**Synopsis**

```
gf_model_set(model M, 'clear')
gf_model_set(model M, 'add fem variable', string name, mesh_fem mf)
gf_model_set(model M, 'add filtered fem variable', string name, mesh_fem mf, int region)
gf_model_set(model M, 'add variable', string name, sizes)
gf_model_set(model M, 'delete variable', string name)
gf_model_set(model M, 'resize variable', string name, sizes)
gf_model_set(model M, 'add multiplier', string name, mesh_fem mf, string primalname[, mesh_im mim, int region])
gf_model_set(model M, 'add im data', string name, mesh_imd mimd)
gf_model_set(model M, 'add fem data', string name, mesh_fem mf[, sizes])
gf_model_set(model M, 'add initialized fem data', string name, mesh_fem mf, vec V[, sizes])
gf_model_set(model M, 'add data', string name, int size)
gf_model_set(model M, 'add macro', string name, string expr)
gf_model_set(model M, 'del macro', string name)
gf_model_set(model M, 'add initialized data', string name, vec V[, sizes])
gf_model_set(model M, 'variable', string name, vec V)
gf_model_set(model M, 'to variables', vec V)
gf_model_set(model M, 'delete brick', int ind_brick)
gf_model_set(model M, 'define variable group', string name[, string varname, ...])
gf_model_set(model M, 'add elementary rotated RT0 projection', string transname)
gf_model_set(model M, 'add interpolate transformation from expression', string transname, mesh source_mesh, mesh target_mesh, string expr)
gf_model_set(model M, 'add element extrapolation transformation', string transname, mesh source_mesh, mat elt_corr)
gf_model_set(model M, 'add standard secondary domain', string name, mesh_im mim, int region = -1)
gf_model_set(model M, 'set element extrapolation correspondance', string transname, mat elt_corr)
gf_model_set(model M, 'add raytracing transformation', string transname, scalar release_distance)
gf_model_set(model M, 'add master contact boundary to raytracing transformation', string transname, mesh m, string dispname, int region)
gf_model_set(model M, 'add slave contact boundary to raytracing transformation', string transname, mesh m, string dispname, int region)
gf_model_set(model M, 'add rigid obstacle to raytracing transformation', string transname, string expr, int N)
gf_model_set(model M, 'add projection transformation', string transname, scalar release_distance)
gf_model_set(model M, 'add master contact boundary to projection transformation', string transname, mesh m, string dispname, int region)
gf_model_set(model M, 'add slave contact boundary to projection transformation', string transname, mesh m, string dispname, int region)
gf_model_set(model M, 'add rigid obstacle to projection transformation', string transname, string expr, int N)
ind = gf_model_set(model M, 'add linear term', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])
ind = gf_model_set(model M, 'add linear twodomain term', mesh_im mim, string expression, int region, string secondary_domain[, int is_symmetric[, int is_coercive]])
ind = gf_model_set(model M, 'add linear generic assembly brick', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])
ind = gf_model_set(model M, 'add nonlinear term', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])
ind = gf_model_set(model M, 'add nonlinear twodomain term', mesh_im mim, string expression, int region, string secondary_domain[, int is_symmetric[, int is_coercive]])
ind = gf_model_set(model M, 'add nonlinear generic assembly brick', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])
ind = gf_model_set(model M, 'add source term', mesh_im mim, string expression[, int region])
ind = gf_model_set(model M, 'add twodomain source term', mesh_im mim, string expression, int region, string secondary_domain)
ind = gf_model_set(model M, 'add source term generic assembly brick', mesh_im mim, string expression[, int region])
gf_model_set(model M, 'add assembly assignment', string dataname, string expression[, int region[, int order[, int before]]])
gf_model_set(model M, 'clear assembly assignment')
ind = gf_model_set(model M, 'add Laplacian brick', mesh_im mim, string varname[, int region])
ind = gf_model_set(model M, 'add generic elliptic brick', mesh_im mim, string varname, string dataname[, int region])
ind = gf_model_set(model M, 'add source term brick', mesh_im mim, string varname, string dataexpr[, int region[, string directdataname]])
ind = gf_model_set(model M, 'add normal source term brick', mesh_im mim, string varname, string dataname, int region)
ind = gf_model_set(model M, 'add Dirichlet condition with simplification', string varname, int region[, string dataname])
ind = gf_model_set(model M, 'add Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region[, string dataname])
ind = gf_model_set(model M, 'add Dirichlet condition with Nitsche method', mesh_im mim, string varname, string Neumannterm, string datagamma0, int region[, scalar theta][, string dataname])
ind = gf_model_set(model M, 'add Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region[, string dataname, mesh_fem mf_mult])
ind = gf_model_set(model M, 'add normal Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region[, string dataname])
ind = gf_model_set(model M, 'add normal Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region[, string dataname, mesh_fem mf_mult])
ind = gf_model_set(model M, 'add normal Dirichlet condition with Nitsche method', mesh_im mim, string varname, string Neumannterm, string gamma0name, int region[, scalar theta][, string dataname])
ind = gf_model_set(model M, 'add generalized Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region, string dataname, string Hname)
ind = gf_model_set(model M, 'add generalized Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region, string dataname, string Hname[, mesh_fem mf_mult])
ind = gf_model_set(model M, 'add generalized Dirichlet condition with Nitsche method', mesh_im mim, string varname, string Neumannterm, string gamma0name, int region[, scalar theta], string dataname, string Hname)
ind = gf_model_set(model M, 'add pointwise constraints with multipliers', string varname, string dataname_pt[, string dataname_unitv] [, string dataname_val])
ind = gf_model_set(model M, 'add pointwise constraints with given multipliers', string varname, string multname, string dataname_pt[, string dataname_unitv] [, string dataname_val])
ind = gf_model_set(model M, 'add pointwise constraints with penalization', string varname, scalar coeff, string dataname_pt[, string dataname_unitv] [, string dataname_val])
gf_model_set(model M, 'change penalization coeff', int ind_brick, scalar coeff)
ind = gf_model_set(model M, 'add Helmholtz brick', mesh_im mim, string varname, string dataexpr[, int region])
ind = gf_model_set(model M, 'add Fourier Robin brick', mesh_im mim, string varname, string dataexpr, int region)
ind = gf_model_set(model M, 'add constraint with multipliers', string varname, string multname, spmat B, {vec L | string dataname})
ind = gf_model_set(model M, 'add constraint with penalization', string varname, scalar coeff, spmat B, {vec L | string dataname})
ind = gf_model_set(model M, 'add explicit matrix', string varname1, string varname2, spmat B[, int issymmetric[, int iscoercive]])
ind = gf_model_set(model M, 'add explicit rhs', string varname, vec L)
gf_model_set(model M, 'set private matrix', int indbrick, spmat B)
gf_model_set(model M, 'set private rhs', int indbrick, vec B)
ind = gf_model_set(model M, 'add isotropic linearized elasticity brick', mesh_im mim, string varname, string dataname_lambda, string dataname_mu[, int region])
ind = gf_model_set(model M, 'add isotropic linearized elasticity brick pstrain', mesh_im mim, string varname, string data_E, string data_nu[, int region])
ind = gf_model_set(model M, 'add isotropic linearized elasticity brick pstress', mesh_im mim, string varname, string data_E, string data_nu[, int region])
ind = gf_model_set(model M, 'add linear incompressibility brick', mesh_im mim, string varname, string multname_pressure[, int region[, string dataexpr_coeff]])
ind = gf_model_set(model M, 'add nonlinear elasticity brick', mesh_im mim, string varname, string constitutive_law, string dataname[, int region])
ind = gf_model_set(model M, 'add finite strain elasticity brick', mesh_im mim, string constitutive_law, string varname, string params[, int region])
ind = gf_model_set(model M, 'add small strain elastoplasticity brick', mesh_im mim, string lawname, string unknowns_type [, string varnames, ...] [, string params, ...] [, string theta = '1' [, string dt = 'timestep']] [, int region = -1])
ind = gf_model_set(model M, 'add elastoplasticity brick', mesh_im mim ,string projname, string varname, string previous_dep_name, string datalambda, string datamu, string datathreshold, string datasigma[, int region])
ind = gf_model_set(model M, 'add finite strain elastoplasticity brick', mesh_im mim , string lawname, string unknowns_type [, string varnames, ...] [, string params, ...] [, int region = -1])
ind = gf_model_set(model M, 'add nonlinear incompressibility brick', mesh_im mim, string varname, string multname_pressure[, int region])
ind = gf_model_set(model M, 'add finite strain incompressibility brick', mesh_im mim, string varname, string multname_pressure[, int region])
ind = gf_model_set(model M, 'add bilaplacian brick', mesh_im mim, string varname, string dataname [, int region])
ind = gf_model_set(model M, 'add Kirchhoff-Love plate brick', mesh_im mim, string varname, string dataname_D, string dataname_nu [, int region])
ind = gf_model_set(model M, 'add normal derivative source term brick', mesh_im mim, string varname, string dataname, int region)
ind = gf_model_set(model M, 'add Kirchhoff-Love Neumann term brick', mesh_im mim, string varname, string dataname_M, string dataname_divM, int region)
ind = gf_model_set(model M, 'add normal derivative Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region [, string dataname, int R_must_be_derivated])
ind = gf_model_set(model M, 'add normal derivative Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region [, string dataname, int R_must_be_derivated])
ind = gf_model_set(model M, 'add Mindlin Reissner plate brick', mesh_im mim, mesh_im mim_reduced, string varname_u3, string varname_theta , string param_E, string param_nu, string param_epsilon, string param_kappa [,int variant [, int region]])
ind = gf_model_set(model M, 'add mass brick', mesh_im mim, string varname[, string dataexpr_rho[, int region]])
gf_model_set(model M, 'shift variables for time integration')
gf_model_set(model M, 'perform init time derivative', scalar ddt)
gf_model_set(model M, 'set time step', scalar dt)
gf_model_set(model M, 'set time', scalar t)
gf_model_set(model M, 'add theta method for first order', string varname, scalar theta)
gf_model_set(model M, 'add theta method for second order', string varname, scalar theta)
gf_model_set(model M, 'add Newmark scheme', string varname, scalar beta, scalar gamma)
gf_model_set(model M, 'disable bricks', ivec bricks_indices)
gf_model_set(model M, 'enable bricks', ivec bricks_indices)
gf_model_set(model M, 'disable variable', string varname)
gf_model_set(model M, 'enable variable', string varname)
gf_model_set(model M, 'first iter')
gf_model_set(model M, 'next iter')
ind = gf_model_set(model M, 'add basic contact brick', string varname_u, string multname_n[, string multname_t], string dataname_r, spmat BN[, spmat BT, string dataname_friction_coeff][, string dataname_gap[, string dataname_alpha[, int augmented_version[, string dataname_gamma, string dataname_wt]]])
ind = gf_model_set(model M, 'add basic contact brick two deformable bodies', string varname_u1, string varname_u2, string multname_n, string dataname_r, spmat BN1, spmat BN2[, string dataname_gap[, string dataname_alpha[, int augmented_version]]])
gf_model_set(model M, 'contact brick set BN', int indbrick, spmat BN)
gf_model_set(model M, 'contact brick set BT', int indbrick, spmat BT)
ind = gf_model_set(model M, 'add nodal contact with rigid obstacle brick', mesh_im mim, string varname_u, string multname_n[, string multname_t], string dataname_r[, string dataname_friction_coeff], int region, string obstacle[, int augmented_version])
ind = gf_model_set(model M, 'add contact with rigid obstacle brick', mesh_im mim, string varname_u, string multname_n[, string multname_t], string dataname_r[, string dataname_friction_coeff], int region, string obstacle[, int augmented_version])
ind = gf_model_set(model M, 'add integral contact with rigid obstacle brick', mesh_im mim, string varname_u, string multname, string dataname_obstacle, string dataname_r [, string dataname_friction_coeff], int region [, int option [, string dataname_alpha [, string dataname_wt [, string dataname_gamma [, string dataname_vt]]]]])
ind = gf_model_set(model M, 'add penalized contact with rigid obstacle brick', mesh_im mim, string varname_u, string dataname_obstacle, string dataname_r [, string dataname_coeff], int region [, int option, string dataname_lambda, [, string dataname_alpha [, string dataname_wt]]])
ind = gf_model_set(model M, 'add Nitsche contact with rigid obstacle brick', mesh_im mim, string varname, string Neumannterm, string dataname_obstacle, string gamma0name, int region[, scalar theta[, string dataname_friction_coeff[, string dataname_alpha, string dataname_wt]]])
ind = gf_model_set(model M, 'add Nitsche midpoint contact with rigid obstacle brick', mesh_im mim, string varname, string Neumannterm, string Neumannterm_wt, string dataname_obstacle, string gamma0name, int region, scalar theta, string dataname_friction_coeff, string dataname_alpha, string dataname_wt)
ind = gf_model_set(model M, 'add Nitsche fictitious domain contact brick', mesh_im mim, string varname1, string varname2, string dataname_d1, string dataname_d2, string gamma0name [, scalar theta[, string dataname_friction_coeff[, string dataname_alpha, string dataname_wt1,string dataname_wt2]]])
ind = gf_model_set(model M, 'add nodal contact between nonmatching meshes brick', mesh_im mim1[, mesh_im mim2], string varname_u1[, string varname_u2], string multname_n[, string multname_t], string dataname_r[, string dataname_fr], int rg1, int rg2[, int slave1, int slave2, int augmented_version])
ind = gf_model_set(model M, 'add nonmatching meshes contact brick', mesh_im mim1[, mesh_im mim2], string varname_u1[, string varname_u2], string multname_n[, string multname_t], string dataname_r[, string dataname_fr], int rg1, int rg2[, int slave1, int slave2, int augmented_version])
ind = gf_model_set(model M, 'add integral contact between nonmatching meshes brick', mesh_im mim, string varname_u1, string varname_u2, string multname, string dataname_r [, string dataname_friction_coeff], int region1, int region2 [, int option [, string dataname_alpha [, string dataname_wt1 , string dataname_wt2]]])
ind = gf_model_set(model M, 'add penalized contact between nonmatching meshes brick', mesh_im mim, string varname_u1, string varname_u2, string dataname_r [, string dataname_coeff], int region1, int region2 [, int option [, string dataname_lambda, [, string dataname_alpha [, string dataname_wt1, string dataname_wt2]]]])
ind = gf_model_set(model M, 'add integral large sliding contact brick raytracing', string dataname_r, scalar release_distance, [, string dataname_fr[, string dataname_alpha[, int version]]])
gf_model_set(model M, 'add rigid obstacle to large sliding contact brick', int indbrick, string expr, int N)
gf_model_set(model M, 'add master contact boundary to large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname[, string wname])
gf_model_set(model M, 'add slave contact boundary to large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])
gf_model_set(model M, 'add master slave contact boundary to large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])
ind = gf_model_set(model M, 'add Nitsche large sliding contact brick raytracing', bool unbiased_version, string dataname_r, scalar release_distance[, string dataname_fr[, string dataname_alpha[, int version]]])
gf_model_set(model M, 'add rigid obstacle to Nitsche large sliding contact brick', int indbrick, string expr, int N)
gf_model_set(model M, 'add master contact boundary to biased Nitsche large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname[, string wname])
gf_model_set(model M, 'add slave contact boundary to biased Nitsche large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])
gf_model_set(model M, 'add contact boundary to unbiased Nitsche large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])
```

**Description :**

Modifies a model object.

**Command list :**

gf_model_set(model M, 'clear')Clear the model.

gf_model_set(model M, 'add fem variable', string name, mesh_fem mf)Add a variable to the model linked to a mesh_fem. <literal>name</literal> is the variable name.

gf_model_set(model M, 'add filtered fem variable', string name, mesh_fem mf, int region)Add a variable to the model linked to a mesh_fem. The variable is filtered in the sense that only the dof on the region are considered. <literal>name</literal> is the variable name.

gf_model_set(model M, 'add variable', string name, sizes)Add a variable to the model of constant sizes. <literal>sizes</literal> is either a integer (for a scalar or vector variable) or a vector of dimensions for a tensor variable. <literal>name</literal> is the variable name.

gf_model_set(model M, 'delete variable', string name)Delete a variable or a data from the model.

gf_model_set(model M, 'resize variable', string name, sizes)Resize a constant size variable of the model. <literal>sizes</literal> is either a integer (for a scalar or vector variable) or a vector of dimensions for a tensor variable. <literal>name</literal> is the variable name.

gf_model_set(model M, 'add multiplier', string name, mesh_fem mf, string primalname[, mesh_im mim, int region])Add a particular variable linked to a fem being a multiplier with respect to a primal variable. The dof will be filtered with the <literal></literal>gmm::range_basis<literal></literal> function applied on the terms of the model which link the multiplier and the primal variable. This in order to retain only linearly independent constraints on the primal variable. Optimized for boundary multipliers.

gf_model_set(model M, 'add im data', string name, mesh_imd mimd)Add a data set to the model linked to a mesh_imd. <literal>name</literal> is the data name.

gf_model_set(model M, 'add fem data', string name, mesh_fem mf[, sizes])Add a data to the model linked to a mesh_fem. <literal>name</literal> is the data name, <literal>sizes</literal> an optional parameter which is either an integer or a vector of suplementary dimensions with respect to <literal>mf</literal>.

gf_model_set(model M, 'add initialized fem data', string name, mesh_fem mf, vec V[, sizes])Add a data to the model linked to a mesh_fem. <literal>name</literal> is the data name. The data is initiakized with <literal>V</literal>. The data can be a scalar or vector field. <literal>sizes</literal> an optional parameter which is either an integer or a vector of suplementary dimensions with respect to <literal>mf</literal>.

gf_model_set(model M, 'add data', string name, int size)Add a fixed size data to the model. <literal>sizes</literal> is either a integer (for a scalar or vector data) or a vector of dimensions for a tensor data. <literal>name</literal> is the data name.

gf_model_set(model M, 'add macro', string name, string expr)Define a new macro for the high generic assembly language. The name include the parameters. For instance name=’sp(a,b)’, expr=’a.b’ is a valid definition. Macro without parameter can also be defined. For instance name=’x1’, expr=’X[1]’ is valid. Teh form name=’grad(u)’, expr=’Grad_u’ is also allowed but in that case, the parameter ‘u’ will only be allowed to be a variable name when using the macro. Note that macros can be directly defined inside the assembly strings with the keyword ‘Def’.

gf_model_set(model M, 'del macro', string name)Delete a previously defined macro for the high generic assembly language.

gf_model_set(model M, 'add initialized data', string name, vec V[, sizes])Add an initialized fixed size data to the model. <literal>sizes</literal> an optional parameter which is either an integer or a vector dimensions that describes the format of the data. By default, the data is considered to b a vector field. <literal>name</literal> is the data name and <literal>V</literal> is the value of the data.

gf_model_set(model M, 'variable', string name, vec V)Set the value of a variable or data. <literal>name</literal> is the data name.

gf_model_set(model M, 'to variables', vec V)Set the value of the variables of the model with the vector <literal>V</literal>. Typically, the vector <literal>V</literal> results of the solve of the tangent linear system (useful to solve your problem with you own solver).

gf_model_set(model M, 'delete brick', int ind_brick)Delete a variable or a data from the model.

gf_model_set(model M, 'define variable group', string name[, string varname, ...])Defines a group of variables for the interpolation (mainly for the raytracing interpolation transformation.

gf_model_set(model M, 'add elementary rotated RT0 projection', string transname)Experimental method ...

gf_model_set(model M, 'add interpolate transformation from expression', string transname, mesh source_mesh, mesh target_mesh, string expr)Add a transformation to the model from mesh <literal>source_mesh</literal> to mesh <literal>target_mesh</literal> given by the expression <literal>expr</literal> which corresponds to a high-level generic assembly expression which may contains some variable of the model. CAUTION: the derivative of the transformation with used variable is taken into account in the computation of the tangen system. However, order two derivative is not implemented, so such tranformation is not allowed in the definition of a potential.

gf_model_set(model M, 'add element extrapolation transformation', string transname, mesh source_mesh, mat elt_corr)Add a special interpolation transformation which represents the identity transformation but allows to evaluate the expression on another element than the current element by polynomial extrapolation. It is used for stabilization term in fictitious domain applications. the array elt_cor should be a two entry array whose first line contains the elements concerned by the transformation and the second line the respective elements on which the extrapolation has to be made. If an element is not listed in elt_cor the evaluation is just made on the current element.

gf_model_set(model M, 'add standard secondary domain', string name, mesh_im mim, int region = -1)Add a secondary domain to the model which can be used in a weak-form language expression for integration on the product of two domains. <literal>name</literal> is the name of the secondary domain, <literal>mim</literal> is an integration method on this domain and <literal>region</literal> the region on which the integration is to be performed.

gf_model_set(model M, 'set element extrapolation correspondance', string transname, mat elt_corr)Change the correspondance map of an element extrapolation interpolate transformation.

gf_model_set(model M, 'add raytracing transformation', string transname, scalar release_distance)Add a raytracing interpolate transformation called <literal>transname</literal> to a model to be used by the generic assembly bricks. CAUTION: For the moment, the derivative of the transformation is not taken into account in the model solve.

gf_model_set(model M, 'add master contact boundary to raytracing transformation', string transname, mesh m, string dispname, int region)Add a master contact boundary with corresponding displacement variable <literal>dispname</literal> on a specific boundary <literal>region</literal> to an existing raytracing interpolate transformation called <literal>transname</literal>.

gf_model_set(model M, 'add slave contact boundary to raytracing transformation', string transname, mesh m, string dispname, int region)Add a slave contact boundary with corresponding displacement variable <literal>dispname</literal> on a specific boundary <literal>region</literal> to an existing raytracing interpolate transformation called <literal>transname</literal>.

gf_model_set(model M, 'add rigid obstacle to raytracing transformation', string transname, string expr, int N)Add a rigid obstacle whose geometry corresponds to the zero level-set of the high-level generic assembly expression <literal>expr</literal> to an existing raytracing interpolate transformation called <literal>transname</literal>.

gf_model_set(model M, 'add projection transformation', string transname, scalar release_distance)Add a projection interpolate transformation called <literal>transname</literal> to a model to be used by the generic assembly bricks. CAUTION: For the moment, the derivative of the transformation is not taken into account in the model solve.

gf_model_set(model M, 'add master contact boundary to projection transformation', string transname, mesh m, string dispname, int region)Add a master contact boundary with corresponding displacement variable <literal>dispname</literal> on a specific boundary <literal>region</literal> to an existing projection interpolate transformation called <literal>transname</literal>.

gf_model_set(model M, 'add slave contact boundary to projection transformation', string transname, mesh m, string dispname, int region)Add a slave contact boundary with corresponding displacement variable <literal>dispname</literal> on a specific boundary <literal>region</literal> to an existing projection interpolate transformation called <literal>transname</literal>.

gf_model_set(model M, 'add rigid obstacle to projection transformation', string transname, string expr, int N)Add a rigid obstacle whose geometry corresponds to the zero level-set of the high-level generic assembly expression <literal>expr</literal> to an existing projection interpolate transformation called <literal>transname</literal>.

ind = gf_model_set(model M, 'add linear term', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])Adds a matrix term given by the assembly string <literal>expr</literal> which will be assembled in region <literal>region</literal> and with the integration method <literal>mim</literal>. Only the matrix term will be taken into account, assuming that it is linear. The advantage of declaring a term linear instead of nonlinear is that it will be assembled only once and no assembly is necessary for the residual. Take care that if the expression contains some variables and if the expression is a potential or of first order (i.e. describe the weak form, not the derivative of the weak form), the expression will be derivated with respect to all variables. You can specify if the term is symmetric, coercive or not. If you are not sure, the better is to declare the term not symmetric and not coercive. But some solvers (conjugate gradient for instance) are not allowed for non-coercive problems. <literal>brickname</literal> is an otpional name for the brick.

ind = gf_model_set(model M, 'add linear twodomain term', mesh_im mim, string expression, int region, string secondary_domain[, int is_symmetric[, int is_coercive]])Adds a linear term given by a weak form language expression like gf_model_set(model M, ‘add linear term’) but for an integration on a direct product of two domains, a first specfied by <literal></literal>mim<literal></literal> and <literal></literal>region<literal></literal> and a second one by <literal></literal>secondary_domain<literal></literal> which has to be declared first into the model.

ind = gf_model_set(model M, 'add linear generic assembly brick', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])Deprecated. Use gf_model_set(model M, ‘add linear term’) instead.

ind = gf_model_set(model M, 'add nonlinear term', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])Adds a nonlinear term given by the assembly string <literal>expr</literal> which will be assembled in region <literal>region</literal> and with the integration method <literal>mim</literal>. The expression can describe a potential or a weak form. Second order terms (i.e. containing second order test functions, Test2) are not allowed. You can specify if the term is symmetric, coercive or not. If you are not sure, the better is to declare the term not symmetric and not coercive. But some solvers (conjugate gradient for instance) are not allowed for non-coercive problems. <literal>brickname</literal> is an otpional name for the brick.

ind = gf_model_set(model M, 'add nonlinear twodomain term', mesh_im mim, string expression, int region, string secondary_domain[, int is_symmetric[, int is_coercive]])Adds a nonlinear term given by a weak form language expression like gf_model_set(model M, ‘add nonlinear term’) but for an integration on a direct product of two domains, a first specfied by <literal></literal>mim<literal></literal> and <literal></literal>region<literal></literal> and a second one by <literal></literal>secondary_domain<literal></literal> which has to be declared first into the model.

ind = gf_model_set(model M, 'add nonlinear generic assembly brick', mesh_im mim, string expression[, int region[, int is_symmetric[, int is_coercive]]])Deprecated. Use gf_model_set(model M, ‘add nonlinear term’) instead.

ind = gf_model_set(model M, 'add source term', mesh_im mim, string expression[, int region])Adds a source term given by the assembly string <literal>expr</literal> which will be assembled in region <literal>region</literal> and with the integration method <literal>mim</literal>. Only the residual term will be taken into account. Take care that if the expression contains some variables and if the expression is a potential, the expression will be derivated with respect to all variables. <literal>brickname</literal> is an optional name for the brick.

ind = gf_model_set(model M, 'add twodomain source term', mesh_im mim, string expression, int region, string secondary_domain)Adds a source term given by a weak form language expression like gf_model_set(model M, ‘add source term’) but for an integration on a direct product of two domains, a first specfied by <literal></literal>mim<literal></literal> and <literal></literal>region<literal></literal> and a second one by <literal></literal>secondary_domain<literal></literal> which has to be declared first into the model.

ind = gf_model_set(model M, 'add source term generic assembly brick', mesh_im mim, string expression[, int region])Deprecated. Use gf_model_set(model M, ‘add source term’) instead.

gf_model_set(model M, 'add assembly assignment', string dataname, string expression[, int region[, int order[, int before]]])Adds expression <literal>expr</literal> to be evaluated at assembly time and being assigned to the data <literal>dataname</literal> which has to be of im_data type. This allows for instance to store a sub-expression of an assembly computation to be used on an other assembly. It can be used for instance to store the plastic strain in plasticity models. <literal>order</literal> represents the order of assembly where this assignement has to be done (potential(0), weak form(1) or tangent system(2) or at each order(-1)). The default value is 1. If before = 1, the the assignement is perfromed before the computation of the other assembly terms, such that the data can be used in the remaining of the assembly as an intermediary result (be careful that it is still considered as a data, no derivation of the expression is performed for the tangent system). If before = 0 (default), the assignement is done after the assembly terms.

gf_model_set(model M, 'clear assembly assignment')Delete all added assembly assignments

ind = gf_model_set(model M, 'add Laplacian brick', mesh_im mim, string varname[, int region])Add a Laplacian term to the model relatively to the variable <literal>varname</literal> (in fact with a minus : <latex style=”text”><![CDATA[-text{div}(nabla u)]]></latex>). If this is a vector valued variable, the Laplacian term is added componentwise. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model.

ind = gf_model_set(model M, 'add generic elliptic brick', mesh_im mim, string varname, string dataname[, int region])Add a generic elliptic term to the model relatively to the variable <literal>varname</literal>. The shape of the elliptic term depends both on the variable and the data. This corresponds to a term <latex style=”text”><![CDATA[-text{div}(anabla u)]]></latex> where <latex style=”text”><![CDATA[a]]></latex> is the data and <latex style=”text”><![CDATA[u]]></latex> the variable. The data can be a scalar, a matrix or an order four tensor. The variable can be vector valued or not. If the data is a scalar or a matrix and the variable is vector valued then the term is added componentwise. An order four tensor data is allowed for vector valued variable only. The data can be constant or describbed on a fem. Of course, when the data is a tensor describe on a finite element method (a tensor field) the data can be a huge vector. The components of the matrix/tensor have to be stored with the fortran order (columnwise) in the data vector (compatibility with blas). The symmetry of the given matrix/tensor is not verified (but assumed). If this is a vector valued variable, the elliptic term is added componentwise. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Note that for the real version which uses the high-level generic assembly language, <literal>dataname</literal> can be any regular expression of the high-level generic assembly language (like “1”, “sin(X(1))” or “Norm(u)” for instance) even depending on model variables. Return the brick index in the model.

ind = gf_model_set(model M, 'add source term brick', mesh_im mim, string varname, string dataexpr[, int region[, string directdataname]])Add a source term to the model relatively to the variable <literal>varname</literal>. The source term is represented by <literal>dataexpr</literal> which could be any regular expression of the high-level generic assembly language (except for the complex version where it has to be a declared data of the model). <literal>region</literal> is an optional mesh region on which the term is added. An additional optional data <literal>directdataname</literal> can be provided. The corresponding data vector will be directly added to the right hand side without assembly. Note that when region is a boundary, this brick allows to prescribe a nonzero Neumann boundary condition. Return the brick index in the model.

ind = gf_model_set(model M, 'add normal source term brick', mesh_im mim, string varname, string dataname, int region)Add a source term on the variable <literal>varname</literal> on a boundary <literal>region</literal>. This region should be a boundary. The source term is represented by the data <literal>dataepxpr</literal> which could be any regular expression of the high-level generic assembly language (except for the complex version where it has to be a declared data of the model). A scalar product with the outward normal unit vector to the boundary is performed. The main aim of this brick is to represent a Neumann condition with a vector data without performing the scalar product with the normal as a pre-processing. Return the brick index in the model.

ind = gf_model_set(model M, 'add Dirichlet condition with simplification', string varname, int region[, string dataname])Adds a (simple) Dirichlet condition on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. The Dirichlet condition is prescribed by a simple post-treatment of the final linear system (tangent system for nonlinear problems) consisting of modifying the lines corresponding to the degree of freedom of the variable on <literal>region</literal> (0 outside the diagonal, 1 on the diagonal of the matrix and the expected value on the right hand side). The symmetry of the linear system is kept if all other bricks are symmetric. This brick is to be reserved for simple Dirichlet conditions (only dof declared on the correspodning boundary are prescribed). The application of this brick on reduced dof may be problematic. Intrinsic vectorial finite element method are not supported. <literal>dataname</literal> is the optional right hand side of the Dirichlet condition. It could be constant (but in that case, it can only be applied to Lagrange f.e.m.) or (important) described on the same finite element method as <literal>varname</literal>. Returns the brick index in the model.

ind = gf_model_set(model M, 'add Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region[, string dataname])Add a Dirichlet condition on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. This region should be a boundary. The Dirichlet condition is prescribed with a multiplier variable described by <literal>mult_description</literal>. If <literal>mult_description</literal> is a string this is assumed to be the variable name corresponding to the multiplier (which should be first declared as a multiplier variable on the mesh region in the model). If it is a finite element method (mesh_fem object) then a multiplier variable will be added to the model and build on this finite element method (it will be restricted to the mesh region <literal>region</literal> and eventually some conflicting dofs with some other multiplier variables will be suppressed). If it is an integer, then a multiplier variable will be added to the model and build on a classical finite element of degree that integer. <literal>dataname</literal> is the optional right hand side of the Dirichlet condition. It could be constant or described on a fem; scalar or vector valued, depending on the variable on which the Dirichlet condition is prescribed. Return the brick index in the model.

ind = gf_model_set(model M, 'add Dirichlet condition with Nitsche method', mesh_im mim, string varname, string Neumannterm, string datagamma0, int region[, scalar theta][, string dataname])Add a Dirichlet condition on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. This region should be a boundary. <literal>Neumannterm</literal> is the expression of the Neumann term (obtained by the Green formula) described as an expression of the high-level generic assembly language. This term can be obtained by gf_model_get(model M, ‘Neumann term’, varname, region) once all volumic bricks have been added to the model. The Dirichlet condition is prescribed with Nitsche’s method. <literal>datag</literal> is the optional right hand side of the Dirichlet condition. <literal>datagamma0</literal> is the Nitsche’s method parameter. <literal>theta</literal> is a scalar value which can be positive or negative. <literal>theta = 1</literal> corresponds to the standard symmetric method which is conditionnaly coercive for <literal>gamma0</literal> small. <literal>theta = -1</literal> corresponds to the skew-symmetric method which is inconditionnaly coercive. <literal>theta = 0</literal> (default) is the simplest method for which the second derivative of the Neumann term is not necessary even for nonlinear problems. Return the brick index in the model.

ind = gf_model_set(model M, 'add Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region[, string dataname, mesh_fem mf_mult])Add a Dirichlet condition on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. This region should be a boundary. The Dirichlet condition is prescribed with penalization. The penalization coefficient is initially <literal>coeff</literal> and will be added to the data of the model. <literal>dataname</literal> is the optional right hand side of the Dirichlet condition. It could be constant or described on a fem; scalar or vector valued, depending on the variable on which the Dirichlet condition is prescribed. <literal>mf_mult</literal> is an optional parameter which allows to weaken the Dirichlet condition specifying a multiplier space. Return the brick index in the model.

ind = gf_model_set(model M, 'add normal Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region[, string dataname])Add a Dirichlet condition to the normal component of the vector (or tensor) valued variable <literal>varname</literal> and the mesh region <literal>region</literal>. This region should be a boundary. The Dirichlet condition is prescribed with a multiplier variable described by <literal>mult_description</literal>. If <literal>mult_description</literal> is a string this is assumed to be the variable name corresponding to the multiplier (which should be first declared as a multiplier variable on the mesh region in the model). If it is a finite element method (mesh_fem object) then a multiplier variable will be added to the model and build on this finite element method (it will be restricted to the mesh region <literal>region</literal> and eventually some conflicting dofs with some other multiplier variables will be suppressed). If it is an integer, then a multiplier variable will be added to the model and build on a classical finite element of degree that integer. <literal>dataname</literal> is the optional right hand side of the Dirichlet condition. It could be constant or described on a fem; scalar or vector valued, depending on the variable on which the Dirichlet condition is prescribed (scalar if the variable is vector valued, vector if the variable is tensor valued). Returns the brick index in the model.

ind = gf_model_set(model M, 'add normal Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region[, string dataname, mesh_fem mf_mult])Add a Dirichlet condition to the normal component of the vector (or tensor) valued variable <literal>varname</literal> and the mesh region <literal>region</literal>. This region should be a boundary. The Dirichlet condition is prescribed with penalization. The penalization coefficient is initially <literal>coeff</literal> and will be added to the data of the model. <literal>dataname</literal> is the optional right hand side of the Dirichlet condition. It could be constant or described on a fem; scalar or vector valued, depending on the variable on which the Dirichlet condition is prescribed (scalar if the variable is vector valued, vector if the variable is tensor valued). <literal>mf_mult</literal> is an optional parameter which allows to weaken the Dirichlet condition specifying a multiplier space. Returns the brick index in the model.

ind = gf_model_set(model M, 'add normal Dirichlet condition with Nitsche method', mesh_im mim, string varname, string Neumannterm, string gamma0name, int region[, scalar theta][, string dataname])Add a Dirichlet condition to the normal component of the vector (or tensor) valued variable <literal>varname</literal> and the mesh region <literal>region</literal>. This region should be a boundary. <literal>Neumannterm</literal> is the expression of the Neumann term (obtained by the Green formula) described as an expression of the high-level generic assembly language. This term can be obtained by gf_model_get(model M, ‘Neumann term’, varname, region) once all volumic bricks have been added to the model. The Dirichlet condition is prescribed with Nitsche’s method. <literal>dataname</literal> is the optional right hand side of the Dirichlet condition. It could be constant or described on a fem. <literal>gamma0name</literal> is the Nitsche’s method parameter. <literal>theta</literal> is a scalar value which can be positive or negative. <literal>theta = 1</literal> corresponds to the standard symmetric method which is conditionnaly coercive for <literal>gamma0</literal> small. <literal>theta = -1</literal> corresponds to the skew-symmetric method which is inconditionnaly coercive. <literal>theta = 0</literal> is the simplest method for which the second derivative of the Neumann term is not necessary even for nonlinear problems. Returns the brick index in the model. (This brick is not fully tested)

ind = gf_model_set(model M, 'add generalized Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region, string dataname, string Hname)Add a Dirichlet condition on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. This version is for vector field. It prescribes a condition <latex style=”text”><![CDATA[Hu = r]]></latex> where <literal>H</literal> is a matrix field. The region should be a boundary. The Dirichlet condition is prescribed with a multiplier variable described by <literal>mult_description</literal>. If <literal>mult_description</literal> is a string this is assumed to be the variable name corresponding to the multiplier (which should be first declared as a multiplier variable on the mesh region in the model). If it is a finite element method (mesh_fem object) then a multiplier variable will be added to the model and build on this finite element method (it will be restricted to the mesh region <literal>region</literal> and eventually some conflicting dofs with some other multiplier variables will be suppressed). If it is an integer, then a multiplier variable will be added to the model and build on a classical finite element of degree that integer. <literal>dataname</literal> is the right hand side of the Dirichlet condition. It could be constant or described on a fem; scalar or vector valued, depending on the variable on which the Dirichlet condition is prescribed. <literal>Hname</literal> is the data corresponding to the matrix field <literal>H</literal>. Returns the brick index in the model.

ind = gf_model_set(model M, 'add generalized Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region, string dataname, string Hname[, mesh_fem mf_mult])Add a Dirichlet condition on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. This version is for vector field. It prescribes a condition <latex style=”text”><![CDATA[Hu = r]]></latex> where <literal>H</literal> is a matrix field. The region should be a boundary. The Dirichlet condition is prescribed with penalization. The penalization coefficient is intially <literal>coeff</literal> and will be added to the data of the model. <literal>dataname</literal> is the right hand side of the Dirichlet condition. It could be constant or described on a fem; scalar or vector valued, depending on the variable on which the Dirichlet condition is prescribed. <literal>Hname</literal> is the data corresponding to the matrix field <literal>H</literal>. It has to be a constant matrix or described on a scalar fem. <literal>mf_mult</literal> is an optional parameter which allows to weaken the Dirichlet condition specifying a multiplier space. Return the brick index in the model.

ind = gf_model_set(model M, 'add generalized Dirichlet condition with Nitsche method', mesh_im mim, string varname, string Neumannterm, string gamma0name, int region[, scalar theta], string dataname, string Hname)Add a Dirichlet condition on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. This version is for vector field. It prescribes a condition @f$ Hu = r @f$ where <literal>H</literal> is a matrix field. CAUTION : the matrix H should have all eigenvalues equal to 1 or 0. The region should be a boundary. <literal>Neumannterm</literal> is the expression of the Neumann term (obtained by the Green formula) described as an expression of the high-level generic assembly language. This term can be obtained by gf_model_get(model M, ‘Neumann term’, varname, region) once all volumic bricks have been added to the model. The Dirichlet condition is prescribed with Nitsche’s method. <literal>dataname</literal> is the optional right hand side of the Dirichlet condition. It could be constant or described on a fem. <literal>gamma0name</literal> is the Nitsche’s method parameter. <literal>theta</literal> is a scalar value which can be positive or negative. <literal>theta = 1</literal> corresponds to the standard symmetric method which is conditionnaly coercive for <literal>gamma0</literal> small. <literal>theta = -1</literal> corresponds to the skew-symmetric method which is inconditionnaly coercive. <literal>theta = 0</literal> is the simplest method for which the second derivative of the Neumann term is not necessary even for nonlinear problems. <literal>Hname</literal> is the data corresponding to the matrix field <literal>H</literal>. It has to be a constant matrix or described on a scalar fem. Returns the brick index in the model. (This brick is not fully tested)

ind = gf_model_set(model M, 'add pointwise constraints with multipliers', string varname, string dataname_pt[, string dataname_unitv] [, string dataname_val])Add some pointwise constraints on the variable <literal>varname</literal> using multiplier. The multiplier variable is automatically added to the model. The conditions are prescribed on a set of points given in the data <literal>dataname_pt</literal> whose dimension is the number of points times the dimension of the mesh. If the variable represents a vector field, one has to give the data <literal>dataname_unitv</literal> which represents a vector of dimension the number of points times the dimension of the vector field which should store some unit vectors. In that case the prescribed constraint is the scalar product of the variable at the corresponding point with the corresponding unit vector. The optional data <literal>dataname_val</literal> is the vector of values to be prescribed at the different points. This brick is specifically designed to kill rigid displacement in a Neumann problem. Returns the brick index in the model.

ind = gf_model_set(model M, 'add pointwise constraints with given multipliers', string varname, string multname, string dataname_pt[, string dataname_unitv] [, string dataname_val])Add some pointwise constraints on the variable <literal>varname</literal> using a given multiplier <literal>multname</literal>. The conditions are prescribed on a set of points given in the data <literal>dataname_pt</literal> whose dimension is the number of points times the dimension of the mesh. The multiplier variable should be a fixed size variable of size the number of points. If the variable represents a vector field, one has to give the data <literal>dataname_unitv</literal> which represents a vector of dimension the number of points times the dimension of the vector field which should store some unit vectors. In that case the prescribed constraint is the scalar product of the variable at the corresponding point with the corresponding unit vector. The optional data <literal>dataname_val</literal> is the vector of values to be prescribed at the different points. This brick is specifically designed to kill rigid displacement in a Neumann problem. Returns the brick index in the model.

ind = gf_model_set(model M, 'add pointwise constraints with penalization', string varname, scalar coeff, string dataname_pt[, string dataname_unitv] [, string dataname_val])Add some pointwise constraints on the variable <literal>varname</literal> thanks to a penalization. The penalization coefficient is initially <literal>penalization_coeff</literal> and will be added to the data of the model. The conditions are prescribed on a set of points given in the data <literal>dataname_pt</literal> whose dimension is the number of points times the dimension of the mesh. If the variable represents a vector field, one has to give the data <literal>dataname_unitv</literal> which represents a vector of dimension the number of points times the dimension of the vector field which should store some unit vectors. In that case the prescribed constraint is the scalar product of the variable at the corresponding point with the corresponding unit vector. The optional data <literal>dataname_val</literal> is the vector of values to be prescribed at the different points. This brick is specifically designed to kill rigid displacement in a Neumann problem. Returns the brick index in the model.

gf_model_set(model M, 'change penalization coeff', int ind_brick, scalar coeff)Change the penalization coefficient of a Dirichlet condition with penalization brick. If the brick is not of this kind, this function has an undefined behavior.

ind = gf_model_set(model M, 'add Helmholtz brick', mesh_im mim, string varname, string dataexpr[, int region])Add a Helmholtz term to the model relatively to the variable <literal>varname</literal>. <literal>dataexpr</literal> is the wave number. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model.

ind = gf_model_set(model M, 'add Fourier Robin brick', mesh_im mim, string varname, string dataexpr, int region)Add a Fourier-Robin term to the model relatively to the variable <literal>varname</literal>. This corresponds to a weak term of the form <latex style=”text”><![CDATA[int (qu).v]]></latex>. <literal>dataexpr</literal> is the parameter <latex style=”text”><![CDATA[q]]></latex> of the Fourier-Robin condition. It can be an arbitrary valid expression of the high-level generic assembly language (except for the complex version for which it should be a data of the model). <literal>region</literal> is the mesh region on which the term is added. Return the brick index in the model.

ind = gf_model_set(model M, 'add constraint with multipliers', string varname, string multname, spmat B, {vec L | string dataname})Add an additional explicit constraint on the variable <literal>varname</literal> thank to a multiplier <literal>multname</literal> peviously added to the model (should be a fixed size variable). The constraint is <latex style=”text”><![CDATA[BU=L]]></latex> with <literal>B</literal> being a rectangular sparse matrix. It is possible to change the constraint at any time with the methods gf_model_set(model M, ‘set private matrix’) and gf_model_set(model M, ‘set private rhs’). If <literal>dataname</literal> is specified instead of <literal>L</literal>, the vector <literal>L</literal> is defined in the model as data with the given name. Return the brick index in the model.

ind = gf_model_set(model M, 'add constraint with penalization', string varname, scalar coeff, spmat B, {vec L | string dataname})Add an additional explicit penalized constraint on the variable <literal>varname</literal>. The constraint is :math<literal>BU=L</literal> with <literal>B</literal> being a rectangular sparse matrix. Be aware that <literal>B</literal> should not contain a palin row, otherwise the whole tangent matrix will be plain. It is possible to change the constraint at any time with the methods gf_model_set(model M, ‘set private matrix’) and gf_model_set(model M, ‘set private rhs’). The method gf_model_set(model M, ‘change penalization coeff’) can be used. If <literal>dataname</literal> is specified instead of <literal>L</literal>, the vector <literal>L</literal> is defined in the model as data with the given name. Return the brick index in the model.

ind = gf_model_set(model M, 'add explicit matrix', string varname1, string varname2, spmat B[, int issymmetric[, int iscoercive]])Add a brick representing an explicit matrix to be added to the tangent linear system relatively to the variables <literal>varname1</literal> and <literal>varname2</literal>. The given matrix should have has many rows as the dimension of <literal>varname1</literal> and as many columns as the dimension of <literal>varname2</literal>. If the two variables are different and if <literal>issymmetric</literal> is set to 1 then the transpose of the matrix is also added to the tangent system (default is 0). Set <literal>iscoercive</literal> to 1 if the term does not affect the coercivity of the tangent system (default is 0). The matrix can be changed by the command gf_model_set(model M, ‘set private matrix’). Return the brick index in the model.

ind = gf_model_set(model M, 'add explicit rhs', string varname, vec L)Add a brick representing an explicit right hand side to be added to the right hand side of the tangent linear system relatively to the variable <literal>varname</literal>. The given rhs should have the same size than the dimension of <literal>varname</literal>. The rhs can be changed by the command gf_model_set(model M, ‘set private rhs’). If <literal>dataname</literal> is specified instead of <literal>L</literal>, the vector <literal>L</literal> is defined in the model as data with the given name. Return the brick index in the model.

gf_model_set(model M, 'set private matrix', int indbrick, spmat B)For some specific bricks having an internal sparse matrix (explicit bricks: ‘constraint brick’ and ‘explicit matrix brick’), set this matrix.

gf_model_set(model M, 'set private rhs', int indbrick, vec B)For some specific bricks having an internal right hand side vector (explicit bricks: ‘constraint brick’ and ‘explicit rhs brick’), set this rhs.

ind = gf_model_set(model M, 'add isotropic linearized elasticity brick', mesh_im mim, string varname, string dataname_lambda, string dataname_mu[, int region])Add an isotropic linearized elasticity term to the model relatively to the variable <literal>varname</literal>. <literal>dataname_lambda</literal> and <literal>dataname_mu</literal> should contain the Lame coefficients. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model.

ind = gf_model_set(model M, 'add isotropic linearized elasticity brick pstrain', mesh_im mim, string varname, string data_E, string data_nu[, int region])Add an isotropic linearized elasticity term to the model relatively to the variable <literal>varname</literal>. <literal>data_E</literal> and <literal>data_nu</literal> should contain the Young modulus and Poisson ratio, respectively. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. On two-dimensional meshes, the term will correpsond to a plain strain approximation. On three-dimensional meshes, it will correspond to the standard model. Return the brick index in the model.

ind = gf_model_set(model M, 'add isotropic linearized elasticity brick pstress', mesh_im mim, string varname, string data_E, string data_nu[, int region])Add an isotropic linearized elasticity term to the model relatively to the variable <literal>varname</literal>. <literal>data_E</literal> and <literal>data_nu</literal> should contain the Young modulus and Poisson ratio, respectively. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. On two-dimensional meshes, the term will correpsond to a plain stress approximation. On three-dimensional meshes, it will correspond to the standard model. Return the brick index in the model.

ind = gf_model_set(model M, 'add linear incompressibility brick', mesh_im mim, string varname, string multname_pressure[, int region[, string dataexpr_coeff]])Add a linear incompressibility condition on <literal>variable</literal>. <literal>multname_pressure</literal> is a variable which represent the pressure. Be aware that an inf-sup condition between the finite element method describing the pressure and the primal variable has to be satisfied. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. <literal>dataexpr_coeff</literal> is an optional penalization coefficient for nearly incompressible elasticity for instance. In this case, it is the inverse of the Lame coefficient <latex style=”text”><![CDATA[lambda]]></latex>. Return the brick index in the model.

ind = gf_model_set(model M, 'add nonlinear elasticity brick', mesh_im mim, string varname, string constitutive_law, string dataname[, int region])Add a nonlinear elasticity term to the model relatively to the variable <literal>varname</literal> (deprecated brick, use add_finite_strain_elaticity instead). <literal>lawname</literal> is the constitutive law which could be ‘SaintVenant Kirchhoff’, ‘Mooney Rivlin’, ‘neo Hookean’, ‘Ciarlet Geymonat’ or ‘generalized Blatz Ko’. ‘Mooney Rivlin’ and ‘neo Hookean’ law names can be preceded with the word ‘compressible’ or ‘incompressible’ to force using the corresponding version. The compressible version of these laws requires one additional material coefficient. By default, the incompressible version of ‘Mooney Rivlin’ law and the compressible one of the ‘neo Hookean’ law are considered. In general, ‘neo Hookean’ is a special case of the ‘Mooney Rivlin’ law that requires one coefficient less. IMPORTANT : if the variable is defined on a 2D mesh, the plane strain approximation is automatically used. <literal>dataname</literal> is a vector of parameters for the constitutive law. Its length depends on the law. It could be a short vector of constant values or a vector field described on a finite element method for variable coefficients. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. This brick use the low-level generic assembly. Returns the brick index in the model.

ind = gf_model_set(model M, 'add finite strain elasticity brick', mesh_im mim, string constitutive_law, string varname, string params[, int region])Add a nonlinear elasticity term to the model relatively to the variable <literal>varname</literal>. <literal>lawname</literal> is the constitutive law which could be ‘SaintVenant Kirchhoff’, ‘Mooney Rivlin’, ‘Neo Hookean’, ‘Ciarlet Geymonat’ or ‘Generalized Blatz Ko’. ‘Mooney Rivlin’ and ‘Neo Hookean’ law names have to be preceeded with the word ‘Compressible’ or ‘Incompressible’ to force using the corresponding version. The compressible version of these laws requires one additional material coefficient.

IMPORTANT : if the variable is defined on a 2D mesh, the plane strain approximation is automatically used. <literal>params</literal> is a vector of parameters for the constitutive law. Its length depends on the law. It could be a short vector of constant values or a vector field described on a finite element method for variable coefficients. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. This brick use the high-level generic assembly. Returns the brick index in the model.

ind = gf_model_set(model M, 'add small strain elastoplasticity brick', mesh_im mim, string lawname, string unknowns_type [, string varnames, ...] [, string params, ...] [, string theta = '1' [, string dt = 'timestep']] [, int region = -1])Adds a small strain plasticity term to the model <literal>M</literal>. This is the main GetFEM++ brick for small strain plasticity. <literal>lawname</literal> is the name of an implemented plastic law, <literal>unknowns_type</literal> indicates the choice between a discretization where the plastic multiplier is an unknown of the problem or (return mapping approach) just a data of the model stored for the next iteration. Remember that in both cases, a multiplier is stored anyway. <literal>varnames</literal> is a set of variable and data names with length which may depend on the plastic law (at least the displacement, the plastic multiplier and the plastic strain). <literal>params</literal> is a list of expressions for the parameters (at least elastic coefficients and the yield stress). These expressions can be some data names (or even variable names) of the model but can also be any scalar valid expression of the high level assembly language (such as ‘1/2’, ‘2+sin(X[0])’, ‘1+Norm(v)’ ...). The last two parameters optionally provided in <literal>params</literal> are the <literal>theta</literal> parameter of the <literal>theta</literal>-scheme (generalized trapezoidal rule) used for the plastic strain integration and the time-step<literal>dt</literal>. The default value for <literal>theta</literal> if omitted is 1, which corresponds to the classical Backward Euler scheme which is first order consistent. <literal>theta=1/2</literal> corresponds to the Crank-Nicolson scheme (trapezoidal rule) which is second order consistent. Any value between 1/2 and 1 should be a valid value. The default value of <literal>dt</literal> is ‘timestep’ which simply indicates the time step defined in the model (by md.set_time_step(dt)). Alternatively it can be any expression (data name, constant value ...). The time step can be altered from one iteration to the next one. <literal>region</literal> is a mesh region.

The available plasticity laws are:

- ‘Prandtl Reuss’ (or ‘isotropic perfect plasticity’). Isotropic elasto-plasticity with no hardening. The variables are the displacement, the plastic multiplier and the plastic strain. The displacement should be a variable and have a corresponding data having the same name preceded by ‘Previous_’ corresponding to the displacement at the previous time step (typically ‘u’ and ‘Previous_u’). The plastic multiplier should also have two versions (typically ‘xi’ and ‘Previous_xi’) the first one being defined as data if <literal>unknowns_type </literal> is ‘DISPLACEMENT_ONLY’ or the integer value 0, or as a variable if <literal>unknowns_type</literal> is DISPLACEMENT_AND_PLASTIC_MULTIPLIER or the integer value 1. The plastic strain should represent a n x n data tensor field stored on mesh_fem or (preferably) on an im_data (corresponding to <literal>mim</literal>). The data are the first Lame coefficient, the second one (shear modulus) and the uniaxial yield stress. A typical call is gf_model_get(model M, ‘add small strain elastoplasticity brick’, mim, ‘Prandtl Reuss’, 0, ‘u’, ‘xi’, ‘Previous_Ep’, ‘lambda’, ‘mu’, ‘sigma_y’, ‘1’, ‘timestep’); IMPORTANT: Note that this law implements the 3D expressions. If it is used in 2D, the expressions are just transposed to the 2D. For the plane strain approximation, see below.
- “plane strain Prandtl Reuss” (or “plane strain isotropic perfect plasticity”) The same law as the previous one but adapted to the plane strain approximation. Can only be used in 2D.
- “Prandtl Reuss linear hardening” (or “isotropic plasticity linear hardening”). Isotropic elasto-plasticity with linear isotropic and kinematic hardening. An additional variable compared to “Prandtl Reuss” law: the accumulated plastic strain. Similarly to the plastic strain, it is only stored at the end of the time step, so a simple data is required (preferably on an im_data). Two additional parameters: the kinematic hardening modulus and the isotropic one. 3D expressions only. A typical call is gf_model_get(model M, ‘add small strain elastoplasticity brick’, mim, ‘Prandtl Reuss linear hardening’, 0, ‘u’, ‘xi’, ‘Previous_Ep’, ‘Previous_alpha’, ‘lambda’, ‘mu’, ‘sigma_y’, ‘H_k’, H_i’, ‘1’, ‘timestep’);
- “plane strain Prandtl Reuss linear hardening” (or “plane strain isotropic plasticity linear hardening”). The same law as the previous one but adapted to the plane strain approximation. Can only be used in 2D.
See GetFEM++ user documentation for further explanations on the discretization of the plastic flow and on the implemented plastic laws. See also GetFEM++ user documentation on time integration strategy (integration of transient problems).

IMPORTANT : remember that <literal>small_strain_elastoplasticity_next_iter</literal> has to be called at the end of each time step, before the next one (and before any post-treatment : this sets the value of the plastic strain and plastic multiplier).

ind = gf_model_set(model M, 'add elastoplasticity brick', mesh_im mim ,string projname, string varname, string previous_dep_name, string datalambda, string datamu, string datathreshold, string datasigma[, int region])Old (obsolete) brick which do not use the high level generic assembly. Add a nonlinear elastoplastic term to the model relatively to the variable <literal>varname</literal>, in small deformations, for an isotropic material and for a quasistatic model. <literal>projname</literal> is the type of projection that used: only the Von Mises projection is available with ‘VM’ or ‘Von Mises’. <literal>datasigma</literal> is the variable representing the constraints on the material. <literal>previous_dep_name</literal> represents the displacement at the previous time step. Moreover, the finite element method on which <literal>varname</literal> is described is an K ordered mesh_fem, the <literal>datasigma</literal> one have to be at least an K-1 ordered mesh_fem. <literal>datalambda</literal> and <literal>datamu</literal> are the Lame coefficients of the studied material. <literal>datathreshold</literal> is the plasticity threshold of the material. The three last variables could be constants or described on the same finite element method. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model.

ind = gf_model_set(model M, 'add finite strain elastoplasticity brick', mesh_im mim , string lawname, string unknowns_type [, string varnames, ...] [, string params, ...] [, int region = -1])Add a finite strain elastoplasticity brick to the model. For the moment there is only one supported law defined through <literal>lawname</literal> as “Simo_Miehe”. This law supports to possibilities of unknown variables to solve for defined by means of <literal>unknowns_type</literal> set to either ‘DISPLACEMENT_AND_PLASTIC_MULTIPLIER’ (integer value 1) or ‘DISPLACEMENT_AND_PLASTIC_MULTIPLIER_AND_PRESSURE’ (integer value 3). The “Simo_Miehe” law expects as <literal>varnames</literal> a set of the following names that have to be defined as variables in the model:

- the displacement variable which has to be defined as an unknown,
- the plastic multiplier which has also defined as an unknown,
- optionally the pressure variable for a mixed displacement-pressure formulation for ‘DISPLACEMENT_AND_PLASTIC_MULTIPLIER_AND_PRESSURE’ as <literal>unknowns_type</literal>,
- the name of a (scalar) fem_data or im_data field that holds the plastic strain at the previous time step, and
- the name of a fem_data or im_data field that holds all non-repeated components of the inverse of the plastic right Cauchy-Green tensor at the previous time step (it has to be a 4 element vector for plane strain 2D problems and a 6 element vector for 3D problems).
The “Simo_Miehe” law also expects as <literal>params</literal> a set of the following three parameters:

- an expression for the initial bulk modulus K,
- an expression for the initial shear modulus G,
- the name of a user predefined function that decribes the yield limit as a function of the hardening variable (both the yield limit and the hardening variable values are assumed to be Frobenius norms of appropriate stress and strain tensors, respectively).
As usual, <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model.

ind = gf_model_set(model M, 'add nonlinear incompressibility brick', mesh_im mim, string varname, string multname_pressure[, int region])Add a nonlinear incompressibility condition on <literal>variable</literal> (for large strain elasticity). <literal>multname_pressure</literal> is a variable which represent the pressure. Be aware that an inf-sup condition between the finite element method describing the pressure and the primal variable has to be satisfied. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model.

ind = gf_model_set(model M, 'add finite strain incompressibility brick', mesh_im mim, string varname, string multname_pressure[, int region])Add a finite strain incompressibility condition on <literal>variable</literal> (for large strain elasticity). <literal>multname_pressure</literal> is a variable which represent the pressure. Be aware that an inf-sup condition between the finite element method describing the pressure and the primal variable has to be satisfied. <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model. This brick is equivalent to the <literal></literal>nonlinear incompressibility brick<literal></literal> but uses the high-level generic assembly adding the term <literal></literal>p*(1-Det(Id(meshdim)+Grad_u))<literal></literal> if <literal></literal>p<literal></literal> is the multiplier and <literal></literal>u<literal></literal> the variable which represent the displacement.

ind = gf_model_set(model M, 'add bilaplacian brick', mesh_im mim, string varname, string dataname [, int region])Add a bilaplacian brick on the variable <literal>varname</literal> and on the mesh region <literal>region</literal>. This represent a term <latex style=”text”><![CDATA[Delta(D Delta u)]]></latex>. where <latex style=”text”><![CDATA[D(x)]]></latex> is a coefficient determined by <literal>dataname</literal> which could be constant or described on a f.e.m. The corresponding weak form is <latex style=”text”><![CDATA[int D(x)Delta u(x) Delta v(x) dx]]></latex>. Return the brick index in the model.

ind = gf_model_set(model M, 'add Kirchhoff-Love plate brick', mesh_im mim, string varname, string dataname_D, string dataname_nu [, int region])Add a bilaplacian brick on the variable <literal>varname</literal> and on the mesh region <literal>region</literal>. This represent a term <latex style=”text”><![CDATA[Delta(D Delta u)]]></latex> where <latex style=”text”><![CDATA[D(x)]]></latex> is a the flexion modulus determined by <literal>dataname_D</literal>. The term is integrated by part following a Kirchhoff-Love plate model with <literal>dataname_nu</literal> the poisson ratio. Return the brick index in the model.

ind = gf_model_set(model M, 'add normal derivative source term brick', mesh_im mim, string varname, string dataname, int region)Add a normal derivative source term brick <latex style=”text”><![CDATA[F = int b.partial_n v]]></latex> on the variable <literal>varname</literal> and the mesh region <literal>region</literal>.

Update the right hand side of the linear system. <literal>dataname</literal> represents <literal>b</literal> and <literal>varname</literal> represents <literal>v</literal>. Return the brick index in the model.

ind = gf_model_set(model M, 'add Kirchhoff-Love Neumann term brick', mesh_im mim, string varname, string dataname_M, string dataname_divM, int region)Add a Neumann term brick for Kirchhoff-Love model on the variable <literal>varname</literal> and the mesh region <literal>region</literal>. <literal>dataname_M</literal> represents the bending moment tensor and <literal>dataname_divM</literal> its divergence. Return the brick index in the model.

ind = gf_model_set(model M, 'add normal derivative Dirichlet condition with multipliers', mesh_im mim, string varname, mult_description, int region [, string dataname, int R_must_be_derivated])Add a Dirichlet condition on the normal derivative of the variable <literal>varname</literal> and on the mesh region <literal>region</literal> (which should be a boundary. The general form is <latex style=”text”><![CDATA[int partial_n u(x)v(x) = int r(x)v(x) forall v]]></latex> where <latex style=”text”><![CDATA[r(x)]]></latex> is the right hand side for the Dirichlet condition (0 for homogeneous conditions) and <latex style=”text”><![CDATA[v]]></latex> is in a space of multipliers defined by <literal>mult_description</literal>. If <literal>mult_description</literal> is a string this is assumed to be the variable name corresponding to the multiplier (which should be first declared as a multiplier variable on the mesh region in the model). If it is a finite element method (mesh_fem object) then a multiplier variable will be added to the model and build on this finite element method (it will be restricted to the mesh region <literal>region</literal> and eventually some conflicting dofs with some other multiplier variables will be suppressed). If it is an integer, then a multiplier variable will be added to the model and build on a classical finite element of degree that integer. <literal>dataname</literal> is an optional parameter which represents the right hand side of the Dirichlet condition. If <literal>R_must_be_derivated</literal> is set to <literal>true</literal> then the normal derivative of <literal>dataname</literal> is considered. Return the brick index in the model.

ind = gf_model_set(model M, 'add normal derivative Dirichlet condition with penalization', mesh_im mim, string varname, scalar coeff, int region [, string dataname, int R_must_be_derivated])Add a Dirichlet condition on the normal derivative of the variable <literal>varname</literal> and on the mesh region <literal>region</literal> (which should be a boundary. The general form is <latex style=”text”><![CDATA[int partial_n u(x)v(x) = int r(x)v(x) forall v]]></latex> where <latex style=”text”><![CDATA[r(x)]]></latex> is the right hand side for the Dirichlet condition (0 for homogeneous conditions). The penalization coefficient is initially <literal>coeff</literal> and will be added to the data of the model. It can be changed with the command gf_model_set(model M, ‘change penalization coeff’). <literal>dataname</literal> is an optional parameter which represents the right hand side of the Dirichlet condition. If <literal>R_must_be_derivated</literal> is set to <literal>true</literal> then the normal derivative of <literal>dataname</literal> is considered. Return the brick index in the model.

ind = gf_model_set(model M, 'add Mindlin Reissner plate brick', mesh_im mim, mesh_im mim_reduced, string varname_u3, string varname_theta , string param_E, string param_nu, string param_epsilon, string param_kappa [,int variant [, int region]])Add a term corresponding to the classical Reissner-Mindlin plate model for which <literal>varname_u3</literal> is the transverse displacement, <literal>varname_theta</literal> the rotation of fibers normal to the midplane, ‘param_E’ the Young Modulus, <literal>param_nu</literal> the poisson ratio, <literal>param_epsilon</literal> the plate thickness, <literal>param_kappa</literal> the shear correction factor. Note that since this brick uses the high level generic assembly language, the parameter can be regular expression of this language. There are three variants. <literal>variant = 0</literal> corresponds to the an unreduced formulation and in that case only the integration method <literal>mim</literal> is used. Practically this variant is not usable since it is subject to a strong locking phenomenon. <literal>variant = 1</literal> corresponds to a reduced integration where <literal>mim</literal> is used for the rotation term and <literal>mim_reduced</literal> for the transverse shear term. <literal>variant = 2</literal> (default) corresponds to the projection onto a rotated RT0 element of the transverse shear term. For the moment, this is adapted to quadrilateral only (because it is not sufficient to remove the locking phenomenon on triangle elements). Note also that if you use high order elements, the projection on RT0 will reduce the order of the approximation. Returns the brick index in the model.

ind = gf_model_set(model M, 'add mass brick', mesh_im mim, string varname[, string dataexpr_rho[, int region]])Add mass term to the model relatively to the variable <literal>varname</literal>. If specified, the data <literal>dataexpr_rho</literal> is the density (1 if omitted). <literal>region</literal> is an optional mesh region on which the term is added. If it is not specified, it is added on the whole mesh. Return the brick index in the model.

gf_model_set(model M, 'shift variables for time integration')Function used to shift the variables of a model to the data corresponding of ther value on the previous time step for time integration schemes. For each variable for which a time integration scheme has been declared, the scheme is called to perform the shift. This function has to be called between two time steps.

gf_model_set(model M, 'perform init time derivative', scalar ddt)By calling this function, indicates that the next solve will compute the solution for a (very) small time step <literal>ddt</literal> in order to initalize the data corresponding to the derivatives needed by time integration schemes (mainly the initial time derivative for order one in time problems and the second order time derivative for second order in time problems). The next solve will not change the value of the variables.

gf_model_set(model M, 'set time step', scalar dt)Set the value of the time step to <literal>dt</literal>. This value can be change from a step to another for all one-step schemes (i.e for the moment to all proposed time integration schemes).

gf_model_set(model M, 'set time', scalar t)Set the value of the data <literal>t</literal> corresponding to the current time to <literal>t</literal>.

gf_model_set(model M, 'add theta method for first order', string varname, scalar theta)Attach a theta method for the time discretization of the variable <literal>varname</literal>. Valid only if there is at most first order time derivative of the variable.

gf_model_set(model M, 'add theta method for second order', string varname, scalar theta)Attach a theta method for the time discretization of the variable <literal>varname</literal>. Valid only if there is at most second order time derivative of the variable.

gf_model_set(model M, 'add Newmark scheme', string varname, scalar beta, scalar gamma)Attach a theta method for the time discretization of the variable <literal>varname</literal>. Valid only if there is at most second order time derivative of the variable.

gf_model_set(model M, 'disable bricks', ivec bricks_indices)Disable a brick (the brick will no longer participate to the building of the tangent linear system).

gf_model_set(model M, 'enable bricks', ivec bricks_indices)Enable a disabled brick.

gf_model_set(model M, 'disable variable', string varname)Disable a variable for a solve (and its attached multipliers). The next solve will operate only on the remaining variables. This allows to solve separately different parts of a model. If there is a strong coupling of the variables, a fixed point strategy can the be used.

gf_model_set(model M, 'enable variable', string varname)Enable a disabled variable (and its attached multipliers).

gf_model_set(model M, 'first iter')To be executed before the first iteration of a time integration scheme.

gf_model_set(model M, 'next iter')To be executed at the end of each iteration of a time integration scheme.

ind = gf_model_set(model M, 'add basic contact brick', string varname_u, string multname_n[, string multname_t], string dataname_r, spmat BN[, spmat BT, string dataname_friction_coeff][, string dataname_gap[, string dataname_alpha[, int augmented_version[, string dataname_gamma, string dataname_wt]]])Add a contact with or without friction brick to the model. If U is the vector of degrees of freedom on which the unilateral constraint is applied, the matrix <literal>BN</literal> have to be such that this constraint is defined by <latex style=”text”><![CDATA[B_N U le 0]]></latex>. A friction condition can be considered by adding the three parameters <literal>multname_t</literal>, <literal>BT</literal> and <literal>dataname_friction_coeff</literal>. In this case, the tangential displacement is <latex style=”text”><![CDATA[B_T U]]></latex> and the matrix <literal>BT</literal> should have as many rows as <literal>BN</literal> multiplied by <latex style=”text”><![CDATA[d-1]]></latex> where <latex style=”text”><![CDATA[d]]></latex> is the domain dimension. In this case also, <literal>dataname_friction_coeff</literal> is a data which represents the coefficient of friction. It can be a scalar or a vector representing a value on each contact condition. The unilateral constraint is prescribed thank to a multiplier <literal>multname_n</literal> whose dimension should be equal to the number of rows of <literal>BN</literal>. If a friction condition is added, it is prescribed with a multiplier <literal>multname_t</literal> whose dimension should be equal to the number of rows of <literal>BT</literal>. The augmentation parameter <literal>r</literal> should be chosen in a range of acceptabe values (see Getfem user documentation). <literal>dataname_gap</literal> is an optional parameter representing the initial gap. It can be a single value or a vector of value. <literal>dataname_alpha</literal> is an optional homogenization parameter for the augmentation parameter (see Getfem user documentation). The parameter <literal>augmented_version</literal> indicates the augmentation strategy : 1 for the non-symmetric Alart-Curnier augmented Lagrangian, 2 for the symmetric one (except for the coupling between contact and Coulomb friction), 3 for the unsymmetric method with augmented multipliers, 4 for the unsymmetric method with augmented multipliers and De Saxce projection.

ind = gf_model_set(model M, 'add basic contact brick two deformable bodies', string varname_u1, string varname_u2, string multname_n, string dataname_r, spmat BN1, spmat BN2[, string dataname_gap[, string dataname_alpha[, int augmented_version]]])

- Add a frictionless contact condition to the model between two deformable
- bodies. If U1, U2 are the vector of degrees of freedom on which the unilateral constraint is applied, the matrices <literal>BN1</literal> and <literal>BN2</literal> have to be such that this condition is defined by $B_{N1} U_1 B_{N2} U_2 + le gap$. The constraint is prescribed thank to a multiplier <literal>multname_n</literal> whose dimension should be equal to the number of lines of <literal>BN</literal>. The augmentation parameter <literal>r</literal> should be chosen in a range of acceptabe values (see Getfem user documentation). <literal>dataname_gap</literal> is an optional parameter representing the initial gap. It can be a single value or a vector of value. <literal>dataname_alpha</literal> is an optional homogenization parameter for the augmentation parameter (see Getfem user documentation). The parameter <literal>aug_version</literal> indicates the augmentation strategy : 1 for the non-symmetric Alart-Curnier augmented Lagrangian, 2 for the symmetric one, 3 for the unsymmetric method with augmented multiplier.

gf_model_set(model M, 'contact brick set BN', int indbrick, spmat BN)Can be used to set the BN matrix of a basic contact/friction brick.

gf_model_set(model M, 'contact brick set BT', int indbrick, spmat BT)Can be used to set the BT matrix of a basic contact with friction brick.

ind = gf_model_set(model M, 'add nodal contact with rigid obstacle brick', mesh_im mim, string varname_u, string multname_n[, string multname_t], string dataname_r[, string dataname_friction_coeff], int region, string obstacle[, int augmented_version])Add a contact with or without friction condition with a rigid obstacle to the model. The condition is applied on the variable <literal>varname_u</literal> on the boundary corresponding to <literal>region</literal>. The rigid obstacle should be described with the string <literal>obstacle</literal> being a signed distance to the obstacle. This string should be an expression where the coordinates are ‘x’, ‘y’ in 2D and ‘x’, ‘y’, ‘z’ in 3D. For instance, if the rigid obstacle correspond to <latex style=”text”><![CDATA[z le 0]]></latex>, the corresponding signed distance will be simply “z”. <literal>multname_n</literal> should be a fixed size variable whose size is the number of degrees of freedom on boundary <literal>region</literal>. It represents the contact equivalent nodal forces. In order to add a friction condition one has to add the <literal>multname_t</literal> and <literal>dataname_friction_coeff</literal> parameters. <literal>multname_t</literal> should be a fixed size variable whose size is the number of degrees of freedom on boundary <literal>region</literal> multiplied by <latex style=”text”><![CDATA[d-1]]></latex> where <latex style=”text”><![CDATA[d]]></latex> is the domain dimension. It represents the friction equivalent nodal forces. The augmentation parameter <literal>r</literal> should be chosen in a range of acceptabe values (close to the Young modulus of the elastic body, see Getfem user documentation). <literal>dataname_friction_coeff</literal> is the friction coefficient. It could be a scalar or a vector of values representing the friction coefficient on each contact node. The parameter <literal>augmented_version</literal> indicates the augmentation strategy : 1 for the non-symmetric Alart-Curnier augmented Lagrangian, 2 for the symmetric one (except for the coupling between contact and Coulomb friction), 3 for the new unsymmetric method. Basically, this brick compute the matrix BN and the vectors gap and alpha and calls the basic contact brick.

ind = gf_model_set(model M, 'add contact with rigid obstacle brick', mesh_im mim, string varname_u, string multname_n[, string multname_t], string dataname_r[, string dataname_friction_coeff], int region, string obstacle[, int augmented_version])DEPRECATED FUNCTION. Use ‘add nodal contact with rigid obstacle brick’ instead.

ind = gf_model_set(model M, 'add integral contact with rigid obstacle brick', mesh_im mim, string varname_u, string multname, string dataname_obstacle, string dataname_r [, string dataname_friction_coeff], int region [, int option [, string dataname_alpha [, string dataname_wt [, string dataname_gamma [, string dataname_vt]]]]])Add a contact with or without friction condition with a rigid obstacle to the model. This brick adds a contact which is defined in an integral way. It is the direct approximation of an augmented Lagrangian formulation (see Getfem user documentation) defined at the continuous level. The advantage is a better scalability: the number of Newton iterations should be more or less independent of the mesh size. The contact condition is applied on the variable <literal>varname_u</literal> on the boundary corresponding to <literal>region</literal>. The rigid obstacle should be described with the data <literal>dataname_obstacle</literal> being a signed distance to the obstacle (interpolated on a finite element method). <literal>multname</literal> should be a fem variable representing the contact stress. An inf-sup condition beetween <literal>multname</literal> and <literal>varname_u</literal> is required. The augmentation parameter <literal>dataname_r</literal> should be chosen in a range of acceptabe values. The optional parameter <literal>dataname_friction_coeff</literal> is the friction coefficient which could be constant or defined on a finite element method. Possible values for <literal>option</literal> is 1 for the non-symmetric Alart-Curnier augmented Lagrangian method, 2 for the symmetric one, 3 for the non-symmetric Alart-Curnier method with an additional augmentation and 4 for a new unsymmetric method. The default value is 1. In case of contact with friction, <literal>dataname_alpha</literal> and <literal>dataname_wt</literal> are optional parameters to solve evolutionary friction problems. <literal>dataname_gamma</literal> and <literal>dataname_vt</literal> represent optional data for adding a parameter-dependent sliding velocity to the friction condition.

ind = gf_model_set(model M, 'add penalized contact with rigid obstacle brick', mesh_im mim, string varname_u, string dataname_obstacle, string dataname_r [, string dataname_coeff], int region [, int option, string dataname_lambda, [, string dataname_alpha [, string dataname_wt]]])Add a penalized contact with or without friction condition with a rigid obstacle to the model. The condition is applied on the variable <literal>varname_u</literal> on the boundary corresponding to <literal>region</literal>. The rigid obstacle should be described with the data <literal>dataname_obstacle</literal> being a signed distance to the obstacle (interpolated on a finite element method). The penalization parameter <literal>dataname_r</literal> should be chosen large enough to prescribe approximate non-penetration and friction conditions but not too large not to deteriorate too much the conditionning of the tangent system. <literal>dataname_lambda</literal> is an optional parameter used if option is 2. In that case, the penalization term is shifted by lambda (this allows the use of an Uzawa algorithm on the corresponding augmented Lagrangian formulation)

ind = gf_model_set(model M, 'add Nitsche contact with rigid obstacle brick', mesh_im mim, string varname, string Neumannterm, string dataname_obstacle, string gamma0name, int region[, scalar theta[, string dataname_friction_coeff[, string dataname_alpha, string dataname_wt]]])Adds a contact condition with or without Coulomb friction on the variable <literal>varname</literal> and the mesh boundary <literal>region</literal>. The contact condition is prescribed with Nitsche’s method. The rigid obstacle should be described with the data <literal>dataname_obstacle</literal> being a signed distance to the obstacle (interpolated on a finite element method). <literal>gamma0name</literal> is the Nitsche’s method parameter. <literal>theta</literal> is a scalar value which can be positive or negative. <literal>theta = 1</literal> corresponds to the standard symmetric method which is conditionnaly coercive for <literal>gamma0</literal> small. <literal>theta = -1</literal> corresponds to the skew-symmetric method which is inconditionnaly coercive. <literal>theta = 0</literal> is the simplest method for which the second derivative of the Neumann term is not necessary. The optional parameter <literal>dataname_friction_coeff</literal> is the friction coefficient which could be constant or defined on a finite element method. CAUTION: This brick has to be added in the model after all the bricks corresponding to partial differential terms having a Neumann term. Moreover, This brick can only be applied to bricks declaring their Neumann terms. Returns the brick index in the model.

ind = gf_model_set(model M, 'add Nitsche midpoint contact with rigid obstacle brick', mesh_im mim, string varname, string Neumannterm, string Neumannterm_wt, string dataname_obstacle, string gamma0name, int region, scalar theta, string dataname_friction_coeff, string dataname_alpha, string dataname_wt)EXPERIMENTAL BRICK: for midpoint scheme only !! Adds a contact condition with or without Coulomb friction on the variable <literal>varname</literal> and the mesh boundary <literal>region</literal>. The contact condition is prescribed with Nitsche’s method. The rigid obstacle should be described with the data <literal>dataname_obstacle</literal> being a signed distance to the obstacle (interpolated on a finite element method). <literal>gamma0name</literal> is the Nitsche’s method parameter. <literal>theta</literal> is a scalar value which can be positive or negative. <literal>theta = 1</literal> corresponds to the standard symmetric method which is conditionnaly coercive for <literal>gamma0</literal> small. <literal>theta = -1</literal> corresponds to the skew-symmetric method which is inconditionnaly coercive. <literal>theta = 0</literal> is the simplest method for which the second derivative of the Neumann term is not necessary. The optional parameter <literal>dataname_friction_coeff</literal> is the friction coefficient which could be constant or defined on a finite element method. Returns the brick index in the model.

ind = gf_model_set(model M, 'add Nitsche fictitious domain contact brick', mesh_im mim, string varname1, string varname2, string dataname_d1, string dataname_d2, string gamma0name [, scalar theta[, string dataname_friction_coeff[, string dataname_alpha, string dataname_wt1,string dataname_wt2]]])Adds a contact condition with or without Coulomb friction between two bodies in a fictitious domain. The contact condition is applied on the variable <literal>varname_u1</literal> corresponds with the first and slave body with Nitsche’s method and on the variable <literal>varname_u2</literal> corresponds with the second and master body with Nitsche’s method. The contact condition is evaluated on the fictitious slave boundary. The first body should be described by the level-set <literal>dataname_d1</literal> and the second body should be described by the level-set <literal>dataname_d2</literal>. <literal>gamma0name</literal> is the Nitsche’s method parameter. <literal>theta</literal> is a scalar value which can be positive or negative. <literal>theta = 1</literal> corresponds to the standard symmetric method which is conditionnaly coercive for <literal>gamma0</literal> small. <literal>theta = -1</literal> corresponds to the skew-symmetric method which is inconditionnaly coercive. <literal>theta = 0</literal> is the simplest method for which the second derivative of the Neumann term is not necessary. The optional parameter <literal>dataname_friction_coeff</literal> is the friction coefficient which could be constant or defined on a finite element method. CAUTION: This brick has to be added in the model after all the bricks corresponding to partial differential terms having a Neumann term. Moreover, This brick can only be applied to bricks declaring their Neumann terms. Returns the brick index in the model.

ind = gf_model_set(model M, 'add nodal contact between nonmatching meshes brick', mesh_im mim1[, mesh_im mim2], string varname_u1[, string varname_u2], string multname_n[, string multname_t], string dataname_r[, string dataname_fr], int rg1, int rg2[, int slave1, int slave2, int augmented_version])Add a contact with or without friction condition between two faces of one or two elastic bodies. The condition is applied on the variable <literal>varname_u1</literal> or the variables <literal>varname_u1</literal> and <literal>varname_u2</literal> depending if a single or two distinct displacement fields are given. Integers <literal>rg1</literal> and <literal>rg2</literal> represent the regions expected to come in contact with each other. In the single displacement variable case the regions defined in both <literal>rg1</literal> and <literal>rg2</literal> refer to the variable <literal>varname_u1</literal>. In the case of two displacement variables, <literal>rg1</literal> refers to <literal>varname_u1</literal> and <literal>rg2</literal> refers to <literal>varname_u2</literal>. <literal>multname_n</literal> should be a fixed size variable whose size is the number of degrees of freedom on those regions among the ones defined in <literal>rg1</literal> and <literal>rg2</literal> which are characterized as “slaves”. It represents the contact equivalent nodal normal forces. <literal>multname_t</literal> should be a fixed size variable whose size corresponds to the size of <literal>multname_n</literal> multiplied by qdim - 1 . It represents the contact equivalent nodal tangent (frictional) forces. The augmentation parameter <literal>r</literal> should be chosen in a range of acceptabe values (close to the Young modulus of the elastic body, see Getfem user documentation). The friction coefficient stored in the parameter <literal>fr</literal> is either a single value or a vector of the same size as <literal>multname_n</literal>. The optional parameters <literal>slave1</literal> and <literal>slave2</literal> declare if the regions defined in <literal>rg1</literal> and <literal>rg2</literal> are correspondingly considered as “slaves”. By default <literal>slave1</literal> is true and <literal>slave2</literal> is false, i.e. <literal>rg1</literal> contains the slave surfaces, while ‘rg2’ the master surfaces. Preferrably only one of <literal>slave1</literal> and <literal>slave2</literal> is set to true. The parameter <literal>augmented_version</literal> indicates the augmentation strategy : 1 for the non-symmetric Alart-Curnier augmented Lagrangian, 2 for the symmetric one (except for the coupling between contact and Coulomb friction), 3 for the new unsymmetric method. Basically, this brick computes the matrices BN and BT and the vectors gap and alpha and calls the basic contact brick.

ind = gf_model_set(model M, 'add nonmatching meshes contact brick', mesh_im mim1[, mesh_im mim2], string varname_u1[, string varname_u2], string multname_n[, string multname_t], string dataname_r[, string dataname_fr], int rg1, int rg2[, int slave1, int slave2, int augmented_version])DEPRECATED FUNCTION. Use ‘add nodal contact between nonmatching meshes brick’ instead.

ind = gf_model_set(model M, 'add integral contact between nonmatching meshes brick', mesh_im mim, string varname_u1, string varname_u2, string multname, string dataname_r [, string dataname_friction_coeff], int region1, int region2 [, int option [, string dataname_alpha [, string dataname_wt1 , string dataname_wt2]]])Add a contact with or without friction condition between nonmatching meshes to the model. This brick adds a contact which is defined in an integral way. It is the direct approximation of an augmented agrangian formulation (see Getfem user documentation) defined at the continuous level. The advantage should be a better scalability: the number of Newton iterations should be more or less independent of the mesh size. The condition is applied on the variables <literal>varname_u1</literal> and <literal>varname_u2</literal> on the boundaries corresponding to <literal>region1</literal> and <literal>region2</literal>. <literal>multname</literal> should be a fem variable representing the contact stress for the frictionless case and the contact and friction stress for the case with friction. An inf-sup condition between <literal>multname</literal> and <literal>varname_u1</literal> and <literal>varname_u2</literal> is required. The augmentation parameter <literal>dataname_r</literal> should be chosen in a range of acceptable values. The optional parameter <literal>dataname_friction_coeff</literal> is the friction coefficient which could be constant or defined on a finite element method on the same mesh as <literal>varname_u1</literal>. Possible values for <literal>option</literal> is 1 for the non-symmetric Alart-Curnier augmented Lagrangian method, 2 for the symmetric one, 3 for the non-symmetric Alart-Curnier method with an additional augmentation and 4 for a new unsymmetric method. The default value is 1. In case of contact with friction, <literal>dataname_alpha</literal>, <literal>dataname_wt1</literal> and <literal>dataname_wt2</literal> are optional parameters to solve evolutionary friction problems.

ind = gf_model_set(model M, 'add penalized contact between nonmatching meshes brick', mesh_im mim, string varname_u1, string varname_u2, string dataname_r [, string dataname_coeff], int region1, int region2 [, int option [, string dataname_lambda, [, string dataname_alpha [, string dataname_wt1, string dataname_wt2]]]])Add a penalized contact condition with or without friction between nonmatching meshes to the model. The condition is applied on the variables <literal>varname_u1</literal> and <literal>varname_u2</literal> on the boundaries corresponding to <literal>region1</literal> and <literal>region2</literal>. The penalization parameter <literal>dataname_r</literal> should be chosen large enough to prescribe approximate non-penetration and friction conditions but not too large not to deteriorate too much the conditionning of the tangent system. The optional parameter <literal>dataname_friction_coeff</literal> is the friction coefficient which could be constant or defined on a finite element method on the same mesh as <literal>varname_u1</literal>. <literal>dataname_lambda</literal> is an optional parameter used if option is 2. In that case, the penalization term is shifted by lambda (this allows the use of an Uzawa algorithm on the corresponding augmented Lagrangian formulation) In case of contact with friction, <literal>dataname_alpha</literal>, <literal>dataname_wt1</literal> and <literal>dataname_wt2</literal> are optional parameters to solve evolutionary friction problems.

ind = gf_model_set(model M, 'add integral large sliding contact brick raytracing', string dataname_r, scalar release_distance, [, string dataname_fr[, string dataname_alpha[, int version]]])Adds a large sliding contact with friction brick to the model. This brick is able to deal with self-contact, contact between several deformable bodies and contact with rigid obstacles. It uses the high-level generic assembly. It adds to the model a raytracing_interpolate_transformation object. For each slave boundary a multiplier variable should be defined. The release distance should be determined with care (generally a few times a mean element size, and less than the thickness of the body). Initially, the brick is added with no contact boundaries. The contact boundaries and rigid bodies are added with special functions. <literal>version</literal> is 0 (the default value) for the non-symmetric version and 1 for the more symmetric one (not fully symmetric even without friction).

gf_model_set(model M, 'add rigid obstacle to large sliding contact brick', int indbrick, string expr, int N)Adds a rigid obstacle to an existing large sliding contact with friction brick. <literal>expr</literal> is an expression using the high-level generic assembly language (where <literal>x</literal> is the current point n the mesh) which should be a signed distance to the obstacle. <literal>N</literal> is the mesh dimension.

gf_model_set(model M, 'add master contact boundary to large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname[, string wname])Adds a master contact boundary to an existing large sliding contact with friction brick.

gf_model_set(model M, 'add slave contact boundary to large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])Adds a slave contact boundary to an existing large sliding contact with friction brick.

gf_model_set(model M, 'add master slave contact boundary to large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])Adds a contact boundary to an existing large sliding contact with friction brick which is both master and slave (allowing the self-contact).

ind = gf_model_set(model M, 'add Nitsche large sliding contact brick raytracing', bool unbiased_version, string dataname_r, scalar release_distance[, string dataname_fr[, string dataname_alpha[, int version]]])Adds a large sliding contact with friction brick to the model based on the Nitsche’s method. This brick is able to deal with self-contact, contact between several deformable bodies and contact with rigid obstacles. It uses the high-level generic assembly. It adds to the model a raytracing_interpolate_transformation object. “unbiased_version” refers to the version of Nische’s method to be used. (unbiased or biased one). For each slave boundary a material law should be defined as a function of the dispacement variable on this boundary. The release distance should be determined with care (generally a few times a mean element size, and less than the thickness of the body). Initially, the brick is added with no contact boundaries. The contact boundaries and rigid bodies are added with special functions. <literal>version</literal> is 0 (the default value) for the non-symmetric version and 1 for the more symmetric one (not fully symmetric even without friction).

gf_model_set(model M, 'add rigid obstacle to Nitsche large sliding contact brick', int indbrick, string expr, int N)Adds a rigid obstacle to an existing large sliding contact with friction brick. <literal>expr</literal> is an expression using the high-level generic assembly language (where <literal>x</literal> is the current point n the mesh) which should be a signed distance to the obstacle. <literal>N</literal> is the mesh dimension.

gf_model_set(model M, 'add master contact boundary to biased Nitsche large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname[, string wname])Adds a master contact boundary to an existing biased Nitsche’s large sliding contact with friction brick.

gf_model_set(model M, 'add slave contact boundary to biased Nitsche large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])Adds a slave contact boundary to an existing biased Nitsche’s large sliding contact with friction brick.

gf_model_set(model M, 'add contact boundary to unbiased Nitsche large sliding contact brick', int indbrick, mesh_im mim, int region, string dispname, string lambdaname[, string wname])Adds a contact boundary to an existing unbiased Nitschelarge sliding contact with friction brick which is both master and slave.