[PL/TRM] Optional body forces for deformation

New tag, by default true, <apply_body_force_for_deformation>

Documentation/ProjectFile/prj/processes/process/THERMO_RICHARDS_MECHANICS/t_apply_body_force_for_deformation.md

+A tag that controls whether the body force should be applied to the displacement.
+Should be switched off if the initial stress already considers the body force.

ProcessLib/ThermoRichardsMechanics/CreateThermoRichardsMechanicsProcess.cpp

@@ -178,6 +178,11 @@ std::unique_ptr<Process> createThermoRichardsMechanicsProcess(
         mass_lumping = *mass_lumping_ptr;
     }
 
+    bool const apply_body_force_for_deformation =
+        //! \ogs_file_param{prj__processes__process__THERMO_RICHARDS_MECHANICS__apply_body_force_for_deformation}
+        config.getConfigParameter<bool>("apply_body_force_for_deformation",
+                                        true);
+
     const bool use_TaylorHood_elements =
         variable_p->getShapeFunctionOrder() !=
                 variable_u->getShapeFunctionOrder()
@@ -191,7 +196,8 @@ std::unique_ptr<Process> createThermoRichardsMechanicsProcess(
         initial_stress,
         specific_body_force,
         mass_lumping,
-        use_TaylorHood_elements};
+        use_TaylorHood_elements,
+        apply_body_force_for_deformation};
 
     SecondaryVariableCollection secondary_variables;
 

ProcessLib/ThermoRichardsMechanics/ThermoRichardsMechanicsFEM-impl.h

@@ -391,7 +391,8 @@ void ThermoRichardsMechanicsLocalAssembler<ShapeFunctionDisplacement,
     block_p(out.res).noalias() = dNdx.transpose() * CD.eq_p_data.rhs_p_dNT_V;
     block_u(out.res).noalias() =
         B.transpose() * CD.s_mech_data.sigma_total -
-        N_u_op.transpose() * CD.grav_data.volumetric_body_force;
+        static_cast<int>(this->process_data_.apply_body_force_for_deformation) *
+            N_u_op.transpose() * CD.grav_data.volumetric_body_force;
 
     // Storage matrices
     out.storage_p_a_p.noalias() = CD.eq_p_data.storage_p_a_p_X_NTN * NTN;

ProcessLib/ThermoRichardsMechanics/ThermoRichardsMechanicsProcessData.h

@@ -55,6 +55,8 @@ struct ThermoRichardsMechanicsProcessData
 
     const bool use_TaylorHood_elements;
 
+    bool const apply_body_force_for_deformation;
+
     MeshLib::PropertyVector<double>* element_saturation = nullptr;
     MeshLib::PropertyVector<double>* element_porosity = nullptr;
     MeshLib::PropertyVector<double>* element_liquid_density = nullptr;