Draft: Implement Nitsche method to couple embedded meshes

src/constraint_framework/4C_constraint_framework_embeddedmesh_interaction_pair.hpp

@@ -15,6 +15,7 @@
 #include "4C_io_visualization_data.hpp"
 #include "4C_linalg_fevector.hpp"
 #include "4C_linalg_fixedsizematrix.hpp"
+#include "4C_solid_3D_ele.hpp"
 #include "4C_utils_parameter_list.fwd.hpp"
 
 #include <memory>
@@ -42,6 +43,7 @@ namespace GeometryPair
 namespace Constraints::EmbeddedMesh
 {
   class SolidToSolidMortarManager;
+  class SolidToSolidNitscheManager;
 
   class SolidInteractionPair
   {
@@ -66,12 +68,12 @@ namespace Constraints::EmbeddedMesh
     /*!
     \brief Get first element
     */
-    const Core::Elements::Element& element_1() const { return *element1_.get(); };
+    Core::Elements::Element& element_1() const { return *element1_.get(); };
 
     /*!
     \brief Get second element
     */
-    const Core::Elements::Element& element_2() const { return *element2_; };
+    Core::Elements::Element& element_2() const { return *element2_; };
 
     /*!
     \brief Get the number of segments
@@ -126,6 +128,19 @@ namespace Constraints::EmbeddedMesh
         Core::LinAlg::FEVector<double>& global_kappa,
         Core::LinAlg::FEVector<double>& global_lambda_active) = 0;
 
+    virtual void evaluate_and_assemble_nitsche_contributions(
+        const Core::FE::Discretization& discret,
+        const Constraints::EmbeddedMesh::SolidToSolidNitscheManager* nitsche_manager,
+        Core::LinAlg::SparseMatrix& global_penalty_interface,
+        Core::LinAlg::SparseMatrix& global_penalty_background,
+        Core::LinAlg::SparseMatrix& global_penalty_interface_background,
+        Core::LinAlg::SparseMatrix& global_nitsche_interface,
+        Core::LinAlg::SparseMatrix& global_nitsche_background,
+        Core::LinAlg::SparseMatrix& global_nitsche_interface_background,
+        Core::LinAlg::FEVector<double>& global_penalty_constraint,
+        Core::LinAlg::FEVector<double>& global_nitsche_constraint,
+        double& nitsche_average_weight_param) = 0;
+
     /**
      * \brief Set the current element displacement.
      * @param discret (in) Discretization, used to get the boundary layer GIDs.
@@ -154,10 +169,10 @@ namespace Constraints::EmbeddedMesh
    private:
     //! @name member variables
     //! first element of interacting pair
-    const std::shared_ptr<Core::Elements::Element> element1_;
+    std::shared_ptr<Core::Elements::Element> element1_;
 
     //! second element of interacting pair
-    const Core::Elements::Element* element2_;
+    Core::Elements::Element* element2_;
 
     //! pointer to the cutwizard
     std::shared_ptr<Cut::CutWizard> cutwizard_ptr_ = nullptr;