How to Use the Meshes as Group

In kratos each modelpart can store several meshes. This meshes can be accessed via a unique id of the mesh given from input file with GetMesh (or pGetMesh ) method:

 ModelPart::MeshType& inlet_mesh = rThisModelPart.GetMesh(12); // 12 is the inlet group id in the input file

Loop Over Nodes

One can use the mesh object for accessing the node via NodesBegin and NodesEnd methods.

 for(ModelPart::NodeIterator i_node = inlet_mesh.NodesBegin(12);
     i_node != inlet_mesh.NodesEnd(12);
     i_node++)	
 {
     KRATOS_WATCH(i_node->Id()); //print the value of the node Id which belongs to inlet
 }

However the modelpart also provides the same methods with mesh Id as input to make the loop over the nodes of a mesh:

 for(ModelPart::NodeIterator i_node = model_part.NodesBegin(12);
     i_node != model_part.NodesEnd(12);
     i_node++)	
 {
     KRATOS_WATCH(i_node->Id()); //print the value of the node Id which belongs to inlet
 }

Loop over other entities

The loop over elements and conditions in a mesh is similar to the nodes described before. One can access it with a mesh reference:

 ModelPart::MeshType& structure_mesh = rThisModelPart.GetMesh(10); // 10 is the structure group id in the input file
 for(ModelPart::ElementIterator i_element = structure_mesh.NodesBegin(12);
     i_element != structure_mesh.NodesEnd(12);
     i_element++)	
 {
     KRATOS_WATCH(i_element->Id()); //print the value of the element Id which belongs to structure
 }

or via modelpart methods:

 for(ModelPart::ElementIterator i_element = model_part.NodesBegin(12);
     i_element != model_part.NodesEnd(12);
     i_element++)	
 {
     KRATOS_WATCH(i_element->Id()); //print the value of the element Id which belongs to structure
 }