Python Script Tutorial: Generating New Modelparts

ModelParts are the essential data structure to hold FEM objects in Kratos.

Since the "physics" of a problem is provided by the Element and Condition which implement it, in order to describe a new physical problem one should provide a new ModelPart describing the connectivity but also made of the relevant element technology.

In Kratos, essentially all of the FEM objects (Nodes, Elements, Conditions, Properties, ProcessInfo) are managed by shared pointers, and can hence have multiple owners. This mean in the practice that a given, say, Node may belong at the same time to multiple ModelParts.

A typical use case is that in which multiple physical problems should be solved on a single discretization of the problem. This is the case for example of the Fluid-Thermal problem that we will describe at the end of the tutorial. Kratos has a special Modeler named ConnectivityPreserveModeler that fills a modelpart by preserving the same connectivity as in the source model part while changing the element technology.

The resultant modelpart is a "free standing" root modelpart, completely independent of the original one. Nevertheless it shares:

• Pointers to the same nodes
• Same ProcessInfo
• Same Properties
• Same Tables as in the source modelpart.

The difference thus lays in the Element type being employed, which substitute in the new modelpart the element of the old modelpart with a new element implementing the desired physics.

The usage of the modeler is as follows:

     modeler = KratosMultiphysics.ConnectivityPreserveModeler()
     modeler.GenerateModelPart(self.main_model_part, self.thermal_model_part, "Element2D3N", "Condition2D2N")