Guidelines for Solving Multiphysics Problems
Multiphysics Models
Unless the model contains a multiphysics node that defines a coupling between a Heat Transfer interface and another interface (see
Multiphysics Couplings
below), each physics interface defines default solver settings that are merged.
The Heat Transfer interfaces always define a dedicated segregated group that uses a linear solver optimized for the heat transfer equations. For strongly coupled models, it may be efficient to merge two (or more) segregated steps. In this case, a unique linear solver must be chosen for the fully coupled solver or the new segregated group.
Time-dependent settings from different physics interfaces may compete. When the different settings are merged the strictest one is kept.
Multiphysics Couplings
When a Heat Transfer interface is coupled with another physics interface through a multiphysics coupling feature, additional predefined default settings are loaded. The next two paragraphs describes the subtleties of the Nonisothermal Flow and Joule Heating interfaces.
Nonisothermal Flow
The
Nonisothermal Flow
multiphysics coupling controls the solver settings for the flow and the temperature dependent variables.
When it assumes a weak coupling between the flow and the heat interfaces (typically no Volume Force feature in the flow interface), the default solver contains dedicated segregated groups for heat and flow dependent variables. Each uses the default linear solver of the corresponding interface, except that the presmoother and postsmoother in the GMRES iterative solver switches from SOR to SCGS.
When a strong coupling is assumed (at least one Volume Force feature in the flow interface), the default solver merges the temperature, pressure, and velocity. In this case, the linear solver corresponds to the default linear solver of the flow interface. The Jacobian is updated once per time step.
Joule Heating
By default, the Joule Heating multiphysics interface solves the temperature and the electric potential in segregated steps.