When modeling elasticity in a solid or a flow problem, it is not typically necessary to use an evolution scheme because equations are usually linear. However, note that even if separate problems converge without evolution, some convergence problems could occur if the retrospective effect of the solid deformation on the flow domain is taken into account.
If you are encountering convergence difficulties, there are three ways to overcome them:
Check the deformation of the solid by selecting the no update of coordinate option in the Material data menu of the elastic sub-task.
If the difficulty is related to the deformation of the solid part, then it is recommended that you use an evolution scheme that decreases the value of the Young’s modulus (see Evolution for details).
An alternative solution is to use an evolution scheme on flow parameters (for example, flow rate or viscosity) that dominates the force produced by the fluid and applies it on the solid interface.
If deformations are dominated by dilatation, then it is recommended that you use an evolution scheme that increases the dilatation coefficient, or the difference between the temperature and the reference temperature.
For a large-scale problem, select the Decoupled computation of the moving surfaces option in the numerical parameters panel.
Decoupled computation of the moving surfaces
This option will iteratively compute the flow problem and the elastic sub-tasks. An advantage of utilizing this option is reduced memory consumption, but the convergence rate will be slower.