Multiphysics Stabilization Solver Reference

The Multiphysics Stabilization Solver allows you to set the stabilization method and convergence tolerance for the displacement at the wetted interface in FSI co-simulations. The Multiphysics Stabilization Solver is available in the solid simulation when all of the following requirements are met:

  • The internal continuum includes the Solid Stress model.
  • The external continuum includes the Implicit Coupling model.
  • You activate the Multiphysics Stabilization Solver property of the Simcenter STAR-CCM+ Co-Simulation solver.

You are advised to activate this solver for FSI co-simulations where the fluid and solid are strongly coupled.

Multiphysics Stabilization Solver Properties

Verbosity
Allows you to control the output level of Quasi-Newton data:
  • Low—displays minimal information in the Output window, including initialization of the fixed-point iteration and application of the Quasi-Newton method.
  • High—displays additional information, including clearing of the stored Quasi-Newton data and the number of the current fixed-point iteration.
Convergence Tolerance
Sets the tolerance by which to assess convergence of the coupled FSI solution. When the Interface Displacement residual is less than the specified tolerance, the solution is considered converged and the data stored for the Quasi-Newton data is reused in the next time-step. Otherwise, the stored data is cleared upon completion of the time-step.
Stabilization Method
Allows you to specify the method of stabilization applied to the solid simulation of the couplied FSI simulation. Currently only a Quasi-Newton Anderson Acceleration method is available. The Quasi-Newton Anderson Acceleration method has the following properties:
  • Under-Relaxation Factor—the under-relaxation value for the second inner iteration of the implicit coupling range.
  • Filtering parameter—allows you to filter out linearly-dependent increments of fixed-point residuals (see the term F k in Eqn. (4640)). If too many vectors are filtered, the solution may not converge, or it may converge slowly. However, if the linear dependencies are not filtered out, the numerical solution of the least-squares problem can become unstable. A value of 10E-6 is recommended for an initial run.
  • History size—allows you to set the maximum number of increments that approximate the Jacobian. Corresponds to the value m in Eqn. (4639).
  • Time Steps Reused—specifies the maximum number of time-steps Simcenter STAR-CCM+ reuses to accelerate the convergence of transient simulations, assuming that the fixed-point problems are closely related. A value of 5 is recommended for an initial run.
For more information, see Anderson Acceleration.
Temporary Storage Retained
When activated, Simcenter STAR-CCM+ retains the Interface Displacement Residual field data that the solver generates during an iteration. The Interface Displacement Residual becomes available as a field function during subsequent iterations.

Stopping Criteria

Interface Displacement Stopping Criteria
Uses the difference in converged displacement at the wetted interface from the Solid Stress Solver and the displacement received by the fluid simulation. Activated automatically by the Multiphysics Stabilization Solver. You are advised to:
  • Use a similar value for the Minimum Limit as the Convergence Tolerance of the Multiphysics Stabilization Solver. Ensure the Normalization Option of the Interface Displacement monitor is set to Off.
  • Enable Stop Inner Iterations in the properties.

Monitors

Interface Displacement
The difference in displacement from the simulation if the partner simulation is finished.