Setting Stopping Criteria and Solver Parameters

Set the appropriate solver parameters and stopping criteria for the simulation.

In this case, the volume fraction field is expected to be sharper than that of a conventional continuous-dispersed flow. To improve convergence, use the Flex Cycle in the Volume Fraction AMG Linear solver, rather than the default V Cycle.

Modify the under-relaxation factors for the solvers to aid solution convergence. As you are solving an unsteady problem, it is necessary to specify the time-step size and the elapsed simulation time. This calculation runs for a maximum physical time of 8.0 seconds with a time-step size of 0.01 s.

To set the solver parameters and stopping criteria:

  1. Edit the Solvers node and set the following properties:
    Node Property Setting
    Volume Fraction > AMG Linear Solver Cycle Type Flex Cycle
    Implicit Unsteady Time-Step 0.01 s
    Segregated EMP Flow > Phase Coupled Velocity Implicit Under-Relaxation Factor 0.1
    Explicit Under-Relaxation Factor 0.5
    Segregated EMP Flow > Pressure Under-Relaxation Factor 0.1
    Volume Fraction Implicit Under-Relaxation Factor 0.2
    Explicit Under-Relaxation Factor 0.5
    K-Omega Turbulence Under-Relaxation Factor 0.2
    K-Omega Turbulent Viscosity Under-Relaxation Factor 0.2
    Maximum Ratio 1.0E8
  2. Edit the Stopping Criteria node and set the following properties:
    Node Property Setting
    Maximum Inner Iterations Maximum Inner Iterations 25
    Maximum Physical Time Maximum Physical Time 8.0 s
    Maximum Steps Enabled Deactivated
  3. Save the simulation.