Setting Up the Solvers and Running the Simulation

You run the simulation for a physical time of 0.4 s. The iterations per time-step stop when the relative change in residuals of the continuity equation is less than 2% or the maximum number of inner iterations of 15 is reached. To enhance the accuracy of the simulation, you set the temporal discretization of the implicit unsteady solver as well as those of the continuity equation and the energy equation to a second-order scheme. To speed up convergence per time-step, you increase the under-relaxation factors from their defaults.

For the time-step size, you set up the following step function:

Δ t = { 10 3 ;  if   t < 0.1 s 5 × 10 4 ;  if   0.1 t < 0.15 s 10 4 ;  if   t 0.15 s

To set up the solvers and run the simulation:
  1. Select the Solvers > Implicit Unsteady node and set the following properties:
    Property Setting
    Time-Step $Time < 0.10 ? 1e-3 : ($Time <0.15 ? 5e-4 : 1e-4)
    Temporal Discretization 2nd-order
  2. Right-click the Solvers > Implicit Unsteady > Stopping Criteria node and select New Monitor Criterion....
  3. In the Select Monitor dialog, select Continuity.
  4. Select the Stopping Criteria > Continuity Criterion node and set Criterion Option to Relative Change.
  5. Select the Continuity Criterion > Relative Change node and set Relative Change to 0.02.
  6. Edit the Solvers node and set the following properties:
    Node Property Setting
    Segregated Flow
    Velocity Under-Relaxation Factor 0.9
    Pressure Under-Relaxation Factor 0.7
    High-Accuracy Temporal Discretization Option Optimized 2nd-order (5)
    Segregated Energy Enable High-Accuracy Temporal Discretization On
    High-Accuracy Temporal Discretization Option Optimized 2nd-order (5)
  7. Edit the Stopping Criteria node and set the following properties:
    Node Property Setting
    Maximum Inner Iterations Maximum Inner Iterations 15
    Maximum Physical Time Maximum Physical Time 0.4 s
    Maximum Steps Enabled Off
  8. Select the Monitors > Pressure Monitor node and set Trigger to Time Step.
  9. Click (Run) to run the simulation.
  10. When the simulation is complete, save it.