Running Unsteady with Curvature Correction

The accuracy of the simulation is improved by activating the curvature correction term of the k-omega turbulence model. However, this improved accuracy means that an unsteady solution must be adopted in order to achieve adequate convergence.

Modify the model selection within the physics continuum and activate curvature correction:
  1. Right-click the Continua > Physics 1 node and choose Select Models.
  2. Within the physics model selection dialog, make the following changes:
    1. From the Enabled group box, deactivate Steady.
    2. From the Time group box, activate Implicit Unsteady.
    3. Click Close.
  3. Select the Physics 1 > Models > SST (Mentor) K-Omega node and set Curvature Correction to On.
Several changes are required for the solver settings and stopping criteria:
  1. Edit the Solvers node and set the following properties:
    NodePropertyValue
    Implicit UnsteadyTime-Step5.0E-4 s
    Segregated Flow > VelocityUnder-Relaxation Factor0.9
    Segregated Flow > PressureUnder-Relaxation Factor0.4
  2. Edit the Stopping Criteria node and set the following properties:
    NodePropertyValue
    Maximum StepsEnabledDeactivated
    Maximum Inner IterationsMaximum Inner Iterations8
    Maximum Physical TimeMaximum Physical Time0.5 s
  3. Select the Solution Histories > cycloneFlowSolution > Update node and set Trigger to Time Step.
You can now run the solver again using the steady solution as the initial state:
  1. In the Solution toolbar, click (Run).
    The solver runs for another 8000 iterations (given 8 inner iterations per time-step).
  2. Save the simulation. This action ensures that the simulation history file is complete.
  3. To compare the final solution from the unsteady run with the solution from the steady run:
    1. Select the Solution Views > cycloneFlowSolution node and set State Name to Steady.
    2. Select the Scenes > Scalar Scene 1 > Scalar 1 > Color Bar node and set:
      • Orientation to Vertical
      • Position to [0.2, 0.6].
    3. Within the Scenes node, right-click Scalar Scene 1 and select Copy.
    4. Right-click the Scenes node and select Paste.
    5. Rename the copy to Steady Solution.
    6. Right-click the Steady Solution node and select Apply Representation to Displayers > cycloneFlowSolution.
    7. Multi-select the Steady Solution and Scalar Scene 1 nodes. Right-click one node and select Linked View.
    8. Right-click the Layout Views node and select New Layout View > 1 Left, 1 Right
    9. From the simulation tree, drag the Scenes > Steady Solution node and drop it into the left panel of the Layout View in the graphics window.
    10. Similarly, drag the Scenes > Scalar Scene 1 node and drop it into the right panel of the Layout View.

    You can now compare the final unsteady solution on the right with the initial steady solution on the left. The addition of curvature correction has sharpened the center core of the swirling flow and defined its shape.