Specify the Physics Behavior

Specify the physics behavior of the water flowing through the heat exchanger.

The physics behavior of fluid flow includes the effects of various environmental conditions on a fluid, as well as the innate physics behaviors of the fluid itself. For example, you can specify the impact of radiation, gravity, and heat on fluid flow. You can also specify if a fluid is compressible or incompressible.

In this example, you specify a particular turbulence model theory for the water flowing through the heat exchanger. There are a number of environmental effects that you can consider, but you ignore these effects for simplicity purposes. Afterward, you define a steady-state step to simulate stable, time-insensitive flow.

  1. From the Physics section of the Assistant, click Physics Behavior .
  2. Select Enable thermal effects to include the effects of heat energy in your flow simulation.
  3. From the Turbulence model options, select Realizable k-ε.

    The realizable k-ε turbulence model is appropriate for internal fluid flow scenarios like this example; other available models are suitable for external fluid flow scenarios.

  4. Click OK.
    When you define the physics behavior, the app automatically generates initial conditions with default settings. These initial conditions are located under the Scenario node in the tree.
  5. From the Physics section of the Assistant, click Steady State Step .
  6. Enter 500 as the Maximum iterations.
  7. Expand the Stopping criteria section, and define the stopping criteria.
    1. Under Error Thresholds, clear all of the check boxes.

      Selecting multiple stopping criteria might result in additional iterations as the solvers attempt to satisfy all of them. For this example, you clear the error thresholds criteria to support faster convergence. Applying only residual thresholds is also a common method for ensuring accurate results at the convergence point.

    2. Under Residual Thresholds, enter 0.01 for each Threshold.
  8. Expand the appropriate sections, and enter the following values for the Under relaxation factor:
    SectionValue
    Pressure Equation Controls 0.2
    Momentum Equation Controls 0.8
    Turbulence Equation Controls 0.8
    Energy Equation Controls 0.95
  9. Click OK.