Defining a Transient Flow Step

You can define a transient flow step to perform a fluid dynamic analysis on a system over a given time period.

  1. From the Procedures section of the action bar, click Transient Step .
  2. Optional: Enter a descriptive Name.
  3. Enter a value for the Total time, which is the duration of the step.
  4. If you enabled solar radiation, enter a value for the Solar load recalculation interval, which is how often the radiation equation solver recalculates the solar load based on the sun's position.
  5. From the Time incrementation options, select one of the following:
    OptionDescription
    Automatic Continually adjusts the time increment size to satisfy the Courant-Friedrichs-Lewy (CFL) stability condition for advection.
    Fixed Increments the time by a fixed size that you specify.
  6. If you selected Automatic time incrementation, enter a value for the CFL number.

    Based on the CFL number you specify, the solver determines the stable time step.

  7. If you selected Fixed, specify the following:

    • The Fixed time increment, which is the duration of each time increment.
    • Optional: The Amplitude , which is the profile that controls the variation of the fixed time increment during the simulation.

  8. Expand the Time incrementation section to define additional time incrementation options.

    For more information about time incrementation, see Defining Time Incrementation Options.

  9. Optional: Specify the equation controls for each equation required by your transient flow step.

    For more information, see Equation Controls.

  10. Optional: Expand the Expert numerics controls section to specify the analysis behavior for disabling secondary diffusion and second-order advection.

    Disabling secondary diffusion and second-order advection can help the solver converge in situations when it might not otherwise; however, the solution might be less accurate.

    For more information, see Defining Expert Numerics Controls.

  11. Optional: Expand the Expert cycle controls section to freeze the flow field or energy field during simulation.

    Freezing the flow field or energy field deactivates the corresponding equation solvers, thereby saving simulation time.

    For more information, see Freezing the Flow Field and Energy Field.

  12. Optional: Select Enable particle modeling to simulate the motion of Lagrangian Particles in the fluid physics, then expand the Particle modeling parameters section to specify the type, material, and behavior for the particles.

    For more information, see Defining Particle Controls.

  13. Click OK.