Defining Active Multispecies in Fluid Physics

You can enable active multispecies to simulate the bulk flow using all of the components in the analysis. When you select active multispecies, you can also simulate the evaporation and condensation of water on surfaces, also known as defog and demist.

The defog and demist functionality does not support phase changes, so all of the materials in the multispecies section must be gaseous, and exactly one species must be water vapor. You indicate manually which species is the water vapor; the app does not perform any checks to validate your choice.

This task shows you how to:

See Also
About Active and Passive Multispecies in a Flow Simulation

Specify Active Multispecies

Before you begin: You must have a multispecies section defined for the model.
  1. From the Procedures section of the action bar, click Physics .
  2. From the Multispecies model options, select Active.
  3. Click OK.

Specify Active Multispecies with Defog and Demist on a Wall Boundary

Before you begin: You must have a multispecies section defined for the model, where each species is a material in gas phase and one of the species is water vapor.
  1. From the Procedures section of the action bar, click Physics .
  2. From the Multispecies model options, select Active.
  3. Select Enable defog and demist model.
  4. From the Tag material options, select the water vapor species and define its Liquid density.
  5. Click OK.

Once you enable the defog and demist model in the fluid physics, you can activate it for individual wall boundaries as well. For more information, see Defining the Multispecies Conditions at a Wall.