Note that the Turbulent Mixing node is only available for some product add-ons. See details: http://www.comsol.com/products/specifications/.

This subnode is available from the context menu (right-click the Transport Properties parent node) as well as from the Physics toolbar, Attributes menu, if Convection is selected as a transport mechanism. Use this node to account for the turbulent mixing caused by the eddy diffusivity. An example is when the specified velocity field corresponds to a RANS solution.

Some physics interfaces provide the turbulent kinematic viscosity, and these appear as options in the Turbulent kinematic viscosity νT list. The list always contains the User defined option where any value or expression can be entered.

The default Turbulent Schmidt number ScT is 0.71 (dimensionless).

See the section About Turbulent Mixing in the CFD Module User’s Guide (this link is available online or if you have the CFD Module documentation installed).