12.13.18 Customizing the Turbulent Prandtl and Schmidt Numbers

If you are using the standard or realizable $k$- $\epsilon$ model or the standard $k$- $\omega$ model, a user-defined function can be used to customize the turbulent Prandtl and Schmidt numbers. This option will allow you to calculate $\sigma_k$ and either $\sigma_{\epsilon}$ or $\sigma_{\omega}$ (depending on the choice of either $k$- $\epsilon$ or $k$- $\omega$ model) by using a UDF. You will also be able to calculate the value of the energy turbulent Prandtl number (Pr $_t$ in this equation in the separate Theory Guide)and the turbulent Prandtl number at the wall (Pr $_t$ in this equation in the separate Theory Guide) in this way. More information about user-defined functions can be found in the separate UDF Manual.

In the Viscous Model dialog box, under User-Defined Functions, select the appropriate user-defined function from the drop-down lists under Prandtl and Schmidt Numbers. Options include: TKE Prandtl Number, TDR Prandtl Number ( $k$- $\epsilon$ models only), SDR Prandtl Number ( $k$- $\omega$ model only), Energy Prandtl Number, Wall Prandtl Number, and Turbulent Schmidt Number.