## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### How to calculate the turbulence dissipation under the SAS-SST model in fluent?

• ztjia
Subscriber

when I use the SAS-SSTÂ  model, I do not understand the epsilon(turbulence/turbulent dissipation rate epsilon). Does the "epsilon" represent the turbulent dissipation rate in SAS-SST model? I know that SAS-SST model can tranfer to the LES-like mode in the unsteady flow, so is the turbulent dissipation rate in SAS-SST model calculated by " effective viscosity*strain rate*strain rate"? hoe you can help me, thank you, waiting for your reply. Also, how to calculate the dissipation rate in the SBES model (k-omega SST)?

• Essence
Ansys Employee

Yes, epsilon is the turbulent dissipation rate. Please refer to the Ansys guide link:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/flu_th/x1-1810005.20.2.html

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/flu_th/flu_th_sec_turb_scales_SBES.html?q=sbes

• ztjia
Subscriber

sorry,the link I can not open

• ztjia
Subscriber

sorry, I can not open the link?is there any problem?

• Rob
Ansys Employee

Click on Help in Fluent & paste the above into the browser that opens. Documentation is password protected but the solvers have a token/cookie/biscuit to bypass that step.Â

• ztjia
Subscriber

thanks for your reply. there still are some questions. for example, when I use SBES model based on the k-omega SST, how to calculate the subgrid viscosity? does the effective viscosity in fluent(Turbulence variable) include the subgrid viscosity? and under the SBES model, does S(strain rate tensor) represent the instantaneous velocity?