Learning Forum

[Aristia Philippou]

Hello,

i was wondering if it is possible to disclose information on the transition mechanisms from RANS to LES model when running an SAS case. 

I understand that SAS transitions between RANS and LES based on local flow conditions, and it blends the turbulence modelling behaviour continuously across a range of length scales. I assume the transition behavior in the Scale-Adaptive SST model is primarily determined by internal algorithms and criteria that are not accessible or modifiable through the Fluent text command interface. The transition is based on some predefined criteria like, turbulent kinetic energy (TKE), length scales, and other flow variables, which are implemented within the Scale-Adaptive SST model. If it is not possible to control these criteria is it possible you could share the default values of these criteria to better understand when the transitioning takes place?

Thank you.

[Federico]

Hello,

you can find more detailed information in the Fluent Theory Guide: 4.11.2. Transport Equations for the SST-SAS Model (ansys.com)

[Aristia Philippou]

Hi,

Thank you, i had a look into the Theory Guide and while it provides information on the transport equations it doesn't necessarily explain the blending of the turbulence modelling.

[Federico]

It is not explicitely explained in the Theory Guide, but the papers on which these models are based on are listed therein.