[Josh]

Good day, all -

The CFX documentation claims that symmetry and periodicity conditions are either impossible or impractical for SAS-SST, DES, and LES simulations since the asymmetrical, 3D turbulent structures must be resolved. Furthermore, the geometry of interest must be 3D and be refined in the spanwise direction in order to sufficiently capture, at the very least, the largest turbulent structures.

Despite this, I have read countless papers from DES and LES experts that have performed 2D or quasi-3D (i.e., a small span with minimal refinement, such as an airfoil of 0.1*chord span with 4 spanwise nodes) simulations and obtained excellent results.

1) Can the SAS-SST, DES, and LES models be used for some 2D simulations, such as low Reynolds number flow over an airfoil?

2) Can quasi-3D simulations be effective in some cases?

3) If a 3D simulation is required for the case of an airfoil in low Re flow (for example), does the airfoil have to stand alone (i.e., have a finite span that doesn't touch the sidewalls) or can it extend to the sidewalls and include a periodic condition?

4) CFX documentation notes that the SAS-SST model follows "most" of the setup guidelines of the DES model (e.g., y+ < 1). However, are there some guidelines it doesn't follow? For example, DES is susceptible to grid-induced separation but SAS is not.

Thanks for any and all help. I am very interested in the SAS-SST model but our computational resources are limited. I'm just wondering if the guidelines are as stringent for SAS as they are for DES. I can run a 3D simulation, but I'd prefer minimal spanwise resolution, if possible.