DES type methods

DES (Detached Eddy Simulation)¹

The length scale in the destruction term of the SA turbulence model is modified:

• Instead of the wall normal distance, the length scale is now the minimum of the wall normal distance and a length parameter proportional to the local grid spacing.
• Δ is called the sub-grid scale
• The method requires careful grid generation

DDES (Delayed Detached Eddy Simulation)²

• Switching is the function of boundary layer thickness.
• The function
  

  is designed such that its value is zero inside the boundary layer.

• Imposes RANS within the boundary layer irrespective of the grid size.
• Unlike DES, the method is grid independent.

IDDES (Improved Delayed Detached Eddy Simulation)³

• Allows switching to LES within the boundary layer
• Creates WMLES formulation by matching the log layers between the RANS and outer LES region
• Uses blending and shielding functions to match logarithmic layers

References

1. Spalart, P.R., Jou, W.H., Strelets, M., Allmaras, S.R., “Comments on the feasibility of LES for wings, and on a hybrid RANS/LES approach”, Proceedings of first AFOSR international conference on DND/LES, 1997.
2. Spalart, P.R., Deck, S., Shur, M.L., Squires, K.D., Strelets, M.K., Travin A., “A new version of detached-eddy simulation, resistant to ambiguous grid densities”, Theoretical Computational Fluid Dynamics 20, 181–195, 2006.
3. Shur, M.L., Spalart, P.R., Strelets, M.K., Travin, A.K., “A hybrid RANS-LES approach with delayed-DES and wall-modeled LES capabilities”, International Journal of Heat and Fluid Flow 29, 2008.