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
- 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.
- 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.
- 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.