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


  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.

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