Spalart-Allmaras Delayed Detached Eddy Simulation (DDES)

- Note
*Under construction*- please check again later

- One equation model based on a modified turbulence viscosity, \( \tilde{\nu} \)
- based on the Spalart-Allmaras DES model.

The model equations are the same as used by the DES variant of the model, with a different approximation for \( \tilde{d} \):

\[ \tilde{d} = \max \left[ L_{RAS} - f_d, \max (L_{RAS} - L_{LES}, 0) \right] \]

The RAS length scale is:

\[ L_{RAS} = y \]

and the LES length:

\[ L_{LES} = \Psi C_{DES} \Delta \]

The delay function is given by:

\[ f_d = 1 - \tanh \left[ \left( C_{d1} r_d \right)^{C_{d2}} \right] \]

Here, when \( f_d = 0 \) RAS is recovered, and when \( f_d = 1 \) the DES mode is recovered. The \( r_d \) parameter is given by:

\[ r_d = \min \left( \frac{\nu_{\mathit{eff}}}{\mag {\grad \u} \kappa^2 y^2}, 10\right) \]

The model is specified using:

LES { turbulence on; LESModel SpalartAllmarasDDES; }

Inlet

Outlet

Walls

- wall functions

Source code:

References:

*Spalart et al.*[74]

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