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Spalart-Allmaras Delayed Detached Eddy Simulation (DDES)

Note
Under construction - please check again later

# Properties

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

# Model equations

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:

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

# Usage

The model is specified using:

LES
{
turbulence      on;
LESModel        SpalartAllmarasDDES;
}


# Boundary conditions

Inlet

Outlet

Walls

• wall functions

# Further information

Source code:

References:

• Spalart et al. [74]

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