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:

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

Default model coefficients🔗

Initialisation🔗

Usage🔗

The model is specified using:

LES
{
    turbulence      on;
    LESModel        SpalartAllmarasDDES;
}

Boundary conditions🔗

Inlet

• fixedValue

Outlet

• Constrained outlet

Walls

• wall functions

Further information🔗

Source code:

• Foam::LESModels::SpalartAllmarasDDES

References:

• Spalart et al. [68]