OpenFOAM Documentation - atmLengthScaleTurbSource

Properties🔗

The atmLengthScaleTurbSource applies sources on either epsilon or omega to correct mixing-length scale estimations for atmospheric boundary layer modelling.
The atmLengthScaleTurbSource can be applied on epsilon or omega based RAS turbulence models.
The atmLengthScaleTurbSource inherits the traits of the fvOption, and cellSetOption.

Corrections applied to either of the below, if exist:

epsilon: Turbulent kinetic energy dissipation rate [m$^2$/s$^3$]
omega: Specific dissipation rate [1/s]

Required fields, either of the below:

epsilon: Turbulent kinetic energy dissipation rate [m$^2$/s$^3$]
omega: Specific dissipation rate [1/s]

Model equations🔗

Turbulent kinetic energy dissipation rate🔗

The model expression for epsilon:

\[S_p = \alpha \rho C_1^* \frac{G_o}{\nu} C_\mu k_o\]

with ([4], Eq. 16 wherein the exponentiation n is not present. n is an ad-hoc implementation):

\[C_1^* = (C_2 - C_1) \left( \frac{L}{L_{max}} \right)^n\]

Mixing-length scale estimation ([59], Eq. 10.37 & p. 374):

\[L = C_\mu^{3/4} \frac{k_o^{3/2}}{\epsilon_o}\]

Specific dissipation rate🔗

The model expression for omega:

\[S_p = \alpha \rho \gamma^* \frac{G_o}{\nu}\]

with ([33], Eq. 3.34):

\[\gamma^* = \left( \gamma - \beta \right) \left( \frac{L}{L_{max}} \right)^n\]

Mixing-length scale estimation ([33], Eq. 3.20):

\[L = \frac{\sqrt{k}}{C_\mu^{1/4} \omega_o}\]

Where:

$S_p$: Source term without boundary conditions
$\epsilon_o$: Previous-iteration epsilon [m2/s3]
$\omega_o$: Previous-iteration omega [1/s]
$k_o$: Previous-iteration k [m2/s2]
$G_o$: Previous-iteration k-production contribution [m2/s3]
$C_1$: Model constant (epsilon-based models) [-]
$C_2$: Model constant (epsilon-based models) [-]
$C_1^*$: Modified model constant field (epsilon-based models) [-]
$C_\mu$: Empirical model constant [-]
$\gamma$: Model constant (omega-based models) [-]
$\beta$: Model constant (omega-based models) [-]
$\gamma^*$: Modified model constant field (omega-based models) [-]
$\nu$: Kinematic viscosity of fluid [m2/s]
$L$: Mixing-length scale [m]
$L_{max}$: Maximum mixing-length scale [m]
$\alpha$: Phase fraction in multiphase computations, otherwise equals to 1
$\rho$: Fluid density in compressible computations, otherwise equals to 1

Usage🔗

Example of the fvOptions specification using constant/fvOptions file:

atmLengthScaleTurbSource1
{
    // Mandatory entries (unmodifiable)
    type                  atmLengthScaleTurbSource;

    atmLengthScaleTurbSourceCoeffs
    {
        // Mandatory (inherited) entries (unmodifiable)
        selectionMode    all;

        // Optional entries (unmodifiable)
        rho              rho;
        Lmax             41.575;
        n                3.0;
    }

    // Optional (inherited) entries
    ...
}

where the entries mean:

Property	Description	Type	Required	Default
type	Type name: atmLengthScaleTurbSource	word	yes	-
rho	Name of density field	word	no	rho
Lmax	Maximum mixing-length scale	scalar	no	41.575
n	Mixing-length scale exponent	scalar	no	3.0

The inherited entries are elaborated in:

fvOption
- cellSetOption

Further information🔗

Tutorials

Source code

$FOAM_SRC/atmosphericModels/fvOptions/atmLengthScaleTurbSource

History:

Introduced in version v2006

Open∇FOAM

atmLengthScaleTurbSource