atmLengthScaleTurbSource

Table of Contents

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 [m2/s3]
omega     | Specific dissipation rate                 [1/s]

Required fields, either of the below: 

epsilon   | Turbulent kinetic energy dissipation rate [m2/s3]
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 ([3], 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 ([61], 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 ([36], Eq. 3.34):

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

Mixing-length scale estimation ([36], 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:

Further information

Tutorials

Source code

History

  • Introduced in version v2006