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Properties

  • The atmAmbientTurbSource applies sources on k and either epsilon or omega to prevent them dropping below a specified ambient value for atmospheric boundary layer modelling.
  • Such adjustment reportedly increases numerical stability for very stable atmospheric stability conditions, and prevents nonphysical oscillations in regions of low shear at higher altitudes.
  • The atmAmbientTurbSource can be applied on epsilon or omega based RAS turbulence models.
  • The atmAmbientTurbSource inherits the traits of the fvOption, and cellSetOption.

Corrections applied to:

k
Turbulent kinetic energy [m\(^2\)/s\(^2\)]

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:

k
Turbulent kinetic energy [m\(^2\)/s\(^2\)]

and either of:

epsilon
Turbulent kinetic energy dissipation rate [m\(^2\)/s\(^3\)]
omega
Specific dissipation rate [1/s]

Model equations

The model expression for epsilon (Heuristically derived from [60], Eq. 4, rhs-term:5):

\[S_p = \alpha \rho C_2 \frac{\epsilon_{amb}^2}{k_{amb} \epsilon_o} \epsilon\]

The model expression for omega ([60], Eq. 4, rhs-term:5):

\[S_p = \alpha \rho C_\mu \beta \frac{\omega^2_{amb}}{\omega_o} \omega\]

The model expression for k when epsilon is available (Heuristically derived from ([60], Eq. 3, rhs-term:4):

\[S_p = \alpha \rho \frac{\epsilon_{amb}}{k_o} k\]

The model expression for k when omega is available ([60], Eq. 3, rhs-term:4):

\[S_p = \alpha \rho C_\mu \frac{\omega_{amb} k_{amb}}{k_o} k\]

Where:

\(S_p\)
Source term without boundary conditions
\(\epsilon\)
Turbulent kinetic energy dissipation rate (Current iteration) [m2/s3]
\(\omega\)
Specific dissipation rate (Current iteration) [1/s]
\(k\)
Turbulent kinetic energy (Current iteration) [m2/s2]
\(\epsilon_{amb}\)
Ambient epsilon value [m2/s3]
\(\omega_{amb}\)
Ambient omega value [1/s]
\(k_{amb}\)
Ambient k value [m2/s2]
\(\epsilon_o\)
Previous-iteration epsilon [m2/s3]
\(\omega_o\)
Previous-iteration omega [1/s]
\(k_o\)
Previous-iteration k [m2/s2]
\(C_2\)
Model constant [-]
\(C_\mu\)
Empirical model constant [-]
\(\beta\)
Model constant [-]
\(\alpha\)
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:

atmAmbientTurbSource1
{
    // Mandatory entries (unmodifiable)
    type                  atmAmbientTurbSource;

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

        // Mandatory entries (unmodifiable)
        kAmb              0.0;

        // Optional entries (unmodifiable)
        rho               rho;
        epsilonAmb        0.0;
        omegaAmb          0.0;
    }

    // Optional (inherited) entries
    ...
}

where the entries mean:

Property Description Type Required Default
type Type name: atmAmbientTurbSource word yes -
kAmb Ambient value for k scalar yes -
rho Name of density field word no rho
epsilonAmb Ambient value for epsilon scalar no 0.0
omegaAmb Ambient value for omega scalar no 0.0

The inherited entries are elaborated in:

Further information

Tutorials

Source code

History:

  • Introduced in version v2006