kLowReWallFunction

Table of Contents

Note
Under construction - please check again later

Properties

  • The kLowReWallFunction boundary condition provides a wall constraint on the turbulent kinetic energy, i.e. k, for low- and high-Reynolds number turbulence models.
  • The kLowReWallFunction condition inherits the traits of the fixedValue boundary condition.

Required fields: 

k    | Turbulent kinetic energy    [m2/s2]

Model equations

The model expressions for k for viscous and inertial sublayers are switched in a stepwise manner:

\[ k = \max(k_{log} u_\tau^2, \zeta) \qquad if \quad y^+ > y^+_{lam} \]

\[ k = \max(k_{vis} u_\tau^2, \zeta) \qquad if \quad y^+ <= y^+_{lam} \]

with

\[ k_{log} = \frac{\ln (y^+) C_k}{\kappa} + B_k \]

\[ k = \frac{2400 C_f}{C_{eps2}^2} \]

\[ y^+ = \frac{u_\tau y}{\nu_w} \]

\[ u_\tau = C_\mu^{1/4} \sqrt{k} \]

\[ C_f = \frac{1}{(y^+ + C)^2} + \frac{2 y^+}{C^3} - \frac{1}{C^2} \]

where

\( k \) = Turbulent kinetic energy [m2/s2]
\( k_{vis} \) = k prediction in the viscous sublayer
\( k_{log} \) = k prediction in the inertial sublayer
\( y \) = Wall-normal height [m]
\( y^+ \) = Estimated wall-normal height of the cell centre in wall units
\( y^+_{lam} \) = Estimated intersection of the viscous and inertial sublayers in wall units
\( u_\tau \) = Friction velocity [m/s]
\( \zeta \) = Small value to prevent floating point exceptions
\( C_\mu \) = Empirical model constant [-]
\( \nu_w \) = Kinematic viscosity of fluid near wall [m2/s]

Usage

Example of the boundary condition specification: 

<patchName>
{
    // Mandatory entries (unmodifiable)
    type            kLowReWallFunction;

    // Optional entries (unmodifiable)
    Ceps2           1.9;
    Ck              -0.416;
    Bk              8.366;
    C               11.0;

    // Optional (inherited) entries
    ...
}

where the entries mean:

Property Description Type Required Default
type Type name: kLowReWallFunction word yes -
Ceps2 Model coefficient scalar no 1.9
Ck Model coefficient scalar no -0.416
Bk Model coefficient scalar no 8.366
C Model coefficient scalar no 11.0

The inherited entries are elaborated in:

  • fixedValueFvPatchField
  • nutWallFunctionFvPatchScalarField

Notes on entries

  • The coefficients Cmu, kappa, and E are obtained from the specified nutWallFunction in order to ensure that each patch possesses the same set of values for these coefficients.

Further information

Source code