nutURoughWallFunction
boundary condition provides a wall constraint on the turbulent viscosity, i.e. nut
, based on velocity i.e. U
, for low- and high-Reynolds number turbulence models for rough walls.nutURoughWallFunction
condition inherits the traits of the nutWallFunction boundary condition.Required fields:
nut | Turbulent viscosity [m2/s]
The model expressions:
\[ \nu_t = 0 \qquad if \quad y^+ <= y^+_{lam} \]
\[ \nu_t = \nu_w \left( \frac{(y^+)^2}{Re} -1 \right) \qquad if \quad y^+ > y^+_{lam} \]
with
\[ Re = \frac{u_p y}{\nu_w} + \zeta \]
where
\( \nu_t \) | = | Turbulent viscosity [m2/s] |
\( Re \) | = | Reynolds number [-] |
\( \nu_w \) | = | Kinematic viscosity of fluid near wall [m2/s] |
\( y^+ \) | = | Estimated wall-normal height of the cell centre in wall units |
\( \zeta \) | = | Small value to prevent floating point exceptions |
Example of the boundary condition specification:
<patchName> { // Mandatory entries (unmodifiable) type nutURoughWallFunction; roughnessHeight 1e-5; roughnessConstant 0.5; roughnessFactor 1; // Optional entries (unmodifiable) maxIter 10; tolerance 0.0001; // Optional (inherited) entries ... }
where the entries mean:
Property | Description | Type | Required | Default |
---|---|---|---|---|
type | Type name: nutURoughWallFunction | word | yes | - |
roughnessHeight | Roughness height | scalar | yes | - |
roughnessConstant | Roughness constant | scalar | yes | - |
roughnessFactor | Scaling factor | scalar | yes | - |
maxIter | Number of Newton-Raphson iterations | label | no | 10 |
tolerance | Convergence tolerance | scalar | no | 0.0001 |
The inherited entries are elaborated in:
correctNut()
(called through turbulence->validate
) returns a slightly different value every time it is called. See nutUSpaldingWallFunction.Foam::nutURoughWallFunctionFvPatchScalarField::calcYPlus
function for the details on how \(y^+\) is computed.Source code