Description๐
The atmNutWallFunction
is a boundary condition that provides
a wall constraint on the turbulent viscosity (i.e. nut
) based on the
turbulent kinetic energy (i.e. k
) and velocity (i.e. U
) for atmospheric
boundary layer modelling.
The governing equation of the boundary condition:
\[\tau_w = {U^*_u} {U^*_k}\]with:
\[{U^*_u} = \frac{\kappa U_w}{ln(z_p / z_0)}\] \[{U^*_k} = C_{\mu}^{1/4} \sqrt{k}\]where:
Property | Description |
---|---|
\(\tau_w\) | Wall shear stress |
\(U^*_u\) | Local friction velocity based on near-ground velocity |
\(U^*_k\) | Local friction velocity based on near-ground k |
\(\kappa\) | von Karman constant |
\(U_w\) | Near-ground velocity |
\(z_p\) | Vertical coordinate |
\(z_0\) | Surface roughness length [m] |
\(C_mu\) | Empirical model constant |
\(k\) | Turbulent kinetic energy |
References
-
Theoretical expressions (tags:RH, SBJM, SM):
Richards, P. J., & Hoxey, R. P. (1993). Appropriate boundary conditions for computational wind engineering models using the k-ฮต turbulence model. In Computational Wind Engineering 1 (pp. 145-153). DOI:10.1016/B978-0-444-81688-7.50018-8
Sรธrensen, N. N., Bechmann, A., Johansen, J., Myllerup, L., Botha, P., Vinther, S., & Nielsen, B. S. (2007). Identification of severe wind conditions using a Reynolds Averaged Navier-Stokes solver. In Journal of Physics: Conference series (Vol. 75, No. 1, p. 012053). DOI:10.1088/1742-6596/75/1/012053
Sumner, J., & Masson, C. (2012). kโฮต simulations of the neutral atmospheric boundary layer: analysis and correction of discretization errors on practical grids. International journal for numerical methods in fluids, 70(6), 724-741. DOI:10.1002/fld.2709
Usage๐
The condition requires entries in both the boundary and field files.
Boundary file๐
<patchName>
{
type patch;
...
}
Field file๐
<patchName>
{
// Mandatory entries
type atmNutWallFunction;
z0Min <scalar>;
z0 <PatchFunction1<scalar>>;
// Inherited entries
...
}
where:
Property | Description | Type | Required | Default |
---|---|---|---|---|
type |
Type name: atmNutWallFunction
|
word | yes | - |
z0Min |
Minimum surface roughness length [m] | scalar | yes | - |
z0 |
Surface roughness length [m] | PatchFunction1<scalar> | yes | - |
The inherited entries are elaborated in:
- nutkWallFunctionFvPatchScalarField.H
- PatchFunction1.H
Further information๐
Tutorial:
- N/A
Source code:
API:
History:
- Introduced in version v2006