atmNutUWallFunction boundary condition provides a wall constraint on the turbulent viscosity, i.e. nut, based on velocity, i.e. U, for atmospheric boundary layer modelling.atmNutUWallFunction condition inherits the traits of the nutUWallFunction boundary condition.Required fields:
nut | Turbulent viscosity [m2/s] U | Velocity [m/s]
The boundary condition expression is:
\[ \nu_{t_w} = \frac{(u^*)^2 y}{max( u_p , 10^{-6} )} - \nu_w \]
with
\[ u^* = \frac{ u_p \kappa}{\ln \left(max(E^\prime, 1 + 10^{-4}) \right)} \]
\[ E^\prime = \frac{y + z_0}{z_0 + 10^{-4} } \]
\[ u_p = | \u_p - (\u_p \cdot \vec{n}) \vec{n} | \]
where
| \( \nu_{t_w} \) | = | Turbulent viscosity [m2/s] |
| \( \nu_w \) | = | Kinematic viscosity of fluid in the wall cell [m2/s] |
| \( y \) | = | Ground-normal distance [m] |
| \( \kappa \) | = | von Kármán constant [-] |
| \( u^* \) | = | Friction velocity [m/s] |
| \( z_0 \) | = | Surface roughness length [m] |
| \( u_p \) | = | Magnitude of modified near-ground velocity field [m/s] |
| \( \vec{n} \) | = | Patch normal vector [m] |
Example of the boundary condition specification:
<patchName>
{
// Mandatory entries (unmodifiable)
type atmNutUWallFunction;
// Mandatory entries (runtime modifiable)
z0 uniform 0.001;
// Optional entries (unmodifiable)
boundNut true;
// Optional (inherited) entries
kappa 0.41;
}
where the entries mean:
| Property | Description | Type | Required | Default |
|---|---|---|---|---|
| type | Type name: atmNutUWallFunction | word | yes | - |
| z0 | Surface roughness length [m] | PatchFunction1<scalar> | yes | - |
| boundNut | Flag: zero-bound nut near wall | bool | no | false |
| kappa | von Kármán constant | scalar | no | 0.41 |
The inherited entries are elaborated in:
Source code
History
1.9.5