atmNutWallFunction boundary condition 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.atmNutWallFunction condition inherits the traits of the nutkWallFunction boundary condition.Required fields:
nut | Turbulent viscosity [m2/s] k | Turbulent kinetic energy [m2/s2]
The boundary condition expression is (([63], Eq. 6-7), ([71], Eq. 7), ([80], Eq. 25)):
\[ \nu_{t_w} = max(\nu_{t_w}^\prime, 0) \]
with
\[ \nu_{t_w}^\prime = \frac{ \tau_w y}{max( u_p, \zeta )} - \nu_w \]
\[ \tau_w = {u^*_{u_p}} {u^*_k} \]
\[ u^*_{u_p} = \frac{\kappa u_p }{\ln \left( max (E^\prime, 1 + \zeta) \right)} \]
\[ E^\prime = \frac{y + z_0}{z_0 + z_{0_{min}} } \]
\[ u^*_k = C_{\mu}^{1/4} \sqrt{k} \]
where
| \( \tau_w \) | = | Characteristic wall shear stress [m2/s2] |
| \( u^*_{u_p} \) | = | Local friction velocity based on near-ground velocity [m/s] |
| \( u^*_k \) | = | Local friction velocity based on near-ground k [m/s] |
| \( \kappa \) | = | von Kármán constant [-] |
| \( u_p \) | = | Magnitude of near-ground velocity field [m/s] |
| \( y \) | = | Ground-normal coordinate [m] |
| \( z_0 \) | = | Surface roughness length [m] |
| \( z_{0_{min}} \) | = | Minimum surface roughness length [m] |
| \( C_\mu \) | = | Empirical model constant [-] |
| \( k \) | = | Turbulent kinetic energy [m2/s2] |
| \( \zeta \) | = | Small value to prevent floating point exceptions [-] |
Example of the boundary condition specification:
<patchName>
{
// Mandatory entries (unmodifiable)
type atmNutWallFunction;
z0Min 0.001;
// Mandatory entries (runtime modifiable)
z0 uniform 0.001;
// Optional (inherited) entries
kappa 0.41;
}
where the entries mean:
| Property | Description | Type | Required | Default |
|---|---|---|---|---|
| type | Type name: atmNutWallFunction | word | yes | - |
| z0 | Surface roughness length [m] | PatchFunction1<scalar> | yes | - |
| z0Min | Minimum surface roughness length [m] | scalar | yes | - |
| kappa | von Kármán constant | scalar | no | 0.41 |
The inherited entries are elaborated in:
Source code
History
1.9.5