nut - \( ν_{t} \)

The entries for \( ν_{t} \) are type calculated because they come from ε and k to calculate the field. Instead in the wall, you specify a wall function for \( ν_{t} \), to modify the momentum equation for the cells adjacent to the wall. The modification is that OpenFoam® calculates wall shear stress from log-law for these cells and put it in their equations. OpenFoam® does not use log-law directly to obtain next-to-the-wall cell velocities but solves their equation in which the stress term is modified using log-law.

Turbulent viscosity wall functions

The choice of wall function model is specified through the turbulent viscosity field  \( ν_{t} \) in the 0/nut dictionary by the nutxxxxxx wall functions:

• nutWallFunction seems to be the most basic wall function without further requirements: high-Re wall-function based on k.

• nutkWallFunction standard for k-ε/k-ω, it calculates the turbulent viscosity in the first node point based on the logarithmic law based on the k value close to the wall

• nutUWallFunction: in comparison to nutkWallFunction it calculates the y⁺sup>+ yPlus value based on the velocity close to the wall

• nutUSpaldingWallFunction standard wall function for the Spallart Allmarras turbulence model, called nutSpalartAllmarasWallFunction, continuous wall-function which should cover the complete y⁺ range from O(1) to somewhere of O(10). Might be the best choice (together with low Re k-ε, k-ω, or SA, when y⁺ varies for different parts of the wall.

• nutLowReWallFunction (code comment: “Sets \( ν_{t} \) to zero and provides an access function to calculate y⁺.”):