Tools

OpenFOAM Turbulence Calculator

Calculate k, epsilon, omega, nut, Reynolds number, and first-cell height for OpenFOAM

What does this calculator do?

This calculator generates typical starting values and boundary conditions for OpenFOAM RANS models such as kEpsilon, kOmega, and kOmegaSST. It calculates Re, turbulence intensity I, turbulent kinetic energy k, dissipation epsilon, specific dissipation omega, turbulent viscosity nut, and first-cell height for a target y+.

Input Values

1. Model
for turbulenceProperties
ideal gas for air
kg/m3
m2/s
2. Inlet / Boundary Conditions
boundary condition for 0/U
for k, epsilon, omega
3. Geometry and Velocity
m/s
m, e.g. hydraulic diameter
can set L automatically
4. Turbulence Values
%; empty/0 = estimated from Re
m; 0 = 0.07 * L
1 wall-resolved, 30-100 wall functions
5. Wall Friction / Roughness
for u_tau and first-cell height
Note: These values are good starting values for typical RANS simulations. For final simulations, check boundary conditions, wall treatment, mesh quality, and resulting y+.
Reynolds
-
Re [-]
Intensity
-
I [%]
Length scale
-
l [m]
k
-
m2/s2
epsilon
-
m2/s3
omega
-
1/s
nut
-
m2/s
first cell
-
m

Boundary Layer / First Cell Height

typically 5-12 for RANS
typically 1.15-1.30
orientation only
y+ 1
-
m
y+ 30
-
m
y+ 100
-
m
Layer thickness
-
m
Advice is calculated from model, y+, and first-cell height.

OpenFOAM Code


        
        
        
        
        
    


    

        
Formula Reference

        

            Re = U * L / nu

            I = 0.16 * Re^(-1/8) if no intensity is specified

            k = 1.5 * (U * I)^2

            epsilon = Cmu^(3/4) * k^(3/2) / l

            omega = sqrt(k) / (Cmu^(1/4) * l)

            nut = Cmu * k^2 / epsilon

            Cf = 0.058 * Re^(-0.2), u_tau = sqrt(0.5 * U^2 * Cf), y = y+ * nu / u_tau


            Default: Cmu = 0.09, l = 0.07 * L