Turbulent parameters in inlet CFD
 

Hi guys, i'm trying to simulate the aerodynamics of a kart with airfoil on windtunnel with Vento CFD. Can some of you help me with the choice of the turbulent parameters on inlet? The parameters are: eddy viscosity ratio and turbulent intensity.
I chose the Turbulent intensity at 1%. Is it a good approximation?
Which value can i use for eddy viscosity ratio?
Thanks :)

1-2% is a very reasonable turbulence intensity for a clean wind tunnel.


Defaults for viscosity ratio is usually set to 10 or a similarly low number, which corresponds to no turbulence in the inlet.


Probably the most practical way is to estimate the turbulent length scale. These would be proportional to some geometric length scale of the features in the wind tunnel. For example, the duct width/height or the size of the wire mesh of a nearby flow conditioner or rods in turbulence grid generator if you are intentionally generating turbulence. I generally use turbulence intensity and length scale because that's what you measure if you do the experiment yourself. But also because turbulence intensity is quite scalable to different conditions and the length scale I can guestimate quickly because I know exactly what the dimensions of the domain are because I just meshed it. Turbulence viscosity ratio I know only two numbers: 10 (which is really 0 except you shouldn't use 0) and 10 000 (which is really infinity except you can't use infinity).

Thank you so much, your answer was very helpfull!