Hi; In a water tunnel test section , for example, what turbulent intensity and turbulent viscosity should I set for inlet boundary condition.

Hey, It depends on your system. For my part I usually use the Hydraulic diameter boundary condition associate with the turbulent intensity. The turbulent intensity represent the Fluctuation capacity of your system compared to the velocity value. You need to know that between 1% to 10% there are strictly no differences in results. Bigger values can modify your final results in some cases.

Hope this can help, thomas

Yes I agree. Use Dh and I. If you don't know the I value, 5% would not be a bad guess. Some low intensity tunnels can get as low as .05%. If you have a screen or obstruction, you may have 10% or greater. For Dh, you know the tunnel height you are modelling, so you have that answer.

I: Turbulent Intensity Dh: Hydraulic Diameter

Hey, Just another quick note about using an hydraulic diameter inlet BC. Using the k-eps turbulent model this method can give you very low k-eps intial condition ( in case you intitialize your domain using 'inlet condition' ). Therefore you should ajust both values more correctly. It is generally admitted k around 0.0001 and eps 0.001 ... but theer again it can depend on your case.

bye, thomas