What are the most common value to use for the turbulent intensity and length scale when using K-e model in a cleanroom air flow. The air speed is at 0.4m/s. It is running in 2-dimension and the height is at about 3m and width at 4.6m.What boundary codition should I be using, currently I am using velocity-inlet as my inlet and pressure-outlet as my outlet. My outlet length is about 0.28m and inlet at 1.5m, and it is located at left hand corner of the ceiling and right hand corner of the ceiling respectively. The flow should be a u-shape. But my data in the fluent for the velocity do not match with the physical experiment data. Please tell my problems. Need help desperately. I am working on my final year project.Especially the velocity data does not match. Or is there other model that I should try??

Do you have enough computational cells in you model to simulate the flow field?

Have you taken into account a coefficient of discharge for you inlet?, if it is square then it should be set to about 0.6 i.e. you reduce the inlet area to the effective area.

How do you know it's the turbulence model that is the problem, have you tried running your simulation as a laminar flow case?

Turbulence models are necessary clutter. Changing the length scale on the inlet can have drastic effects, generally speaking increasing the length scale increases the recirculation. It probably has more effect than changing the intensity. Probably nobody will know the answers to what your asking you just have to experiment with the inlet boundary conditions.