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Ianina December 21, 2005 19:15

Influence of turb. intensity at the inlet?

one question about turbulence intensity:

I am modeling the flow past a bluff body (hemisphere) attached to a wall of a channel. Conditions: turbulent, subcritical. I am using k-omega SST turbulent model with appropriate grid resolution near the wall (y+ = 0.5 at max). Also second order discretization schemes are used. The body is placed approx. 6 diameters downstream from the inlet to investigate the effect of different gradients in velocity profile. Turbulence intensity is given according the recommendations of Fluent manual (in this case about 4%)

I would like to ask for the opinion on following: comparing the distributions of Cp with the wind channel experiments i get a different position of min Cp (at 80 degrees) as it was measured (at 75-78 degrees) and consequentially later separation. In this case solution converges to a steady state. I tried to set the turb. intensity to 1 % and got separation earlier but solution does not converge any more to a steady state. Is it physical behavior or the problem of the turbulence model? I noticed some messages on the problems with convergence at a low turbulence level in the forum before.

Any opinion is highly appreciated


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