# Cavitation inception problem

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 May 8, 2003, 08:14 Cavitation inception problem #1 newuser Guest   Posts: n/a Hi I am modeling flow of water around hemisphere cylinder configuration using multifluid mixture model with cavitation. At zero degree angle of attack cavitation inception number is in very good agreeement with experimental results. But at 5 degrees angle of attack results are erroneous. Fluent6.012 predicts cavitation inception number very high as compared to experimetal cavitation inception number number. Whats wrong with the simulation . I am using same parameters as given in cavitation tutorial of Fluent tutorial documentation. Please comment on this problem.

 May 8, 2003, 10:01 Re: Cavitation inception problem #2 mateus Guest   Posts: n/a Hi! In Fluent 6.12 you have to input two parametres that are not really well known - the bubble number per m^3 and the bubble radius. The tutorial uses n=10000 and r=10^-5m (iīm not shure if is it radius or diameter). The problem is that noboby realy knows what are the real values. I found values ov number of bubbles from 10000 to 1000000000 per m^3. Itīsnot so bad for the radius - from 10^-5 to 10^-4 m. In any case if you find good agreement with experiment using any number within these values you are ok. On the other hand I would rather use the new fluent version (6.1.18) to model cavitation. Itīs model is much more stabil and all the parameters are easelly measurable). Best regards MATEUS

 May 9, 2003, 09:24 Re: Cavitation inception problem #3 newuser Guest   Posts: n/a Thanks Mateus! I have used different bubble densities and different bubbles radius but it does not affect results so much. Results are still erroneous at 5 degrees angle of incidence

 May 13, 2003, 11:14 Re: Cavitation inception problem #4 mateus Guest   Posts: n/a Hi! Sorry for repliying late. Maybe you should try to calculate with higher order of accuracy, or with different tipes of pressure-velocity cupling... I've had some problems with simulating unsteady cavitation and this more or less solved it. best regards MATEUS

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