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May 6, 2009, 03:48 |
Weak rotational flow - Convergence Problems
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#1 |
New Member
Dag Stromsvag
Join Date: Apr 2009
Posts: 6
Rep Power: 17 |
Hi,
I am simulating seawater flow in a subsea particle filtration unit, with weak to moderate rotating flow induced by stationary curved fins. I get convergence using all k-epsilon models using SIMPLE pressure.velocity coupling, but when switching to k-omega (standard and SST) the solution only converge for 1st Order Upwind. When switching to higher order schemes the residual oscilliates around a specific point quite far from the convergence criteria of 0.001. It is mainly the continuity residual that struggles. I have tried under-relaxation and PISO, but they dont do the job. As inlet condition I have velocity inlet, and the outlet is an outflow. Most of the flow is laminar, but a certain region is turbulent so I figured I had to use turbulent modelling. Is there any basic steps I can apply in order to figure out the problem, and is it possible that the k-omega turbulence modelling law just doesn't apply in this case? ty |
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May 8, 2009, 10:45 |
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#2 |
Member
Ralf Schmidt
Join Date: Mar 2009
Location: Austria
Posts: 67
Rep Power: 17 |
Hi!
I have no experience with water, but it could be, that there are problems with your grid - see also: http://www.cfd-online.com/Forums/flu...cillation.html If just some region is turbulent, you might use a "laminar zone" in this regions to suppresses all turbulence (in the fluid BC). Another option would be, to change the gradient option (-> define -> models -> solver) . I have no idea, what is really behind this settings, but they helped me sometimes... Hope, that helps a little. Ralf
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