abdul099 |
January 18, 2013 15:04 |
Quote:
Originally Posted by siara817
(Post 402100)
I think the problem is that you have considered a turbulent case as laminar, the case is turbulent
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I don't think this is the issue. Even when you run a turbulent case, you can often experience oscillating solutions. There's a difference between a turbulent case (which models small scale unsteady turbulence effects) and a laminar unsteady case (which models unsteady effects, but does not take small scale turbulence effects into account).
Quote:
Originally Posted by siara817
(Post 402100)
As the velocity is low, you need to activate a near wall treatment model, the best is to use Two layer all y+ wall treatment
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This does not necessarily depend on the velocity. Also a two layer model has it's restrictions, and pretty often you mix crap with crap by using a two layer model without properly adjusting your mesh to this model. It is dangerous to use a two layer model as a general advice when the one using this model does not now where the limitations are.
Quote:
Originally Posted by siara817
(Post 402100)
run the simulation first by running first order scheme and then if it is converged change it to the second order.
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When a simple case like this is set up in a proper way, you should not need to run first order before switching to second order. Your flow might not show the unsteady behaviour when running first order since it smears the solution. But when you switch back to second order, it's just a matter of time until you can see the unsteady behaviour again. So this does not help to get a non-oscillating solution. It helps only when you case diverges during the first few iterations.
I think shanefarrell needs to give some additional information to judge what the issue is.
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