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newposter June 7, 2006 11:55

boundary conditions compressible flow

I want to simulate a shock in laval nozzle with my pressure-correction based SIMPLE code. I want to prescribe at Inlet: u,v,w and T at the Outlet: p_Stat

I can`t get convergence, the residuals are oszillating.

What can I do, please help?!

khai ching June 7, 2006 21:44

Re: boundary conditions compressible flow
What if you try to fix the stagnation properties at the inlet, e.g. Total Pressure, Total Temperature as well as the flow angle

newposter June 8, 2006 02:45

Re: boundary conditions compressible flow
That`s possible and working! My question is only if it`s possible to fix u,v,w and T and to get results with shocks and so on... Thank`s...

Mani June 9, 2006 16:41

Re: boundary conditions compressible flow
I don't see the point of doing that. The total pressure and total temperature are "natural" inlet conditions, because they are usually known from experiments, and they can be viewed as independent from the exit static pressure. Inlet flow angles are quasi known because of the duct geometry. On the other hand, the inlet velocity is not usually known in internal flow problems. Think physically: Flow is determined by pressure gradients, especially in internal flow, and your CFD should be driven by a natural condition. You ought to have some information on (total) pressure at the inlet. As a general remark: The number of conditions that you need to provide depend on the number of characteristics traveling into/out of the domain at the boundary, and that number is well known. However, the number alone does not guarantee convergence, or even existence of a unique solution. You have to choose a reasonable (preferably physical) combination of boundary conditions.

newposter June 16, 2006 17:10

Re: boundary conditions compressible flow
Thank you very much!!

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