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May 5, 2006, 18:20 |
SIMPLE and spurious oscillations
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#1 |
Guest
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Hi!
I am carrying out the computation of a swirling combustion chamber: 1- 3D, (nearly) isotropic unstructured grid 2- SIMPLE, stationary version (no time-dependent terms) 3- k-epsilon turbulence model 4- energy and species equations The problem is that I can get a "stationary" solution only if I use a first-order upwind scheme for the convective terms. Higher order schemes (CDS, QUICK, LUDS, ecc...) do not yield to a stationary solution even with a limiter function. On the other hand, the cold run (no chemical reactions, no flame, only small T gradients due to high wall temperature) converges with all these schemes. Moreover: I have tried to perform some iterations keeping all the variables but velocity and pressure constant (under relaxation factor = 0) and even in this case V and p oscillate without end. Very generic question: what can I do to improve the situation? Thanks Max |
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May 5, 2006, 22:27 |
Re: SIMPLE and spurious oscillations
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#2 |
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Do you expect the flow to be steady? Are you sure that a 'stationary' solution exists? Turn off all convection stabilisation & see what happens. Plot the output data at various times (say a cutplane), put into Powerpoint & run as a movie. What do you observe? Are there any patterns to what you see?
diaw... |
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