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rhoSimpleFoam, simple setup, wrong BC?

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Old   May 17, 2016, 11:20
Post rhoSimpleFoam, simple setup, wrong BC?
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Tim Anonym
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Dear Foamers,

I struggle with this testcase for a while now.
I've got an instability issue with a rhoSimpleFoam case.
I'm using total pressure and total temperature at inlet and static pressure at outlet. Additionally the direction at inlet is given.
I turned the turbulence off for simplicity.

The case files are attached. The basic setup is as follows:

Geometry:
2D, rectangle, 2 sides are connected cyclic, inlet, outlet
originally there was a turbine blade in the middle, which i removed for simplicity

Boundary conditions(p, T, U)
inlet: totalpressure, totaltemperature, pressureDirectedInletVelocity
outlet: fixedValue, zeroGradient, inletOutlet

solver: rhoSimpleFoam

If i run the solver, velocity rapidly increases at inlet and consequently (or the other way round) pressure drops. Then the flow at outlet reverses and the calculation diverges.

I really need some advice, what causes the instability.

Thanks for your help!

Greetings, Tim
Attached Files
File Type: gz 0.tar.gz (1.2 KB, 33 views)
File Type: gz constant.tar.gz (128.2 KB, 13 views)
File Type: gz system.tar.gz (2.6 KB, 14 views)
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Old   May 23, 2016, 08:35
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Is your issue solved yet? Just a guess: I had quite a similar problem which I solved by setting 'value' to 'uniform 0' (in 'p.totalPressure'). It seems like this offers the solver more "flexibility" to adjust dynamic and static pressure at the boundary - but I did not look very close at it.

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Old   May 24, 2016, 05:59
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Tim Anonym
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Thanks for your reply.

Setting the initial value of p at inlet to 0 gives an error, because I'm doing a compressible case. Setting it close to 0 doesn't seem to change the problem.

I'm open for any further suggestions. Just give the ideas. Nothing can be worse than it's now.
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Old   September 1, 2016, 09:02
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larmes
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did you solve your issue?
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divergence, rhosimplefoam, totalpressure, totaltemperature

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