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Old   December 15, 2007, 17:47
Default Hi everyone: I'm new to O.F
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Laurence Griffiths
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Hi everyone:

I'm new to O.F. and i was hoping maybe somebody could give me some tips on the following:

A)Is there the option to run high Ma (up to Ma=5, transonic would be nice but not necessary) but with a steady solver?

Or is it possible to speed the transient solvers up? I dont really care what the intermediate solution is - just the final converged one.

B)ive been trying to get rhoSimpleFoam to work, but unsuccessfully, does anybody have some input files they could send me for this case?
with me it keeps telling me i have incompatible dimensions (which i dont, the case works in other solvers).

C)Does anyone know the Ma range of rhoSimpleFoam. Some people have said Ma=1.3 max - is this correct?

Background info:
I'm trying to model an aerofoil in supersonic flow. Once this works i'd like to try something more complex.

anyway thanks a lot! Any help/advice on the above would be really really awesome!

regards,
Laurence
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Old   December 18, 2007, 17:35
Default hi again, has anyone here b
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Laurence Griffiths
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hi again,

has anyone here been able to get rhoSimpleFoam to work?
i keep getting an error that my dimensions are incorrect, does anyone know what the problem might be - or maybe experienced the same problem and know what the problem is? (ive tried to adapt the rhoTurbFoam and rhoSimpleFoam cases).

thanks,
Laurence
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Old   December 19, 2007, 00:11
Default Yes, it worked for me. 1) Del
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Doug Baldwin
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Yes, it worked for me. 1) Delete phi from initial timestep. You may have generated this by running potentialFoam. If you search the forum, you'll find I learned that phi compressible includes density whereas phi incompressible does not. 2) relaxation parameter for p = 0.001 or something very low, at least initially. I found I needed to monitor and adjust relaxation. Also, you can add a relaxation parameter rho = 0.3 or so. May want to start with all relaxation at about 0.1, except p which should be say 0.001 initially.

Doug
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Old   December 30, 2007, 15:15
Default thanks a lot for those tips -
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Laurence Griffiths
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thanks a lot for those tips - helped a lot, especially with the relaxation parameters.

I also had to initially set a high relative Tolerance for h for the first few iterations.

my initial mistake was just stupidity, under SIMPLE (fvSolution) i had:
pMin pMin[1 -1 -2 0 0 0 0] 100;
not
pMin pMin [1 -1 -2 0 0 0 0] 100;
i.e. missed out the space - (amazing how that took me almost a week to find)! isn't syntax just wonderful.

just thought id mentioned it in case somebody else has a similar problem.


if anyone has the time to explain what pMin actually does i would really greatly appreciate that too. (or better still, tell me where i can look it up, ive searched about and cant find anywhere that explains what this parameter does).
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Old   January 13, 2008, 09:00
Default Okay in response to my initial
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Laurence Griffiths
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Okay in response to my initial question, i managed to come up with the following. Hopefully it will save somebody else some time:

http://www.cfd-online.com/OpenFOAM_D...ges/1/929.html

In short, as i understand it, Openfoam cannot solve steady Compresible High Machnumber cases. (unless you solve it transient... which will take a very very long time!)
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