Compressor Simulation using rhoPimpleDyMFoam

vasava · December 1, 2014, 02:41

Quickly, if I were you I would not use fixedValue for inlet velocity if I am specifying pressure at the inlet. Instead use pressureInletOutletVelocity.

Also you are using fixed temperature at the outlet. Do you already know the temperature or you want openfoam to calculate the temperature? I would use fixed temperature at inlet and inletOutlet at outlet for temperature.

Please provide error messages, material properties and boundary files in the /0 folder.

maHein · December 2, 2014, 03:58

I would specify total pressure and temperature at the inlet and static pressure at the outlet. Most of the time, defining a uniform velocity profile at the inlet is rather nonphysical.

You could use pressureInletOutletVelocity for the U at the boundarie.

crixman · December 2, 2014, 10:39

thank you for the replies.
As you recommended, I specified the temperature at inlet and inletOutlet at outlet, and pressureInletVelocity for U at inlet.

If someone is interested, the same BCs do not converge on rhoSimpleFoam if I refine the mesh!

maHein · December 2, 2014, 10:43

Have you tried lowering the relaxation factors when using the finer mesh?

crixman · December 3, 2014, 08:04

Not really - I should check it, but I think it's more a SIMPLE algorithm problem than a matter of relaxation factors

Tobi · December 3, 2014, 08:23

Quote:

Originally Posted by crixman

Not really - I should check it, but I think it's more a SIMPLE algorithm problem than a matter of relaxation factors

Do not understand your statement?
Relaxation and SIMPLE is like a married couple (:
Without relaxation you will not can run SIMPLE in complex cases. This is due to some missing terms in the pressure prediction (see also Ferziger and Peric).

crixman · December 6, 2014, 07:59

You are right - I meant it is possibly due to the fact that it is a very unsteady case and is probably not the best case to use SIMPLE - I am having good results with PIMPLE solvers so I'll stick to that for now

crixman · December 9, 2014, 14:38

I am having AMI floating point exception problems when restarting the simulation from latestTime.
I got the same problem first when running renumberMesh in parallel after decomposePar - running rhoPimpleDyMFoam after decomposePar solved the problem.
Any ideas on how to solve this AMI issue at restart? Maybe someone had the same problem!

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December 1, 2014, 02:41		#101
vasava Senior Member Paritosh Vasava Join Date: Oct 2012 Location: Lappeenranta, Finland Posts: 732 Rep Power: 23	Quickly, if I were you I would not use fixedValue for inlet velocity if I am specifying pressure at the inlet. Instead use pressureInletOutletVelocity. Also you are using fixed temperature at the outlet. Do you already know the temperature or you want openfoam to calculate the temperature? I would use fixed temperature at inlet and inletOutlet at outlet for temperature. Please provide error messages, material properties and boundary files in the /0 folder.

December 2, 2014, 03:58		#102
maHein Member Join Date: Jun 2012 Posts: 76 Rep Power: 14	I would specify total pressure and temperature at the inlet and static pressure at the outlet. Most of the time, defining a uniform velocity profile at the inlet is rather nonphysical. You could use pressureInletOutletVelocity for the U at the boundarie.

December 2, 2014, 10:39		#103
crixman Member Christian Join Date: Apr 2014 Posts: 74 Rep Power: 12	thank you for the replies. As you recommended, I specified the temperature at inlet and inletOutlet at outlet, and pressureInletVelocity for U at inlet. If someone is interested, the same BCs do not converge on rhoSimpleFoam if I refine the mesh!

December 2, 2014, 10:43		#104
maHein Member Join Date: Jun 2012 Posts: 76 Rep Power: 14	Have you tried lowering the relaxation factors when using the finer mesh?

December 3, 2014, 08:04		#105
crixman Member Christian Join Date: Apr 2014 Posts: 74 Rep Power: 12	Not really - I should check it, but I think it's more a SIMPLE algorithm problem than a matter of relaxation factors

December 6, 2014, 07:59		#107
crixman Member Christian Join Date: Apr 2014 Posts: 74 Rep Power: 12	You are right - I meant it is possibly due to the fact that it is a very unsteady case and is probably not the best case to use SIMPLE - I am having good results with PIMPLE solvers so I'll stick to that for now

December 9, 2014, 14:38		#108
crixman Member Christian Join Date: Apr 2014 Posts: 74 Rep Power: 12	I am having AMI floating point exception problems when restarting the simulation from latestTime. I got the same problem first when running renumberMesh in parallel after decomposePar - running rhoPimpleDyMFoam after decomposePar solved the problem. Any ideas on how to solve this AMI issue at restart? Maybe someone had the same problem!