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#1 |
New Member
Michal
Join Date: Apr 2012
Location: Czech Republic
Posts: 27
Rep Power: 14 ![]() |
Hello,
I have a question about the energy equation (compressible flow - subsonic) in OF v 1.6-ext and 2.1.0 (there are some posts but still without answer). The conservation of energy has the form: ![]() where ![]() ![]() 1) From the conservation of energy I can derive the energy equation (EE), which is used in OF v 2.1.0 but I can not reach the EE which is implemented in version 1.6-ext. Why is the difference between EE? The left hand sides of the energy equations are the same in both versions and similarly the enthalpy definitions. Steady-state case without volume forces and viscous term (same EE implemented in OF 2.1.0): ![]() In OF 1.6-ext the EE: ![]() 2) I solved some simple case (diffuser), which can be "easy" described analytically. The OF 2.1.0 solver gives the best results.. BUT.. When I applied both version of OF solvers for same turbomachinery case, the version 2.1.0 gave unrealistic temperature field (convergent solution in both version, 6000it). If EE should be the same in both versions, why I have obtained so much different result for identically same case (velocity filed, temperature, pressure, thermoModel, turbulence, ...)? Your answers would be very helpful for me. Thank you. Michal Last edited by majkl; June 20, 2012 at 10:30. |
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#2 |
Member
prasant
Join Date: Jan 2013
Posts: 33
Rep Power: 13 ![]() |
Hello Michal,
I am solving one Impeller case. For me also, Temperature values are not coming properly at outlet. Did you recieve any information from people? If so, Could you please share that information? Regards Prasant. |
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#3 |
New Member
Michal
Join Date: Apr 2012
Location: Czech Republic
Posts: 27
Rep Power: 14 ![]() |
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#4 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26 ![]() |
hi dear michal.i have had doubt about energy equation ever.but i didn't understand what you have done.did diffuser problems were solved properly at both versions but another problem didn't?both versions gave incorrect results in second experiment or just one did so?
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#5 |
New Member
Join Date: Oct 2019
Posts: 13
Rep Power: 6 ![]() |
Hello foamers,
Did you succeed to perform any compressible flow simulation for turbomachinery application? What is you feedback? I have also encoutered some problems you were talking about. This is my case: OpenFOAM-v2006 Geometry: Centrifugal compressor, only one blade passage with cyclic/cyclicAMI (with diffuser vanedless and without volute) BCs: flowRateInletVelocity with fixedValue temperature inlet and fixedValue pressure outlet MRF model Turbulence: kOmegaSST Thermophysical: hePsiThermo, pureMixture, transport const, hConst, perfectGas, sensibleInternalEnergy Tried Solvers: rhoSimpleFoam, rhoCentralFoam, sonicFoam Results are strange, the pressure increased as expected at the exit but not the temperature which seems remain almost constant. Do you have any idea of the problem? |
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#6 |
Senior Member
Herpes Free Engineer
Join Date: Sep 2019
Location: The Home Under The Ground with the Lost Boys
Posts: 931
Rep Power: 12 ![]() |
I kindly suggest you to review the understanding of yours for the problem at hand: I don't see any application that you can subsequently test {rhoSimpleFoam, rhoCentralFoam, sonicFoam} for modelling of the same physical phenomena. Yet note that compressible flow simulations in general are far more sensitive to the numerical settings than its incompressible counterparts.
If the concern of yours is the numerical stability: I suggest you to test these fvOptions: limitTemperature, (if the case is unsteady) limitVelocity, (if the case is steady) velocityDampingConstraint.
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