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problem with total enthalpy solved by rhoporousmrfsimplefoam |
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January 26, 2012, 07:59 |
problem with total enthalpy solved by rhoporousmrfsimplefoam
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#1 | |
New Member
Join Date: Oct 2011
Posts: 4
Rep Power: 14 |
Hi all!
I'm solving a compressor with rhoporousmrfsimplefoam and my problem is,that my real total enthalpy is below the isentrope one at the outlet. So i have an efficieny factor above 1(what a nice factor ), but it should be near by 0.7(CFX). At the outlet my pressure is near by the value of CFX(a little bit to high), total temperature is to low and my density is to high. To find my mistake much faster i created a case with a simple pipe and the same settings and solver. I changed some BC's and other settings, but there is still the same problem. When i solve it laminar with low velocity the result looks fine. Is there a problem with my komegasst-model? Or maybe my BC's are not correct? These are the files of the pipe-case: Quote:
Regards, Eric |
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February 14, 2012, 04:21 |
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#2 |
New Member
Join Date: Oct 2011
Posts: 4
Rep Power: 14 |
edit: In the case with the simple pipe the total temperature at the outlet is lower than the total temperature at the inlet, but it should be the same, because its adiabatic. I think my BC's are correct, aren't they? So is there a problem with the h-equation or something else?
Thank you in advance! Regards, Eric |
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February 16, 2012, 05:31 |
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#3 |
New Member
Martin
Join Date: Feb 2012
Location: Germany
Posts: 13
Rep Power: 0 |
I encountered a similar issue. I was simulating a compressor wheel with rhoPorousMRFSimpleFoam using OpenFOAM 2.1.x. Despite compression, the temperature decreased by about 30K. Previous simulations with openFOAM 2.0.x resulted in an increase of about 30K.
So I took a closer look at the hEqn.H of the solver: OpenFOAM 2.1.x Code:
fvScalarMatrix hEqn ( fvm::div(phi, h) - fvm::Sp(fvc::div(phi), h) - fvm::laplacian(turbulence->alphaEff(), h) == - fvc::div(phi, 0.5*magSqr(U), "div(phi,K)") ); Code:
fvScalarMatrix hEqn ( fvm::div(phi, h) - fvm::Sp(fvc::div(phi), h) - fvm::laplacian(turbulence->alphaEff(), h) == fvc::div(phi/fvc::interpolate(rho), rho/psi, "div(U,p)") - (rho/psi)*fvc::div(phi/fvc::interpolate(rho)) ); |
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January 28, 2013, 02:06 |
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#4 |
Member
prasant
Join Date: Jan 2013
Posts: 33
Rep Power: 13 |
Hello All,
Did you get any information regarding correction in hEqn If so, please share the information with me. I tried to modified the hEqn as per Eric comments. But still outlet temperature is decreasing. Regards Prasant. |
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