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Error or Different Meaning of alpha in eEqu and hEqu of compressible solver?

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Old   July 20, 2010, 11:56
Default Error or Different Meaning of alpha in eEqu and hEqu of compressible solver?
  #1
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yu
Join Date: Nov 2009
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In compressible flow solvers, eEqu and hEqu share the same parameter "thermal diffusivity", or turbulence->alphaEff() in the following equations. However, my understanding of the meaning of thermal diffusivity should be different in these equaitons, i.e. , (for a laminar flow),

In eEqu, alpha = K / (Cv rho), where Cv, k and rho are heat capacity at constant volume, theremal conductivity and density, respectively.

while, in hEqu, alpha = k / ( Cp rho), where Cp, k and rho are heat capacity at constant pressure, theremal conductivity and density, respectively.

My questions are:

1, my understanding about alpha is right or wrong?
2, if i am right, is openFoam wrong ?, or there is specific application inside openfoam dealing with this issue?

========================================
In sonicFoam eEqu is

solve
(
fvm::ddt(rho, e)
+ fvm::div(phi, e)
- fvm::laplacian(turbulence->alphaEff(), e)
==
- p*fvc::div(phi/fvc::interpolate(rho))
);

========================================
In rhoPisoFoam hEqu is

fvScalarMatrix hEqn
(
fvm::ddt(rho, h)
+ fvm::div(phi, h)
- fvm::laplacian(turbulence->alphaEff(), h)
==
DpDt
);

Last edited by universez; July 26, 2010 at 13:38.
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Old   August 8, 2010, 11:51
Thumbs up compare with rhoFurbFoam
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kiran Ambilpur
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Hi yu
you are not wrong in understanding but you have compare similar solvers like rhoTurbFoam in 1.5 and sonicFoam in 1.6.

iam working on both the slovers and i feel both are same (Unsteady Turbulent compressible solvers).

try to analyze with rhoTurbFoam that will clear your doubt.
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