CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Programming & Development (http://www.cfd-online.com/Forums/openfoam-programming-development/)

 lfgmarc October 25, 2011 10:57

HsEqn ReactingFoam Hypothesis?

Hi, I'm a little confuse with the assumptions under HsEqn implemented in reactingFoam, the energy equation in terms of the sensible enthalpy, can be written as:

My confusion is with two terms:

1. the term associated with the species diffusion:

2, the term associated with the energy dissipation by viscous effects:

The implementation of this equation in reactingFoam is:

Code:

     fvm::ddt(rho, hs)       + mvConvection->fvmDiv(phi, hs)       - fvm::laplacian(turbulence->alphaEff(), hs) //      - fvm::laplacian(turbulence->muEff(), hs)  // unit lewis no.     ==         DpDt       + chemistrySh
In this implementation I see that is neglected the viscous dissipation, but I don't understand very well why? i think that may be under the hypothesis of an Brinkman number<<1?

On the other hand it is clear that the species diffusion term was neglected, but reviewed bibliography I see that this term ussually is neglected if :

a) if mixture contains only one specie

b) if all species have the same sensible enthalpy.

c) sometimes is set to zero because it is usually negligible compared with

The first assumption in this case is not suitable, I'm confused with the second one, it is applicable in this case or simply is considered the third hypothesis?

if someone could shed some light on this I'll be very grateful