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-   -   FireFoam what is HRR ? (http://www.cfd-online.com/Forums/openfoam-post-processing/75026-firefoam-what-hrr.html)

fgal April 14, 2010 14:58

FireFoam what is HRR ?
 
Hi OpenFoamers,

Does anybody knows what the volumic scalar field HRR is? Because I thought that it was the combustion source term in the energy equation but it is sometimes negative.

Is it divided by the cell volume, because it can raise values around+/- 1E6 ?

Many thanks

Francois Gallard

fgal April 16, 2010 10:37

Hi, I found this in the fireFoam source code :
HRR=
- fvc::ddt(rho, hc)
- fvc::div(phi, hc)
+ fvc::laplacian(turbulence->alphaEff(), hc);

So it seems that the HRR is defined as all the source terms in the enthalpy equation except for the heat Fourier and turbulent diffusions. So, if I am right, source terms left are :
- heat due to chemistery
- heat due to friction, certainly close to zero because of very low Mach number of the flow
- radiated heat, but I swiched the radiation off
- inter spieces diffusion term, zero because all heat capacities are supposed to be equals
-the pressure term, very low

So I still don't understand why the heat release rate can be negative and positive depending on the cells, with so huge variations : -1E6 ; +1E6

Has anybody an idea ?


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