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 jose_rodrig July 16, 2011 10:33

chemical time scale

Hi,

Does anybody knows how OpenFOAM calculates the chemical time scale, tc ?

I am deciphering the source code right now, but it would be nice to have somebody else's work to compare with.

Any help?

Jose

 megacrout August 16, 2011 03:26

Hi José,

If you´re simply looking for the formula, you´ve got a first answer on slide 16 of the following presentation:
http://www.openfoamworkshop.org/6th_...ist_slides.pdf

If you´re trying to determine how and where exactly this parameter is computed in OpenFOAM format, I´m afraid I can´t help. I actually looked for it - as I am running simulations with reactingFoam and find the question interesting - but did not quite get it. I guess it would help to have more than just my basic knowledge of C++!

I´d be glad to read your findings here in case you got more than that in the meantime.

Tibo

 Manuel CFD November 19, 2013 13:03

Chemical time scale in PaSR model

Dear all,

I have a doubt concerning chemical time scale computation in ChemistryModel class. Mainly I'm referring to the tc() function reported in the following:

Code:

``` if (this->chemistry_)     {         forAll(rho, celli)         {             scalar rhoi = rho[celli];             scalar Ti = this->thermo().T()[celli];             scalar pi = this->thermo().p()[celli];             scalarField c(nSpecie_);             scalar cSum = 0.0;             for (label i=0; i<nSpecie_; i++)             {                 scalar Yi = Y_[i][celli];                 c[i] = rhoi*Yi/specieThermo_[i].W();                 cSum += c[i];             }             forAll(reactions_, i)             {                 const Reaction<ThermoType>& R = reactions_[i];                 omega(R, c, Ti, pi, pf, cf, lRef, pr, cr, rRef);                 forAll(R.rhs(), s)                 {                     scalar sr = R.rhs()[s].stoichCoeff;                     tc[celli] += sr*pf*cf;                 }             }             tc[celli] = nReaction*cSum/tc[celli];         }     }```
Could anyone explain me in details how this chemical time is computed? Which is the physical expression taken as reference? Are there any literature works concerning the evalutation of this term?
I've read a lot of works about PaSR model where they talk about the general overview of this combustion model but in each of them they talk about the need of solving detailed reaction system in order to obtain this time. But I've never found how this has to be done.

Thank you.

Manuel

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