CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

OpenFOAM, Difference between combustion and reaction

Register Blogs Community New Posts Updated Threads Search

Like Tree1Likes
  • 1 Post By clapointe

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 30, 2019, 15:22
Default OpenFOAM, Difference between combustion and reaction
  #1
Member
 
Farshad
Join Date: Sep 2010
Posts: 36
Rep Power: 16
farshadexp is on a distinguished road
Hi;
Can any one explain the differences between following codes, bold lines:


Code:
forAll(Y, i)
    {
        if (i != inertIndex && composition.active(i))
        {
            volScalarField& Yi = Y[i];

            fvScalarMatrix YiEqn
            (
                fvm::ddt(rho, Yi)
              + mvConvection->fvmDiv(phi, Yi)
              - fvm::laplacian(turbulence->muEff(), Yi)
             ==
                reaction->R(Yi)
              + fvOptions(rho, Yi)
            );

            YiEqn.relax();

            fvOptions.constrain(YiEqn);

            YiEqn.solve(mesh.solver("Yi"));

            fvOptions.correct(Yi);

            Yi.max(0.0);
            Yt += Yi;
        }
    }
Code:
forAll(Y, i)
    {
        if (i != inertIndex && composition.active(i))
        {
            volScalarField& Yi = Y[i];

            fvScalarMatrix YiEqn
            (
                fvm::ddt(rho, Yi)
              + mvConvection->fvmDiv(phi, Yi)
              - fvm::laplacian(turbulence->alphaEff(), Yi)
              ==
                parcels.SYi(i, Yi)
              + surfaceFilm.Srho(i)
              + combustion->R(Yi)
              + fvOptions(rho, Yi)
            );

            YiEqn.relax();

            fvOptions.constrain(YiEqn);

            YiEqn.solve(mesh.solver("Yi"));

            fvOptions.correct(Yi);

            Yi.max(0.0);
            Yt += Yi;
        }
    }
the first one is part of YEqn.H (reactingFoam) and the second one is part of YEEqn.H (fireFoam).
farshadexp is offline   Reply With Quote

Old   March 31, 2019, 13:16
Default
  #2
Senior Member
 
Join Date: Aug 2015
Posts: 494
Rep Power: 15
clapointe is on a distinguished road
There shouldn't be any difference. If you check the respective create fields, you'll notice one creates names the combustion autoPtr "combustion" and the other names it "reaction".

Caelan
clapointe is offline   Reply With Quote

Old   March 31, 2019, 16:42
Default
  #3
Member
 
Farshad
Join Date: Sep 2010
Posts: 36
Rep Power: 16
farshadexp is on a distinguished road
Dear Caelan, thanks for your answer.

You are right. I quote both of the pointer definitions below for future users who may follow this thread:


Code:
autoPtr<CombustionModel<psiReactionThermo>> reaction
(
    CombustionModel<psiReactionThermo>::New(thermo, turbulence())
);

Code:
autoPtr<CombustionModel<psiReactionThermo>> combustion
(
    CombustionModel<psiReactionThermo>::New(thermo, turbulence())
);
But I have a more general Q. what's the difference between fireFoam and for example reactingFoam?! Why EDC or PaSR combustion models do not works with fireFoam, in other words, no reaction (no temperature rise) occurs when using EDC or PaSR in fireFoam solver!
farshadexp is offline   Reply With Quote

Old   March 31, 2019, 18:49
Default
  #4
Senior Member
 
Join Date: Aug 2015
Posts: 494
Rep Power: 15
clapointe is on a distinguished road
In brief, fireFoam tutorials are all configured to use infinitelyFast chemistry. To use other combustion models you'll likely need to provide some sort of energy source (eg a spark or a pilot flame or preheating reactants) to start reactions. Look into the reactingFoam tutorials for examples for how to do this. However, then you'll need to start thinking about the nature of your combustion problem -- for mixing controlled diffusion flames the infinitely fast assumption is not a terrible one. That said, there are extensions of the EDC to les that do modify the infinitely fast heat release by local laminar/turbulence timescales (see e.g. https://www.sciencedirect.com/scienc...79711214000125). I think the OpenFoam+ side has a variant of this.

Caelan
clapointe is offline   Reply With Quote

Old   April 1, 2019, 02:49
Default
  #5
Member
 
Farshad
Join Date: Sep 2010
Posts: 36
Rep Power: 16
farshadexp is on a distinguished road
I used energy sources (e.g ignition by setFields and fvSolution) but nothing changed.
I am going to try extended version of OF, maybe I could find the solution.
p.s: results of infinitelyFast are not reliable comparing with experiments for pool fire.
farshadexp is offline   Reply With Quote

Old   April 1, 2019, 11:42
Default
  #6
Senior Member
 
Join Date: Aug 2015
Posts: 494
Rep Power: 15
clapointe is on a distinguished road
If you change the combustion model, you will need to make corresponding changes to the thermo/reactions. Re. infinitely fast, it may not work out of the box. As I said, extension to the eddy dissipation model works quite well. See eg. https://www.sciencedirect.com/scienc...10002944#b0005.

Caelan
farshadexp likes this.
clapointe is offline   Reply With Quote

Reply

Tags
combustion model, openfoam6


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to switch off combustion and reaction in reactingFoam shenzhou1987 OpenFOAM Running, Solving & CFD 16 October 26, 2017 16:31
Detailed Chemical reaction over combustion model jaychhatbar AVL FIRE 1 June 23, 2017 14:13
how to add the ion reaction to the combustion mechanism in Chemkin Pro dfzw_jwd Main CFD Forum 0 December 1, 2016 04:30
Coal combustion and ash reaction kinetics sega Fluent UDF and Scheme Programming 0 January 21, 2010 09:05
combustion - reaction rates - urgent help needed siri Main CFD Forum 2 March 3, 2007 13:25


All times are GMT -4. The time now is 17:09.