**fireFoam**

Transient solver for fires and turbulent diffusion flames with reacting particle clouds, surface film and pyrolysis modelling.

## Contents

## 1 Solution Strategy

The source code can be found in fireFoam.C

/*---------------------------------------------------------------------------*\ ========= | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox \\ / O peration | \\ / A nd | Copyright (C) 2011-2017 OpenFOAM Foundation \\/ M anipulation | ------------------------------------------------------------------------------- License This file is part of OpenFOAM. OpenFOAM is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. OpenFOAM is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>. Application fireFoam Group grpCombustionSolvers Description Transient solver for fires and turbulent diffusion flames with reacting particle clouds, surface film and pyrolysis modelling. \*---------------------------------------------------------------------------*/ #include "fvCFD.H" #include "turbulentFluidThermoModel.H" #include "basicReactingCloud.H" #include "surfaceFilmModel.H" #include "pyrolysisModelCollection.H" #include "radiationModel.H" #include "SLGThermo.H" #include "solidChemistryModel.H" #include "psiReactionThermo.H" #include "CombustionModel.H" #include "pimpleControl.H" #include "fvOptions.H" // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // int main(int argc, char *argv[]) { argList::addNote ( "Transient solver for fires and turbulent diffusion flames" " with reacting particle clouds, surface film and pyrolysis modelling." ); #include "postProcess.H" #include "addCheckCaseOptions.H" #include "setRootCaseLists.H" #include "createTime.H" #include "createMesh.H" #include "createControl.H" #include "createFields.H" #include "createFieldRefs.H" #include "initContinuityErrs.H" #include "createTimeControls.H" #include "compressibleCourantNo.H" #include "setInitialDeltaT.H" #include "createRegionControls.H" turbulence->validate(); // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Info<< "\nStarting time loop\n" << endl; while (runTime.run()) { #include "readTimeControls.H" #include "compressibleCourantNo.H" #include "solidRegionDiffusionNo.H" #include "setMultiRegionDeltaT.H" #include "setDeltaT.H" ++runTime; Info<< "Time = " << runTime.timeName() << nl << endl; parcels.evolve(); surfaceFilm.evolve(); if(solvePyrolysisRegion) { pyrolysis.evolve(); } if (solvePrimaryRegion) { #include "rhoEqn.H" // --- PIMPLE loop while (pimple.loop()) { #include "UEqn.H" #include "YEEqn.H" // --- Pressure corrector loop while (pimple.correct()) { #include "pEqn.H" } if (pimple.turbCorr()) { turbulence->correct(); } } rho = thermo.rho(); } runTime.write(); runTime.printExecutionTime(Info); } Info<< "End" << endl; return 0; } // ************************************************************************* //

## 2 Equations

### 2.1 Equations Liquid Film

The equation describing the evolution of the liquid film can be found in http://www.ilasseurope.org/ICLASS/iclass2012_Heidelberg/Contributions/Paper-pdfs/Contribution1294_b.pdf and https://www.witpress.com/Secure/elibrary/papers/MPF11/MPF11020FU1.pdf. A description of the method used to derive the equation can be found in https://www.researchgate.net/profile/Petr_Vita/publication/313655371_Thin_Film_Fluid_Flow_Simulation_on_Rotating_Discs/links/58a1a592a6fdccf5e9707665/Thin-Film-Fluid-Flow-Simulation-on-Rotating-Discs.pdf.

The conservation of mass reads:

| (x) |

represents the mean film velocity, the film height and mass source term resulting from the impingement of the liquid droplets on the film surface. The momentum conservation reads:

| (x) |

represents the pressure, the stress like components of the forces acting on the filme and represents the contribution to the momentum by the impinging droplets. The pressure contribution is divided in three components: The contribution due to capillary effects , the hydrostatic contribution and the contribution of the pressure originated by the surrounding gas .

The energy equation reads:

| (x) |

represents the mean film enthalpy and represents the contribution of the impinging droplets to the energy equation.

### 2.2 Equations Fluid

#### 2.2.1 Momentum conservation

The equation of motion are written for a moving frame of reference. They are however formulated for the absolute velocity (the derivation of the equations of motion can be found in https://openfoamwiki.net/index.php/See_the_MRF_development and also in https://diglib.tugraz.at/download.php?id=581303c7c91f9&location=browse. Some additional information can be found in https://pingpong.chalmers.se/public/pp/public_courses/course07056/published/1497955220499/resourceId/3711490/content/UploadedResources/HakanNilssonRotatingMachineryTrainingOFW11-1.pdf):

| (2) |

represent the velocity, the relative veloicty, the gravitational acceleration, the pressure minus the hydrostatic pressure and and are the viscose and turbulent stresses. Note that since the relative velocity appears in the divergence term, the face flux appearing in the finite volume discretization of the momentum equation should be calculated with the relative velocity. represents the force excreted by the particles on the fluid.

The source code can be found in Ueqn.H:

MRF.correctBoundaryVelocity(U); fvVectorMatrix UEqn ( fvm::ddt(rho, U) + fvm::div(phi, U) + MRF.DDt(rho, U) + turbulence->divDevRhoReff(U) == parcels.SU(U) + fvOptions(rho, U) ); UEqn.relax(); fvOptions.constrain(UEqn); if (pimple.momentumPredictor()) { solve ( UEqn == fvc::reconstruct ( ( - ghf*fvc::snGrad(rho) - fvc::snGrad(p_rgh) )*mesh.magSf() ) ); fvOptions.correct(U); K = 0.5*magSqr(U); }