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TEqn implementation in icoReactingMultiphaseInterFoam 

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September 30, 2019, 10:28 
TEqn implementation in icoReactingMultiphaseInterFoam

#1 
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Gowthaman Parivendhan
Join Date: Aug 2019
Location: Dublin, Ireland
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Hi Foamers,
I have a basic question on implementation of temperature equation in one of the solvers in OF v1806. I was going through the TEqn.H file of icoReactingMultiphaseInterFoam in OF and found the following implementation: Code:
fvScalarMatrix TEqn ( fvm::ddt(rhoCp, T) + fvm::div(rhoCpPhi, T, "div(phi,T)")  fvm::Sp(fvc::ddt(rhoCp) + fvc::div(rhoCpPhi), T)  fvm::laplacian(kappaEff, T, "laplacian(kappa,T)") == fluid.heatTransfer(T) + radiation>ST(T) + fvOptions(rhoCp, T) ); +  If that is the case, then why are density and Cp has taken out as constant? Shouldn't the volume of fluid averaged rhoCp depend on both time and space in a multiphase system? Please let me know if I'm missing something here as I'm quite new to heat transfer modelling. Many thanks, Gowthaman 

December 4, 2022, 20:40 

#2 
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Corbin G
Join Date: Oct 2022
Location: Midwest, USA
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Hi Gowthaman,
I think you are correct. At least for the transient term we can use the product rule to expand: Using algebra to rearrange we have the below equation. The right hand side corresponds, in so far as I can tell, to what is implemented in icoReactingMultiphaseInterFoam TEqn.H. Therefore, effectively the LHS is being calculated. Now, why code the right hand side instead of just putting directly? I have a theory: fvm::ddt(rhoCp, T) makes an fvScalarMatrix data type. OpenFOAM, in my experience, does not allow the multiplication of volScalarField by fvScalarMatrix or it will give error at compilation. That is to say, if we had rhoCp stored as volScalarField, rhoCp*fvm::ddt(T) would give volScalarField*fvScalarMatrix compilation error. Fauster has documented this volScalarField*fvScalarMatrix compilation error, but no one has responded a way to get around it: How to multiply volScalarField and fvScalarMatrix ? EDIT: Thank you to newGuyAtCFD for pointing out my oversight. Please regard my aforementioned theory as incorrect. volScalarField*fvScalarMatrix IS possible. But, fvScalarMatrix*volScalarField gives compilation error: Code:
volScalarField rhoCp1 = rho1*alpha1*mixture.thermo1().Cp() + rho2*alpha2*mixture.thermo2().Cp(); fvScalarMatrix eEqn ( rhoCp1*fvm::ddt(T) // compiles OK! //fvm::ddt(T)*rhoCp1 // gives compilation error! == fvOptions(rhoCp1, T) ); Last edited by CorbinMG; December 14, 2022 at 11:34. 

December 5, 2022, 16:07 

#3 
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Quote:
To my understanding the above code should represent: Where everything is inside the parenthesis. Please correct me if I am wrong. Also, multiplying a volScalarField with a matrix is possible and defined on line 28162826 of fvMatrix.C Code:
template<class Type> Foam::tmp<Foam::fvMatrix<Type>> Foam::operator* ( const volScalarField::Internal& dsf, const tmp<fvMatrix<Type>>& tA ) { tmp<fvMatrix<Type>> tC(tA.ptr()); tC.ref() *= dsf; return tC; } Last edited by newGuyAtCFD; December 6, 2022 at 05:54. 

December 6, 2022, 05:12 

#4  
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Quote:
I agree with you, but corrected the T into the derivatives. The orginial equation should look like this with the mentioned substitutions of the reformulated differentials. I mean this should be equal same for the divergence term. Then it follows: Which is nothing else than: My guess is that inserting of the reformulated differentials was done either because of discretization reasons or because of the interphase properties. 

August 9, 2023, 10:00 

#5 
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S Abrahams
Join Date: Mar 2022
Location: UK
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Hi everyone,
I wonder if anyone can help me with a followup question please? In compressibleInterFoam in OF9, the TEqn is formulated as Code:
fvm::ddt(rho, T) + fvm::div(rhoPhi, T)  fvm::Sp(contErr, T)  fvm::laplacian(turbulence.alphaEff(), T) + ( fvc::div(fvc::absolute(phi, U), p)()() //  contErr/rho*p + (fvc::ddt(rho, K) + fvc::div(rhoPhi, K))()()  (U()&(fvModels.source(rho, U)&U)())  contErr*K ) *( alpha1()/mixture.thermo1().Cv()() + alpha2()/mixture.thermo2().Cv()() ) == fvModels.source(rho, T) I believe the TEqn should be equivalent to but the formulation above seems to be equivalent to Can anyone help me to understand how has been taken out in this way? Many thanks, SAbrahams Last edited by sabrahams; August 9, 2023 at 13:16. Reason: spelling 

Tags 
heat and mass transfer, openfoam 1806, teqn, vof method 
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