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August 4, 2009, 10:19 |
how to implement this kind of equation
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New Member
mihamina keisha
Join Date: May 2009
Location: india
Posts: 19
Rep Power: 16 |
hi there!
I'm modeling a combustion problem(2D problem) and I have trouble implementing this equation: (vs rhoapp Cps)d/dx(Ts)-laplacian(lambda,Ts) = S; where d/dx stands for derivative with respect to x vs stands for the velocity of the household refuse entering the incinerator (dimensionedVector) rhoapp is a volScalarfield (density) Cps is the heat capacity S is a source term Here is what I tried: solve ( -fvm::laplacian(lambdaeff,Ts)+fvm::div(rhoappvsCp, Ts) ==S ); coupled with the gas mixture temperature (in order to take into account the convective transfer included in the source term of both equations) which is: solve(fvm::div(phi,T) == SS); rhoappvsCp is surfaceScalarField it starts well but it crashes after. I thought it was due to the boundary condition in the beginning(conservative flux) but when I turned it into a transient problem which gave: solve ( -fvm::laplacian(lambdaeff,Ts)+fvm::ddt(rhoappvsCp, Ts) == S ); solve ( fvm::ddt(rhoCpporo, T)+fvm::div(phi,T) == SS ); it's ok,it ran well and gave an accurate solution! Then I ended up thinking that the problem was due to the implementation of this term ""(vs rhoapp Cps)d/dx(Ts)"" So I tried to do something else like this: solve ( -fvm::laplacian(lambdaeff,Ts)+rhoappvsCp*(myvector & fvc::grad(Ts)) == S ); Because I thought that it was a gradient term but the y component should be eliminated then I created a vector myvector (1 0 0),and with the inner product the y component is omitted! it still crashed!!!! in the source code I also have to implement the density equation which is: d/dx(vs rhoapp) = S and I went on with the elimination of the y-component: mag(vs)*(myvector & fvc::grad(rhoapp)) == Srhoapp but it sends an error message!!!before,I took it as divergence term using fvm::div(svs,rhoapp) = Srhoapp svs is a surfaceScalarField and it runs well but I don't think that it is a divergence term!!! So my question is how to implement this kind of equation "(vs rhoapp Cps)d/dx(Ts)" and this "d/dx(vs rhoapp)" DIVERGENCE OR GRADIENT WITH Y-COMPONENT ELIMINATED?? I'M QUITE STUCK!!! Please can somebody help me out? Best Regards |
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