[mmkr825]

Hi foamers,
i developed my own solver for predicting velocity profile(U) and particle concentration profile(T) for suspension flow (fluid+particles). And in my momentum equation, the viscosity is not constant, it is function of particle volume fraction(T).
And i written the momentum equation as follows:

tmp<fvVectorMatrix> UEqn
(
fvm::div(phi, U)
- fvm::laplacian(nu*pow(1-T/0.68,-1.82), U)
);
UEqn().relax();

sources.constrain(UEqn());

solve(UEqn() == -fvc::grad(p));

where T is the particle volume fraction (dimensionless scalar field).

For predicting particle volume fraction(T), the governing equation written as:

solve
(
fvm::div(phi, T)
- fvm::laplacian(0.62*1.82*pow(a,2)*g*pow(T,2)*pow(0 .68-T,-1), T)
- fvm::laplacian(0.41*pow(a,2)*g*T, T)
==
fvc::laplacian(0.41*pow(a,2)*T*T, g)
);

Where g = local shear rate
= sqrt(2*E:E)
= 1.4142*sqrt(magSqr(symm(fvc::grad(U))))

when i run my case (simple channel flow) by using my solver, initially it is giving the following error.


error message:-

Create time

Create mesh for time = 0

Reading transportProperties

Reading field p

Reading field U

Reading field T

Reading/calculating face flux field phi

No field sources present


SIMPLE: convergence criteria
field p tolerance 0.01
field U tolerance 0.001
field T tolerance 1e-05


Starting time loop

Time = 1

DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 4.00548e-06, No Iterations 4
DILUPBiCG: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0
#0 Foam::errorprintStack(Foam::Ostream&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#2 Uninterpreted:
#3 FoamDILUPreconditioner::calcReciprocalD(Foam::Fi eld<double>&, Foam::lduMatrix const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#4 FoamDILUPreconditionerDILUPreconditioner(Foam: :lduMatrix::solver const&, Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#5 Foam::lduMatrixpreconditioner::addasymMatrixCons tructorToTable<FoamDILUPreconditioner>::New(Foam ::lduMatrix::solver const&, Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#6 Foam::lduMatrixpreconditioner::New(Foam::lduMatr ix::solver const&, Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#7 FoamPBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#8 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libfiniteVolume.so"
#9 Foam::fvMatrix<double>::solve() in "/home/malli_reddy/OpenFOAM/malli_reddy-2.1.1/platforms/linuxGccDPOpt/bin/myDiffusiveFoam"
#10
in "/home/malli_reddy/OpenFOAM/malli_reddy-2.1.1/platforms/linuxGccDPOpt/bin/myDiffusiveFoam"
#11 __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#12
in "/home/malli_reddy/OpenFOAM/malli_reddy-2.1.1/platforms/linuxGccDPOpt/bin/myDiffusiveFoam"
Floating point exception
malli_reddy@ubuntu:~/OpenFOAM/malli_reddy-2.1.1/PROJECT/myDiffusive$


But when i give good initial guess (by running the same case by using another solver in which coefficients are constants), then the case is running and giving good results. My geometry is 2D channel flow. when i run my case with checkMesh, it given no errors.


And i used SIMPLE scheme for pressure velocity coupling. And for
laplacian() Gauss linear corrected;
div() Gauss linear;

To generalize my solver should i shift to any other schemes?
Thanks in advance

cheers
Mallikarjuna