[waynezw0618]

Hi everyone

i have calculated the performance and internal filed in a centrifugal pump impeller using both OpenFOAM-1.5 and ANSYS CFX 11.0, for all calculation i use one mesh(i generated the mesh in ICEM-CFD 11.0,save a copy as .cfx for CFX,and the other as .msh for OpenFOAM,so for both solver use the same mesh)

the working conditions of all simulations are all part load off-design condtion,and for OpenFoam result are all face one problem(i will show in the table below),here is result of 25%Q_design

in OpenFOAM i have use both simpleSRFFoam & MRFSimpleFoam,and turbulence model is SST,the both two get the similar result,so i will show the result of MRFSimpleFoam here only ,here is fvScheme and fvSolution for MRFSimpleFoam

fvSolution:

solvers
{
p PCG
{
preconditioner GAMG
{

tolerance 1e-6;
relTol 0.05;

smoother DICGaussSeidel;
nPreSweeps 0;
nPostSweeps 2;
nBottomSweeps 2;

cacheAgglomeration false;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;

};
tolerance 1e-06;
relTol 0.01;
};
U smoothSolver
{
smoother GaussSeidel;
nSweeps 2;
tolerance 1e-7;
relTol 0.01;
};
k PBiCG
{
preconditioner DILU;
tolerance 1e-7;
relTol 0.1;
};
omega PBiCG
{
preconditioner DILU;
tolerance 1e-7;
relTol 0.1;
};
}

SIMPLE
{
nNonOrthogonalCorrectors 2;
}

relaxationFactors
{
p 0.3;
U 0.4;
k 0.4;
omega 0.4;
}


!! nNonOrthogonalCorrectors is 2

fvScheme:

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
grad(U) Gauss linear;
grad(Urel) Gauss linear;

}

divSchemes
{
default none;
div(phi,U) Gauss SFCD;
div(phi,Urel) Gauss SFCD;
div(phi,k) Gauss linear;
div(phi,epsilon) Gauss linear;
div(phi,omega) Gauss linear;
div(phi,v2) Gauss limitedLinear 0.5;
div(phi,f) Gauss limitedLinear 0.5;
div(phi,R) Gauss linear;
div(R) Gauss linear;
div(phi,nuTilda) Gauss upwind;
div((nuEff*dev(grad(U).T()))) Gauss linear;
div((nuEff*dev(grad(Urel).T()))) Gauss linear;
}

laplacianSchemes
{
default Gauss linear corrected;
laplacian(nuEff,U) Gauss linear corrected;
laplacian(nuEff,Urel) Gauss linear corrected;
laplacian((1|A(U)),p) Gauss linear corrected;
laplacian((1|A(Urel)),p) Gauss linear corrected;
laplacian(DkEff,k) Gauss linear corrected;
laplacian(DepsilonEff,epsilon) Gauss linear corrected;
laplacian(DomegaEff,omega) Gauss linear corrected;
laplacian(DREff,R) Gauss linear corrected;
laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
}

interpolationSchemes
{
default linear;
interpolate(U) linear;
interpolate(Urel) linear;
}

snGradSchemes
{
default corrected;
}

fluxRequired
{
default no;
p;
}

in CFX i try to use the StandardkEpsilo+scable wallfunction
/SST+ automatic wall fuction
/unsteady SST+automatic wall fuction
/SST-SAS automatic wall fuction
/LES Smaginsky subgrid model + scalable wall function

and the advection term scheme is High Resoltion method in ANSYS CFX11.0

the result of internel field is almost the same for all OF and CFX(I have post before:http://www.cfd-online.com/OpenFOAM_D...es/1/9426.html)

the stange thing is in openFOAM the pressure torque on Blade is very small(!!more than 10% of that of CFX SST),you could see in the table below:



SST-OF1.5 kEpsilon-CFX11 SST-CFX11 UNSST-CFX11 SSTSAS-CFX11 LES-CFX11

Torque_p@blade 0.39 0.41 0.43 0.43 0.44 0.45

Torque_viscous@blade 0.0039 0.0031 0.0035 0.0035 0.0036 0.0038

Torque_viscous@hub 0.054 0.012 0.015 0.015 0.018 0.049

Torque_viscous@shroud 0.053 0.020 0.030 0.033 0.033 0.048




i don`t know why but i guess there maybe 2 problems:

1) in fvScheme and fvSolutin. the scheme is different for CFX and OpenFOAM
2) solver.for ANSYS CFX is coupled solver for p and U,but NOT in OF

or is there any other things will cause the differents?

how can i resolve it ? how to set the fvScheme(to to switch on some limiters ) and fvSolution(change for p???) ??

thanks

yours wayne