unphysical behaviour in buoyantSimpleFoam at inclined surfaces
 

Hi there,
I wanted to run a case with the buoyantSimpleFoam solver but got some strange behaviour of the flow - at an inclined wall the hot air moves in the direction of gravity. For comparison I ran the same case with a vertical wall and got the expected result. Moreover, running the case with the inclined wall with the buoyantBoussinesqSimpleFoam solver also gives the expected results. - see attached images
Attachment 19805

Attachment 19808

Attachment 19807

The boundary conditions were the following:
p_rgh
internalField uniform 101325;
boundaryField
{
hotWall
{
type buoyantPressure;
value $internalField;
}
fixedWalls
{
type buoyantPressure;
value $internalField;
}
}

U
internalField uniform (0 0 0);
boundaryField
{
hotWall
{
type fixedValue;
value uniform (0 0 0);
}
fixedWalls
{
type fixedValue;
value uniform (0 0 0);
}
}

k
internalField uniform 0.1;
boundaryField
{
hotWall
{
type compressible::kqRWallFunction;
value uniform 0.1;
}
fixedWalls
{
type compressible::kqRWallFunction;
value uniform 0.1;
}
}

epsilon
internalField uniform 0.01;
boundaryField
{
hotWall
{
type compressible::epsilonWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0.01;
}
fixedWalls
{
type compressible::epsilonWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0.01;
}
}

mut
internalField uniform 0.01;
boundaryField
{
hotWall
{
type compressible::epsilonWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0.01;
}
fixedWalls
{
type compressible::epsilonWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0.01;
}
}

Can anybody tell me whether this is a bug or my boundary conditions are not suitable?

Thanks a lot,
Hannes

Hi Hannes,

this looks really strange.
Which schemes did you use?

The fluid is an ideal gas?

Bye RMF

Dear RMF,

yes, the fluid is calculated as ideal gas. The used schemes are as follows:

ddtSchemes
{
default steadyState;
}
gradSchemes
{
default Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss upwind;
div(phi,h) Gauss upwind;
div(phi,K) Gauss upwind;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div((muEff*dev2(T(grad(U))))) Gauss linear;
}
laplacianSchemes
{
default none;
laplacian(muEff,U) Gauss linear uncorrected;
laplacian((rho*(1|A(U))),p_rgh) Gauss linear uncorrected;
laplacian(alphaEff,h) Gauss linear uncorrected;
laplacian(DkEff,k) Gauss linear uncorrected;
laplacian(DepsilonEff,epsilon) Gauss linear uncorrected;
laplacian(DREff,R) Gauss linear uncorrected;
}
interpolationSchemes
{
default linear;
}
snGradSchemes
{
default corrected;
}
fluxRequired
{
default no;
p_rgh;
}

anybody any idea?
Thanks a lot
Hannes

thanks to Henry I got the solution:
"Inclining the wall makes the mesh non-orthogonal but you choose an uncorrected laplacian but a corrected snGrad. If you correct for non-orthogonality the flow goes in the expected direction."

hi Hanness.do we use unCorrected in orthogonal meshes only and for non normal faces(non-orthogonal) use corrected?should both laplacian and snGradSchemes be the same?am i correct?when we use limit?