CFD Online Discussion Forums - rhoCentralFoam linearUpwind

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rhoCentralFoam linearUpwind

Dear foamers.
I want to try the schemes linearUpwind in interpolationSchemes for rhoCentralFoam solver.
In the begining my fvSchemes file looks so:

Code:

fluxScheme Tadmor;

ddtSchemes

{

default Euler;

}

gradSchemes

{

  default cellLimited leastSquares 1;

}

divSchemes

{

default none;

div(tauMC) Gauss linearUpwind;

div(phi,k) Gauss linearUpwind;

div(phi,omega) Gauss linearUpwind;

}

laplacianSchemes

{

default Gauss linear corrected;

}

interpolationSchemes

{

default linear;

reconstruct(rho) upwind;

reconstruct(U) upwind;

reconstruct(T) upwind;

}

snGradSchemes

{

default corrected;

}

Then i replace interpolationSchemes

Code:

interpolationSchemes

{

default linear;

reconstruct(rho) linearUpwind;

reconstruct(U) linearUpwind;

reconstruct(T) linearUpwind;

}

and OpenFoam gives out an error:

Code:

[3] --> FOAM FATAL IO ERROR: 

[3] Grad scheme not specified



Valid grad schemes are :



8

(

Gauss

cellLimited

cellMDLimited

extendedLeastSquares

faceLimited

faceMDLimited

fourth

leastSquares

)

Then i replace interpolationSchemes to

Code:

interpolationSchemes

{

default linear;

reconstruct(rho) Gauss linearUpwind;

reconstruct(U) Gauss linearUpwind;

reconstruct(T) Gauss linearUpwind;

}

OpenFoam gives out an error:

Code:

[17] --> FOAM FATAL IO ERROR: 

[17] Unknown discretisation scheme Gauss



Valid schemes are :



51

(

Gamma

Gamma01

MUSCL

MUSCL01

Minmod

OSPRE

QUICK

SFCD

SuperBee

UMIST

biLinearFit

blended

clippedLinear

cubic

cubicUpwindFit

downwind

filteredLinear

filteredLinear2

filteredLinear3

fixedBlended

harmonic

limitWith

limitedCubic

limitedCubic01

limitedGamma

limitedLimitedCubic

limitedLimitedLinear

limitedLinear

limitedLinear01

limitedMUSCL

limitedVanLeer

linear

linearFit

linearPureUpwindFit

linearUpwind

localBlended

localMax

localMin

midPoint

outletStabilised

quadraticFit

quadraticLinearFit

quadraticLinearUpwindFit

quadraticUpwindFit

reverseLinear

skewCorrected

upwind

vanAlbada

vanLeer

vanLeer01

weighted

)

How probably to use linearUpwind?

Thanks.

To use the linearUpwind scheme you have to specify also a gradient scheme. The correct syntax in OF-2.0.x should be (for instance):

div(phi,k) Gauss linearUpwind grad(k);

where grad(k) is the scheme specified for k in the gradSchemes section (in your case, the default cellLimited leastSquares 1 scheme will be selected).
In OF-1.7.x this syntax will not be recognized, because you have to specify explicitly the gradient scheme, like in the following example:

div(phi,k) Gauss linearUpwind cellLimited leastSquares 1;

Finally, just a note about div(tauMC): it is an explicitly calculated divergence term, not a convective flux term, thus the only scheme that makes sense is Gauss linear.

Hope this helps

V.

Thanks for your fast reply,
You tip has really helped me, but i have same questions:
If i use

Code:

interpolationSchemes

{

default linear;

reconstruct(rho) upwind cellLimited leastSquares 1;

reconstruct(U) upwind cellLimited leastSquares 1;

reconstruct(T) upwind cellLimited leastSquares 1;

}

What order of the scheme turns out, the first or the second?

Quote:

Originally Posted by Andy_bm (Post 332035)

Thanks for your fast reply,
You tip has really helped me, but i have same questions:
If i use

Code:

interpolationSchemes

{

default linear;

reconstruct(rho) upwind cellLimited leastSquares 1;

reconstruct(U) upwind cellLimited leastSquares 1;

reconstruct(T) upwind cellLimited leastSquares 1;

}

What order of the scheme turns out, the first or the second?

Actually this syntax makes no sense, because the first order upwind scheme does not need any gradient scheme specification (I think that the code will simply ignore anything you write after "upwind"). Anyway, I advice you to use something more accurate for the reconcstruction schemes, like for instance:

Code:

interpolationSchemes

{

default linear;

reconstruct(rho) Gamma 1;

reconstruct(U) GammaV 1;

reconstruct(T) Gamma 1;

}

Regards

V.

I already tried to use this:

Code:

interpolationSchemes

{

default linear;

reconstruct(rho) Gamma 1;

reconstruct(U) GammaV 1;

reconstruct(T) Gamma 1;

}

but my case has dispersing decision

my case has the decision only

Code:



interpolationSchemes

{

default linear;

reconstruct(rho) upwind;

reconstruct(U) upwind;

reconstruct(T) upwind;

}

And now I try find the scheme which will raise accuracy of the decision.

Thanks.

Quote:

Originally Posted by Andy_bm (Post 332040)

I already tried to use this:

Code:

interpolationSchemes

{

default linear;

reconstruct(rho) Gamma 1;

reconstruct(U) GammaV 1;

reconstruct(T) Gamma 1;

}

but my case has dispersing decision

my case has the decision only

Code:



interpolationSchemes

{

default linear;

reconstruct(rho) upwind;

reconstruct(U) upwind;

reconstruct(T) upwind;

}

And now I try find the scheme which will raise accuracy of the decision.

Thanks.

It depends from what you are looking for: rhoCentralFoam is designed as a transonic shock-capturing solver and the solution scheme of Tadmor and Kurganov is also constructed for this kind of flows, so using a first order scheme in my opinion introduces too much diffusion. I've noticed that sometimes rhoCentralFoam returns an oscillating behavior, but if you set the gradientScheme to a limited option (as for instance the cellLimited leastSquares 1 option) the oscillations are largely smeared out. It's up to you.

V.

I solve a problem of the expiration stream (М~2-5) in vacuum what solver can you recommend? I used sonicFoam, but he required too much time for the decision.

Quote:

Originally Posted by Andy_bm (Post 332044)

I solve a problem of the expiration stream (М~2-5) in vacuum what solver can you recommend? I used sonicFoam, but he required too much time for the decision.

rhoCentralFoam is the best OF solver for this kind of flow: just play a bit with the schemes until the (eventual) oscillations will be sufficiently small for your requirements.

V.

Thanks a lot, I will try select schemes.