HeatFlux in buoyantBoussinesq

ubaid · November 16, 2010, 14:41

Quote:

Originally Posted by David_010

Hi ubaid

snGrad is the gradient normal to a surface. The gradient term can be evaluated in different manners, and in the case of the temperature gradient at the wall, the heat flux expression q=k(DT/DX) employs the gradient normal to that wall, so snGrad is the correct way.

I suggest you to take a look to the Programmers Guide, I think it explains this better than me.

Hope it helps, regards

David

Hallo David,

Thanks a lot, i got what you meant. I will look at manual closely.

Best Regards,

sarahk · March 8, 2011, 09:35

Hey Foamers,

i just tried the turbulentHeatFluxTemperature bc in the buoyantBoussinesqPimpleFoam tutorial case with OF-1.7.1.
I exchanged all the kappaEff with alphaEff. Its reading all the files, starts the time loop and breaks up directly. i got a:

--> FOAM FATAL ERROR:
request for volScalarField unifrom from objectRegistry region0 failed
available objects ot type volScalarField are

do i need to add a field in createFields?
Thought its ok, when i just add a value in the 0/T file ...

Any suggestions?

Thanks in advance!

Sarah

Anne Lincke · August 17, 2011, 09:20

Dear Foamers,
can someone explain me why OF1.7 still uses

HTML Code:
- ghf*fvc::snGrad(rhok)*mesh.magSf()
instead of

HTML Code:
fvc::interpolate(rhok)*(g & mesh.Sf())
as it was used in the previous version OF1.6.
I do not understand why the gradient of the densitiy is used while in the equations I find in literature it has to be just the densitiy multiplied with the constant g.
Can someone help me? Is this still a bug or do I overlook something?
Also in the Wiki-Link
http://openfoamwiki.net/index.php/Bu...sinesqPisoFoam
they use the interpolated density instead of the surface normal gradient.

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March 8, 2011, 09:35		#22
sarahk New Member Sarah Köhler Join Date: Jun 2010 Location: Leoben Posts: 11 Rep Power: 15	Hey Foamers, i just tried the turbulentHeatFluxTemperature bc in the buoyantBoussinesqPimpleFoam tutorial case with OF-1.7.1. I exchanged all the kappaEff with alphaEff. Its reading all the files, starts the time loop and breaks up directly. i got a: --> FOAM FATAL ERROR: request for volScalarField unifrom from objectRegistry region0 failed available objects ot type volScalarField are do i need to add a field in createFields? Thought its ok, when i just add a value in the 0/T file ... Any suggestions? Thanks in advance! Sarah

August 17, 2011, 09:20		#23
Anne Lincke Senior Member Anne Gerdes Join Date: Aug 2010 Location: Hamburg Posts: 168 Rep Power: 15	Dear Foamers, can someone explain me why OF1.7 still uses HTML Code: - ghffvc::snGrad(rhok)mesh.magSf() instead of HTML Code: fvc::interpolate(rhok)*(g & mesh.Sf()) as it was used in the previous version OF1.6. I do not understand why the gradient of the densitiy is used while in the equations I find in literature it has to be just the densitiy multiplied with the constant g. Can someone help me? Is this still a bug or do I overlook something? Also in the Wiki-Link http://openfoamwiki.net/index.php/Bu...sinesqPisoFoam they use the interpolated density instead of the surface normal gradient.