CFD Online Discussion Forums - buoyantBoussinesqPimpleFoam heat transfer

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buoyantBoussinesqPimpleFoam heat transfer

Hello OpenFoamers,

i am using the buoyantBoussinesqPimpleFoam solver for my simulation.
I do have a tank, in which is water at 20°C.
The tank has got a hot wall which i initialised with a fixed temperature 50°C.
But after setting my case up my hot temperature at the wall isnt going into the cold water!
I did use the hotRoom tutorial as baseCase.

Does someone know wich properties have to be set, that the wall and the water are "communicating"?

I tried to set different initial values for alpaht, nut, epsilon... but there isnt a heat flow to see.
Also i didnt manage to set externalWallheatFluxTemperature, but i think thats because it isnt usable for this incompressible solver?

I hope somebody can point me into the right direction!

Regards
GerHan

The boundary condition is by definition always communicating with the internal system.

What are you doing incorrectly? I don't know, you give too little information.

My first guess:
What do you mean by "initialise the hot wall temperature"? Didnt't you set the boundary condition there? Post your 0/T file between [code\][/code\]-marks (without the backslash of course).

Second guess:
Did you wait sufficiently long, or are you simulating a timescale shorter than the timescale of heat transfer (Fourier number)?

Thanks for your reply!

Sry i gave too less information. I was checking your guess and indeed i just didnt wait too long and my mesh was too coarse to see a changing.
i used the fixedValue and the fixedGradient BC and in both cases the watertemperature is changing.

But instead of using a groovyBC and calculating my walltemperature myself im trying now to use the wallHeatTransfer BC:

Code:

type wallHeatTransfer;

Tinf uniform 50;

alphaWall 10;

value 20;

But it isnt working. I think the problem is that i am using the incompressible buoyantBoussinesqPimpleFoam solver?? Is there a way to use this BC anyway with my solver? This is the errormessage:

Code:

--> FOAM FATAL ERROR: 



    lookup of turbulenceProperties from objectRegistry region0 successful

    but it is not a compressibleTurbulenceModel, it is a kEpsilon



     From function const Type& Foam::objectRegistry::lookupObject(const  Foam::word&) const [with Type =  Foam::ThermalDiffusivity<Foam::CompressibleTurbulenceModel<Foam::fluidThermo>  >]

    in file /home/openfoam/OpenFOAM/OpenFOAM-4.0/src/OpenFOAM/lnInclude/objectRegistryTemplates.C at line 178.



FOAM aborting

I was also trying the externalWallheatFluxTemperature BC.

Code:

{

        type            externalWallHeatFluxTemperature;

         kappaMethod     fluidThermo;

        q               uniform 500;

        thicknessLayers (0.05 0.2);

        kappaLayers     (200 0.05);

        value           uniform 293;

        kappaName       none;

        Qr              none;

        relaxation      1;

}

but it is also crashing. It says

Code:

kappa defined to employ fluidThermo method, but thermo package not available

I think this means it is looking for a thermophysicalProperties file?
I tried to implement a kappa file in the 0/ dictionary but also failed.

Im am new in Openfoam and i hope that you can bring some light in the big darkness:)

I have no experience with those BC nor with the thermo package, hence I cannot really help you.

Nevertheless, this might help you a little further until someone else replies:

(1) The following OpenFoam tutorials use the thermo package. Maybe you can have a look at them first? Some of them use the buoyantPimpleFoam solver, which is the same solver as you are using, but then without the Boussinesq approximation.

Code:

cd ${FOAM_TUTORIALS}

find . -iname "*thermo*"

(2) Your first fatal error is mentioning a turbulence model. Try to turn turbulence off (to laminar) and see what happens.

Thanks floquation for your reply!

1) thanks to your code i can see that my solver and the bouyantPimpleFoam solver both dont use the thermo package...
But i want to use the boussinesq Solver so i think i have to calculate the wall temperature with the groovy bc.

2)i will get the same error message! but instead of "it is a kEpsilon" it says "it is a laminar".
so i think it is the problem that the solver doesnt support the thermo package.
So i will just use the groovyBC.

Regards