[YannGuyot]

Dear all,


I have a question that i suppose quiet simple but I can not find the answer.

I would like to know what type of boundary condition for temperature i should apply to a wall that is heated by a high heat source (like fire) emitting radiation?
I am able to compute the radiation flux received by the wall (with fvDOM) but I don't know how to make it heat my wall.
If any of you know how to simulate this in OpenFOAM i will really appreciate.
All the best,
Yann

[peterhess]

Hello!
I am not sure to understand your question right way...
Anyway, see the pdf here:

http://www.nextfoam.co.kr/lib/downlo...bb43ccfe025b25

and look to 4.8.

Regards

Peter

[simrego]

Hi!
You can use the following BC for example:
https://openfoam.com/documentation/g...d.html#details
For example you can use in flux mode with 0 prescribed flux. Thus your wall will be adiabatic.
This BC will create a heat flux BC based on the radiative field and you prescribed flux, thus: qwall = qPrescribed + qRad
So it will "put back" the radiative flux to the wall.

[YannGuyot]

Hello
Thank you very much for your replies,
I actually tried this BC (externalWallHeatFluxTemperature) with zero flux, but my simulations were crashing, and i didn't understand why.
Do you have working examples using this type of BC?
Cheers
Yann

[simrego]

Hi!
Sorry, now I don't have a shareable case. But if your temperature blows up, you can try to relax it in the bc somehow like this, but maybe the radiation relaxation is enough and you don't need the temperature relaxation.
Also you can decrease the relaxation of the radiative field if you feel that it will help.

<patchName>
{
    type            externalWallHeatFluxTemperature;
    mode            flux;
    q               0;
    kappaMethod     fluidThermo;
    qr              qr;
    relaxation      0.7;            //Temperature relaxation
    qrRelaxation    0.7;            //Radiation relaxation
    value           $internalField;
}

[YannGuyot]

Thank you very much, I will try it and keep you in touch!

[YannGuyot]

It works!


I tried with simulations looking like those from comsol tutorial (min 14:30) https://www.comsol.com/video/simulat...l-multiphysics
Simulation parameters are not exactly the same but I did it in a way that i could see a difference with or without this BC.
I removed the relaxation on temperature since results where physically wrong.

    {
        type            externalWallHeatFluxTemperature;
        mode            flux;
        q               0;
        kappaMethod     fluidThermo;
        qr              qr;
        qrRelaxation    0.7;
        value           $internalField;
    }

Thank very much for your help
All the best