wallHeatFlux with radiation

fxzf · October 16, 2017, 17:30

Hi Everyone,

I got a bit trouble in Openfoam with heat transfer problem. Basically, I need to specify heatflux boundary condition which is same with Fluent. However, I didn't find this boundary condition in standard Openfoam. I found a "externalWallHeatFluxTemperature", but that is for compressible flow with solid. My case is incompressible flow with buoyantboussinesqsimplefoam solver.

Then, luckily, I download a wallHeatFlux boundary condition from foam contribution.
https://openfoamwiki.net/index.php/Contrib/wallHeatFlux

However, this one is not included radiation. So, I test it for radiation off case, the results is almost identical with Fluent.

Then, I added radiation in it. So basically, I just added qr in the equation

gradient() = (HeatFlux_ - qr_)/(alphaEffW * Cp0.value() * rho0.value() );

The code is working when radiation on. However, it then crashed very soon as G (radiation incident), T temperature are goto very high number like E100 then crashed.

Does anyone know anything about Heatflux boundary condition to give me any suggestion?

Thanks a lot.

fxzf · October 25, 2017, 12:55

Hi Guys,

I added relexation factor for qr in this case, and it then working. However, the relaxation factor is related to qr magnitude when qr is high, very low relaxation is needed like 1E-5. However, this will make simulation converge very very slow.

Does anyone has any idea to improve convergence?

Thanks a lot.

October 16, 2017, 17:30	wallHeatFlux with radiation	#1
fxzf Member ff Join Date: Feb 2010 Posts: 81 Rep Power: 16	Hi Everyone, I got a bit trouble in Openfoam with heat transfer problem. Basically, I need to specify heatflux boundary condition which is same with Fluent. However, I didn't find this boundary condition in standard Openfoam. I found a "externalWallHeatFluxTemperature", but that is for compressible flow with solid. My case is incompressible flow with buoyantboussinesqsimplefoam solver. Then, luckily, I download a wallHeatFlux boundary condition from foam contribution. https://openfoamwiki.net/index.php/Contrib/wallHeatFlux However, this one is not included radiation. So, I test it for radiation off case, the results is almost identical with Fluent. Then, I added radiation in it. So basically, I just added qr in the equation gradient() = (HeatFlux_ - qr_)/(alphaEffW * Cp0.value() * rho0.value() ); The code is working when radiation on. However, it then crashed very soon as G (radiation incident), T temperature are goto very high number like E100 then crashed. Does anyone know anything about Heatflux boundary condition to give me any suggestion? Thanks a lot.

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October 25, 2017, 12:55		#2
fxzf Member ff Join Date: Feb 2010 Posts: 81 Rep Power: 16	Hi Guys, I added relexation factor for qr in this case, and it then working. However, the relaxation factor is related to qr magnitude when qr is high, very low relaxation is needed like 1E-5. However, this will make simulation converge very very slow. Does anyone has any idea to improve convergence? Thanks a lot.