Incident Radiation Intensity(G) wrong value with fireFoam

Trixalian · May 2, 2023, 10:13

Hello,

I am a new user of fireFoam (for 3-4 month) and I am trying to verify some results with basic cases of radiation.

The case is the following :
- An infinite (obtained usig symmetryPlane as boundary condition foar the side of the domain) hot plate at 2000K considered as a blackbody( $\epsilon = 1$ )
- The rest of the space is at 200K(for limitation consideration according to JANAF tables)
- The medium is non-participating (emission and absorption = 0)

In this case the analytical result of G, the incident radiation intensity, is a constant and equal to 907.2kW/m² = $\epsilon \sigma T_{plate}^{4}$
Using the fvDOM radiation model on fireFoam solver to do the radiation simulation, the result obtained is a constant but equal to 1814.8kW/m². So twice the result we should have. I Dont know where this difference comes from...

Anyone have any idea?
Thanks !

harshin · December 13, 2024, 04:43

Hi Did you figure this out? If yes could you explain what happened?

Trixalian · December 13, 2024, 05:27

Hi,

Yes I found the answer. I just misunderstood the meaning of G. It is not the same as the heat flux recieved by a cell or emmited by a plate
It is analytically : $\int_{4\pi}I_\lambda d\Omega$ and discretised in fireFOAM : $\sum_\Omega I_\lambda \Omega$ . In that peculiar case its value is $2\sigma T^4$ .

Hope it helps !

harshin · December 14, 2024, 05:34

Hello,

Thank you very much for the explanation.I found the magnitude G much higher that qr on solar radiation tutorial examples in openfoam. qr is about 1000 W/m^2 which makes sense but G is about 4 times that value. The surfaces involved in the simulation is mostly soil ground which is not very reflective.

May 2, 2023, 10:13	Incident Radiation Intensity(G) wrong value with fireFoam	#1
Trixalian New Member Join Date: Jan 2023 Posts: 2 Rep Power: 0	Hello, I am a new user of fireFoam (for 3-4 month) and I am trying to verify some results with basic cases of radiation. The case is the following : - An infinite (obtained usig symmetryPlane as boundary condition foar the side of the domain) hot plate at 2000K considered as a blackbody( $\epsilon = 1$ ) - The rest of the space is at 200K(for limitation consideration according to JANAF tables) - The medium is non-participating (emission and absorption = 0) In this case the analytical result of G, the incident radiation intensity, is a constant and equal to 907.2kW/m² = $\epsilon \sigma T_{plate}^{4}$ Using the fvDOM radiation model on fireFoam solver to do the radiation simulation, the result obtained is a constant but equal to 1814.8kW/m². So twice the result we should have. I Dont know where this difference comes from... Anyone have any idea? Thanks !

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
UDF for DOM incident radiation ( ansys fluent )	pouriyana	Fluent UDF and Scheme Programming	0	May 8, 2019 06:38
Surface integrals report: incident radiation	Novice	FLUENT	3	February 8, 2018 10:53
udf error	srihari	FLUENT	1	October 31, 2016 15:18
Monte Carlo Simulation: H-Energy is not convergating & high Incident Radiation	volleyHC	CFX	5	April 3, 2016 06:41
radiation temperature ,G(the incident radiation)	ymg	FLUENT	0	October 16, 2008 09:57

December 13, 2024, 04:43		#2
harshin New Member Harshin Kamal Asok Join Date: Aug 2017 Posts: 5 Rep Power: 9	Hi Did you figure this out? If yes could you explain what happened?

December 13, 2024, 05:27		#3
Trixalian New Member Join Date: Jan 2023 Posts: 2 Rep Power: 0	Hi, Yes I found the answer. I just misunderstood the meaning of G. It is not the same as the heat flux recieved by a cell or emmited by a plate It is analytically : $\int_{4\pi}I_\lambda d\Omega$ and discretised in fireFOAM : $\sum_\Omega I_\lambda \Omega$ . In that peculiar case its value is $2\sigma T^4$ . Hope it helps !

December 14, 2024, 05:34		#4
harshin New Member Harshin Kamal Asok Join Date: Aug 2017 Posts: 5 Rep Power: 9	Hello, Thank you very much for the explanation.I found the magnitude G much higher that qr on solar radiation tutorial examples in openfoam. qr is about 1000 W/m^2 which makes sense but G is about 4 times that value. The surfaces involved in the simulation is mostly soil ground which is not very reflective.