Domain imbalance in CHT

Studentdrak · May 1, 2012, 08:22

Hi,

I am trying to simulate a simple CHT problem.

I give a constant heat flux the base plate(with certain thickness) and a fin is attached to the base plate(as a integral part of base). Both are made of aluminium.

Air flows over the fin. Interfaces with conservative interface flux has been defined at domain interfaces.

I get a domain imbalance for H-energy for air as ~ 3% !!! and T-energy as ~0.3% .(residuals have converged)

Kindly suggest some ways to improve my soln. asap.

Thanks

stumpy · May 1, 2012, 09:10

Residuals are not a measure of global conservation. Keep running until the imbalances are reasonable (or use the Conservation Target control).

ghorrocks · May 1, 2012, 19:14

As stumpy says, you need to include imbalances in the convergence definition. CHT is the key example where imbalances are required to gauge convergence as residuals do not pick up the global imbalance.

If steady state, you probably alos need to use some solid time scale factor as well. This greatly accelerates convergence in CHT simulations.

Studentdrak · May 2, 2012, 04:21

Thanks stumpy and Glenn.

May 1, 2012, 08:22	Domain imbalance in CHT	#1
Studentdrak Member Join Date: Aug 2011 Posts: 53 Rep Power: 14	Hi, I am trying to simulate a simple CHT problem. I give a constant heat flux the base plate(with certain thickness) and a fin is attached to the base plate(as a integral part of base). Both are made of aluminium. Air flows over the fin. Interfaces with conservative interface flux has been defined at domain interfaces. I get a domain imbalance for H-energy for air as ~ 3% !!! and T-energy as ~0.3% .(residuals have converged) Kindly suggest some ways to improve my soln. asap. Thanks

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May 1, 2012, 09:10		#2
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	Residuals are not a measure of global conservation. Keep running until the imbalances are reasonable (or use the Conservation Target control).

May 1, 2012, 19:14		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	As stumpy says, you need to include imbalances in the convergence definition. CHT is the key example where imbalances are required to gauge convergence as residuals do not pick up the global imbalance. If steady state, you probably alos need to use some solid time scale factor as well. This greatly accelerates convergence in CHT simulations.

May 2, 2012, 04:21		#4
Studentdrak Member Join Date: Aug 2011 Posts: 53 Rep Power: 14	Thanks stumpy and Glenn.