Need help : natural convection in inclined convergent channel

Glare · October 21, 2012, 13:08

hello all, first of all, sorry for my bad english
im still newbie here and hope to get some help

i have some problem on inclined convergent channel system.

The system has 2 inclined wall with same temperatur (i set 332K for both wall). The bottom & top temperatur is set to 300K. The bottom side is inlet and the top side is outlet. What boundary condition should i choose for top & bottom? is that true if i set the top & bottom side of system is set to pressure outlet & pressure inlet?

In material panel, i set density properties to boussinesq, should i change its value (default value = 0)?

When i have convergence problem, i try to change the under relaxation factor, i decrease it gradually until the residual almost constant. Is there any limit value in decreasing uder relaxation factor?

Any help would be very useful to me, thanks

msaeedsadeghi · October 21, 2012, 13:31

1- Don't change fluent default values without information
2- You should define that density value. Set the density. Zero is incorrect.
3- If you have a natural convection in a closed box, all boundary conditions should be as wall.
4- Natural convection is highly sensitive to mesh size. change it to get a good result.

October 21, 2012, 13:08	Need help : natural convection in inclined convergent channel	#1
Glare New Member Join Date: Oct 2012 Posts: 1 Rep Power: 0	hello all, first of all, sorry for my bad english im still newbie here and hope to get some help i have some problem on inclined convergent channel system. The system has 2 inclined wall with same temperatur (i set 332K for both wall). The bottom & top temperatur is set to 300K. The bottom side is inlet and the top side is outlet. What boundary condition should i choose for top & bottom? is that true if i set the top & bottom side of system is set to pressure outlet & pressure inlet? In material panel, i set density properties to boussinesq, should i change its value (default value = 0)? When i have convergence problem, i try to change the under relaxation factor, i decrease it gradually until the residual almost constant. Is there any limit value in decreasing uder relaxation factor? Any help would be very useful to me, thanks

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October 21, 2012, 13:31		#2
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 15	1- Don't change fluent default values without information 2- You should define that density value. Set the density. Zero is incorrect. 3- If you have a natural convection in a closed box, all boundary conditions should be as wall. 4- Natural convection is highly sensitive to mesh size. change it to get a good result.