Boundarys for Heat Convection in chimney

hotti24 · November 23, 2016, 08:24

Hello Guys,

lets say I have chimney styled geometry with a heat source basically like in the picture.

How would you set the boundary conditions? I cannot reach a stable simulation. I tried to set the lower inlet to inlet-outlet for velocity and the pressure to 0, and the upper outlet to inlet-outlet for velocity and the pressure to different things but nothing worked fine. Is it possible that i have to set it to p = roh_air * g* high?

The task is the simulation of the free convection flow through the pipe.

Thank you very much!
Hendrik

gkarlsen · November 23, 2016, 09:15

Did you try totalpressure=0 for P in both ends. Possibly combined with pressureInletOutletVelocity for U? As the fluid flows faster the inlet losses will increase until the pressure difference cancel out the "drive" caused by the heat source. At this point you have the steady state condition.

You did not mention which solver you are using, but I assume it is one that can handle buoyancy?

November 23, 2016, 08:24	Boundarys for Heat Convection in chimney	#1
hotti24 New Member Hendrik Join Date: Jul 2013 Location: Germany Posts: 9 Rep Power: 13	Hello Guys, lets say I have chimney styled geometry with a heat source basically like in the picture. How would you set the boundary conditions? I cannot reach a stable simulation. I tried to set the lower inlet to inlet-outlet for velocity and the pressure to 0, and the upper outlet to inlet-outlet for velocity and the pressure to different things but nothing worked fine. Is it possible that i have to set it to p = roh_air * g* high? The task is the simulation of the free convection flow through the pipe. Thank you very much! Hendrik

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November 23, 2016, 09:15		#2
gkarlsen Member Geir Karlsen Join Date: Nov 2013 Location: Norway Posts: 59 Rep Power: 14	Did you try totalpressure=0 for P in both ends. Possibly combined with pressureInletOutletVelocity for U? As the fluid flows faster the inlet losses will increase until the pressure difference cancel out the "drive" caused by the heat source. At this point you have the steady state condition. You did not mention which solver you are using, but I assume it is one that can handle buoyancy?