Natural Convection

muzair · September 7, 2015, 21:22

Hi All,

I am dealing with buoyancy driven convective heat loss from a cavity by using CFX with the help of 2 different turbulence models (SST and Spalart Allmaras) through a cavity. The cavity is vertical and the opening is downward. I tried to solve this problem with steady state but the results are too high and even they are not converging properly. In transient simulation, can anyone guide me:

1) How I can predict either my simulation is now moving toward steady state or not?
2) how to check the steady state values of heat flux or convective heat loss through cavity, when doing transient simulation?
3) Should I take the average of any value for whole simulation time or for specific time period?

Regards

ghorrocks · September 7, 2015, 21:40

1) Many free convection flows end up with large scale transient flow features. You cannot capture this with a steady state model. Try running transient.

2) Use a monitor point. This works for steady state flows as well.

3) If the large scale transient flows exist like I refer to in 1) then you cannot reproduce this with a steady state flow. You need to run it transient.

September 7, 2015, 21:22	Natural Convection	#1
muzair New Member Muhammad Uzair Join Date: Aug 2014 Posts: 3 Rep Power: 11	Hi All, I am dealing with buoyancy driven convective heat loss from a cavity by using CFX with the help of 2 different turbulence models (SST and Spalart Allmaras) through a cavity. The cavity is vertical and the opening is downward. I tried to solve this problem with steady state but the results are too high and even they are not converging properly. In transient simulation, can anyone guide me: 1) How I can predict either my simulation is now moving toward steady state or not? 2) how to check the steady state values of heat flux or convective heat loss through cavity, when doing transient simulation? 3) Should I take the average of any value for whole simulation time or for specific time period? Regards Last edited by muzair; September 7, 2015 at 21:32. Reason: Question was not too clear

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September 7, 2015, 21:40		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,692 Rep Power: 143	1) Many free convection flows end up with large scale transient flow features. You cannot capture this with a steady state model. Try running transient. 2) Use a monitor point. This works for steady state flows as well. 3) If the large scale transient flows exist like I refer to in 1) then you cannot reproduce this with a steady state flow. You need to run it transient.