Multiple steady state with same boundary conditions

faisal_durr · July 13, 2011, 05:45

Hello,

I am looking at Natural ventilation inside buildings. I have read many papers where for the same geometry of the building they acquire multiple steady states of the final ventilation flow. Experimentally they observe such phenomena by repeating the experiment a couple of times. I am now using LES to simulate such multiple steady states. Can some one advice me how to acquire them using LES? I mean if I run LES once on a geometry I will get one steady state right? But how do I get the other steady states for the same boundary conditions? Thank you

stumpy · July 13, 2011, 10:08

LES is always transient. To get the "steady state" result you could collect variable averages using transient statistics. Collecting the averages over sequential time periods would give multiple "steady state" results.

faisal_durr · July 13, 2011, 20:07

Thank you stumpy for your helpful reply. I am collecting transient averages of velocity, temp and pressure. When you said "collecting the averages of sequential time periods" what exactly did you mean. I mean I am running a simulation of lets say 0 to 100 sec. I will get transient averages in cfx-post for the full 0-100sec. Then what did you mean by "collecting the averages of sequential time periods"??? Thank you.

July 13, 2011, 05:45	Multiple steady state with same boundary conditions	#1
faisal_durr Member Faisal Durrani Join Date: Nov 2009 Location: England Posts: 62 Rep Power: 16	Hello, I am looking at Natural ventilation inside buildings. I have read many papers where for the same geometry of the building they acquire multiple steady states of the final ventilation flow. Experimentally they observe such phenomena by repeating the experiment a couple of times. I am now using LES to simulate such multiple steady states. Can some one advice me how to acquire them using LES? I mean if I run LES once on a geometry I will get one steady state right? But how do I get the other steady states for the same boundary conditions? Thank you

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July 13, 2011, 10:08		#2
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	LES is always transient. To get the "steady state" result you could collect variable averages using transient statistics. Collecting the averages over sequential time periods would give multiple "steady state" results.

July 13, 2011, 20:07		#3
faisal_durr Member Faisal Durrani Join Date: Nov 2009 Location: England Posts: 62 Rep Power: 16	Thank you stumpy for your helpful reply. I am collecting transient averages of velocity, temp and pressure. When you said "collecting the averages of sequential time periods" what exactly did you mean. I mean I am running a simulation of lets say 0 to 100 sec. I will get transient averages in cfx-post for the full 0-100sec. Then what did you mean by "collecting the averages of sequential time periods"??? Thank you.