Specifying the transition Reynolds and cfx's calculation of this number

Nick R · April 3, 2011, 22:10

Hi,

My question is regarding the way the transition Reynolds number should be specified as a user defined parameter in the transition models. I read in other posts that the method CFX uses to define the length scale is thru the cube of the flow domain volume and averaged velocities. So I wonder how I can come up with a Re that is consistent with this method?

Suppose I estimate transition to occur at 1/5th of the chord on an airfoil from the leading edge. Should I simply use this length to calculate and specify Reynolds in the CFX model?

Regards,
Nick

ghorrocks · April 4, 2011, 19:27

You can specify the transition location by many ways. Not sure if you can specify a Re number, hopefully you can.

But if you know where the transition is you can just define the intermittency and define this area as laminar and that area as turbulent. Much simpler.

vidhya · April 5, 2011, 01:49

hi, i am doing simulation of multiphase flows in stirred tanks using gas-liquid.. the problem is well defined but i get some solver errors.. POPDIR, MEMER, MAKDIR.. it says some files in the crash recovery file is locked.. how to get rid of this problem?

delaneyluke · April 7, 2011, 02:31

Post some more details of the error from the .out file Vidhya. The error could be numerous things. And please start a new thread as the topic of this thread has no relation to your problem.

Regards
Luke

April 3, 2011, 22:10	Specifying the transition Reynolds and cfx's calculation of this number	#1
Nick R Senior Member Nick Join Date: Nov 2010 Posts: 126 Rep Power: 16	Hi, My question is regarding the way the transition Reynolds number should be specified as a user defined parameter in the transition models. I read in other posts that the method CFX uses to define the length scale is thru the cube of the flow domain volume and averaged velocities. So I wonder how I can come up with a Re that is consistent with this method? Suppose I estimate transition to occur at 1/5th of the chord on an airfoil from the leading edge. Should I simply use this length to calculate and specify Reynolds in the CFX model? Regards, Nick

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April 4, 2011, 19:27		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,934 Rep Power: 145	You can specify the transition location by many ways. Not sure if you can specify a Re number, hopefully you can. But if you know where the transition is you can just define the intermittency and define this area as laminar and that area as turbulent. Much simpler.

April 5, 2011, 01:49		#3
vidhya New Member Join Date: Jan 2011 Posts: 24 Rep Power: 16	hi, i am doing simulation of multiphase flows in stirred tanks using gas-liquid.. the problem is well defined but i get some solver errors.. POPDIR, MEMER, MAKDIR.. it says some files in the crash recovery file is locked.. how to get rid of this problem?

April 7, 2011, 02:31		#4
delaneyluke Senior Member Join Date: Mar 2009 Location: Indiana, US Posts: 186 Rep Power: 18	Post some more details of the error from the .out file Vidhya. The error could be numerous things. And please start a new thread as the topic of this thread has no relation to your problem. Regards Luke