FLUENT Q-Criterion

smartsoldier · April 12, 2015, 09:03

I am currently running some LES on an Ahmed Body and pulling out iso-contours of Q-criterion for vortex analysis. However, I would eventually like to move on and stop using LES in favor of a turbulence model. The problem is that when I switch from LES, Fluent no longer calculates Q-criterion for me, as in I cannot select it when I go to export or output my data. Unfortunately, Q-criterion is much more complicated than say Vorticity and cannot simply be calculated as such. Does anyone know how to get Fluent to give me Q-criterion?

`e` · April 12, 2015, 19:15

If you can't find a Fluent UDF of Q Criterion that someone has already created and posted online then you may need to create your own. Have a read of this post on Lambda-2 (similar to the Q Criterion) because they provide equations and code.

sbaffini · April 13, 2015, 04:49

You can find a custom field function for Q here:

http://www.cfd-online.com/Forums/blo...nt-part-1.html

smartsoldier · April 14, 2015, 11:15

This is exactly what I wanted, thank you so much!

April 12, 2015, 09:03	FLUENT Q-Criterion	#1
smartsoldier New Member Jacob Join Date: Apr 2014 Posts: 23 Rep Power: 12	I am currently running some LES on an Ahmed Body and pulling out iso-contours of Q-criterion for vortex analysis. However, I would eventually like to move on and stop using LES in favor of a turbulence model. The problem is that when I switch from LES, Fluent no longer calculates Q-criterion for me, as in I cannot select it when I go to export or output my data. Unfortunately, Q-criterion is much more complicated than say Vorticity and cannot simply be calculated as such. Does anyone know how to get Fluent to give me Q-criterion?

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April 12, 2015, 19:15		#2
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	If you can't find a Fluent UDF of Q Criterion that someone has already created and posted online then you may need to create your own. Have a read of this post on Lambda-2 (similar to the Q Criterion) because they provide equations and code.

April 13, 2015, 04:49		#3
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,152 Blog Entries: 29 Rep Power: 39	You can find a custom field function for Q here: http://www.cfd-online.com/Forums/blo...nt-part-1.html

April 14, 2015, 11:15		#4
smartsoldier New Member Jacob Join Date: Apr 2014 Posts: 23 Rep Power: 12	This is exactly what I wanted, thank you so much!