distance between two vortex

saeedabedi · June 6, 2013, 06:51

Hi all

I am attempting to calculate distance between two vortxes behind a submarine by using ansys cfx.
This distance is calculated by vorticity contour (contour of velocity curl in cfx post). Distance between stream lines is also calculated. Why this two distance is different and non equal?

Cheers,

Saeed

ghorrocks · June 6, 2013, 07:32

I do not understand what you are asking. Are you asking why is a vorticity contour a different distance apart compared to some streamlines?

saeedabedi · June 6, 2013, 17:11

I am need to obtain distance between two vortexes due to flow over a submarine.
I think that this distance can obtain from vorticity contour or 2D streamline in cfx post that this two value (value from vorticity contour and value from 2D stremline on plane perpendicular to submarine) must be equal. but result from vorticity contour is not equal to 2D streamline. why?

ghorrocks · June 6, 2013, 19:27

An image would help.

But it seems pretty obvious that the vorticity approach and the streamline approach are defining the distance differently and therefore return different values. Why do you expect them to be the same?

saeedabedi · June 7, 2013, 07:10

I think that location of vorticity is where that streamline rotate.

below image of streamlie
CFX0.6.jpg

below image of vorticity contour
CFX10.7.jpg

ghorrocks · June 10, 2013, 22:33

Your mesh looks very coarse. Have you tried a finer mesh?

June 6, 2013, 06:51	distance between two vortex	#1
saeedabedi New Member saeed Join Date: Apr 2013 Posts: 4 Rep Power: 13	Hi all I am attempting to calculate distance between two vortxes behind a submarine by using ansys cfx. This distance is calculated by vorticity contour (contour of velocity curl in cfx post). Distance between stream lines is also calculated. Why this two distance is different and non equal? Cheers, Saeed

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June 6, 2013, 07:32		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	I do not understand what you are asking. Are you asking why is a vorticity contour a different distance apart compared to some streamlines?

June 6, 2013, 17:11		#3
saeedabedi New Member saeed Join Date: Apr 2013 Posts: 4 Rep Power: 13	I am need to obtain distance between two vortexes due to flow over a submarine. I think that this distance can obtain from vorticity contour or 2D streamline in cfx post that this two value (value from vorticity contour and value from 2D stremline on plane perpendicular to submarine) must be equal. but result from vorticity contour is not equal to 2D streamline. why?

June 6, 2013, 19:27		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	An image would help. But it seems pretty obvious that the vorticity approach and the streamline approach are defining the distance differently and therefore return different values. Why do you expect them to be the same?

June 7, 2013, 07:10		#5
saeedabedi New Member saeed Join Date: Apr 2013 Posts: 4 Rep Power: 13	I think that location of vorticity is where that streamline rotate. below image of streamlie CFX0.6.jpg below image of vorticity contour CFX10.7.jpg

June 10, 2013, 22:33		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Your mesh looks very coarse. Have you tried a finer mesh?