Circumferential Velocity Component

L_W · June 18, 2014, 06:07

Hi,

can somebody tell me how to calculate the circumferential velocity from the cartesian components (u,v,w)? I Don't want to use the turbo-mode because I want to use this expression in order to calculate the circumferential components of other flow parameters later on in Post.

Thanks a lot and kind reguards

ghorrocks · June 18, 2014, 06:39

You could define a new coordinate frame.

You could define a new 3D vector variable, and do the transformation from the default cartesian coords to any coord system you like.

L_W · June 18, 2014, 07:10

Thanks for your fast replay.

Can you explain this in detail? When I try to define a new frame in post, this is a cartesian frame as well.
For the transformation I have the expression
v_circumferential=-cos(Theta)* Velocity u + sin(Theta) * Velcoty w
(X and Z are my radial axis in the cartesian reference frame).
When I compare this to the Circumferential Velocity in the turbo-mode I don't get the same results.

ghorrocks · June 18, 2014, 18:49

You probably have the equation wrong. Don't forget you also have the axial, circum and radial unit vectors and lots of other ways to calculate it.

Jane92 · July 12, 2015, 05:30

Hi
I wonder if you find the method to calculate the circumferential velocity from the cartesian components (u,v,w)。Now I face the same question with you！

Thanks a lot and kind reguards

ghorrocks · July 12, 2015, 06:00

You could define a coordinate frame and get CFX to work it out for you. Or you could do it using some maths. Your choice.

Jane92 · July 12, 2015, 07:54

thanks for your replay！
I find only the Cartesian coordinate could be defined in CFX-Post。and can you
explain in details of the maths

ghorrocks · July 12, 2015, 08:01

Quote:

explain in details of the maths

When I get paid to write posts on this forum I will explain the maths in detail.

In the meantime, I will refer you to references like:

http://mathworld.wolfram.com/Cylindr...ordinates.html
https://en.wikipedia.org/wiki/Cylind...rdinate_system
http://tutorial.math.lamar.edu/Class...calCoords.aspx

singer1812 · July 13, 2015, 10:43

You have another job besides writting responses on this forum? Who Knew!??!!

ghorrocks · July 13, 2015, 18:55

It can be difficult fitting paid work in between typing all the posts sometimes.

June 18, 2014, 06:07	Circumferential Velocity Component	#1
L_W New Member Lars Wein Join Date: Jun 2012 Posts: 8 Rep Power: 13	Hi, can somebody tell me how to calculate the circumferential velocity from the cartesian components (u,v,w)? I Don't want to use the turbo-mode because I want to use this expression in order to calculate the circumferential components of other flow parameters later on in Post. Thanks a lot and kind reguards Jane92 likes this.

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June 18, 2014, 06:39		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You could define a new coordinate frame. You could define a new 3D vector variable, and do the transformation from the default cartesian coords to any coord system you like.

June 18, 2014, 07:10		#3
L_W New Member Lars Wein Join Date: Jun 2012 Posts: 8 Rep Power: 13	Thanks for your fast replay. Can you explain this in detail? When I try to define a new frame in post, this is a cartesian frame as well. For the transformation I have the expression v_circumferential=-cos(Theta)* Velocity u + sin(Theta) * Velcoty w (X and Z are my radial axis in the cartesian reference frame). When I compare this to the Circumferential Velocity in the turbo-mode I don't get the same results.

June 18, 2014, 18:49		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You probably have the equation wrong. Don't forget you also have the axial, circum and radial unit vectors and lots of other ways to calculate it.

July 12, 2015, 05:30		#5
Jane92 New Member meizhenwang Join Date: Jul 2015 Posts: 5 Rep Power: 10	Hi I wonder if you find the method to calculate the circumferential velocity from the cartesian components (u,v,w)。Now I face the same question with you！ Thanks a lot and kind reguards

July 12, 2015, 06:00		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You could define a coordinate frame and get CFX to work it out for you. Or you could do it using some maths. Your choice.

July 12, 2015, 07:54		#7
Jane92 New Member meizhenwang Join Date: Jul 2015 Posts: 5 Rep Power: 10	thanks for your replay！ I find only the Cartesian coordinate could be defined in CFX-Post。and can you explain in details of the maths

July 13, 2015, 10:43		#9
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	You have another job besides writting responses on this forum? Who Knew!??!!

July 13, 2015, 18:55		#10
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	It can be difficult fitting paid work in between typing all the posts sometimes.