# derivative definition of velocity IN CFX

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 21, 2016, 05:30 derivative definition of velocity IN CFX #1 Senior Member   Aja Join Date: Nov 2013 Location: Hungary Posts: 380 Rep Power: 6 Hi, How do i can define velocity derivative as follow: Thanks. Best. Aja

 April 21, 2016, 06:44 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,456 Rep Power: 104 u.grad_x and so on for uvw and xyz. Look in the CFX reference manual for the full list of variables, functions and operators on variables (like the gradient function). aja1345 likes this.

April 21, 2016, 09:41
#3
Senior Member

Aja
Join Date: Nov 2013
Location: Hungary
Posts: 380
Rep Power: 6
Quote:
 Originally Posted by ghorrocks u.grad_x and so on for uvw and xyz. Look in the CFX reference manual for the full list of variables, functions and operators on variables (like the gradient function).
Thanks,

Should I define in Expressions? or user functions?

I want to obtain a contour by using above function in post 1.

 April 21, 2016, 10:25 #4 Senior Member   Aja Join Date: Nov 2013 Location: Hungary Posts: 380 Rep Power: 6 I created as follows: Now, How can i call this formula in contour panel? I want to obtain a contour by using defined function. Rotary is whole computational domain. Method is single reference frame. in Fact, i rotate whole computational domain. What is "Value=0.00490041"? Last edited by aja1345; April 22, 2016 at 15:55.

 April 21, 2016, 10:38 #5 Senior Member   Aja Join Date: Nov 2013 Location: Hungary Posts: 380 Rep Power: 6 I was wrong. I created a new variable in expression panel as follows: And then volume integral : It is ok, but now How do i obtain a contour by using variable RRR? There is variable RRR in contour panel: Last edited by aja1345; April 22, 2016 at 08:48.

 April 21, 2016, 12:25 #6 Senior Member   Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 640 Rep Power: 13 For contours, you can only plot variables, not expressions. You must create a new variable. And then maker the definition of that variable your expression. aja1345 likes this.

April 21, 2016, 15:57
#7
Senior Member

Aja
Join Date: Nov 2013
Location: Hungary
Posts: 380
Rep Power: 6
Quote:
 Originally Posted by evcelica For contours, you can only plot variables, not expressions. You must create a new variable. And then maker the definition of that variable your expression.
Thanks.

According the following picture, i created new variable(VVV). Right?

But, the contour of new variable(VVV) is not very good and clear, there are not different colors in the following contour of this new variable. why?

Thanks

Last edited by aja1345; April 22, 2016 at 05:12.

April 22, 2016, 02:27
#8
Senior Member

Maxim
Join Date: Aug 2015
Location: Germany
Posts: 342
Rep Power: 4
Quote:
 Originally Posted by aja1345 But, the contour of new variable(VVV) is not very good and clear, there are different colors in the following contour of this new variable. why?
Isn't that the goal of contour plots? Getting different colors according to the range of your variable? 1000 colors of contours is a bit much, maybe start with 50 or so

you probably need to adjust your color range. 'local' is a good first shot but a lot of times you still too coarse. You probably know in which range your values should be - so start with that range. Something like min= 0 , max=10. Or min=10, max= 100. Etc.

April 22, 2016, 02:32
#9
Senior Member

Maxim
Join Date: Aug 2015
Location: Germany
Posts: 342
Rep Power: 4
Quote:
 Originally Posted by aja1345 What is "Value=0.00490041"?
In this case you already 'applied' your equation to a specific surface and that's why you got a result (=value). CFX solved that volume integral of your equation on surface ROTARY

 April 22, 2016, 06:21 #10 Senior Member   Aja Join Date: Nov 2013 Location: Hungary Posts: 380 Rep Power: 6 Thanks. Now I want to export this contour to tecplot format. there was tecplot format in Fluent(for exporting), but i dont see this format in CFX. I am grateful that guide me about this case.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post rystokes CFX 2 January 11, 2010 18:17 diluom CFX 7 December 10, 2009 23:50 ed CFX 1 November 8, 2006 17:03 Lichun Dong FLUENT 6 December 8, 2005 12:09 zonexo Main CFD Forum 2 September 27, 2005 03:02

All times are GMT -4. The time now is 20:40.