# Vorticity Direction

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 March 4, 2008, 09:15 Vorticity Direction #1 Sham Guest   Posts: n/a Hi all, I am simulating an oscillating cylinder and observing the vorticities. Does anyone know how to view the velocity in which the clock wise and anti clockwise vorticity direction gives you diff colour in the contour plot? This will make it easy to differentiate between positive and negative vorticity direction. Sham

 March 4, 2008, 23:47 Re: Vorticity Direction #2 NRD Guest   Posts: n/a Hello, Your question is not entirely clear to me. However, if you want to look at the direction in which the vortices are rotating (i.e. whether clockwise or counter-clockwise) why not plot the velocity vectors?

 March 7, 2008, 01:58 Re: Vorticity Direction #3 John Young Guest   Posts: n/a Hi Sham, I'm assuming your problem is 2D, where fluent only provides the vorticity magnitude. To get around this you can define a Custom Field Function (see sect 30.5.1 of the user guide) for the vorticity which is du/dy - dv/dx. John

 March 22, 2008, 04:41 Re: Vorticity Direction #4 Sham Guest   Posts: n/a John, Could you pls explain a little bit more how can I use the Custom Field Function to define the vorticity direction and show it in diff colour? I am modelling a 2D cylinder in free stream. Sham.

 March 24, 2008, 17:15 Re: Vorticity Direction #5 John Young Guest   Posts: n/a Hi Sham, Go to the "Define" menu, pick "Custom Field Function". Then in the "Field Functions" drop-down box, pick "Derivatives", select "dX-Velocity/dy" from the second drop-down box, click "Select", then the "-" button, then select "dY-Velocity/dx" and click "Select". Now choose a name for your new variable (e.g. "Vorticity-signed"), then click "Define". When you go to plot contours, choose "Custom Field Functions", and your new variable will be available. Note that most of the vorticity will be in the boundary layer, so you will probably have to take it off "Auto Range" and pick some lower values to see anything at all in the wake. Positive values represent rotation in one direction, negative values in the other. Hope that helps, John bestniaz, saas1y12@soton.as.uk, rajann_786 and 1 others like this.

 March 25, 2008, 00:08 Re: Vorticity Direction #6 Sham Guest   Posts: n/a John, Thanks a lot. It works. Sham.

 May 19, 2011, 16:27 VORTICITY calculation in unstructured grid? #7 New Member   anil Join Date: Jul 2010 Location: india Posts: 3 Rep Power: 8 I have one doubt regarding the vorticity calculation in FLUENT. In a forum i found the vorticity calculation is by du/dy-dv/dx. But this is valid for structured mesh only according to theory and how can it be valid for unstructured grids. Is there any method (Algorithm) by which Fluent calculates the vorticity for unstructured grid?.

 January 9, 2016, 03:43 #8 New Member   Rajendra Singh Join Date: Aug 2015 Posts: 11 Rep Power: 3 To, John Young Thanks!!! It is helpful.

 May 24, 2016, 06:01 #9 New Member   anonymous Join Date: Nov 2015 Posts: 4 Rep Power: 2 Thank You John I lost my 3 weeks finding how to do this.. finally you made my day

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