# Using vorticity utility and meaning of curl (U)

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 June 18, 2013, 11:13 Using vorticity utility and meaning of curl (U) #1 New Member   Ali Join Date: Nov 2011 Posts: 9 Rep Power: 6 Dear Foamers, I am planing to use vorticity as a post processing utility. When I hit the vorticity command in terminal the error comes up: Time = 1500 Reading U Calculating vorticity --> FOAM Warning : --> FOAM FATAL IO ERROR: keyword curl(U) is undefined in dictionary "/home/ali/run/2/system/fvSchemes::gradSchemes" 1. Is there any body explain me what the curl(U) is? 2. Is there any suggestion for the most suitable gradSchemes for curl(U) in fvSchemes? I really appreciate for any help.

 June 19, 2013, 14:58 #2 Senior Member     Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 581 Rep Power: 20 1. Curl(U) is the cross product of the vector differential operator and the velocity vector explained here 2. for grad schemes, I like least squares defined like Code: `grad(U) leastSquares;` found from here Enjoy wyldckat and immortality like this. __________________ Dan Find me on twitter @dancombest and LinkedIn

 September 27, 2013, 15:34 #3 Senior Member   Przemek Join Date: Jun 2011 Posts: 126 Rep Power: 7 hi foamers I have the same problem as aligoger. Did anybody solve this problem? best

September 27, 2013, 21:01
#4
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Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 9,659
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Greetings to all!

@gaza:
Quote:
 Originally Posted by gaza I have the same problem as aligoger. Did anybody solve this problem?
What Daniel meant is that you should edit the file "system/fvSchemes" and find the block that starts with "gradSchemes", e.g.:
Code:
```gradSchemes
{
default         Gauss linear;
}```
And add the entry for "curl(U)":
Code:
```gradSchemes
{
default         Gauss linear;
curl(U) leastSquares;
}```
Best regards,
Bruno
__________________

Last edited by wyldckat; September 27, 2013 at 21:02. Reason: grad(U) -> curl(U)

 September 28, 2013, 01:42 #5 Senior Member   Przemek Join Date: Jun 2011 Posts: 126 Rep Power: 7 Hi Bruno In fvScheme I had set up gradSchemes { default none; grad(p) Gauss linear; grad(U) Gauss linear; } Today when I changed this to gradSchemes { default Gauss linear; // grad(p) Gauss linear; // grad(U) Gauss linear; } it works. I don't know why and this is strange for me. I haven't had to set up curl(U). Very thank you for your ultra fast replay and help. best Przemek

 September 28, 2013, 01:50 #6 Senior Member   Przemek Join Date: Jun 2011 Posts: 126 Rep Power: 7 It seems that settings: default none in gradSchemes cannot be set up if I want to calculate vorticity with vorticity utility. best Przemek

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