How to calculate the gradient at a boundary patch

xiaofishnus · April 28, 2015, 05:14

It seems that grad() function can only calculate the gradient of the scalar at the cell center.

snGrad() is just for a normal gradient at boundary, which returns a scalar but not vector as grad() does.

Is any function in OF can directly calculate the gradient of a scalar for a boundary patch?

Thanks.
xiaofish

ybapat · April 28, 2015, 07:23

Hello,

I am not sure if you can get direct gradient instead of surface normal gradient at the boundary. But you can get gradient at the adjacent cell by taking cell ID of the adjacent cell.

Regards,
-Yogesh

rapierrz · April 30, 2015, 12:53

Hello,

You can compute gradient of a scalar with paraView :

filters --> alphabetical ---> compute derivatives

April 28, 2015, 05:14	How to calculate the gradient at a boundary patch	#1
xiaofishnus New Member Join Date: Oct 2014 Posts: 9 Rep Power: 13	It seems that grad() function can only calculate the gradient of the scalar at the cell center. snGrad() is just for a normal gradient at boundary, which returns a scalar but not vector as grad() does. Is any function in OF can directly calculate the gradient of a scalar for a boundary patch? Thanks. xiaofish Pagoda and rajibroy like this.

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April 28, 2015, 07:23		#2
ybapat Senior Member Yogesh Bapat Join Date: Oct 2010 Posts: 102 Rep Power: 17	Hello, I am not sure if you can get direct gradient instead of surface normal gradient at the boundary. But you can get gradient at the adjacent cell by taking cell ID of the adjacent cell. Regards, -Yogesh

April 30, 2015, 12:53		#3
rapierrz Senior Member Hesam Join Date: Feb 2015 Posts: 139 Rep Power: 12	Hello, You can compute gradient of a scalar with paraView : filters --> alphabetical ---> compute derivatives