calcFvcGrad

Elham · March 13, 2016, 21:57

Hi,

I am simulating a droplet falling in a chamber. I need to have gradient of velocity filed in the whole domain and the corresponding coordination of them since I need to plot velocity gradient versus 3D location. I have used calcFvcGrad for Ug. As this is based on the center of cells I need to know the coordination of each cell centre. I have used writeCellCentres. But the number of cell centers are not the same as Ugs. I suppose that Ug is just for internal flow and cell centers are for the whole domain. I hope it make sense.

Thanks.

wyldckat · March 28, 2016, 15:14

Hi Elham,

Sorry, but only now did I finally manage to take a look into your questions.
Fortunately I see that you've already solved your problem on another thread of yours: http://www.cfd-online.com/Forums/ope...e-control.html

Best regards,
Bruno

Elham · March 29, 2016, 22:45

Dear Bruno,

Yes I did it. No worries.

Elham

Ananthakrishnan · April 19, 2016, 05:26

Hi

I am trying to get the shear stress profile in a cross section using stress = mu * (du/dr). Solver used is simpleFoam.

I used " calcFvcGrad " on the U field (as shown by bruno in earlier posts) which gave me 8 velocity gradients!!! But the shear stress reproduced using one of the U fields matches at the wall with the value given by "wallShearStress" tool.

My doubt is what are the 8 gradients referring to. Also please let me know if the method i followed to obtain shear stress is flawed in any manner.

I have attached the file generated by calcFvcGrad (I have added shear stress calculation in the same file)

My geometry is a concentric annulus as show below in which i need the shear stress profile in a cross section.

Thanks a lot
Regards
AK

Elham · April 22, 2016, 04:40

Dear Ak,

Just as a quick reply, I remember that all of them together construct gradient of the flowfield. If you read the header of the gradient file you will see that you have 9 components for gradient if you are doing 3 dimensional analysis of probably 4 if you are doing 2 dimensional.

Ananthakrishnan · April 22, 2016, 04:52

Hi,

Oh yes there are 9 field(0 to 8)..thanks a lot for the clarification.

Ardali · April 7, 2022, 11:19

Quote:

Originally Posted by wyldckat

Hi f0208secretx,

I was intrigued by this crash and I've finally managed to take the time to diagnose and find a fix for this problem. The bug and fix has been reported here: http://www.openfoam.org/mantisbt/view.php?id=1828

Best regards,
Bruno

Hi Bruno,

FYI: That bug still exists in OF2006
Bests,
Ardalan

April 22, 2016, 04:52		#26
Ananthakrishnan Senior Member Ananthakrishnan.A.S Join Date: Feb 2012 Location: Mumbai (Bombay), India Posts: 157 Rep Power: 16	Hi, Oh yes there are 9 field(0 to 8)..thanks a lot for the clarification. Elham likes this.

March 13, 2016, 21:57		#21
Elham Senior Member Elham Join Date: Oct 2009 Posts: 184 Rep Power: 17	Hi, I am simulating a droplet falling in a chamber. I need to have gradient of velocity filed in the whole domain and the corresponding coordination of them since I need to plot velocity gradient versus 3D location. I have used calcFvcGrad for Ug. As this is based on the center of cells I need to know the coordination of each cell centre. I have used writeCellCentres. But the number of cell centers are not the same as Ugs. I suppose that Ug is just for internal flow and cell centers are for the whole domain. I hope it make sense. Thanks.

March 28, 2016, 15:14		#22
wyldckat Retired Super Moderator Bruno Santos Join Date: Mar 2009 Location: Lisbon, Portugal Posts: 10,981 Blog Entries: 45 Rep Power: 128	Hi Elham, Sorry, but only now did I finally manage to take a look into your questions. Fortunately I see that you've already solved your problem on another thread of yours: http://www.cfd-online.com/Forums/ope...e-control.html Best regards, Bruno

March 29, 2016, 22:45		#23
Elham Senior Member Elham Join Date: Oct 2009 Posts: 184 Rep Power: 17	Dear Bruno, Yes I did it. No worries. Elham

April 22, 2016, 04:40		#25
Elham Senior Member Elham Join Date: Oct 2009 Posts: 184 Rep Power: 17	Dear Ak, Just as a quick reply, I remember that all of them together construct gradient of the flowfield. If you read the header of the gradient file you will see that you have 9 components for gradient if you are doing 3 dimensional analysis of probably 4 if you are doing 2 dimensional.