Obtain local volume at node/vertex in user routine

honcho62 · January 18, 2016, 05:22

Hi again

I am assigning momentum to a certain number of nodes in a fluid domain. That momentum needs to be adjusted for how much the volume at that node inhabits the volumes of all nodes that have momentum assigned to them.

I have a FOR/DO loop, in a Fortran User Routine, that assigns these nodes their momentum. So I have been looking for a way to call up the volume that is related to X(ILOC),Y(ILOC),Z(ILOC). However, the routines I can find for Fortran such as USER_GET_MESH_INFO use the counter NVX, referring to total number of vertices. So the question is, are the vertices from that routine arranged the same way as X,Y,Z from ARGS(). Or ILOC = NVX

I know I could also call volcvol in CEL in CFX pre, but I need to know the total sum first, so I don't think it's a good idea to put this in CFX pre as such.

ghorrocks · January 18, 2016, 06:14

Aren't source terms defined as per unit volume? If so then you don't need to adjust for cell volumes.

honcho62 · January 18, 2016, 06:54

That may be so, but you're only applying this force on a small volume within the domain. And this smaller volume consists of several cells, so you'd have to distribute the force over these cells in a way that it would be a singular cell. It's not so much about dimension, more about fraction.

ghorrocks · January 18, 2016, 07:07

So if you get the total volume of the source from a CEL expression then you can get the per unit volume source and apply it as a constant source term.

honcho62 · January 18, 2016, 07:50

Pretty much, so I need an equivalent Volume term for X(ILOC) etc that I can use in Fortran, the subroutine that I mentioned seems useful but it uses a different counter so I'm not sure if for the same index they refer to the same vertex.

ghorrocks · January 18, 2016, 18:14

If you have not already guessed, I am not very familiar with fortran in CFX so cannot directly answer your question. Maybe somebody else on the forum knows CFX fortran better than I and can answer your question.

But maybe my alternate approach can work - if you calculate the total volume as a CEL expression, then access that variable in fortran you can calculate the total volume that way.

honcho62 · January 19, 2016, 07:39

Quote:

Originally Posted by ghorrocks

If you have not already guessed, I am not very familiar with fortran in CFX so cannot directly answer your question. Maybe somebody else on the forum knows CFX fortran better than I and can answer your question.

But maybe my alternate approach can work - if you calculate the total volume as a CEL expression, then access that variable in fortran you can calculate the total volume that way.

I'm aware, but thanks for all the help anyway. I put the post up there in the hope someone would know.

That might be a solution, but only if you can hold of the calculation of the force until it's done with the volume expression. I'll try it out, thanks!

January 18, 2016, 05:22	Obtain local volume at node/vertex in user routine	#1
honcho62 Member Join Date: Jan 2016 Posts: 34 Rep Power: 10	Hi again I am assigning momentum to a certain number of nodes in a fluid domain. That momentum needs to be adjusted for how much the volume at that node inhabits the volumes of all nodes that have momentum assigned to them. I have a FOR/DO loop, in a Fortran User Routine, that assigns these nodes their momentum. So I have been looking for a way to call up the volume that is related to X(ILOC),Y(ILOC),Z(ILOC). However, the routines I can find for Fortran such as USER_GET_MESH_INFO use the counter NVX, referring to total number of vertices. So the question is, are the vertices from that routine arranged the same way as X,Y,Z from ARGS(). Or ILOC = NVX I know I could also call volcvol in CEL in CFX pre, but I need to know the total sum first, so I don't think it's a good idea to put this in CFX pre as such. snowquote likes this.

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January 18, 2016, 06:14		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Aren't source terms defined as per unit volume? If so then you don't need to adjust for cell volumes.

January 18, 2016, 06:54		#3
honcho62 Member Join Date: Jan 2016 Posts: 34 Rep Power: 10	That may be so, but you're only applying this force on a small volume within the domain. And this smaller volume consists of several cells, so you'd have to distribute the force over these cells in a way that it would be a singular cell. It's not so much about dimension, more about fraction.

January 18, 2016, 07:07		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	So if you get the total volume of the source from a CEL expression then you can get the per unit volume source and apply it as a constant source term.

January 18, 2016, 07:50		#5
honcho62 Member Join Date: Jan 2016 Posts: 34 Rep Power: 10	Pretty much, so I need an equivalent Volume term for X(ILOC) etc that I can use in Fortran, the subroutine that I mentioned seems useful but it uses a different counter so I'm not sure if for the same index they refer to the same vertex.

January 18, 2016, 18:14		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	If you have not already guessed, I am not very familiar with fortran in CFX so cannot directly answer your question. Maybe somebody else on the forum knows CFX fortran better than I and can answer your question. But maybe my alternate approach can work - if you calculate the total volume as a CEL expression, then access that variable in fortran you can calculate the total volume that way.