fvOptions - fix cellValues in cellZone with different values

Tobi · June 26, 2017, 11:48

Hi all,

just out of curiosity. Is there a way in fvOptions to fix the values at given cells (cellZone) with different values? Using scalarFixedValueConstraint enables this possibility for a cellZone, but I only can add one value which will be used for all cells. In my case I have a cellZone (arbitrary cells) which have different values. I never worked with fvOptions too much so maybe one of you knows it. If there is not such an option I might make a patch or do a dirty solution with hard-coding and using setValues for the matrix.

Tobi · July 11, 2017, 10:46

Short info. Right now it is not working. I guess it is based on the fact that the matrix should be first constructed completely and then we should manipulate it. Doing the same things after constructing the matrix works fine and as expected. Thus, I decided to make a new solver.

Thecomebackkid · November 6, 2018, 04:27

Is this also true of blue-cfd 2017 pls? I am trying to use fvOptions to make certain cellZones zero pressure and velocity within a MRF.

Tobi · November 6, 2018, 06:26

As I pointed out, I wanted to set different values for a cellZone (cellSet). So in your case it should work without problems.

Thecomebackkid · November 6, 2018, 06:45

thanks for the confirmation.

sumitverma5977 · April 10, 2021, 19:13

I am solving incompressible flow problem using pimpleFoam solver and my computational domain is a cylinder.... I have created a cellset consisting of control volume cells at the bottom periphery(i.e. cells that lie at the circumference) of the cylinder.... I wanted to fix the pressure values of those cells(or the cellset/cellZone) to 0 value throughout the simulation time.... Looking for someways to tackle the problem, i came across "scalarFixedValueConstraint" utility and using that i tries to fix the cellzZone pressure to a 0 value but it did not help..... Later i tried looking at the source code of solver "pimpleFoam"... I found that the constructor for momentum equation is created in such a way that the right hand side comprises of "fvOptions (U)"..... Although i am not sure.... As i am looking to constrain pressure values... Should it be modified to "fvOptions (p)"? Or is there any other way to fix cellzZone pressure values to 0? I would really appreciate the help if somebody would provide hints or point to a helpful resource relating to the problem at hand.... Thanks

mikulo · July 11, 2022, 04:45

Hello,

What you are trying to do is impossible. fvOptions functionality takes an argument for U and H only. However, you can make your own class but it would be so tedious. I suggest you make a code in the solver, or make a cellset and then from this cellset modify the pressure. But i don't understand why it didn't work out for you in scalarFixedValueConstraint.

Regards,
Mike

June 26, 2017, 11:48	fvOptions - fix cellValues in cellZone with different values	#1
Tobi Super Moderator Tobias Holzmann Join Date: Oct 2010 Location: Tussenhausen Posts: 2,708 Blog Entries: 6 Rep Power: 51	Hi all, just out of curiosity. Is there a way in fvOptions to fix the values at given cells (cellZone) with different values? Using scalarFixedValueConstraint enables this possibility for a cellZone, but I only can add one value which will be used for all cells. In my case I have a cellZone (arbitrary cells) which have different values. I never worked with fvOptions too much so maybe one of you knows it. If there is not such an option I might make a patch or do a dirty solution with hard-coding and using setValues for the matrix. __________________ Keep foaming, Tobias Holzmann

July 11, 2017, 10:46		#2
Tobi Super Moderator Tobias Holzmann Join Date: Oct 2010 Location: Tussenhausen Posts: 2,708 Blog Entries: 6 Rep Power: 51	Short info. Right now it is not working. I guess it is based on the fact that the matrix should be first constructed completely and then we should manipulate it. Doing the same things after constructing the matrix works fine and as expected. Thus, I decided to make a new solver. __________________ Keep foaming, Tobias Holzmann

November 6, 2018, 06:26		#4
Tobi Super Moderator Tobias Holzmann Join Date: Oct 2010 Location: Tussenhausen Posts: 2,708 Blog Entries: 6 Rep Power: 51	As I pointed out, I wanted to set different values for a cellZone (cellSet). So in your case it should work without problems. __________________ Keep foaming, Tobias Holzmann

April 10, 2021, 19:13		#6
sumitverma5977 New Member Join Date: Apr 2021 Posts: 1 Rep Power: 0	I am solving incompressible flow problem using pimpleFoam solver and my computational domain is a cylinder.... I have created a cellset consisting of control volume cells at the bottom periphery(i.e. cells that lie at the circumference) of the cylinder.... I wanted to fix the pressure values of those cells(or the cellset/cellZone) to 0 value throughout the simulation time.... Looking for someways to tackle the problem, i came across "scalarFixedValueConstraint" utility and using that i tries to fix the cellzZone pressure to a 0 value but it did not help..... Later i tried looking at the source code of solver "pimpleFoam"... I found that the constructor for momentum equation is created in such a way that the right hand side comprises of "fvOptions (U)"..... Although i am not sure.... As i am looking to constrain pressure values... Should it be modified to "fvOptions (p)"? Or is there any other way to fix cellzZone pressure values to 0? I would really appreciate the help if somebody would provide hints or point to a helpful resource relating to the problem at hand.... Thanks hhu_lulu likes this.

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November 6, 2018, 04:27		#3
Thecomebackkid New Member zeshan Join Date: Apr 2016 Posts: 24 Rep Power: 10	Is this also true of blue-cfd 2017 pls? I am trying to use fvOptions to make certain cellZones zero pressure and velocity within a MRF.

November 6, 2018, 06:45		#5
Thecomebackkid New Member zeshan Join Date: Apr 2016 Posts: 24 Rep Power: 10	thanks for the confirmation.

July 11, 2022, 04:45		#7
mikulo Member Join Date: Nov 2020 Posts: 53 Rep Power: 5	Hello, What you are trying to do is impossible. fvOptions functionality takes an argument for U and H only. However, you can make your own class but it would be so tedious. I suggest you make a code in the solver, or make a cellset and then from this cellset modify the pressure. But i don't understand why it didn't work out for you in scalarFixedValueConstraint. Regards, Mike