interFoam solver needs pdRefCell?

openTom · May 9, 2009, 09:25

Hi Foamers,
i've got a question about the interFoam solver. I have implemented a new case in OpenFoam. I'm using a closed box (4 walls and empty frontAndBack) and when I'm trying to solve my case with the interFoam solver, i have to set pdRefCell and pdRefValue in the fvsolution file. Why is this neccessary? If i have a look in the damBreak test case, there isn't set a pdRefCell/pdRefValue, too. Is this because of the damBreak test case having an atmosphere boundary condition?
Thanks

ngj · May 10, 2009, 09:14

Hi Tom (?)

If you are solving the poisson equation specifying only zeroGradient type boundary conditions, then in the mathematical sense there is a unique solution _plus_ an unknown constant. This constant can only be determined (obtain a truely unique solution), by specifying the pressure at an internal located point.
In the case of the damBreak case a Dirichlet boundary condition is specified for the pressure at the atmospheric boundary, hence it is not needed to specify pdRefCell/pdRef.

Best regards,

Niels

openTom · May 10, 2009, 10:20

Hi Niels,
All right. That makes sense.
Thank you.
Tom

May 9, 2009, 09:25	interFoam solver needs pdRefCell?	#1
openTom New Member Join Date: May 2009 Posts: 13 Rep Power: 16	Hi Foamers, i've got a question about the interFoam solver. I have implemented a new case in OpenFoam. I'm using a closed box (4 walls and empty frontAndBack) and when I'm trying to solve my case with the interFoam solver, i have to set pdRefCell and pdRefValue in the fvsolution file. Why is this neccessary? If i have a look in the damBreak test case, there isn't set a pdRefCell/pdRefValue, too. Is this because of the damBreak test case having an atmosphere boundary condition? Thanks

May 10, 2009, 09:14		#2
ngj Senior Member Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Copenhagen, Denmark Posts: 1,900 Rep Power: 37	Hi Tom (?) If you are solving the poisson equation specifying only zeroGradient type boundary conditions, then in the mathematical sense there is a unique solution _plus_ an unknown constant. This constant can only be determined (obtain a truely unique solution), by specifying the pressure at an internal located point. In the case of the damBreak case a Dirichlet boundary condition is specified for the pressure at the atmospheric boundary, hence it is not needed to specify pdRefCell/pdRef. Best regards, Niels tonnykz likes this.

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May 10, 2009, 10:20		#3
openTom New Member Join Date: May 2009 Posts: 13 Rep Power: 16	Hi Niels, All right. That makes sense. Thank you. Tom