PEqnflux in compressible and incompressible PISO loop

dbxmcf · October 7, 2008, 11:58

Hi, all:

I have a question about the pEqn.flux() in the PISO loop, for the incompressible(icoFoam) case, after solving the pressure correction equation:

phi -= pEqn.flux();

while in the compressible case (sonicFoam),

phi = pEqn.flux();

My understanding is the incompressible flow is just a special case for the compressible flow (rho=const), no matter the pressure correction equation looks like. Can anyone explain the difference for the two cases?

Thanks a lot!

David1 · July 11, 2015, 16:21

Hi Roy,

Did you eventually found your answer? Because I have the same question you have/had.

Thank you!

AshwaniAssam · September 27, 2019, 02:14

Did it get resolved? Because I do not see anywhere else in OpenFOAM except in the sonicFOAM this term

phi = pEqn.flux();

without any addition or subtraction.

Is it right?

AshwaniAssam · September 27, 2019, 07:13

I found the answer here: PISO Details

In sonicFoam
the ".flux()" function returns the influence of all implicit terms on the flux. In this case everything is implicit, so you can assign it like that
phi = pEqn.flux();

So, what I understand is that .flux() operator gives the flux terms of the equation which are handled implicitly.

October 7, 2008, 11:58	Hi, all: I have a question	#1
dbxmcf Member roy fokker Join Date: Mar 2009 Posts: 44 Rep Power: 17	Hi, all: I have a question about the pEqn.flux() in the PISO loop, for the incompressible(icoFoam) case, after solving the pressure correction equation: phi -= pEqn.flux(); while in the compressible case (sonicFoam), phi = pEqn.flux(); My understanding is the incompressible flow is just a special case for the compressible flow (rho=const), no matter the pressure correction equation looks like. Can anyone explain the difference for the two cases? Thanks a lot!

September 27, 2019, 02:14		#3
AshwaniAssam Senior Member Ashwani Join Date: Sep 2013 Location: Hyderabad Posts: 154 Rep Power: 13	Did it get resolved? Because I do not see anywhere else in OpenFOAM except in the sonicFOAM this term phi = pEqn.flux(); without any addition or subtraction. Is it right? Last edited by AshwaniAssam; September 27, 2019 at 02:15. Reason: Typos correction

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July 11, 2015, 16:21		#2
David1 New Member België/Belgique Join Date: Jul 2015 Posts: 3 Rep Power: 11	Hi Roy, Did you eventually found your answer? Because I have the same question you have/had. Thank you!

September 27, 2019, 07:13		#4
AshwaniAssam Senior Member Ashwani Join Date: Sep 2013 Location: Hyderabad Posts: 154 Rep Power: 13	I found the answer here: PISO Details In sonicFoam the ".flux()" function returns the influence of all implicit terms on the flux. In this case everything is implicit, so you can assign it like that phi = pEqn.flux(); So, what I understand is that .flux() operator gives the flux terms of the equation which are handled implicitly.