Pressure based solver question

Tobiasrpr · February 2, 2012, 13:50

Hello,

Regarding the predictor-corrector family of methods (SIMPLE, SIMPLEC etc), can someone tell me the purpose of the velocity predictor step? Are there any methods which are based on only pressure correction, without velocity prediction? Any pointer to relevant literature will be much appreciated.

Regards.

leflix · February 2, 2012, 16:52

Hi Tobias,

Start to have a look to this here
http://www.cfd-online.com/Wiki/Veloc...ssure_coupling

then read the book of patankar
"numerical heat transfer and heat flow"

and follow with
"Computational fluid dynamics" from Ferziger-Peric

You will find your answers.

For incompressible flows velocity and pressure are deeply coupled. You can not correct one without correcting the other.

FMDenaro · February 3, 2012, 12:05

As said, pressure in incompressible flows is not a thermodinamic variable and you have no equations governing it (it is a Lagrangian multiplier)... as well, scalar pressure is not a variable to be solved, you need to solve for a gradient of a suitable scalar function that ensures the divergence-free constraint. Solving for the "pressure" equation is therefore equivalent to solve the continuity equation. The relation between such a gradient and the real pressure gradient depends on the method.

February 2, 2012, 13:50	Pressure based solver question	#1
Tobiasrpr New Member Join Date: Feb 2012 Posts: 1 Rep Power: 0	Hello, Regarding the predictor-corrector family of methods (SIMPLE, SIMPLEC etc), can someone tell me the purpose of the velocity predictor step? Are there any methods which are based on only pressure correction, without velocity prediction? Any pointer to relevant literature will be much appreciated. Regards.

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February 2, 2012, 16:52		#2
leflix Senior Member Join Date: Aug 2011 Posts: 272 Rep Power: 15	Hi Tobias, Start to have a look to this here http://www.cfd-online.com/Wiki/Veloc...ssure_coupling then read the book of patankar "numerical heat transfer and heat flow" and follow with "Computational fluid dynamics" from Ferziger-Peric You will find your answers. For incompressible flows velocity and pressure are deeply coupled. You can not correct one without correcting the other.

February 3, 2012, 12:05		#3
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,764 Rep Power: 71	As said, pressure in incompressible flows is not a thermodinamic variable and you have no equations governing it (it is a Lagrangian multiplier)... as well, scalar pressure is not a variable to be solved, you need to solve for a gradient of a suitable scalar function that ensures the divergence-free constraint. Solving for the "pressure" equation is therefore equivalent to solve the continuity equation. The relation between such a gradient and the real pressure gradient depends on the method.