pressure velocity coupling

bhargav guntreddi · July 26, 2021, 08:07

why we are using the pressure velocity coupling when we use one continuity equation and three momentum equations to calculate the u,v,w,p for incompressible flows. we have four equations and four unknowns right..? then what is the need for pressure velocity coupling?

sbaffini · July 26, 2021, 09:00

Quote:

Originally Posted by bhargav guntreddi

why we are using the pressure velocity coupling when we use one continuity equation and three momentum equations to calculate the u,v,w,p for incompressible flows. we have four equations and four unknowns right..? then what is the need for pressure velocity coupling?

Well, continuity equation is not for pressure per se. So, if you want to solve for pressure (and not for density), you are formally missing an equation.

FMDenaro · July 26, 2021, 09:23

Quote:

Originally Posted by bhargav guntreddi

why we are using the pressure velocity coupling when we use one continuity equation and three momentum equations to calculate the u,v,w,p for incompressible flows. we have four equations and four unknowns right..? then what is the need for pressure velocity coupling?

I am not sure if your question is about the theoretical coupling for the incompressible flow model in contunuous form or you are asking for the numerical fomulations (that is why pressure or density-based solver) chosen to solve.

LuckyTran · July 26, 2021, 10:18

Pressure doesn't have its own independent equation where you can solve purely for pressure. Pressure appears in the momentum equation and is coupled with the velocity. They are coupled.

If you are asking why we need to use specifically SIMPLE to solve for pressure and velocity, you do not always have to use SIMPLE. You can use coupled solvers that solve simultaneously for pressure and velocity.

July 26, 2021, 08:07	pressure velocity coupling	#1
bhargav guntreddi New Member bhargav Join Date: Jul 2021 Posts: 2 Rep Power: 0	why we are using the pressure velocity coupling when we use one continuity equation and three momentum equations to calculate the u,v,w,p for incompressible flows. we have four equations and four unknowns right..? then what is the need for pressure velocity coupling?

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July 26, 2021, 10:18		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	Pressure doesn't have its own independent equation where you can solve purely for pressure. Pressure appears in the momentum equation and is coupled with the velocity. They are coupled. If you are asking why we need to use specifically SIMPLE to solve for pressure and velocity, you do not always have to use SIMPLE. You can use coupled solvers that solve simultaneously for pressure and velocity.