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compressibility-NavierStokesEqutations in buoyantFOAM?

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Old   June 18, 2009, 12:04
Default compressibility-NavierStokesEqutations in buoyantFOAM?
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hi everybody!

i' ve got a quick question about the equations of buoyantFoam,
i realize that most buoyant flows can be treated incompressible..

I understand that I technically solve compressible Navier Stokes equations, however i am slightly confused about the pressure correction procedure with pdyn.
is this just a way of introducing a sort of artificial compressibility and when this equation is solved put back into the momentum equation (->correct)?
I solve for rho, U, h and pdyn (and turb. properties) in that order. So the pressure correction term has an effect in the next time step for U.Eqn & h.Eqn?

many thanxx for your help!!:-)
thomas
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Old   June 19, 2009, 09:46
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The effect of pressure correction is the same as in incompressible flow: enforce continuity.
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Old   June 20, 2009, 05:15
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thanks for your reply!

so i understand I solve the NavStokEquations in the compressible state (if UEqn would contain p_total, UEqn. would be the same form as e.g. in sonicFOAM)
and that the pressure correction acts on just the dynamic pressure (not total) to enforce continuity but still for the compressible system

the only thing that still confuses me is that basically all buoyant flows CFD I have seen so far was run incompressible
maybe I still make a mistake in understanding the solver

thanks
thomas
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Old   June 20, 2009, 07:45
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Pressure is dicomposed as:
P = PRef + Pd + rho * g * h

PRef is a constant, dpRef/dx =0, so it does not show up in momentum equation.

-dp/dx = - dpd/dx - grad(rho)*g*h - rho*grad(rho*h)

The last term is canceled out with rho*g term in the momentum equation.

What you are really solving is compressible equation with gravity term in the momentum equation.

Hope it helps.
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