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fvc::ddtPhiCorr(rUA, U, phi)

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Old   January 23, 2011, 09:42
Default fvc::ddtPhiCorr(rUA, U, phi)
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ata kamyabi
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Hi FOAMers
can any one tell me fvc::ddtPhiCorr(rUA, U, phi) in icoFoam code is for what?
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Old   January 24, 2011, 13:05
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Hi, take a look of:

Programming questions

and

DdtPhiCorr

Best.
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Old   January 24, 2011, 23:02
Default fvc::ddtPhiCorr(rUA, U, phi)
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Thank you very much
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Old   August 19, 2011, 22:29
Post http://www.openfoam.com/mantisbt/print_bug_page.php?bug_id=169
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the term Phi in UEqn and PEqn is not exactly the same:
In the UEqn: corrected flux from the previous iteration or timestep,
In the PEqn: mass flux without the pressure contribution.

The term ddtPhiCorr checks for the dimensional units of U and phi to decide what operation has to be performed, and if phi is defined in terms of mass, a division of phi by rho is performed.

This represents a problem in the case of zero density. Such a case cannot happen in single-phase flows, however it might happen in multiphase flows. For example, let's consider a momentum equation in the form

ddt(alpha*rho*U) + div(alpha*rho*U*U) = ...

where alpha is the phase fraction. The equation is then represented in the code as

fvm::ddt(alphaRho, U) + fvm::div(alphaf*phi, U) == ...

being phi = rho_f * (U_f \cdot S). In such a case, if my understanding is correct, one should compute

surfaceScalarField phi =
fvc::interpolate(rho)*(fvc::interpolate(U) & mesh.Sf())
+ fvc::ddtPhiCorr(rUA, rhoAlpha, U, phi)

At this point, since alpha can be zero, ddtPhiCorr will cause a division by zero.

This does not represent a problem in the incompressible case, since the equation can be divided by rho, which leads phi to be a volumetric flux, and ddtPhiCorr would be ddtPhiCorr(rUA, alpha, U, phi). However, if one wants to deal with the compressible case, keeping equations in conservative form, the problem appears.
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Old   August 21, 2011, 03:54
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The problem is known and was reported (I guess you read it since you pasted it :P):

http://www.openfoam.com/mantisbt/view.php?id=169
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Old   September 10, 2011, 12:47
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Quote:
Originally Posted by alberto View Post
The problem is known and was reported (I guess you read it since you pasted it :P):

http://www.openfoam.com/mantisbt/view.php?id=169

Yes alberto
I referenced to the link you've mentiond in the title of my post!!!
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Old   February 7, 2013, 23:10
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Hi FOAMERS
I have modified SIMPLEFOAM for unsteady flows bu adding ddt(U) to the U matrix. Do I also have to add fvc::ddtPhiCorr in PEqu.H to calculate fluxes? How ignoring this term will affect my results?
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