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Noel July 23, 2008 10:54

Pressure correction in two-phases flow
Dear all, In single-phase flow, Phoenics will use the continuty equation to correct the pressure and velocity obtain from momentum equation. In one of Phoenics document, it writes that the phase continuity equation (for each phase) is used to compute the volume fraction of the corresponding phase.

The arising questions : 1. How does then Phoenics carry out the pressure correction if all continuity equations have been used for the computation of volume fraction ? 2. Where does Phoenics use the total fraction (e.g. for two-phases, r1 + r2 = 1).

Looking forward to hearing from you all. Thank's in advance

Regards, Noel

mike July 23, 2008 11:29

Re: Pressure correction in two-phases flow
In PHOENICS, the option exists to solve for r1 and r2, or alternatively, to solve for either r1 or r2 with the remaining volume fraction determined from the requirement that the two volume fractions sum to unity.

The overall continuity equation (pressure correction) is used to correct the pressure, which is shared by both phases.

For details of the precise procedure, refer to published accounts of the IPSA (InterPhase Slip Analyser). There are various variants of IPSA in the literature, but the original method is documented here:

D B Spalding (1983), 'Numerical Computation of Multiphase Flow and Heat-transfer', Contribution to 'Recent Advances in Numerical Methods in Fluids', pp 139-167 Eds. C Taylor & K Morgan, Pineridge Press, Swansea.

D B Spalding (1981), 'Numerical computation of multi-phase flows',Imperial College Lecture Course, London, 2-6 Nov. CFDU Report, (1981).

Noel July 23, 2008 11:55

Re: Pressure correction in two-phases flow
Thank's very much Mike.

You mentioned the options : 1. to solve for r1 and r2 2. to solve for either r1 or r2

If I choose the first option, does Phoenics still use the unity sum of the volume fractions ? If so, then it will be overdetermined.


mike July 23, 2008 12:03

Re: Pressure correction in two-phases flow
As I recall, the volume fractions are scaled so as to enforce overall continuity.

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