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ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

ON THE CONSISTENCY OF MULTIFIELD FORMULATION FOR MODELING TWO-PHASE FLOW AND HEAT TRANSFER

Get access (open in a dialog) DOI: 10.1615/IHTC13.p12.540
9 pages

Abstract

A common approach to simulate multidimensional two-phase and multiphase flow and heat transfer is the use of multifield models. Although the multifield conservation equations seem to be a direct extension of those governing single-phase flows, it turns out that the averaging procedure introduces several constraints on the formulation of individual models.
The objective of this paper is to present selected theoretical and computational aspects of the interpenetrating-fluids modeling concept and its application to multiphase/multicomponent flows. The emphasis is given to a consistent formulation of ensemble-averaged conservation equations, and the associated models of interfacial phenomena between the continuous and disperse fields.
It is shown that, strictly speaking, the interpenetrating-fluids model is not applicable to dilute two-phase flows, since the dispersed field pressure is not an independent variable, nor it does appear in the generic first-principle governing equations. An explanation is also given why the use of such a model to gas/liquid flows (which has been a common practice) normally still produces acceptable results (especially for nearly fully-developed flows), provided specific conditions are satisfied concerning the formulation of the stress terms in the momentum equations for individual fields. It is demonstrated that a consistent model formulation yields a unique concentration-dependent partitioning of the local total shear stress (combined viscous and turbulent) between the interacting flow components or phases. Such a partitioning should be satisfied for any flow topologies and flow regimes, as long as the average equations are physically meaningful, although the modeling details may depend on flow patterns, geometry and other factors.
The effects of using an incorrect vs. correct model formulation on the accuracy and consistency of multiphase model predictions are also discussed.