The local volumetric interfacial area transport equation: derivation and physical significance

In the two-fluid model, the closure relations for the mass, momentum and en ergy interfacial transfer terms involve the contact area between the phases per unit volume, namely the volumetric interfacial area, Ishii suggested t hat the local volumetric interfacial area should obey a transport equation. The main purpose of this paper is to derive this transport equation from g eometrical considerations. No assumption on the interface configuration is needed so that the mathematical expression obtained for the transport veloc ity is valid for any two-phase flow regime. The physical significance of th e transport velocity will be illustrated on some artificially generated bub bly flows with spherical bubbles. The link between the variables entering t he transport equation and experimentally measurable quantities will be exem plified. The measurement of the local volumetric interfacial area and its t ransport velocity can be achieved by using four-sensor probes. As a prelimi nary study of real measurements, we have assessed the performance of some e xisting signal processing methods proposed for four-sensor probes on some a rtificially generated flows. (C) 1999 Elsevier Science Ltd. All rights rese rved.