Theoretical analysis of interfacial instability in a countercurrent annular two-phase flow

A small disturbance analysis is applied to an instability of a liquid-gas interface in a countercurrent annular two-phase flow, considering the curvature of the interface and viscosity and velocity distributions in liquid and gas phases. The analysis indicates that the average velocity, velocity distribution, and viscosity of liquid film significantly affect the instability criterion. Comparison of the present analysis with existing analyses of Hewitt and Imura, in which the viscous effect was neglected, indicates that the viscosity produces two critical boundaries classifying stable and unstable regions instead of the one boundary predicted in the existing analysis. (author)