Effect of miscibility on the linear instability of two-fluid channel flow

This study provides an extension into the finite-miscibility regime of theories for interfacial instabilities in two-fluid channel flow. When the two fluids are of high mass diffusivity, a new mode of instability, called here the overlap mode, appears when the critical layer of the dominant disturbance overlaps the viscosity-stratified layer. For poor diffusivity, the instability is qualitatively different: broadband and at low Reynolds number, beginning to resemble the Yih mode for immiscible interfaces. The results lend themselves to verification by experiment and direct numerical simulation. (C) 2004 Elsevier Ltd. All rights reserved.