Transient growth in two-phase mixing layers ( submitted )

Transient growth properties are computed for a two-phase temporal mixing layer of immiscible incompressible
Newtonian fluids with interfacial tension.  Large transient growth factors are found to occur at short times in
parameter regimes characteristic of the primary breakup of a liquid. Optimal growth factors scale with the
square of the Reynolds number, as for single phase flow.  The flow fields of optimal disturbances show liquid
up-flows and high speed streamwise gas jets occuring together near the interface, suggesting transient growth
as a possible mechanism for the formation of interfacial patterns.

Optimal growth occurs for streamwise uniform disturbances with a spanwise wavelength proportional to the
thickness of the gas boundary layer.  For a coaxial jet, the predicted number of ligaments would be inversely
proportional to the gas boundary layer thickness.