Instability of finite amplitude waves: Transition from stratified to slug flow

Two-phase flow--air flow over inviscid and incompressible wavy water--in a rectangular horizontal channel is analyzed to determine the characteristics of the transition from stratified to slug flow.; Theoretical stability analysis in two-phase flow on the transition from stratified to slug flow was based on irrotational flow where potential functions represented the flows. Real processes (flows) and especially that of air over water are rotational and expectedly this condition may drastically affect the stability criterion. The measurement of pressure distribution along the wave profile reflects the realistic interfacial conditions. In this work, real air pressure distribution is used and an analytical study of nonlinear instability of finite amplitude waves in two-phase flow is conducted using a numerical method approach to obtain a new criterion for Kelvin-Helmholtz instability. This instability is checked and found to exist in the neighborhood of the wave crest as proposed by previous researchers.