Two instability criteria for the stratified flow in horizontal pipe at cocurrent flow conditions

This paper presents a theoretical approach of two instability criteria from the stratified to nonstratified flow in horizontal pipes at cocurrent flow conditions. The new theoretical instability criteria for the stratified and nonstratified flow transition in horizontal pipe have been developed by hyperbolic equations in two-phase flow. These criteria, onset of slugging criterion and critical flow condition criterion, at cocurrent flow condition correspond to imaginary and zero characteristics which occur when the hyperbolicity of a stratified two-phase flow are broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al.'s experimental data, it is shown that they are in good agreement with experimental data.