FLOW PATTERN TRANSITION DUE TO INSTABILITY OF VOIDAGE WAVE

In order to show that the transition from bubble flow to slug flow observed in a vertical riser is due to the instability of voidage wave, an analysis and a calculation are performed on the basis of a dilute bubbly liquid model. The result demonstrates such a possibility, together with expressions for propagation velocities, growth rate and coefficient of negative diffusion. A comparison is made with the experimental result.