Vortex Breakdown Phenmena in a Circular Pipe : 2nd Report, Flow Modes of Unsteady Type Breakdowns

Abstract

It has been reported by many other authors that the vortex breakdown phenomena may occur in several distinct types. The aim of this study is to obtain a reasonable and consistent explanation for the various flow patterns of breakdowns. In the preceding report, we have pointed out that the breakdown phenomena depend greatly upon the occurrence of internal waves within a swirling flow field, and also that the type of breakdown so far reported corresponds to an azimuthal mode of the wave disturbance. The preceding paper, however, treated only steady(time-independent) types of breakdowns. The present paper concerns unsteady(or periodicwith time) types of breakdowns. It is found that the time-dependency of breakdown has a close relation to the phase velocity of the wave disturbance.