Unstable Flow Phenomena through a Pipe System with Cross Branch Pipe : Investigation of Flow Stabilizing Structure for Unstable Discharge Phenomena

Abstract

The stabilizing structure for the phenomenon where the flow rate of a loop with a cross pipe switches nonperiodically between a high level and a low level under certain flow conditions was investigated analytically and experimentally. With numerical analysis, a pair of vortices appeared downstream from where the axes of the main pipe and the side branches crossed. As the upstream vortex grew larger, it drifted further upstream and resulted in swirls with a high pressure loss. Conversely, when the downstream vortex grew larger, the flow became nonswirling with a low pressure loss. Two methods for stabilizing nonswirling flow were confirmed by experimentation: use of a flow diverter, and removal of the region where vortices appear by narrowing the downstream region at the cross pipe.