A Study of Swirling Backflow and a Vortex Structure in the Inlet of an Inducer

Abstract

This paper presents a vortex structure at the inlet of an inducer which appears on the boundary of backflow regions. The vortex structure was visualized using vortex cavitations by operating at cavitation number σ=0.050 and recorded by a high speed video. The vortex structure was also observed by using two laser displacement sensors. An FFT analyzer couldn't be used to determine the passing frequency because the periodicity of vortex passage is very weak, i. e., rather irregular. The passing frequency and the shape of vortex lines were determined by counting the pulse from laser displacement sensors which responds to the passage of vortex cavitation. The results show that the number of vortices, its strength, its travelling velocity are functions of flow coefficient and depend on a steady flow velocity profile.