High speed visualization of self-oscillation of axisymmetric cavitating cavity in a square vortex chamber

Abstract

Abstract An experimental investigation of the multiphase turbulent flow in a square vortex chamber was carried out to examine the self-oscillation of a cavitating cavity in a wide range of flow rates and pressure conditions. Such phenomenon is observed behind turbine runner when the hydraulic units operate at full load regime at high flowrate, and leads to significant flowrate and pressure pulsations in the entire hydraulic system. The dynamics of the cavity over time, and the freaquency of the volumetric oscillations frequency was studied via high speed visualization. The grey-scale images of the vortex cavity were binarized. By assuming an axially symmetric flow, the volume of cavity for each frame was integrated, and further investigated using FFT. Quantitative information on the structure of a single-phase flow was also obtained using the PIV technique.