VELOCITY MEASUREMENTS IN CAVITATING FLOWS USING FAST X-RAY IMAGING

Abstract

A promising method to measure velocity fields in complex two-phase flows such us cavitating flows is presented. Dynamics of the liquid phase and the bubbles are both investigated. The measurements are based on ultra fast X-ray imaging performed at the APS (Advanced Photon Source) of the Argonne National Laboratory. The experimental device consists of a millimetric Venturi test section associated with a transportable hydraulic loop. Various configurations of velocity, pressure, and temperature have been investigated. Radio-opaque particles are used as tracers for the liquid phase, in association with a multipixel sensor to record the successive positions of the particles. The use of X-rays instead of light solves the problems related to light reflection and dispersion on phase boundaries, since X-rays penetrate a gas/liquid flow in straight lines. Images contain simultaneously the information related to the particles (for PIV analysis in the liquid), to the vapour bubbles (for PIV in the gas). The slip velocity between vapour and liquid is calculated.