High-velocity air-water flows downstream of sluice gates including selection of optimum phase-detection probe

Abstract

High-velocity air-water flows occur commonly in hydraulic structures including low-level outlets. Novel experiments of air-water flow patterns and properties were conducted along a tunnel chute downstream of a high-head sluice gate for a wide range of flow conditions including Froude numbers between 10 and 45, Reynolds numbers up to 2.4 × 106 and flow velocities up to 22 m/s, limiting potential scale effects at close to prototype scale. The study documents the evolution of distribution shapes and characteristic values for a range of air-water flow properties along the tunnel chute. The results show an increase in flow aeration and bubble break-up processes with increasing upstream head and flow velocity. The measurement of air-water flow properties was conducted with a side-by-side double-tip conductivity probe, amongst others, which in a comprehensive comparative analysis of four types of phase-detection intrusive probe designs was identified as the most suitable one in high-velocity air-water flows as studied herein. The performance of the conductivity probe for the present flow conditions suggests that the probe may be a promising instrumentation for future prototype measurements of high-velocity air-water flows.