Asymmetric Solid–Liquid Two-Phase Flow around a NACA0012 Cascade in Sediment-Laden Flow

Abstract

Sediment abrasion may cause the removal of material and efficiency loss to hydraulic machinery (hydro-turbine, pump, etc.), which may worsen the internal flow and endanger the safe operation of the machines. As abrasion is caused by the impact of sediment on the solid surface, the movement of particles determines the wear intensity. To understand the wear mechanism of hydraulic machinery, the motion characteristics of the asymmetric solid–liquid two-phase flow in a sediment-laden flow around NACA0012 cascades were studied. The laser particle imaging velocimetry (PIV) method was used to measure the flow of quartz particles with median diameters d50 of 82.7 μm, 65.9 μm, and 31.8 μm near the wall of cascades at an impact angle of 10° in a Venturi circuit. The flow characteristics and velocity slip between solid and liquid phases, as well as the effects of particle size and the Reynolds number on velocity slip, were analyzed. The results showed that: (1) the flow is asymmetrically distributed in front of the cascade’s leading edge at a 10° impact angle, and there is strong velocity slip between solid and liquid phases; (2) under the influence of particle inertia, the velocity of the solid phase is higher than that of the liquid phase in the deceleration stage, while the velocity of the solid phase is lower than that of liquid phase in the acceleration stage; (3) in the process of approaching the leading edge, the velocity difference between the solid and liquid phase increases by about 10% and the angle difference increases by about 8.8°.