关键词: 水力学, 高速水流, 空蚀, 含沙量, 混凝土试件

Abstract: The effect of sediment concentration on cavitation erosion in high velocity flows is studied experimentally in a small looped water tunnel. First, we prepare artificially sediment-laden flows with low, moderate and high concentrations in the inner tank of the tunnel, and measure the volume concentration using an infrared suspended solid analyzer. Pressure in the cavitation erosion zone at different concentrations is measured using a dynamic pressure acquisition system. Then, we use concrete specimens of different concrete ages and different mix proportions and install them in the cavitation zone and cavitation erosion zone separately. An erosion and abrasion test run takes five hours and the weight loss per hour is used as the cavitation erosion rate and abrasion rate. The experimental results show that at a grain diameter of d50 = 1.09 mm and concentration of S = 0 ~ 30 kg/m3, time-averaged pressure and cavitation number in the cavitation erosion zone rise with an increase in concentration, promoting the occurrence of cavitation erosion. With mix proportion and age fixed, cavitation erosion intensifies with an increase in concentration, and the eroded area expands. The anti-cavitation erosion capacity of specimens with a higher strength is greater than that with a lower strength at different concentrations; the greater increase in concentration, the greater difference in the capacity. Prolonging cure time of a concrete specimen enhances its anti-cavitation erosion capacity at different concentrations. For the same test time, the abrasion rate of a concrete specimen is much smaller than its cavitation erosion rate, indicating cavitating action far stronger than sediment abrasion action in high velocity sediment-laden flows.

Key words: hydraulics, high-velocity flow, cavitation erosion, sediment concentration, concrete specimen