泥沙颗粒级配对高速水流空化空蚀的影响

在小型循环式水洞中试验研究了非黏性沙颗粒级配对高速水流空化空蚀的影响。首先，在循环式水洞内筒中配制8种泥沙小于某粒径不同重量百分比(P<2%、12%、33%、47%、56%、70%、86%、100%)的挟沙水样，用红外测沙仪测定了挟沙水样的含沙量。利用压力数据采集系统实时量测了泥沙小于某粒径不同重量百分比P下水洞工作段(空化区、空蚀区)的压力；其次，试验采用不同强度混凝土试件，在相同含沙量S、小于某粒径不同重量百分比P的工况下，进行历时4 h的空蚀破坏试验。试验结果表明：在含沙量S=12 kg/m³，喉部流速V=38.6 m/s条件下，空化区测点压力随小于某粒径重量百分比P的增大而降低，促进了空化的发生；空蚀区测点压力则随小于某粒径重量百分比P的增大而升高，增强了空蚀的强度；混凝土试件强度相同时，混凝土试件的空蚀量随泥沙小于某粒径重量百分比的增大而增加；保持含沙量S和小于某粒径重量百分比P不变，高强度(f_cu=17.8 MPa)混凝土试件的抗空蚀能力明显比低强度(f_cu=13.7 MPa)试件高。

Effect of sediment gradation on cavitation erosion in high velocity flows

Effects of non-cohesive sediment grain gradation on cavitation erosion in high velocity flows is studied experimentally in a small looped water tunnel. First, eight non-cohesive sediment samples of different gradations are prepared in the inner tank of the tunnel－weight percentages smaller than a certain grain size of P < 2%, 12%, 33%, 47%, 56%, 70%, 86%, 100%; Sediment concentration is measured using an infrared suspended solid analyzer. A dynamic pressure data acquisition system is adopted to measure real-time the pressure in the tunnel working section, including the cavitation zone and cavitation erosion zone in the condition of eight sediment gradations. Second, concrete specimens with different strengths are used for the tests of erosion of 4 hours long under the condition of the same concentration S and different sediment gradations. The results show that at S = 12 kg/m3 and throat flow velocity V = 38.6 m/s, an increase in weight percentage P lowers the pressure in the cavitation zone, promoting the occurrence of cavitation; but it raises the pressures in the erosion zone, enhancing cavitation erosion. At a fixed strength of concrete specimens, their cavitation erosion intensifies with an increase in P; at fixed values of S and P, a specimen with a higher strength (fcu = 17.8 MPa) presents a greater cavitation erosion resistance than that with a lower strength (fcu = 13.7 MPa).