Experimental Study on the Mechanism of the Combined Action of Cavitation Erosion and Abrasion at High Speed Flow

A new experimental method on simulating the combined action of cavitation erosion and abrasion was proposed to investigate the erosion mechanism of overflow structure induced by the said processes. An automatic sand mixing device was invented for high-pressure and high-speed flow based on the characteristics of Venturi cavitation generator and hydraulic Bernoulli principle. The experimental system for the combined action of cavitation erosion and abrasion was designed and constructed, and high-speed sand mixing flow only appeared in the test section. A series of tests on the combined and single action of cavitation erosion and abrasion on hydraulic concrete and cement was carried out by using the invented experimental device. Results show that the wear of concrete surface exhibited the combined characteristics of cavitation erosion and abrasion under their joint action. The damage degree of concrete surface under the combined action was more severe than that under a single action. The mass loss of concrete under the combined action was higher than sum of mass losses of concrete under two single actions. The promotion and enhancement between cavitation erosion and abrasion existed in high-speed sand mixing flow. A power exponential relationship was observed between erosion mass loss and flow speed, and the velocity indexes approximated 4.5. Small and light sand particles easily follow water flow. Thus, the strong coupling effect of cavitation erosion and abrasion resulted from the presence of small sand particles. Given the different mechanisms of cavitation erosion and abrasion, presenting the skeleton structure formed by cavitation erosion was notably difficult under the action of abrasion. Meanwhile, abrasion wear easily occurred under the impact of cavitation erosion, and this result is due to the mechanism of the combined action of both processes.