High-pressure submerged cavitation jet is widely used in the fields of material peening, petroleum drilling, and ocean engineering. The impact performance of the jet with intensive cavitation is related to the factors such as working condition and the nozzle geometry. To reveal the relationship between the nozzle divergent angle and the jet pressure on the unsteady characteristics of the jet, high-speed photography with frame rate of 20000 fps is used to record the image of the cavitation clouds. Grayscale analysis algorithm developed in MATLAB is used to study the effects of injecting condition on the special structure, unsteady characteristics, and shedding frequency of the cavitation bubbles. The impact load characteristics of the cavitation jet with different cavitation numbers and stand-off distances are recorded using a high-response pressure transducer. It is found that the cavitation number is the main factor affecting the cavitation morphology of the submerged jet. The lower the cavitation number is, the more intense the cavitation occurs. The outlet divergent angle of the convergent-divergent nozzle also has a significant influence on the development of the cavitation clouds. In the three nozzles with the outlet divergent angles of 40°, 80°, and 120°, the highest bubble concentration is formed usinga nozzle with a divergent angle of 40°, but the high-concentration cavitating bubbles are only distributed in a very small range of the nozzle outlet. The cavities generated by using the nozzle with a divergent angle of 80° can achieve good results in terms of concentration and distribution range, while the nozzle with divergent angle of 120° has lower cavitation performance due to the lack of the constraint at the outlet which intensifies the shear stress of the jet. According to the result of frame difference method (FDM) analysis, the jet cavitation is mainly formed in the vortex structure generated by the shearing layer at the nozzle exit, and the most severe region in the collapse stage is the rear end of the downstream segment after the bubble cloud sheds off. The impact load of the cavitation jet is mainly affected by the stand-off distance of the nozzle from the impinged target, while the nozzle outlet geometry also has an effect on the impact performance. Optimizing the stand-off distance and the outlet geometry of the nozzles is found to be a good way to improve the performance of the cavitation jet.

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高压潜水空化射流的非定常特性和冲击性能的实验研究

高压潜空化射流广泛应用于材料喷丸，石油钻探和海洋工程领域。强烈气蚀的射流的冲击性能与诸如工作条件和喷嘴几何形状等因素有关。为了揭示喷嘴发散角与射流压力之间的关系，射流的不稳定特性，使用帧率为20000 fps的高速摄影记录了空化云的图像。用MATLAB开发的灰度分析算法研究了注入条件对空化气泡的特殊结构，非定常特性和脱落频率的影响。使用高响应压力传感器记录具有不同空化次数和间隔距离的空化射流的冲击载荷特性。发现空化数是影响潜水射流空化形态的主要因素。空化数越低，发生的空化越剧烈。收敛-发散喷嘴的出口发散角也对空化云的发展有重要影响。在出口发散角分别为40°，80°和120°的三个喷嘴中，使用发散角为40°的喷嘴可形成最高的气泡浓度，但高浓度的空化气泡仅分布在很小的范围内喷嘴出口范围。使用发散角为80°的喷嘴产生的腔体在浓度和分布范围方面均能获得良好的结果，而发散角为120°的喷嘴由于缺乏出口约束而具有较低的空化性能。增强了射流的剪切应力。根据帧差法（FDM）分析的结果，射流空化主要形成在喷嘴出口处剪切层产生的涡旋结构中，塌陷阶段最严重的区域是下游段的后端。泡泡云散下后。空化射流的冲击载荷主要受喷嘴与撞击目标之间的距离的影响，而喷嘴出口的几何形状也对冲击性能产生影响。