涡流
物理
空化
机械
涡流环
绳子
雷诺数
起动涡流
经典力学
湍流
结构工程
工程类
作者
Deyou Li,Zhipeng Ren,Liang Yu,Qi Yang,Hongjie Wang
出处
期刊:Physics of Fluids
[American Institute of Physics]
日期:2021-10-01
卷期号:33 (10)
被引量:14
摘要
Cavitation vortex rope widely occurs in hydraulic machinery, leading to the decrease in performance characteristic and increase in pressure fluctuation. The objective of this study was to explore the generation and transformation of cavitation vortex ropes in a swirling flow. A visual swirling-flow generator platform was designed to investigate their spatiotemporal evolution mechanism. A flow pattern observation system with a high-speed camera was built to capture the vortex rope forms, and pressure fluctuation experiments were carried out to present fluctuating characteristics of corresponding cavitation vortex ropes. Cavitation vortex rope forms and pressure fluctuation characteristic under different operating conditions were exhibited. Four types of stable cavitation vortex ropes (broken, dual, single, and subulate) were observed. Regional distribution of vortex ropes under different Reynolds and cavitation numbers was characterized, which showed that broken and subulate vortex ropes account in large Reynolds and cavitation ranges. Pressure fluctuation analyses revealed dominant characteristic frequencies were 2.13, 1.98, 1.74, and 1.93 times the rotational frequency of the runner for the broken, dual, single, and subulate cavitation vortex ropes, respectively. In addition, two unstable transitions were identified during the conversion process. One is an unstable transitional triple-vortex rope during from a dual- to single-vortex rope process, and the other is an unstable subulate-vortex rope between the occurrence of the single- and stable subulate-vortex ropes. The present study could give a deep understanding of the generation of cavitation vortex ropes and provide some references to improve the hydraulic instabilities induced by cavitation vortex ropes in hydraulic machinery.
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