Acoustics and hydrodynamics of a drop impact on a water surface

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• 作者：Yu. D. Chashechkin ; V. E. Prokhorov
• 关键词：impact pulse ; underflow ; gas cavity ; detachment ; resonance ; acoustic packet ; emission instability
• 刊名：Acoustical Physics
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：63
• 期：1
• 页码：33-44
• 全文大小：
• 刊物类别：Physics and Astronomy
• 刊物主题：Acoustics;
• 出版者：Pleiades Publishing
• ISSN：1562-6865
• 卷排序：63

文摘

Hydrodynamic and acoustic processes associated with a drop impact on a water surface were studied experimentally. Acoustic signals were detected underwater (with a hydrophone) and in air (with a microphone), the flow pattern was recorded with a high-speed camera, and the surface perturbation was monitored with a laser detector. The dimensionless parameters of flows (Reynolds, Froude, and Weber numbers) induced by the impact varied with fall height within the ranges of 5000 < Re < 20000, 20 < Fr < 350, and 70 < We < 1000. The sequence of acoustic signals incorporated an impact pulse at the moment of contact between a drop and the surface and a series of acoustic packets attributable to the resonance emission of gas cavities. The top of the impact pulse, which was detected clearly in the entire fall height range, had a complex structure with short high-frequency and longer low-frequency oscillations. The total number and the parameters of emitted acoustic packets depended to a considerable extent on the fall height. The cases of lacking, one-time, and repeated emission of packets were noted in a series of experiments performed at a constant fall height. The analysis of video data showed that the signal variability was induced by considerable differences in the scenarios of water entry of a drop, which assumed an ovoid shape at the end trajectory segment, in the mentioned experiments.