Sound generation as a drop falls on a water surface

Prokhorov, V. E.; Chashechkin, Yu. D.

doi:10.1134/s1063771011050137

Cited by 19 publications

(8 citation statements)

References 14 publications

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“…Additional time scales can be large when the influence of diffusion effects is important, and are sufficiently small when a rapid release of the available potential energy takes place, for example, due to annihilation of free liquid surface when different fluids merge. Diffusion effects generate long-living structural features, and energetic short time phenomena produce high frequency flow components (for example, short capillary waves and sound when falling drops impact on a liquid surface [17,18]). The additional free parameters complicate the picture of the process and make it difficult to develop universal methods for flow calculations.…”

Section: Concept Of "Fluid Flow"mentioning

confidence: 99%

Differential Fluid Mechanics—Harmonization of Analytical, Numerical and Laboratory Models of Flows

Chashechkin

2015

Computational Methods in Applied Sciences

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Concepts of a "solid body motion" and "fluid flow" are compared taking into account the condition of inobservability of a "fluid particle". General properties of the fundamental set of fluid mechanics equations, accepted for describing fluid flows, are analyzed taking into account the compatibility condition. Hierarchy of periodic flows is classified basing on the order of linearized set of governing equations. Results of theoretical analysis of infinitesimal periodic flows in a stably stratified fluid including periodic internal waves and accompanied family of small scale components are given. Calculations of periodic internal waves propagation and generation in a fluid with arbitrary stable profile of buoyancy are compared with data of schlieren observations in laboratory. Fine flow structure observed behind uniformly towing strip is discussed in context of a given model. Some conclusions and recommendations on improvement techniques of a fluid dynamics experiment are presented.

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Section: Concept Of "Fluid Flow"mentioning

confidence: 99%

Differential Fluid Mechanics—Harmonization of Analytical, Numerical and Laboratory Models of Flows

Chashechkin

2015

Computational Methods in Applied Sciences

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“…In the twenties of the last century, accompanying sound signals were recorded initially in the air [3], and with the development of measurement techniquesin the aquatic environment [4]. Improving the technique for visual registration of flow patterns [5] and acoustic signal parameters [6], the development of computer technology and programming made possible the increase of the sensitivity, temporal and spatial resolution of measuring systems, and to distinguish new stably reproducible features of the ongoing processes.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics, Energetics and Acoustics of Free Falling Drop Impact at a Motionless Fluid

Chashechkin¹,

Prokhorov²

2020

Topical Problems of Fluid Mechanics 2020

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The results of coordinated studies of the flow structure and acoustic signals generated in a fluid at rest by a freely falling drop of clean or dye colored water are presented. Highresolution video recording of the flow revealed the structure of plane ejecta, spikes, droplets sprays cavity, splash, secondary cavity, streamer, secondary droplets and sequence of capillary waves. Recurrence of the fine structure as the appearance of fast fine spikes after decay of initial perturbations on the free surface was observed in the center of the cavity and at the head of a growing splash. Groups of capillary waves accompanied the formation and elimination of every structure componentsplash, separating drop and coming back. A measuring hydrophone and a sensitive microphone measured acoustic signals consisting of a high-frequency pulse of the primary contact and a delayed lower-frequency packet(s). The relative poverty of the acoustic signal indicates that from a large number of observed gas bubbles only one, the formation of which included the break of a thin air bridge, was actually sounding. The shock of a fast-moving remnant of the bridge generates volumetric oscillations of the bubble. The sound stops as soon as the bubble adopts a smooth elliptical or spherical shape. The formation of fine flow components is governed by the release of available potential energy in the process of the elimination of the free surface during the merging of liquids. Perturbations that arose are saved in a thin "double layer" around the former boundary surface inside fluid which is deformed and transported by the main flow.

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“…1) arises at the instant of time corresponding to the detachment of an asymmetrically shaped air cavity 2 (Fig. 2a) jet [12]. The fact, in itself, of the detachment of cavity 2 and its submersion indicates the existence of intense flows in the bulk of the liquid, although they do not manifest themselves in distortions of the free surface shape.…”

mentioning

confidence: 96%

“…A droplet was ejected from a calibrated nozzle (0.4 cm in diam eter) installed at height H. In each series of the exper iment, we performed calibration of the image scale at a given resolution. A more detailed description of the setup is presented in [12].…”

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confidence: 99%

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Dynamics of underwater sound emission for a droplet falling onto a liquid surface

Prokhorov

Chashechkin

2012

Dokl. Phys.

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The problem of sound emission by liquid and gas flows is urgent in modern physics and mathematics by virtue of the wide propagation and importance of this phenomenon for practice [1]. Jet engines, pumps, and fans are known as the most intense acoustic contami nators of the environment. An intense source of underwater acoustic noise is rain [2]. The connection of the emitted sound and bubble nucleation processes was also noted. The sound frequency is quite consis tent with calculations based on approximate formulas for a spherical cavity [3].In this case, the question on the energy balance in the emission process remains open [4]. Several mech anisms of sound generation have been considered, e.g., a sharp increase in internal pressure of the process of bubble compression by surface tension forces [5] and the interaction of bubble surface vibration modes [6]. The effect of a cumulative jet arising as a result of breaking off the connecting neck between a bubble and the liquid surface was also analyzed in [7,8]. This effect is accompanied by a rapid compression drop in the surrounding liquid [9]. At the same time, as esti mates have shown, the combined action of surface tension forces and hydrostatic pressure provides not more than 10% of the energy of the registered acoustic emission [5].In experiments with gases injected into liquids through profiled nozzles, the sound emission was related to bubble volume reduction as a result of breaking off the connecting neck [10]. At this instant of time, the onset for the sequence of sonic packets initiated by the droplet fall onto the water surface was registered [11]. It was noted in experiments with fall ing droplets that the parameters of sonic packets (their duration, amplitude, and frequency) varied noticeably even under the same external conditions. Thus, the onset of sound generation by detached gas bubbles at the instant of breaking off from the con necting neck is confirmed in a number of independent experiments and may be considered to be true. How ever, the mechanisms of the excitation and mainte nance of the emission and the transformation of the mechanical motion energy to acoustic energy remain unknown. In the present paper, we study the connec tion between the processes of sound emission and shape variation for an emitting gas cavity.The experiments were conducted in a hydrooptic basin 145 × 50 × 60 cm 3 in volume. The basin, supplied with windows made of optic glass, was filled with degasified tap water to a depth of 40 cm, which consid erably exceeded the size of the droplets, of the cavern, and of the arising gas bubbles. Acoustic pressure vari ations were registered by a GI51B measuring hydro phone (transmission band of 2 Hz to 120 kHz, sensi tivity of 30 mV Pa -1 , irregularity of the amplitude fre quency characteristic better than 3 dB). The flow pattern was recorded by an Optronis CR3000 × 2 high speed video camera (recording rate up to 200 000 frames per second). The camera's optic axis was aligned hor izontally at the level of the free water surface....

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Sound generation as a drop falls on a water surface

Cited by 19 publications

References 14 publications

Differential Fluid Mechanics—Harmonization of Analytical, Numerical and Laboratory Models of Flows

Differential Fluid Mechanics—Harmonization of Analytical, Numerical and Laboratory Models of Flows

Hydrodynamics, Energetics and Acoustics of Free Falling Drop Impact at a Motionless Fluid

Dynamics of underwater sound emission for a droplet falling onto a liquid surface

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