Irregular Bubble Entrainment Following Drop Impact on a Free Surface

2003 ◽  
Author(s):  
Yukio Tomita ◽  
Toshiyasu Kasai ◽  
Shinya Miura
Keyword(s):  
Free Surface ◽  
Impact Velocity ◽  
Water Surface ◽  
Drop Impact ◽  
Drop Diameter ◽  
Air Bubbles ◽  
Air Bubble ◽  
Bubble Entrainment ◽  
Irregular Case ◽  
The Impact

An air bubble is entrained by the impact of a drop on a water surface. Consequently sound is emitted. There are two categories of the bubble entrainment depending on the drop diameter dD and impact velocity Vimp. One is the regular entrainment where air bubbles are always pinched off, another is the irregular case where bubbles are trapped irregularly. In this paper we explore the mechanism of the irregular bubble entrainment and induced bubble sound.

Surface breakup and air bubble formation by drop impact in the irregular entrainment region

2007 ◽  
Vol 588 ◽  
pp. 131-152 ◽  
Author(s):  
Y. TOMITA ◽  
T. SAITO ◽  
S. GANBARA
Keyword(s):  
Froude Number ◽  
Water Column ◽  
Water Surface ◽  
Bubble Formation ◽  
Drop Impact ◽  
Air Bubbles ◽  
Bubble Generation ◽  
Air Bubble ◽  
Bubble Entrainment ◽  
The Impact

Drop impact on a water surface can be followed by underwater sounds originating not at the drop impact but when the entrained bubbles oscillate. Although the sound mechanism in the regular bubble entrainment region is well-known, there is less knowledge on the impact phenomena in the irregular bubble entrainment region where various situations can exist, such as many types of bubble formation or even no bubble generation under some conditions. In the present study, the aim is to clarify the dynamics of the water surface after the impact of a primary drop, mainly with diameter 5.2, 5.7 and 6.2mm, each of which is accompanied by a single satellite drop. Special attention was paid to the breakup behaviour of the water surface for Froude number Fr < 300. It was found that three underwater sounds were generated for a single drop impact, besides the sound due to impact itself. The first two were audible to the human ear, but the third one was almost inaudible. The first underwater sound resulted from the oscillation of a single air bubble formed as a result of the satellite drop impact on the bottom of the contracting cavity, and the second sound was due to the oscillation of air bubbles generated during the collapse of the water column. The formation of these air bubbles strongly depends on the Froude number, Weber number (or Bond number) and the aspect ratio of the drop at impact, although involving probability characteristics. Furthermore it is suggested that an air bubble entrapped in a water column plays an important role in increasing the probability of contact between the column surface and the curved free surface. A Japanese Suikinkutsu was introduced as an application of drop-impact-induced sounds. Using an open-type Suikinkutsu an additional experiment was carried out with larger drops with average diameters of 6.2, 7.2 and 7.8, mm.

scholarly journals Exploring droplet impact near a millimetre-sized hole: comparing a closed pit with an open-ended pore

2015 ◽  
Vol 772 ◽  
pp. 427-444 ◽  
Author(s):  
Rianne de Jong ◽  
Oscar R. Enríquez ◽  
Devaraj van der Meer
Keyword(s):  
Impact Velocity ◽  
Crucial Role ◽  
Drop Impact ◽  
Impact Dynamics ◽  
Air Bubbles ◽  
Air Bubble ◽  
Impact Location ◽  
Impact Phenomena ◽  
The Impact

We investigate drop impact dynamics near closed pits and open-ended pores experimentally. The resulting impact phenomena differ greatly in each case. For a pit, we observe three distinct phenomena, which we denote as a splash, a jet and an air bubble, whose appearance depends on the distance between impact location and pit. Furthermore, we found that splash velocities can reach up to seven times the impact velocity. Drop impact near a pore, however, results solely in splashing. Interestingly, two distinct and disconnected splashing regimes occur, with a region of planar spreading in between. For pores, splashes are less pronounced than in the pit case. We state that, for the pit case, the presence of air inside it plays the crucial role of promoting splashing and allowing for air bubbles to appear.

scholarly journals Experimental Study of Drop Impact on Deep-Water Surface in the Presence of Wind

2018 ◽  
Vol 48 (2) ◽  
pp. 329-341 ◽  
Author(s):  
Xinan Liu
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Water Drop ◽  
Threshold Value ◽  
Impact Angle ◽  
Drop Impact ◽  
Wind Speeds ◽  
Secondary Droplets ◽  
Low Wind Speeds ◽  
The Impact

AbstractThe effects of wind on the impact of a single water drop on a deep-water surface are studied experimentally in a wind tunnel. Experiments are performed by varying impacting drop diameters, ranging from 2.5 to 4.1 mm and wind speeds up to 6.7 m s−1. The sequence of splashing events that occurred during drop impacts is recorded with a backlit, cinematic shadowgraph technique. The experimental results show that for low wind speeds, an asymmetrical crown forms on the leeward of the periphery of the colliding region after the drop hits the water surface, while a wave swell forms on the windward. Secondary droplets are generated from the crown rim. For high wind speeds with large drop diameters, ligaments are generated from the crown rim on the leeward of the drop impact site. The ligaments grow, coalesce, and fragment into secondary droplets. It is found that both the drag force and surface tension play important roles in the evolution process of the ligaments. The nondimensional K number (K = WeOh−0.4, where We is the Webber number and Oh is the Ohnesorge number) is used to describe the splashing-deposition limit of drop impact. The threshold value of this K number changes with the wind velocity and/or drop impact angle.

Numerical Simulation Study on the Wave Dissipating Performance of Air Bubbles Breakwater with Double Air Discharged Pipes

2014 ◽  
Vol 501-504 ◽  
pp. 2112-2115
Author(s):  
Cheng Xing Zhang
Keyword(s):  
Numerical Simulation ◽  
Simulation Study ◽  
Numerical Models ◽  
Variable Density ◽  
Air Bubbles ◽  
Two Phase ◽  
Air Bubble ◽  
The Impact ◽  
Phase Fluid

The numerical simulation of air bubbles breakwater was presented in this paper. The two-phase fluid of water and air was assumed as a variable density fluid. The numerical models were developed by FLUENT in order to explore the air amount scale in the system of air bubbles breakwater . The impact of double air discharged pipes on the wave dissipating performance of air bubble breakwater was obtained, which illuminated that under the condition of equal total air amount of Qp, the wave dissipating performance of air bubbles breakwater with double air discharged pipes breakwater may not be improved in comparison with the air bubbles breakwater with single air discharged pipe.

Numerical Simulation Study on the Submerged Pipe Depth of Air Bubbles Breakwater

2013 ◽  
Vol 353-356 ◽  
pp. 2732-2735
Author(s):  
Cheng Xing Zhang
Keyword(s):  
Numerical Simulation ◽  
Simulation Study ◽  
Incident Wave ◽  
Numerical Models ◽  
Variable Density ◽  
Air Bubbles ◽  
Two Phase ◽  
Air Bubble ◽  
The Impact ◽  
Phase Fluid

The numerical simulation of air bubbles breakwater was presented in this paper. The two-phase fluid of water and air was assumed as a variable density fluid. The numerical models were developed by FLUENT in order to explore the air amount scale in the system of air bubbles breakwater . The impact of submerged pipe depth on the wave dissipating performance of air bubble breakwater was obtained, which illuminated that The submerged pipe depth D is deeper, the wave dissipating performance of air bubbles breakwater is better. Furthermore, the effect of air amount and the incident wave periods on the performance of the air bubbles breakwater was analyzed.

Cavitation Testing of Propellers in a Free Surface Tunnel Utilizing Micro Air Bubble Control

1975 ◽  
Vol 97 (4) ◽  
pp. 523-531 ◽  
Author(s):  
K. Albrecht ◽  
O. Bjorheden
Keyword(s):  
Free Surface ◽  
Air Bubbles ◽  
Special Device ◽  
Test Results ◽  
Air Bubble ◽  
Bubble Cavitation ◽  
Marine Laboratory

Cavitation testing in a free surface tunnel presents specific problems in terms of low content of undissolved micro air bubbles in the water owing to the high de-aerating capacity of the tunnel. Such air nuclei are necessary to provide realistic conditions for the inception and extension of cavitation, in particular bubble cavitation at intermediate propeller loading. This paper gives a brief discussion of the problem in relation to some test results obtained in the new free surface tunnel at the KMW Marine Laboratory. A special device built into the tunnel circuit to produce the necessary amount of micro bubbles and its effect on cavitation and propeller forces is described.

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