Air entrapment under an impacting drop

2003 ◽  
Vol 478 ◽  
pp. 125-134 ◽  
Author(s):  
S. T. THORODDSEN ◽  
T. G. ETOH ◽  
K. TAKEHARA
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Liquid Surface ◽  
Reynolds Numbers ◽  
Video Camera ◽  
Air Entrapment ◽  
Contraction Speed ◽  
High Speed Video Camera ◽  
Drop Impacts ◽  
Two Bubbles

When a drop impacts on a liquid surface it entraps a small amount of air under its centre as the two liquid surfaces meet. The contact occurs along a ring enclosing a thin disk of air. We use the next-generation ultra-high-speed video camera, capable of 1 million f.p.s. (Etoh et al. 2002), to study the dynamics of this air sheet as it contracts due to surface tension, to form a bubble or, more frequently, splits into two bubbles. During the contraction of the air disk an azimuthal undulation, resembling a pearl necklace, develops along its edge. The contraction speed of the sheet is accurately described by a balance between inertia and surface tension. The average initial thickness of the air sheet decreases with higher impact Reynolds numbers, becoming less than one micron. The total volume of air entrapped depends strongly on the bottom curvature of the drop at impact. A sheet of micro-bubbles is often observed along the original interface. Oguz–Prosperetti bubble rings are also observed. For low Weber numbers (We<20) a variety of other entrapment phenomena appear.

Motion of a Particle Floating on a Liquid Meniscus Surface

1992 ◽  
Vol 114 (3) ◽  
pp. 411-416 ◽  
Author(s):  
Kenji Katoh ◽  
Hideomi Fujita ◽  
Eiichiro Imazu
Keyword(s):  
High Speed ◽  
Liquid Surface ◽  
Vertical Direction ◽  
Video Camera ◽  
Tangential Direction ◽  
Tangential Component ◽  
Camera System ◽  
Buoyant Force ◽  
Liquid Meniscus ◽  
High Speed Video Camera

A small particle floating on a liquid meniscus surface near a vessel wall tends to approach the wall spontaneously. This particle behavior was theoretically investigated. Because of the solid-liquid wettability, an unbalanced force is caused in the tangential direction to the liquid surface and the particle moves toward the wall. Since the particle is excessively drawn into the liquid due to the wettability, an excessive buoyant force acts on the particle in the vertical direction. The force caused by the wettability points in the normal downward direction to the liquid surface and is balanced with that component of the buoyant force. Then the tangential component of the buoyant force is not balanced and the particle moves upward along the meniscus surface. The particle trajectory calculation based on the above theoretical consideration agrees with the experimental one observed by a high-speed video camera system.

Experiments on Drop Impact and Coalescence at a Liquid/Liquid Interface

2003 ◽  
Author(s):  
Zulfaa Mohamed-Kassim ◽  
Ellen K. Longmire
Keyword(s):  
High Speed ◽  
Vortex Pair ◽  
Reynolds Numbers ◽  
Video Camera ◽  
Liquid Interface ◽  
Bulk Liquid ◽  
Index Matching ◽  
High Speed Video Camera ◽  
Gravity Driven ◽  
Counter Rotating Vortex Pair

The gravity-driven impact and coalescence of a single drop through a liquid/liquid interface have been investigated experimentally. PIV images were obtained with a high frequency pulsed-laser and a high-speed video camera. Index-matching and a slight camera inclination were employed to eliminate optical distortion. The drop Reynolds numbers based on impact velocity and ambient viscosity were 20 and 68. During the approach towards the interface, viscous stresses generated a vortex ring inside each drop and a wake behind it. The subsequent deformation of the drop and the interface due to impact were observed to be more radical in the higher Re case. Both the wake shearing on the upper drop surface and interfacial deformation were significant in dissipating the vorticity inside the drops. After the vorticity dissipated, an outward flow developed along one radian between the ‘resting’ drop and the interface below generating a counter-rotating vortex pair. The eventual coalescence was typically off axis. During coalescence, a capillary ring wave propagated radially inward enhancing the collapse of the drop fluid into the bulk liquid below.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

In Situ Observation Method for Quantitative Evaluation of Solidification Phenomena and Solidification Cracks during Welding

2014 ◽  
Vol 782 ◽  
pp. 3-7
Author(s):  
Kenji Shinozaki ◽  
Motomichi Yamamoto ◽  
Kohta Kadoi ◽  
Peng Wen
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Solidification Cracking ◽  
In Situ Observation ◽  
High Speed Video Camera ◽  
Varestraint Test ◽  
Solidification Cracks ◽  
Observation Method ◽  
Solidification Crack

Solidification cracking during welding is very serious problem for practical use. Therefore, there are so many reports concerning solidification cracking. Normally, solidification cracking susceptibility of material is quantitatively evaluated using Trans-Varestraint test. On the other hand, local solidification cracking strain was tried to measure precisely using in-situ observation method, called MISO method about 30 years ago. Recently, digital high-speed video camera develops very fast and its image quality is very high. Therefore, we have started to observe solidification crack using in site observation method. In this paper, the local critical strain of a solidification crack was measured and the high temperature ductility curves of weld metals having different dilution ratios and different grain sizes to evaluate quantitatively the effects of dilution ratio and grain size on solidification cracking susceptibility by using an improved in situ observation method.

Study on Magnetic Barrel Machine Equipped with Three-Dimensional Arrangement of Magnets

2007 ◽  
Vol 329 ◽  
pp. 761-766 ◽  
Author(s):  
Y. Zhang ◽  
Masato Yoshioka ◽  
Shin-Ichiro Hira
Keyword(s):  
High Speed ◽  
Permanent Magnets ◽  
Three Dimensional ◽  
Video Camera ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
The Media ◽  
Set Up

At present, a commercially available magnetic barrel machine equipped with permanent magnets has some faults arising from constructional reason. That is, grinding or finishing ability is different from place to place in the machining region, resulting in the limitation on the region we can use in the container of workpieces. Therefore, in this research, authors made the new magnetic barrel machine equipped with three dimensional (3D) magnet arrangement to overcome these faults. The grinding ability of the new 3D magnetic barrel machine converted was experimentally examined, and compared with that of the traditional magnetic barrel machine. As a result, it was shown that we can use much broader region in the new 3D machine. It was also shown that the grinding ability became higher. The distribution of barrel media in action was recorded by means of a high speed video camera. It was clarified that the media rose up higher and were distributed more uniformly in the container by the effect of the magnet block newly set up. It was supposed that this must be the reason for the above-mentioned improvement of grinding ability.

Grease soap particles passing through an elastohydrodynamic contact under side slip conditions

2000 ◽  
Vol 214 (4) ◽  
pp. 317-325 ◽  
Author(s):  
P Eriksson ◽  
V Wikström ◽  
R Larsson
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Previous Investigation ◽  
Video Camera ◽  
Slip Conditions ◽  
High Speed Video ◽  
Elastohydrodynamic Contact ◽  
High Speed Video Camera ◽  
Pure Rolling ◽  
Minimum Film Thickness

In a previous investigation, grease thickener fibres were tracked as they passed through an elastohydrodynamic (EHD) contact in pure rolling using interferometry in a standard ball-and-disc apparatus. In order to capture single thickener fibres, a high-speed video camera was used. Here, the experiments have been repeated introducing different amounts of side slip for different rolling speeds and a faster video camera capable of capturing 4500 frames/s. The contact was lubricated with a continuous supply of grease. Two greases, based on the same synthetic poly(α-olefin) but thickened with Li-12-OH and lithium complex soap respectively, were studied. It was observed that the thickener fibres were stretched both before entering the contact and as they passed through it. Fibres seem to avoid the minimum film thickness regions and, if they enter, the film is restored immediately after passage.

Biomechanical Analysis of a World Record Javelin Throw: A Case Study

1985 ◽  
Vol 1 (1) ◽  
pp. 73-77 ◽  
Author(s):  
Robert J. Gregor ◽  
Marilyn Pink
Keyword(s):  
High Speed ◽  
Video Camera ◽  
The United States ◽  
Track And Field ◽  
Biomechanical Analysis ◽  
World Record ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
Ongoing Project

As part of an ongoing project to evaluate elite track and field throwers in the United States, the javelin competition was filmed during the 1983 Pepsi Invitational Track Meet. A high-speed video camera (Spin Physics SP2000) was positioned orthogonal to the javelin runway to record the release of all throws. During this competition, Tom Petranoff’s world record (99.72 m) was filmed at 200 fields per second. Subsequent frame-by-frame digitization yielded results consistent with reports in the literature. Release velocity was 32.3 m/s and represents one of the highest values ever reported. Angle of release was .57r, javelin attitude at release was .64r» and angle of attack was .07r. While optimum values for these release parameters, in light of published results, remain open to discussion, the results presented here represent unique information on a world record performance and can serve as a basis of comparison for future performances.

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