scholarly journals Singular jets during the collapse of drop-impact craters

2018 ◽  
Vol 848 ◽  
Author(s):  
S. T. Thoroddsen ◽  
K. Takehara ◽  
H. D. Nguyen ◽  
T. G. Etoh
Keyword(s):  
High Speed ◽  
Power Laws ◽  
Dimple Size ◽  
Inertial Focusing ◽  
Surface Level ◽  
Video Cameras ◽  
High Speed Video ◽  
Extensional Stress ◽  
Volume Oscillation ◽  
Drop Impacts

When a drop impacts on a deep pool at moderate velocity it forms a hemispheric crater which subsequently rebounds to the original free-surface level, often forming Worthington jets, which rise vertically out of the crater centre. Under certain impact conditions the crater collapse forms a dimple at its bottom, which pinches off a bubble and is also known to be associated with the formation of a very fast thin jet. Herein we use two ultra-high-speed video cameras to observe simultaneously the dimple collapse and the speed of the resulting jet. The fastest fine jets are observed at speeds of approximately $50~\text{m}~\text{s}^{-1}$ and emerge when the dimple forms a cylinder which retracts without pinching off a bubble. We also identify what appears to be micro-bubbles at the bottom of this cylinder, which we propose are caused by local cavitation from extensional stress in the flow entering the jet. The radial collapse of the dimple does not follow capillary-inertial power laws nor is its bottom driven by a curvature singularity, as has been proposed in some earlier studies. The fastest jets are produced by pure inertial focusing and emerge at finite dimple size, bypassing the pinch-off singularity. These jets emerge from the liquid contained originally in the drop. Finally, we measure directly the compression of the central bubble following the pinch-off and the subsequent large volume oscillation, which occurs at frequencies slightly above the audible range at approximately 23 kHz.

scholarly journals Standard of the Initial Ball Velocity for a Fly Ball in Baseball Hitting

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 137
Author(s):  
Hirotaka Nakashima ◽  
Gen Horiuchi ◽  
Shinji Sakurai
Keyword(s):  
Initial Velocity ◽  
High Speed ◽  
Baseball Players ◽  
Ball Impact ◽  
Video Cameras ◽  
High Speed Video ◽  
Before And After ◽  
Ball Velocity ◽  
Opposite Field ◽  
Measuring Tape

This study aimed to determine the minimum required initial velocity to hit a fly ball toward the same field (left-field for right-handed batters), center field, and opposite field (right field for right-handed batters). Six baseball players hit fastballs launched by a pitching machine. The movements of the balls before and after bat-to-ball impact were recorded using two high-speed video cameras. The flight distance was determined using a measuring tape. Seventy-nine trials were analyzed, and the minimum required initial velocities of batted balls were quantified to hit balls 60, 70, 80, 90, 100, 110, and 120 m in each direction through regression analysis. As a result, to hit a ball 120 m, initial velocities of 43.0, 43.9, and 46.0 m/s were required for the same field, center field, and opposite field, respectively. The result provides a useful index for batters to hit a fly ball in each of the directions.

Micro-splashing by drop impacts

2012 ◽  
Vol 706 ◽  
pp. 560-570 ◽  
Author(s):  
S. T. Thoroddsen ◽  
K. Takehara ◽  
T. G. Etoh
Keyword(s):  
Free Surface ◽  
Size Distribution ◽  
Solid Surface ◽  
High Speed ◽  
Solid Substrate ◽  
Liquid Sheet ◽  
Drop Surface ◽  
High Speed Video ◽  
Rain Drops ◽  
Drop Impacts

AbstractWe use ultra-high-speed video imaging to observe directly the earliest onset of prompt splashing when a drop impacts onto a smooth solid surface. We capture the start of the ejecta sheet travelling along the solid substrate and show how it breaks up immediately upon emergence from the underneath the drop. The resulting micro-droplets are much smaller and faster than previously reported and may have gone unobserved owing to their very small size and rapid ejection velocities, which approach 100 m s−1, for typical impact conditions of large rain drops. We propose a phenomenological mechanism which predicts the velocity and size distribution of the resulting microdroplets. We also observe azimuthal undulations which may help promote the earliest breakup of the ejecta. This instability occurs in the cusp in the free surface where the drop surface meets the radially ejected liquid sheet.

scholarly journals Experimental analysis of high velocity impacts of composite fragments on aluminium plates

2021 ◽  
Vol 250 ◽  
pp. 01011
Author(s):  
Jorge López-Puente ◽  
Jesús Pernas-Sánchez ◽  
José Alfonso Artero-Guerrero ◽  
David Varas ◽  
Joseba Múgica ◽  
...  
Keyword(s):  
High Velocity ◽  
High Speed ◽  
Woven Composites ◽  
Residual Velocity ◽  
Video Cameras ◽  
High Speed Video ◽  
High Velocity Impacts ◽  
Deformable Structure ◽  
The Impact ◽  
Composite Blades

The improvement of engines is one of the ways to diminish the fuel consumption in civil aircrafts, and Open Rotors engines are one of the best promises in order to achieve a sensible efficiency increment. These engines have large composite blades that could, in the event of failure, impact against the fuselage, totally or partially. In this case, composite fragments could behave as impactors. In order to design fuselages for this event and adopt these new engines in the future, it is necessary to understand the impact behaviour of a composite fragment against a deformable structure. To this end, unidirectional and woven composites fragments were impacted at high velocity (up to 150 m/s) against aluminium panels at different impact velocities. The composite fragments were made using AS4/8552 (UD) and AGP-193PW (woven) prepregs manufactured by Hexcel Composites, both using AS4 fibres and 8552 epoxy matrix. High speed video cameras were used to record the impact process and to measure both the impact and the residual velocity and hence the energy absorbed.

Vibration analysis of acoustic guitar string employing high-speed video cameras

2016 ◽  
Vol 139 (4) ◽  
pp. 2204-2204 ◽  
Author(s):  
Bozena Kostek ◽  
Piotr Szczuko ◽  
Jozef Kotus ◽  
Maciej Szczodrak ◽  
Andrzej Czyzewski
Keyword(s):  
Vibration Analysis ◽  
High Speed ◽  
Video Cameras ◽  
High Speed Video ◽  
Acoustic Guitar

J027022 Kinematic analysis of dolphin jumping by using high-speed video cameras

2013 ◽  
Vol 2013 (0) ◽  
pp. _J027022-1-_J027022-5
Author(s):  
Yusuke UCHIDA ◽  
Gen LI ◽  
Masashi NAKAMURA ◽  
Hiroto TANAKA ◽  
Hao LIU
Keyword(s):  
Kinematic Analysis ◽  
High Speed ◽  
Video Cameras ◽  
High Speed Video

scholarly journals Design and Development of a Robotic Bee for the Analysis of Honeybee Dance Communication

2008 ◽  
Vol 5 (3) ◽  
pp. 157-164 ◽  
Author(s):  
T. Landgraf ◽  
H. Moballegh ◽  
R. Rojas
Keyword(s):  
Visual Feedback ◽  
High Speed ◽  
Tracking System ◽  
Feedback System ◽  
High Speed Camera ◽  
Video Cameras ◽  
High Speed Video ◽  
Successive Addition ◽  
Essential Properties ◽  
Dance Communication

We have designed a robotic honeybee to mimic the bee dance communication system. To achieve this goal, a tracking system has been developed to extract real bee dance trajectories recorded with high-speed video cameras. The results have been analysed to find the essential properties required for the prototype robot. Putative signals in the dance communication have been identified from the literature. Several prototypes were built with successive addition of more features or improvement of existing components. Prototypes were tested in a populated beehive results were documented using high-speed camera recordings. A substantial innovation is a visual feedback system that helps the robot to minimise collisions with other bees.

Development of high-speed video cameras for Dynamic PIV

2002 ◽  
Vol 5 (3) ◽  
pp. 213-224 ◽  
Author(s):  
G. T. Etoh ◽  
K. Takehara ◽  
Y. Takano
Keyword(s):  
High Speed ◽  
Video Cameras ◽  
High Speed Video ◽  
Dynamic Piv

Mechanics and aerodynamics of perching manoeuvres in a large bird of prey

2010 ◽  
Vol 114 (1161) ◽  
pp. 673-680 ◽  
Author(s):  
A. C. Carruthers ◽  
A. L. R. Thomas ◽  
S. M. Walker ◽  
G. K. Taylor
Keyword(s):  
High Speed ◽  
High Lift ◽  
Still Images ◽  
Video Cameras ◽  
Bird Of Prey ◽  
High Speed Video ◽  
Wing Profile ◽  
Large Bird ◽  
Flight Muscles

Abstract This paper reviews recent results on the mechanics and aerodynamics of perching in a large bird of prey, the Steppe Eagle Aquila nipalensis. Data collected using onboard and high-speed video cameras are used to examine gross morphing of the wing planform by the flight muscles, and smaller-scale morphing of the wing profile by aeroelastic deflection of the feathers, Carruthers et al. High-resolution still images are used to reconstruct the shape of the wing using multi-station photogrammetry, and the performance of the measured wing profile is analysed using a panel code, Carruthers et al. In bringing these lines of research together, we examine the role of aeroelastic feather deflection, and show that the key to perching in birds lies not in high-lift aerodynamics, but in the way in which the wings and tail morph to allow the bird to transition quickly from a steady glide into a deep stall.

Shuttlecock detection system for fully-autonomous badminton robot with two high-speed video cameras

2017 ◽  
Author(s):  
T. Masunari ◽  
K. Yamagami ◽  
M. Mizuno ◽  
S. Une ◽  
M. Uotani ◽  
...  
Keyword(s):  
High Speed ◽  
Detection System ◽  
Video Cameras ◽  
High Speed Video
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