Dynamic Behaviors of Re-Entrant Jet and Cavity Shedding During Transitional Cavity Oscillation on NACA0015 Hydrofoil

2018 ◽  
Vol 141 (6) ◽  
Author(s):  
Bangxiang Che ◽  
Linlin Cao ◽  
Ning Chu ◽  
Dmitriy Likhachev ◽  
Dazhuan Wu
Keyword(s):  
Pressure Measurement ◽  
High Speed ◽  
Large Scale ◽  
Dominant Role ◽  
Video Observation ◽  
Sheet Cavitation ◽  
High Speed Video ◽  
Cavity Shedding ◽  
Cavity Closure ◽  
High Instability

Transitional cavity shedding is known as the stage of attached cavitation with high instability and distinct periodicity. In this study, we experimentally investigated the dynamic characteristics of transitional cavity (0.8≤L/c<1) shedding on NACA0015 hydrofoil with high-speed video observation and synchronous pressure measurement. In the partial cavity (0.4<L/c<0.8) oscillation, the sheet cavitation grew along the chord with good spanwise uniformity, and the middle-entrant jet played a dominant role in cavity shedding. Meanwhile, in the transitional cavity oscillation, the previous shedding cavity exhibited a prohibitive effect on the growth of sheet cavitation on the hydrofoil, resulting in concave cavity closure line. Moreover, two symmetrical side-entrant jets originated at the near-wall ends and induced the two-stage shedding phenomenon. The aft and fore parts of the sheet cavitation shed separated as different forms and eventually merged into the large-scale cloud cavity.

Observation and Scaling of Tip Vortex Cavitation on Elliptical Hydrofoils

2011 ◽  
Author(s):  
Shigeki Nagaya ◽  
Risa Kimoto ◽  
Kenji Naganuma ◽  
Takayuki Mori
Keyword(s):  
Water Quality ◽  
Reynolds Number ◽  
High Speed ◽  
Tip Vortex ◽  
Video Observation ◽  
Tip Vortex Cavitation ◽  
Air Content ◽  
Sheet Cavitation ◽  
High Speed Video ◽  
Systems Research

Experimental study on tip vortex cavitation (TVC) was carried out for elliptical hydrofoils with various chord lengths. The purpose of the experiment was to clarify the influences of Reynolds number and water quality on tip vortex cavitation. Experiments were made in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense Japan. The elliptical hydrofoils tested were NACA 0012 cross section with chord lengths of 500mm, 250mm and 50mm. Reynolds number based on hydrofoil chord length was 2×105 < ReC < 7.4×106. Water quality of the tunnel was characterized by air content and nuclei distribution. Air content of the tunnel was varied between 30% and 80%. Nuclei distribution was measured by a cavitation susceptibility meter (CSM) with center-body venturi. Cavitation inception was determined from high speed video observation. A standard formula, (σL/σS) = (ReL/ReS)n, was applied for the scaling. In the present study, exponent of the scaling law n was found to be 0.2 < n < 0.4. High speed video observation showed that the process of the TVC inception strongly depends on water quality. In the experiments, unsteady behaviors of TVC were also investigated. Strong interactions between sheet cavitation and TVC were observed.

Reentrant Motion in Cloud Cavitation due to Cloud Collapse and Pressure Wave Propagation

2010 ◽  
Author(s):  
Keiichi Sato ◽  
Youhei Wada ◽  
Yoshitaka Noto ◽  
Yasuhiro Sugimoto
Keyword(s):  
Image Analysis ◽  
Wave Propagation ◽  
Difference Method ◽  
Pressure Wave ◽  
High Speed ◽  
Video Observation ◽  
Cloud Cavitation ◽  
High Speed Video ◽  
Frame Difference ◽  
Cavity Closure

It is well known that reentrant jet motion in periodic cloud cavitation means upward flow from the cavity closure area of cloud cavitation. However the mechanism of reentrant motion seems to remain unsolved clearly. In the present study some experiments were conducted about the mechanism of reentrant motion in a fixed type cavity for a convergent-divergent nozzle. High speed video observation and image analysis based on the frame difference method were made about unsteady cloud cavitation with a periodic structure of cavitation cloud shedding. As a result, the main points are experimentally found as follows; 1) a typical pattern of reentrant motions can be caused by the pressure wave propagation from the collapse of cavitation cloud shed downstream and 2) the frame difference method is very useful in an image analysis for high speed video observation of cavitating flow because the trajectory of pressure waves can be clearly visualized by the method.

1020 High-speed Video Observation of Wire EDM Performance

2008 ◽  
Vol 2008.46 (0) ◽  
pp. 403-404
Author(s):  
Keishi TANAKA ◽  
Masayuki HIGASHI ◽  
Akira OKADA ◽  
Yoshiyuki UNO ◽  
Toshiyuki YAMAUCHI
Keyword(s):  
High Speed ◽  
Video Observation ◽  
Wire Edm ◽  
High Speed Video

High-speed video observation of swimming behavior and flagellar motility ofProrocentrum minimum (Dinophyceae)

PROTOPLASMA ◽  
1998 ◽  
Vol 204 (1-2) ◽  
pp. 38-46 ◽  
Author(s):  
Iku Miyasaka ◽  
Kenji Nanba ◽  
Ken Furuya ◽  
Yoshihachiro Nimura
Keyword(s):  
High Speed ◽  
Swimming Behavior ◽  
Video Observation ◽  
Flagellar Motility ◽  
High Speed Video

High-speed Video Observation of Engine Oil Aeration

2004 ◽  
Author(s):  
D. L. Manz ◽  
J. S. Cowart ◽  
W. K. Cheng
Keyword(s):  
High Speed ◽  
Engine Oil ◽  
Video Observation ◽  
High Speed Video

Comparison between high‐speed video observation of sprites and broadband sferic measurements

2021 ◽  
Author(s):  
Huan Ren ◽  
Gaopeng Lu ◽  
Steven A. Cummer ◽  
Kang‐Ming Peng ◽  
Walter A. Lyons ◽  
...  
Keyword(s):  
High Speed ◽  
Video Observation ◽  
High Speed Video

The effect of shielding gas composition in CO2 laser—gas metal arc hybrid welding

2008 ◽  
Vol 222 (11) ◽  
pp. 1315-1324 ◽  
Author(s):  
H-B Chae ◽  
C-H Kim ◽  
J-H Kim ◽  
S Rhee
Keyword(s):  
Molten Metal ◽  
High Speed ◽  
Dominant Role ◽  
Ambient Air ◽  
Metal Transfer ◽  
Video Observation ◽  
Hybrid Welding ◽  
Shielding Gas ◽  
Droplet Transfer ◽  
Laser Induced Plasma

In carbon dioxide (CO2) laser—gas metal arc hybrid welding, a shielding gas is supplied to isolate the molten metal from the ambient air, suppress the laser-induced plasma, remove the plume out of the keyhole, and stabilize the metal transfer. In this study, a shielding gas consisting of helium, argon, and CO2 was used, and its effects on the composition of the welding phenomena, such as behaviours of laser-induced plasma generation, molten pool flow, and droplet transfer in gas metal arc welding, were investigated. High-speed video observation was used to investigate the welding phenomena inside the arc regime. Consequently, helium was found to have a dominant role in suppressing laser-induced plasma; minimum helium content at a laser power of 8 kW was suggested for laser autogenous and hybrid welding. Argon and CO2 govern the droplet transfer and arc stability. A 12 per cent addition of CO2 stabilizes the metal transfer and eliminates undercut caused by insufficient wetting of molten metal.

scholarly journals Rockburst simulation using dynamic tests on the support system

2021 ◽  
Vol 2 (1) ◽  
pp. 1-6
Author(s):  
R. Brändle ◽  
R. Luis Fonseca ◽  
G. Fisher
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Support Systems ◽  
Test Site ◽  
Ground Support ◽  
High Speed Video ◽  
Load Cells ◽  
Support Area ◽  
Scale Test ◽  
Bearing Behavior

Ground support for dynamic conditions must be able to withstand the associated loads and deformations and the support scheme must work as a system. In order to prove the suitability of such support systems with high-tensile steel mesh and bolts and to analyze the bearing behavior of them, a large-scale test setup was commissioned in Walenstadt, Switzerland. On this test rig it is possible to apply large energies on variable ground support systems with variable bolt patterns and meshes with a total support area of 3.6 × 3.6m in a full-scale way. The test site is instrumented by load cells, high-speed video analysis and accelerometers. In this paper the analysis of the load cells, the accelerometers and the high-speed video cameras is given, and results of system tests are discussed.

scholarly journals High-Speed Video Observation of Tympanic Membrane Rupture in Guinea Pigs

2003 ◽  
Vol 46 (4) ◽  
pp. 1434-1440 ◽  
Author(s):  
Takuji KOIKE ◽  
Hiroshi WADA ◽  
Fumiaki ITO ◽  
Kazuyoshi TAKAYAMA ◽  
Toshimitsu KOBAYASHI
Keyword(s):  
Tympanic Membrane ◽  
Guinea Pigs ◽  
High Speed ◽  
Video Observation ◽  
Membrane Rupture ◽  
High Speed Video
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