scholarly journals Improved Instruments and Methods for the Photographic Study of Spark-Induced Cavitation Bubbles

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1683 ◽  
Author(s):  
Qi Zhang ◽  
Jing Luo ◽  
Yanwei Zhai ◽  
Yilan Li
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Time History ◽  
Flow Equation ◽  
Velocity Fields ◽  
Image Processing Algorithm ◽  
Working Process ◽  
Pressure Fields ◽  
Cavitation Bubbles ◽  
History Of

An underwater spark is able to induce a cavitation bubble, and this principle has been utilized to make cavitation bubble generators for several decades. In this paper, an improved instrument for generating spark-induced cavitation bubbles is described in detail. The voltage time history inside the instrument is measured to show the working process and principle. Cavitation bubbles are generated by the instrument and recorded by a high-speed camera. The radius time history of the bubble is obtained using an image processing algorithm. The ratio of its minimum radius to its maximum radius reaches ~0.2, which indicates that there is little undissolved gas in the bubble. With the radius time history, the velocity fields around the bubbles were calculated by the 1D continuity flow equation, and the pressure fields were calculated by the 1D Euler equation. One cavitation bubble is chosen and discussed in detail. The velocity and pressure on the bubble interface achieve their maximums (~25 m/s and ~1.2 MPa, respectively) at the same time, when the radius is at its minimum (~1 mm). Some statistical results are also presented to show the effect of the instrument.

scholarly journals A Photographic Study of Spark-Induced Cavitation Bubble Collapse

1972 ◽  
Vol 94 (4) ◽  
pp. 825-832 ◽  
Author(s):  
C. L. Kling ◽  
F. G. Hammitt
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Bubble Collapse ◽  
Solid Boundary ◽  
High Speed Photography ◽  
Minimum Volume ◽  
Cavitation Bubbles ◽  
Flowing System

The collapse of spark-induced cavitation bubbles in a flowing system was studied by means of high speed photography. The migration of cavitation bubbles toward a nearby solid boundary during collapse and rebound was observed. Near its minimum volume the bubble typically formed a high speed microjet, which struck the nearby surface causing individual damage craters on soft aluminum.

Analysis of Liquid Slug Motion in a Voided Line

1998 ◽  
Vol 120 (1) ◽  
pp. 74-80 ◽  
Author(s):  
J. Yang ◽  
D. C. Wiggert
Keyword(s):  
Momentum Transfer ◽  
High Speed ◽  
Time History ◽  
Air Entrainment ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Pressure Time ◽  
History Of ◽  
Good Agreement

A quasi-two-dimensional two-phase flow cylindrical model of slug motion in a voided line is developed that can reasonably predict the change of flow pattern of the slug, air entrainment, “holdup” and the distribution of axial velocity. However, when using the theory of incompressible momentum transfer to estimate the pressure-time history of slug at the elbow, the calculated results are not in good agreement with those of the experiments. Further analysis of the experimental results indicate that an acoustic, or waterhammerlike response may occur immediately upon impact of the high-speed slug with the elbow, and subsequently, the waveform exhibits momentum transfer due to the acceleration of the slug at the elbow.

On the mechanics of high speed liquid jets

1977 ◽  
Vol 357 (1689) ◽  
pp. 143-162 ◽  
Keyword(s):  
Sound Speed ◽  
High Speed ◽  
Supersonic Jet ◽  
Time History ◽  
Taylor Instability ◽  
Liquid Jets ◽  
Late Time ◽  
History Of ◽  
Theoretical Evidence

Both experimental and theoretical methods are used to investigate the mechanics of the emergence and flight of a liquid jet travelling at speeds supersonic relative to the sound speed of the liquid. The experimental work uses an Imacon image converter camera to follow the mechanical events at micro-second framing intervals. The theoretical investigation employs similarity arguments and the Tschaplygin transformation to investigate the role of liquid overcompression in the process of the jet emergence. In addition, simple theoretical arguments are used to examine the effects of Stokes drag on the small liquid particle shroud surrounding the jet and Taylor instability effects in the late time history of the jet’s flight. An evacuated chamber is used to verify the theoretical prediction that subsonic (relative to the liquid sound speed) jets will not undergo the violent decompression process predicted for supersonic jets. The experimental and theoretical evidence are synthesized into an overall picture of the jet’s history from initial decompression of an overdense supersonic jet to the breakup of the resulting liquid slugs by deceleration and Taylor instability.

Analysis of the dynamic response and fatigue reliability of a full-scale carbody of a high-speed train

2018 ◽  
Vol 232 (7) ◽  
pp. 2006-2023 ◽  
Author(s):  
Yaohui Lu ◽  
Linyuan Dang ◽  
Xing Zhang ◽  
Zhen Feng ◽  
Jing Zeng ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Probability Distribution ◽  
Failure Rate ◽  
Surrogate Model ◽  
High Speed ◽  
Time History ◽  
Strength Degradation ◽  
High Speed Train ◽  
Fatigue Reliability ◽  
History Of

For a vehicle operating under different line conditions, coupled with track irregularity and many other factors, the carbody is subjected to extremely complex random loads, and the load mainly exists in the form of an alternating load; therefore, the primary type of failure is fatigue failure. With the continuous improvement in train speed, lightweight designs of carbody structures and the application of high-strength aluminium alloy, the safety and reliability of a carbody require more attention. An investigation of the dynamic fatigue reliability of a full-scale carbody of a high-speed train under random load conditions is carried out. A dynamics model of the vehicle system has been established for acquiring the time history of forces acting on the carbody by each air spring (hereinafter referred to as ‘the load–time history’). A surrogate model (a simple model instead of a complex carbody model) of the carbody is established based on the Box–Behnken matrix design and the polynomial fitting method; then, the load–time history is transformed to the stress–time history of the points of concern, and the results are compared with the results of the transient analysis, which verify the accuracy and effectiveness of the surrogate model. Then, a stress block spectrum is obtained by rain flow counting, and the stress probability distribution is determined. Combined with the probability distribution of fatigue strength, a dynamic stress–strength interference model (the area of interference between strength and stress in the model changes over time) is established. The failure rate and dynamic reliability of the points of concern for two cases are analysed: without considering the strength degradation and considering the strength degradation. The results show that without considering the strength degradation during service, with increased service mileage, the fatigue strength reliability of the points of concern decreases continuously, and the corresponding failure rate of the points of concern decreases with time and reaches a steady value, which has the characteristics of the first two stages of the bathtub curve. By considering the strength degradation during service, the reliability of the points of concern decreases gradually, and the corresponding failure rate of the points of concern decreases and then increases, with all the features of the bathtub curve. In addition, compared with the base metal region, the fatigue resistance of the welded structure decreases due to welding. Under the same service conditions, the reliability of the welded region is relatively low, and fatigue failure is more likely to occur.

Analysis on Load Spectrum of Bogie Frame for High-Speed EMU

2014 ◽  
Vol 633-634 ◽  
pp. 1166-1173
Author(s):  
Yu Guang Wang ◽  
Da Fu Zhang
Keyword(s):  
Fatigue Life ◽  
Dynamic Model ◽  
High Speed ◽  
Estimation Method ◽  
Time History ◽  
Load Spectrum ◽  
Safe Operation ◽  
Bogie Frame ◽  
Key Factor ◽  
History Of

The load spectrum, on which there is not a thorough research, is the key factor of the safe operation of EMU. A dynamic model of some high-speed EMU is established and the load time history of main load on frame is obtained through simulation and analysis based on the Beijing-Tianjin route. The load spectrum for main load is calculated by rain-flow counting, the crossing contrast of load spectrum in basic and fault conditions is proceeded as well, the extent of impact of all kinds of fault conditions to bogie main load is analyzed and a brief introduction of estimation method of the frame fatigue life is put forward in this paper.

scholarly journals Comparison of cavitation bubbles evolution in viscous media

2018 ◽  
Vol 180 ◽  
pp. 02038 ◽  
Author(s):  
Darina Jasikova ◽  
Petr Schovanec ◽  
Michal Kotek ◽  
Vaclav Kopecky
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Silicone Oil ◽  
Time Development ◽  
High Speed Camera ◽  
Silicon Oil ◽  
Cavitation Bubbles ◽  
Laser Induced Breakdown ◽  
Viscous Media ◽  
Superheat Limit

There have been tried many types of liquids with different ranges of viscosity values that have been tested to form a single cavitation bubble. The purpose of these experiments was to observe the behaviour of cavitation bubbles in media with different ranges of absorbance. The most of the method was based on spark to induced superheat limit of liquid. Here we used arrangement of the laser-induced breakdown (LIB) method. There were described the set cavitation setting that affects the size bubble in media with different absorbance. We visualized the cavitation bubble with a 60 kHz high speed camera. We used here shadowgraphy setup for the bubble visualization. There were observed time development and bubble extinction in various media, where the size of the bubble in the silicone oil was extremely small, due to the absorbance size of silicon oil.

Analysis and Selection of Fluid-Film Bearings for Spool-Shaft Gas Turbines

1970 ◽  
Vol 92 (4) ◽  
pp. 597-606
Author(s):  
W. Shapiro ◽  
R. Colsher ◽  
O. Decker
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Ambient Pressure ◽  
Time History ◽  
Fluid Film ◽  
Fluid Film Bearings ◽  
High Speed Rotation ◽  
History Of ◽  
Speed Rotation

The mechanical simplicity and damping qualities of fluid-film bearings makes them attractive possibilities for spool-shaft bearings of gas turbines. The simultaneous high-speed rotation of journal and bearing, however, causes whirl stability to be a major problem. Computerized analysis was utilized to screen a spectrum of practical candidate configurations. Stability threshold plots were expeditiously generated using accurately determined cross-coupled spring and damping coefficients to represent the bearings. Performance of each bearing type was determined as a function of configuration, ambient pressure, and machined clearance. The selected three-lobe design was further tested with a “time-transient” analysis that accurately traced a complete time history of the motions of the system in its various degrees of freedom.

scholarly journals Sterilization of Biofilm in Foam Using a Single Cavitation Bubble

2020 ◽  
Vol 328 ◽  
pp. 05003
Author(s):  
Petr Schovanec ◽  
Darina Jasikova ◽  
Michal Kotek ◽  
Karel Havlicek ◽  
Magda Nechanicka ◽  
...  
Keyword(s):  
Laser Beam ◽  
Cavitation Bubble ◽  
High Speed ◽  
Bubble Collapse ◽  
Long Distance ◽  
Piv Method ◽  
Cavitation Bubbles ◽  
Image Velocimetry ◽  
Laser Induced Breakdown ◽  
Surrounding Liquid

This article presents the sterilization of bacteria using cavitation bubbles. Cavitation generated by ultrasound creates a cavitation cloud. Therefore is more advantageous to generate the cavitation bubbles by laser-induced breakdown, because it is possible to generate individual bubbles for the purpose of study single impact and physical mechanism of acting. The cavitation bubble is generated by a Nd: YAG 532nm laser beam, a short 10ns pulse. Here, we used optics to focus the laser beam and a high-speed camera to visualize characteristics the bubble. We used the method of long-distance microscopy and shadowgraph lightening for the visualization. We used the particle image velocimetry (PIV) method to determine the interaction of the bubble with the surrounding liquid and solid surface. The main goal of the research is to use cavitation to sterilize bacteria and biofilm in impact of single bubble collapse on living cells.

scholarly journals Features of the working process of high-speed diesel engines

2021 ◽  
Vol 264 ◽  
pp. 04021
Author(s):  
Sarvar Kadirov ◽  
Madamin Aripdjanov ◽  
Obidjon Ergashev ◽  
Ravshan Iskandarov
Keyword(s):  
Diesel Engine ◽  
Diesel Engines ◽  
High Speed ◽  
Engine Performance ◽  
Injection Pressure ◽  
Working Process ◽  
High Speed Diesel ◽  
Wide Range ◽  
History Of ◽  
Main Factors

This article discusses the main history of the creation of high-speed short-stroke diesel engines and an assessment of the main factors that most significantly affect the working process of a diesel engine. When developing a new design of a high-speed diesel engine, it is necessary to pay special attention to the following factors: the intensity of the air charge, injection pressure parameters, the shape of the combustion chamber and the choice of the best option. Research carried out with a 7 x 0.15 mm nozzle in a wide range of speed changes (n = 1000 + 2800 min-1) shows that it is possible to find a position of the widened valve at which optimal results are obtained at medium and high rotational speeds, and on small - engine performance will deteriorate slightly.

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