scholarly journals On the Mechanism of Cavitation Damage by Nonhemispherical Cavities Collapsing in Contact With a Solid Boundary

1961 ◽  
Vol 83 (4) ◽  
pp. 648-656 ◽  
Author(s):  
Charl F. Naude´ ◽  
Albert T. Ellis
Keyword(s):  
High Speed ◽  
Cavity Wall ◽  
Solid Boundary ◽  
Cavity Volume ◽  
Axially Symmetric ◽  
Cavitation Damage ◽  
Fluid Theory ◽  
Symmetric Cavity ◽  
Theory And Experiment ◽  
Collapse Process

A perfect fluid theory, which neglects the effect of gravity, and which assumes that the pressure inside a cavitation bubble remains constant during the collapse process, is given for the case of a nonhemispherical, but axially symmetric cavity which collapses in contact with a solid boundary. The theory suggests the possibility that such a cavity may deform to the extent that its wall strikes the solid boundary before minimum cavity volume is reached. High-speed motion pictures of cavities generated by spark methods are used to test the theory experimentally. Agreement between theory and experiment is good for the range of experimental cavities considered, and the phenomenon of the cavity wall striking the solid boundary does indeed occur. Studies of damage by cavities of this type on soft aluminum samples reveals that pressures caused by the cavity wall striking the bounda y are higher than those resulting from a compression of gases inside the cavity, and are responsible for the damage.

scholarly journals Time series measurement of flow in an axially symmetric cavity by high-speed-video PIV

1999 ◽  
Vol 19 (Supplement2) ◽  
pp. 141-144
Author(s):  
Kenji Hosoi ◽  
Masaaki Kawahashi ◽  
Kouzyu Shiozaki ◽  
Hiroyuki Hirahara ◽  
Kennichirou Sato
Keyword(s):  
Time Series ◽  
High Speed ◽  
Axially Symmetric ◽  
High Speed Video ◽  
Symmetric Cavity ◽  
Series Measurement ◽  
Time Series Measurement

A study of the collapse of arrays of cavities

1988 ◽  
Vol 190 ◽  
pp. 409-425 ◽  
Author(s):  
J. P. Dear ◽  
J. E. Field
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
High Speed Photography ◽  
Cavitation Damage ◽  
Major Mechanism ◽  
Collapse Mechanisms ◽  
Multiple Jets ◽  
Circular Holes ◽  
Schlieren Photography ◽  
Thick Glass

This paper describes a method for examining the collapse of arrays of cavities using high-speed photography and the results show a variety of different collapse mechanisms. A two-dimensional impact geometry is used to enable processes occurring inside the cavities such as jet motion, as well as the movement of the liquid around the cavities, to be observed. The cavity arrangements are produced by first casting water/gelatine sheets and then forming circular holes, or other desired shapes, in the gelatine layer. The gelatine layer is placed between two thick glass blocks and the array of cavities is then collapsed by a shock wave, visualized using schlieren photography and produced from an impacting projectile. A major advantage of the technique is that cavity size, shape, spacing and number can be accurately controlled. Furthermore, the shape of the shock wave and also its orientation relative to the cavities can be varied. The results are compared with proposed interaction mechanisms for the collapse of pairs of cavities, rows of cavities and clusters of cavities. Shocks of kbar (0.1 GPa) strength produced jets of c. 400 m s−1 velocity in millimetre-sized cavities. In closely-spaced cavities multiple jets were observed. With cavity clusters, the collapse proceeded step by step with pressure waves from one collapsed row then collapsing the next row of cavities. With some geometries this leads to pressure amplification. Jet production by the shock collapse of cavities is suggested as a major mechanism for cavitation damage.

An experimental and simulation study of the flow pattern characteristics of water jet impingements in boreholes

2021 ◽  
pp. 014459872110520
Author(s):  
Yabin Gao ◽  
Xin Xiang ◽  
Ziwen Li ◽  
Xiaoya Guo ◽  
Peizhuang Han
Keyword(s):  
High Speed ◽  
Impact Force ◽  
Jet Impingement ◽  
Flow Patterns ◽  
Water Jet ◽  
Solid Boundary ◽  
Force Model ◽  
Water Jets ◽  
Contact Surfaces ◽  
The Impact

Hydraulic slotting has become one of the most common technologies adopted to increase permeability in low permeability in coal field seams. There are many factors affecting the rock breaking effects of water jets, among which the impact force cannot be ignored. To study the influencing effects of contact surface shapes on jet flow patterns and impact force, this study carried out experiments involving water jet impingement planes and boreholes under different pressure conditions. The investigations included numerical simulations under solid boundary based on gas–liquid coupling models and indoor experiments under high-speed camera observations. The results indicated that when the water jets impinged on different contact surfaces, obvious reflection flow occurred, and the axial velocity had changed through three stages during the development process. Moreover, the shapes of the contact surfaces, along with the outlet pressure, were found to have impacts on the angles and velocities of the reflected flow. The relevant empirical formulas were summarized according to this study's simulation results. In addition, the flow patterns and shapes of the contact surfaces were observed to have influencing effects on the impact force. An impact force model was established in this study based on the empirical formula, and the model was verified using both the simulation and experimental results. It was confirmed that the proposed model could provide important references for the optimization of the technical parameters water jet systems, which could provide theoretical support for the further intelligent and efficient transformation of coal mine drilling water jet technology.

Mitigation of Damage to Solid Surfaces From the Collapse of Cavitation Bubble Clouds

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Parag V. Chitnis ◽  
Nicholas J. Manzi ◽  
Robin O. Cleveland ◽  
Ronald A. Roy ◽  
R. Glynn Holt
Keyword(s):  
High Speed ◽  
Porous Ceramic ◽  
Bubble Surface ◽  
Back Pressure ◽  
Solid Surfaces ◽  
Surface Erosion ◽  
Cavitation Damage ◽  
Acoustic Transducer ◽  
Bubble Layer ◽  
Bubble Clouds

The collapse of transient bubble clouds near a solid surface was investigated to test a scheme for mitigation of cavitation-induced damage. The target was a porous ceramic disk through which air could be forced. Transient cavitation bubbles were created using a shock-wave lithotripter focused on the surface of the disk. The dynamics of bubble clouds near the ceramic disks were studied for two boundary conditions: no back pressure resulting in surface free of bubbles and 10 psi (0.7 atm) of back pressure, resulting in a surface with a sparse (30% of area) bubble layer. Images of the cavitation near the surface were obtained from a high-speed camera. Additionally, a passive cavitation detector (3.5 MHz focused acoustic transducer) was aligned with the surface. Both the images and the acoustic measurements indicated that bubble clouds near a ceramic face without a bubble layer collapsed onto the boundary, subsequently leading to surface erosion. When a sparse bubble layer was introduced, bubble clouds collapsed away from the surface, thus mitigating cavitation damage. The erosion damage to the ceramic disks after 300 shock waves was quantified using micro-CT imaging. Pitting up to 1 mm deep was measured for the bubble-free surface, and the damage to the bubble surface was too small to be detected.

Study on the Effect of Tool Rake Angle on Cutting Vibration in Precision Machining

2004 ◽  
Vol 471-472 ◽  
pp. 127-131
Author(s):  
Gui Cheng Wang ◽  
Li Jie Ma ◽  
Hong Jie Pei
Keyword(s):  
Theoretical Analysis ◽  
High Speed ◽  
Cutting Speed ◽  
Rake Angle ◽  
Precision Machining ◽  
Turning Operation ◽  
Cutting Vibration ◽  
Main Factors ◽  
Theory And Experiment

The cutting vibration is one of the main factors to affect precision machining. In this paper, the influence of tool rake angle on cutting vibration is studied at different cutting speed in turning operation, and corresponding theoretical analysis is made. The experiment results show that: the amplitude of machining vibration gradually decreases with tool rake angle increasing; while rake angle o g <0°, the biggest amplitude occurs at V=50~70m/min; While o g ≥0°, it is at V=160~180m/min. Moreover, theory and experiment foundation is presented on avoiding the biggest amplitude range so as to guarantee quality of precision machining at high speed.

Integral Axi-Symmetric Nozzle Design

1965 ◽  
Vol 69 (659) ◽  
pp. 795-798
Author(s):  
M. J. Cohen
Keyword(s):  
High Speed ◽  
Design Method ◽  
Space Technology ◽  
Axially Symmetric ◽  
Cross Sectional ◽  
Hypersonic Nozzle ◽  
Low Speed ◽  
Throat Region ◽  
High Enthalpy ◽  
Working Section

SummaryThis is an extension of the design method described in ref. 1 to the compressible flow in integral nozzles comprising both subsonic (contraction) and supersonic (effusor) parts. The nozzles are axially symmetric and will be considered as isentropic convertors of low speed high enthalpy inviscid gas to a high speed, relatively low enthalpy state, heat transfer effects being ignored. The key advantage of the method over existing hybrid design methods(2'3'4'5) is that no assumption is made as to conditions in the “sonic” throat region before expansion in the effusor, the design being integral from low speed inlet to high speed outlet. A slight disadvantage of the method is that of ref 1, namely that a nozzle of an ideally infinite extent has to be truncated both at inlet and outlet. However, for a given nozzle length this limitation can be biased towards the relatively insensitive low subsonic inlet to benefit correspondingly outlet conditions to the extent that it should be possible to make the maximum variation from the mean in the cross-sectional speed at outlet less than 0.01 per cent. The method is being applied to design integral hypersonic nozzle units for the projected small intermittent hypersonic facility in the Department of Aeronautics and Space Technology. This tunnel will have a nominal working-section diameter of 2 in and the flow will be accelerated from low speed (about 20 ft/sec) at inlet to Mach numbers of either 5, 6, or 7 at outlet to the working section using three alternative nozzles.

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.

Radial Flow Between Axisymmetric Nonparallel Plates of Small Slope

1988 ◽  
Vol 110 (2) ◽  
pp. 342-346
Author(s):  
R. F. Gans ◽  
A. G. Johnson ◽  
S. B. Malanoski
Keyword(s):  
Excellent Agreement ◽  
Mass Flux ◽  
Radial Flow ◽  
Central Pressure ◽  
Axially Symmetric ◽  
Air Mass ◽  
Bearing Load ◽  
Dramatic Difference ◽  
Theory And Experiment

We have measured the separation and central pressure of a slightly concave axially symmetric pressurized bearing as a function of lubricant (air) mass flux and bearing load. We find that a mean face slope of 1.6 × 10−3 makes a dramatic difference in the behavior of the bearing, reducing the central pressure by more than a factor of two and eliminating the need for overpressures to start the system. We have also explored the behavior of the system analytically and find excellent agreement between theory and experiment.

Measurements of Gas Bubble Size Distributions in Flowing Liquid Mercury

2012 ◽  
Author(s):  
Mark Wendel ◽  
Bernard Riemer ◽  
Ashraf Abdou
Keyword(s):  
Bubble Size ◽  
High Speed ◽  
National Laboratory ◽  
Size Distributions ◽  
Flow Loop ◽  
Proton Beam Irradiation ◽  
Flowing Liquid ◽  
Cavitation Damage ◽  
Oak Ridge ◽  
Liquid Mercury

Pressure waves created in liquid mercury pulsed spallation targets have been shown to induce cavitation damage on the target container. One way to mitigate such damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, measuring such a population in mercury is difficult since it is opaque and the mercury is involved in a turbulent flow. Ultrasonic measurements have been attempted on these types of flows, but the flow noise can interfere with the measurement, and the results are unverifiable and often unrealistic. Recently, a flow loop was built and operated at Oak Ridge National Labarotory to assess the capability of various bubbler designs to deliver an adequate population of bubbles to mitigate cavitation damage. The invented diagnostic technique involves flowing the mercury with entrained gas bubbles in a steady state through a horizontal piping section with a glass-window observation port located on the top. The mercury flow is then suddenly stopped and the bubbles are allowed to settle on the glass due to buoyancy. Using a bright-field illumination and a high-speed camera, the arriving bubbles are detected and counted, and then the images can be processed to determine the bubble populations. After using this technique to collect data on each bubbler, bubble size distributions were built for the purpose of quantifying bubbler performance, allowing the selection of the best bubbler options. This paper presents the novel procedure, photographic technique, sample visual results and some example bubble size distributions. The best bubbler options were subsequently used in proton beam irradiation tests performed at the Los Alamos National Laboratory. The cavitation damage results from the irradiated test plates in contact with the mercury are available for correlation with the bubble populations. The most effective mitigating population can now be designed into prototypical geometries for implementation into an actual SNS target.

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