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.

Shock Waves as dominant Mechanism for Cavitation damage

2021 ◽  
pp. 1-12
Author(s):  
Osman Omar Osman ◽  
Ahmed Abouel Kasem Ahmed ◽  
Shemy Mohamed Ahmed
Keyword(s):  
Shock Waves ◽  
Cavitation Bubble ◽  
High Speed ◽  
Pure Aluminum ◽  
Shock Pressure ◽  
Surface Erosion ◽  
Pressure Waves ◽  
Wear Particles ◽  
Cavitation Damage ◽  
Cavitation Wear

Abstract In this paper, the mechanism of energy transfer from cavitation bubbles to solids is demonstrated as shock waves. To identify this mechanism, cavitation bubble structures, the corresponding damaged surface, and the wear particles in vibratory erosion tests on pure aluminum Al-99.999 using high-speed and SEM photography were observed. The eroded surface morphology was in the form of large swellings (hundreds of micrometers), which embodies the plastic flow. Results indicate that large swelling regions formed in a few seconds are caused by shock pressure waves and not by a microjet only several micrometers in size. The observed surface erosion and falling particles make it clear that the mechanism of cavitation wear is fatigue failure.

scholarly journals Production of Porous Ceramic Materials from Spent Fluorescent Lamps

2021 ◽  
Vol 11 (13) ◽  
pp. 6056
Author(s):  
Egle Rosson ◽  
Acacio Rincón Rincón Romero ◽  
Denis Badocco ◽  
Federico Zorzi ◽  
Paolo Sgarbossa ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
High Speed ◽  
Porous Ceramic ◽  
Ceramic Materials ◽  
Porous Ceramics ◽  
Fluorescent Lamps ◽  
Naoh Solution ◽  
Commercial Glass ◽  
Triton X

Spent fluorescent lamps (SFL) are classified as hazardous materials in the European Waste Catalogue, which includes residues from various hi-tech devices. The most common end-of-life treatment of SFL consists in the recovery of rare earth elements from the phosphor powders, with associated problems in the management of the glass residues, which are usually landfilled. This study involves the manufacturing of porous ceramics from both the coarse glass-rich fraction and the phosphor-enriched fraction of spent fluorescent lamps. These porous materials, realizing the immobilization of Rare Earth Elements (REEs) within a glass matrix, are suggested for application in buildings as thermal and acoustic insulators. The proposed process is characterized by: (i) alkaline activation (2.5 M or 1 M NaOH aqueous solution); (ii) pre-curing at 75 °C; (iii) the addition of a surfactant (Triton X-100) for foaming at high-speed stirring; (iv) curing at 45 °C; (v) viscous flow sintering at 700 °C. All the final porous ceramics present a limited metal leaching and, in particular, the coarse glass fraction activated with 2.5 M NaOH solution leads to materials comparable to commercial glass foams in terms of mechanical properties.

scholarly journals Cavitation patterns in high-pressure homogenization nozzles with cylindrical orifices: Influence of mixing stream in Simultaneous Homogenization and Mixing

2021 ◽  
Author(s):  
V. Gall ◽  
E. Rütten ◽  
H. P. Karbstein
Keyword(s):  
High Pressure ◽  
Process Design ◽  
High Speed ◽  
State Of The Art ◽  
Back Pressure ◽  
High Pressure Homogenization ◽  
Unit Operation ◽  
Mixing Chamber ◽  
Cavitation Intensity ◽  
Droplet Sizes

AbstractHigh-pressure homogenization is the state of the art to produce high-quality emulsions with droplet sizes in the submicron range. In simultaneous homogenization and mixing (SHM), an additional mixing stream is inserted into a modified homogenization nozzle in order to create synergies between the unit operation homogenization and mixing. In this work, the influence of the mixing stream on cavitation patterns after a cylindrical orifice is investigated. Shadow-graphic images of the cavitation patterns were taken using a high-speed camera and an optically accessible mixing chamber. Results show that adding the mixing stream can contribute to coalescence of cavitation bubbles. Choked cavitation was observed at higher cavitation numbers σ with increasing mixing stream. The influence of the mixing stream became more significant at a higher orifice to outlet ratio, where a hydraulic flip was also observed at higher σ. The decrease of cavitation intensity with increasing back-pressure was found to be identical with conventional high-pressure homogenization. In the future, the results can be taken into account in the SHM process design to improve the efficiency of droplet break-up by preventing cavitation or at least hydraulic flip.

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.

scholarly journals Movements of Mycoplasma mobile gliding machinery detected by high-speed atomic force microscopy

2021 ◽  
Author(s):  
Kohei Kobayashi ◽  
Noriyuki Kodera ◽  
Taishi Kasai ◽  
Yuhei O Tahara ◽  
Takuma Toyonaga ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Internal Structure ◽  
Sodium Azide ◽  
High Speed ◽  
Atp Hydrolysis ◽  
Solid Surfaces ◽  
Force Microscopy ◽  
Special Mechanism ◽  
Atomic Force ◽  
Internal Structures

ABSTRACTMycoplasma mobile, a parasitic bacterium, glides on solid surfaces, such as animal cells and glass by a special mechanism. This process is driven by the force generated through ATP hydrolysis on an internal structure. However, the spatial and temporal behaviors of the internal structures in living cells are unclear. In this study, we detected the movements of the internal structure by scanning cells immobilized on a glass substrate using high-speed atomic force microscopy (HS-AFM). By scanning the surface of a cell, we succeeded in visualizing particles, 2 nm in hight and aligned mostly along the cell axis with a pitch of 31.5 nm, consistent with previously reported features based on electron microscopy. Movements of individual particles were then analyzed by HS-AFM. In the presence of sodium azide, the average speed of particle movements was reduced, suggesting that movement is linked to ATP hydrolysis. Partial inhibition of the reaction by sodium azide enabled us to analyze particle behavior in detail, showing that the particles move 9 nm right, relative to the gliding direction, and 2 nm into the cell interior in 330 ms, then return to their original position, based on ATP hydrolysis.IMPORTANCEThe Mycoplasma genus contains bacteria generally parasitic to animals and plants. Some Mycoplasma species form a protrusion at a pole, bind to solid surfaces, and glide by a special mechanism linked to their infection and survival. The special machinery for gliding can be divided into surface and internal structures that have evolved from rotary motors represented by ATP synthases. This study succeeded in visualizing the real-time movements of the internal structure by scanning from the outside of the cell using an innovative high-speed atomic force microscope, and then analyzing their behaviors.

scholarly journals Characterization of Ultrasonic Bubble Clouds in A Liquid Metal by Synchrotron X-ray High Speed Imaging and Statistical Analysis

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 44 ◽  
Author(s):  
Chuangnan Wang ◽  
Thomas Connolley ◽  
Iakovos Tzanakis ◽  
Dmitry Eskin ◽  
Jiawei Mi
Keyword(s):  
High Speed ◽  
Liquid Metals ◽  
Quantitative Information ◽  
Ultrasonic Waves ◽  
High Speed Imaging ◽  
X Ray ◽  
Processing Strategies ◽  
Solidification Processes ◽  
Bubble Clouds ◽  
Temperature Liquid

Quantitative understanding of the interactions of ultrasonic waves with liquid and solidifying metals is essential for developing optimal processing strategies for ultrasound processing of metal alloys in the solidification processes. In this research, we used the synchrotron X-ray high-speed imaging facility at Beamline I12 of the Diamond Light Source, UK to study the dynamics of ultrasonic bubbles in a liquid Sn-30wt%Cu alloy. A new method based on the X-ray attenuation for a white X-ray beam was developed to extract quantitative information about the bubble clouds in the chaotic and quasi-static cavitation regions. Statistical analyses were made on the bubble size distribution, and velocity distribution. Such rich statistical data provide more quantitative information about the characteristics of ultrasonic bubble clouds and cavitation in opaque, high-temperature liquid metals.

Comparison in High-Speed Droplet Impact Between Single and Multiple Collisions Against a Wall Covered With a Liquid Film

2019 ◽  
Author(s):  
Yoichiro Fukuchi ◽  
Tomoki Kondo ◽  
Keita Ando
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
High Speed ◽  
Water Layer ◽  
Liquid Jet ◽  
Surface Erosion ◽  
Single Droplet ◽  
Cleaning Efficiency ◽  
Droplet Impingement ◽  
Wall Shear

Abstract In semiconductor industry, liquid jet cleaning plays an important role because of its high cleaning efficiency and low environmental load. However, its cleaning mechanism is not revealed in detail because the experimental observation of high-speed and sub-micron droplets is challenging. Furthermore, higher impact velocity may give rise to surface erosion due to water-hammer shock loading from the impingement. To study cleaning mechanisms and surface erosion, numerical simulation of droplet impingement accounting for both viscosity and compressibility is an effective approach. In the previous study, wall-shear-flow generation has evaluated from the simulation of high-speed single droplet impingement. To evaluate more practical model of jet cleaning application, simulation of two droplets simplifying mono-dispersed splay of droplet train is favorable. Here, we numerically simulated impingement of two droplets, which allows for evaluating water-hammer pressure and wall shear stress. We consider the case of two water droplets (200 μm in diameter) that collides continuously, at speed 50 m/s, at the inter-droplet distance from 250 to 400 μm, with a no-slip rigid wall covered with a water layer (100 μm in thickness). The simulation is based on compressible Navier-Stokes equations for axisymmetric flow and the mixture of two components appears in numerically diffusion interface expressed by the volume average and advection equation. The simulation is solved by finite-volume WENO scheme that can capture both shock waves and material interface. In our simulation, the impingement of second droplet impingement gain higher shear stress than the single droplet impingement. At the case that the inter-droplet distance is 300 μm, maximum shear stress is 30.22 kPa (at the second droplet impingement), which is much larger than at the first droplet impingement (8.42 kPa). This result indicates how the second droplet impingement make wall shear flow induced by first droplet impingement stronger. From the parameter study of the inter-droplet distance, we can say that wall shear stress gets stronger as water layer thickness decreases. Furthermore, the maximum wall pressure is 1.96 MPa at the second droplet impingement, which is larger than at the first droplet impingement (1.46 MPa). From this study, the evaluation of surface erosion caused by jet cleaning is expected. The simulation suggests that multiple droplets impingement continuously may gain higher cleaning efficiency, which will give us a fundamental insight into liquid jet cleaning technologies. For further study, simulation of water column impingement and comparing the result of impingement of two droplets are expected.

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.

A Technique for the Detection of Liquid Slip at a Load-Bearing, High Shear Contact

2005 ◽  
Author(s):  
J. H. Choo ◽  
H. A. Spikes ◽  
M. Ratoi ◽  
R. P. Glovnea ◽  
A. Forrest
Keyword(s):  
High Speed ◽  
Physical Phenomenon ◽  
Solid Surfaces ◽  
The Other ◽  
Plasma Cleaning ◽  
High Shear ◽  
Test Rig ◽  
Simple Liquids ◽  
New Type ◽  
O2 Plasma

This research aims to exploit the physical phenomenon of simple liquids slipping against very smooth solid surfaces, to create a new type of bearing where the lubricant slips against one surface but not the other. To demonstrate the feasibility of this idea, a special test rig capable of measuring milli-Newton forces has been employed to measure friction in high-speed, sliding contacts between a steel roller and sapphire window, lubricated by hexadecane. Sapphire was made either lyophobic by coating with a self-assembled silane monolayer, or lyophilic by O2-plasma cleaning. The roller was made lyophilic. A significant reduction in friction was achieved with lyophobic sapphire but not with lyophilic sapphire. This reduced friction is believed to result from lubricant slip against the lyophobic surface. One possible application of such a bearing will be in microsystems and devices.

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