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.

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.

Cavitation Phenomena in Thin Films of Newtonian, Non-Newtonian and Viscoelastic Fluids Due to Rapid Bubble Expansion Under Pulses of Negative Pressure

2003 ◽  
Author(s):  
P. Rhodri Williams ◽  
Rodhri L. Williams ◽  
A. Al-Hussany
Keyword(s):  
Thin Films ◽  
Synovial Fluid ◽  
Cavitation Bubble ◽  
Shear Thinning ◽  
Biological Tissues ◽  
Pressure Waves ◽  
Pulsed Ultrasound ◽  
Expansion Phase ◽  
Cavitation Damage ◽  
Shear Thinning Fluids

We report studies of the growth of a cavitation bubble in terms of the development of hydrodynamic pressures within the liquid close to the expanding bubble’s surface. The results of this study are discussed in terms of the possible consequences of cavitation bubble expansion in Newtonian and non-Newtonian, shear-thinning fluids (such as synovial fluid). Contrary to previous indications in the literature, non-Newtonian (specifically, shear-thinning) behaviour is found to be significant in this context, insofar as it may result in markedly enhanced tensions due to the pressure waves developed about a growing bubble during the latter stages of its expansion phase. The magnitude of the tensions so developed are compared with estimates of cavitation thresholds (Fc ) which are obtained from experiments involving the reflection of pulsed ultrasound at a flexible boundary. Under some circumstances the tensions developed about the growing cavity are shown to be commensurate with Fc. The possible consequences of these findings are discussed in terms of cavitation damage to blood vessels or other biological tissues.

Detonation Behaviors of Nitromethane with Various Initiating Shock Pressure

2007 ◽  
Vol 566 ◽  
pp. 41-46 ◽  
Author(s):  
Hideki Hamashima ◽  
Akinori Osada ◽  
Shigeru Itoh ◽  
Yukio Kato
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
Shock Pressure ◽  
High Speed Photography ◽  
Detailed Structure ◽  
Complicated Structure ◽  
Low Velocity ◽  
Cavitation Field ◽  
Liquid Explosives ◽  
Multiple Shock

Some liquid explosives have two different detonation behaviors: high velocity detonation (HVD) or low velocity detonation (LVD). The detonation behavior depends on the level of the initiating shock pressure. The detailed structure of LVD in liquid explosives has not yet been clarified. A physical model was proposed that LVD is not a self-reactive detonation, but rather a supported-reactive detonation from the cavitation field generated by precursor shock waves. In this study, high-speed photography was used to investigate the detonation behavior of nitromethane (NM) with the various initiating shock pressures. Stable LVD was not observed, only transient LVD was observed. A very complicated structure of LVD was observed: the interaction of multiple precursor shock waves, multiple oblique shock waves, and a cavitation field. Multiple shock waves propagating in non-detonating NM were observed for shock pressures below the range required for LVD, while above the LVD range HVD was observed.

Development of Water Treatment Systems Using Interaction of Pressure Waves, Cavitation Bubbles and Micro Bubbles

2014 ◽  
Author(s):  
Masaaki Tamagawa
Keyword(s):  
Water Treatment ◽  
Shock Waves ◽  
Cavitation Bubble ◽  
Treatment System ◽  
Bursting Pressure ◽  
Pressure Waves ◽  
Working Pressure ◽  
Water Treatment System ◽  
Cavitation Bubbles ◽  
Micro Bubble

This paper describes the fundamental investigations for developing new water treatment system using cavitation bubbles, micro bubbles and pressure waves (shock waves). To understand the fundamental phenomena of interaction of these factors, the pressure using cavitation bubbles and micro bubbles was measured, and the influence of micro bubble on the cavitation water treatment system was investigated. From these results, it was concluded that (1) there are two types of bursting pressure histories when pressure waves and cavitation bubble are working on micro-bubble, (2) frequency of bursting pressure from micro bubble and cavitation bubbles was increased by increasing working pressure, (3) the efficiency of water treatment was increased by increasing cavitation bubbles, (4) the improved water treatment system was proposed by changing the seeding position of the micro bubbles.

PIV Measurements of Cavitation Bubble Collapse Flow Induced by Pressure Wave

2010 ◽  
Author(s):  
Sheng-Hsueh Yang ◽  
Shenq-Yuh Jaw ◽  
Keh-Chia Yeh
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Bubble Radius ◽  
Ccd Camera ◽  
Bubble Surface ◽  
Bubble Collapse ◽  
Solid Boundary ◽  
Liquid Jet ◽  
Pressure Waves ◽  
Critical Position

In this study, a single cavitation bubble is generated by rotating a U-tube filled with water. A series of bubble collapse flows induced by pressure waves of different strengths are investigated by positioning the cavitation bubble at different stand-off distances to a solid boundary. Particle images of bubble collapse flow recorded by high speed CCD camera are analyzed by multi-grid, iterative particle image distortion method. Detail velocity variations of the transient bubble collapse flow are obtained. It is found that a Kelvin–Helmholtz vortex is formed when a liquid jet penetrates the bubble surface. If the bubble center to the solid boundary is within one to three times of the bubble radius, the liquid jet is able to impinge the solid boundary to form a stagnation ring. The fluid inside the stagnation ring will be squeezed toward the center of the ring to form a counter jet. At certain critical position, the bubble collapse flow will produce a Kelvin–Helmholtz vortex, the Richtmyer-Meshkov instability, or the generation of a counter jet flow, depending on the strengths of the pressure waves. If the bubble surface is in contact with the solid boundary, the liquid jet can only splash inside-out without producing the stagnation ring and the counter jet. The complex phenomenon of cavitation bubble collapse flows is clearly manifested in this study.

Three-Dimensional Imaging through Shock-Waves at Ultra-High Speed.

2018 ◽  
Author(s):  
Yi Chen Mazumdar ◽  
Michael E. Smyser ◽  
Jeffery Dean Heyborne ◽  
Daniel Robert Guildenbecher
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
Three Dimensional ◽  
Three Dimensional Imaging ◽  
Ultra High Speed

scholarly journals CFD Simulation of a Hyperloop Capsule Inside a Low-Pressure Environment Using an Aerodynamic Compressor as Propulsion and Drag Reduction Method

2021 ◽  
Vol 11 (9) ◽  
pp. 3934
Author(s):  
Federico Lluesma-Rodríguez ◽  
Temoatzin González ◽  
Sergio Hoyas
Keyword(s):  
Shock Waves ◽  
Power Consumption ◽  
High Speed ◽  
Cfd Simulation ◽  
Aerodynamic Drag ◽  
Flow Behavior ◽  
Critical Conditions ◽  
Vehicle Speed ◽  
Blockage Ratio ◽  
The Cost

One of the most restrictive conditions in ground transportation at high speeds is aerodynamic drag. This is even more problematic when running inside a tunnel, where compressible phenomena such as wave propagation, shock waves, or flow blocking can happen. Considering Evacuated-Tube Trains (ETTs) or hyperloops, these effects appear during the whole route, as they always operate in a closed environment. Then, one of the concerns is the size of the tunnel, as it directly affects the cost of the infrastructure. When the tube size decreases with a constant section of the vehicle, the power consumption increases exponentially, as the Kantrowitz limit is surpassed. This can be mitigated when adding a compressor to the vehicle as a means of propulsion. The turbomachinery increases the pressure of part of the air faced by the vehicle, thus delaying the critical conditions on surrounding flow. With tunnels using a blockage ratio of 0.5 or higher, the reported reduction in the power consumption is 70%. Additionally, the induced pressure in front of the capsule became a negligible effect. The analysis of the flow shows that the compressor can remove the shock waves downstream and thus allows operation above the Kantrowitz limit. Actually, for a vehicle speed of 700 km/h, the case without a compressor reaches critical conditions at a blockage ratio of 0.18, which is a tunnel even smaller than those used for High-Speed Rails (0.23). When aerodynamic propulsion is used, sonic Mach numbers are reached above a blockage ratio of 0.5. A direct effect is that cases with turbomachinery can operate in tunnels with blockage ratios even 2.8 times higher than the non-compressor cases, enabling a considerable reduction in the size of the tunnel without affecting the performance. This work, after conducting bibliographic research, presents the geometry, mesh, and setup. Later, results for the flow without compressor are shown. Finally, it is discussed how the addition of the compressor improves the flow behavior and power consumption of the case.

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.

Sign in / Sign up

Export Citation Format

Share Document