Journal articles on the topic 'Cavitation bubble dynamics'
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1
CHOI, JAEHYUG, and STEVEN L. CECCIO. "Dynamics and noise emission of vortex cavitation bubbles." Journal of Fluid Mechanics 575 (March 2007): 1–26. http://dx.doi.org/10.1017/s0022112006003776.
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The growth and collapse of a cavitation bubble forming within the core of a line vortex was examined experimentally to determine how the dynamics and noise emission of the elongated cavitation bubble is influenced by the underlying non-cavitating vortex properties. A steady line vortex was formed downstream of a hydrofoil mounted in the test section of a recirculating water channel. A focused pulse of laser light was used to initiate a nucleus in the core of a vortex, allowing for the detailed examination of the growth, splitting and collapse of individual cavitation bubbles as they experience a reduction and recovery of the local static pressure. Images of single-bubble dynamics were captured with two pulse-synchronized high-speed video cameras. The shape and dynamics of single vortex cavitation bubbles are compared to the original vortex properties and the local static pressure in the vortex core, and an analysis was performed to understand the relationship between the non-cavitating vortex properties and the diameter of the elongated cavitation bubble. Acoustic emissions from the bubbles were detected during growing, splitting and collapse, revealing that the acoustic impulse created during collapse was four orders of magnitude higher than the noise emission due to growth and splitting. The dynamics and noise generation of the elongated bubbles are compared to that of spherical cavitation bubbles in quiescent flow. These data indicate that the core size and circulation are insufficient to scale the developed vortex cavitation. The non-cavitating vortex circulation and core size are not sufficient to scale the bubble dynamics, even though the single-phase pressure field is uniquely scaled by these parameters. A simple analytical model of the equilibrium state of the elongated cavitation bubble suggests that there are multiple possible equilibrium values of the elongated bubble radius, each with varying tangential velocities at the bubble interface. Thus, the details of the bubble dynamics and bubble–flow interactions will set the final bubble dimensions.
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DELALE, C. F., G. H. SCHNERR, and J. SAUER. "Quasi-one-dimensional steady-state cavitating nozzle flows." Journal of Fluid Mechanics 427 (January 25, 2001): 167–204. http://dx.doi.org/10.1017/s0022112000002330.
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Quasi-one-dimensional cavitating nozzle flows are considered by employing a homogeneous bubbly liquid flow model. The nonlinear dynamics of cavitating bubbles is described by a modified Rayleigh–Plesset equation that takes into account bubble/bubble interactions by a local homogeneous mean-field theory and the various damping mechanisms by a damping coefficient, lumping them together in the form of viscous dissipation. The resulting system of quasi-one-dimensional cavitating nozzle flow equations is then uncoupled leading to a nonlinear third-order ordinary differential equation for the flow speed. This equation is then cast into a nonlinear dynamical system of scaled variables which describe deviations of the flow field from its corresponding incompressible single-phase value. The solution of the initial-value problem of this dynamical system can be carried out very accurately, leading to an exact description of the hydrodynamic field for the model considered.A bubbly liquid composed of water vapour–air bubbles in water at 20 °C for two different area variations is considered, and the initial cavitation number is chosen in such a way that cavitation can occur in the nozzle. Results obtained, when bubble/bubble interactions are neglected, show solutions with flow instabilities, similar to the flashing flow solutions found recently by Wang and Brennen. Stable steady-state cavitating nozzle flow solutions, either with continuous growth of bubbles or with growth followed by collapse of bubbles, were obtained when bubble/bubble interactions were considered together with various damping mechanisms.
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Wang, Yi-Chun. "Stability Analysis of One-Dimensional Steady Cavitating Nozzle Flows With Bubble Size Distribution." Journal of Fluids Engineering 122, no. 2 (December 20, 1999): 425–30. http://dx.doi.org/10.1115/1.483273.
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A continuum bubbly mixture model coupled to the Rayleigh-Plesset equation for the bubble dynamics is employed to study one-dimensional steady bubbly cavitating flows through a converging-diverging nozzle. A distribution of nuclei sizes is specified upstream of the nozzle, and the upstream cavitation number and nozzle contraction are chosen so that cavitation occurs in the flow. The computational results show very strong interactions between cavitating bubbles and the flow. The bubble size distribution may have significant effects on the flow; it is shown that it reduces the level of fluctuations and therefore reduces the “cavitation loss” compared to a monodisperse distribution. Another interesting interaction effect is that flashing instability occurs as the flow reaches a critical state downstream of the nozzle. A stability analysis is proposed to predict the critical flow variables. Excellent agreement is obtained between the analytical and numerical results for flows of both equal bubble size and multiple bubble sizes. [S0098-2202(00)00702-1]
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Zhu, Xi Jing, Ce Guo, Jian Qing Wang, and Guo Dong Liu. "Dynamics Modeling of Cavitation Bubble in the Grinding Area of Power Ultrasonic Honing." Advanced Materials Research 797 (September 2013): 108–11. http://dx.doi.org/10.4028/www.scientific.net/amr.797.108.
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t can particularly generate abundant cavitation bubbles in the processing of the power ultrasonic honing. The dynamics of cavitation bubbles in the grinding area are very vital to study the machining mechanism and the cutting chatter of power ultrasonic honing. Based on the Rayleigh-Plesset equation, a new dynamics model of cavitation bubble is established, considering the velocity of ultrasonic honing and honing pressure. With the superposition principle of velocity potential, the dynamics of double cavitation bubble is also established. Moreover, the dynamic characteristics of cavitation bubble also can be simulated numerically. The results show that cavitation bubble in the grinding zone begins to grow extensively and then undergoes collapse, and even subsequent rebound and then. The variation trend of radius change of double cavitation bubble in the grinding area is more than that of single cavitation bubble by an order of magnitude.
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Ban, Zhen Hong, Kok Keong Lau, and Mohd Sharif Azmi. "Bubble Nucleation and Growth of Dissolved Gas in Solution Flowing across a Cavitating Nozzle." Applied Mechanics and Materials 773-774 (July 2015): 304–8. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.304.
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Computational modelling of dissolved gas bubble formation and growth in supersaturated solution is essential for various engineering applications, including flash vaporisation of petroleum crude oil. The common mathematical modelling of bubbly flow only caters for single liquid and its vapour, which is known as cavitation. This work aims to simulate the bubble nucleation and growth of dissolved CO2 in water across a cavitating nozzle. The dynamics of bubble nucleation and growth phenomenon will be predicted based on the hydrodynamics in the computational domain. The complex interrelated bubble dynamics, mass transfer and hydrodynamics was coupled by using Computational Fluid Dynamics (CFD) and bubble nucleation and growth model. Generally, the bubbles nucleate at the throat of the nozzle and grow along with the flow. Therefore, only the region after the throat of the nozzle has bubbles. This approach is expected to be useful for various types of bubbly flow modelling in supersaturated condition.
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WILSON, MILES, JOHN R. BLAKE, and PETER M. HAESE. "CLOUD CAVITATION DYNAMICS." ANZIAM Journal 50, no. 2 (October 2008): 199–208. http://dx.doi.org/10.1017/s1446181109000133.
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AbstractAn analysis is developed for the behaviour of a cloud of cavitation bubbles during both the growth and collapse phases. The theory is based on a multipole method exploiting a modified variational principle developed by Miles [“Nonlinear surface waves in closed basins”, J. Fluid Mech.75 (1976) 418–448] for water waves. Calculations record that bubbles grow approximately spherically, but that a staggered collapse ensues, with the outermost bubbles in the cloud collapsing first of all, leading to a cascade of bubble collapses with very high pressures developed near the cloud centroid. A more complex phenomenon occurs for bubbles of variable radius with local zones of collapse, with a complex frequency spectrum associated with each individual bubble, leading to both local and global collective behaviour.
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d’Agostino, Luca, Fabrizio d’Auria, and Christopher E. Brennen. "A Three-Dimensional Analysis of Rotordynamic Forces on Whirling and Cavitating Helical Inducers." Journal of Fluids Engineering 120, no. 4 (December 1, 1998): 698–704. http://dx.doi.org/10.1115/1.2820726.
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This paper investigates the linearized dynamics of three-dimensional bubbly cavitating flows in helical inducers. The purpose is to understand the impact of the bubble response on the radial and tangential rotordynamic forces exerted by the fluid on the rotor and stator stages of whirling turbomachines under cavitating conditions. The flow in the inducer annulus is modeled as a homogeneous inviscid mixture, containing vapor bubbles with a small amount of noncondensable gas. The effects of several contributions to the damping of the bubble dynamics are included in the model. The governing equations of the inducer flow are written in “body-fitted” orthonormal helical Lagrangian coordinates, linearized for small-amplitude perturbations about the mean flow, and solved by modal decomposition. The whirl excitation generates finite-speed propagation and resonance phenomena in the two-phase flow within the inducer. These, in turn, lead to a complex dependence of the lateral rotordynamic fluid forces on the excitation frequency, the void fraction, the average size of the cavitation bubbles, and the turbopump operating conditions (including, rotational speed, geometry, flow coefficient and cavitation number). Under cavitating conditions the dynamic response of the bubbles induces major deviations from the noncavitating flow solutions, especially when the noncondensable gas content of the bubbles is small and thermal effects on the bubble dynamics are negligible. Then, the quadratic dependence of rotordynamic fluid forces on the whirl speed, typical of cavitation-free operation, is replaced by a more complex behavior characterized by the presence of different regimes where, depending on the whirl frequency, the fluid forces have either a stabilizing or a destabilizing effect on the inducer motion. Results are presented to illustrate the influence of the relevant flow parameters.
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Delale, Can F., Kohei Okita, and Yoichiro Matsumoto. "Steady-State Cavitating Nozzle Flows With Nucleation." Journal of Fluids Engineering 127, no. 4 (April 2, 2005): 770–77. http://dx.doi.org/10.1115/1.1949643.
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Quasi-one-dimensional steady-state cavitating nozzle flows with homogeneous bubble nucleation and nonlinear bubble dynamics are considered using a continuum bubbly liquid flow model. The onset of cavitation is modeled using an improved version of the classical theory of homogeneous nucleation, and the nonlinear dynamics of cavitating bubbles is described by the classical Rayleigh-Plesset equation. Using a polytropic law for the partial gas pressure within the bubble and accounting for the classical damping mechanisms, in a crude manner, by an effective viscosity, stable steady-state solutions with stationary shock waves as well as unstable flashing flow solutions were obtained, similar to the homogeneous bubbly flow solutions given by Wang and Brennen [J. Fluids Eng., 120, 166–170, 1998] and by Delale, Schnerr, and Sauer [J. Fluid Mech., 427, 167–204, 2001]. In particular, reductions in the maximum bubble radius and bubble collapse periods are observed for stable nucleating nozzle flows as compared to the nonnucleating stable solution of Wang and Brennen under similar conditions.
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Zubalic, Emil, Daniele Vella, Aleš Babnik, and Matija Jezeršek. "Interferometric Fiber Optic Probe for Measurements of Cavitation Bubble Expansion Velocity and Bubble Oscillation Time." Sensors 23, no. 2 (January 10, 2023): 771. http://dx.doi.org/10.3390/s23020771.
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Cavitation bubbles are used in medicine as a mechanism to generate shock waves. The study of cavitation bubble dynamics plays a crucial role in understanding and utilizing such phenomena for practical applications and purposes. Since the lifetime of cavitation bubbles is in the range of hundreds of microseconds and the radii are in the millimeter range, the observation of bubble dynamics requires complicated and expensive equipment. High-speed cameras or other optical techniques require transparent containers or at least a transparent optical window to access the region. Fiber optic probe tips are commonly used to monitor water pressure, density, and temperature, but no study has used a fiber tip sensor in an interferometric setup to measure cavitation bubble dynamics. We present how a fiber tip sensor system, originally intended as a hydrophone, can be used to track the expansion and contraction of cavitation bubbles. The measurement is based on interference between light reflected from the fiber tip surface and light reflected from the cavitation bubble itself. We used a continuous-wave laser to generate cavitation bubbles and a high-speed camera to validate our measurements. The shock wave resulting from the collapse of a bubble can also be measured with a delay in the order of 1 µs since the probe tip can be placed less than 1 mm away from the origin of the cavitation bubble. By combining the information on the bubble expansion velocity and the time of bubble collapse, the lifetime of a bubble can be estimated. The bubble expansion velocity is measured with a spatial resolution of 488 nm, half the wavelength of the measuring laser. Our results demonstrate an alternative method for monitoring bubble dynamics without the need for expensive equipment. The method is flexible and can be adapted to different environmental conditions, opening up new perspectives in many application areas.
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Wang, Yi-Chun, and C. E. Brennen. "One-Dimensional Bubbly Cavitating Flows Through a Converging-Diverging Nozzle." Journal of Fluids Engineering 120, no. 1 (March 1, 1998): 166–70. http://dx.doi.org/10.1115/1.2819642.
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A nonbarotropic continuum bubbly mixture model is used to study the one-dimensional cavitating flow through a converging-diverging nozzle. The nonlinear dynamics of the cavitation bubbles are modeled by the Rayleigh-Plesset equation. Analytical results show that the bubble/bubble interaction through the hydrodynamics of the surrounding liquid has important effects on this confined flow field. One clear interaction effect is the Bernoulli effect caused by the growing and collapsing bubbles in the nozzle. It is found that the characteristics of the flow change dramatically even when the upstream void fraction is very small. Two different flow regimes are found from the steady state solutions and are termed: quasi-steady and quasi-unsteady. The former is characterized by large spatial fluctuations downstream of the throat which are induced by the pulsations of the cavitation bubbles. The quasi-unsteady solutions correspond to flashing flow. Bifurcation occurs as the flow transitions from one regime to the other. An analytical expression for the critical bubble size at the bifurcation is obtained. Physical reasons for this quasi-static instability are also discussed.
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Ceccio, S. L., and C. E. Brennen. "Observations of the dynamics and acoustics of travelling bubble cavitation." Journal of Fluid Mechanics 233 (December 1991): 633–60. http://dx.doi.org/10.1017/s0022112091000630.
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Individual travelling cavitation bubbles generated on two axisymmetric headforms were detected using a surface electrode probe. The growth and collapse of the bubbles were studied photographically, and these observations are related to the pressure fields and viscous flow patterns associated with each headform. Measurements of the acoustic impulse generated by the bubble collapse are analysed and found to correlate with the maximum volume of the bubble for each headform. These results are compared to the observed bubble dynamics and numerical solutions of the Rayleigh–Plesset equation. Finally, the cavitation nuclei flux was measured and predicted cavitation event rates and bubble maximum size distributions are compared with the measurements of these quantities.
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Cheng, Feng, Weixi Ji, and Junhua Zhao. "Bubble–bubble interaction effects on multiple bubbles dynamics in an ultrasonic cavitation field." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 234, no. 7 (November 19, 2019): 1051–60. http://dx.doi.org/10.1177/1350650119886214.
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A vibratory erosion test rig is used to study the cavitation erosion of 6061 alloy. Some craters and material fracture are found on the specimen surface at the beginning of test. A cavitation model in an ultrasonic field is developed by applying the bubble–bubble interaction effect into Keller–Miksis equation to obtain the bubbles dynamic characteristics. The results reveal that the bubble cloud configuration is suitable for the explanation of cavitation erosion, and the erosion surfaces of the specimen were subjected to the effect of both massive bubbles collapsing, occurring in the thin liquid layer between the horn and the specimen. It is concluded that the optimal coupling strength of bubbles increases with the decrease of the bubble initial radius, and stable cavitation only occurs when the acoustic pressure amplitude is higher than a threshold value, which can well predict the experimental results.
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Lauterborn, Werner, and Claus-Dieter Ohl. "Cavitation bubble dynamics." Ultrasonics Sonochemistry 4, no. 2 (April 1997): 65–75. http://dx.doi.org/10.1016/s1350-4177(97)00009-6.
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Qin, Dui, Qingqin Zou, Shuang Lei, Wei Wang, and Zhangyong Li. "Cavitation Dynamics and Inertial Cavitation Threshold of Lipid Coated Microbubbles in Viscoelastic Media with Bubble–Bubble Interactions." Micromachines 12, no. 9 (September 18, 2021): 1125. http://dx.doi.org/10.3390/mi12091125.
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Encapsulated microbubbles combined with ultrasound have been widely utilized in various biomedical applications; however, the bubble dynamics in viscoelastic medium have not been completely understood. It involves complex interactions of coated microbubbles with ultrasound, nearby microbubbles and surrounding medium. Here, a comprehensive model capable of simulating the complex bubble dynamics was developed via taking the nonlinear viscoelastic behaviors of the shells, the bubble–bubble interactions and the viscoelasticity of the surrounding medium into account simultaneously. For two interacting lipid-coated bubbles with different initial radii in viscoelastic media, it exemplified that the encapsulating shell, the inter-bubble interactions and the medium viscoelasticity would noticeably suppress bubble oscillations. The inter-bubble interactions exerted a much stronger suppressing effect on the small bubble within the parameters examined in this paper, which might result from a larger radiated pressure acting on the small bubble due to the inter-bubble interactions. The lipid shells make the microbubbles exhibit two typical asymmetric dynamic behaviors (i.e., compression or expansion dominated oscillations), which are determined by the initial surface tension of the bubbles. Accordingly, the inertial cavitation threshold decreases as the initial surface tension increases, but increases as the shell elasticity and viscosity increases. Moreover, with the distance between bubbles decreasing and/or the initial radius of the large bubble increasing, the oscillations of the small bubble decrease and the inertial cavitation threshold increases gradually due to the stronger suppression effects caused by the enhanced bubble–bubble interactions. Additionally, increasing the elasticity and/or viscosity of the surrounding medium would also dampen bubble oscillations and result in a significant increase in the inertial cavitation threshold. This study may contribute to both encapsulated microbubble-associated ultrasound diagnostic and emerging therapeutic applications.
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De Chizelle, Y. Kuhn, S. L. Ceccio, and C. E. Brennen. "Observations and scaling of travelling bubble cavitation." Journal of Fluid Mechanics 293 (June 25, 1995): 99–126. http://dx.doi.org/10.1017/s0022112095001650.
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Recent observations of growing and collapsing bubbles in flows over axisymmetric headforms have revealed the complexity of the ‘micro-fluid-mechanics’ associated with these bubbles (van der Meulen & van Renesse 1989; Briancon-Marjollet et al. 1990; Ceccio & Brennen 1991). Among the complex features observed were the bubble-to-bubble and bubble-to-boundary-layer interactions which leads to the shearing of the underside of the bubble and alters the collapsing process. All of these previous tests, though, were performed on small headform sizes. The focus of this research is to analyse the scaling effects of these phenomena due to variations in model size, Reynolds number and cavitation number. For this purpose, cavitating flows over Schiebe headforms of different sizes (5.08, 25.4 and 50.8 cm in diameter) were studied in the David Taylor Large Cavitation Channel (LCC). The bubble dynamics captured using high-speed film and electrode sensors are presented along with the noise signals generated during the collapse of the cavities.In the light of the complexity of the dynamics of the travelling bubbles and the important bubble/bubble interactions, it is clear that the spherical Rayleigh-Plesset analysis cannot reproduce many of the phenomena observed. For this purpose an unsteady numerical code was developed which uses travelling sources to model the interactions between the bubble (or bubbles) and the pressure gradients in the irrotational flow outside the boundary layer on the headform. The paper compares the results of this numerical code with the present experimental results and demonstrates good qualitative agreement between the two.
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Altay, Rana, Abdolali K. Sadaghiani, M. Ilker Sevgen, Alper Şişman, and Ali Koşar. "Numerical and Experimental Studies on the Effect of Surface Roughness and Ultrasonic Frequency on Bubble Dynamics in Acoustic Cavitation." Energies 13, no. 5 (March 3, 2020): 1126. http://dx.doi.org/10.3390/en13051126.
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With many emerging applications such as chemical reactions and ultrasound therapy, acoustic cavitation plays a vital role in having improved energy efficiency. For example, acoustic cavitation results in substantial enhancement in the rates of various chemical reactions. In this regard, an applied acoustic field within a medium generates acoustic streaming, where cavitation bubbles appear due to preexisting dissolved gas in the working fluid. Upon cavitation inception, bubbles can undergo subsequent growth and collapse. During the last decade, the studies on the effects of different parameters on acoustic cavitation such as applied ultrasound frequency and power have been conducted. The bubble growth and collapse mechanisms and their distribution within the medium have been classified. Yet, more research is necessary to understand the complex mechanism of multi-bubble behavior under an applied acoustic field. Various parameters affecting acoustic cavitation such as surface roughness of the acoustic generator should be investigated in more detail in this regard. In this study, single bubble lifetime, bubble size and multi-bubble dynamics were investigated by changing the applied ultrasonic field. The effect of surface roughness on bubble dynamics was presented. In the analysis, images from a high-speed camera and fast video recording techniques were used. Numerical simulations were also done to investigate the effect of acoustic field frequency on bubble dynamics. Bubble cluster behavior and required minimum bubble size to be affected by the acoustic field were obtained. Numerical results suggested that bubbles with sizes of 50 µm or more could be aligned according to the radiation potential map, whereas bubbles with sizes smaller than 10 µm were not affected by the acoustic field. Furthermore, it was empirically proven that surface roughness has a significant effect on acoustic cavitation phenomena.
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Wang, Yi-Chun. "Effects of Nuclei Size Distribution on the Dynamics of a Spherical Cloud of Cavitation Bubbles." Journal of Fluids Engineering 121, no. 4 (December 1, 1999): 881–86. http://dx.doi.org/10.1115/1.2823550.
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The nonlinear dynamics of a spherical bubble cloud with nuclei size distribution are studied numerically. The spectrum of nuclei is assumed uniform initially. The simulations employ a nonlinear continuum bubbly mixture model with consideration of the presence of bubbles of different sizes. This model is then coupled with the Rayleigh-Plesset equation for the dynamics of bubbles. A numerical method based on the integral representation of the mixture continuity and momentum equations in the Lagrangian coordinates is developed to solve this set of integro-differential equations. Computational results show that the nuclei size distribution has significant effects on the cloud dynamics in comparison to the results for a single bubble size. One important effect is that the bubble collapse is always initiated near the surface of the cloud, even if the cloud has a very small initial void fraction. This effect has an important consequence, namely that the geometric focusing of the bubbly shock wave is always a part of the nonlinear dynamics associated with the collapse of a spherical cloud with nuclei size distribution. The strength of the shock and the oscillation structure behind the shock front are suppressed due to the effects of multiple bubble sizes. Far-field acoustic pressures radiated by two bubble clouds, one of equal-size bubbles and the other with bubble size distribution, are also compared. It is found that the cloud containing bubbles of different sizes emits a larger noise than the cloud of identical bubbles. Explanations for this effect are also presented.
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Lv, Liang, Xu LUO, Hongxia ZHANG, Bing CUI, and Lihai CHEN. "The Numerical Investigation on Bubble Interaction Dynamics in Hydrodynamic Cavitation." Mechanics 27, no. 2 (April 15, 2021): 115–21. http://dx.doi.org/10.5755/j02.mech.26187.
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Bubble-bubble interactions are of great importance for bubble dynamics. A mathematical model describing the dynamics of a cluster in hydrodynamic cavitation is presented. The interaction strength (i.e. the number density of bubbles) is introduced into Keller-Misis equation. Using this model, numerical investigations of bubble dynamics (i.e. radial motion and internal energy) of single bubble in a cluster have been made due to linear pressure gradient. With the increase of interaction strength, the times of bubble reaching the maximum and minimum radii are delayed. The more of bubbles are in a cluster, the more significant of the delay effect is. The maximum internal energy inside the bubble is closely related to interaction strength (i.e. positive correlation). Furthermore, the initial bubble radius and final recovered pressure of the orifice on bubble dynamics are quantitatively discussed. Based on numerical results, some references are put forward for optimize and manipulate of hydrodynamic cavitation reactor.
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Wang, Xiaoyu, Shenghao Zhou, Zumeng Shan, and Mingang Yin. "Investigation of Cavitation Bubble Dynamics Considering Pressure Fluctuation Induced by Slap Forces." Mathematics 9, no. 17 (August 26, 2021): 2064. http://dx.doi.org/10.3390/math9172064.
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Cavitation erosion is induced by the penetrating pressure from implosion of cavitation bubbles nearby solid boundary. The bubble evolution and the subsequent collapse pressure are especially important to evaluate the erosion degradation of solid boundary materials. The bubble dynamics equation taking into account the influence of distance between bubble and solid boundary is formulated to investigate the effect of boundary wall on bubble evolution process. The pressure fluctuation induced by slapping forces is adopted to evaluate the bubble dynamic characteristics. Negative pressure period which reflects the effect of vibration velocity and gap clearance also has large influence on bubble dynamics. The effects of standoff distance, initial radius and negative pressure period on bubble evolution and collapsing shock pressure are discussed. Maximum bubble radius increases with standoff distance and initial radius, while shock pressure increases with distance and decreases with bubble initial radius, and both of them increase with negative pressure period.
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Sedlář, Milan, Patrik Zima, and Martin Komárek. "Numerical Prediction of Erosive Potential of Unsteady Cavitating Flow around Hydrofoil." Applied Mechanics and Materials 565 (June 2014): 156–63. http://dx.doi.org/10.4028/www.scientific.net/amm.565.156.
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The paper attempts to assess the erosive potential of cavitation bubbles in unsteady flow of liquid over a prismatic hydrofoil using two-way coupling of the URANS and the Rayleigh-Plesset equations. The erosive potential of the cavitating flow is evaluated from the energy dissipated during the collapses of imploding cavitation bubbles near the solid surface of the hydrofoil. The bubbles are assumed spherical and the phase slip is neglected. Bubble fission is modelled using a simple break-up model. The interaction between bubbles is considered by superposing the pressure change due to pressure waves generated by collapsing bubbles and propagated in the computational domain over the local pressure in the liquid (external to the bubble). The rate of erosion of the solid material is not studied in this work. The flow is analysed using the in-house three-dimensional solver for unsteady turbulent flow with bubble dynamics. The results are demonstrated on the NACA 2412 hydrofoil with the incidence angle of 8 degrees and the cavitation number 1.37, which corresponds to the regime of oscillating partial cavity with periodic shedding of bubble cloud downstream of the cavity.
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Phan, Thanh-Hoang, Ebrahim Kadivar, Van-Tu Nguyen, Ould el Moctar, and Warn-Gyu Park. "Thermodynamic effects on single cavitation bubble dynamics under various ambient temperature conditions." Physics of Fluids 34, no. 2 (February 2022): 023318. http://dx.doi.org/10.1063/5.0076913.
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Thermodynamic characteristics and their effects on single cavitation bubble dynamics are important to elucidate the physical behaviors of cavitation phenomena. In this study, experimental and numerical methods were utilized to explore the thermodynamic effects on single cavitation bubble dynamics under various ambient temperature conditions. A series of experiments was performed to generate a single cavitation bubble at ambient temperatures between 20 and 80 °C using a laser-induced method and a high-speed camera to observe the dynamic behaviors of bubbles. By increasing the ambient temperature, a nonspherical bubble shape with a jet flow at the bubble rebound stage was observed. Next, the numerical simulation results in terms of the bubble radius and bubble shape were validated with the corresponding experimental data. Generally, the results exhibited reasonable agreement, particularly at the later collapse and rebound stages. Critical hydrodynamic and thermodynamic mechanisms over multiple oscillation stages at different ambient temperatures were analyzed. The bubble behaviors and their intensities were numerically quantified with respect to the bubble radius, collapsing time, internal pressure, internal temperature, and phase transition rate parameters. The results showed that the maximum bubble radius, first minimum bubble radius, and collapsing time increased with an increase in the ambient temperature. Nevertheless, the peak values of the internal pressure and internal temperature decreased with an increase in the ambient temperature. Generally, the bubble collapsed less violently at high temperatures than at low temperatures.
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Wang, Yi-Chun, and Christopher E. Brennen. "Numerical Computation of Shock Waves in a Spherical Cloud of Cavitation Bubbles." Journal of Fluids Engineering 121, no. 4 (December 1, 1999): 872–80. http://dx.doi.org/10.1115/1.2823549.
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The nonlinear dynamics of a spherical cloud of cavitation bubbles have been simulated numerically in order to learn more about the physical phenomena occurring in cloud cavitation. A finite cloud of nuclei is subject to a decrease in the ambient pressure which causes the cloud to cavitate. A subsequent pressure recovery then causes the cloud to collapse. This is typical of the transient behavior exhibited by a bubble cloud as it passes a body or the blade of a ship propeller. The simulations employ the fully nonlinear continuum bubbly mixture equations coupled with the Rayleigh-Plesset equation for the dynamics of bubbles. A Lagrangian integral method is developed to solve this set of equations. It was found that, with strong bubble interaction effects, the collapse of the cloud is accompanied by the formation of an inward propagating bubbly shock wave. A large pressure pulse is produced when this shock passes the bubbles and causes them to collapse. The focusing of the shock at the center of the cloud produces a very large pressure pulse which radiates a substantial impulse to the far field and provides an explanation for the severe noise and damage potential in cloud cavitation.
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Xing, Tao, Zhenyin Li, and Steven H. Frankel. "Numerical Simulation of Vortex Cavitation in a Three-Dimensional Submerged Transitional Jet." Journal of Fluids Engineering 127, no. 4 (April 7, 2005): 714–25. http://dx.doi.org/10.1115/1.1976742.
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Vortex cavitation in a submerged transitional jet is studied with unsteady three-dimensional direct numerical simulations. A locally homogeneous cavitation model that accounts for non-linear bubble dynamics and bubble/bubble interactions within spherical bubble clusters is employed. The velocity, vorticity, and pressure fields are compared for both cavitating and noncavitating jets. It is found that cavitation occurs in the cores of the primary vortical structures, distorting and breaking up the vortex ring into several sections. The velocity and transverse vorticity in the cavitating regions are intensified due to vapor formation, while the streamwise vorticity is weakened. An analysis of the vorticity transport equation reveals the influence of cavitation on the relative importance of the vortex stretching, baroclinic torque, and dilatation terms. Statistical analysis shows that cavitation suppresses jet growth and decreases velocity fluctuations within the vaporous regions of the jet.
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Ku, Garam, Cheolung Cheong, Hanshin Seol, and Hongseok Jeong. "Numerical investigation into effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wing." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 5 (August 1, 2021): 1813–17. http://dx.doi.org/10.3397/in-2021-1958.
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In this study, the effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wings are investigated using coupled Eulerian-Lagrangian method based on sequential application of Reynolds averaged Navier-Stokes (RANS) solver, bubble dynamics model and acoustic analogy. The bubble dynamics model used in the preceding study (Ku et al., 2020) is modified by including the gas pressure terms and the bubble collapse model, which depends on the timing and threshold of bubble collapse, the number, initial radius and location of divided bubbles. The validity of the modified bubble dynamics model is confirmed through its application to a benchmark problem where single bubble is triggered by laser. Then, the coupled Eulerian-Lagrangian method based on the modified bubble dynamic model is applied for the prediction of tip-vortex cavitation noise of NACA16-020 wing. The predicted results of the tip vortex pattern and acoustic pressure spectrum are compared with the measured results, which shows closer agreements between two results than those in the previous study.
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Li, Duan, Zhang, Tang, and Zhang. "Retardant Effects of Collapsing Dynamics of a Laser-Induced Cavitation Bubble Near a Solid Wall." Symmetry 11, no. 8 (August 15, 2019): 1051. http://dx.doi.org/10.3390/sym11081051.
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In the present paper, the dynamic behavior of cavitation bubbles near a wall is experimentally investigated with a focus on the retardant effects of the wall on the collapsing dynamics of the bubble. In the present experiments, a cavitation bubble is generated by a focused laser beam with its behavior recorded through high-speed photography. During the data analysis, the influences of non-dimensional bubble–wall distance on the bubble collapsing dynamics are qualitatively and quantitatively investigated in terms of the interface evolution, the velocities of the poles, and the movement of the bubble centroid. Our results reveal that the presence of the wall could significantly affect the collapsing characteristics, leading to a dramatic difference between the moving velocities of interfaces near and away from the wall. With the decrease of the bubble–wall distance, the effects will be gradually strengthened with a rapid movement of the bubble centroid during the final collapse. Finally, a physical interpretation of the phenomenon is given based on the bubble theory, together with a rough estimation of the induced water hammer pressure by the bubble collapse.
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Aganin, A. A., A. I. Davletshin, and T. F. Khalitova. "Numerical simulation of bubble dynamics in central region of streamer." Multiphase Systems 13, no. 3 (June 29, 2018): 11–22. http://dx.doi.org/10.21662/mfs2018.3.002.
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A mathematical model and a numerical technique for studying strong expansion and collapse of cavitation bubbles located in the central region of a streamer where the bubbles are almost motionless are developed. They are essentially efficient combinations of the models and techniques previously created by the authors for calculating the dynamics of interacting weakly-non-spherical bubbles in a streamer and the dynamics of a single axisymmetric bubble. The first model and technique are applied at the low-speed stage of expansion and compression of bubbles where their hydrodynamic interaction is significant. The second ones are used at the final high-speed stage of their collapse where the interaction is inessential. The simplest case of the streamer comprising three bubbles is considered as an example to illustrate the features of the developed model and numerical technique. It is shown that under the strong expansion and collapse of an initially spherical cavitation bubble, the presence of neighboring bubbles can substantially deflect the bubble cavity vapor dynamics from what is realized inside a similar but single bubble.
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Zhu, Xi Jing, Ce Guo, and Jian Qing Wang. "The Pressure Field Radiated by Cavitation Bubble in the Grinding Area of Power Ultrasonic Honing." Advanced Materials Research 1027 (October 2014): 44–47. http://dx.doi.org/10.4028/www.scientific.net/amr.1027.44.
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The pressure field induced by cavitaion bubble is responsible for the grinding mechanism and the cutting chatter of power ultrasonic honing. Based on the cavitation bubble dynamics model in the grinding area of power ultrasonic honing, the radiation pressure field of cavitation bubble was established. Experimental results show that the bubble is distributed in the grinding area like honeycomb and the size is about 10μm. Numerical simulation of dynamics and pressure field of cavitation bubble was performed. Numerical results show the dynamic behavior of cavitation bubble presents grow, expend and collapse under an acoustic cycle. However the expansion amplitude of bubble can be decreased and the collapse time can be extended and even collapse after several acoustic cycles with increasing ambient bubble radius. The bubble radiation pressure during collapsing bubble increases with increasing ultrasonic amplitude and ultrasonic frequency. And the pressure value of collapsing bubble is about 10Mpa which is more an order of magnitude than atmospheric pressure.
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Wu, Hao, Tianshu Zhang, Xiaochen Lai, Haixia Yu, Dachao Li, Hao Zheng, Hui Chen, Claus-Dieter Ohl, and Yuanyuan Li. "Influence of Surface Tension on Dynamic Characteristics of Single Bubble in Free-Field Exposed to Ultrasound." Micromachines 13, no. 5 (May 17, 2022): 782. http://dx.doi.org/10.3390/mi13050782.
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The motion of bubbles in an ultrasonic field is a fundamental physical mechanism in most applications of acoustic cavitation. In these applications, surface-active solutes, which could lower the surface tension of the liquid, are always utilized to improve efficiency by reducing the cavitation threshold. This paper examines the influence of liquids’ surface tension on single micro-bubbles motion in an ultrasonic field. A novel experimental system based on high-speed photography has been designed to investigate the temporary evolution of a single bubble in the free-field exposed to a 20.43 kHz ultrasound in liquids with different surface tensions. In addition, the R-P equations in the liquid with different surface tension are solved. It is found that the influences of the surface tension on the bubble dynamics are obvious, which reflect on the changes in the maximum size and speed of the bubble margin during bubble oscillating, as well as the weaker stability of the bubble in the liquid with low surface tension, especially for the oscillating bubble with higher speed. These effects of the surface tension on the bubble dynamics can explain the mechanism of surfactants for promoting acoustic cavitation in numerous application fields.
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Ma, Chunlong, Dongyan Shi, Yingyu Chen, Xiongwei Cui, and Mengnan Wang. "Experimental Research on the Influence of Different Curved Rigid Boundaries on Electric Spark Bubbles." Materials 13, no. 18 (September 6, 2020): 3941. http://dx.doi.org/10.3390/ma13183941.
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It is well known that the bubble dynamics and load characteristics of cavitation bubbles depend to a great extent on their proximity to the boundary. The purpose of this study is to explore the relationship between the boundary curvature and bubble dynamics, as well as the load characteristics, and summarize the relevant change laws. This study takes three hemispheres of different curvatures and one flat board as its main research boundaries. The hemisphere was chosen as the curved surface boundary because the hemisphere represents the simplest type of curved surface boundary. This method allowed us to easily observe the experimental results and summarize the change laws of bubble dynamics and load characteristics. A high voltage electricity of 400 V was used to produce stable and repeatable electric spark bubbles in this experiment. Since the pulsation time of the bubbles is very short, we used a high-speed camera to acquire the necessary photographs. We also used a Hopkinson bar (HPB) to measure the bubble collapse load. Suppose that the dimensionless parameter of curvature is ζ and the dimensionless parameter of the explosion distance is γ. By summarizing the 44 groups of the experimental results under different combinations of ζ and γ, we found that the cavitation bubble dynamics and loading characteristics are affected by ζ. With an increase of ζ, the shockwave load and bubble collapse load will decrease. In addition, in terms of load characteristics, this study further verified the change trend of the shockwave load and bubble collapse load with γ. For the bubble shrink shape, this paper illustrates the relationship between the bubble’s shrink shape and its shrinkage speed. Four typical bubble shrink shapes are summarized. The effects of different ζ and γ values on the jet are preliminarily explored using the experimental results, and, by considering the experimental results, the developmental trends of the time of the bubble’s first pulsation period are discussed.
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Crespo, A., F. Castro, F. Manuel, and J. Herna´ndez. "Dynamics of an Elongated Bubble During Collapse." Journal of Fluids Engineering 112, no. 2 (June 1, 1990): 232–37. http://dx.doi.org/10.1115/1.2909393.
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An analytical model is presented to describe the collapse of an elongated bubble, which appears in the core of a cavitating vortex. The flow field is assumed to be irrotational, due to a sink line. The kinematic and dynamic conditions are applied only at the tip and in the middle of the bubble surface. This simplified theory must retain losses of mechanical energy near the tips of the bubble, which are due to a microjet. In order to check the validity of this model, the irrotational flow equations have been solved numerically by using a panel method; the numerical results agree with the analytical ones and confirm the existence of the microjet at the tip. The agreement with experimental results is also good. For very slender bubbles the speed near the tips becomes very large, and this may be cause of cavitation damage. A simplified approach is proposed to explain the flow in the microjet.
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Chahine, G. L., and Y. T. Shen. "Bubble Dynamics and Cavitation Inception in Cavitation Susceptibility Meters." Journal of Fluids Engineering 108, no. 4 (December 1, 1986): 444–52. http://dx.doi.org/10.1115/1.3242602.
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To improve the understanding of the scaling effects of nuclei on cavitation inception, bubble dynamics, multibubble interaction effects, and bubble-mean flow interaction in a venturi Cavitation Susceptibility Meter are considered theoretically. The results are compared with classical bubble static equilibrium predictions. In a parallel effort, cavitation susceptibility measurements of ocean and laboratory water were carried out using a venturi device. The measured cavitation inception indices were found to relate to the measured microbubble concentration. The relationship between the measured cavitation inception and bubble concentration and distribution can be explained by using the theoretical predictions. A tentative explanation is given for the observation that the number of cavitation bursting events measured by an acoustic device is sometimes an order of magnitude lower than the number of microbubbles measured by the light scattering detector. The questions addressed here add to the fundamental knowledge needed if the cavitation susceptibility meter is to be used effectively for the measurement of microbubble size distributions.
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d’Agostino, Luca, and Fabio Burzagli. "On the Stability of Parallel Bubbly Cavitating Flows." Journal of Fluids Engineering 122, no. 3 (April 25, 2000): 471–80. http://dx.doi.org/10.1115/1.1287036.
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This paper illustrates the effects of the dynamics of bubbles with arbitrary vapor-gas contents on the inviscid and viscous stability of two-dimensional parallel bubbly flows of low void fraction. The linear perturbation equations derived for the stability analysis include the effects of bubble compressibility, inertia, and energy dissipation due to the viscosity of the liquid and the transfer of heat and mass as a consequence of compression/expansion of the noncondensable gas and evaporation/condensation of the vapor contained in the bubbles. Numerical solution of the spatial stability problem for two-dimensional inviscid shear layers and Blasius boundary layers confirms that the presence of the dispersed phase is generally in favor of stability. Significant deviations from the classical results for compressible and incompressible single phase fluids are observed, especially when the occurrence of large compliant and/or resonant oscillations of the bubbles greatly enhances their dynamic coupling with the perturbation field. More importantly, the present analysis points out some major differences in the stability of parallel flows with noncondensable gas bubbles with respect to cavitating flows containing bubbles with a dominant content of vapor. Unconditional stability is predicted in the travelling bubble cavitation limit for low pressures and high vapor mass fraction of the bubble contents. Results are shown to illustrate these effects for some representative flow configurations and conditions. [S0098-2202(00)00603-9]
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Menzl, Georg, Miguel A. Gonzalez, Philipp Geiger, Frédéric Caupin, José L. F. Abascal, Chantal Valeriani, and Christoph Dellago. "Molecular mechanism for cavitation in water under tension." Proceedings of the National Academy of Sciences 113, no. 48 (November 1, 2016): 13582–87. http://dx.doi.org/10.1073/pnas.1608421113.
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Despite its relevance in biology and engineering, the molecular mechanism driving cavitation in water remains unknown. Using computer simulations, we investigate the structure and dynamics of vapor bubbles emerging from metastable water at negative pressures. We find that in the early stages of cavitation, bubbles are irregularly shaped and become more spherical as they grow. Nevertheless, the free energy of bubble formation can be perfectly reproduced in the framework of classical nucleation theory (CNT) if the curvature dependence of the surface tension is taken into account. Comparison of the observed bubble dynamics to the predictions of the macroscopic Rayleigh–Plesset (RP) equation, augmented with thermal fluctuations, demonstrates that the growth of nanoscale bubbles is governed by viscous forces. Combining the dynamical prefactor determined from the RP equation with CNT based on the Kramers formalism yields an analytical expression for the cavitation rate that reproduces the simulation results very well over a wide range of pressures. Furthermore, our theoretical predictions are in excellent agreement with cavitation rates obtained from inclusion experiments. This suggests that homogeneous nucleation is observed in inclusions, whereas only heterogeneous nucleation on impurities or defects occurs in other experiments.
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KLASEBOER, EVERT, SIEW WAN FONG, CARY K. TURANGAN, BOO CHEONG KHOO, ANDREW J. SZERI, MICHAEL L. CALVISI, GEORGY N. SANKIN, and PEI ZHONG. "Interaction of lithotripter shockwaves with single inertial cavitation bubbles." Journal of Fluid Mechanics 593 (November 23, 2007): 33–56. http://dx.doi.org/10.1017/s002211200700852x.
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The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave-bubble interaction are discussed.
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PHILIPP, A., and W. LAUTERBORN. "Cavitation erosion by single laser-produced bubbles." Journal of Fluid Mechanics 361 (April 25, 1998): 75–116. http://dx.doi.org/10.1017/s0022112098008738.
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In order to elucidate the mechanism of cavitation erosion, the dynamics of a single laser-generated cavitation bubble in water and the resulting surface damage on a flat metal specimen are investigated in detail. The characteristic effects of bubble dynamics, in particular the formation of a high-speed liquid jet and the emission of shock waves at the moment of collapse are recorded with high-speed photography with framing rates of up to one million frames/s. Damage is observed when the bubble is generated at a distance less than twice its maximum radius from a solid boundary (γ=2, where γ=s/Rmax, s is the distance between the boundary and the bubble centre at the moment of formation and Rmax is the maximum bubble radius). The impact of the jet contributes to the damage only at small initial distances (γ[les ]0.7). In this region, the impact velocity rises to 83 m s−1, corresponding to a water hammer pressure of about 0.1 GPa, whereas at γ>1, the impact velocity is smaller than 25 m s−1. The largest erosive force is caused by the collapse of a bubble in direct contact with the boundary, where pressures of up to several GPa act on the material surface. Therefore, it is essential for the damaging effect that bubbles are accelerated towards the boundary during the collapse phases due to Bjerknes forces. The bubble touches the boundary at the moment of second collapse when γ<2 and at the moment of first collapse when γ<1. Indentations on an aluminium specimen are found at the contact locations of the collapsing bubble. In the range γ=1.7 to 2, where the bubble collapses mainly down to a single point, one pit below the bubble centre is observed. At γ[les ]1.7, the bubble shape has become toroidal, induced by the jet flow through the bubble centre. Corresponding to the decay of this bubble torus into multiple tiny bubbles each collapsing separately along the circumference of the torus, the observed damage is circular as well. Bubbles in the ranges γ[les ]0.3 and γ=1.2 to 1.4 caused the greatest damage. The overall diameter of the damaged area is found to scale with the maximum bubble radius. Owing to the possibility of generating thousands of nearly identical bubbles, the cavitation resistance of even hard steel specimens can be tested.
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Hsiao, Chao-Tsung, and Laura L. Pauley. "Study of Tip Vortex Cavitation Inception Using Navier-Stokes Computation and Bubble Dynamics Model." Journal of Fluids Engineering 121, no. 1 (March 1, 1999): 198–204. http://dx.doi.org/10.1115/1.2822002.
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The Rayleigh-Plesset bubble dynamics equation coupled with the bubble motion equation developed by Johnson and Hsieh was applied to study the real flow effects on the prediction of cavitation inception in tip vortex flows. A three-dimensional steady-state tip vortex flow obtained from a Reynolds-Averaged Navier-Stokes computation was used as a prescribed flow field through which the bubble was passively convected. A “window of opportunity” through which a candidate bubble must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial bubble sizes. It was found that bubbles with larger initial size can be entrained into the tip-vortex core from a larger window size and also had a higher cavitation inception number.
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GONZALEZ-AVILA, SILVESTRE ROBERTO, EVERT KLASEBOER, BOO CHEONG KHOO, and CLAUS-DIETER OHL. "Cavitation bubble dynamics in a liquid gap of variable height." Journal of Fluid Mechanics 682 (June 21, 2011): 241–60. http://dx.doi.org/10.1017/jfm.2011.212.
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We report on an experimental study of cavitation bubble dynamics within sub-millimetre-sized narrow gaps. The gap height is varied, while the position of the cavitation event is fixed with respect to the lower gap wall. Four different sizes of laser-induced cavitation bubbles are studied using high-speed photography of up to 430,000 frames per second. We find a strong influence of the gap height, H, on the bubble dynamics, in particular on the collapse scenario. Also, similar bubble dynamics was found for the same non-dimensional gap height η = H/Rx, where Rx is the maximum radius in the horizontal direction. Three scenarios are observed: neutral collapse at the gap centre, collapse onto the lower wall and collapse onto the upper wall. For intermediate gap height the bubble obtains a conical shape 1.4 < η < 7.0. For large distances, η > 7.0, the bubble no longer feels the presence of the upper wall and collapses hemispherically. The collapse time increases with respect to the expansion time for decreasing values of η. Due to the small scales involved, the final stage of the bubble collapse could not be resolved temporally and numerical simulations were performed to elucidate the details of the flow. The simulations demonstrate high-speed jetting towards the upper and lower walls and complex bubble splitting for neutral collapses.
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BRENNER, MICHAEL P. "Cavitation in linear bubbles." Journal of Fluid Mechanics 632 (July 27, 2009): 1–4. http://dx.doi.org/10.1017/s0022112009008167.
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Recent work has developed a beautiful model system for studying the energy focusing and heating power of collapsing bubbles. The bubble is effectively one-dimensional and the collapse and heating can be quantitatively measured. Thermal effects are shown to play an essential role in the time-dependent dynamics.
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CHOI, JAEHYUG, CHAO-TSUNG HSIAO, GEORGES CHAHINE, and STEVEN CECCIO. "Growth, oscillation and collapse of vortex cavitation bubbles." Journal of Fluid Mechanics 624 (April 10, 2009): 255–79. http://dx.doi.org/10.1017/s0022112008005430.
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The growth, oscillation and collapse of vortex cavitation bubbles are examined using both two- and three-dimensional numerical models. As the bubble changes volume within the core of the vortex, the vorticity distribution of the surrounding flow is modified, which then changes the pressures at the bubble interface. This interaction can be complex. In the case of cylindrical cavitation bubbles, the bubble radius will oscillate as the bubble grows or collapses. The period of this oscillation is of the order of the vortex time scale, τV = 2πrc/uθ, max, where rc is the vortex core radius and uθ, max is its maximum tangential velocity. However, the period, oscillation amplitude and final bubble radius are sensitive to variations in the vortex properties and the rate and magnitude of the pressure reduction or increase. The growth and collapse of three-dimensional bubbles are reminiscent of the two-dimensional bubble dynamics. But, the axial and radial growth of the vortex bubbles are often strongly coupled, especially near the axial extents of the bubble. As an initially spherical nucleus grows into an elongated bubble, it may take on complex shapes and have volume oscillations that also scale with τV. Axial flow produced at the ends of the bubble can produce local pinching and fission of the elongated bubble. Again, small changes in flow parameters can result in substantial changes to the detailed volume history of the bubbles.
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Shah, Yash, Andrea Vacca, and Sadegh Dabiri. "Air Release and Cavitation Modeling with a Lumped Parameter Approach Based on the Rayleigh–Plesset Equation: The Case of an External Gear Pump." Energies 11, no. 12 (December 12, 2018): 3472. http://dx.doi.org/10.3390/en11123472.
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In this paper, a novel approach for the simulation of cavitation and aeration in hydraulic systems using the lumped parameter method is presented. The presented approach called the Hybrid Rayleigh–Plesset Equation model is derived from the Rayleigh–Plesset Equation representative of bubble dynamics and overcomes several shortcomings present in existing lumped parameter based cavitation modeling approaches. Models based on static approximations do not consider the non-equilibrium effects of phase change on the system and incorrectly predict the system dynamics. On the other hand, the existing dynamic cavitation modeling strategies account for the non-equilibrium effects of phase change but express the evolution of phases through approximations of the Rayleigh–Plesset Equation (such as exclusion of nonlinear interactions in bubble dynamics), which often lead to physically unrealistic time-scales of bubble growth or dissolution. This paper presents a dynamic model for cavitation which is capable of predicting cavitation in hydraulic systems while preserving the nonlinear dynamics arising from the Rayleigh–Plesset Equation. The derived model determines the evolution of phases in terms of physically realizable parameters such as the bubble radius and the nuclei density, which can be estimated or determined experimentally. The paper demonstrates the effectiveness of the derived modeling approach with the help of numerical simulations of an External Gear Machine. Results from the simulations employing the proposed model are compared with an existing dynamic cavitation modeling approach and validated with experimental results over a range of dynamic parameters.
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Vogel, A., W. Lauterborn, and R. Timm. "Optical and acoustic investigations of the dynamics of laser-produced cavitation bubbles near a solid boundary." Journal of Fluid Mechanics 206 (September 1989): 299–338. http://dx.doi.org/10.1017/s0022112089002314.
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The dynamics of laser-produced cavitation bubbles near a solid boundary and its dependence on the distance between bubble and wall are investigated experimentally. It is shown by means of high-speed photography with up to 1 million frames/s that jet and counterjet formation and the development of a ring vortex resulting from the jet flow are general features of the bubble dynamics near solid boundaries. The fluid velocity field in the vicinity of the cavitation bubble is determined with time-resolved particle image velocimetry. A comparison of path lines deduced from successive measurements shows good agreement with the results of numerical calculations by Kucera & Blake (1988). The pressure amplitude, the profile and the energy of the acoustic transients emitted during spherical bubble collapse and the collapse near a rigid boundary are measured with a hydrophone and an optical detection technique. Sound emission is the main damping mechanism in spherical bubble collapse, whereas it plays a minor part in the damping of aspherical collapse. The duration of the acoustic transients is 20-30 ns. The highest pressure amplitudes at the solid boundary have been found for bubbles attached to the boundary. The pressure inside the bubble and at the boundary reaches about 2.5 kbar when the maximum bubble radius is 3.5 mm. The results are discussed with respect to the mechanism of cavitation erosion.
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Church, Charles C., Sean M. Cordry, and Lawrence A. Crum. "ESWL and cavitation bubble dynamics." Journal of the Acoustical Society of America 90, no. 4 (October 1991): 2338. http://dx.doi.org/10.1121/1.402210.
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An, Yu. "Nonlinear bubble dynamics of cavitation." Journal of the Acoustical Society of America 131, no. 4 (April 2012): 3227. http://dx.doi.org/10.1121/1.4708035.
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Li, Zehao, Zhigang Zuo, and Zhongdong Qian. "A Venturi tube design for studying travelling bubble cavitation." Journal of Physics: Conference Series 2217, no. 1 (April 1, 2022): 012023. http://dx.doi.org/10.1088/1742-6596/2217/1/012023.
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Abstract Travelling bubble cavitation always appears in forms of nearly spherical travelling bubbles. These bubbles grow from the freestream/surface nuclei in the low-pressure region in the flow channel. As the inception of travelling bubble cavitation is very sensitive to the boundary layer flow, attached cavitation would be likely to appear simultaneously if the flow is not well-controlled. In this study, based on the interaction between cavitation inception and boundary layer, a Venturi tube for studying travelling bubble cavitation is designed with the aid of a computational fluid dynamics (CFD) approach. The flow channel of this Venturi tube is composed of an inlet straight pipe (10 mm × 10 mm square), a contraction section, a throat section (5 mm × 5 mm square) and two diffuser sections (diffuser 1 and diffuser 2). For visualization convenience, each cross section of the Venturi tube is square. From CFD results, no flow separation occurs near the throat section and the adverse pressure gradient is relatively small, which indicates attached cavitation may not occur. The manufactured Venturi tube is installed in a blow-down type tunnel and tested with Reynolds number at roughly 3 - 3.75 × 104 and the pressure recovery number at 2.95 - 4.41. The velocity of the Venturi inlet varies from about 6 m/s to 7.5 m/s. Experiment results shows travelling bubble cavitation can be generated successfully and pure travelling bubble cavitation inception is achieved in this Venturi tube. The formation of travelling bubbles is recorded by a Phantom VEO 710L high-speed camera with framing rate of 24000 fps.
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Liu, Gang, Qiang Fu, and Junjun Kang. "Cavitation and Negative Pressure: A Flexible Water Model Molecular Dynamics Simulation." International Journal of Statistics and Probability 8, no. 2 (February 22, 2019): 172. http://dx.doi.org/10.5539/ijsp.v8n2p172.
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The critical negative pressure for cavitation in water has been theoretically predicted to be in the range of -100 to -200 MPa at room temperature, whereas values around -30 MPa have been obtained by many experiments. The discrepancy has yet to be resolved. Molecular dynamics (MD) is an effective method of observing bubble nucleation, however, most MD simulations use a rigid water model and do not take the effects of intermolecular vibrations into account. In this manuscript we perform MD simulations to study cavitation in water by using a TIP4P/2005f model under volumecontrolled stretching. It is found that the critical negative pressure of water was -168 MPa in the simulation and the critical negative pressure of water containing 50 oxygen molecules was -150 MPa. Hydrogen bonds played a major role in the cavitation process: the breaking of hydrogen bonds promoted bubble generation and growth. The O-H bond could release energy to increase the amount of potential energy in the system, so that cavitation was more likely to occur. When cavitation occurred, the O-H bond could absorb energy to reduce the amount of potential energy in the system, which will promote the growth of bubbles, and stabilise the cavitation bubbles.
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Maeda, Kazuki, and Tim Colonius. "Bubble cloud dynamics in an ultrasound field." Journal of Fluid Mechanics 862 (January 16, 2019): 1105–34. http://dx.doi.org/10.1017/jfm.2018.968.
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The dynamics of bubble clouds induced by high-intensity focused ultrasound is investigated in a regime where the cloud size is similar to the ultrasound wavelength. High-speed images show that the cloud is asymmetric; the bubbles nearest the source grow to a larger radius than the distal ones. Similar structures of bubble clouds are observed in numerical simulations that mimic the laboratory experiment. To elucidate the structure, a parametric study is conducted for plane ultrasound waves with various amplitudes and diffuse clouds with different initial void fractions. Based on an analysis of the kinetic energy of liquid induced by bubble oscillations, a new scaling parameter is introduced to characterize the dynamics. The new parameter generalizes the cloud interaction parameter originally introduced by d’Agostino & Brennen (J. Fluid Mech., vol. 199, 1989, pp. 155–176). The dynamic interaction parameter controls the energy localization and consequent anisotropy of the cloud. Moreover, the amplitude of the far-field, bubble-scattered acoustics is likewise correlated with the proposed parameter. Findings of the present study not only shed light on the physics of cloud cavitation, but may also be of use for the quantification of the effects of cavitation on outcomes of ultrasound therapies including high-intensity focused ultrasound-based lithotripsy.
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Lee, Insu, Sunho Park, Woochan Seok, and Shin Hyung Rhee. "A Study on the Cavitation Model for the Cavitating Flow Analysis around the Marine Propeller." Mathematical Problems in Engineering 2021 (June 17, 2021): 1–8. http://dx.doi.org/10.1155/2021/2423784.
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In this study, a cavitation model for propeller analysis was selected using computational fluid dynamics (CFD), and the model was applied to the cavitating flow around the Potsdam Propeller Test Case (PPTC) propeller. The cavitating flow around the NACA 66 hydrofoil was analyzed to select a cavitation model suitable for propeller analysis among various cavitation models. The present and the experimental results were compared to select a cavitation model that would be applied to propeller cavitation analysis. Although the CFD results using the selected cavitation model showed limitations in estimating some of the foam cavitation and bubble cavitation identified in the experimental results, it was identified that foam cavitation and sheet cavitation around the tip were well simulated.
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Wang, Tianhao, and Linya Chen. "Thermodynamic Behavior and Energy Transformation Mechanism of the Multi-Period Evolution of Cavitation Bubbles Collapsing near a Rigid Wall: A Numerical Study." Energies 16, no. 3 (January 17, 2023): 1048. http://dx.doi.org/10.3390/en16031048.
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The dynamic behavior and energy transformation mechanism of the multi-period evolution of bubbles collapsing near a wall have been essential considerations in bubble dynamics research. In this study, a compressible two-phase solver considering thermodynamics and phase transitions is developed on OpenFOAM (version v2112). This model is validated via comparison with analytical solutions and experimental results. The dynamics of the multi-period evolution of bubbles collapse process at different dimensionless stand-off distances (γ) were accurately reproduced. The results indicate that the shock wave emitted by the collapse of cavitation bubbles impacts the wall, causing the fluid temperature along the wall to increase. Moreover, the liquid jet has a dual effect on the wall temperature increase, depending on the initial stand-off distance between the bubble and the wall. When γ is small, the jet carries the low-temperature fluid to occupy the high-temperature region, and when γ is large, the jet carries the high-temperature fluid to occupy the low-temperature region. Compared with the mechanisms above of wall temperature increase, the collapse process of cavitation, when directly attached to the wall, increases the fluid temperature along the wall more significantly. Additionally, an energy transformation mechanism is proposed considering the internal bubble energy based on the analysis of the internal bubble energy and acoustic radiation energy with different γ values. Both the internal and acoustic radiation energy initially decreased and subsequently increased with increasing γ values. These findings provide deeper insights into the near-wall collapsing cavitation process mechanism.
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Huang, Yong Chun, Yu Wu, and Feng Yang. "Numerical Simulation on the Dynamics for the Ultrasonic Cavitation Bubble in Chitosan Solution." Applied Mechanics and Materials 275-277 (January 2013): 628–34. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.628.
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In order to understand the influencing factors and laws on the ultrasonic cavitation dynamics in chitosan solution, numerical simulation of cavitation bubble motion had been performed based on Rayleigh-Plesset equation and the equation was solved by using 4~5 order Runge–Kutta algorithm. By numerical simulation the effects of frequency and intensity of ultrasonic, ambient pressure, initial bubble radius, concentration and temperature of solution, dual-frequency ultrasonic on the motion of cavitation bubble were discussed. The results show that for improving the effect of cavitation in chitosan solution, ultrasonic cavitation should be under the conditions of lower frequency, lower intensity, lower ambient pressure, smaller initial cavitation bubble, moderate temperature of solution and lower concentration. It is also found that the cavitation intensity due to dual-frequency ultrasonic is stronger than that of single-frequency ultrasonic.
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Blake, J. R. "The Kelvin impulse: application to cavitation bubble dynamics." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 30, no. 2 (October 1988): 127–46. http://dx.doi.org/10.1017/s0334270000006111.
Full textAbstract:
AbstractThe Kelvin impulse is a particularly valuable dynamical concept in unsteady fluid mechanics, with Benjamin and Ellis [2] appearing to be the first to have realised its value in cavitation bubble dynamics. The Kelvin impulse corresponds to the apparent inertia of the cavitation bubble and, like the linear momentum of a projectile, may be used to determine aspect It is defined aswhere ρ is the fluid density, ø is the velocity potential, S is the surface of the cavitation bubble and n is the outward normal to the fluid. Contributions to the Kelvin impulse may come from the presence of nearby boundaries and the ambient velocity and pressure field. With this number of mechanisms contributing to its development, the Kelvin impulse may change sign during the lifetime of the bubble. After collapse of the bubble, it needs to be conserved, usually in the form of a ring vortex. The Kelvin impulse is likely to provide valuable indicators as to the physical properties required of boundaries in order to reduce or eliminate cavitation damage. Comparisons are made against available experimental evidence.