Numerical simulation of traveling bubble cavitation

2006 ◽  
Vol 16 (4) ◽  
pp. 393-416 ◽  
Author(s):  
Sunil Mathew ◽  
Theo G. Keith Theo G. Keith ◽  
Efstratios Nikolaidis
Keyword(s):  
Cavitation Bubble ◽  
Bubble Radius ◽  
Random Variable ◽  
Bubble Collapse ◽  
Maximum Pressure ◽  
Local Pressure ◽  
New Approach ◽  
Content Type ◽  
Collapse Pressure ◽  
Bubble Cavitation

PurposeThe purpose is to present a new approach for studying the phenomenon of traveling bubble cavitation.Design/methodology/approachA flow around a rigid, 2D hydrofoil (NACA‐0012) with a smooth surface is analyzed computationally. The Rayleigh‐Plesset equation is numerically integrated to simulate the growth and collapse of a cavitation bubble moving in a varying pressure field. The analysis is performed for both incompressible and compressible fluid cases. Considering the initial bubble radius as a uniformly distributed random variable, the probability density function of the maximum collapse pressure is determined.FindingsThe significance of the liquid compressibility during bubble collapse is illustrated. Furthermore, it is shown that the initial size of the bubble has a significant effect on the maximum pressure generated during the bubble collapse. The maximum local pressure developed during cavitation bubble collapse is of the order of 104 atm.Research limitations/implicationsA single bubble model that does not account for the effect of neighboring bubbles is used in this analysis. A spherical bubble is assumed.Originality/valueA new approach has been developed to simulate traveling bubble cavitation by interfacing a CFD solver for simulating a flow with a program simulating the growth and collapse of the bubble. Probabilistic analysis of the local pressure due to bubble collapse has been performed.

Cavitation erosion behavior of hydraulic concrete under high-speed flow

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xin Wang ◽  
Ting-Qiang Xie
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Cavitation Erosion ◽  
Concrete Strength ◽  
Bubble Collapse ◽  
High Speed Flow ◽  
Content Type ◽  
Erosion Behavior ◽  
Hydraulic Concrete ◽  
Speed Flow

Purpose Cavitation erosion has always been a common technical problem in a hydraulic discharging structure. This paper aims to investigate the cavitation erosion behavior of hydraulic concrete under high-speed flow. Design/methodology/approach A high-speed and high-pressure venturi cavitation erosion generator was used to simulate the strong cavitation. The characteristics of hydrodynamic loads of cavitation bubble collapse zone, the failure characteristics and the erosion development process of concrete were investigated. The main influencing factors of cavitation erosion were discussed. Findings The collapse of the cavitation bubble group produced a high frequency, continuous and unsteady pulse load on the wall of concrete, which was more likely to cause fatigue failure of concrete materials. The cavitation action position and the main frequency of impact load were greatly affected by the downstream pressure. A power exponential relationship between cavitation load, cavitation erosion and flow speed was observed. With the increase of concrete strength, the degree of damage of cavitation erosion was approximately linearly reduced. Originality/value After cavitation erosion, a skeleton structure was formed by the accumulation of granular particles, and the relatively independent bulk structure of the surface differed from the flake structure formed after abrasion.

Modelling of material pitting from cavitation bubble collapse

2014 ◽  
Vol 755 ◽  
pp. 142-175 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
A. Jayaprakash ◽  
A. Kapahi ◽  
J.-K. Choi ◽  
Georges L. Chahine
Keyword(s):  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Numerical Approach ◽  
Bubble Collapse ◽  
Material Surface ◽  
Collapse Pressure ◽  
Flow Solver ◽  
Incompressible Boundary ◽  
The Impact ◽  
Impulsive Pressure

AbstractMaterial pitting from cavitation bubble collapse is investigated numerically including two-way fluid–structure interaction (FSI). A hybrid numerical approach which links an incompressible boundary element method (BEM) solver and a compressible finite difference flow solver is applied to capture non-spherical bubble dynamics efficiently and accurately. The flow codes solve the fluid dynamics while intimately coupling the solution with a finite element structure code to enable simulation of the full FSI. During bubble collapse high impulsive pressures result from the impact of the bubble re-entrant jet on the material surface and from the collapse of the remaining bubble ring. A pit forms on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress. The results depend on bubble dynamics parameters such as the size of the bubble at its maximum volume, the bubble standoff distance from the material wall, and the pressure driving the bubble collapse. The effects of these parameters on the re-entrant jet, the following bubble ring collapse pressure, and the generated material pit characteristics are investigated.

Cavitation Bubble Collapse Near a Heated Wall and Its Effect on the Heat Transfer

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Bin Liu ◽  
Jun Cai ◽  
Xiulan Huai ◽  
Fengchao Li
Keyword(s):  
Heat Transfer ◽  
Cavitation Bubble ◽  
Stokes Equations ◽  
Saturated Vapor ◽  
Bubble Diameter ◽  
Bubble Radius ◽  
Heated Wall ◽  
Bubble Collapse ◽  
Flow State ◽  
Vof Model

In the present work, a numerical investigation on the mechanism of heat transfer enhancement by a cavitation bubble collapsing near a heated wall has been presented. The Navier–Stokes equations and volume of fluid (VOF) model are employed to predict the flow state and capture the liquid-gas interface. The model was validated by comparing with the experimental data. The results show that the microjet violently impinges on the heated wall after the bubble collapses completely. In the meantime, the thickness of the thermal boundary layer and the wall temperature decrease significantly within the active scope of the microjet. The fresh low-temperature liquid and the impingement brought by the microjet should be responsible for the heat transfer reinforcement between the heated wall and the liquid. In addition, it is found that the impingement width of the microjet on the heated wall always keeps 20% of the bubble diameter. And, the enhancement degree of heat transfer significantly depends on such factors as stand-off distance, saturated vapor pressure, and initial bubble radius.

Numerical Investigation of Liquid Parameters Effect on the Oscillation of Cavitation Bubble

2014 ◽  
Vol 568-570 ◽  
pp. 1794-1800
Author(s):  
Xiu Mei Liu ◽  
Bei Bei Li ◽  
Wen Hua Li ◽  
Jie He ◽  
Jian Lu ◽  
...  
Keyword(s):  
Surface Tension ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Dynamic Performance ◽  
Bubble Radius ◽  
Gas Content ◽  
Viscous Force ◽  
Bubble Collapse ◽  
Hydraulic Systems ◽  
Increasing Temperature

Cavitation is a common harmful phenomenon in hydraulic transmission systems. It not only damages flow continuity and reduces medium physical performance, but also induces vibration and noise. At the same time, the efficiency of a system is reduced due to cavitation, especially dynamic performance are deteriorated. Applying commercial CFD software FLUENT, the cavitation issuing from the orifice was numerically investigated, reducing the harm. The effect of liquid parameters (such as surface tension, gas content, and the temperature) on the oscillation of bubble is studied numerically. The modified Rayleigh-Plesset equations are presented to describe the oscillation of bubble in different liquids. Employing the finite difference calculus, the behavior of a cavitation bubble in liquids with different physics parameters are obtained. Meanwhile, the numerical results are compared with experiment results. It is observed that the viscous force decreases the growth and collapse of a bubble, making it expand or collapse less violently. And the surface-tension forces stave bubble growth progress and speed up bubble collapse process. On the other hand, both the maximum bubble radius and bubble lifetime increase with increasing temperature. These results can provide theory basis for understanding cavitation bubble dynamics in the hydraulic systems.

scholarly journals An Approach to Studying Cavitation Bubble Collapse Pressure and Erosion.

1996 ◽  
Vol 62 (602) ◽  
pp. 2326-2332 ◽  
Author(s):  
Hiroyuki MORI ◽  
Shuji HATTORI ◽  
Tsunenori OKADA ◽  
Kazutoshi MIZUSHIMA
Keyword(s):  
Cavitation Bubble ◽  
Bubble Collapse ◽  
Collapse Pressure

scholarly journals Dynamics and acoustics of cavitation bubble in adverse external pressure gradient

2020 ◽  
Author(s):  
К.В. Рождественский
Keyword(s):  
Pressure Gradient ◽  
Cavitation Bubble ◽  
Acoustic Pressure ◽  
Bubble Radius ◽  
Pressure Rise ◽  
Leading Edge ◽  
External Pressure ◽  
Gas Content ◽  
Bubble Collapse ◽  
Spectral Parameters

В статье приводятся аналитические и численные результаты по динамике и акустике кавитационного пузырька при повышении внешнего давления. В начале рассматривается модельная задача о сжатии пузырька вплоть до коллапса при мгновенном повышении давления. При этом уравнение Рэлея-Плессета рассматривается с учетом газосодержания, поверхностного натяжения и вязкости. Акустическое давление, вызванное сжатием пузырька, записанное в безразмерном виде, определяется как с привлечением формул, так и численным путем. Показано, что если наряду с паром, внутри пузырька имеется некоторое количество газа, скорость его сжатия и акустическое давление оказываются конечными вплоть до полного схлопывания. Кроме того, возможно многократное повторение цикла расширения-сжатия с затуханием амплитуды колебаний. На каждом периоде колебаний вблизи момента времени коллапса (достижения минимального радиуса) наблюдается импульсное возрастание давления. Во второй части аналогичное исследование проводится для случая, когда кавитационный пузырек возникает в закругленной носовой части подводного крылового профиля. При этом демонстрируется зависимость динамического поведения пузырька и вызываемого им в заданной точке контура профиля акустического давления от типа профиля, его толщины и угла атаки. По периоду первого цикла схлопывания спектральные параметры акустического импульса определяются как у эквивалентного треугольного импульса. Presented in this paper are analytical and numerical results on dynamics and acoustics of a cavitation bubble in adverse external pressure gradient. First considered is a model problem of bubble collapse due to instantaneous increase of pressure. Therewith, the Rayleigh-Plesset equation is treated with account of gas content, surface tension and viscosity. Non-dimensional acoustic pressure caused by the compression of the bubble, is determined both with use of relevant formulae and numerically. It is shown that if together with vapor the bubble contains some quantity of gas, than its collapse rate and acoustic pressure during compression turn out to be finite. In addition, multiple expansion compression cycles are possible. For each period of bubble radius variation there occurs near the moment of collapse (moment of reaching a minimum radius) an impulse acoustic pressure rise. In the second part of the paper a similar investigation is carried out for the case when the bubble occurs near the rounded leading edge of a hydrofoil. Demonstrated therewith is the dependence of the bubble dynamic behavior and accompanying acoustic pressure pulses upon the foil type, thickness and angle of attack. Based on the period of the first bubble collapse cycle the spectral parameters of the induced acoustic pressure impulse are determined as for an equivalent triangular impulse.

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.

Numerical Study on Mass Transfer Effects on Spherical Cavitation Bubble Collapse in an Acoustic Field

2010 ◽  
Author(s):  
Ehsan Samiei ◽  
Mehrzad Shams ◽  
Reza Ebrahimi
Keyword(s):  
Mass Transfer ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Bubble Radius ◽  
Numerical Code ◽  
Bubble Collapse ◽  
Growth Time ◽  
Transfer Effects ◽  
Low Amplitude

A numerical code to simulate mass transfer effects on spherical cavitation bubble collapse in an acoustic pressure domain in quiescent water has been developed. Gilmore equation is used to simulate bubble dynamics, with considering mass diffusion and heat transfer. Bubbles with different initial radii were considered in quiescent infinite water in interaction with sinusoidal shock waves with different magnitudes of amplitude and frequency. Simulations were done in two cases; with and without considering mass transfer. Good agreement with reference data was achieved. For bubbles with small radii in high frequency pressure field with low amplitude, mass transfer causes larger maximum radii and growth time, and more violent resultant collapse. Decreasing pressure frequency or increasing its amplitude causes larger maximum radii, longer collapse time, and more violent collapse. But, in cases with mass transfer because at the last moments of collapse stage a large amount of water vapor is trapped inside the bubble, the collapse will become less violent. For larger bubbles collapse becomes more violent for the cases without mass transfer in all pressure amplitudes and higher frequencies. But decreasing pressure frequency makes the collapse of the bubbles with mass transfer more violent. However, mass transfer effects decreases with increasing initial bubble radius.

scholarly journals The concept of neutrality: a new approach

2019 ◽  
Vol 76 (1) ◽  
pp. 333-353 ◽  
Author(s):  
Stephen Macdonald ◽  
Briony Birdi
Keyword(s):  
Literature Review ◽  
Design Methodology ◽  
Information Science ◽  
Social Institutions ◽  
Future Research ◽  
Library And Information Science ◽  
New Approach ◽  
Content Type ◽  
Normative Framework ◽  
Contextual Awareness

Purpose Neutrality is a much debated value in library and information science (LIS). The “neutrality debate” is characterised by opinionated discussions in contrasting contexts. The purpose of this paper is to fill a gap in the literature by bringing these conceptions together holistically, with potential to deepen understanding of LIS neutrality. Design/methodology/approach First, a literature review identified conceptions of neutrality reported in the LIS literature. Second, seven phenomenographic interviews with LIS professionals were conducted across three professional sectors. To maximise variation, each sector comprised at least one interview with a professional of five or fewer years’ experience and one with ten or more years’ experience. Third, conceptions from the literature and interviews were compared for similarities and disparities. Findings In four conceptions, each were found in the literature and interviews. In the literature, these were labelled: “favourable”, “tacit value”, “social institutions” and “value-laden profession”, whilst in interviews they were labelled: “core value”, “subservient”, “ambivalent”, and “hidden values”. The study’s main finding notes the “ambivalent” conception in interviews is not captured by a largely polarised literature, which oversimplifies neutrality’s complexity. To accommodate this complexity, it is suggested that future research should look to reconcile perceptions from either side of the “neutral non-neutral divide” through an inclusive normative framework. Originality/value This study’s value lies in its descriptive methodology, which brings LIS neutrality together in a holistic framework. This framework brings a contextual awareness to LIS neutrality lacking in previous research. This awareness has the potential to change the tone of the LIS neutrality debate.

Development of insect repellent finish by a simple coacervation microencapsulation technique

2018 ◽  
Vol 30 (2) ◽  
pp. 152-158 ◽  
Author(s):  
Rachna Sharma ◽  
Alka Goel
Keyword(s):  
Essential Oils ◽  
Design Methodology ◽  
Insect Repellent ◽  
New Approach ◽  
Content Type ◽  
Eucalyptus Oil ◽  
Gum Acacia ◽  
Major Benefit ◽  
Natural Insecticide ◽  
Practical Implications

Purpose The paper focused onto the development of microcapsules by using two essential oils. It proposes the uses of eucalyptus oil and cedarwood oil as a natural insecticide. The purpose of this paper is to demonstrate the application of developed microcapsules to impart insect repellency on textile substrate. Design/methodology/approach The paper opted for an experimental study using two essential oils and gum in formations of microcapsules through a simple coaseravtion encapsulation technique. The developed solution was analyzed, including confirmation of size and structure through. Application of developed finish on substrate was also undertaken to prove better ability as repellent fabric. Findings The paper highlights useful invention of microencapsulated fabric developed with the combination of gum acacia and eucalyptus oil as core and shell material. The developed fabric has better ability to repel silverfish as compared to microencapsulated fabric developed with gum acacia (shell) and cedarwood oil (core). Research limitations/implications Due to the lack of time and less availability of essential oils, only two oils were used to test the insect repellent behavior. Practical implications This paper fulfills an identified need, it includes implications for the development of a very useful natural insecticide to repel silverfish (Lepisma saccharina) insect. This insect is a very common problem found in cloth wardrobes and bookshelves; it mainly attacks the fabric with cellulosic content and starch. Social implications Society will get major benefit of using these microencapsulated finished fabrics, which repel silverfish from their home and keep their clothing and books safe for longer period. The natural fragrance and medicinal benefits of these essential oils can never be ignored. Originality/value This study sets a new approach to repel insects like silverfish from the bookshelves and clothing wardrobes. A layer of insect repellent microencapsulated finished fabric can be added in these shelves and wardrobes. It is an eco-friendly approach of using natural essential oils instead of chemical insecticides.

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