Numerical Prediction of Impact Force in Cavitating Flows

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Hong Wang ◽  
Baoshan Zhu
Keyword(s):  
Numerical Method ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Impact Force ◽  
Quantitative Agreement ◽  
Bubble Collapse ◽  
Cavitating Flows ◽  
Cavitation Model ◽  
Model Based ◽  
The Impact

A numerical method including a macroscopic cavitation model based on the homogeneous flow theory and a microscopic cavitation model based on the bubble dynamics is proposed for the prediction of the impact force caused by cavitation bubble collapse in cavitating flows. A large eddy simulation solver, which is incorporated with a macroscopic cavitation model, is applied to simulate the unsteady cavitating flows. Based on the simulated flow field, the evolution of the cavitation bubbles is determined by a microscopic cavitation model from the resolution of a Rayleigh–Plesset equation including the effects of the surface tension, the viscosity and compressibility of fluid, the thermal conduction and radiation, the phase transition of water vapor at the interface, and the chemical reactions. The cavitation flow around a hydrofoil is simulated to validate the macroscopic cavitation model. A good quantitative agreement is obtained between the prediction and the experiment. The proposed numerical method is applied to predict the impact force at cavitation bubble collapse on a KT section in cavitating flows. It is found that the shock pressure caused by cavitation bubble collapse is very high. The impact force is predicted qualitatively compared with the experimental data.

Possibility of Quantitative Prediction of Cavitation Erosion Without Model Test

1996 ◽  
Vol 118 (3) ◽  
pp. 582-588 ◽  
Author(s):  
Hiroharu Kato ◽  
Akihisa Konno ◽  
Masatsugu Maeda ◽  
Hajime Yamaguchi
Keyword(s):  
Model Test ◽  
Cavitation Bubble ◽  
Cavitation Erosion ◽  
Impact Force ◽  
Quantitative Agreement ◽  
Main Flow ◽  
Quantitative Prediction ◽  
Bubble Collapse ◽  
The Impact ◽  
Cavitating Hydrofoil

A scenario for quantitative prediction of cavitation erosion was proposed. The key value is the impact force/pressure spectrum on a solid surface caused by cavitation bubble collapse. As the first step of prediction, the authors constructed the scenario from an estimation of the cavity generation rate to the prediction of impact force spectrum, including the estimations of collapsing cavity number and impact pressure. The prediction was compared with measurements of impact force spectra on a partially cavitating hydrofoil. A good quantitative agreement was obtained between the prediction and the experiment. However, the present method predicted a larger effect of main flow velocity than that observed. The present scenario is promising as a method of predicting erosion without using a model test.

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.

Investigation on cavitation bubble dynamics induced by clinically available Ho:YAG lasers

2016 ◽  
Vol 5 (2) ◽  
Author(s):  
Karl Stock ◽  
Daniel Steigenhöfer ◽  
Thomas Pongratz ◽  
Rainer Graser ◽  
Ronald Sroka
Keyword(s):  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Laser Energy ◽  
Bubble Collapse ◽  
High Contrast ◽  
Core Diameter ◽  
Ho:Yag Laser ◽  
Fiber Core ◽  
Set Up ◽  
Short Time

AbstractEndoscopic laser lithotripsy is the preferred technique for minimally invasive destruction of ureteral and kidney stones, and is mostly performed by pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser irradiation. The absorbed laser energy heats the water creating a vapor bubble which collapses after the laser pulse, thus producing a shock wave. Part of the laser energy strikes the stone through the vapor bubble and induces thermomechanical material removal. Aim of the present study was to visualize the behavior and the dynamics of the cavitation bubble using a specially developed ultra-short-time illumination system and then to determine important characteristics related to clinically used laser and application parameters for a more detailed investigation in the future.In accordance with Toepler’s Schlieren technique, in the ultra-short-time-illumination set-up the cavitation bubble which had been induced by Ho:YAG laser irradiation at the fiber end, was illuminated by two Q-switched lasers and the process was imaged in high contrast on a video camera. Cavitation bubbles were induced using different pulse energies (500 mJ/pulse and 2000 mJ/pulse) and fiber core diameters (230 μm and 600 μm) and the bubble dynamics were recorded at different times relative to the Ho:YAG laser pulse. The time-dependent development of the bubble formation was determined from the recordings by measuring the bubble diameter in horizontal and vertical directions, together with the volume and localization of the center of the bubble collapse.The results show that the bubble dynamics can be visualized and studied with both high contrast and high temporal resolution. The bubble volume increases with pulse energy and with fiber diameter. The bubble shape is almost round when a larger fiber core diameter is used, and elliptical when using a fiber of smaller core diameter. Moreover, the center of the resulting bubble is slightly further away from the fiber end and the center of the bubble collapse for a smaller fiber core diameter.The experimental set-up developed gives a better understanding of the bubble dynamics. The experiments indicate that the distance between fiber tip and target surface, as well as the laser parameters used have considerable impact on the cavitation bubble dynamics. Both the bubble dynamics and their influence on the stone fragmentation process require further investigation.

scholarly journals Cavitation and bubble dynamics: the Kelvin impulse and its applications

2015 ◽  
Vol 5 (5) ◽  
pp. 20150017 ◽  
Author(s):  
John R. Blake ◽  
David M. Leppinen ◽  
Qianxi Wang
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Bubble Dynamics ◽  
Clinical Medicine ◽  
Bubble Collapse ◽  
Rigid Boundary ◽  
Design Problems ◽  
Practical Applications ◽  
Wide Range ◽  
Naval Engineering

Cavitation and bubble dynamics have a wide range of practical applications in a range of disciplines, including hydraulic, mechanical and naval engineering, oil exploration, clinical medicine and sonochemistry. However, this paper focuses on how a fundamental concept, the Kelvin impulse, can provide practical insights into engineering and industrial design problems. The pathway is provided through physical insight, idealized experiments and enhancing the accuracy and interpretation of the computation. In 1966, Benjamin and Ellis made a number of important statements relating to the use of the Kelvin impulse in cavitation and bubble dynamics, one of these being ‘One should always reason in terms of the Kelvin impulse, not in terms of the fluid momentum…’. We revisit part of this paper, developing the Kelvin impulse from first principles, using it, not only as a check on advanced computations (for which it was first used!), but also to provide greater physical insights into cavitation bubble dynamics near boundaries (rigid, potential free surface, two-fluid interface, flexible surface and axisymmetric stagnation point flow) and to provide predictions on different types of bubble collapse behaviour, later compared against experiments. The paper concludes with two recent studies involving (i) the direction of the jet formation in a cavitation bubble close to a rigid boundary in the presence of high-intensity ultrasound propagated parallel to the surface and (ii) the study of a ‘paradigm bubble model’ for the collapse of a translating spherical bubble, sometimes leading to a constant velocity high-speed jet, known as the Longuet-Higgins jet.

scholarly journals Experimental Study on the Impact Characteristics of Cavitation Bubble Collapse on a Wall

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1262 ◽  
Author(s):  
Jing Luo ◽  
Weilin Xu ◽  
Jun Deng ◽  
Yanwei Zhai ◽  
Qi Zhang
Keyword(s):  
Impact Strength ◽  
Cavitation Bubble ◽  
Measuring System ◽  
Critical Conditions ◽  
Bubble Collapse ◽  
Main Concern ◽  
Wall Surface ◽  
Cavitation Bubbles ◽  
Impact Area ◽  
The Impact

As a hydrodynamic phenomenon, cavitation is a main concern in many industries such as water conservancy, the chemical industry and medical care. There are many studies on the generation, development and collapse of cavitation bubbles, but there are few studies on the variation of the cyclic impact strength on walls from the collapse of cavitation bubbles. In this paper, a high-speed dynamic acquisition and analysis system and a pressure measuring system are combined to study the impact of a cavitation bubble generated near a wall for various distances between the cavitation bubble and the wall. The results show that (1) with the discriminating criteria of the impact pressure borne by the wall, the critical conditions for the generation of a micro-jet in the collapse process of the cavitation bubbles are obtained, and therefore collapses of cavitation bubbles near the wall are mainly divided into primary impact area collapses, secondary impact area collapses and slow release area collapses; (2) it can be seen from the impact strength of the cavitation bubble collapse on the wall surface that the impact of cavitation bubbles on the wall surface during the first collapse decreases as γ (the dimensionless distance between the cavitation bubble and the wall) increases, but the impact of the second collapse on the wall surface increases first and then decreases sharply. When γ is less than 1.33, the impact on the wall surface is mainly from the first collapse. When γ is between 1.33 and 2.37, the impact on the wall surface is mainly from the second collapse. These conclusions have potential theoretical value for the utilization or prevention and control technologies for cavitation erosion.

A TRANSPORT EQUATION MODEL FOR SIMULATING CAVITATION FLOWS IN MINIATURE MACHINES

2010 ◽  
Vol 24 (13) ◽  
pp. 1467-1470 ◽  
Author(s):  
YAO ZHANG ◽  
XIANWU LUO ◽  
SHUHONG LIU ◽  
HONGYUAN XU
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Transport Equation ◽  
Bubble Growth ◽  
Cavitation Bubble ◽  
Equation Model ◽  
Cavitating Flow ◽  
Viscous Force ◽  
Cavitating Flows ◽  
Cavitation Model

A new transport equation model is proposed for simulating cavitating flows in miniature machines. In the developed model, the surface tension, viscous force, and thermal effect of cavitation are considered to reflect their influence on the cavitation bubble growth. The cavitating flow in a miniature pump is calculated by applying the proposed cavitation model. The comparison between numerical results and experimental data indicates that the new cavitation model is applicable for simulating the cavitating flow in miniature machines.

scholarly journals Energy Balance in Cavitation Erosion: From Bubble Collapse to Indentation of Material Surface

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
R. Fortes-Patella ◽  
G. Challier ◽  
J. L. Reboud ◽  
A. Archer
Keyword(s):  
Energy Balance ◽  
International Symposium ◽  
Wave Energy ◽  
Vapor Bubble ◽  
Pressure Wave ◽  
Cavitation Erosion ◽  
Bubble Dynamics ◽  
Bubble Collapse ◽  
Pressure Waves ◽  
Cavitating Flows

An original approach based on energy balance between vapor bubble collapse, emitted pressure wave, and neighboring solid wall response was proposed, developed, and tested to estimate the aggressiveness of cavitating flows. In the first part of the work, to improve a prediction method for cavitation erosion (Fortes-Patella and Reboud, 1998, “A New Approach to Evaluate the Cavitation Erosion Power,” ASME J. Fluids Eng., 120(2), pp. 335–344; Fortes-Patella and Reboud, 1998, “Energetical Approach and Impact Efficiency in Cavitation Erosion,” Proceedings of Third International Symposium on Cavitation, Grenoble, France), we were interested in studying the pressure waves emitted during bubble collapse. The radial dynamics of a spherical vapor/gas bubble in a compressible and viscous liquid was studied by means of Keller's and Fujikawa and Akamatsu's physical models (Prosperetti, 1994, “Bubbles Dynamics: Some Things we did not Know 10 Years Ago,” Bubble Dynamics and Interface Phenomena, Blake, Boulton-Stone, Thomas, eds., Kluwer Academic Publishers, Dordrecht, the Netherlands, pp. 3–15; Fujikawa and Akamatsu, 1980, “Effects of Non-Equilibrium Condensation of Vapor on the Pressure Wave Produced by Collapse of a Bubble in Liquid,” J. Fluid Mech., 97(3), pp. 481–512). The pressure amplitude, the profile, and the energy of the pressure waves emitted during cavity collapses were evaluated by numerical simulations. The model was validated by comparisons with experiments carried out at Laboratoire Laser, Plasma et Procédés Photoniques (LP3-IRPHE) (Marseille, France) with laser-induced bubble (Isselin et al., 1998, “Investigations of Material Damages Induced by an Isolated Vapor Bubble Created by Pulsed Laser,” Proceedings of Third International Symposium on Cavitation, Grenoble, France; Isselin et al., 1998, “On Laser Induced Single Bubble Near a Solid Boundary: Contribution to the Understanding of Erosion Phenomena,” J. Appl. Phys., 84(10), pp. 5766–5771). The efficiency of the first collapse ηwave/bubble (defined as the ratio between pressure wave energy and initial bubble potential energy) was evaluated for different bubble collapses. For the cases considered of collapse in a constant-pressure field, the study pointed out the strong influence of the air contents on the bubble dynamics, on the emitted pressure wave characteristics, and on the collapse efficiency. In the second part of the study, the dynamic response and the surface deformation (i.e., pit profile and pit volume) of various materials exposed to pressure wave impacts was simulated making use of a 2D axisymmetric numerical code simulating the interaction between pressure wave and an elastoplastic solid. Making use of numerical results, a new parameter β (defined as the ratio between the pressure wave energy and the generated pit volume) was introduced and evaluated for three materials (aluminum, copper, and stainless steel). By associating numerical simulations and experimental results concerning pitted samples exposed to cavitating flows (volume damage rate), the pressure wave power density and the flow aggressiveness potential power were introduced. These physical properties of the flow characterize the cavitation intensity and can be related to the flow hydrodynamic conditions. Associated to β and ηwave/bubble parameters, these power densities appeared to be useful tools to predict the cavitation erosion power.

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.

Modeling of Cavitation Bubble Dynamics in Multicomponent Mixtures

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Si Huang ◽  
A. A. Mohamad
Keyword(s):  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Current Model ◽  
Bubble Radius ◽  
Liquid Mixtures ◽  
Temporal Variations ◽  
Multicomponent Mixtures ◽  
First Order ◽  
Solid Liquid ◽  
The Impact

Investigation on cavitation in multicomponent (solid-liquid and liquid-liquid) mixtures has many applications in the industries and engineering. In this paper, for simulation of multicomponent mixtures, a set of equations with first-order bubble-wall Mach number is derived for a single spherical bubble in quasihomogeneous mixtures. Cavitation bubble behaviors in several kinds of liquid-liquid and solid-liquid mixtures are numerically calculated based on the current model, including the temporal variations in the bubble radius, pressure, and temperature inside the bubble. Specifically, the analysis is focused on the impact of pressure and temperature, while the bubble collapses in the mixtures. The computed results are compared with the previously reported experimental ones to demonstrate the validity of the current model and the numerical procedures.

Cavitation bubble dynamics in a liquid gap of variable height

2011 ◽  
Vol 682 ◽  
pp. 241-260 ◽  
Author(s):  
SILVESTRE ROBERTO GONZALEZ-AVILA ◽  
EVERT KLASEBOER ◽  
BOO CHEONG KHOO ◽  
CLAUS-DIETER OHL
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Strong Influence ◽  
Bubble Dynamics ◽  
Bubble Collapse ◽  
High Speed Photography ◽  
Expansion Time ◽  
Gap Height ◽  
Bubble Splitting ◽  
Narrow Gaps

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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