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.

Cinematographic Analysis of Counter Jet Formation in a Single Cavitation Bubble Collapse Flow

2011 ◽  
Vol 27 (2) ◽  
pp. 253-266 ◽  
Author(s):  
S.-H. Yang ◽  
S.-Y. Jaw ◽  
K.-C. Yeh
Keyword(s):  
Flow Field ◽  
Cavitation Bubble ◽  
Pressure Wave ◽  
Bubble Surface ◽  
Bubble Collapse ◽  
Solid Boundary ◽  
Liquid Jet ◽  
Pressure Waves ◽  
Field Variation ◽  
Critical Position

ABSTRACTThis study utilized a U-shape platform device to generate a single cavitation bubble for the detail analysis of the flow field characteristics and the cause of the counter jet during the process of bubble collapse induced by pressure wave. 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 the solid boundary. It is found that the Kelvin-Helmholtz vortices are formed when the liquid jet induced by the pressure wave penetrates the bubble surface. If the bubble center to the solid boundary is within one to three times the bubble's radius, a stagnation ring will form on the boundary when impacted by the penetrated jet. The liquid inside the stagnation ring is squeezed toward the center of the ring to form a counter jet after the bubble collapses. At the critical position, where the bubble center from the solid boundary is about three times the bubble's radius, the bubble collapse flows will vary. Depending on the strengths of the pressure waves applied, either just the Kelvin-Helmholtz vortices form around the penetrated jet or the penetrated jet impacts the boundary directly to generate the stagnation ring and the counter jet flow. This phenomenon used the particle image velocimetry method can be clearly revealed the flow field variation of the counter jet. If the bubble surface is in contact with the solid boundary, the liquid jet can only splash radially without producing the stagnation ring and the counter jet. The complex phenomenon of cavitation bubble collapse flows are clearly manifested in this study.

scholarly journals Influence of pulsive pressure waves on liquid penetration into wood in semi-opened container

2019 ◽  
Vol 65 (1) ◽  
Author(s):  
Soichi Tanaka ◽  
Masako Seki ◽  
Tsunehisa Miki ◽  
Kenji Umemura ◽  
Kozo Kanayama
Keyword(s):  
Wave Energy ◽  
Pressure Wave ◽  
Compressive Deformation ◽  
Hydraulic Pressure ◽  
Pressure Waves ◽  
Wood Block ◽  
Liquid Penetration ◽  
Water Penetration ◽  
Closed Container ◽  
Block Sample

Abstract The purpose of this paper was to confirm the influence of pulsive pressure waves on the liquid penetration into wood in the semi-opened container. Wood block sample was irradiated by the pulsive pressure waves in the semi-opened container filled with water used as a liquid. The irradiation was also performed in the closed container for the comparison. The water penetration into the sample was promoted by the pressure-wave irradiation. There was little difference in the degree of the penetration between the closed and the semi-opened containers. It was presumed from the measured hydraulic pressure that the pressure-wave energy irradiated on the sample in the closed container was higher than that in the semi-opened container. It was also presumed that the cavitation generation was promoted in the semi-opened container. This indicates that the cavitation as well as the pressure waves themselves affected the liquid penetration into wood. The compressive deformation of the sample irradiated in the semi-opened container was slightly smaller than that in the closed container. This indicates that the pulsive pressure-wave irradiation in the semi-opened container promoted the liquid penetration into wood with less compressive deformation.

Numerical Solution on Spherical Vacuum Bubble Collapse Using MPS Method

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Wen xi Tian ◽  
Sui-zheng Qiu ◽  
Guang-hui Su ◽  
Yuki Ishiwatari ◽  
Yoshiaki Oka
Keyword(s):  
Cavitation Erosion ◽  
Bubble Dynamics ◽  
Pressure Pulse ◽  
Bubble Diameter ◽  
Bubble Collapse ◽  
Interfacial Velocity ◽  
Bubble Liquid ◽  
Mps Method ◽  
Good Consistency ◽  
Moving Particle

Single vacuum bubble collapse in subcooled water has been simulated using the moving particle semi-implicit (MPS) method in the present study. The liquid is described using moving particles, and the bubble-liquid interface was set to be the vacuum pressure boundary without interfacial heat mass transfer. The topological shape of the vacuum bubble is determined according to the location of interfacial particles. The time dependent bubble diameter, interfacial velocity, and bubble collapse time were obtained within a wide parametric range. Comparison with Rayleigh’s prediction indicates a good consistency, which validates the applicability and accuracy of the MPS method. The potential void-induced water hammer pressure pulse was also evaluated, which is instructive for the cavitation erosion study. The present paper discovers fundamental characteristics of vacuum bubble hydrodynamics, and it is also instructive for further applications of the MPS method to complicated bubble dynamics.

Evaluation of Cavitation Erosion Intensity in a Microscale Nozzle Using Eulerian–Lagrangian Bubble Dynamic Simulation

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Masoud Khojasteh-Manesh ◽  
Miralam Mahdi
Keyword(s):  
Cavitation Erosion ◽  
Bubble Dynamics ◽  
Three Dimensional ◽  
Bubble Surface ◽  
Initial Position ◽  
Bubble Collapse ◽  
Lagrangian Analysis ◽  
Two Phase ◽  
The Impact ◽  
Erosion Intensity

In the present study, cavitation erosion is investigated by implementing an Eulerian–Lagrangian approach. Three-dimensional two-phase flow is simulated in a microscale nozzle using Reynolds-averaged Navier–Stokes (RANS) solver along with realizable k−ε turbulence model and Schnerr–Sauer cavitation model. The numerical results are in agreement with experimental observations. A modified form of Rayleigh–Plesset–Keller–Herring equation along with bubble motion equation is utilized to simulate bubble dynamics. Average values of mixture properties over bubble surface are used instead of bubble-center values in order to account for nonuniformities around the bubble. A one-way coupling method is used between Lagrangian analysis and RANS solution. The impact pressure resulted from bubble collapse is calculated for evaluation of erosion in diesel and soy methyl ester (SME) biodiesel in different situations. The results show that the initial size of the bubbles is an important factor for determining the intensity of erosion. So, the bubbles erosive power increases when their initial radius increases. It is also found that the intensity of erosion in diesel is much higher than that of biodiesel and this is because of the differences in fuels properties, especially in viscosity and vapor pressure. The effect of bubbles initial position on erosion intensity is also investigated in this study, and it is found that bubbles with the highest distance from sheet cavity termination have the highest contribution in erosion rate.

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.

A Vlasov equation for pressure wave propagation in bubbly fluids

2002 ◽  
Vol 454 ◽  
pp. 287-325 ◽  
Author(s):  
PETER SMEREKA
Keyword(s):  
Wave Propagation ◽  
Vlasov Equation ◽  
Pressure Wave ◽  
Bubble Dynamics ◽  
Type Equation ◽  
Nonlinear Effects ◽  
Single Bubble ◽  
Pressure Waves ◽  
General Description ◽  
Bubbly Fluids

The derivation of effective equations for pressure wave propagation in a bubbly fluid at very low void fractions is examined. A Vlasov-type equation is derived for the probability distribution of the bubbles in phase space instead of computing effective equations in terms of averaged quantities. This provides a more general description of the bubble mixture and contains previously derived effective equations as a special case. This Vlasov equation allows for the possibility that locally bubbles may oscillate with different phases or amplitudes or may have different sizes. The linearization of this equation recovers the dispersion relation derived by Carstensen & Foldy. The initial value problem is examined for both ideal bubbly flows and situations where the bubble dynamics have damping mechanisms. In the ideal case, it is found that the pressure waves will damp to zero whereas the bubbles continue to oscillate but with the oscillations becoming incoherent. This damping mechanism is similar to Landau damping in plasmas. Nonlinear effects are considered by using the Hamiltonian structure. It is proven that there is a damping mechanism due to the nonlinearity of single-bubble motion. The Vlasov equation is modified to include effects of liquid viscosity and heat transfer. It is shown that the pressure waves have two damping mechanisms, one from the effects of size distribution and the other from single-bubble damping effects. Consequently, the pressure waves can damp faster than bubble oscillations.

Propagation of Pressure Waves, Caused by a Thermal Shock, in Liquid Metals Containing Gas Bubbles

2005 ◽  
Author(s):  
K. Okita ◽  
Y. Matsumoto ◽  
S. Takagi
Keyword(s):  
Thermal Shock ◽  
Void Fraction ◽  
Pressure Wave ◽  
Cavitation Erosion ◽  
Liquid Metals ◽  
Bubble Radius ◽  
Gas Bubbles ◽  
Pressure Waves ◽  
Lower Natural Frequency ◽  
Small Bubbles

Propagation of pressure waves caused by a thermal shock in liquid metals containing gas bubbles is performed by a numerical simulation. The present study examined the influences of bubble radius and void fraction on the absorption of thermal expansion of liquid metals and attenuation of pressure waves. As the result of the calculation, since the large bubbles which have a lower natural frequency than the small bubbles cannot respond to the heat input, the peak pressure at the heated region increases with increasing bubble radius. Especially, when the bubble radii are around 500 μm, the pressure wave propagates through the mixture not with the sonic speed of the mixture but with that of liquid mercury. On the other hand, decreasing the void fraction makes behavior of bubbles nonlinear and a collapse of bubble produces a high pressure wave. However, the calculation shows that the method of introducing micro gas bubbles into liquid metals is effective to prevent cavitation erosion on the wall.

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