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.

scholarly journals Numerical Simulation and Investigation of System Parameters of Sonochemical Process

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Sankar Chakma ◽  
Vijayanand S. Moholkar
Keyword(s):  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Gas Content ◽  
Small Radius ◽  
Dissolved Gas ◽  
High Vapor ◽  
Higher Temperature ◽  
Simulation Results ◽  
Main Effects

This paper presents the effects of various parameters that significantly affect the cavitation. In this study, three types of liquid mediums with different physicochemical properties were considered as the cavitation medium. The effects of various operating parameters such as temperature, pressure, initial bubble radius, dissolved gas content and so forth, were investigated in detail. The simulation results of cavitation bubble dynamics model showed a very interesting link among these parameters for production of oxidizing species. The formation of •OH radical and H2O2 is considered as the results of main effects of sonochemical process. Simulation results of radial motion of cavitation bubble dynamics revealed that bubble with small initial radius gives higher sonochemical effects. This is due to the bubble with small radius can undergo many acoustic cycles before reaching its critical radius when it collapses and produces higher temperature and pressure inside the bubble. On the other hand, due to the low surface tension and high vapor pressure, organic solvents are not suitable for sonochemical reactions.

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.

The Pressure Field Radiated by Cavitation Bubble in the Grinding Area of Power Ultrasonic Honing

2014 ◽  
Vol 1027 ◽  
pp. 44-47 ◽  
Author(s):  
Xi Jing Zhu ◽  
Ce Guo ◽  
Jian Qing Wang
Keyword(s):  
Radiation Pressure ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Pressure Field ◽  
Bubble Radius ◽  
Ultrasonic Frequency ◽  
Power Ultrasonic ◽  
Cutting Chatter ◽  
Grinding Mechanism ◽  
Order Of Magnitude

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.

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.

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.

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.

Dynamics and noise emission of vortex cavitation bubbles

2007 ◽  
Vol 575 ◽  
pp. 1-26 ◽  
Author(s):  
JAEHYUG CHOI ◽  
STEVEN L. CECCIO
Keyword(s):  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Static Pressure ◽  
Bubble Radius ◽  
Water Channel ◽  
Core Size ◽  
Noise Emission ◽  
Line Vortex ◽  
The Core ◽  
Cavitation Bubbles

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.

Voices of Distress: The Emotional Peril of Not Attaining a Dietetic Internship in Ontario

2013 ◽  
Vol 1 (3) ◽  
pp. 9
Author(s):  
Jennifer Lee Brady ◽  
Annie Hoang ◽  
Olivia Siswanto ◽  
Jordana Riesel ◽  
Jacqui Gingras
Keyword(s):  
Empirical Research ◽  
Current Model ◽  
Well Being ◽  
Structured Interview ◽  
Application Process ◽  
Dietetic Education ◽  
Dietetic Internship ◽  
The Impact ◽  
And Training ◽  
Future Growth

Obtaining dietetic licensure in Ontario requires completion of a Dietitians of Canada (DC) accredited four-year undergraduate degree in nutrition and an accredited post-graduate internship or combined Master’s degree program. Given the scarcity of internship positions in Ontario, each year approximately two-thirds of the eligible applicants who apply do not receive a position XX, XX, XX, XX, XX, XX, in press). Anecdotally, not securing an internship position is known to be a particularly disconcerting experience that has significant consequences for individuals’ personal, financial, and professional well-being. However, no known empirical research has yet explored students’ experiences of being unsuccessful in applying for internship positions. Fifteen individuals who applied between 2005 and 2009 to an Ontario-based dietetic internship program, but were unsuccessful at least once, participated in a one-on-one semi-structured interview. Findings reveal that participants’ experiences unfold successively in four phases that are characterized by increasingly heightened emotional peril: naïveté, competition, devastation, and frustration. The authors conclude that the current model of dietetic education and training in Ontario causes lasting distress to students and hinders the future growth and vitality of the dietetic profession. Further research is required to understand the impact of the current model on dietetic educators, internship coordinators, and preceptors as coincident participants in the internship application process.

Specifics of creating an effective system of project financing of innovation and investment activities of dairy subcomplex enterprises

2020 ◽  
Vol 26 (9) ◽  
pp. 1951-1969
Author(s):  
S.A. Chernikova
Keyword(s):  
Financial Stability ◽  
Current Model ◽  
Methodological Approach ◽  
Information Support ◽  
Competitive Advantages ◽  
Project Financing ◽  
Financing System ◽  
Management Of Innovation ◽  
Effective System ◽  
The Impact

Subject. The article considers the need to study the financing of investment and innovation processes and creating an effective system of project financing. Objectives. The purpose is to search for new opportunities to enhance the competitive advantages of enterprises of the dairy subcomplex, to ensure their financial stability and steady position in specialized agricultural food-product markets. Methods. The study draws on the theoretical and methodological approach to the impact of project management of innovation and investment activities on improving the efficiency of the project financing system and financial stability of enterprises operating in the dairy subcomplex. Results. The findings show that four levels can be distinguished in the formation and improvement of the system of project financing and the management of innovation and investment activities, depending on the depth of transformation. The principle that provides the integration of the said system with the current model of management of the dairy subcomplex enterprise is defined as a driver. The paper offers a number of levels of the system transformation to gain competitive advantages. Conclusions. I present a mechanism for creating and improving the system of project financing and the management of innovation and investment activities, and a mechanism for interaction of the network of automated information systems, intended to make management decisions, with the automation of information support to innovative solutions.

scholarly journals Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 213
Author(s):  
Hamid Ait Said ◽  
Hassan Noukrati ◽  
Hicham Ben Youcef ◽  
Ayoub Bayoussef ◽  
Hassane Oudadesse ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Compressive Strength ◽  
Mechanical Strength ◽  
Bone Repair ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Composite Effect ◽  
Solid Liquid ◽  
The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

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