scholarly journals Investigation of Cavitation Bubble Dynamics Considering Pressure Fluctuation Induced by Slap Forces

Mathematics ◽  
2021 ◽  
Vol 9 (17) ◽  
pp. 2064
Author(s):  
Xiaoyu Wang ◽  
Shenghao Zhou ◽  
Zumeng Shan ◽  
Mingang Yin
Keyword(s):  
Pressure Fluctuation ◽  
Negative Pressure ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Shock Pressure ◽  
Standoff Distance ◽  
Vibration Velocity ◽  
Solid Boundary ◽  
Initial Radius ◽  
Bubble Evolution

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.

Modeling bubble evolution in air-oil mixture with a simplified method

2016 ◽  
Vol 230 (16) ◽  
pp. 2865-2871 ◽  
Author(s):  
Junjie Zhou ◽  
Jibin Hu ◽  
Shihua Yuan
Keyword(s):  
Mass Transfer ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Pressure Change ◽  
Isothermal Transformation ◽  
Adiabatic Process ◽  
Interphase Mass Transfer ◽  
Simplified Method ◽  
Bubble Evolution ◽  
Model C

This work addresses the problem of bubble evolution arising from gas cavitation in hydraulic oils. Two significant aspects, including the interphase mass transfer represented by air release and absorption phenomena and different thermodynamic considerations, are currently taken into account using a simplified method. In particular, three new models in progressive relationship are proposed on the basis of Rayleigh–Plesset equation which describes bubble dynamics. They are Model A in which air content is assumed to be constant, Model B in which the interphase mass transfer is introduced with the air undergoing an isothermal transformation, and Model C assuming an adiabatic process for the bubble evolution. With the goal of investigating the effects of these aspects, comparisons of the three models for two typical cases are presented with regard to the practical circumstances in which the oil pressure is set to increase linearly or oscillate sinusoidally. Results show a consistent trend for both cases concerning Model B and Model C compared to Model A. Although its speed relates to many factors, air release and absorption has a relevant impact on gas bubble radius. By the reason of adiabatic assumption, Model C provides a slower response regarding the oil pressure change. However, Model B and Model C may be both inaccurate if considering the actual interfacial heat transfer. In this viewpoint, the oil temperature in fluid power system could be affected.

scholarly journals Bubble Dynamics in a Two-Phase Bubbly Mixture

2010 ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Discharge Voltage ◽  
Large Bubble ◽  
Water Mixture ◽  
Two Phase ◽  
Mixture Density ◽  
Bubbly Medium

The dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is investigated experimentally and the results are provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of varying intensities. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the pressure imposed in the container. The size and concentration of the fine bubbles can be controlled by the electrolysis voltage, the length, diameter, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the bubble characteristic quantities such as maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and the mixture is observed using high speed video photography. The void fraction/density of the bubbly mixture in the fluid domain is measured as a function of time and space using image analysis of the high speed movies. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to simple compressible equations employed for spherical bubbles including a modified Gilmore Equation. Suggestions for improvement of the modeling are then presented.

Behavior of Inert Gas Bubbles in Forced Convective Liquid Metal Circuits

1976 ◽  
Vol 98 (1) ◽  
pp. 5-11 ◽  
Author(s):  
W. J. Minkowycz ◽  
D. M. France ◽  
R. M. Singer
Keyword(s):  
Liquid Metal ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Liquid Sodium ◽  
Gas Bubble ◽  
Flowing Liquid ◽  
Argon Gas ◽  
The Core

Conservation equations are derived for the motion of a small inert gas bubble in a large flowing liquid-gas solution subjected to large thermal gradients. Terms which are of the second order of magnitude under less severe and steady-state conditions are retained, thus resulting in an expanded form of the Rayleigh equation. The bubble dynamics is a function of opposing mechanisms tending to increase or decrease bubble volume while being transported with the solution. Diffusion of inert gas between the bubble and the solution is one of the most important of these mechanisms included in the analysis. The analytical model is applied to an argon gas bubble flowing in a weak solution of argon gas in liquid sodium. Calculations are performed for these fluids under conditions typical of normal and abnormal operation of a liquid metal fast breeder reactor (LMFBR) core and the resulting bubble radius, internal gas pressure, and mass of inert gas are presented in each case. An important result obtained indicates that inert gas bubbles reaching the core inlet of an LMFBR will always grow as they traverse the core under normal and extreme abnormal conditions and that the rate of growth is quite small in all cases.

On the boundary integral method for the rebounding bubble

2007 ◽  
Vol 570 ◽  
pp. 407-429 ◽  
Author(s):  
M. LEE ◽  
E. KLASEBOER ◽  
B. C. KHOO
Keyword(s):  
Energy Loss ◽  
Integral Method ◽  
Bubble Radius ◽  
Experimental Studies ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Bubble Collapse ◽  
Solid Boundary ◽  
Bubble System ◽  
Toroidal Bubble

The formation of a toroidal bubble towards the end of the bubble collapse stage in the neighbourhood of a solid boundary has been successfully studied using the boundary integral method. The further evolution (rebound) of the toroidal bubble is considered with the loss of system energy taken into account. The energy loss is incorporated into a mathematical model by a discontinuous jump in the potential energy at the minimum volume during the short collapse–rebound period accompanying wave emission. This implementation is first tested with the spherically oscillating bubble system using the theoretical Rayleigh–Plesset equation. Excellent agreement with experimental data for the bubble radius evolution up to three oscillation periods is obtained. Secondly, the incorporation of energy loss is tested with the motion of an oscillating bubble system in the neighbourhood of a rigid boundary, in an axisymmetric geometry, using a boundary integral method. Example calculations are presented to demonstrate the possibility of capturing the peculiar entity of a counterjet, which has been reported only in recent experimental studies.

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.

Impact of Tongue Shapes on Hydraulic and Structure Performances of Double-Channel Pump Based on Fluid-Structure Interaction

2015 ◽  
Author(s):  
Binjuan Zhao ◽  
Jing Qiu ◽  
Huilong Chen ◽  
Yu Wang ◽  
Youfei Zhao
Keyword(s):  
Stress Concentration ◽  
Pressure Fluctuation ◽  
Maximum Stress ◽  
Fluid Structure Interaction ◽  
Radial Force ◽  
Vibration Velocity ◽  
Maximum Displacement ◽  
Structure Interaction ◽  
Corner Radius ◽  
Double Channel

The volute tongue has a great influence on the rotational impeller and stationary volute interaction in a pump. In this paper, the impact of tongue shapes on hydraulic and structural performances of a double channel pump with a specific speed of 110.9 is investigated, and four cases with different tongue shapes are simulated by the two-way coupling fluid-structure interaction (FSI) method. The result shows that, in the hydraulic performance aspect, the influence of tongue shapes on the efficiency is weak, and the maximum different value is 0.76%. But the maximum different value of pump-head is 0.126m. Tongue shapes mainly affect the pressure fluctuation in and after the tongue edge in the rotational direction. Pressure fluctuation near the rectangle tongue is stronger than that near the rounded tongue, and an appropriate increase of the corner radius will decrease the pressure fluctuation effectively. Because of the asymmetry of the volute, radial force on the volute is very large. It is periodical when the impeller rotates one circle and decreases obviously with an appropriate increase of the corner radius. Compared to the rounded tongue, the radial force on the volute with rectangle tongue is larger. In structural performance aspect, stress concentration of the impeller appears on the suction surface near the outlet, and the volute stress concentration appears near the tongue edge. Tongue shapes have little effect on the stress distribution of the impeller, but affect the volute stress deeply. The maximum stress near the rectangle tongue is a little larger than that near the rounded tongue, but an appropriate increase of the corner radius will decrease the maximum stress of volute obviously, and the amplitude will decrease slightly. Displacement with the magnitude 10−5 m happens in the pump, and the maximum displacement point appears in the outlet of the volute. It is periodical and mainly influenced by the blade-passing frequency. The tongue shape has little impact on the maximum displacement, but it has an obvious effect on the vibration velocity of the pump. Compared to the volute with rectangle tongue, the rounded tongue can decrease the vibration velocity, and larger corner radius can also suppress the vibration.

scholarly journals Generation of negative pressure of underwater intensive acoustic pulse and cavitation bubble dynamics

2012 ◽  
Vol 61 (18) ◽  
pp. 184302
Author(s):  
Zhang Jun ◽  
Zeng Xin-Wu ◽  
Chen Dan ◽  
Zhang Zhen-Fu
Keyword(s):  
Negative Pressure ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Acoustic Pulse

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 and experimental study on dynamic characteristics of cavitation bubbles

2018 ◽  
Vol 70 (6) ◽  
pp. 1119-1126
Author(s):  
Feng Cheng ◽  
Weixi Ji
Keyword(s):  
Theoretical Model ◽  
Dynamic Characteristics ◽  
Water Pressure ◽  
Bubble Radius ◽  
Bubble Wall ◽  
Content Type ◽  
Cavitation Bubbles ◽  
Perturbation Frequency ◽  
Bubble Evolution ◽  
Evolution With Time

Purpose Cavitation bubbles cannot be avoided in the hydraulic system. Because of instability of flow and variation of water pressure, the jet often occurs in a bubble collapse. This study aims to accurately predict the shape, velocity and time of the resulting jet, so as to inhibit cavitation erosion. Design/methodology/approach In the study, a theoretical model of cavitation bubbles in the water has been developed by applying a periodic water film pressure into the Rayleigh–Plesset equation. A fourth-order in time Runge–Kutta scheme is used to obtain an accurate computation of the bubble dynamic characteristics. The behavior of the proposed theory is further simulated in a high-speed photography experiment by using a cavitation bubble test rig. The evolution with time of cavitation bubbles is further obtained. Findings A comparison with the available experimental results reveals that the bubble evolution with time has a duration of about 0.3T0, that well predicts the expanding and compressing process of cavitation bubbles. The results also show that the initial bubble radius in the water influences the moving velocity of the bubble wall, whereas the perturbation frequency of the water pressure has less effect on the velocity of the bubble wall. Originality/value A theoretical model well predicts dynamic characteristics of cavitation bubbles. The bubble evolution with time has a duration of about 0.3T0, Initial bubble radius influences the velocity of bubble wall. Perturbation frequency has less effect on the velocity of bubble wall.

Experimental and Numerical Investigation of Single Bubble Dynamics in a Two-Phase Bubbly Medium

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
Compressible Fluid ◽  
High Speed ◽  
Bubble Dynamics ◽  
Ambient Pressure ◽  
Bubble Radius ◽  
Homogeneous Medium ◽  
Two Phase ◽  
Fluid Medium ◽  
Bubbly Medium

The dynamics of a bubble in a dilute bubbly water-air mixture is investigated experimentally and the results compared with a simple homogeneous compressible fluid model in order to elucidate the requirements from a better advanced numerical solution. The experiments are conducted in view of providing input and validation for an advanced bubbly flow numerical model we are developing. Corrections for classical approaches where in the two-phase flow modeling the dynamics of individual bubble is based on spherical isolated bubble dynamics in the liquid or an equivalent homogeneous medium are sought. The main/primary bubble is produced by an underwater spark discharge from charged capacitors, while the bubbly medium is generated using electrolysis. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the ambient pressure in the container. The size and concentration of the fine bubbles is controlled by the electrolysis voltage, the length, diameter, arrangement, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the primary bubble characteristic quantities such as achieved maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and of the mixture is observed using high speed video photography. The void fraction of the bubbly mixture in the fluid domain is deduced from image analysis of the high speed movies and obtained as a function of time and space. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to a simple compressible fluid medium model which accounts for the change in the medium properties in space and time. This helps illustrate where such simple models are valid and where they need improvements. This information is valuable for the parallel development of an Eulerian-Lagrangian code, which accounts for the dynamics of bubbles in the field and their interaction.

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