The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
A.-man Zhang - One of the best experts on this subject based on the ideXlab platform.
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SPH-BEM simulation of underwater explosion and bubble dynamics near Rigid Wall
Science China-technological Sciences, 2019Co-Authors: Zhifan Zhang, A.-man Zhang, Cheng Wang, Vadim V. Silberschmidt, Longkan WangAbstract:A process of underwater explosion of a charge near a Rigid Wall includes three main stages: charge detonation, bubble pulsation and jet formation. A smoothed particle hydrodynamics (SPH) method has natural advantages in solving problems with large deformations and is suitable for simulation of processes of charge detonation and jet formation. On the other hand, a boundary element method (BEM) is highly efficient for modelling of the bubble pulsation process. In this paper, a hybrid algorithm, fully utilizing advantages of both SPH and BEM, was applied to simulate the entire process of free and near-field underwater explosions. First, a numerical model of the free-field underwater explosion was developed, and the entire explosion process– from the charge detonation to the jet formation–was analysed. Second, the obtained numerical results were compared with the original experimental data in order to verify the validity of the presented method. Third, a SPH model of underwater explosion for a column charge near a Rigid Wall was developed to simulate the detonation process. The results for propagation of a shock wave are in good accordance with the physical observations. After that, the SPH results were employed as initial conditions for the BEM to simulate the bubble pulsation. The obtained numerical results show that the bubble expanded at first and then shrunk due to a differences of pressure levels inside and outside it. Here, a good agreement between the numerical and experimental results for the shapes, the maximum radius and the movement of the bubble proved the effectiveness of the developed numerical model. Finally, the BEM results for a stage when an initial jet was formed were used as initial conditions for the SPH method to simulate the process of jet formation and its impact on the Rigid Wall. The numerical results agreed well with the experimental data, verifying the feasibility and suitability of the hybrid algorithm. Besides, the results show that, due to the effect of the Bjerknes force, a jet with a high speed was formed that may cause local damage to underwater structures.
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experimental and numerical study on bubble sphere interaction near a Rigid Wall
Physics of Fluids, 2017Co-Authors: Shuai Li, A.-man ZhangAbstract:This study is concerned with the interaction between a violently oscillating bubble and a movable sphere with comparable size near a Rigid Wall, which is an essential physical phenomenon in many applications such as cavitation, underwater explosion, ultrasonic cleaning, and biomedical treatment. Experiments are performed in a cubic water tank, and the underwater electric discharge technique (580 V DC) is employed to generate a bubble that is initiated between a Rigid Wall and a sphere in an axisymmetric configuration. The bubble-sphere interactions are captured using a high-speed camera operating at 52 000 frames/s. A classification of the bubble-sphere interaction is proposed, i.e., “weak,” “intermediate,” and “strong” interactions, identified with three distinct bubble shapes at the maximum volume moment. In the numerical simulations, the boundary integral method and the auxiliary function method are combined to establish a full coupling model that decouples the mutual dependence between the force and t...
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numerical analysis of the bubble jet impact on a Rigid Wall
Applied Ocean Research, 2015Co-Authors: Shuai Li, Yunbo Li, A.-man ZhangAbstract:Abstract The main characteristic of the bubble dynamics near a Rigid Wall is the development of a high speed liquid jet, generating highly localized pressure on the Wall. In present study, the bubble dynamic behaviors and the pressure impulses are investigated through experimental and numerical methods. In the experiment, the dynamics of a spark-generated bubble near a steel plate are captured by a high-speed camera with up to 650,000 frames per second. Numerical studies are conducted using a boundary integral method with incompressible assumption, and the vortex ring model is introduced to handle the discontinued potential of the toroidal bubble. Meanwhile, the pressure on the Rigid Wall is calculated by an auxiliary function. Calculated results with two different stand-off parameters show excellent agreement with experimental observations. A double-peaked or multiple-peaked structure occurs in the pressure profile during the collapse and rebounding phase. Generally, the pressure at the Wall center reaches the first peak soon after the jet impact, and the second peak is caused by the rapid migration of the bubble toward the Wall, and the subsequent peaks may be caused by the splashing effect and the rebounding of the toroidal bubble. At last, both agreements and differences are found in the comparison between the present model and a hybrid incompressible–compressible method in Hsiao et al. (2014). The differences show that the compressibility of the flow is another influence factor of the jet impact. However, the main features of the jet impact could be simulated using the present model.
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Motion characteristics of cavitation bubble near the Rigid Wall with the driving of acoustic wave
China Ocean Engineering, 2015Co-Authors: Xi Ye, A.-man Zhang, Dong-rui ZengAbstract:The dynamics of cavitation bubble is analyzed in the compressible fluid by use of the boundary integral equation considering the compressibility. After the vertical incidence of plane wave to the Rigid Wall, the motion characteristics of single cavitation bubble near the Rigid Wall with initial equilibrium state are researched with different parameters. The results show that after the driving of acoustic wave, the cavitation bubble near the Rigid Wall will expand or contract, and generate the jet pointing to the Wall. Also, the existence of the Wall will elongate time for one oscillation. With the compressible model, the oscillation amplitude is reduced, as well as the peak value of inner pressure and jet tip velocity. The effect of the Wall on oscillation amplitude is limited. However with the increment of initial vertical distance, the effect of Wall on the jet velocity is from acceleration to limitation, and finally to acceleration again.
Longkan Wang - One of the best experts on this subject based on the ideXlab platform.
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SPH-BEM simulation of underwater explosion and bubble dynamics near Rigid Wall
Science China-technological Sciences, 2019Co-Authors: Zhifan Zhang, A.-man Zhang, Cheng Wang, Vadim V. Silberschmidt, Longkan WangAbstract:A process of underwater explosion of a charge near a Rigid Wall includes three main stages: charge detonation, bubble pulsation and jet formation. A smoothed particle hydrodynamics (SPH) method has natural advantages in solving problems with large deformations and is suitable for simulation of processes of charge detonation and jet formation. On the other hand, a boundary element method (BEM) is highly efficient for modelling of the bubble pulsation process. In this paper, a hybrid algorithm, fully utilizing advantages of both SPH and BEM, was applied to simulate the entire process of free and near-field underwater explosions. First, a numerical model of the free-field underwater explosion was developed, and the entire explosion process– from the charge detonation to the jet formation–was analysed. Second, the obtained numerical results were compared with the original experimental data in order to verify the validity of the presented method. Third, a SPH model of underwater explosion for a column charge near a Rigid Wall was developed to simulate the detonation process. The results for propagation of a shock wave are in good accordance with the physical observations. After that, the SPH results were employed as initial conditions for the BEM to simulate the bubble pulsation. The obtained numerical results show that the bubble expanded at first and then shrunk due to a differences of pressure levels inside and outside it. Here, a good agreement between the numerical and experimental results for the shapes, the maximum radius and the movement of the bubble proved the effectiveness of the developed numerical model. Finally, the BEM results for a stage when an initial jet was formed were used as initial conditions for the SPH method to simulate the process of jet formation and its impact on the Rigid Wall. The numerical results agreed well with the experimental data, verifying the feasibility and suitability of the hybrid algorithm. Besides, the results show that, due to the effect of the Bjerknes force, a jet with a high speed was formed that may cause local damage to underwater structures.
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dynamics of an underwater explosion bubble near a Rigid Wall effect of slenderness ratio installation and distance parameter
Journal of Coastal Research, 2017Co-Authors: Zhifan Zhang, Longkan Wang, Jicai LangAbstract:ABSTRACT Zhang, Z.; Wang, L.; Yao, X., and Lang, J., 2017. Dynamics of an underwater explosion bubble near a Rigid Wall: Effect of slenderness ratio, installation, and distance parameter. Structural damage of maritime construction (e.g., dams, warships, etc.) has received considerable international attention in recent years because of underwater explosions from accidental events and terrorist bombing attacks. Therefore, research studies on underwater explosion load characteristics will have a great influence on the future of coastal and maritime engineering. Here, level set–direct ghost fluid–Runge Kutta discontinuous Galerkin method and boundary element method are combined to establish a model of underwater explosion near a Rigid Wall. First, the hybrid algorithm is used to simulate the process of underwater explosion in free field; the results agree well with experimental data, proving the effectiveness of the algorithm. Second, the process of underwater explosion near a Rigid Wall is simulated by the p...
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pressure characteristics of bubble collapse near a Rigid Wall in compressible fluid
Applied Ocean Research, 2016Co-Authors: Longkan Wang, Zhifan Zhang, Shiping WangAbstract:Abstract High speed liquid jet and shockwave can be produced when a bubble collapses near a Rigid Wall, which may cause severe damage to solid structures. A hybrid algorithm was adopted to simulate bubble motion and associated pressures near a Wall combining Level Set-Modified Ghost Fluid-Discontinuous Galerkin (LS-MGF-DG) method and boundary element method (BEM). Numerical results were compared with experimental data to validate the presented algorithm. Jet formation was simulated by BEM and the induced pressure on the Wall was calculated with auxiliary function. The pressure at the point on the Wall where the jet points to reaches its peak value after the jet penetrates the bubble. Bubble collapse and rebounding were simulated by the LS-MGF-DG method. Shock-wave is induced when the bubble collapse toroidally to a minimum volume and the pressure at Wall center reaches the maximum due to shockwave superposition. A third pressure peak is found associated with the bubble rebounds and bubble splitting. In the case studied, a higher pressure was found due to collapse shockwave than bubble jet and affects a larger area of the Wall. In addition, the three pressure peaks due to jet impact, collapse impact as well as bubble rebounding and splitting decrease with the increase of the standoff distance.
Frederic Dias - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Wave Impact on a Rigid Wall Using a Two–phase Compressible SPH Method
Procedia IUTAM, 2020Co-Authors: Ashkan Rafiee, Denys Dutykh, Frederic DiasAbstract:Abstract In this paper, an SPH method based on the SPH–ALE formulation is used for modelling two-phase flows with large density ratios and realistic sound speeds. The SPH scheme is further improved to circumvent the tensile instability that may occur in the SPH simulations. The two-phase SPH solver is then used to model a benchmark problem of liquid impact on a Rigid Wall. The results are compared with an incompressible Level Set solver. Furthermore, a wave impact on a Rigid Wall with a large entrained air pocket is modelled. The SPH simulation is initialised by the output of a fully non-linear potential flow solver. The pressure distribution, velocity field and impact pressure are then analysed.
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numerical simulation of wave impact on a Rigid Wall using a two phase compressible sph method
Procedia IUTAM, 2015Co-Authors: Ashkan Rafiee, Denys Dutykh, Frederic DiasAbstract:Abstract In this paper, an SPH method based on the SPH–ALE formulation is used for modelling two-phase flows with large density ratios and realistic sound speeds. The SPH scheme is further improved to circumvent the tensile instability that may occur in the SPH simulations. The two-phase SPH solver is then used to model a benchmark problem of liquid impact on a Rigid Wall. The results are compared with an incompressible Level Set solver. Furthermore, a wave impact on a Rigid Wall with a large entrained air pocket is modelled. The SPH simulation is initialised by the output of a fully non-linear potential flow solver. The pressure distribution, velocity field and impact pressure are then analysed.
Shuai Li - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical study on bubble sphere interaction near a Rigid Wall
Physics of Fluids, 2017Co-Authors: Shuai Li, A.-man ZhangAbstract:This study is concerned with the interaction between a violently oscillating bubble and a movable sphere with comparable size near a Rigid Wall, which is an essential physical phenomenon in many applications such as cavitation, underwater explosion, ultrasonic cleaning, and biomedical treatment. Experiments are performed in a cubic water tank, and the underwater electric discharge technique (580 V DC) is employed to generate a bubble that is initiated between a Rigid Wall and a sphere in an axisymmetric configuration. The bubble-sphere interactions are captured using a high-speed camera operating at 52 000 frames/s. A classification of the bubble-sphere interaction is proposed, i.e., “weak,” “intermediate,” and “strong” interactions, identified with three distinct bubble shapes at the maximum volume moment. In the numerical simulations, the boundary integral method and the auxiliary function method are combined to establish a full coupling model that decouples the mutual dependence between the force and t...
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numerical analysis of the bubble jet impact on a Rigid Wall
Applied Ocean Research, 2015Co-Authors: Shuai Li, Yunbo Li, A.-man ZhangAbstract:Abstract The main characteristic of the bubble dynamics near a Rigid Wall is the development of a high speed liquid jet, generating highly localized pressure on the Wall. In present study, the bubble dynamic behaviors and the pressure impulses are investigated through experimental and numerical methods. In the experiment, the dynamics of a spark-generated bubble near a steel plate are captured by a high-speed camera with up to 650,000 frames per second. Numerical studies are conducted using a boundary integral method with incompressible assumption, and the vortex ring model is introduced to handle the discontinued potential of the toroidal bubble. Meanwhile, the pressure on the Rigid Wall is calculated by an auxiliary function. Calculated results with two different stand-off parameters show excellent agreement with experimental observations. A double-peaked or multiple-peaked structure occurs in the pressure profile during the collapse and rebounding phase. Generally, the pressure at the Wall center reaches the first peak soon after the jet impact, and the second peak is caused by the rapid migration of the bubble toward the Wall, and the subsequent peaks may be caused by the splashing effect and the rebounding of the toroidal bubble. At last, both agreements and differences are found in the comparison between the present model and a hybrid incompressible–compressible method in Hsiao et al. (2014). The differences show that the compressibility of the flow is another influence factor of the jet impact. However, the main features of the jet impact could be simulated using the present model.
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Bubble jet impact on a Rigid Wall of different stand-off parameters
IOP Conference Series: Materials Science and Engineering, 2015Co-Authors: Shuai Li, S P Wang, A M ZhangAbstract:One of the key features of the dynamics of a bubble near a Rigid Wall is the development of a high liquid jet, generating highly localized pressure on the Wall. In present study, the boundary integral method is employed to simulate this phenomenon, and the vortex ring model is introduced to handle the discontinued potential of the toroidal bubble. Meanwhile, the pressure induced in the whole process is calculated by an auxiliary function. The effect of the stand-off parameter on the bubble dynamics and the pressure on the Wall is investigated, and a double-peaked structure occurs in the pressure profile after the jet impact in some cases, which is associated with the jet impact and the high internal pressure inside the bubble.
Dachao Li - One of the best experts on this subject based on the ideXlab platform.
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A novel measurement method to investigate dynamics of single acoustic bubble near a Rigid Wall
2019 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2019Co-Authors: Hao Wu, Haixia Yu, Cheng Zhou, Zhihua Pu, Dachao LiAbstract:This paper proposes a non-invasive method to research on the dynamic behaviors of a micrometer scale air-bubble near a Rigid boundary in ultrasound field. As the rapid change and tiny size of the acoustic bubble near Rigid Wall, it is very hard to record the dynamic behaviors of acoustic bubbles, which is one of the key fundamental problems in the application of ultrasonic cavitation. In this paper, a new method combining microscope, high speed photography and synchronous technology is proposed to noninvasively and accurately record the dynamic behaviors of a single bubble in ultrasound field. By this method, a single air bubble in tiny size can be created in water whose inner composition is almost the same as acoustic cavitation bubbles, and the relative position of the generated bubble near Rigid Wall can be controlled. In the experiment, the temporal evolution of the bubble is recorded by the high-speed camera at 300,000 frames per second, as well as the corresponding data, such as volume of the bubble and the velocity of the farthermost point on the bubble from the Rigid boundary, is recorded. Results are demonstrated for a single bubble generated over a Rigid Wall under a certain standoff distance (1.85) in an ultrasound field with frequency of 20.47 kHz. The results show that the dynamics of a single bubble near the Rigid Wall in ultrasonic field can be divided into four parts: oscillation, movement, collapse and rebound. The maximum velocity of the bubble boundary, which is due to the formation of the high speed liquid jet, is around 11.3 m/s. Furthermore, the dynamic behaviors of a single bubble in the experiment of this paper have a good agreement with the corresponding numerical results.
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I2MTC - A novel measurement method to investigate dynamics of single acoustic bubble near a Rigid Wall
2019 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2019Co-Authors: Hao Wu, Haixia Yu, Cheng Zhou, Zhihua Pu, Jiaming Ma, Dachao LiAbstract:This paper proposes a non-invasive method to research on the dynamic behaviors of a micrometer scale air-bubble near a Rigid boundary in ultrasound field. As the rapid change and tiny size of the acoustic bubble near Rigid Wall, it is very hard to record the dynamic behaviors of acoustic bubbles, which is one of the key fundamental problems in the application of ultrasonic cavitation. In this paper, a new method combining microscope, high speed photography and synchronous technology is proposed to noninvasively and accurately record the dynamic behaviors of a single bubble in ultrasound field. By this method, a single air bubble in tiny size can be created in water whose inner composition is almost the same as acoustic cavitation bubbles, and the relative position of the generated bubble near Rigid Wall can be controlled. In the experiment, the temporal evolution of the bubble is recorded by the high-speed camera at 300,000 frames per second, as well as the corresponding data, such as volume of the bubble and the velocity of the farthermost point on the bubble from the Rigid boundary, is recorded. Results are demonstrated for a single bubble generated over a Rigid Wall under a certain standoff distance (1.85) in an ultrasound field with frequency of 20.47 kHz. The results show that the dynamics of a single bubble near the Rigid Wall in ultrasonic field can be divided into four parts: oscillation, movement, collapse and rebound. The maximum velocity of the bubble boundary, which is due to the formation of the high speed liquid jet, is around 11.3 m/s. Furthermore, the dynamic behaviors of a single bubble in the experiment of this paper have a good agreement with the corresponding numerical results.
