Mechanism Of Bubble Breakup Research Articles

CFD analysis of the intensification mechanism of bubble breakup by perforated plates in a bubble column

CFD analysis of the intensification mechanism of bubble breakup by perforated plates in a bubble column

Modeling bubble dynamics in rotating foam stirrer reactors: A computational fluid dynamics approach incorporating gas–solid interactions

Abstract The rotating foam stirrer reactor (RFSR) employs a donut‐shaped porous solid foam stirrer to enhance mass transfer in multiphase systems. However, the complex structure of the foam stirrer presents significant challenges for developing efficient computational models, impeding reactor optimization and scale‐up. In this work, we developed a novel bubble breakup and coalescence model based on Liao's framework, incorporating the effects of the rotating porous media. A new bubble breakup mechanism was proposed, accounting for the friction and collisions between bubbles and the struts within the foam stirrer. By integrating this model with a porous media approach, we constructed a simplified three‐dimensional computational fluid dynamics model of the RFSR. Simulation results reveal that bubble breakup within the porous medium is primarily driven by gas–solid interactions, leading to enhanced mass transfer. The model accurately predicts gas holdup and bubble size distributions, providing valuable insights for reactor design and scale‐up.

Experimental study of bubble breakup in water and solid suspension by using the image‐based method

Abstract This work investigates the bubble breakup process with and without particles in turbulent conditions using the image‐based method. A binocular high‐speed camera was employed to capture breakup events. A deep learning‐based image identification software (Large Deformation Dispersed Phase Analysis in Multiphase Flows) and a highly deformed bubble volume/surface area quantification method (Dense Adaptive Segmentation Method) are proposed. An energy barrier is found during the bubble breakup process, with the maximum increase in surface area (ΔSmax) being two to three times the final increase after breakup (ΔSfinal). This indicates that the critical energy required for bubble breakup is underestimated in most breakup models. The presence of suspended particles raises this energy barrier, thus reducing the breakup probability. The daughter bubble size distribution follows an M‐type distribution in water, while the addition of particles leads to a tendency towards equal‐size breakup. This work provides a reliable technology and the experimental data for further clarifying the bubble breakup mechanism.

Numerical simulation study of bubble breakup mechanism in microchannels with V-shaped obstacle

Numerical simulation study of bubble breakup mechanism in microchannels with V-shaped obstacle

Experimental and numerical research on the coupled mechanisms of cavitation effect in a Venturi-type bubble generator

Experimental and numerical research on the coupled mechanisms of cavitation effect in a Venturi-type bubble generator

Effect of stirring speed and temperature on the microstructure and mechanical properties of A356 alloy under vacuum

Effect of stirring speed and temperature on the microstructure and mechanical properties of A356 alloy under vacuum

Evaluation and dynamic breakup of bubble size distribution of liquified natural gas release underwater

Evaluation and dynamic breakup of bubble size distribution of liquified natural gas release underwater

Numerical investigation on the coupled mechanisms of bubble breakup in a venturi-type bubble generator

ABSTRACT The bubble breakup mechanism in a venturi-type bubble generator is a hot research topic, and the bubble breakup mechanisms induced by the axial regional flow field characteristics has long been studied and debated. A coupled volume of fluid and large eddy simulation numerical simulation method was conducted within the OpenFOAM® framework to track the two-phase interfaces and transient turbulence characteristics of the flow field in a venturi-type bubble generator. A turbulence inlet database was established to ensure the reliability of the numerical solution and the economy of the calculation. The results indicated that the bubble breakup induced by the axial regional flow field characteristics of the divergent section can be divided into a steady-state disturbed breakup pattern and an unsteady-state disturbed breakup pattern macroscopically, the latter playing a dominant role in generating fine bubbles. Furthermore, a series of typical bubble breakup processes were captured via a Lagrangian approach that showed that interfacial instability played an important role at each stage of bubble transport: Kelvin–Helmholtz instability caused bubbles to detach from the gas film during the steady-state disturbed breakup pattern, and Rayleigh–Taylor instability induced the deformation of detached bubbles in the unsteady-state disturbed region. Additionally, viscous shear force strengthened the interfacial instability in the binary breakup process, and turbulent fluctuations and collisions contributed to the shattering of defective bubbles. Moreover, a shearing-off process tended to occur in regions with small vorticity fluctuations, therefore playing a small role in creating large clusters of bubbles.

Monodispersed microbubble production using modified micro-Venturi bubble generator

This paper presents an innovative method to produce controlled monodispersed bubbles using a modified micro-Venturi channel. The influence of flow control parameters such as liquid pressure and gas flow rate on the controlled generation of micro-bubbles was investigated. Experiments were conducted in a transparent modified micro-Venturi channel, having a depth of 40 μm, in which monodispersed gas bubbles were generated. The proposed design provides a new configuration to produce monodispersed microbubbles. Image analysis focused at the vena-contracta region showed that the geometry of generated microbubbles change suddenly from an ellipsoidal shape to a circular shape having a constant diameter. The dynamics of the bubble breakup mechanism in a modified micro-Venturi channel has been described. It was observed that the velocity and the size of the micro-bubbles were strongly dependent on the flow control parameters. The bubble frequency was linearly increasing with respect to gas mass flow rates.

Deformation of gas-liquid interfaces in a non-Newtonian fluid at high throughputs inside a microfluidic device and effect of an expansion on bubble breakup mechanisms

Deformation of gas-liquid interfaces in a non-Newtonian fluid at high throughputs inside a microfluidic device and effect of an expansion on bubble breakup mechanisms

A review on bubble generation and transportation in Venturi-type bubble generators

Venturi-type bubble generators own advantages of simplicity in structure, high efficiency, low power consumption, and high reliability, exhibiting a broad application potential in various fields. This work presents a literature review of recent progress in the research concerning Venturi-type bubble generators, with a focus on the performance evaluation, bubble transportation, and breakup mechanisms. Experimental studies employing flow visualization techniques have played an important role in exploring the bubble transportation and breakup phenomena, which is vitally necessary for clarifying the bubble breakup mechanisms and understanding the working principle and performance of a Venturi channel as a bubble generator. A summarization was carried out on both experimental and theoretical work concerning parameters influencing the bubble breakup and the performance of Venturi-type bubble generators. Based on the geometric parameter optimization combined with appropriate flow conditions, it is expected that Venturi-type bubble generators can produce bubbles with controllable size and concentration to satisfy the application requirements, while a further work is required to illustrate the interaction between the liquid and gas bubbles.

Numerical Study of Bubble Breakup in Fractal Tree-Shaped Microchannels.

Hydrodynamic behaviors of bubble stream flow in fractal tree-shaped microchannels is investigated numerically based on a two-dimensional volume of fluid (VOF) method. Bubble breakup is examined in each level of bifurcation and the transition of breakup regimes is discussed in particular. The pressure variations at the center of different levels of bifurcations are analyzed in an effort to gain further insight into the underlying mechanism of bubble breakup affected by multi-levels of bifurcations in tree-shaped microchannel. The results indicate that due to the structure of the fractal tree-shaped microchannel, both lengths of bubbles and local capillary numbers decrease along the microchannel under a constant inlet capillary number. Hence the transition from the obstructed breakup and obstructed-tunnel combined breakup to coalescence breakup is observed when the bubbles are flowing into a higher level of bifurcations. Compared with the breakup of the bubbles in the higher level of bifurcations, the behaviors of bubbles show stronger periodicity in the lower level of bifurcations. Perturbations grow and magnify along the flow direction and the flow field becomes more chaotic at higher level of bifurcations. Besides, the feedback from the unequal downstream pressure to the upstream lower level of bifurcations affects the bubble breakup and enhances the upstream asymmetrical behaviors.

Experimental studies on bubble breakup mechanism in a venturi bubble generator

Experimental studies on bubble breakup mechanism in a venturi bubble generator

Characteristics and mechanism of bubble breakup in a bubble generator developed for a small TMSR

Characteristics and mechanism of bubble breakup in a bubble generator developed for a small TMSR

Dynamic characteristics of ventilated bubble moving in micro scale venturi

Dynamic characteristics of ventilated bubble moving in micro scale venturi

Numerical Simulation of Bubble Formation and Transport in Cross-Flowing Streams

Numerical simulations on confined bubble trains formed by cross-flowing streams are carried out with the numerical code THETIS which is based on the Volume of Fluid (VOF) method and has been developed for two phase flow studies and especially for a gas-liquid system. The surface tension force, which needs particular attention in order to determine the shape of the interface accurately, is computed using the Continuum Surface Force model (CSF). Through the coupling of a VOF-PLIC technique (Piecewise-Linear Interface Calculation) and a smoothing function of adjustable thickness, the Smooth Volume of Fluid technique (SVOF) is intended to capture accurately strong interface distortion, rupture or reconnection with large density and viscosity contrasts between phases. This approach is extended by using the regular VOF-PLIC technique, while applying a smoothing procedure affecting both physical characteristics averaging and surface tension modeling. The front-capturing strategy is extended to gas injection. We begin by introducing the main physical phenomena occurring during bubble formation in microfluidic systems. Then, an experimental study performed in a cylindrical T-junction for different wetting behaviors is presented. For the wetting configuration, Cartesian 2D numerical simulations concerning the gas-liquid bubble production performed in a T-junction with rectangular, planar cross sections are shown and compared with experimental measurements. Finally, the results obtained of bubble break-up mechanism, shape, transport and pressure drop along the channel will be presented, discussed and compared to some experimental and numerical outcomes given in the literature.

Three‐Dimensional Simulation of Bubble Formation Through a Microchannel T‐Junction

Abstract Three‐dimensional simulations of bubble formation in Newtonian and non‐Newtonian fluids through a microchannel T‐junction are conducted by the volume‐of‐fluid method. For Newtonian fluids, the critical capillary number Ca for the transition of the bubble breakup mechanism is dependent on the velocity ratio between the two phases and the microchannel dimension. For the power law fluid, the bubble diameter decreases and the generation frequency increases with higher viscosity parameter K and power law index n. For a Bingham fluid, the viscous force plays a more important role in microbubble formation. Due to the yield stress τy, a high‐viscous region is developed in the central area of the channel and bubbles deform to a flat ellipsoid shape in this region. The bubble diameter and generation frequency are almost independent of K.

Breakup of finite thickness viscous shell microbubbles by ultrasound: A simplified zero-thickness shell model

A simplified three-dimensional (3-D) zero-thickness shell model was developed to recover the non-spherical response of thick-shelled encapsulated microbubbles subjected to ultrasound excitation. The model was validated by comparison with previously developed models and was then used to study the mechanism of bubble break-up during non-spherical deformations resulting from the presence of a nearby rigid boundary. The effects of the shell thickness and the bubble standoff distance from the solid wall on the bubble break-up were studied parametrically for a fixed insonification frequency and amplitude. A diagram of bubble shapes versus the normalized shell thickness and wall standoff was derived, and the potential bubble shapes at break-up from reentrant jets were categorized resulting in four distinct zones.

Experimental Study on Air Entrainment in Slot Die Coating of High-Viscosity, Shear-Thinning Fluids

Experimental Study on Air Entrainment in Slot Die Coating of High-Viscosity, Shear-Thinning Fluids

Breakup dynamics of slender bubbles in non‐newtonian fluids in microfluidic flow‐focusing devices

Abstract This study aims to investigate the breakup of slender bubbles in non‐Newtonian fluids in microfluidic flow‐focusing devices using a high‐speed camera and a microparticle image velocimetry (micro‐PIV) system. Experiments were conducted in 400‐ and 600‐μm square microchannels. The variation of the minimum width of gaseous thread with the remaining time before pinch‐off could be scaled as a power‐law relationship with an exponent less than 1/3, obtained for the pinch‐off of bubbles in Newtonian fluids. The velocity field and spatial viscosity distribution in the liquid phase around the gaseous thread were determined by micro‐PIV to understand the bubble breakup mechanism. A scaling law was proposed to describe the size of bubbles generated in these non‐Newtonian fluids at microscale. The results revealed that the rheological properties of the continuous phase affect significantly the bubble breakup in such microdevices. © 2012 American Institute of Chemical Engineers AIChE J,, 2012