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The study of bubble growth and collapse is of great significance in the context of sustainability due to its influence on numerous energy-related processes and technologies. Understanding the dynamics of bubble behavior is vital for optimising heat transfer efficiency, which has an energetic role in improving the performance of sustainable systems such as nuclear reactors, thermal inkjet printing, and nucleate boiling. Indeed, researchers can progress strategies to enhance the efficiency of these technologies by analysing the parameters influencing bubble growth and collapse, which can lead to reduced energy consumption and environmental impact. Although several theoretical models and experimental investigations have been achieved in the past to inspect bubble growth and collapse, a thorough review and critical assessment of the studies conducted have not yet been achieved. This review aims to provide a comprehensive understanding of the relationship between bubble dynamics and sustainability, highlighting the potential for further research and development in this area. Specifically, the scope and limitations of past research on bubble growth and collapse is conducted to fill this gap in the open literature. The review covers both numerical and experimental studies of bubble growth and collapse in a wide set of innovative industrial applications including nuclear reactors, thermal inkjet printing, nucleate boiling, hydrodynamic erosion, and ultrasonic and medicinal therapy. The current review also attempts to illustrate and evaluate the numerical methods used and underlines the most relevant results from the studies that were looked at in order to provide researchers with a clear picture of the growth and collapse of bubbles in different applications. The results give a precise understanding of the dynamics of bubble growth and collapse and the related temperature change and cumulative heat transmission from the thermal boundary layer. Additionally, it has been demonstrated that simulation-based models can effectively predict transport coefficients. However, the review observes a number of limitations of the past research on bubble growth and collapse. Due to numerical instability, very little work with respect to dynamic modelling has been carried out on the mechanisms of bubble collapse. Accordingly, a number of recommendations are made for the improvement of heat transmission during bubble growth and collapse. Specifically, future criteria for the highest heat transmission will demand more precise experimental and numerical approaches. [ABSTRACT FROM AUTHOR]

The formation of oxygen bubbles in the anodic circuit of a polymer electrolyte membrane (PEM) electrolyser is a major technological problem as it greatly affects heat transfer, process performance and safety. Overall, bubbles evolve in the pipe flow upstream of the gas separator due to oxygen super-saturation created by the chemical reaction at the anode. The accurate prediction of bubble formation in the pipes is important for the correct positioning and design of the gas separator. This paper therefore presents a cell-based one-dimensional numerical model that estimates bubble evolution in a horizontal pipe-flow. For this purpose, the model considers bubble growth at nucleation sites and in the flow, enabling the prediction of the corresponding gas fraction at different locations within the cooling circuit. Furthermore, a sensitivity analysis was conducted based on the derived model to evaluate the impact of various parameters on the degassing rate. It was found that the smaller the pipe diameter, the greater the initial gas content and the greater the number of nucleation sites, the shorter the pipe length required to achieve solubility. • Bubbles evolve in the cooling circuit of PEM-electrolysis due to super-saturation. • A cell-based 1D numerical model predicts the gas fraction at various locations. • A sensitivity analysis shows the impact of various parameters on the degassing. • Degassing is improved by smaller pipe diameters and a higher initial gas fraction. • The higher the number of nucleation sites, the better the degassing. [ABSTRACT FROM AUTHOR]

Improving the scalability of tissue imaging throughput with bright, coherent X-rays requires identifying and mitigating artifacts resulting from the interactions between X-rays and matter. At synchrotron sources, long-term imaging of soft tissues in solution can result in gas bubble formation or cavitation, which dramatically compromises image quality and integrity of the samples. By combining in-line phase-contrast imaging with gas chromatography in real time, we were able to track the onset and evolution of high-energy X-ray-induced gas bubbles in ethanol-embedded soft tissue samples for tens of minutes (two to three times the typical scan times). We demonstrate quantitatively that vacuum degassing of the sample during preparation can significantly delay bubble formation, offering up to a twofold improvement in dose tolerance, depending on the tissue type. However, once nucleated, bubble growth is faster in degassed than undegassed samples, indicating their distinct metastable states at bubble onset. Gas chromatography analysis shows increased solvent vaporization concurrent with bubble formation, yet the quantities of dissolved gasses remain unchanged. By coupling features extracted from the radiographs with computational analysis of bubble characteristics, we uncover dose-controlled kinetics and nucleation site-specific growth. These hallmark signatures provide quantitative constraints on the driving mechanisms of bubble formation and growth. Overall, the observations highlight bubble formation as a critical yet often overlooked hurdle in upscaling X-ray imaging for biological tissues and soft materials and we offer an empirical foundation for their understanding and imaging protocol optimization. More importantly, our approaches establish a top-down scheme to decipher the complex, multiscale radiation–matter interactions in these applications.

Improving the scalability of tissue imaging throughput with bright, coherent X-rays requires identifying and mitigating artifacts resulting from the interactions between X-rays and matter. At synchrotron sources, long-term imaging of soft tissues in solution can result in gas bubble formation or cavitation, which dramatically compromises image quality and integrity of the samples. By combining in-line phase-contrast imaging with gas chromatography in real time, we were able to track the onset and evolution of high-energy X-ray-induced gas bubbles in ethanol-embedded soft tissue samples for tens of minutes (two to three times the typical scan times). We demonstrate quantitatively that vacuum degassing of the sample during preparation can significantly delay bubble formation, offering up to a twofold improvement in dose tolerance, depending on the tissue type. However, once nucleated, bubble growth is faster in degassed than undegassed samples, indicating their distinct metastable states at bubble onset. Gas chromatography analysis shows increased solvent vaporization concurrent with bubble formation, yet the quantities of dissolved gasses remain unchanged. By coupling features extracted from the radiographs with computational analysis of bubble characteristics, we uncover dose-controlled kinetics and nucleation site-specific growth. These hallmark signatures provide quantitative constraints on the driving mechanisms of bubble formation and growth. Overall, the observations highlight bubble formation as a critical yet often overlooked hurdle in upscaling X-ray imaging for biological tissues and soft materials and we offer an empirical foundation for their understanding and imaging protocol optimization. More importantly, our approaches establish a top-down scheme to decipher the complex, multiscale radiation-matter interactions in these applications. [ABSTRACT FROM AUTHOR]

A detailed study at the microscopic level of the transient behavior of boiling phenomena during quenching of an AISI 304 stainless steel, conical-end, cylindrical probe in flowing water at 60 °C was conducted using high-speed video recordings and cooling curve data acquisition. Two free-stream velocities (0.2 and 0.6 m/s) and two initial probe temperatures (850 and 950 °C) were investigated. It was complemented by video recordings at 60 fps to calculate the wetting front velocity. Surface heat flux histories at the thermocouple positions were estimated by solving the corresponding Inverse Heat Conduction Problem. As the water velocity increases the duration of the vapor film at each thermocouple position shortens and the difference among cooling curves at the thermocouple positions decreases. Increasing the initial temperature increases the duration of the vapor film stage. The wetting front velocity increased from 4 to 6 m/s. The time to reach the maximum surface heat flux at the position of the thermocouple closest to the probe tip ranged from 9.7 to 18 s. Undulations at the vapor-liquid interface that appear periodically and propagate in the direction of quenchant flow were observed early during the vapor film stage. Later, before the collapse of the vapor film, a kind of a shock wave was generated at the probe tip which modified the appearance of the film. Once the Leidenfrost temperature is reached, a wetting front (which consists of many small bubbles that coalesce rapidly in a very small area) is formed and travels in the direction of quenchant flow while fewer and larger bubbles nucleate and grow upstream. The nucleation, growth and detachment of the larger bubbles was studied; as the free-stream velocity decreases larger values of bubble maximum diameter and half-life time were observed, while the initial temperature has a marginal effect on these quantities. [ABSTRACT FROM AUTHOR]

Methane and other gases released from soft sediments are among the main sources of greenhouse gases in the atmosphere. In this paper, a growth model for isolated bubbles in the sediments was established based on the theory of linear elastic fracture mechanics. Water level drop experiments were conducted using magnesium lithium philip silicate transparent soils, and the changes in bubble pressure and morphology during water level drop were analyzed. The experimental results show that there is a critical pressure for bubble growth caused by a drop in water level. Bubbles only start to grow by fracturing the overlying sediments when the water level drops to the critical value because the critical bubble pressure is lower than the actual bubble pressure. The strength of soil, depth of the bubble position, longitudinal length of bubble, and amount and rate of water level drop are key factors affecting isolated bubble growth. Bubbles in the soils with higher strength are more difficult to reach the critical state but have a faster growth rate once they do reach it. The depth of bubble position only affects the time reaching the critical state and does not impact the post-growth process. Deeper bubbles are more difficult for initiating growth. For bubbles at the same depth, larger bubbles begin growing earlier. As bubbles become larger, the growth rate of the bubble increases progressively faster. Faster water level drops result in shorter times to reach their critical state and accelerate their growth rate. [ABSTRACT FROM AUTHOR]

Condition monitoring and maintenance are essential for ensuring stable and reliable operation of facility transformer, reducing costs, and increasing expected life. Foam cannot be avoided within the power transformer which illustrates at least one of the principal roots of insulation deterioration. Due to the intricacy of the dynamics within the insulation system, involving bubble creation, migration, and accumulation, challenges arise in understanding these mechanisms. Consequently, the problems caused by bubble dynamics require further investigation. This paper provides a scientific review of issues related to bubble formation, migration, and dispersion and their electrical effects on power transformers. Various descriptions are given to high-light impact of the dynamics of the bubble within high voltage insulation fields, which covers bubble generation mechanism, and therefore, the quintessential influencing factors, state-of-the-art advances in multi-physics coupled modeling of bubble dynamics, etc. Moreover, pending issues on bubble control and mitigation are addressed, as well as recommendations for future investigations. Nonetheless, this paper contains a useful quotation guide for researchers within an equivalent field of research, which can motivate readers to explore scientific solutions to prevailing bottleneck problems.

Bubble growth processes are highly influenced by the elongational viscosity of the blowing agent-loaded polymer melt. Therefore, the elongational viscosity is an important parameter for the development of new polymers for foaming applications, as well as for the prediction of bubble growth processes. Thus, knowledge of the initial expansion and deformation behavior in dependency on the polymer, the blowing agent concentration, and the process conditions is necessary. This study presents a novel method for the in-line observation and analysis of the initial expansion and deformation behavior within the bead foam extrusion process. For this purpose, nitrogen as the blowing agent was injected into the polymer melt (PS and PLA) during the extrusion process. The in-line observation system consists of a borescope equipped with a camera, which was integrated into the water box of an underwater pelletizer. The camera is controlled by a developed trigger by means of angular step signal analysis of a rotary encoder on the cutter shaft of the underwater pelletizer. Thus, images can be taken at any time during the foaming process depending on the cutter position to the die outlet. It is shown that the developed method provides reliable results and that the differences of the initial expansion and deformation behavior during bubble growth can be analyzed in-line in dependency on real foaming process conditions and the type of polymer used. [ABSTRACT FROM AUTHOR]

The factors that affect electrophoretic mobility, namely particle velocity of polystyrene latex (PSL) particles and bubble growth rate on the electrode in the aqueous system were investigated during the continuous and pulsed direct current (DC) of electrophoretic deposition (EPD). The velocity of the PSL particles of varied sizes, i.e., 600, 300 and 100 nm at pH 5.5 and electric field strength of 4.1 V/cm were measured using a zeta potential meter under continuous and pulsed DC frequencies of 83.3, 10 and 5 Hz. The bubbles growth rate on the electrodes under the same condition was duplicated and measured separately using a recorded video attached to a microscope. Pulsed DC showed a more uniform particle velocity between 1.5 and 8 μm/s with a narrower particle velocity distribution than the continuous DC. The velocity of the particles was reduced by approximately 50% of the continuous DC. Pulsed DC also significantly reduced the bubble growth (gas formation) rate by three times lower than the continuous DC with a maximum bubble size of approximately 446 μm. [ABSTRACT FROM AUTHOR]

Acoustic cavitation and tissue deformation are studied by modifying a level-set method for compressible two-phase flows to consider viscoelastic tissue deformation. The numerical simulations performed using different shear moduli and bubble-tissue distances demonstrate various interactions between bubble and viscoelastic tissue, including inverted cone-shape bubbles, bubble migration, liquid jet formation, compressive and expansive tissue deformation, and tissue perforation. The bubble is observed to grow larger with increasing tissue bulk modulus and density. The maximum tissue deformation generally increases with decreasing initial bubble-tissue distance and with increasing tissue bulk modulus and density. The tissue shear modulus conditions that maximize tissue deformation are in the range of 1–10 MPa, unless the tissue density is very large.

This study focuses on the numerical illustration of bubble growth and addresses the inherent interface deformation problem associated with phase change in the Volume of Fluid (VOF) interface tracking method. To avoid the interface deformation, this study proposes a cell alternation algorithm that could simulate bubble growth with a sharp interface. The proposed algorithm identifies two types of cells near the vicinity of the interface, which include the primary-interface-cell and small-interface-cell. This algorithm computes mass transfer associated with a phase change at the primary interface cell and relocates it to a nearby cell full of vapor. The predictive accuracy of the proposed method is assessed with a one-dimensional Stefan phase change problem. In the case of the Stefan phase change problem, the results of simulations agree well with the results of the theoretical solution, and the predictive accuracy increases as the grid are refined. In addition, the proposed method is verified with two engineering problems which include bubble growth on a constant temperature surface and bubble growth in a microchannel. The simulation results show a good agreement with the results of the experiment in terms of bubble growth rate, bubble shape, and other parameters associated with experiment. Also, an insight into the temperature and velocity fields is provided in simulation which cannot be achieved directly through experiment.

We have investigated the effect of the surfactant Sodium Dodecyl Sulfate on the bubble growth and detachment processes in a bubble column system. A modified pendant drop model was employed to determine the dynamic surface tension. The dynamic surface tension approached the static surface tension value within a few seconds. A photographic technique and a laser-based electro-optical method were used to study the bubble size variation and the generation frequency, respectively. Parameters like bubble generation frequency, size, growth rate, and contact angle were found to be a strong function of surfactant concentration. Our results show that the addition of surfactant significantly reduces the bubble lifetime at the orifice. Such a decrease in the bubble lifetime has a direct impact on the bubble growth rate and departure size. Furthermore, bubble parameters vary with surfactant concentration only up to the critical micellar concentration. [ABSTRACT FROM AUTHOR]

Bubble-propelled Janus micromotors have attracted extensive attention in recent years and have been regarded as powerful tools in the environmental and medical fields due to their excellent movement ability. The movement ability can mainly be attributed to the periodic growth, detachment, and/or collapse of the bubble. However, subjected to the experimental conditions, the mechanism of bubble evolution on the motion of the micromotor could not be elucidated clearly. In this work, a finite element method was employed for exploring the role of bubble evolution in bubble-propelled Janus micromotors, which emphasized the growth and collapse of bubbles. After the proposed model was verified by the scallop theorem, the influence of the growth and rapid collapse of bubbles on micromotors was investigated. Results show that the growth and collapse of a bubble can drive the micromotor to produce a displacement, but the displacement caused by a bubble collapse is significantly greater than that caused by bubble growth. The reasons for this phenomenon are analyzed and explained. In addition to the influence of bubble size, the collapse time of the bubble is also investigated. [ABSTRACT FROM AUTHOR]

The boiling behavior on nano-structured surfaces is a frontier research direction in nuclear engineering. However, the mechanism of boiling heat transfer on nano-structured surfaces is still unclear. In this study, a depletable micro-layer model and the nano-structure model are proposed based on the Moving Particle Semi-implicit (MPS) method coupled with Meshless-Advection using the Flow-directional Local-grid (MAFL) scheme, also known as the MPS-MAFL method. The developed method in this paper establishes a bridge between the nano-scale surface structure heat transfer and the macroscopic bubble boiling. Only by knowing the nanoparticle size, porosity, and thickness of the nano-structure, the heat transfer of the nano-structure can be considered into the macroscopic boiling bubble growth process. The accuracy of the approach is validated by benchmark cases and experiments, respectively. The present method quantitatively simulates the bubble growth behaviors on nano-structured surfaces for the first time. The results indicate that the heat transfer contribution of the micro-layer to bubble growth was not neglectable, while the proportion of heat transfer rate of the micro-layer on the bared surface was 40.55% at ΔTw = 7.22 ℃ and 32.23% at ΔTw = 10.15 ℃. The heat transfer contributions of the micro-layer and the wicked fluid to the bubble growth in the nano-structured heater were about 42.13%, the ratio of them was 14:11. The current study provides a fundamental base for further investigations. [ABSTRACT FROM AUTHOR]

Surface wettability plays an essential role in bubble nucleation. This paper investigates the phase transition behaviour of argon films placed on inhomogeneous wettability substrates using molecular dynamics simulations. The location of bubble nucleation and initial nucleation time is investigated to reflect the effect of hydrophobic area fraction of inhomogeneous wettability surfaces on bubble nucleation. The results show that the bubbles appear first on the hydrophobic part of the inhomogeneous wettability surface. The relationship between hydrophobic area fraction and initial nucleation time is nonlinear. The initial nucleation time first decreases and then increases as the area of the hydrophobic region increases. In addition, the bubble nucleation process is restricted when the hydrophobic occupation is relatively large on inhomogeneous wettability surfaces. At last, the mechanism of bubble nucleation on inhomogeneous wettability surfaces is discussed in combination with the restrictive relationship between heat absorption and solid–liquid interaction energy. The amount of heat absorption does not directly determine the bubble nucleation. Bubble nucleation can arise in the location with a lower surface energy barrier once the heat absorption can overcome the solid–liquid interaction energy. [ABSTRACT FROM AUTHOR]

The measurement of the two-phase contact area is very important to determine the heat transfer coefficient in the process of direct contact heat transfer, but the direct measurement of the two-phase contact area is a difficult problem. The experiments are carried out utilizing a cylindrical Perspex tube of 100 cm in total height and 15 cm inner diameter. The active column height throughout the experiments is taken to be equal to 50 cm. Liquid Therminol®66 with four different initial temperatures (50 °C, 60 °C, 70 °C and 80 °C) is used as a continuous phase, while liquid R245fa at a constant temperature of 23 °C is used as a dispersed phase. In this paper, the empirical correlations between bubble growth and local convection heat transfer coefficient are obtained through modeling and measurement, and its correctness is verified by experiments. The results show that the bubble diameter is positively correlated with continuous phase temperature, flow rate ratio, and height, but the local convection heat transfer coefficient is negatively correlated with continuous phase temperature, flow rate ratio, and height. At the same time, it is found that the maximum error between the actual bubble diameter and the theoretical bubble diameter is 7%, and the error between the heat flux calculated by the local convection heat transfer coefficient and the actual heat flux is within 10%. This study provides theoretical guidance for an in-depth understanding of the direct contact heat transfer process and the development of high-efficiency waste heat recovery systems. [ABSTRACT FROM AUTHOR]

This study focuses on the numerical illustration of bubble growth and addresses the inherent interface deformation problem associated with phase change in the Volume of Fluid (VOF) interface tracking method. To avoid the interface deformation, this study proposes a cell alternation algorithm that could simulate bubble growth with a sharp interface. The proposed algorithm identifies two types of cells near the vicinity of the interface, which include the primary-interface-cell and small-interface-cell. This algorithm computes mass transfer associated with a phase change at the primary interface cell and relocates it to a nearby cell full of vapor. The predictive accuracy of the proposed method is assessed with a one-dimensional Stefan phase change problem. In the case of the Stefan phase change problem, the results of simulations agree well with the results of the theoretical solution, and the predictive accuracy increases as the grid are refined. In addition, the proposed method is verified with two engineering problems which include bubble growth on a constant temperature surface and bubble growth in a microchannel. The simulation results show a good agreement with the results of the experiment in terms of bubble growth rate, bubble shape, and other parameters associated with experiment. Also, an insight into the temperature and velocity fields is provided in simulation which cannot be achieved directly through experiment. [ABSTRACT FROM AUTHOR]

Bubble formation and dissolution have a wide range of industrial applications, from the production of beverages to foam manufacturing processes. The rate at which the bubble expands or contracts has a significant effect on these processes. In the current work, the hydrodynamics of an isolated bubble expanding due to mass transfer in a pool of supersaturated gas–liquid solution is investigated. The complete scalar transportation equation (advection–diffusion) is solved numerically. It is observed that the present model accurately predicted bubble growth when compared with existing approximated models and experiments. The effect of gas–liquid solution parameters such as inertia, viscosity, surface tension, diffusion coefficient, system pressure, and solubility of the gas has been investigated. It is found that the surface tension and inertia have a very minimal effect during the bubble expansion. However, it is observed that the viscosity, system pressure, diffusion, and solubility have a considerable effect on bubble growth. [ABSTRACT FROM AUTHOR]

The process of bubble growth inside an intensively evaporating sessile liquid drop on a heated structured black silicon has been studied. Experiments are carried out with volatile fluids FC-72, HFE 7100, ethanol, and water. The schlieren-based method was developed for investigations of the bubble growth inside a liquid droplet. The contact line velocity was measured during the droplet evaporation, including the case of a growing bubble inside the drop. The velocities of the contact line for droplet evaporation with/without bubble were compared. The contact line instability was detected emerging also due to the developed substrate structure. This can lead to an increase of local flows in the microregion and to significant heat transfer enhancement. [ABSTRACT FROM AUTHOR]

Control of cell structure is an important factor of fabricating polymer foam, which is related to technological design and product performance. In this article, a multibubble growth model of polymethyl‐methacrylate (PMMA) is established based on supercritical fluid foaming method and fluid simulation, aiming to analyze and predict the effects of foaming conditions (foaming temperature and foaming pressure) on the cell structures of PMMA foams. The bubble growth process is endothermic, resulting in a drop of temperature in PMMA/CO2 system, a decrease in diffusion coefficient and an increase in surface tension and viscosity, thereby preventing bubble growth. The pressure in the outer cells decreases faster than the pressure in the inner cells, causing the outer cells preferentially grow and deform, and will limit the growth of the inner cells. An empirical formula for the average cell size and foaming conditions is obtained. [ABSTRACT FROM AUTHOR]

Microchannel flow boiling is an efficient cooling solution for high-power-density miniaturized systems. Many studies on microchannel flow boiling focused on the dynamics of single vapor bubbles, while neglecting the interaction between bubbles, which is important in relevant applications. Here, numerical simulations are carried out to study the interaction between multiple vapor bubbles in microchannel flow boiling. The results show that for different numbers of bubbles in the microchannels with the same initial size and position of leading bubbles, the bubble size in a single-bubble microchannel is larger compared to the leading bubble of multiple-bubble cases because of heat absorption by the vaporization at the rear bubbles. As the initial volume ratio between the leading bubble and the rear bubble decreases, the leading bubble size in the downstream becomes smaller because of the reduced contact with the superheated thermal boundary layer. With increasing the Reynolds number, both the leading and the trailing bubbles increase slightly in size in the upstream of the heated region, because the bubbles at higher Reynolds number move faster and firstly get in contact with the superheated fluid. The increase in the bottom wall thickness increases the growth rate of the multiple bubble sizes with earlier bubble coalescence because of the higher upstream wall temperature by heat conduction in the solid wall. • Bubble in single-bubble scenario is larger than leading bubble of multiple bubbles. • Heat absorption of rear bubbles affects the expansion of the leading bubble. • Initial volume ratio influences contact with superheated thermal boundary layer. • Reynolds number influences bubble growth by affecting time to reach heated region. • Wall thickness influences bubble growth by affecting upstream wall temperature. [ABSTRACT FROM AUTHOR]

Bubble-propelled Janus micromotors have attracted extensive attention in recent years and have been regarded as powerful tools in the environmental and medical fields due to their excellent movement ability. The movement ability can mainly be attributed to the periodic growth, detachment, and/or collapse of the bubble. However, subjected to the experimental conditions, the mechanism of bubble evolution on the motion of the micromotor could not be elucidated clearly. In this work, a finite element method was employed for exploring the role of bubble evolution in bubble-propelled Janus micromotors, which emphasized the growth and collapse of bubbles. After the proposed model was verified by the scallop theorem, the influence of the growth and rapid collapse of bubbles on micromotors was investigated. Results show that the growth and collapse of a bubble can drive the micromotor to produce a displacement, but the displacement caused by a bubble collapse is significantly greater than that caused by bubble growth. The reasons for this phenomenon are analyzed and explained. In addition to the influence of bubble size, the collapse time of the bubble is also investigated.

Effusive to violently explosive eruptions of crystal-rich magmas are frequently found in volcanic records. The competing effects of rheological stiffening of magma in the presence of crystals and magma overpressure build-up in the presence of bubbles typically control the volcanic explosivity. The bubble growth exerts extensional stress on its wall, i.e., the melt+crystal matrix surrounding it. However, the rheology of crystal-rich magma under such extension along with the effect of crystals on bubble growth, are poorly understood. From analog experiments, this study finds that crystalline magma exhibits yield stress and power-law rheology with broadly comparable values under extensional and shear deformation. The pressure loss due to the presence of yield stress can significantly affect bubble growth in magma. Using bubble growth model in crystallizing magma, this study shows that the yield stress in melt+crystal matrix surrounding bubbles can exceed gas overpressure, preventing bubble growth. The model parameter search exhibits three regimes of bubble growth in crystallizing magmas for a wide range of magma decompression and crystallization rates during effusive to explosive volcanic eruptions. In the yield stress-limited regime, a complete halt in bubble growth can occur at a relatively small viscosity of crystal-rich basaltic magma (∼106 Pa s), and depending on the crystalline system, at a crystal volume as low as ∼30%. On the other hand, at relatively higher magma decompression rates, significant magma expansion associated with relatively rapid bubble growth, even at a relatively high normalized crystal content of >90%, could cause magma fragmentation and eruption explosivity. This study demonstrates that small changes in eruption conditions, such as magma decompression rates and crystallization rates, can cause significant changes in bubble growth dynamics with implications for transitions in volcanic eruption styles. • Crystal-rich magma exhibits Herschel-Bulkley type rheology under extension. • The presence of yield stress significantly hinder bubble growth. • Bubble growth with no yield stress to yield stress-limited to no bubble growth are obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molecular dynamics simulations are applied to study nucleation and growth of nanobubbles (NB) in CH 4 -H 2 O-Alcohol system. • Effect of alcohol concentration and alkyl chain length on NB nucleation and evolution is examined. • NBs nucleate at multiple sites in CH 4 -H 2 O-C 2 H 5 OH and CH 4 -H 2 O-nC 3 H 7 OH systems and grows in size through bubble coalescence. • In CH 4 -H 2 O-CH 3 OH system, primarily a single NB nucleates which grow by absorbing dissolved CH 4 from the liquid. • NB influences orientation and number of hydration water around dissolved methane molecules in the surrounding liquid. Nanobubbles (NBs) which are gas filled cavities of nanometre dimensions present in liquids attracted increasing attention in the recent years due to their application in various fields such as chemistry, biology, medicine etc. An important aspect of NB research is the study of effect of additives on formation and evolution of these bubbles. The present study examined by applying molecular dynamics simulations, the formation and evolution of methane NBs in the CH 4 -H 2 O-Alcohol system, which is known to form during alcohol induced dissociation of CH 4 hydrates in the natural gas extraction process. The effect of alcohol type and concentration on NB formation and evolution was examined through simulations of CH 4 -H 2 O-CH 3 OH, CH 4 -H 2 O-C 2 H 5 OH and CH 4 -H 2 O-nC 3 H 7 OH systems. The study revealed that increase in both concentration and the alkyl chain length of alcohols promoted NB formation. Alcohol molecules are found to enhance NB nucleation through accumulation near the NB-liquid interface resulting in a decrease in the surface tension (γ) at the interface. These effects become more pronounced as the alkyl chain length increases which explains the enhanced NB formation in systems containing nC 3 H 7 OH and C 2 H 5 OH compared to those containing CH 3 OH. The mechanism of formation and evolution of NBs is found to significantly depend on the type of alcohol present. NBs are found to nucleate at multiple locations in the systems containing nC 3 H 7 OH and C 2 H 5 OH which eventually coalesce to form a single large stable NB. In the presence of NBs which vary significantly in size, bubble growth was also found to occur through Ostwald ripening which involves transfer of CH 4 from smaller NB to the larger one. In contrast, in the CH 4 -H 2 O-CH 3 OH system, primarily a single NB nucleated which grew in size through absorption of CH 4 molecules dissolved in the liquid, rather than through coalescence or Ostwald ripening. The observed influence of alcohol type on the process of NB evolution is explained by examining the influence of alkyl chain length on γ and diffusivity of CH 4 molecules. Due to the role of NBs on methane hydrate regeneration from the hydrate melt, we examined the influence of NB in the CH 4 -H 2 O-Alcohol system on the organization of water molecules (HSWs) present in the hydration shell of dissolved CH 4. The value of F 4 order parameter of HSWs and the number of hydrogen bonded water rings in the hydration shell of CH 4 were analysed. The value of F 4 order parameter indicate that the hydrophobic alkyl chain of alcohol induced hydrate like arrangement of HSWs, which is more pronounced in the case of alcohol with longer alkyl chain. However, alcohol molecules are also found to dislodge HSWs around CH 4 resulting in a decrease in the number of water rings around dissolved CH 4 which is not conducive to hydrate formation. These observations are consistent with the reported dual effect of alcohol on hydrate formation with alcohol promoting hydrate formation at low concentrations and inhibiting at high concentrations. [ABSTRACT FROM AUTHOR]

• Air bubbles of 2.24 to 1.43 mm radii in a quiescent liquid are generated in laboratory. • A smoothed horizontal edge syringe tube and 97 degrees-rotated metallic sharp needles are the injectors. • Acoustical signals were recorded with a condenser microphone (PTFE-Electret) adapted as a hydrophone. • Physical-hydrodynamic events such as a beat phenomenon is observed as bubble shape changes. • Theoretical curve fits to bubble sound emissions is a promising tool to confirm the presence of beats. Understanding the passive acoustic signals of gas bubbles has become increasingly imporant due to their growing relevance in ambient marine acoustics and medical areas, as well as the recent search for dark matter by Bubble Chamber Detectors. Here the acoustic signatures of 2.24, 1.83, 1.75, 1.66 and 1.43 mm radii bubbles are reported experimentaly. They were generated by two different air injectors in a quiescent liquid, a standard plastic syringe tube and 97 degrees-rotated metallic needles. The evolution of the sound pulse over time is presented alongside simultaneous images of the bubbles detaching from the injector and moving freely in the liquid. The beat-wave phenomenon is the standard interference pattern between two sounds of slightly different frequencies, generating a beat-period envelope of "rosary chain" form. In this study, beats are observed when the bubble exhibits changes in its shape through Cassini-oval, trapezoid, 'guitar pick', ellipsoid and oblate shapes, which is in agreement with earlier results on bubble fragmentation in a locally sheared flow. Finally, theoretical curve fits of freely-oscillating, lightly-damped bubble sound emissions confirm that the beats are due to changes in the bubble shapes. [ABSTRACT FROM AUTHOR]

Nucleate boiling finds extensive applications in cooling systems across diverse industrial fields owing to its exceptionally effective heat transfer capacity. The effect of bubble growth on wall heat transfer is substantial during nucleate boiling. To examine this effect, a model for single bubble growth was developed using the Volume of Fluid (VOF) method, incorporating a dissipative microlayer model through user-defined functions to simulate microlayer evaporation. The effect of the thermophysical properties of the heating substrate on the wall heat transfer process was studied. The simulation results are in good agreement with the experimental data, and can accurately predict the wall temperature and bubble size. The study found that the thermophysical properties of the heating substrate had a remarkable impact on both bubble growth process and bubble influence area. Three stages were discovered in the evolution of the bubble influence area: microlayer-dominated stage, inertial expansion stage, and shrinkage stage. The study also found that the bubble influence factor (K) had a linear relationship with the thermal diffusivity of the heating substrate. The results in this paper were of great significance for improving the wall heat flux partitioning model. • The influence of the heating substrate thermophysical properties on bubble influence area was performed. • A single bubble growth model with a dissipative microlayer sub-model was established • Three stages were found in the evolution of the bubble influence area. • A linear relationship between bubble influence factor and heating substrate thermal diffusivity was found. [ABSTRACT FROM AUTHOR]

Synchrotron radiation dynamic imaging technology combined with the static characterization method was used to study the microstructural evolution and the growth kinetics of intermetallic compounds (IMCs) at the liquid Al/solid Cu interface. The results show that the interfacial microstructure can be divided into layered solid diffusion microstructures (AlCu3, Al4Cu9, Al2Cu3 and AlCu) and solidification microstructures (Al3Cu4, AlCu and Al2Cu) from the Cu side to the Al side. Meanwhile, the growth of bubbles formed during the melting, holding and solidification of an Al/Cu sample was also discussed, which can be divided into three modes: diffusion, coalescence and engulfment. Moreover, the growth of AlCu3 and (Al4Cu9 + Al2Cu3) near the Cu side is all controlled by both interfacial reaction and volume diffusion. The growth of Al3Cu4 adjacent to the melt is mainly controlled by the interfacial reaction, which plays a major role in the growth of the total IMCs. [ABSTRACT FROM AUTHOR]

The benefits of nucleate pool boiling phenomena and their potential applications on thermal management of various microelectronic devices have triggered the development of new approaches that augment the magnitude of heat transfer rate. To implement these approaches, an accurate estimation of the boiling heat transfer coefficient between the fluid and the heated surface is often required. The acquisition of the boiling heat transfer coefficient must follow a better understanding of the bubble ebullition cycle because of its inherent coupling with heat transfer mechanisms involved in this cycle. Bubble ebullition occurs by periodic bubble nucleation on a boiling surface, bubble growth, and subsequent bubble departure from the surface. Different parameters related to the dynamics of the bubble ebullition cycle, including bubble departure diameter, bubble waiting period, active nucleation site density, bubble growth period, bubble departure frequency, and bubble growth rate govern the heat transfer rate in the nucleate pool boiling. Thus, numerous empirical correlations that determine the boiling heat transfer coefficient have been proposed by many researchers according to different bubble dynamics parameters. To accurately predict the boiling heat transfer coefficient and boiling heat flux based on the bubble ebullition cycle, understanding bubble growth mechanisms and associated dominant parameters is crucial. In this review, different bubble growth mechanisms during nucleate pool boiling are thoroughly reviewed. Then, bubble dynamics parameters used in different correlations for determining the boiling heat transfer coefficient are discussed. Semi-empirical and empirical correlations for determining these parameters are also extensively provided. Additionally, a detailed review of factors affecting bubble dynamics parameters is provided. Next, different applications of nucleate boiling in cooling systems are reviewed. Overall, this review includes various correlations from experimental and numerical data, which can be used to better predict the heat transfer during nucleate boiling. [ABSTRACT FROM AUTHOR]

Microbubbles have important applications in optofluidics. The generation and growth of microbubbles is a complicated process in microfluidic channels. In this paper, we use a laser to irradiate light-absorbing particles to generate microbubbles in capillary tubes and investigate the factors affecting microbubble size. The results show that the key factor is the total area of the light-absorbing particles gathered at the microbubble bottom. The larger the area of the particles at bottom, the larger the size of the microbubbles. Furthermore, the area is related to capillary tube diameter. The larger the diameter of the capillary tube, the more particles gathered at the bottom of the microbubbles. Numerical simulations show that the Marangoni convection is stronger in a capillary tube with a larger diameter, which can gather more particles than that in a capillary tube with a smaller diameter. The calculations show that the particles in contact with the microbubbles will be in a stable position due to the surface tension force. [ABSTRACT FROM AUTHOR]

Summary: Low‐density expanded starchy products are often desirable, particularly in the snack food industry. Levels of shear and amylose are often deemed crucial factors for expansion. In this study, maize starches containing low (waxy), normal and high levels of amylose were compared after processing. Low shear processing used a popping head (similar to a rice‐cake machine), while high shear (~450 kJ kg−1) samples (pellets and directly expanded) were created using twin‐screw thermomechanical extrusion. Native starches and ground extruded materials (<106 µm) were popped using the same conditions (230 °C, 4 s, water content 12% wwb). All samples tested created fused aerated cakes, which had little or no remaining crystallinity, except for the directly popped waxy sample, which retained ~17% of its original crystallinity. Water absorbances and solubilities were influenced greatly by the starch source and marginally by the amount of processing. On processing, waxy samples showed increased solubility while those with normal amylose content had greater absorption. The densities of all the popped samples were similar despite marked differences in shear regime history and the major variations in the amylose and amylopectin ratios. These results challenge the expected relationships between shear and different starches' potential to expand. [ABSTRACT FROM AUTHOR]

Methane (CH4) transport from organic-rich fine-grained (muddy) shallow aquatic sediments to water column is mediated dominantly by discrete bubbles, which is an important natural source of greenhouse CH4. The lifespan of these bubbles within the sediment comprises two successive stages: growth from nucleation up to a mature size and then buoyant ascent toward the sediment–water interface. Bubbles often experience an oscillating overburden load due to the passage of winds and/or storm-induced short period surface waves or long-period tides, which can potentially affect both stages of the bubble’s lifespan. However, little is known about the wave effects over bubble growth phase. In the present work, this subject is investigated using a numerical single-bubble mechanical/solute transport model, which quantifies the effects of different parameters (amplitude and period) of the wave loading and of the water depth, over the bubble growth pattern in sediments and its specific characteristics. It was found that bubbles induce early sediment fracturing in the presence of waves, attributed to the low overburden load appearing at wave troughs. Bubbles at shallow depth rapidly grow at wave troughs by inducing multiple intense fracturing events. However, this ability decreases with an increasing water depth because of a slower solute influx. In the presence of waves, bubbles mature in shorter time, whose contrast to the no wave case is controlled by the ratio of wave amplitude to equilibrium water depth. Due to the higher frequency of occurrence of wave troughs for shorter-period waves, bubble growth is accelerated compared with the case of longer-period waves. Overall, our modeling suggests that the fastest bubble growth can be predicted for higher amplitude, short-period waves traveling in shallow water. We further infer that accelerated bubble growth, along with subsequent wave-induced ascent can sufficiently shorten the bubble’s total lifespan in sediment, which explains the observed episodic in situ ebullitions correlated with wind- or storm-induced waves.

The boiling behavior on nano-structured surfaces is a frontier research direction in nuclear engineering. However, the mechanism of boiling heat transfer on nano-structured surfaces is still unclear. In this study, a depletable micro-layer model and the nano-structure model are proposed based on the Moving Particle Semi-implicit (MPS) method coupled with Meshless-Advection using the Flow-directional Local-grid (MAFL) scheme, also known as the MPS-MAFL method. The developed method in this paper establishes a bridge between the nano-scale surface structure heat transfer and the macroscopic bubble boiling. Only by knowing the nanoparticle size, porosity, and thickness of the nano-structure, the heat transfer of the nano-structure can be considered into the macroscopic boiling bubble growth process. The accuracy of the approach is validated by benchmark cases and experiments, respectively. The present method quantitatively simulates the bubble growth behaviors on nano-structured surfaces for the first time. The results indicate that the heat transfer contribution of the micro-layer to bubble growth was not neglectable, while the proportion of heat transfer rate of the micro-layer on the bared surface was 40.55% at ΔTw = 7.22 ℃ and 32.23% at ΔTw = 10.15 ℃. The heat transfer contributions of the micro-layer and the wicked fluid to the bubble growth in the nano-structured heater were about 42.13%, the ratio of them was 14:11. The current study provides a fundamental base for further investigations.