Bubble Rise Research Articles

Dynamics of single bubble ascension in stagnant liquid: An investigation into multiphase flow effects on hydrodynamic characteristics using computational simulation

Industrial operations often involve multiphase flows, where the motion of bubbles plays a crucial role in determining hydrodynamic properties. In the context of modern practices, advanced computational solvers are increasingly employed to simulate the interactions and trajectories of bubbles within complex flows. This study stands out in its unique examination of the computational software COMSOL's capability to accurately simulate the upward motion of a single bubble within quiescent water, akin to a liquid-like environment. The novelty lies in the comprehensive coverage of various container diameters (ranging from 10 to 80 mm) and heights (from 25 to 300 mm) relative to the air bubble diameter (ranging from 0.5 to 8 mm). Through meticulous comparisons between nine empirical formulas and numerically projected bubble ascent through a water column, a remarkable level of agreement emerges, underscoring the precision and consistency of the simulations. These simulations unveil intriguing findings, shedding light on the intricate interplay of forces governing bubble behavior. Notably, variations in drag forces induce changes in bubble shapes as a function of diameter, while the ascent of bubbles is accompanied by distinctive vortices, resulting in fascinating asymmetry. Furthermore, vorticity concentrates within the bubble, particularly in lighter fluid regions characterized by reduced pressure. The study also unveils how larger aspect ratios minimize flow drag, consequently boosting ascent velocities, and demonstrates the influence of container diameter on the rising velocity. Gravitational forces are found to reduce ascent velocities at greater column heights, while the rate of air bubble rise escalates with its size. This meticulous exploration of bubble dynamics in multiphase flows yields invaluable insights for diverse industrial applications, ultimately enhancing our understanding of this complex phenomenon. The strong alignment observed between empirical formulations and numerical simulations within the COMSOL framework underscores the utility of such computational tools for the study and design of multiphase flows' intricate dynamics.

Numerical simulation of incompressible interfacial flows by a level set re-distancing method with improved mass conservation

This paper presents a level set re-distancing (NLS) method to better preserve mass conservation and more accurately predict interface evolution in the simulation of incompressible interfacial flows. In this method, the level set function is first advected by an advection equation. The key to this method depends on the simulation of the re-distancing equation subject to a proper mass-correction term. The performance of the proposed NLS method is verified against benchmark cases such as vortex deforming and Zalesak’s cases. The NLS method is then combined with an explicit Adams–Bashforth scheme on a staggered Eulerian grid to obtain Navier–Stokes solutions. Two-layer liquid sloshing, dam-break flow and Rayleigh–Taylor instability are simulated and compared with numerical or experimental results reported in literature. Two-phase flows that involve nonlinear phenomena such as bubble rising and bubble bursting at a free-surface are also chosen to demonstrate the ability of the proposed method in considering surface tension. The NLS method proposed in this paper is compared with the CLSVOF method of Li and Yu (2019) in terms of computational time in dam-break flow and Rayleigh–Taylor instability cases.

Quantification and correlation analysis of bubble characteristics and heat transfer performance in direct contact heat exchanger

In this work, a combination of morphological processing and watershed algorithm is proposed to measure bubble size, based on which an improved frame difference method is proposed to obtain bubble velocities with an F1 score of 0.96. Empirical equations for the boiling properties of flow in immiscible fluids and their influencing factors are developed. Correlation equations for the Nusselt (Nu) number and Colburn (j) factor are developed, with mean deviations of 5.42% and 5.47%, respectively. The results show that the increase in bubble rise rate and the trend of bubble growth become slower with the increase in the flow rate of the dispersed phase. In contrast, the temperature of the continuous phase has a negative correlation on the bubble growth and almost no effect on the bubble velocity. In addition, the heat transfer coefficient, which increases with the increase of the flow rate of the dispersed phase, has a negative correlation with the initial temperature difference. The main objective of this study is to provide a new method for measuring bubble parameters during direct contact boiling heat transfer and to provide new ideas for studying direct contact boiling heat transfer.

The role of the water–air and pulp-froth interfaces on particle detachment: Impact of particle size, type, contact angle and bubble rise velocity

Although the pulp-froth interface is thought to be very important to particle detachment and therefore overall flotation recovery, experimental evidence to back this is contradictory with recent observation indicating that detachment may not be as rigorous as previously thought. We investigate the effect of the interface (air–water and froth-water) on particle detachment as function of particle size, density, hydrophobicity, and bubble sizes. Bubbles were loaded with particles of size classes between 53 µm and 1018 µm and were allowed to collide with the a given interface while videos of the interaction were taken. using a high-speed video camera. The results from the experiments indicate that particles attached to bubbles do not detach when a loaded bubble collides with the interfaces. Further, the particle properties - (size and type of the particles, and contact angle) and bubble had no influence on particle detachment at the interface. However, the particles attached as agglomerates dropped off upon impact and as a result of bubble shape deformations. Further, observations from the water froth interface show that the impact upon collision can significantly shake of particles from within the froth while the particles on the bubble remain attached. Under our experimental conditions, coalescence was also observed not to be as rapid, with loaded bubbles remaining in contact with the water-froth interface for not less than 26 s.

Experiments on fluid entrainment and slip in continuous bubble plumes

A series of laboratory experiments are reported in which a continuous stream of bubbles rise from a small source at the base of a tank of water. Using different nozzles, bubble sizes $d$ ranging from 1.2 to 11.6 mm were produced for a number of gas volume fluxes, $Q_b$ , ranging between 1.1 and $21.1\times 10^{-6}\ {\rm m}^3\ {\rm s}^{-1}$ . Within a small distance from the source, the slip speed of these bubbles exceeds the speed of the equivalent single-phase plume with the same buoyancy flux, leading to formation of what we refer to as the ‘slip plume’ regime. Through a combination of high-speed photography, coupled with flow visualisation in the plume and the ambient fluid using dye, we find that the bubble speed and the fluid speed remain nearly constant with height, with the maximum fluid speed being of order $0.30\pm 0.03$ of the bubble speed. Using the filling box method, we also find that the net fluid volume flux in the slip plume increases linearly with distance from the source at a rate $Q_l = \lambda Bz/v_s^2$ , where $B$ is the buoyancy flux of the gas, $v_s$ the rise speed of the gas bubbles, $z$ the distance above the source and $\lambda$ is a constant related to the dimensionless volume of fluid in the wake of each bubble. This slip-dominated flow regime can be understood in terms of kinetic energy imparted to the fluid as the bubbles rise and release potential energy. Further experiments with particle-laden plumes illustrate similar scalings for the volume flux in a particle-driven slip plume once the slip speed of the particles exceeds the bulk speed of the equivalent single-phase buoyant plume with the same buoyancy flux. Near the source the slip speed may be smaller than the plume speed, and the flow follows the classical model for a turbulent buoyant plume, with the transition to the slip regime occurring at a distance $z^*\approx (32\pm 5)\lambda ^{3/2} B/v_s^3$ from the source, where the dimensionless parameter $\lambda$ relates to the dimensionless volume of the fluid wake, which we find varies with the Reynolds number of the particles.

Comparison of bubble parameters in natural and chemical surfactant solutions: a force analysis

The authors have investigated the potential of a plant-based natural surfactant in the modification of various bubble parameters. Bubble dynamics at the orifice were studied in natural surfactant solutions extracted from the plant Sapindus mukorossi at concentrations below and above its critical micellar concentration (CMC). The results were compared to the ones obtained with Sodium Dodecyl Sulfate solutions. The CMC values of Sapindus mukorossi and Sodium Dodecyl Sulfate are 7.5 × 10−3 g/cc and 2.39 × 10−3 g/cc, respectively. A photographic method was employed to observe bubble formation at the orifice. The results show that biosurfactants, like chemical surfactants, have a comparable effect on bubble density, size, and rise velocity. Experimentally determined bubble radius, volume, and radial velocity were used to calculate various forces contributing to the bubble dynamics. The buoyancy, pressure, and surface tension forces were significantly stronger in magnitude in comparison to the gas momentum, viscous drag, and added mass forces. Our findings suggest that the significance of various dynamic forces involved in bubble growth dynamics varies according to the bubble generation frequency regimes. We report for the first time the potential of Sapindus mukorossi in altering bubble properties and surface forces at the orifice and its usage in various bubble-related industrial applications.

Fate of bubble clusters rising in a quiescent liquid

We use experiments to study the evolution of bubble clusters in a swarm of freely rising, deformable bubbles. A new machine learning-aided algorithm allows us to identify and track bubbles in clusters and measure the cluster lifetimes. The results indicate that contamination in the carrier liquid can enhance the formation of bubble clusters and prolong the cluster lifetimes. The mean bubble rise velocities conditioned on the bubble cluster size are also explored, and we find a positive correlation between the cluster size and the rise speed of the bubbles in the cluster, with clustered bubbles rising up to $20\,\%$ faster than unclustered bubbles.

Investigation of Taylor bubble dynamics in annular conduits with counter-current flow

This study numerically investigates counter-current slug flow by considering the motion of a Taylor bubble in annular conduits with downward-flowing liquids using the Volume-of-Fluid method implemented in the commercial computational fluid dynamics software ANSYS Fluent (Release 19.2). The translational velocity of a counter-current ascending or co-current descending Taylor bubble in vertical concentric annuli and the corresponding distribution parameter (C0) are analyzed. The latter is correlated in terms of Eötvös number (Eo) and inverse viscosity number (Nf) within the range of Eo between 40 and 400 and Nf between 40 and 320. The proposed correlation provides an accurate fit to the numerical data with an average error of 2.64%, and is successfully compared with published numerical findings. In general, the smooth and stable shape of the bubble is disrupted as the counter-current flow velocity (Frl) increases above a critical value, leading to the formation of surface waves and the displacement of the bubble tip away from the annular gap center and towards the outer pipe. C0 increases with Eo and Nf, plateauing at high values of Eo. The effects of annulus inclination (θ) and eccentricity (ε) on bubble rise velocity are examined within the common range of θ and ε encountered during the drilling of oil, gas, or geothermal wells, i.e. 0° ≤ θ ≤ 60° and 0 ≤ ε ≤ 0.7, and their impact on the C0. The increasing Frl and θ lead to a streamlined bubble with pointed nose and thus a reduction in the wrap angle (θwrap), ultimately leading to reduced drag compared to the vertical annulus case and a decrease in C0. As the ε increases, which is accompanied by an increase in the degree of bubble eccentricity, the corresponding C0 decreases. For a constant Eo = 100 and Nf = 160 with inclination angle of θ = 40°and eccentricity of ε = 0.5, the C0 < 1 is observed.

Direct measurements of gas flux at seep sites using a broadband split-beam echosounder

Measurement of methane gas flux from oceanic seep sites is challenging, given the ephemeral nature and the heterogeneous spatial distribution of seeps. Acoustic systems offer a solution, as they make synoptic measurements of the water column, and the gas bubbles are strong acoustic scatterers. Here, we present a method to directly estimate gas flux using a calibrated broadband split-beam echosounder. The vertical range resolution of the broadband system facilitates discrimination of individual bubbles in the acoustic record. By comparing measurements of bubble target strength to an analytical scattering model, bubble radii can be directly measured from the acoustic data. Concurrently, split-aperture processing allows for the precise tracking of bubbles as they rise from the seafloor for measurement of bubble rise velocity. Together, the observations of bubble radius and rise velocity offer a measure of gas flux, requiring nothing more than a vessel transiting over a seep site. Application of this method to seep data collected on the East Siberian Arctic Shelf shows good agreement between resulting measurements of bubble radii (0.68–8.40 mm) with those made using optical sensors, and bubble rise velocities (4–36 cm/s) are consistent with published measurements and models. Extrapolating from single bubbles measurements, our estimates of regional methane flux (2.9 × 104 kg/year) suggest that carbon emissions in this region may be lower than previously believed.

Effects of gas flow rate on rising bubble chains and induced flow fields: An experimental study

This paper reports an experimental investigation of the characteristics of bubble chains and their induced flow fields in a quiescent fluid at gas flow rates of 5, 10, 50, and 100 ml/min. The shadowgraphy and laser-induced-fluorescence particle image velocimetry (LIF-PIV) were used to analyze quantitatively the bubble morphology, kinematics, and induced flow fields. The results show that with increasing gas flow rate, the bubbles exhibit a larger average diameter, aspect ratio, and more-abundant morphology. The bubble motion includes a rectilinear rise followed by an oscillating rise, and the position where the bubble deviates from the linear trajectory is associated with the point of maximum bubble aspect ratio. The amplitude of bubble oscillation and the position of the instability both increase with the gas flow rate, except for the case of 50 ml/min. The bubble-induced flow field at higher gas flow rates exhibits stronger entrainment, which reflects the ability of the flow to entrain the surrounding fluid. The instantaneous flow-field results show that bubble-induced wake shedding is the main cause of the change in bubble rise state and trajectory instability. The direction of bubble deflection is related directly to the sequence of wake shedding: when the clockwise (resp. counterclockwise) vortex in the wake is the first to shed, the bubble deflects to the left (resp. right). The study also reveals that the simultaneous shedding of counterclockwise and clockwise vortices at 50 ml/min results in the bubbles continuing to rise rectilinearly for a period of time, and the position of trajectory destabilization has a maximum height.

Bubble behavior in a vacuum fluidized bed

Bubble behavior in a vacuum fluidized bed was investigated in this work. Experimental results showed that bubble diameter and rise velocity increased with declining the pressure, whereas bubble density decreased. The evolution of bubble density with bed height could be divided into three stages on the basis of the corresponding net-coalescence rates. The decrease in bubble density in the bottom region accelerated as the pressure decreased, whereas the increase in bubble density in the top region was gentle. Increasing the vacuum degree enlarged the variation in bubble size, resulting in the decline of operating stability in the fluidized bed. A new correlation that considered the effect of operating pressure on bubble behaviors exhibited accurate prediction in the vacuum fluidized bed. Bubble velocity was proportional to bubble diameter for small bubbles, and bed structure obviously affected the rise velocity of large bubbles. The distribution of the bubble aspect ratio was positively skewed and many bubbles had a tendency to become slender as the operating pressure decreased.

Numerical study of bubble rise in a three-dimensional sinusoidal channel

The bubble formation phenomenon and its movement have numerous applications in the shipbuilding, nuclear, mechanical, and ocean industries. Thus, a complete understanding of bubble rise is of immense importance in the fields mentioned above. Although, even after a plethora of research, a significant understanding of bubble wobbling and path instability still needs to be achieved. Furthermore, the complexity increases when a bubble rises in complex channels. Although various two-dimensional studies have attempted to report the bubble wobbling in the complex channels, a three-dimensional study on it still needs to be explored. Thus, in the present study, we attempted to report the bubble rise tendency in a three-dimensional sinusoidal channel. As bubble rise velocity plays a significant role in bubble wobbling, we attempted to study the bubble's path instability and rising velocity at different Reynolds numbers (Re) and Bond numbers (Bo). The maximum bubble rise velocity was observed to increase with Reynolds number (Re) while it decreases with an increase in Bond number (Bo). Furthermore, the wobbling tendency was also less in three-dimensional cases compared to previously reported two-dimensional studies. The bubble wobbling was reported to increase with the Reynolds number with a more periodic nature of the velocity profile. Bubble wobbling increased with an increase in a Bond number less than 9. The multi-phase simulation was performed on the open-source solver Gerris. The present study unveiled various aspects of bubble rise in three-dimensional sinusoidal channels and highlighted the role of rising velocity in the path instability of bubble rise.

Impact of surfactants on the rise of deformable bubbles and interfacial gas–liquid mass transfer

Axisymmetric numerical simulations of the hydrodynamics around rising bubbles are performed in order to investigate the impact of surfactants on the bubble dynamics. Surfactants are assumed to be insoluble. The transport of the adsorbed surfactants is computed along the deforming surface at large surface Péclet number, and Marangoni stresses are taken into account. This simulation model leads to the stagnant-cap regime, with partially immobile interfaces. A parametric study is performed on cases at given Archimedes number, by varying the degree of contamination (Marangoni number) but maintaining a nearly constant Eötvös number. The presence of surfactants affects the rise velocity for oblate bubbles less than for spherical bubbles: the increase of the drag coefficient, due to interface contamination, is mitigated by a lower bubble deformation. When the cap angle $\theta _{cap}$ belongs to the southern hemisphere, the aspect ratio $\chi$ is found to decrease with contamination: the dynamic pressure responsible for the bubble distortion is lowered, related to the decline of kinetic energy. As soon as $\theta _{cap}$ lies in the northern hemisphere, the pressure stress causing distortion becomes independent on $\theta _{cap}: \chi$ no longer evolves with contamination, and already matches the prediction for fully immobile interfaces. Mass transfer of a passive scalar across the contaminated interface is also analysed. Surprisingly, the Sherwood number $Sh$ is found to follow the same law as for spherical shapes (Kentheswaran et al., Intl J. Heat Mass Transfer, vol. 198, 2022, 123325), allowing us to predict the decrease in $Sh$ due to contamination. These results reveal the couplings between interface immobilisation, bubble deformation, rise velocity and interfacial mass transfer.

Optimizing Design and Operational Parameters for Enhanced Mixing and Hydrodynamics in Bubbling Fluidized Bed Gasifiers: An Experimental and CFD-Based Approach

An experimental investigation of hydrodynamics of gas-solid flow is carried out by engaging different designs of air distributor plates. An analysis of three different plates, i.e., perforated, 45° slotted and novel hybrid plate, revealed the difference in pressure drop and minimum fluidization velocities (Umf) for varying input operational variables. Umf is found to be lowest for perforated and highest for 45° slotted plate, whereas pressure drop is found to be highest for 45° slotted plate and lowest for novel hybrid distributor plate. The bubbles rise velocity ratio (Umf,b/Umf,f) is noticed minimum for 45° slotted plate due to relatively larger bubbles originating from the bigger slot openings and maximum for perforated distributor plate owing to smaller bubbles with dominant axial rise. Furthermore, the bed height rise ratio (h/L) is observed as a minimum for perforated distributor and maximum for 45° slotted plate due to larger bubbles through 45° slots rupturing the bed surface, causing more bed expansion. Furthermore, CFD analysis is also carried out to observe the insight flow dynamics using the distributor plates. The simulations use a two-fluid model (TFM) and K-Epsilon turbulence models. CFD model shows promising results in agreement with the experimental results. CFD results revealed that the lower portion enhanced lateral dispersion/mixing of solid particles due to 45° angular openings of an air inlet. In contrast, the perforated plate exhibited a straight upward motion of small air bubbles, causing no radial/lateral mixing. CFD results for the hybrid plate show the mixed axial as well as lateral mixing of solids by revealing velocity distribution; therefore, the novel hybrid plate is found to be an optimum distributor plate due to its lowest pressure drop, adequate Umf, intermediary bed height rise ratio and moderate bubble rise velocity ratio across the bed.

Bubble-assisted matte transportation into slag phase: A numerical investigation

Copper loss into the slag phase during the smelting process can be minimized by controlling gas bubble size and hydrodynamics. Here, bubble rising characteristics from copper matte to slag phase were investigated using the volume-of-fluid modelling approach, in which the continuous surface force model was adopted to define the surface tension parameters. The simulated results for bubble terminal velocities in bulk water and the literature data showed relative errors up to 4.51 %. The obtained qualitative and quantitative data from simulation at the liquid–liquid interface agreed well with the literature experimental results. The simulation setup was applied to investigate three different sizes of bubble rising dynamics from matte to slag phase with the bubble Reynolds number (Re) up to 1734 and the Eotvos number (Eo) up to 3.2. For low Re and Eo, the bubble rising velocity decreased before the matte film rupture and the bubble required a long time to complete that film drainage due to the balance of interfacial tension force and bubble buoyancy. No matte residue associated with the bubble rise in the slag phase was obtained because of restoring initial, non-deformed shape of bubbles. For the higher Re and Eo, quicker matte film drainage was obtained around the upper bubble surface while the entrained matte contribution to the slag phase was strongly dependent on the bubble-shape deformation, which was discussed with the well-known Grace diagram. The decreasing viscosity and increasing surface tension of the slag phase significantly affected the matte film height more than the film rupture time. The film height and rupture time increased and decreased with increasing Eo, respectively. The outcomes of our studies are useful for the design and operation of smetling furnaces in pyrometallurgical purification of metal concentrates.

Numerical investigation on the bubble rising dynamics in ratchet channels filled with viscoelastic liquids

In this paper, we investigated the dynamics of a bubble rising inside ratchet channels filled with viscoelastic liquids by means of volume-of-fluid-based direct numerical simulations. The exponential Phan–Thien–Tanner constitutive model was used to describe the rheological behaviors of the nonlinear viscoelastic fluid. The effects of fluid elasticity [characterized by the relaxation time (λ)] and ratchet angle (θ) are mainly discussed in respect of bubble dynamics (e.g., rising velocity, flow field, and stress field, etc.). Our results found that the bubble rise velocity increases with fluid elasticity, and the average bubble velocity can be reduced up to 20% at low elasticity in ratchet channels. In addition, the periodic arrangement of the ratchet influences the distribution of the stress field, the vorticity component, and also the deformation of the entangled polymers in the flow. It was observed that the distributions of the stress field and the trace of the conformation tensor change significantly in a dense ratchet channel compared to a sparse one. Interestingly, the bubble velocity gradually increases after the bubble emerges from the convergent section, whereas it decreases on approaching the convergent section. The dynamical bubbles can be manipulated by the surrounding fluid viscoelasticity and ratchet channels, which will be useful in oil extraction and chemical process involving complex non-Newtonian fluids.

Transient simulation of SO2 absorption into water in a bubbling reactor

A bubbling reactor is an important type of gas scrubber to reduce SO2 emissions in maritime shipping. Both experiments and simulations were conducted to study the relationship between the periodic gas bubbling process and SO2 concentration at the outlet of the reactor, and the entrainment of liquid droplets on SO2 absorption. The accuracy of the model was verified by comparing the bubble size, the depth of bubbles injected into the water, and the SO2 concentration obtained in both experiments and simulations. The gas bubbling process is accompanied by bubble formation, rise, and collapse. The gas bubbling period is affected by the disturbance of the liquid level. The period of the SO2 concentration at the outlet of the gas bubbling reactor is smaller than that at the gas jar outlet which acts as the gas buffering region. The amounts of water carried out of the bubbling reactor by the gas bubbling process increase with the gas flow rates. The droplets and liquid film in the gas jar and the connecting tube play an important role in the absorption of SO2. This study encourages more research to reduce the fluctuation of SO2 concentration and consider droplet entrainment in the design of bubbling reactors.

A three-dimensional non-orthogonal multiple-relaxation-time phase-field lattice Boltzmann model for multiphase flows at large density ratios and high Reynolds numbers

This study proposes a three-dimensional non-orthogonal multiple-relaxation-time (NMRT) phase-field multiphase lattice Boltzmann (PFLB) model within a recently established unified lattice Boltzmann model (ULBM) framework [Luo et al., Phil. Trans. R. Soc. A 379, 20200397, 2021]. The conservative Allen-Cahn equation and the incompressible Navier-Stokes (NS) equations are solved. In addition, a local gradient calculation scheme for the order parameter of the Allen-Cahn equation is constructed with the non-equilibrium part of the distribution function. A series of benchmark cases are conducted to validate the proposed model, including the two-phase Poiseuille flow, Rayleigh-Taylor instability, binary liquid/metal droplet collision, and a bubble rise in water. The present simulation results are in good agreement with existing simulation and experimental data. In the simulation of the co-current two-phase Poiseuille flow, the present model is proven to resolve the discontinuity at the phase interface and provide accurate results at extremely high density ratios (i.e., up to 106). Finally, the proposed model is adopted to simulate two challenging cases: (1) water droplet splashing during its impacting on a thin liquid film and (2) liquid jet breakup. The simulation results demonstrate an excellent agreement with previous experimental results, both qualitatively and quantitatively. In these simulations, the Weber number and Reynolds number reach 105 and 6000, respectively, and the viscosity can be as low as ∼10−4, in the lattice unit.

Analysis of Interaction and Flow Pattern of Multiple Bubbles in Shear-Thinning Viscoelastic Fluids

A numerical study was conducted on the interaction of bubbles with different diameters and arrangements in shear-thinning viscoelastic fluids using OpenFOAM. The Volume of Fluid (VOF) method combined with the surface tension model was used to track the gas–liquid interface, and the rheological properties of the fluid were characterized with the Giesekus model. The numerical results are corresponded with the previous references, verifying the correctness of the simulation method. The influences of the initial bubble diameter, horizontal spacing, and arrangement on the motion state of three parallel bubbles were studied in detail. The flow pattern of the bubble rising was analyzed and compared with the motion state of parallel unequal double bubbles. As the diameter of the bubbles increases, the interaction among three equal size bubbles is changed from coalescence to detachment. Changing the diameter of one of the bubbles will significantly affect the movement of the larger diameter bubble, which is due to the enhancement in kinetic energy. The final state of some arrangement ways is consistent with the phenomenon of unequal double bubbles. The shear thinning effect, the velocity difference between bubbles, and the flow field around bubbles are considered the main reasons that decide the interaction between bubbles.

Numerical study of the geometric characteristics and kinetic behavior of single bubble rise processes in different liquids

The characterization of single bubble in gas–liquid two phase flow is a critical yet unresolved issue in both science and industry. In this study, the volume-of-fluid (VOF) method is used to numerically simulate and experimentally investigate the effect of initial bubble diameter, liquid viscosity, and surface tension on bubble deformation and the internal flow field of the bubble in a pool of stationary liquid. The findings indicate that as liquid viscosity increases, the bubble's rising speed decreases, and the bubble tends to oscillate. The variation in bubble deformation ratio and the degree of fluctuation increase with the bubble's initial diameter and decrease with the viscosity of the liquid phase. Additionally, as the surface tension of the liquid decreases, the bubble becomes more prone to rupture, and the number of ruptures increases. The flow field inside the bubble can be classified into three categories: “double main vortex type,” “double main vortex type with separated vortex,” and “double main vortex type with scattered vortex.” The velocity reaches its maximum at the center of each vortex type, and the velocity at the interface varies as the bubble interface shape changes. This work lays the foundation for the study of the flow field inside the bubble and improves the predictability of gas–liquid equipment design.