In this study,the dynamic characteristics of microscale floating bubbles near the vertical wall are studied.This occurrence is common in industrial and natural phenomena.Although many studies have been conducted on mi...In this study,the dynamic characteristics of microscale floating bubbles near the vertical wall are studied.This occurrence is common in industrial and natural phenomena.Although many studies have been conducted on microscale bubbles,few studies investigate floating bubbles with very small Reynolds number(Re)near the wall,which is the main research goal of this study.Therefore,this study establishes a model for the ascent of small-scale bubbles near a vertical wall using the interFoam solver in OpenFOAM.This study investigates the influences of diverse viscosity parameters,varying distances from the wall,and different gas flow rates on the terminal velocity,deformation,and motion trajectory of bubbles.The results reveal that as liquid viscosity increases,the Re of bubbles gradually decreases and reaches a minimum of 0.012,which is similar to the Re of micrometer-sized bubbles in water.The characteristics of the wall-induced force in the longitudinal direction are closely related to the changes in liquid viscosity.Under low-viscosity conditions,the induced lift is the principal form of action,whereas under high-viscosity conditions,it is primarily manifested as induced drag.展开更多
To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software ...To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.展开更多
During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a rest...During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.展开更多
The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurren...The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurrent flow in annulus is carried out under different working conditions to reveal how the wellbore inclination angle,liquid phase property and countercurrent liquid velocity affect the bubble deformation and bubble migration trajectory/velocity,and to establish a bubble migration velocity prediction model.The bubbles in the countercurrent flow mainly migrate in two modes:free rising of isolated bubbles,and interactive rising of multiple bubbles.The bubbles migrate by an S-shaped trajectory in the countercurrent flow.With the increase of countercurrent liquid velocity,the lateral oscillation of bubbles is intensified.The increases of wellbore inclination angle,liquid density and liquid viscosity make the bubble migration trajectory gradually to be linear.The bubble is generally ellipsoidal during its rising.The wellbore inclination angle has little effect on the degree of bubble deformation.The bubbles are ellipsoidal during rising,with little influence of wellbore inclination angle on bubble deformation.With the increase of liquid viscosity and density,the aspect ratio of the bubble decreases.As the wellbore inclination angle increases,the bubble migration velocity gradually decreases.As the liquid viscosity increases,the bubble migration velocity decreases.As the liquid density increases,the bubble migration velocity increases slightly.The established bubble migration velocity prediction model yields errors within±15%,and demonstrates broad applicability across a wide range of operating conditions.展开更多
The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclea...The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclear fuels containing pressurized FGBs,a mechanical constitutive model for the equivalent solid of FGBs was developed and validated.This model was based on the modified Van der Waals equation,incorporating the effects of surface tension.Using this model,the micromechanical fields in irradiated U-10Mo fuels with randomly distributed FGBs were calculated during uniaxial tensile testing via the finite element(FE)method.The macroscopic elastic constants of the irradiated U-10Mo fuels were then derived using homogenization theory,and the influences of bubble pressure,bubble size,and porosity on these constants were examined.Results show that adjacent FGBs exhibit mechanical interactions,which leads to distinct stress concentrations in the surrounding fuel skeleton.The macroscopic elastic constants of irradiated U-10Mo fuels decrease with increasing the macroscopic porosity,which can be quantitatively described by the Mori-Tanaka model.In contrast,bubble pressure and size have negligible effects on these constants.展开更多
Submarine pipelines are critical infrastructures for offshore energy transport and communications. Understanding their structural response to near-field explosions is crucial for enhancing their blast resistance and o...Submarine pipelines are critical infrastructures for offshore energy transport and communications. Understanding their structural response to near-field explosions is crucial for enhancing their blast resistance and operational safety. This study presents a computational study on the interaction between explosion-induced bubbles and a seabed-mounted pipeline. A recently developed computational framework is employed, which couples a compressible fluid solver with a finite element structural solver via a partitioned procedure. An embedded boundary method and a level-set method are employed to handle the fluid-structure and gas-liquid interfaces. Using this framework, we analyze the flow field evolution, bubble dynamics, and transient pipe deformation. Two distinct response modes are identified: periodic oscillation under low-pressure loading and downward collapse triggered by high-pressure loading and bubble jet impact. Specifically, under high-pressure conditions, the pipe initially deforms inward, generating a localized high-pressure zone within the concave region. During structural rebound, the trapped fluid is expelled upward, giving rise to a bubble jet. Further parametric studies on the pipe's internal pressure, wall thickness, and support angle reveal several key insights. A higher internal pressure delays structural collapse, and a greater pipe thickness results in more uniform implosion morphologies. The support angle strongly influences the collapse dynamics, with the shortest collapse time occurring at 60 °. These findings offer new insights for the protective design of submarine pipelines.展开更多
The size and distribution patterns of bubbles within a laboratory-scale coarse-particle flotation column were examined using a high-speed camera-based dynamic measurement system.The effects of operational parameters s...The size and distribution patterns of bubbles within a laboratory-scale coarse-particle flotation column were examined using a high-speed camera-based dynamic measurement system.The effects of operational parameters such as superficial water velocity,air-flow rate,and frother dosage on bubble-size and distribution characteristics were investigated.This study aims to provide theoretical support for enabling fluidized-bed flotation within coarse-particle flotation columns.The results show that negative pressure for air inspiratory and bubble formation is generated by passing a high-speed jet through a throat,and the greatest number of bubbles are observed under natural inspiratory state at an air-liquid ratio of 1:3-1:2.5.Increasing the air-flow rate transforms the bubble diameter distribution from a peaked distribution to a more uniform distribution.Furthermore,the frother narrows the range of bubble-size distribution.A positive correlation exists between the bubble Sauter diameter and air-flow rate,with the bubble Sauter diameter bearing a negative correlation with the superficial water velocity and frother concentration.展开更多
Sound speed is essential for leakage detection in liquid pipelines when using acoustic methods,which can be significantly influenced by gas bubbles generated from leakage.The propagation characteristics and mechanism ...Sound speed is essential for leakage detection in liquid pipelines when using acoustic methods,which can be significantly influenced by gas bubbles generated from leakage.The propagation characteristics and mechanism of acoustic waves in horizontal liquid pipelines containing gas bubbles are studied in detail in the present paper.The effect of sound wave frequency,bubble size and bubble distribution pattern on sound speed is studied through numerical simulations.The results show that the acoustic wave generated by leakage of liquid pipelines containing gas bubbles is a multi-frequency signal,and the energy of the signal is mainly concentrated within 200 Hz.In the low-frequency range,the propagation of sound waves has almost no dispersion in bubbly liquid.Sound speed at a certain void fraction is not constant,which is related to the bubble size and distribution pattern.The bubble size affects the gasliquid heat transfer equilibrium,during which sound speed is affected.For this reason,a thermodynamic correction factor is proposed,which enables the accuracy of the sound speed calculation to reach98.2%.What's more,sound speed increases non-linearly with the reduction of the bubble distribution space in the pipeline axial direction.This paper establishes a theoretical calculation model of sound speed based on the bubble distribution pattern in the pipeline axial direction,which is in good agreement with the numerical calculation results.The results of this paper provide the basis for applying acoustic leak detection technology in liquid pipelines containing gas bubbles.展开更多
We employ the Multi-Scale Log-Periodic Power Law Singularity Confidence Indicator(MS-LPPLS-CI)approach to identify positive and negative bubbles in the short-,medium,and long-term for the Indian stock market,using wee...We employ the Multi-Scale Log-Periodic Power Law Singularity Confidence Indicator(MS-LPPLS-CI)approach to identify positive and negative bubbles in the short-,medium,and long-term for the Indian stock market,using weekly data from November 2003 to December 2020.We use a nonparametric causality-in-quantiles approach to analyze the predictive impact of monetary policy shocks on bubble indicators.We find,in general,strong evidence of predictability across the entire conditional distribution for the two monetary policy shock factors,with stronger impacts for negative bubbles.Our findings have critical implications for the Reserve Bank of India,academics,and investors.展开更多
In this study, a water/silicone oil interface was used to simulate the steel/slag interface in a converter. A high-speed camera was used to record the entrainment process of droplets when air bubbles were passed throu...In this study, a water/silicone oil interface was used to simulate the steel/slag interface in a converter. A high-speed camera was used to record the entrainment process of droplets when air bubbles were passed through the water/silicone oil interface. Motion parameters of the bubbles and droplets were obtained using particle kinematic analysis software, and the entrainment rate of the droplets was calculated. It was found that the entrainment rate decreased from 29.5% to 0 when the viscosity of the silicone oil was increased from 60 mPa.s to 820 mPa.s in the case of bubbles with a 5 mm equivalent diameter passing through the water/silicone oil interface. The results indicate that in- creasing the viscosity of the silicone oil is conducive to reducing the entrainment rate. The entrainment rate increased from 0 to 136.3% in the case of silicone oil with a viscosity of 60 mPa.s when the equivalent diameter of the bubbles was increased from 3 mm to 7 ram. We there- fore conclude that small bubbles are also conductive to reducing the entrainment rate. The force analysis results for the water colmnn indicate that the entrainment rate of droplets is affected by the velocity of the bubble passing through the water/silicone oil interface and that the en- trainment rate decreases with the bubble velocity.展开更多
In order to understand the dominant factors of the physical properties of ice in ice thermodynamics and mechanics, in-situ observations of ice growth and decay processes were carried out. Two samplings were conducted ...In order to understand the dominant factors of the physical properties of ice in ice thermodynamics and mechanics, in-situ observations of ice growth and decay processes were carried out. Two samplings were conducted in the fast and steady ice growth stages. Ice pieces were used to observe ice crystals and gas bubbles in ice, and to measure the ice density. Vertical profiles of the type and size of ice crystals, shape and size of gas bubbles, and gas bubble content, as well as the ice density, were obtained. The results show that the upper layer of the ice pieces is granular ice and the lower layer is columnar ice; the average crystal size increases with the ice depth and remains steady in the fast and steady ice growth stages; the shape of gas bubbles in the upper layer of ice pieces is spherical with higher total content, and the shape in the middle and lower layers is cylinder with lower total content; the gas bubble size and content vary with the ice growth stage; and the ice density decreases with the increase of the gas bubble content.展开更多
The bubbles rise up and burst at the free surface is a complex two-phase process.A free energy lattice Boltzmann method(LBM)model is adopted in this paper to study this phenomenon.The interface capturing technique[Zhe...The bubbles rise up and burst at the free surface is a complex two-phase process.A free energy lattice Boltzmann method(LBM)model is adopted in this paper to study this phenomenon.The interface capturing technique[Zheng et al.,2006]is used to deal with the high density ratio problem.The Laplace law and the air-water interface capturing ability are validated for the multiphase model.The interaction between the single bubble or multiple bubbles and the free surface are studied by the multiphase model.The force acting on the bubble and the evolution of the free surface is studied.Meanwhile,effect of the initial distance between two adjacent bubbles on interaction effects of multiple bubbles is investigated as well.展开更多
Supercavitation in the diesel nozzle increases the instability of droplets in part due to the two-phase mixture, while the effect of cavitation bubbles on the instability of drops is still unclear. In order to investi...Supercavitation in the diesel nozzle increases the instability of droplets in part due to the two-phase mixture, while the effect of cavitation bubbles on the instability of drops is still unclear. In order to investigate the breakup of cavitation bubbles within the diesel droplet, a new mathematical model describing the disturbance growth rate of the diesel bubble instability is developed. The new mathematical model is applied to predict the effects of fluids viscosity on the stability of cavitation bubbles. The predicted values reveal that the comprehensive effect of fluids viscosity makes cavitation bubbles more stable. Compared with the viscosities of air and cavitation bubble, the diesel droplet＇s viscosity plays a dominant role on the stability of cavitation bubbles. Furthermore, based on the modified bubble breakup criterion, the effects of bubble growth speed, sound speed, droplet viscosity, droplet density, and bubble-droplet radius ratio on the breakup time and the breakup radius of cavitation bubbles are studied respectively. It is found that a bubble with large bubble-droplet radius ratio has the initial condition for breaking easily. For a given bubble-droplet radius ratio （0.2）, as the bubble growth speed increases （from 2 m/s to 60 m/s）, the bubble breakup time decreases（from 3.59 gs to 0.17 ps） rapidly. Both the greater diesel droplet viscosity and the greater diesel droplet density result in the increase of the breakup time. With increasing initial bubble-droplet radius ratio （from 0.2 to 0.8）, the bubble breakup radius decreases （from 8.86 trn to 6.23 tm）. There is a limited breakup radius for a bubble with a certain initial bubble-droplet radius ratio. The mathematical model and the modified bubble breakup criterion are helpful to improve the study on the breakup mechanism of the secondary diesel droplet under the condition of supercavitation.展开更多
Gas–liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rule...Gas–liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rules of bubbles, which influence the mass transfer efficiency to a large extent, have received much less attention. In this paper, the volume of fluid method was used to calculate the bubble shapes, pressure, velocity distributions,and the flow patterns inside the bubbles. The rising behavior of the bubbles with four different initial diameters,i.e., 3 mm, 5 mm, 7 mm and 9 mm was investigated in four various liquids including water, 61.23% glycerol,86.73% glycerol and 100% glycerol. The results show that the liquid properties and bubble initial diameters have great impacts on bubble shapes. Moreover, flow patterns inside the bubbles with different initial diameters were analyzed and classified into three types under the condition of different bubble shapes. Three correlations for predicting the maximum internal circulation inside the bubbles in 86.73% glycerol were presented and the R-square values were all bigger than 0.98. Through analyzing the pressure and velocity distributions around the bubbles, four rules of bubble deformation were also obtained to explain and predict the shapes.展开更多
Based on the modification of the radial pulsation equation of an individual bubble, an effective medium method （EMM） is presented for studying propagation of linear and nonlinear longitudinal acoustic waves in visco...Based on the modification of the radial pulsation equation of an individual bubble, an effective medium method （EMM） is presented for studying propagation of linear and nonlinear longitudinal acoustic waves in viscoelastic medium permeated with air bubbles. A classical theory developed previously by Gaunaurd （Gaunaurd GC and UEberall H, J. Acoust, Soc, Am., 1978; 63： 1699-1711） is employed to verify the EMM under linear approximation by comparing the dynamic （i.e. frequency-dependent） effective parameters, and an excellent agreement is obtained. The propagation of longitudinal waves is hereby studied in detail, The results illustrate that the nonlinear pulsation of bubbles serves as the source of second harmonic wave and the sound energy has the tendency to be transferred to second harmonic wave, Therefore the sound attenuation and acoustic nonlinearity of the viscoelastic matrix are remarkably enhanced due to the system＇s resonance induced by the existence of bubbles.展开更多
Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promot...Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.展开更多
Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano b...Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano bubble generation, a four-factor three-level Central Composite Design of Experimental was conducted for investigating four important design parameters of cavitation venturi tube governing the median size and the volume of pico and nano bubbles. The test results showed that maximum volume of pico and nano bubbles, 65–75%, and minimum mean pico and nano bubble size,150–240 nm, were achieved at the medium ratio of the diameter of outlet of the venturi-tube and diameter of throat(3–4), medium outlet angle(11–13°), high inlet angle(26–27°) and high ratio of the length of the throat and the diameter of throat(2.3–3). Study the effects of the producing pico and nano bubbles on fine coal flotation was performed in a 5 cm diameter 260 cm height flotation column. The optimal percentage of pico and nano bubbles was about 70%, which produced maximum combustible material recovery of 86% with clean coal ash content of 11.7%.展开更多
The entrapment behavior of Ar bubbles onto the solidifying front of molten steel in the continuous casting mold was investigated. The dynamic model of bubble and particle entrapment was developed in order to consider ...The entrapment behavior of Ar bubbles onto the solidifying front of molten steel in the continuous casting mold was investigated. The dynamic model of bubble and particle entrapment was developed in order to consider the effect of surface tension gradient induced forces(Marangoni force) due to the gradient of sulfur concentration and temperature. The numerical analysis and water model experiment were performed to apply the present model for various conditions. The calculation result is compared with experimental results and plant data in continuous casting mold as well. It shows that the thermal Marangoni force could play an important role and this model predicts the bubble behavior in the vicinity of solid/liquid interface more precisely.展开更多
The interaction of bubbles is the key to understand gas–liquid bubbling flow. Two-dimensional axis-symmetry computational fluid dynamics simulations on the interactive bubbles were performed with VOF method,which was...The interaction of bubbles is the key to understand gas–liquid bubbling flow. Two-dimensional axis-symmetry computational fluid dynamics simulations on the interactive bubbles were performed with VOF method,which was validated by experimental work. It is testified that several different bubble interactive behaviors could be acquired under different conditions. Firstly, for large bubbles(d: 4, 6, 8, 10 mm), the trailing bubble rising velocity and aspect ratio have negative correlations with liquid viscosity and surface tension. The influences of viscosity and surface tension on leading bubble are negligible. Secondly, for smaller bubbles(d: 1, 2 mm), the results are complicated. The two bubbles tend to move together due to the attractive force by the wake and the potential repulsive force. Especially for high viscous or high surface tension liquid, the bubble pairs undergo several times acceleration and deceleration. In addition, bubble deformation plays an important role during bubble interaction which cannot be neglected.展开更多
The 3D turbulence k-ε model flow of the steel melt （continuous phase） and the trajectories of individual gas bubbles （dispersed phase） in a continuous casting mold were simulated using an Eulerian-Lagrangian appr...The 3D turbulence k-ε model flow of the steel melt （continuous phase） and the trajectories of individual gas bubbles （dispersed phase） in a continuous casting mold were simulated using an Eulerian-Lagrangian approach. In order to investigate the effect of bubble size distribution, the radii of bubbles are set with an initial value of 0. 1- 2.5 mm which follows the normal distribution. The presented results indicate that, in the submerged entry nozzle （SEN）, the distribution of void fraction is only near the wall. Due to the fact that the bubbles motion is only limited to the wall, the deoxidization products have no access to contacting the wall, which prevents clogging. In the mold, the bubbles with a radius of 0. 25--2.5 mm will move to the top surface. Larger bubbles issuing out of the ports will attack the menis- cus and induce the fluid flows upwards in the top surface near the nozzle. It may induce mold powder entrapment into the mold. The bubbles with a radius of 0.1--0.25 mm will move to the zone near the narrow surface and the wide surface. These small bubbles will probably be trapped by the solidification front. Most of the bubbles moving to the narrow surface will flow with the ascending flow, while others will flow with the descending flow.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.52271319)the Jiangsu Funding Program for Excellent Postdoctoral Talent,and the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(Grant No.GZC20240618)the Natural Science Foundation of Jiangsu Province of China(BK20231525).
文摘In this study,the dynamic characteristics of microscale floating bubbles near the vertical wall are studied.This occurrence is common in industrial and natural phenomena.Although many studies have been conducted on microscale bubbles,few studies investigate floating bubbles with very small Reynolds number(Re)near the wall,which is the main research goal of this study.Therefore,this study establishes a model for the ascent of small-scale bubbles near a vertical wall using the interFoam solver in OpenFOAM.This study investigates the influences of diverse viscosity parameters,varying distances from the wall,and different gas flow rates on the terminal velocity,deformation,and motion trajectory of bubbles.The results reveal that as liquid viscosity increases,the Re of bubbles gradually decreases and reaches a minimum of 0.012,which is similar to the Re of micrometer-sized bubbles in water.The characteristics of the wall-induced force in the longitudinal direction are closely related to the changes in liquid viscosity.Under low-viscosity conditions,the induced lift is the principal form of action,whereas under high-viscosity conditions,it is primarily manifested as induced drag.
基金Funded by the National Natural Science Foundation of China(No.52172007)。
文摘To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.
基金financially supported by the National Natural Science Foundation of China(Nos.52274315 and 52374320)the Fundamental Research Funds for the Central Universities(Nos.FRF-TP-22-011A1 and FRF-DF22-16)。
文摘During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.
基金Supported by the National Natural Science Foundation of China(U21B2069,52274020,52288101,52274022)National Key Research and Development Program of China(2022YFC2806504)。
文摘The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurrent flow in annulus is carried out under different working conditions to reveal how the wellbore inclination angle,liquid phase property and countercurrent liquid velocity affect the bubble deformation and bubble migration trajectory/velocity,and to establish a bubble migration velocity prediction model.The bubbles in the countercurrent flow mainly migrate in two modes:free rising of isolated bubbles,and interactive rising of multiple bubbles.The bubbles migrate by an S-shaped trajectory in the countercurrent flow.With the increase of countercurrent liquid velocity,the lateral oscillation of bubbles is intensified.The increases of wellbore inclination angle,liquid density and liquid viscosity make the bubble migration trajectory gradually to be linear.The bubble is generally ellipsoidal during its rising.The wellbore inclination angle has little effect on the degree of bubble deformation.The bubbles are ellipsoidal during rising,with little influence of wellbore inclination angle on bubble deformation.With the increase of liquid viscosity and density,the aspect ratio of the bubble decreases.As the wellbore inclination angle increases,the bubble migration velocity gradually decreases.As the liquid viscosity increases,the bubble migration velocity decreases.As the liquid density increases,the bubble migration velocity increases slightly.The established bubble migration velocity prediction model yields errors within±15%,and demonstrates broad applicability across a wide range of operating conditions.
基金National Natural Science Foundation of China(12135008,12132005)。
文摘The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclear fuels containing pressurized FGBs,a mechanical constitutive model for the equivalent solid of FGBs was developed and validated.This model was based on the modified Van der Waals equation,incorporating the effects of surface tension.Using this model,the micromechanical fields in irradiated U-10Mo fuels with randomly distributed FGBs were calculated during uniaxial tensile testing via the finite element(FE)method.The macroscopic elastic constants of the irradiated U-10Mo fuels were then derived using homogenization theory,and the influences of bubble pressure,bubble size,and porosity on these constants were examined.Results show that adjacent FGBs exhibit mechanical interactions,which leads to distinct stress concentrations in the surrounding fuel skeleton.The macroscopic elastic constants of irradiated U-10Mo fuels decrease with increasing the macroscopic porosity,which can be quantitatively described by the Mori-Tanaka model.In contrast,bubble pressure and size have negligible effects on these constants.
基金supported by the National Key R&D Program of China(Grant No.2024YFC3013200)the Shenzhen Peacock Plan(Grant No.QD2023006C).
文摘Submarine pipelines are critical infrastructures for offshore energy transport and communications. Understanding their structural response to near-field explosions is crucial for enhancing their blast resistance and operational safety. This study presents a computational study on the interaction between explosion-induced bubbles and a seabed-mounted pipeline. A recently developed computational framework is employed, which couples a compressible fluid solver with a finite element structural solver via a partitioned procedure. An embedded boundary method and a level-set method are employed to handle the fluid-structure and gas-liquid interfaces. Using this framework, we analyze the flow field evolution, bubble dynamics, and transient pipe deformation. Two distinct response modes are identified: periodic oscillation under low-pressure loading and downward collapse triggered by high-pressure loading and bubble jet impact. Specifically, under high-pressure conditions, the pipe initially deforms inward, generating a localized high-pressure zone within the concave region. During structural rebound, the trapped fluid is expelled upward, giving rise to a bubble jet. Further parametric studies on the pipe's internal pressure, wall thickness, and support angle reveal several key insights. A higher internal pressure delays structural collapse, and a greater pipe thickness results in more uniform implosion morphologies. The support angle strongly influences the collapse dynamics, with the shortest collapse time occurring at 60 °. These findings offer new insights for the protective design of submarine pipelines.
基金supported by the National Key R&D Program of China(Nos.2023YFC3904202,2022YFC2904500)Major Science and Technology Program of Yunnan Province,China(No.202202AB080012).
文摘The size and distribution patterns of bubbles within a laboratory-scale coarse-particle flotation column were examined using a high-speed camera-based dynamic measurement system.The effects of operational parameters such as superficial water velocity,air-flow rate,and frother dosage on bubble-size and distribution characteristics were investigated.This study aims to provide theoretical support for enabling fluidized-bed flotation within coarse-particle flotation columns.The results show that negative pressure for air inspiratory and bubble formation is generated by passing a high-speed jet through a throat,and the greatest number of bubbles are observed under natural inspiratory state at an air-liquid ratio of 1:3-1:2.5.Increasing the air-flow rate transforms the bubble diameter distribution from a peaked distribution to a more uniform distribution.Furthermore,the frother narrows the range of bubble-size distribution.A positive correlation exists between the bubble Sauter diameter and air-flow rate,with the bubble Sauter diameter bearing a negative correlation with the superficial water velocity and frother concentration.
基金supported by the National Natural Science Foundation of China[grant number 52274066]。
文摘Sound speed is essential for leakage detection in liquid pipelines when using acoustic methods,which can be significantly influenced by gas bubbles generated from leakage.The propagation characteristics and mechanism of acoustic waves in horizontal liquid pipelines containing gas bubbles are studied in detail in the present paper.The effect of sound wave frequency,bubble size and bubble distribution pattern on sound speed is studied through numerical simulations.The results show that the acoustic wave generated by leakage of liquid pipelines containing gas bubbles is a multi-frequency signal,and the energy of the signal is mainly concentrated within 200 Hz.In the low-frequency range,the propagation of sound waves has almost no dispersion in bubbly liquid.Sound speed at a certain void fraction is not constant,which is related to the bubble size and distribution pattern.The bubble size affects the gasliquid heat transfer equilibrium,during which sound speed is affected.For this reason,a thermodynamic correction factor is proposed,which enables the accuracy of the sound speed calculation to reach98.2%.What's more,sound speed increases non-linearly with the reduction of the bubble distribution space in the pipeline axial direction.This paper establishes a theoretical calculation model of sound speed based on the bubble distribution pattern in the pipeline axial direction,which is in good agreement with the numerical calculation results.The results of this paper provide the basis for applying acoustic leak detection technology in liquid pipelines containing gas bubbles.
文摘We employ the Multi-Scale Log-Periodic Power Law Singularity Confidence Indicator(MS-LPPLS-CI)approach to identify positive and negative bubbles in the short-,medium,and long-term for the Indian stock market,using weekly data from November 2003 to December 2020.We use a nonparametric causality-in-quantiles approach to analyze the predictive impact of monetary policy shocks on bubble indicators.We find,in general,strong evidence of predictability across the entire conditional distribution for the two monetary policy shock factors,with stronger impacts for negative bubbles.Our findings have critical implications for the Reserve Bank of India,academics,and investors.
基金financially supported by the China Postdoctoral Science Foundation (Nos. 2015T80039 and 2014M560890)
文摘In this study, a water/silicone oil interface was used to simulate the steel/slag interface in a converter. A high-speed camera was used to record the entrainment process of droplets when air bubbles were passed through the water/silicone oil interface. Motion parameters of the bubbles and droplets were obtained using particle kinematic analysis software, and the entrainment rate of the droplets was calculated. It was found that the entrainment rate decreased from 29.5% to 0 when the viscosity of the silicone oil was increased from 60 mPa.s to 820 mPa.s in the case of bubbles with a 5 mm equivalent diameter passing through the water/silicone oil interface. The results indicate that in- creasing the viscosity of the silicone oil is conducive to reducing the entrainment rate. The entrainment rate increased from 0 to 136.3% in the case of silicone oil with a viscosity of 60 mPa.s when the equivalent diameter of the bubbles was increased from 3 mm to 7 ram. We there- fore conclude that small bubbles are also conductive to reducing the entrainment rate. The force analysis results for the water colmnn indicate that the entrainment rate of droplets is affected by the velocity of the bubble passing through the water/silicone oil interface and that the en- trainment rate decreases with the bubble velocity.
基金supported by the National Natural Science Foundation of China (Grant No.50879008)the Open Fund of State Key Laboratory of Frozen Soil Engineering (Grant No. SKLFSE200904)+1 种基金the Vilho,Yrj and Kalle Visl Fund of the Finnish Academy of Sciences and Lettersthe Norwegian Research Council Project AMORA (Grant No.193592/S30)
文摘In order to understand the dominant factors of the physical properties of ice in ice thermodynamics and mechanics, in-situ observations of ice growth and decay processes were carried out. Two samplings were conducted in the fast and steady ice growth stages. Ice pieces were used to observe ice crystals and gas bubbles in ice, and to measure the ice density. Vertical profiles of the type and size of ice crystals, shape and size of gas bubbles, and gas bubble content, as well as the ice density, were obtained. The results show that the upper layer of the ice pieces is granular ice and the lower layer is columnar ice; the average crystal size increases with the ice depth and remains steady in the fast and steady ice growth stages; the shape of gas bubbles in the upper layer of ice pieces is spherical with higher total content, and the shape in the middle and lower layers is cylinder with lower total content; the gas bubble size and content vary with the ice growth stage; and the ice density decreases with the increase of the gas bubble content.
基金supported by the National Natural Science Foundation of China (11672081)
文摘The bubbles rise up and burst at the free surface is a complex two-phase process.A free energy lattice Boltzmann method(LBM)model is adopted in this paper to study this phenomenon.The interface capturing technique[Zheng et al.,2006]is used to deal with the high density ratio problem.The Laplace law and the air-water interface capturing ability are validated for the multiphase model.The interaction between the single bubble or multiple bubbles and the free surface are studied by the multiphase model.The force acting on the bubble and the evolution of the free surface is studied.Meanwhile,effect of the initial distance between two adjacent bubbles on interaction effects of multiple bubbles is investigated as well.
基金supported by National Natural Science Foundation of China(Grant No.51276011)Beijing Municipal Natural Science Foundation of China(Grant No.3132016)+1 种基金National Hi-tech Research and Development Program of China(863 Program,Grant No.2013AA065303)Opening Foundation of State Key Laboratory of Engines of China(Grant No.K2013-3)
文摘Supercavitation in the diesel nozzle increases the instability of droplets in part due to the two-phase mixture, while the effect of cavitation bubbles on the instability of drops is still unclear. In order to investigate the breakup of cavitation bubbles within the diesel droplet, a new mathematical model describing the disturbance growth rate of the diesel bubble instability is developed. The new mathematical model is applied to predict the effects of fluids viscosity on the stability of cavitation bubbles. The predicted values reveal that the comprehensive effect of fluids viscosity makes cavitation bubbles more stable. Compared with the viscosities of air and cavitation bubble, the diesel droplet＇s viscosity plays a dominant role on the stability of cavitation bubbles. Furthermore, based on the modified bubble breakup criterion, the effects of bubble growth speed, sound speed, droplet viscosity, droplet density, and bubble-droplet radius ratio on the breakup time and the breakup radius of cavitation bubbles are studied respectively. It is found that a bubble with large bubble-droplet radius ratio has the initial condition for breaking easily. For a given bubble-droplet radius ratio （0.2）, as the bubble growth speed increases （from 2 m/s to 60 m/s）, the bubble breakup time decreases（from 3.59 gs to 0.17 ps） rapidly. Both the greater diesel droplet viscosity and the greater diesel droplet density result in the increase of the breakup time. With increasing initial bubble-droplet radius ratio （from 0.2 to 0.8）, the bubble breakup radius decreases （from 8.86 trn to 6.23 tm）. There is a limited breakup radius for a bubble with a certain initial bubble-droplet radius ratio. The mathematical model and the modified bubble breakup criterion are helpful to improve the study on the breakup mechanism of the secondary diesel droplet under the condition of supercavitation.
基金Supported by the National Natural Science Foundation of China(21276132)the Transformation Project of Scientific and Technological Achievements of Qingdao(16-6-2-50-nsh)
文摘Gas–liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rules of bubbles, which influence the mass transfer efficiency to a large extent, have received much less attention. In this paper, the volume of fluid method was used to calculate the bubble shapes, pressure, velocity distributions,and the flow patterns inside the bubbles. The rising behavior of the bubbles with four different initial diameters,i.e., 3 mm, 5 mm, 7 mm and 9 mm was investigated in four various liquids including water, 61.23% glycerol,86.73% glycerol and 100% glycerol. The results show that the liquid properties and bubble initial diameters have great impacts on bubble shapes. Moreover, flow patterns inside the bubbles with different initial diameters were analyzed and classified into three types under the condition of different bubble shapes. Three correlations for predicting the maximum internal circulation inside the bubbles in 86.73% glycerol were presented and the R-square values were all bigger than 0.98. Through analyzing the pressure and velocity distributions around the bubbles, four rules of bubble deformation were also obtained to explain and predict the shapes.
基金Project supported by the Excellent Youth Science Foundation of China （Grant No 10125417） and the State Key Development Program of Basic Research （Grant No 51315）,
文摘Based on the modification of the radial pulsation equation of an individual bubble, an effective medium method （EMM） is presented for studying propagation of linear and nonlinear longitudinal acoustic waves in viscoelastic medium permeated with air bubbles. A classical theory developed previously by Gaunaurd （Gaunaurd GC and UEberall H, J. Acoust, Soc, Am., 1978; 63： 1699-1711） is employed to verify the EMM under linear approximation by comparing the dynamic （i.e. frequency-dependent） effective parameters, and an excellent agreement is obtained. The propagation of longitudinal waves is hereby studied in detail, The results illustrate that the nonlinear pulsation of bubbles serves as the source of second harmonic wave and the sound energy has the tendency to be transferred to second harmonic wave, Therefore the sound attenuation and acoustic nonlinearity of the viscoelastic matrix are remarkably enhanced due to the system＇s resonance induced by the existence of bubbles.
基金The project is sponsored by the National Natural Science Foundation of China (No.50274007).
文摘Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.
基金West Virginia State Coal and Energy Research Bureau(WVCERB)the Department of Mining Engineering,West Virginia University
文摘Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano bubble generation, a four-factor three-level Central Composite Design of Experimental was conducted for investigating four important design parameters of cavitation venturi tube governing the median size and the volume of pico and nano bubbles. The test results showed that maximum volume of pico and nano bubbles, 65–75%, and minimum mean pico and nano bubble size,150–240 nm, were achieved at the medium ratio of the diameter of outlet of the venturi-tube and diameter of throat(3–4), medium outlet angle(11–13°), high inlet angle(26–27°) and high ratio of the length of the throat and the diameter of throat(2.3–3). Study the effects of the producing pico and nano bubbles on fine coal flotation was performed in a 5 cm diameter 260 cm height flotation column. The optimal percentage of pico and nano bubbles was about 70%, which produced maximum combustible material recovery of 86% with clean coal ash content of 11.7%.
文摘The entrapment behavior of Ar bubbles onto the solidifying front of molten steel in the continuous casting mold was investigated. The dynamic model of bubble and particle entrapment was developed in order to consider the effect of surface tension gradient induced forces(Marangoni force) due to the gradient of sulfur concentration and temperature. The numerical analysis and water model experiment were performed to apply the present model for various conditions. The calculation result is compared with experimental results and plant data in continuous casting mold as well. It shows that the thermal Marangoni force could play an important role and this model predicts the bubble behavior in the vicinity of solid/liquid interface more precisely.
基金Supported by the National Natural Science Foundation of China(91334105).
文摘The interaction of bubbles is the key to understand gas–liquid bubbling flow. Two-dimensional axis-symmetry computational fluid dynamics simulations on the interactive bubbles were performed with VOF method,which was validated by experimental work. It is testified that several different bubble interactive behaviors could be acquired under different conditions. Firstly, for large bubbles(d: 4, 6, 8, 10 mm), the trailing bubble rising velocity and aspect ratio have negative correlations with liquid viscosity and surface tension. The influences of viscosity and surface tension on leading bubble are negligible. Secondly, for smaller bubbles(d: 1, 2 mm), the results are complicated. The two bubbles tend to move together due to the attractive force by the wake and the potential repulsive force. Especially for high viscous or high surface tension liquid, the bubble pairs undergo several times acceleration and deceleration. In addition, bubble deformation plays an important role during bubble interaction which cannot be neglected.
基金Item Sponsored by National Natural Science Foundation of China(50874130,50974034)
文摘The 3D turbulence k-ε model flow of the steel melt （continuous phase） and the trajectories of individual gas bubbles （dispersed phase） in a continuous casting mold were simulated using an Eulerian-Lagrangian approach. In order to investigate the effect of bubble size distribution, the radii of bubbles are set with an initial value of 0. 1- 2.5 mm which follows the normal distribution. The presented results indicate that, in the submerged entry nozzle （SEN）, the distribution of void fraction is only near the wall. Due to the fact that the bubbles motion is only limited to the wall, the deoxidization products have no access to contacting the wall, which prevents clogging. In the mold, the bubbles with a radius of 0. 25--2.5 mm will move to the top surface. Larger bubbles issuing out of the ports will attack the menis- cus and induce the fluid flows upwards in the top surface near the nozzle. It may induce mold powder entrapment into the mold. The bubbles with a radius of 0.1--0.25 mm will move to the zone near the narrow surface and the wide surface. These small bubbles will probably be trapped by the solidification front. Most of the bubbles moving to the narrow surface will flow with the ascending flow, while others will flow with the descending flow.
