In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,whi...In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.展开更多
An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer. The experimental tube is 0.018 m I...An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer. The experimental tube is 0.018 m ID and 1.0m in length. The range of the inclination angle is 45°-9° from the horizontal. The experiment focused on the effect of the inclination angle show that the mean liquid slug length and Taylor bubble length increase with the increasing xlD at various inclination angles. At the same x/D, the mean liquid slug length and Taylor bubble length increase first, and then decrease with decreasing inclination angles, with the maximum at 60°. In the vertical tube, standard deviation of the nitrogen Taylor bubble iength increase with the increasing xlD. For the inclined tube, standard deviation of the nitrogen Taylor bubble length increases first, and then decreases with the increasing x/D. Standard deviation of the liquid slug length increases with increasing x/D for all inclination angles.展开更多
An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital camera.The tubes in the experiment are 0.01...An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital camera.The tubes in the experiment are 0.018 m and 0.014 m in inner diameter and 1.0 m in length.The range of the inclination angles is 0-45° from the vertical.The statistical method is employed to analyze the experimental data.The experiment was focused on the effect of the inclination angle on the initial position distribution of Taylor bubbles.The formation criterion of Taylor bubbles was confirmed by analyzing the images of Taylor bubbles.The experimental results show that the initial position of Taylor bubble increased first,and then decreased with the increasing inclination angle,with the maximum at 30°.The standard deviation of the initial position of Taylor bubble in tubes was different with different inner diameters.The lognormal shape was fitted to the measured the initial position distributions of Taylor bubbles in the cryogenic tubes.展开更多
The hydrodynamic study of the liquid film around Taylor bubbles in slug flow has great significance for understanding parallel flow and interaction between Taylor bubbles.The prediction models for liquid film thicknes...The hydrodynamic study of the liquid film around Taylor bubbles in slug flow has great significance for understanding parallel flow and interaction between Taylor bubbles.The prediction models for liquid film thickness mainly focus on stagnant flow,and some of them remain inaccurate performance.However,in the industrial process,the slug flow essentially is co-current flow.Therefore,in this paper,the liquid film thickness is studied by theoretical analysis and experimental methods under two conditions of stagnant and co-current flow.Firstly,under the condition of stagnant flow,the present work is based on Batchelor's theory,and modifies Batchelor's liquid film thickness model,which effectively improves its prediction accuracy.Under the condition of co-current flow,the prediction model of average liquid film thickness in slug flow is established by force and motion analysis.Taylor bubble length is introduced into the model as an important parameter.Dynamic experiments were carried out in the pipe with an inner diameter of 20 mm.The liquid film thickness,Taylor bubble velocity and length were measured by distributed ultrasonic sensor and intrusive cross-correlation conductivity sensor.Comparing the predicted value of the model with the measured results,the relative error is controlled within 10%.展开更多
Wall-liquid mass transfer for Taylor bubbles rising through liquid column in vertical tubes is an important and fundamental topic in industrial processes.In this work,the characteristics of wall-liquid mass transfer f...Wall-liquid mass transfer for Taylor bubbles rising through liquid column in vertical tubes is an important and fundamental topic in industrial processes.In this work,the characteristics of wall-liquid mass transfer for this special case of slug flow were studied experimentally by limiting diffusion current technique (LDCT). Based on the experimental results and the analysis of hydrodynamic mechanisms,it was proposed that four different zones exist,i.e.the laminar falling film zone,the turbulent falling film zone,the wake region and the remaining liquid slug zone.The corresponding correlations for all these zones were developed.展开更多
This article studies rising velocity of Taylor bubbles and liquid slugs in liquid nitrogen at different axial positions in upward inclined tubes by means of a high speed motion analyzer. The bottom-closed tubes in the...This article studies rising velocity of Taylor bubbles and liquid slugs in liquid nitrogen at different axial positions in upward inclined tubes by means of a high speed motion analyzer. The bottom-closed tubes in the experiments are 1.0 m long with an inner diameter of 0.014 m or 0.018 m. The tube inclines upward from 0~ to 50~ with respect to the normal. Statistical method is used to analyze the data of the Taylor bubble and the liquid slug velocity. Reflecting the effects of the inclination angle on the rising velocity of Taylor bubbles and liquid slugs, the experimental results indicate the similar trend the Taylor bubble velocity and the liquid slug velocity have： it increases first, and then decreases with the increase of the inclination angle. Moreover, with the increase of the inclination angle, the liquid slug velocity becomes greater than Taylor bubble velocity.展开更多
The motion of the Taylor bubbles in vertical and near-vertical tubes wasinvestigated. The non-invasive measurements were conducted by using a high-speed motion analyzer.For the vertical slug flow, the coefficient C_1 ...The motion of the Taylor bubbles in vertical and near-vertical tubes wasinvestigated. The non-invasive measurements were conducted by using a high-speed motion analyzer.For the vertical slug flow, the coefficient C_1 was found to be very close to the ratio of themaximum velocity to the average velocity in the profile. For the inclined slug flow, the value ofC_1 is smaller than that for the vbertical case because the nose tip of the Taylor bubble usuallydeviates from the centerline. The drift velocity is increased with the decrease of inclinationangle. Based on the theoretical analysis and experimental data, the bubble velocity correlationswere obtained. The results are in good agreement with the available data.展开更多
Large vertical pipes are key structures connecting subsea wells to offshore platforms.However,existing studies mainly focus on small vertical pipes.In a vertical acrylic pipe with 80 mm inner diameter and 11 m height,...Large vertical pipes are key structures connecting subsea wells to offshore platforms.However,existing studies mainly focus on small vertical pipes.In a vertical acrylic pipe with 80 mm inner diameter and 11 m height,a high-speed camera was used to visually research the influences of pipe diameters,liquid properties and inlet effect on air-water co-flow characteristic.Different flow regime maps of vertical pipes(diameters are in the range of 50e189 mm)were compared and the critical gas velocity of the transition boundary from bubble to slug flow tended to increase with the increase of diameters at D≥80 mm.Drift-flux models were established in different flow regimes and liquid properties have a significant effect on drift coefficients of bubble flow and slug flow(void fraction a≤0.4).The influence of inlet turbulent effect on the gas-liquid interface distribution gradually weakened and disappeared from the pipe base to 85D,where the flow was fully developed.Slug frequency has a trend of increase first and then decrease with the gas Weber numbers increasing at low liquid superficial velocities(J_(L)≤0.31 m/s).And on the basis of this law,a new slug frequency correlation was proposed.It was found that there was an exponential relationship between the ratio of lengths of Taylor bubble to slug and the void fraction.展开更多
One of the crucial aspects of reducing air consumption when conveying particles with an airlift pump is to know the factors that affect the process of particle motion at an initial velocity of zero.To determine the in...One of the crucial aspects of reducing air consumption when conveying particles with an airlift pump is to know the factors that affect the process of particle motion at an initial velocity of zero.To determine the influence of submer-gence ratio and physical properties of particles(such as size,shape,and mass)on the onset of vertical particle motion,the airlift pump was taken as the research object,and spherical glass together with irregular shaped coal were used as experimental test particles.The results show that unlike the water-solid environment,the start of particle motion in the water-air mixture does not always occur at a certain value of superficial water velocity and this value also increases with increasing submergence level.Among the parameters considered,the role of submergence ratio is much more effective than the dimensions and the shape of the particle,because by increasing submergence from 0.3 to 0.8,it is possible to reduce air consumption by up to 8 times.Based on this study the corresponding theoretical model derived by Fujimoto et al.is optimized,wherein the overall agreement between the modified theory and present experimental data is particularly good.Contrary to Fujimoto,the minimum superficial water velocity for lifting solids in the air-water mixture is not always smaller than water ambient which indicates on optimum submergence ratio higher than 0.7.Finally,a new criterion was introduced to describe the moment of onset of the particle motion as a function of the superficial fluid velocity ratio for each submergence value.展开更多
It has been reported in recent experimental and numerical studies that the forced gas-liquid displacement in a partially wettable capillary tube can give rise to entrainment of a liquid film and generation of Taylor b...It has been reported in recent experimental and numerical studies that the forced gas-liquid displacement in a partially wettable capillary tube can give rise to entrainment of a liquid film and generation of Taylor bubbles at a large displacement rate.However,simulations and hydrodynamic theory of Gao et al.(J.Fluid Meeh.,2019,vol 859:308-320)predicted an abrupt drop of the contact line velocity Ca_(cl)at the onset of wetting transition,which conflicted with the experiments of Zhao et al.(Phys.Rev.Lett.,2018,vol 120:084501),who suggested a continuous variation of Ca_(cl).To resolve this discrepancy,we performed experiments of gas-liquid displacement,focusing on the contact line velocity close to the threshold.It is found that Ca_(cl) is indeed discontinuous,confirming the validity of the hydrodynamic description of the moving contact line.After an abrupt drop,Ca_(cl)increases to a constant for a slight raise of the displacement rate.The failure of detecting this discontinuity in previous experiments is due to the low resolution of the displacement rate.The propagating velocity and the length of the generated bubbles are presented and agree well with the existing theory.Variation of the liquid slug length with the displacement rate is also presented.展开更多
The slug length and the trailing Taylor bubble velocity in an upward vertical slug flow were measured by using the optical probes and the EKTAPRO 1000 high speed motion analyzer. The correlation between the trailing b...The slug length and the trailing Taylor bubble velocity in an upward vertical slug flow were measured by using the optical probes and the EKTAPRO 1000 high speed motion analyzer. The correlation between the trailing bubble velocity and the length of liquid slug ahead of that bubble is derived from the experimental data. Based on this correlation as well as the bubble overtaking mechanism, a model for the slug length distribution at any designated locations along the pipe is proposed. The predicted results are in agreement with the experimental data.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12202441).
文摘In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.
基金Supported by the National Natural Science Foundation of China （50476015） and National High Technology Research and Development Program of China （2006AA09Z333）.
文摘An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer. The experimental tube is 0.018 m ID and 1.0m in length. The range of the inclination angle is 45°-9° from the horizontal. The experiment focused on the effect of the inclination angle show that the mean liquid slug length and Taylor bubble length increase with the increasing xlD at various inclination angles. At the same x/D, the mean liquid slug length and Taylor bubble length increase first, and then decrease with decreasing inclination angles, with the maximum at 60°. In the vertical tube, standard deviation of the nitrogen Taylor bubble iength increase with the increasing xlD. For the inclined tube, standard deviation of the nitrogen Taylor bubble length increases first, and then decreases with the increasing x/D. Standard deviation of the liquid slug length increases with increasing x/D for all inclination angles.
基金Supported by the National Natural Science Foundation of China （50476015） and National High-Yech Research and Develop ment Program of China （2006AA09Z333）.
文摘An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital camera.The tubes in the experiment are 0.018 m and 0.014 m in inner diameter and 1.0 m in length.The range of the inclination angles is 0-45° from the vertical.The statistical method is employed to analyze the experimental data.The experiment was focused on the effect of the inclination angle on the initial position distribution of Taylor bubbles.The formation criterion of Taylor bubbles was confirmed by analyzing the images of Taylor bubbles.The experimental results show that the initial position of Taylor bubble increased first,and then decreased with the increasing inclination angle,with the maximum at 30°.The standard deviation of the initial position of Taylor bubble in tubes was different with different inner diameters.The lognormal shape was fitted to the measured the initial position distributions of Taylor bubbles in the cryogenic tubes.
基金supported by National Natural Science Foundation of China(42074142,51527805)。
文摘The hydrodynamic study of the liquid film around Taylor bubbles in slug flow has great significance for understanding parallel flow and interaction between Taylor bubbles.The prediction models for liquid film thickness mainly focus on stagnant flow,and some of them remain inaccurate performance.However,in the industrial process,the slug flow essentially is co-current flow.Therefore,in this paper,the liquid film thickness is studied by theoretical analysis and experimental methods under two conditions of stagnant and co-current flow.Firstly,under the condition of stagnant flow,the present work is based on Batchelor's theory,and modifies Batchelor's liquid film thickness model,which effectively improves its prediction accuracy.Under the condition of co-current flow,the prediction model of average liquid film thickness in slug flow is established by force and motion analysis.Taylor bubble length is introduced into the model as an important parameter.Dynamic experiments were carried out in the pipe with an inner diameter of 20 mm.The liquid film thickness,Taylor bubble velocity and length were measured by distributed ultrasonic sensor and intrusive cross-correlation conductivity sensor.Comparing the predicted value of the model with the measured results,the relative error is controlled within 10%.
文摘Wall-liquid mass transfer for Taylor bubbles rising through liquid column in vertical tubes is an important and fundamental topic in industrial processes.In this work,the characteristics of wall-liquid mass transfer for this special case of slug flow were studied experimentally by limiting diffusion current technique (LDCT). Based on the experimental results and the analysis of hydrodynamic mechanisms,it was proposed that four different zones exist,i.e.the laminar falling film zone,the turbulent falling film zone,the wake region and the remaining liquid slug zone.The corresponding correlations for all these zones were developed.
基金National Natural Science Foundation of China (50476015)
文摘This article studies rising velocity of Taylor bubbles and liquid slugs in liquid nitrogen at different axial positions in upward inclined tubes by means of a high speed motion analyzer. The bottom-closed tubes in the experiments are 1.0 m long with an inner diameter of 0.014 m or 0.018 m. The tube inclines upward from 0~ to 50~ with respect to the normal. Statistical method is used to analyze the data of the Taylor bubble and the liquid slug velocity. Reflecting the effects of the inclination angle on the rising velocity of Taylor bubbles and liquid slugs, the experimental results indicate the similar trend the Taylor bubble velocity and the liquid slug velocity have： it increases first, and then decreases with the increase of the inclination angle. Moreover, with the increase of the inclination angle, the liquid slug velocity becomes greater than Taylor bubble velocity.
基金ThisworkwassupportedbyBeijingScienceandTechnologyCommission (GrantNo :95 4 810 80 0 )andSRFforRocs SEM .
文摘The motion of the Taylor bubbles in vertical and near-vertical tubes wasinvestigated. The non-invasive measurements were conducted by using a high-speed motion analyzer.For the vertical slug flow, the coefficient C_1 was found to be very close to the ratio of themaximum velocity to the average velocity in the profile. For the inclined slug flow, the value ofC_1 is smaller than that for the vbertical case because the nose tip of the Taylor bubble usuallydeviates from the centerline. The drift velocity is increased with the decrease of inclinationangle. Based on the theoretical analysis and experimental data, the bubble velocity correlationswere obtained. The results are in good agreement with the available data.
基金supported by the National Natural Science Foundation of China(No.51888103,No.52076175).
文摘Large vertical pipes are key structures connecting subsea wells to offshore platforms.However,existing studies mainly focus on small vertical pipes.In a vertical acrylic pipe with 80 mm inner diameter and 11 m height,a high-speed camera was used to visually research the influences of pipe diameters,liquid properties and inlet effect on air-water co-flow characteristic.Different flow regime maps of vertical pipes(diameters are in the range of 50e189 mm)were compared and the critical gas velocity of the transition boundary from bubble to slug flow tended to increase with the increase of diameters at D≥80 mm.Drift-flux models were established in different flow regimes and liquid properties have a significant effect on drift coefficients of bubble flow and slug flow(void fraction a≤0.4).The influence of inlet turbulent effect on the gas-liquid interface distribution gradually weakened and disappeared from the pipe base to 85D,where the flow was fully developed.Slug frequency has a trend of increase first and then decrease with the gas Weber numbers increasing at low liquid superficial velocities(J_(L)≤0.31 m/s).And on the basis of this law,a new slug frequency correlation was proposed.It was found that there was an exponential relationship between the ratio of lengths of Taylor bubble to slug and the void fraction.
基金supported by the European Research Council (Research Fund for Coal and Steel)under Grant Agreement number 800757.
文摘One of the crucial aspects of reducing air consumption when conveying particles with an airlift pump is to know the factors that affect the process of particle motion at an initial velocity of zero.To determine the influence of submer-gence ratio and physical properties of particles(such as size,shape,and mass)on the onset of vertical particle motion,the airlift pump was taken as the research object,and spherical glass together with irregular shaped coal were used as experimental test particles.The results show that unlike the water-solid environment,the start of particle motion in the water-air mixture does not always occur at a certain value of superficial water velocity and this value also increases with increasing submergence level.Among the parameters considered,the role of submergence ratio is much more effective than the dimensions and the shape of the particle,because by increasing submergence from 0.3 to 0.8,it is possible to reduce air consumption by up to 8 times.Based on this study the corresponding theoretical model derived by Fujimoto et al.is optimized,wherein the overall agreement between the modified theory and present experimental data is particularly good.Contrary to Fujimoto,the minimum superficial water velocity for lifting solids in the air-water mixture is not always smaller than water ambient which indicates on optimum submergence ratio higher than 0.7.Finally,a new criterion was introduced to describe the moment of onset of the particle motion as a function of the superficial fluid velocity ratio for each submergence value.
基金the National Natural Science Foundation of China(Grant Nos.11972340,11672287,11932019,and 11621202)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB22040103)the Fundamental Research Funds for the Central Universities.
文摘It has been reported in recent experimental and numerical studies that the forced gas-liquid displacement in a partially wettable capillary tube can give rise to entrainment of a liquid film and generation of Taylor bubbles at a large displacement rate.However,simulations and hydrodynamic theory of Gao et al.(J.Fluid Meeh.,2019,vol 859:308-320)predicted an abrupt drop of the contact line velocity Ca_(cl)at the onset of wetting transition,which conflicted with the experiments of Zhao et al.(Phys.Rev.Lett.,2018,vol 120:084501),who suggested a continuous variation of Ca_(cl).To resolve this discrepancy,we performed experiments of gas-liquid displacement,focusing on the contact line velocity close to the threshold.It is found that Ca_(cl) is indeed discontinuous,confirming the validity of the hydrodynamic description of the moving contact line.After an abrupt drop,Ca_(cl)increases to a constant for a slight raise of the displacement rate.The failure of detecting this discontinuity in previous experiments is due to the low resolution of the displacement rate.The propagating velocity and the length of the generated bubbles are presented and agree well with the existing theory.Variation of the liquid slug length with the displacement rate is also presented.
基金supported by the National Natural Science Foundation of China (Grant No. 50876003)the Science and Technology Development Project of Beijing Education Committee (Grant No. KZ200710005001)the Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality (Grant No. PHR200906104)
文摘The slug length and the trailing Taylor bubble velocity in an upward vertical slug flow were measured by using the optical probes and the EKTAPRO 1000 high speed motion analyzer. The correlation between the trailing bubble velocity and the length of liquid slug ahead of that bubble is derived from the experimental data. Based on this correlation as well as the bubble overtaking mechanism, a model for the slug length distribution at any designated locations along the pipe is proposed. The predicted results are in agreement with the experimental data.
