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Shripad T Revankar - One of the best experts on this subject based on the ideXlab platform.
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investigation of Bubble Breakup and coalescence in a packed bed reactor part 1 a comparative study of Bubble Breakup and coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of Bubble Breakup and coalescence models has been investigated to study Bubble size distributions as a function of the axial location. The Bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of Bubble Breakup and coalescence models is examined under two inlet flow conditions: (1) predominant Bubble Breakup flow and (2) predominant Bubble coalescence flow. The resulting Bubble size distributions, Breakup and coalescence rates estimated by individual models, are qualitatively compared to each other. The change of Bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing Bubble Breakup and coalescence models do not agree with the experimental data, a new Bubble Breakup and coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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Investigation of Bubble Breakup and coalescence in a packed-bed reactor – Part 1: A comparative study of Bubble Breakup and coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of Bubble Breakup and coalescence models has been investigated to study Bubble size distributions as a function of the axial location. The Bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of Bubble Breakup and coalescence models is examined under two inlet flow conditions: (1) predominant Bubble Breakup flow and (2) predominant Bubble coalescence flow. The resulting Bubble size distributions, Breakup and coalescence rates estimated by individual models, are qualitatively compared to each other. The change of Bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing Bubble Breakup and coalescence models do not agree with the experimental data, a new Bubble Breakup and coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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investigation of Bubble Breakup and coalescence in a packed bed reactor part 2 development of a new Bubble Breakup and coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of Bubble Breakup and coalescence has been developed for a packed bed. Bubble Breakup and coalescence models are developed for two coalescence and three Breakup mechanisms by taking account of geometry effects and local flow conditions. The Bubble size distribution estimated with the present Bubble Breakup and coalescence models are compared with the experimental data. Change of Bubble size distributions along the axial direction is studied with the median Bubble size. Median Bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) Bubble Breakup dominated flow and (2) Bubble coalescence dominated flow. The predictions of the median Bubble size with the present model result in the best among other existing Bubble Breakup and coalescence models. However, the prediction of the median Bubble size for the Bubble coalescence dominated flow is still significantly larger than the experimental data. Breakup and coalescence coefficients need to be adjusted in order to predict more accurate Bubble size distributions and median Bubble size for both flow conditions. For the Bubble Breakup dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.4, respectively. For the Bubble coalescence dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.01, respectively.
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Investigation of Bubble Breakup and coalescence in a packed-bed reactor – Part 2: Development of a new Bubble Breakup and coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of Bubble Breakup and coalescence has been developed for a packed bed. Bubble Breakup and coalescence models are developed for two coalescence and three Breakup mechanisms by taking account of geometry effects and local flow conditions. The Bubble size distribution estimated with the present Bubble Breakup and coalescence models are compared with the experimental data. Change of Bubble size distributions along the axial direction is studied with the median Bubble size. Median Bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) Bubble Breakup dominated flow and (2) Bubble coalescence dominated flow. The predictions of the median Bubble size with the present model result in the best among other existing Bubble Breakup and coalescence models. However, the prediction of the median Bubble size for the Bubble coalescence dominated flow is still significantly larger than the experimental data. Breakup and coalescence coefficients need to be adjusted in order to predict more accurate Bubble size distributions and median Bubble size for both flow conditions. For the Bubble Breakup dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.4, respectively. For the Bubble coalescence dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.01, respectively.
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Study of Bubbly Flow Through a Packed Bed
Volume 6: Fluids and Thermal Systems; Advances for Process Industries Parts A and B, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:A two phase bubbly flow through a packed bed was studied for dominant Bubble Breakup and coalescence mechanisms through experiments and CFD modeling. Data on various two-phase parameters, such as local void fraction, Bubble velocity, size, number, and shape were obtained from the high speed video images. Results indicated that when a flow regime changed from bubbly to either trickling or pulsing flow, the number of average size Bubbles significantly decreased and the shape of majority of Bubbles was no longer spherical. The Bubble coalescence and Breakup mechanisms depend on local conditions such as local velocity of the Bubble and pore geometry. The CFD analysis using CFX software package was carried out to study Bubble size distributions. In the analysis the models for interactions were examined for each case of Bubble Breakup flow and Bubble coalescence. A comparative study was performed on the resulting Bubble size distributions, Breakup and coalescence rates estimated by individual models. For change of Bubble size distributions along the axial direction medians was used as an comparative parameter and the CFD results on Bubble medians were compared against the experimental data. This comparative study showed that the predictions estimated by CFD analyses with the Bubble Breakup and coalescence models currently available in the literature do not agree with the experimental data.Copyright © 2011 by ASME
Tiefeng Wang - One of the best experts on this subject based on the ideXlab platform.
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an improved Bubble Breakup model in turbulent flow
Chemical Engineering Journal, 2019Co-Authors: Huahai Zhang, Guangyao Yang, Ali Sayyar, Tiefeng WangAbstract:Abstract An improved Bubble Breakup model has been developed by adequately describing the internal flow inside the deformed Bubble, to account for the significant effect of pressure on the Bubble Breakup behaviors and hydrodynamics in a Bubble column. In this new model, several significant conditions and experimental findings, such as static stress analysis, interfacial stress of Bubble neck, viscous flow resistance, were taken into account. These issues were not considered and led to under-predictions of the Bubble Breakup rate in our previous model. The Bubble Breakup rate and daughter Bubble size distribution predicted by this improved model were consistent with available experimental data. Moreover, this Bubble Breakup model was directly used in the CFD-PBM model to numerically simulate a Bubble column operated at different pressures. A good agreement between the simulated and experimental results was obtained under complex operating conditions.
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CFD-PBM simulations of a Bubble column with different liquid properties
Chemical Engineering Journal, 2017Co-Authors: Tiefeng Wang, Jinfu WangAbstract:Abstract The CFD-PBM coupled model was validated in a Bubble column with organic liquids under industrial conditions. Experimental data of the gas holdup, Bubble size distribution and mass transfer rate were collected from the literature. The liquid viscosity and surface tension were two important parameters affecting the hydrodynamics. Low liquid viscosity and surface tension enhanced the Bubble Breakup but hindered the Bubble coalescence. Compared with water, organic liquids led to a higher gas holdup, smaller Bubble size and larger mass transfer rate. The elevated temperature decreased the liquid viscosity and surface tension. The effects of temperature on the hydrodynamic and gas-liquid mass transfer behaviors were well predicted using the corresponding liquid properties. The CFD-PBM coupled model gave good predictions because it quantitatively described the effect of liquid properties on the Bubble size, interphase forces, turbulence parameters, and Bubble Breakup and coalescence behaviors. The simulations with different Bubble Breakup models showed that the accuracy of the Bubble Breakup model was crucial for reliable predictions of the CFD-PBM coupled model.
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A unified theoretical model for Breakup of Bubbles and droplets in turbulent flows
Aiche Journal, 2014Co-Authors: Chutian Xing, Tiefeng Wang, Jinfu WangAbstract:Pressure has a significant effect on Bubble Breakup, and Bubbles and droplets have very different Breakup behaviors. This work aimed to propose a unified Breakup model for both Bubbles and droplets including the effect of pressure. A mechanism analysis was made on the internal flow through the Bubble/droplet neck in the Breakup process, and a mathematical model was obtained based on the Young–Laplace and Bernoulli equations. The internal flow behavior strongly depended on the pressure or gas density, and based on this mechanism, a unified Breakup model was proposed for both Bubbles and droplets. For the first time, this unified Breakup model gave good predictions of both the effect of pressure or gas density on the Bubble Breakup rate and the different daughter size distributions of Bubbles and droplets. The effect of the mother Bubble/droplet diameter, turbulent energy dissipation rate and surface tension on the Breakup rate, and daughter Bubble/droplet size distribution was discussed. This Bubble Breakup model can be further used in a population balance model (PBM) to study the effect of pressure on the Bubble size distribution and in a computational fluid dynamics-population balance model (CFD-PBM) coupled model to study the hydrodynamic behaviors of a Bubble column at elevated pressures. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1391–1403, 2015
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Simulation of Bubble column reactors using CFD coupled with a population balance model
Frontiers of Chemical Engineering in China, 2010Co-Authors: Tiefeng WangAbstract:Bubble columns are widely used in chemical and biochemical processes due to their excellent mass and heat transfer characteristics and simple construction. However, their fundamental hydrodynamic behaviors, which are essential for reactor scale-up and design, are still not fully understood. To develop design tools for engineering purposes, much research has been carried out in the area of computational fluid dynamics (CFD) modeling and simulation of gas-liquid flows. Due to the importance of the Bubble behavior, the Bubble size distribution must be considered in the CFD models. The population balance model (PBM) is an effective approach to predict the Bubble size distribution, and great efforts have been made in recent years to couple the PBM into CFD simulations. This article gives a selective review of the modeling and simulation of Bubble column reactors using CFD coupled with PBM. Bubble Breakup and coalescence models due to different mechanisms are discussed. It is shown that the CFD-PBM coupled model with proper Bubble Breakup and coalescence models and interphase force formulations has the ability of predicting the complex hydrodynamics in different flow regimes and, thus, provides a unified description of both the homogeneous and heterogeneous regimes. Further study is needed to improve the models of Bubble coalescence and Breakup, turbulence modification in high gas holdup, and interphase forces of Bubble swarms.
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A CFD-PBM coupled model for gas-liquid flows
AIChE Journal, 2006Co-Authors: Tiefeng Wang, Jinfu Wang, Yong JinAbstract:A computational fluid dynamics-population balance model (CFD-PBM) coupled model was developed that combines the advantages of CFD to calculate the entire flow field and of the PBM to calculate the local Bubble size distribution. Bubble coalescence and Breakup were taken into account to determine the evolution of the Bubble size. Different Bubble Breakup and coalescence models were compared An algorithm was proposed for computing the parameters based on the Bubble size distribution, including the drag force, transverse lift force, wall lubrication force, turbulent dispersion force, and Bubble induced turbulence. With the Bubble Breakup and coalescence models and the interphase force formulations in this work, the CFD-PBM coupled model can give a unified description for both the homogeneous and the heterogeneous regimes. Good agreement was obtained with the experimental results for the gas holdup, liquid velocity, and Bubble size distribution. (c) 2005 American Institute of Chemical Engineers AIChE J, 52: 125-140, 2006.
Taotao Fu - One of the best experts on this subject based on the ideXlab platform.
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dynamics and interfacial evolution for Bubble Breakup in shear thinning non newtonian fluid in microfluidic t junction
Chemical Engineering Science, 2019Co-Authors: Hao Zhou, Taotao Fu, Huai Z LiAbstract:Abstract The dynamics and interfacial evolution for Bubble Breakup in shear-thinning non-Newtonian fluids in microfluidic T-junction were investigated. The Bubble Breakup process includes three stages: squeezing, transition and rapid pinch-off stages. The minimum widths of the Bubble neck in three stages exhibit a power-law relationship with the time or remaining time. Compared to Bubble Breakup in Newtonian fluid, the squeezing stage shortens in non-Newtonian fluid, and the power-law exponent of the rapid pinch-off stage increases with the decrease of the flow index of the CMC solutions. The length of the Bubble tip is linearly stretched with time, and the elongation rate increases with the concentration of CMC solution. The results show that the rheological property of the CMC solution could significantly affect the Bubble Breakup process in the microfluidic T-junction.
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critical condition for Bubble Breakup in a microfluidic flow focusing junction
Chemical Engineering Science, 2017Co-Authors: Xiaoda Wang, Taotao FuAbstract:Abstract The critical condition for Bubble Breakup in a microfluidic flow-focusing junction was studied in this work. The experiments were conducted in a square microchannel of 400 μm wide. The critical condition for Bubble Breakup was investigated by varying the Bubble length l 0 , liquid viscosity μ , velocity of the liquid from the main channel of the flow-focusing junction u 1, and velocity of the liquid from the side channels of the junction u 2 . By analyzing the effects of these factors on the dynamical evolution of gas-liquid interface for Bubble deformation and Breakup, expressions for describing the Bubble deformation and Breakup time were established, respectively. On the basis of these two expressions, the critical condition for the Bubble Breakup in a microfluidic flow-focusing junction was deduced: l 0 w c = 1.5 u 1 u 2 0.75 Ca 2 - 0.13 , where w c is the width of microchannel, Ca 2 = u 2 μ / γ , and γ is the surface tension.
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dynamics of Bubble Breakup at a t junction
Physical Review E, 2016Co-Authors: Yutao Lu, Taotao Fu, Huai Z LiAbstract:The gas-liquid interfacial dynamics of Bubble Breakup in a T junction was investigated. Four regimes were observed for a Bubble passing through the T junction. It was identified by the stop flow that a critical width of the Bubble neck existed: if the minimum width of the Bubble neck was less than the critical value, the Breakup was irreversible and fast; while if the minimum width of the Bubble neck was larger than the critical value, the Breakup was reversible and slow. The fast Breakup was driven by the surface tension and liquid inertia and is independent of the operating conditions. The minimum width of the Bubble neck could be scaled with the remaining time as a power law with an exponent of 0.22 in the beginning and of 0.5 approaching the final fast pinch-off. The slow Breakup was driven by the continuous phase and the gas-liquid interface was in the equilibrium stage. Before the appearance of the tunnel, the width of the depression region could be scaled with the time as a power law with an exponent of 0.75; while after that, the width of the depression was a logarithmic function with the time.
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dynamics of Bubble Breakup with partly obstruction in a microfluidic t junction
Chemical Engineering Science, 2015Co-Authors: Xiaoda Wang, Yining Wu, Taotao FuAbstract:Abstract The Bubble Breakup with partly obstruction in a microfluidic T-junction was investigated experimentally in this paper. It was demonstrated that the Breakup process could be divided into two stages: squeezing stage and pinch-off stage, according to the evolution of the minimum width of the Bubble neck w m . During the squeezing stage, the variation of 1− w m / w c with time t could be scaled by a power law. In the pinch-off stage, the minimum width of the Bubble neck w m could also be correlated into a power law function with the remaining time ( T c − t ). A tunnel, which characterized the Bubble Breakup with partly obstruction, appeared between the Bubble tip and the microchannel wall in the squeezing stage, and exhibited little effect on the evolution of the Bubble neck. However, the evolution of the Bubble tip was obviously different before and after tunnel appearance. By means of the analysis on the dynamics of the Bubble tip, some important parameters such as the final Bubble length and the leakage volume were studied and discussed.
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Bubble Breakup with permanent obstruction in an asymmetric microfluidic t junction
Aiche Journal, 2015Co-Authors: Xiaoda Wang, Taotao FuAbstract:Bubble Breakup with permanent obstruction in an asymmetric microfluidic T-junction is investigated experimentally. The Breakup process of Bubbles can be divided into three stages: squeezing, transition, and pinch-off stages. In the squeezing stage, the thinning of the Bubble neck is mainly controlled by the velocity of the fluid flowing into the T-junction, and the increase of the liquid viscosity can promote this process. In the transition stage, the minimum width of Bubble neck decreases linearly with time. In the pinch-off stage, the effect of the velocity of the fluid flowing into the T-junction on the thinning of the Bubble neck becomes weaker, and the increase of the liquid viscosity would delay this process. The evolution of the minimum width of the Bubble neck with the remaining time before the Breakup can be scaled by a power–law relationship. The Bubble length has little influence on the whole Breakup process of Bubbles. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1081–1091, 2015
Daeseong Jo - One of the best experts on this subject based on the ideXlab platform.
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investigation of Bubble Breakup and coalescence in a packed bed reactor part 1 a comparative study of Bubble Breakup and coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of Bubble Breakup and coalescence models has been investigated to study Bubble size distributions as a function of the axial location. The Bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of Bubble Breakup and coalescence models is examined under two inlet flow conditions: (1) predominant Bubble Breakup flow and (2) predominant Bubble coalescence flow. The resulting Bubble size distributions, Breakup and coalescence rates estimated by individual models, are qualitatively compared to each other. The change of Bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing Bubble Breakup and coalescence models do not agree with the experimental data, a new Bubble Breakup and coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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Investigation of Bubble Breakup and coalescence in a packed-bed reactor – Part 1: A comparative study of Bubble Breakup and coalescence models
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract In a packed-bed reactor a comparative study of Bubble Breakup and coalescence models has been investigated to study Bubble size distributions as a function of the axial location. The Bubble size distributions are obtained by solving population balance equations that describe gas–liquid interactions. Each combination of Bubble Breakup and coalescence models is examined under two inlet flow conditions: (1) predominant Bubble Breakup flow and (2) predominant Bubble coalescence flow. The resulting Bubble size distributions, Breakup and coalescence rates estimated by individual models, are qualitatively compared to each other. The change of Bubble size distributions along the axial direction is also described with medians. The medians resulting from CFD analyses are compared against the experimental data. Since the predictions estimated by CFD analyses with the existing Bubble Breakup and coalescence models do not agree with the experimental data, a new Bubble Breakup and coalescence model that takes account of the geometry effects is required to describe gas–liquid interactions in a packed-bed reactor.
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investigation of Bubble Breakup and coalescence in a packed bed reactor part 2 development of a new Bubble Breakup and coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of Bubble Breakup and coalescence has been developed for a packed bed. Bubble Breakup and coalescence models are developed for two coalescence and three Breakup mechanisms by taking account of geometry effects and local flow conditions. The Bubble size distribution estimated with the present Bubble Breakup and coalescence models are compared with the experimental data. Change of Bubble size distributions along the axial direction is studied with the median Bubble size. Median Bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) Bubble Breakup dominated flow and (2) Bubble coalescence dominated flow. The predictions of the median Bubble size with the present model result in the best among other existing Bubble Breakup and coalescence models. However, the prediction of the median Bubble size for the Bubble coalescence dominated flow is still significantly larger than the experimental data. Breakup and coalescence coefficients need to be adjusted in order to predict more accurate Bubble size distributions and median Bubble size for both flow conditions. For the Bubble Breakup dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.4, respectively. For the Bubble coalescence dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.01, respectively.
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Investigation of Bubble Breakup and coalescence in a packed-bed reactor – Part 2: Development of a new Bubble Breakup and coalescence model
International Journal of Multiphase Flow, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:Abstract A mechanistic model of Bubble Breakup and coalescence has been developed for a packed bed. Bubble Breakup and coalescence models are developed for two coalescence and three Breakup mechanisms by taking account of geometry effects and local flow conditions. The Bubble size distribution estimated with the present Bubble Breakup and coalescence models are compared with the experimental data. Change of Bubble size distributions along the axial direction is studied with the median Bubble size. Median Bubble size as a function of the axial location is estimated under two inlet flow conditions: (1) Bubble Breakup dominated flow and (2) Bubble coalescence dominated flow. The predictions of the median Bubble size with the present model result in the best among other existing Bubble Breakup and coalescence models. However, the prediction of the median Bubble size for the Bubble coalescence dominated flow is still significantly larger than the experimental data. Breakup and coalescence coefficients need to be adjusted in order to predict more accurate Bubble size distributions and median Bubble size for both flow conditions. For the Bubble Breakup dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.4, respectively. For the Bubble coalescence dominated flow, the Breakup and coalescence coefficients are found to be 0.35 and 0.01, respectively.
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Study of Bubbly Flow Through a Packed Bed
Volume 6: Fluids and Thermal Systems; Advances for Process Industries Parts A and B, 2011Co-Authors: Daeseong Jo, Shripad T RevankarAbstract:A two phase bubbly flow through a packed bed was studied for dominant Bubble Breakup and coalescence mechanisms through experiments and CFD modeling. Data on various two-phase parameters, such as local void fraction, Bubble velocity, size, number, and shape were obtained from the high speed video images. Results indicated that when a flow regime changed from bubbly to either trickling or pulsing flow, the number of average size Bubbles significantly decreased and the shape of majority of Bubbles was no longer spherical. The Bubble coalescence and Breakup mechanisms depend on local conditions such as local velocity of the Bubble and pore geometry. The CFD analysis using CFX software package was carried out to study Bubble size distributions. In the analysis the models for interactions were examined for each case of Bubble Breakup flow and Bubble coalescence. A comparative study was performed on the resulting Bubble size distributions, Breakup and coalescence rates estimated by individual models. For change of Bubble size distributions along the axial direction medians was used as an comparative parameter and the CFD results on Bubble medians were compared against the experimental data. This comparative study showed that the predictions estimated by CFD analyses with the Bubble Breakup and coalescence models currently available in the literature do not agree with the experimental data.Copyright © 2011 by ASME
Huai Z Li - One of the best experts on this subject based on the ideXlab platform.
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dynamics and interfacial evolution for Bubble Breakup in shear thinning non newtonian fluid in microfluidic t junction
Chemical Engineering Science, 2019Co-Authors: Hao Zhou, Taotao Fu, Huai Z LiAbstract:Abstract The dynamics and interfacial evolution for Bubble Breakup in shear-thinning non-Newtonian fluids in microfluidic T-junction were investigated. The Bubble Breakup process includes three stages: squeezing, transition and rapid pinch-off stages. The minimum widths of the Bubble neck in three stages exhibit a power-law relationship with the time or remaining time. Compared to Bubble Breakup in Newtonian fluid, the squeezing stage shortens in non-Newtonian fluid, and the power-law exponent of the rapid pinch-off stage increases with the decrease of the flow index of the CMC solutions. The length of the Bubble tip is linearly stretched with time, and the elongation rate increases with the concentration of CMC solution. The results show that the rheological property of the CMC solution could significantly affect the Bubble Breakup process in the microfluidic T-junction.
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dynamics of Bubble Breakup at a t junction
Physical Review E, 2016Co-Authors: Yutao Lu, Taotao Fu, Huai Z LiAbstract:The gas-liquid interfacial dynamics of Bubble Breakup in a T junction was investigated. Four regimes were observed for a Bubble passing through the T junction. It was identified by the stop flow that a critical width of the Bubble neck existed: if the minimum width of the Bubble neck was less than the critical value, the Breakup was irreversible and fast; while if the minimum width of the Bubble neck was larger than the critical value, the Breakup was reversible and slow. The fast Breakup was driven by the surface tension and liquid inertia and is independent of the operating conditions. The minimum width of the Bubble neck could be scaled with the remaining time as a power law with an exponent of 0.22 in the beginning and of 0.5 approaching the final fast pinch-off. The slow Breakup was driven by the continuous phase and the gas-liquid interface was in the equilibrium stage. Before the appearance of the tunnel, the width of the depression region could be scaled with the time as a power law with an exponent of 0.75; while after that, the width of the depression was a logarithmic function with the time.
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hydrodynamic feedback on Bubble Breakup at a t junction within an asymmetric loop
Aiche Journal, 2014Co-Authors: Taotao Fu, Huai Z LiAbstract:Bubble Breakup at a microfluidic T-junction by taking into consideration the hydrodynamic feedback at the downstream channels is presented. Experiments are conducted in square microchannels with 400 μm in width. The splitting ratio of the Bubble size in the bifurcations varies nonmonotonically with the flow rate ratio of gas/liquid phases, and it is also affected by the liquid viscosity. A critical size of the mother Bubble determines the variation trend of the splitting ratio of Bubble size with flow rates of both phases and the liquid viscosity, which is related to the different Breakup mechanisms for long and short Bubbles at the junction and the different additional resistances induced by long and short Bubbles in downstream channels. A theoretical model is proposed to predict the tailoring size of Bubbles at the T-junction by taking into account of the additional resistance in the presence of Bubbles in downstream channels. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1920–1929, 2014
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Hydrodynamic feedback on Bubble Breakup at a T‐junction within an asymmetric loop
Aiche Journal, 2014Co-Authors: Taotao Fu, Youguang Ma, Huai Z LiAbstract:Bubble Breakup at a microfluidic T-junction by taking into consideration the hydrodynamic feedback at the downstream channels is presented. Experiments are conducted in square microchannels with 400 μm in width. The splitting ratio of the Bubble size in the bifurcations varies nonmonotonically with the flow rate ratio of gas/liquid phases, and it is also affected by the liquid viscosity. A critical size of the mother Bubble determines the variation trend of the splitting ratio of Bubble size with flow rates of both phases and the liquid viscosity, which is related to the different Breakup mechanisms for long and short Bubbles at the junction and the different additional resistances induced by long and short Bubbles in downstream channels. A theoretical model is proposed to predict the tailoring size of Bubbles at the T-junction by taking into account of the additional resistance in the presence of Bubbles in downstream channels. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1920–1929, 2014
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Breakup dynamics of slender Bubbles in non‐newtonian fluids in microfluidic flow‐focusing devices
Aiche Journal, 2012Co-Authors: Taotao Fu, Denis Funfschilling, Youguang Ma, Huai Z LiAbstract:This study aims to investigate the Breakup of slender Bubbles in non-Newtonian fluids in microfluidic flow-focusing devices using a high-speed camera and a microparticle image velocimetry (micro-PIV) system. Experiments were conducted in 400- and 600-μm square microchannels. The variation of the minimum width of gaseous thread with the remaining time before pinch-off could be scaled as a power-law relationship with an exponent less than 1/3, obtained for the pinch-off of Bubbles in Newtonian fluids. The velocity field and spatial viscosity distribution in the liquid phase around the gaseous thread were determined by micro-PIV to understand the Bubble Breakup mechanism. A scaling law was proposed to describe the size of Bubbles generated in these non-Newtonian fluids at microscale. The results revealed that the rheological properties of the continuous phase affect significantly the Bubble Breakup in such microdevices. © 2012 American Institute of Chemical Engineers AIChE J,, 2012
