INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
·
2019
·
IF 2.829
Xin Huang,Limin He,Xiaoming Luo,Haoran Yin,Donghai Yang
Deformation and coalescence behaviors of water droplets in viscous fluid under a direct current electric field are investigated with experiments and numerical simulations. An electro-hydrodynamic model is developed based on fluid dynamics equations and electrostatic equations. A coupled level set and volume of fluid method is proposed to capture the dynamic interface. The numerical results are validated to be in good accordance with classic results in the literature. The effects of electric capillary number Ca and viscosity ratio λ on droplet deformation and coalescence are systematically analyzed. Two different droplet response modes are obtained, namely overdamping response and underdamping response. The conversion of response modes is discussed with the ( Ca, λ ) phase diagram. Moreover, the distributions of electric field and flow field before and after the droplets contact are compared and analyzed. Numerical results show the time evolution of liquid bridge is dominated by the interfacial tension and viscosity of continuous phase. The electric stress is extremely weak at the liquid bridge and has a slight influence on evolution of liquid bridge. The correlation formula between dimensionless liquid bridge radius and conical angle during the growth of liquid bridge is regressed. These results are helpful for the optimization of electro-coalescence process.
研究领域:
流体力学
·
电动力学
✓ 已验证
产品关联
DOI
高影响因子
AICHE JOURNAL
·
2021
·Vol. 67
·期 5
·e17165
·
IF 3.993
Xin Huang,Limin He,Xiaoming Luo,Ke Xu,Yuling Lü,Donghai Yang
The dynamic behaviors of two droplets and droplet cluster under an alternating current (AC) electric field are investigated. Two droplets generally undergo transformation from complete coalescence to partial coalescence and finally to non-coalescence as the electric capillary number Ca p increases. The critical electric capillary number Ca pc for complete coalescence in the AC electric field remains unchanged and is twice as large as that in the direct current (DC) electric field when the frequency f ≥ 250 Hz. Charge transfer and reversal of electric field result in the reversal of the direction of electric force, which is the fundamental mechanism of non-coalescence of two droplets and chain formation in droplet cluster. The number of rebounds dramatically increases as f increases, promoting the stability of droplet chain. The droplet chains in the high-frequency AC electric field are longer and more stable than those in the low-frequency AC electric field.
研究领域:
流体力学
·
电动力学
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF CHEMICAL ENGINEERING
·
2022
·
IF 3.898
Yanyan Liu,Chaoqun Yao,Guangwen Chen
Gas–liquid–liquid three-phase slug flow was generated in both hydrophilic and hydrophobic microreactors with double T-junctions. The bubble-droplet relative movement and the local mass transfer within the continuous slug and the dispersed droplet were investigated. It was found that bubbles moved faster than droplets under low capillary number ( Ca ), while droplets moved faster upon the increase of Ca due to the increased inertia. For the first time, we observed that the increased viscosity of droplets fastened the droplet movement. The mass transfer in the continuous slug was dominated by convection, leading to nearly constant global mass transfer coefficient ( k L a ); while that in the dispersed droplet was dominated by diffusion, resulting in k L decreasing along the channel. Such features are analogical to the corresponding gas–liquid or liquid–liquid two-phase slug flow, but the formation of bubble-droplet clusters caused by relative movement lowered the absolute mass transfer coefficient. These results provide insights for the precise manipulation of gas–liquid–liquid slug flow in microreactors towards process optimization.
研究领域:
化学工程
·
流体力学
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2018
·
IF 3.306
Xin Sun,Chunying Zhu,Taotao Fu,Youguang Ma,Huai Z. Li
Dynamics for droplet breakup with tunnels and formation of satellite droplets in a symmetric microfluidic T-junction are investigated using a high-speed digital camera. The breakup process of droplet could be divided into four sequential stages: squeezing, transition, pinch-off, and thread rupture stages. Effects of the viscosity ratio of both phases λ , the capillary number of the continuous phase Ca c , and the dimensionless droplet length l 0 / w c on the breakup process of droplet are analyzed. In the squeezing stage controlled by squeezing pressure, the variation of the minimum width of the droplet neck with time could be scaled as a power-law relationship with exponent related to λ and l 0 / w c . The transition stage is dominated by the velocity of the fluid, and the pinch-off stage is mainly driven by the capillary force. For these two stages, the evolution of the minimum width of the droplet neck with the remaining time could be described as other power-law relationship with exponent related to λ . In the thread rupture stage controlled by viscous stresses of both phases and the surface tension, the minimum width of droplet neck decreases linearly with time, and the coefficient of the linear function depends on λ . Additionally, for the formation of satellite droplets, the size of satellite droplet increases with the increase of superficial velocity of the fluid and droplet viscosity. Furthermore, a critical capillary number 0.03 is observed in low viscosity of the droplet, which divides the variation of the size of the main satellite droplet with the capillary number into constant area and growth zone.
研究领域:
流体力学
·
生物工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2021
·
IF 4.311
You Ma,Chunying Zhu,Taotao Fu,Youguang Ma,Huai Z. Li
Dynamics of non-Newtonian droplet (CMC aqueous solution) breakup with partial obstruction in microfluidic Y-junction was visually investigated. Three breakup stages were found: squeezing, transition and pinch-off. The effects of the concentration c of CMC, continuous capillary number Ca c and dispersed phase local capillary number Ca d on droplet breakup were studied. In squeezing stage and transition stage, the breakup process could be promoted by increasing Ca d or decreasing c . The pinch-off stage relied primarily on the surface tension and was almost independent of inertial force and viscous force. For the shear thinning non-Newtonian droplet, the length of the daughter droplet was always linearly stretched with time until breakup and the maximum gap width increased with Ca c , but decreased with the increases of c and Ca d .
研究领域:
流体力学
·
微流控技术
·
生物工程
✓ 已验证
产品关联
DOI
高影响因子
AICHE JOURNAL
·
2024
·Vol. 70
·期 8
·e18462
·
IF 3.5
Xin Huang,Mindan Chen,Yunyun Huang,Xiaoming Luo,Lin Teng,Longqiang Xiao,Jiaqing Li
Excessive electric field strength causes the droplets to contact but not coalesce, severely deteriorating the oil–water separation efficiency. The investigation of the non-coalescence of nonidentical droplets in oil under a DC electric field is conducted using high-speed photography. The effects of droplet volume ratio and interfacial tension ratio on the characteristics and critical parameters for droplet non-coalescence are systematically explored. The results show the critical electrocapillary number for the non-coalescence of nonidentical droplets and critical contact cone angle decreases as the volume sum increases or the interfacial tension ratio decreases, which is related to the competition between the resultant electric field force and the interfacial tension force. These results contribute to optimizing the operating parameters of the electric coalescer and improving the oil–water separation efficiency.
研究领域:
化学工程
·
流体力学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2022
·
IF 4.889
Yanjun Deng,Chunying Zhu,Taotao Fu,Youguang Ma
The effect of nanoparticles on droplet coalescence in microchannel was investigated experimentally. The interaction between acid-functionalized nanoparticles and polymers with complementary terminal functional groups facilitates the adsorption of particles at the oil–water interface. Three flow patterns were observed: squeezing coalescence, decompression coalescence and non-coalescence. The presence of nanoparticles significantly reduces the droplet coalescence percentage, and stable droplets could be obtained when the particles concentration increased to 1%. Furthermore, it was found that the film drainage time of squeezing coalescence was independent of the nanoparticles concentration. However, the film drainage time of decompression coalescence increases with nanoparticles concentration. Taking the influence of nanoparticles on the film drainage time into consideration, a new prediction model was proposed. Coupling the droplet contact time with the film drainage time, the critical capillary number for droplet coalescence was obtained. This work could provide important data and technical support for the application of nanoparticle-stabilized emulsions.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
·
2023
·
IF 3.8
Suchen Wu,Liangyu Wu,Juan Chen,Chengbin Zhang,Xiangdong Liu,Yongping Chen,Wei Gao
Droplet splitting in fractal tree-shaped microchannels is studied experimentally in this work. Four flow patterns of droplets splitting in fractal tree-shaped microchannels are distinguished according to the level of bifurcations that all the droplets breakup. The self-similar variation of the droplet pressure and velocity are discussed. And the effect of capillary number and droplet size on the size distribution of daughter and granddaughter droplets are examined quantitatively. The results indicate that the tree-shaped networks with φ = 90° are better than the φ = 120° for the sequential breakup of droplets. Asymmetry in the breakup accumulates as the droplets enter high-level branch channels. Increasing Ca is an effective approach in maintaining the monodispersity of daughter and granddaughter droplets since non-breakup regime is eliminated in the low-levels of branch channels. The performance of splitting droplets is deteriorated as the mother droplet size decreases, that increasing inactive branch channels are observed.
研究领域:
微流体学
·
流体力学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2025
·
IF 4.3
Tao Zhang,Yumian Liu,Jiahe Ru,Yan Pang,Chunqing Zha,Jun Li,Xiang Wang
The behavior of neck breakup and the prediction of droplet volume during Janus droplet generation are investigated experimentally. The generation processes of Janus droplets can be divided into four distinct stages: the uniform extension stage, the accelerated extension stage, the radial necking stage and the rapid breakup stage, while the first two stages represent the filling stage of the droplet tip. Under varying continuous phase flow rates, the diameter of the droplet neck has the uniform evolution with time, and the droplet interface profiles exhibit self-similar characteristics. Differences in the physical properties of the two dispersed phases result in asymmetric contraction at the upper and lower interfaces of the Janus droplet neck, but this influence is reduced near the breakup time of the droplet in the way that the neck contraction tends to synchronize. The volume prediction model is proposed based on the local capillary number of the continuous phase, which demonstrates that the droplet volume consistently decreases as the continuous phase flow rate increases.
研究领域:
微流控
·
流体动力学
·
液滴生成
·
多相流
✓ 已验证
产品关联
DOI
高影响因子
LAB ON A CHIP
·
2024
·Vol. 24
·期 14
·3412-3421
·
IF 6.1
Shi Feng,Chundong Xue,Cunliang Pan,Shengyang Tao
Droplets generated through microfluidics serve as a common platform for assembling artificial cells, which are feasibly tailored using microfluidic methodology. The ability of natural cells to undergo shape changes, such as phagocytosis, is a typical characteristic that researchers aim to mimic in artificial cells. However, simulating the deformation behavior of natural cells within droplets is exceptionally challenging. Here, this study reports a pinocytosis-like phenomenon observed in droplets, termed “droplet drinking”. When droplets traverse a capillary with constrictions, the shear force from the continuous-phase fluid induces relative motion within the droplets, creating concave regions at the rear. These regions facilitate engulfing of the continuous-phase fluid, resulting in the formation of multiple emulsions. This behavior is influenced by the capillary number, and the size of the ingested droplets is governed by the interfacial tension between the two phases. The production of multicore or multi-shell emulsions can be easily accomplished by making slight adjustments to the constrictions. Furthermore, this method demonstrates the integration of reactants into pre-existing droplets, facilitating biochemical reactions. This study presents a convenient approach for generating complex emulsions and an innovative strategy for studying deformation behavior in droplet-based artificial cells.
研究领域:
微流控技术
·
生物物理学
·
化学工程
·
细胞生物学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
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