Article
Engineering, Chemical
Daofan Ma, Di Liang, Chunying Zhu, Taotao Fu, Youguang Ma, Xigang Yuan, Huai Z. Li
Summary: The study visually investigated the breakup process of viscous droplets in Y-shaped microchannels, highlighting the dynamics of droplet breakup with partial obstruction. The rupture process of droplets is divided into squeezing, transition, and rapid pinch-off stages, each displaying unique characteristics related to time, two-phase viscosity ratio, capillary number, and other factors. The findings provide insights into the factors influencing droplet breakup in microscale flow systems.
CHEMICAL ENGINEERING SCIENCE
(2021)
Article
Mechanics
Zhaoyuan Meng, Yubing Zhu, Jiguang Hao, Gengkai Hu, J. M. Floryan
Summary: This study investigates the residual diameter of a droplet impacting a cold surface at a low temperature using high-speed photography. It is found that below a certain threshold temperature, the droplet freezes near its maximum spreading diameter, creating a pancake shape. However, above the threshold temperature, the droplet retracts before freezing. The threshold temperature decreases with increasing Weber number.
Article
Mechanics
Dhrijit Kumar Deka, Sukumar Pati
Summary: This study investigates numerically the merging dynamics of two identical dispersed droplets within a Y-shaped bifurcating channel of rectangular cross-section for different wall wettability conditions, initial droplet sizes, and a fixed Capillary number. The results show that wall wettability affects the merging process of droplets, with hydrophilic and neutral walls leading to longer size droplets and hydrophobic walls resulting in entrapping of droplets within the daughter droplet. The influence of wall wettability is found to be insignificant when the initial sizes of the droplets are smaller.
FLUID DYNAMICS RESEARCH
(2021)
Article
Mechanics
Jinjin Wang, Chunying Zhu, Taotao Fu, Youguang Ma
Summary: In this study, the droplet generation in a wedge-shaped step-emulsification microchannel was experimentally investigated. The dynamics of the dripping flow regime, as the main applicable flow regime, was primarily studied. The results showed that the droplet generation process consists of four stages, and the behaviors of the dispersed phase are influenced by its flow rate and viscosity. The size and formation period of the droplets increase with the increase in dispersed phase flow rate and viscosity. A correlation was proposed to predict the droplet size.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Physics, Fluids & Plasmas
Yashwant Rawat, Sachit Kalia, Pranab Kumar Mondal
Summary: The study develops a mathematical model to describe the imbibition dynamics of an elastic non-Newtonian fluid in a conical microfluidic assay, taking into account geometrical features, rheological parameters, and predicting filling dynamics effectively. The model demonstrates a balance between capillary and viscous forces during imbibition leading to three distinct filling regimes, influenced by the nonuniform cross section which alters the viscous force at the contact line. This analysis enhances understanding of viscoelastic fluid dynamics in nonuniform pathways and provides practical relevance for designing microfluidic assays in biomedical applications.
Article
Mechanics
Zhaomiao Liu, Dezhi Li, Xiang Wang, Yan Pang, Yilin Ma, Mengqi Li, Ju Wang
Summary: This study experimentally investigates the breakup regimes of double emulsion droplets after their on-chip generation, categorizing them into five distinct breakup regimes based on breakup times and the existence of the coupling effect. The evolutions of neck widths and thinning rates of inner and outer droplets are provided to analyze the dynamics of different regimes and stages. The influences of coupling effect on interfacial evolution, collapsing mechanism, force analysis, and breakup critical condition are confirmed through comparisons with results of single emulsion droplets.
Article
Chemistry, Physical
Shensheng Chen, Emad Pirhadi, Xin Yong
Summary: This study investigates the necking dynamics of attractive microgels and reveals that it exhibits liquid-like or solid-like behavior over different time and length scales. The growth of the neck is governed by stress relaxation of the polymers, and it shows an exponential decay in the rate of growth.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2022)
Article
Chemistry, Physical
Keshvad Shahrivar, Francesco Del Giudice
Summary: The use of viscoelastic solutions of xanthan gum in microfluidic devices enables controlled single particle encapsulation, with efficiency up to 2-fold higher than predicted by Poisson statistics. By identifying specific xanthan gum concentrations, researchers discovered that single encapsulation efficiency was increased. An empirical formula was introduced to aid in the design of controlled viscoelastic encapsulation systems.
Article
Mechanics
A. Rubio, E. J. Vega, A. M. Ganan-Calvo, J. M. Montanero
Summary: We experimentally studied the stability of micrometer weakly viscoelastic jets produced with transonic flow focusing. We found that highly stable jets are formed when adding low molecular weight polymer to water at low concentration and reducing the injected flow rate. The capillary instability is delayed and jet breakup occurs at distant locations from the ejected. The intense converging extensional flow in the ejection point results in long-lasting viscoelastic stress that is not relaxed in the jet even for times longer than the polymer relaxation time. The drag force exerted by the outer gas stream and partial polymer entanglement at the jet emission point may contribute to this effect.
Article
Polymer Science
Yuya Doi, Atsushi Takano, Yoshiaki Takahashi, Yushu Matsushita
Summary: The study found that dumbbell polymers form a unique network structure with distinctive entanglement characteristics in the system. Dumbbell PS samples with longer central chains exhibit slower terminal relaxation and retain entanglement features in high-concentration DOP solutions.
Article
Chemistry, Physical
Wenchuan Liu, Ning Li, Zhiqian Sun, Zhenbo Wang, Zengli Wang
Summary: This study presents molecular dynamics simulations of droplet collision and coalescence in shear gas flow between gold plates. The results show that parameters such as shear velocity, normal symmetry velocity, and capillary number play a crucial role in determining the behavior of the droplets.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Chemistry, Multidisciplinary
Li Lei, Yuting Zhao, Jun An, Bo Zhang, Jingzhi Zhang
Summary: The experimental method was used to study the droplet breaking characteristics of a two-phase immiscible liquid-liquid system in symmetric Y-junction microchannels. The results showed that the breakup behavior of the droplets had an impact on the flow pattern and the length of the sub-droplets. A correlation formula for predicting the length of the sub-droplets was proposed.
APPLIED SCIENCES-BASEL
(2022)
Article
Mechanics
Shanshan Li, Lin Wen, Wei Wang
Summary: The asymmetric breakup dynamics of a solitary water droplet in a Y-junction microchannel with a non-uniform outlet flow rate is numerically studied. Four distinct breakup patterns are identified and the impacts of significant parameters on the breakup characteristics are determined. The correlations are used to predict the breakup threshold and propose functional correlations to describe the variation in the splitting ratio of offspring droplets based on the exponential law.
Article
Engineering, Environmental
Yanpeng Dong, Hongwei Zhu, Xingyu Xiang, Zhongdong Wang, Asad Ullah, Sajawal Raza, Chunying Zhu, Wenyuan Fan, Bing Sun, Youguang Ma, Taotao Fu
Summary: The dynamics of viscoelastic droplet formation in T-shaped asymmetric parallel microchannels were investigated using a high-speed camera. The effects of fluid viscoelasticity and flow rates on droplet stability, uniformity, and flow distribution were explored. The results showed that the viscoelasticity influenced the different stages of droplet formation, and increasing the continuous phase flow rate improved stability and affected droplet uniformity. Prediction models for fluid flow distribution, droplet size, and formation period were established, and the breakup mode and satellite droplet size were also studied. The findings demonstrated the importance of fluid viscoelasticity and flow rates in droplet formation.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Chemistry, Analytical
Chao Yuan, Hongna Zhang, Xiaobin Li, Masamichi Oishi, Marie Oshima, Qinghe Yao, Fengchen Li
Summary: Oscillatory flow in micro-scaled devices can be achieved through the nonlinear characteristics of viscoelastic fluid flow. The use of an improved T-shaped channel structure can significantly enhance the oscillation intensity.
