Numerical Analysis of Junction Point Pressure during Droplet Formation in Y-Junction Microchannel

2013 ◽  
Vol 481 ◽  
pp. 241-246
Author(s):  
Zhao Miao Liu ◽  
Li Kun Liu
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Contact Angles ◽  
Junction Point ◽  
Dispersed Phase ◽  
Wetting Property ◽  
Point Pressure ◽  
Pressure Changes

Junction point pressure changes during droplet formation in Y-junction microchannels with differed Y-angles, wetting property and capillary number of the liquid by using a three dimensional numerical simulation. The pressure of the junction point fluctuates throughout the droplet formation process, and it can be used to depict exactly and directly different stages of droplet in microchannels. And the pressure of junctions with different Y-angles of microchannel, different contact angles of dispersed phase with the surface, and different capillary numbers of continuous phase could thus be investigated via the droplet formation mechanism.

Effect of Geometry on Droplet Generation in a Microfluidic T-Junction

2013 ◽  
Author(s):  
Katerina Loizou ◽  
Wim Thielemans ◽  
Buddhika N. Hewakandamby
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Main Channel ◽  
Superficial Velocity ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Aspect Ratios ◽  
The Cross

The main aim of this study is to examine how the droplet formation in microfluidic T-junctions is influenced by the cross-section and aspect ratio of the microchannels. Several studies focusing on droplet formation in microfluidic devices have investigated the effect of geometry on droplet generation in terms of the ratio between the width of the main channel and the width of the side arm of the T-junction. However, the contribution of the aspect ratio and thus that of the cross-section on the mechanism of break up has not been examined thoroughly with most of the existing work performed in the squeezing regime. Two different microchannel geometries of varying aspect ratios are employed in an attempt to quantify the effect of the ratio between the width of the main channel and the height of the channel on droplet formation. As both height and width of microchannels affect the area on which shear stress acts deforming the dispersed phase fluid thread up to the limit of detaching a droplet, it is postulated that geometry and specifically cross-section of the main channel contribute on the droplet break-up mechanisms and should not be neglected. The above hypothesis is examined in detail, comparing the volume of generated microdroplets at constant flowrate ratios and superficial velocities of continuous phase in two microchannel systems of two different aspect ratios operating at dripping regime. High-speed imaging has been utilised to visualise and measure droplets formed at different flowrates corresponding to constant superficial velocities. Comparing volumes of generated droplets in the two geometries of area ratio near 1.5, a significant increase in volume is reported for the larger aspect ratio utilised, at all superficial velocities tested. As both superficial velocity of continuous phase and flowrate ratio are fixed, superficial velocity of dispersed phase varies. However this variation is not considered to be large enough to justify the significant increase in the droplet volume. Therefore it can be concluded that droplet generation is influenced by the aspect ratio and thus the cross-section of the main channel and its effect should not be depreciated. The paper will present supporting evidence in detail and a comparison of the findings with the existing theories which are mainly focused on the squeezing regime.

Droplet Formation in a Microchannel T-Junction With Different Step Structure Position

2020 ◽  
Vol 143 (7) ◽  
Author(s):  
Mohammad Yaghoub Abdollahzadeh Jamalabadi ◽  
Rasoul Kazemi ◽  
Mohammad Ghalandari
Keyword(s):  
Nusselt Number ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Flow Path ◽  
The Other ◽  
Two Phase ◽  
Fluid Behavior ◽  
Discrete Phase

Abstract In this study, numerical simulation of formation of droplet within T-shaped microchannel is investigated. Three-dimensional, transient and two-phase numerical solution for four different microchannels with different stepping positions in the flow path was performed. Various parameters such as volume fraction, Nusselt number, pressure, Reynolds number, and temperature are discussed. The results show that the location of stepped barriers in the flow path affects the process of droplet formation, its number and size in the microchannel and should be considered as an important factor in determining the fluid behavior in the microchannel. It was observed that by placing half of the step at the entrance and the other half after the entrance, the continuous phase (S3 mode) was formed in 37.5 s compared to the other modes. The droplets were also smaller in size and more in numbers. It was also observed that the maximum value for the Nusselt number was obtained for the S2 mode where the step was located just above the discrete-phase entrance. In addition, the pressure at the inlet was higher and the flow velocity increased after the step and its pressure decreased, and continued to decrease due to frictional path.

scholarly journals Influence on droplet formation in the presence of nanoparticles in a microfluidic T-junction

2012 ◽  
Vol 16 (5) ◽  
pp. 1429-1432
Author(s):  
Rui-Jin Wang ◽  
Zhi-Hua Li
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Liquid Interface ◽  
Dispersed Phase ◽  
Microscopic Mechanism ◽  
Formation Dynamics

The droplet formation in the presence of nanoparticles was studied in a T-shaped microfluidic device numerically. Nanoparticles in continuous phase did not influence droplet formation dynamics obviously. Contrarily, the presence of nanoparticles in dispersed phase will influence evidently droplet formation dynamics, the possible reason is that the accumulation of nanoparticles at the liquid-liquid interface would cause the variation of interfacial tension and the anisotropy of nanoparticles? movement at interface. Discussions on microscopic mechanism of droplet formation in the presence of nanoparticles were carried out.

scholarly journals Experimental Studies of Droplet Formation Process and Length for Liquid–Liquid Two-Phase Flows in a Microchannel

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1341
Author(s):  
Li Lei ◽  
Yuting Zhao ◽  
Wukai Chen ◽  
Huiling Li ◽  
Xinyu Wang ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Scaling Law ◽  
Experimental Studies ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Volume Flow ◽  
Dispersed Phase ◽  
Two Phase

In this study, changes in the droplet formation mechanism and the law of droplet length in a two-phase liquid–liquid system in 400 × 400 μm standard T-junction microchannels were experimentally studied using a high-speed camera. The study investigated the effects of various dispersed phase viscosities, various continuous phase viscosities, and two-phase flow parameters on droplet length. Two basic flow patterns were observed: slug flow dominated by the squeezing mechanism, and droplet flow dominated by the shear mechanism. The dispersed phase viscosity had almost no effect on droplet length. However, the droplet length decreased with increasing continuous phase viscosity, increasing volume flow rate in the continuous phase, and the continuous-phase capillary number Cac. Droplet length also increased with increasing volume flow rate in the dispersed phase and with the volume flow rate ratio. Based on the droplet formation mechanism, a scaling law governing slug and droplet length was proposed and achieved a good fit with experimental data.

Investigation on the Droplet Formation Time With Xanthan Gum Solutions at a T-Junction

2012 ◽  
Author(s):  
Zhipeng Gu ◽  
Jong-Leng Liow ◽  
Guofeng Zhu
Keyword(s):  
Flow Rate ◽  
Xanthan Gum ◽  
Critical Concentration ◽  
Droplet Diameter ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Formation Time ◽  
Drop Formation ◽  
Dispersed Phase ◽  
Phase Flow

Xanthan gum solutions with various concentrations were used as the dispersed phase to study the formation time for drop formation at a T-junction. Two critical concentrations (0.05 and 0.2 wt%) of xanthan gum solutions were observed resulting in three distinct regimes. The droplet diameter increased with increasing xanthan gum concentration within each regime but the transition through each critical concentration was accompanied by a significant reduction in the droplet size. Experimental results showed that the droplet formation time decreased exponentially with increasing continuous phase flow rate. It was also found that the formation time was reduced with increasing dispersed phase flow rate. Xanthan gum solutions with a higher concentration within each regime resulted in a longer formation time, and there was a decrease in the formation time at each critical concentration. The formation time consists of growth and breakup stages and the effect of xanthan gum concentration on each stage was examined.

A Comparison Between Round Turbulent Jets and Particle-Laden Jets in Crossflow by Using Time-Resolved Stereoscopic Particle Image Velocimetry

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
F. J. Diez ◽  
M. M. Torregrosa ◽  
S. Pothos
Keyword(s):  
Particle Image Velocimetry ◽  
High Intensity ◽  
Particle Image ◽  
Three Dimensional ◽  
Continuous Phase ◽  
Stereoscopic Particle Image Velocimetry ◽  
Dispersed Phase ◽  
Time Resolved ◽  
Image Velocimetry ◽  
Phase Images

Time-resolved stereoscopic particle image velocimetry (TR-ST-PIV) measurements were performed to compare the velocity and vorticity field, and the three-dimensional high intensity vorticity structures between a round turbulent single-phase jet and a particle-laden jet in crossflow. The experiments involved steady fresh water jet sources with a particle mass loading of ∼2.0% injected into steady fresh water crossflows. The TR-ST-PIV system was combined with a phase discrimination method that separates two-phase stereo PIV images into dispersed phase images and continuous phase images that are analyzed by using particle tracking velocimetry and stereo-PIV algorithms, respectively. The analysis shows the importance of phase separation for accurate velocity results. It provides instantaneous velocity fields where the dispersed phase preferentially concentrated in regions of low vorticity with the velocity not matching the continuous phase. The jet and the particle-laden jets trajectories are compared to each other and with results in the literature. Similarly, a comparison of mean velocity and vorticity fields between both flows suggest enhanced mixing in the particle-laden jet due to the effects of the dispersed phased which lowered the centerline velocities and enhanced the penetration in the cross-stream direction of the continuous phase. The Taylor’s frozen flow hypothesis is applied to reconstruct the 3D high intensity vorticity structures in a volume. The visualization of the three-dimensional structures corresponding to the intermediate scales of the flow shows slightly elongated structures preferentially aligned with the jet centerline axis.

Sign in / Sign up

Export Citation Format

Share Document