scholarly journals Lattice Boltzmann Simulation of Droplet Generation in a Microfluidic Cross-Junction

2011 ◽  
Vol 9 (5) ◽  
pp. 1235-1256 ◽  
Author(s):  
Haihu Liu ◽  
Yonghao Zhang
Keyword(s):  
Droplet Size ◽  
Flow Rate ◽  
Lattice Boltzmann ◽  
Capillary Number ◽  
Rate Ratio ◽  
Viscosity Ratio ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Viscous Force ◽  
Flow Rate Ratio

AbstractUsing the lattice Boltzmann multiphase model, numerical simulations have been performed to understand the dynamics of droplet formation in a microfluidic cross-junction. The influence of capillary number, flow rate ratio, viscosity ratio, and viscosity of the continuous phase on droplet formation has been systematically studied over a wide range of capillary numbers. Two different regimes, namely the squeezinglike regime and the dripping regime, are clearly identified with the transition occurring at a critical capillary number Cacr. Generally, large flow rate ratio is expected to produce big droplets, while increasing capillary number will reduce droplet size. In the squeezing-like regime (Ca ≤ Cacr), droplet breakup process is dominated by the squeezing pressure and the viscous force; while in the dripping regime (Ca ≤ Cacr), the viscous force is dominant and the droplet size becomes independent of the flow rate ratio as the capillary number increases. In addition, the droplet size weakly depends on the viscosity ratio in both regimes and decreases when the viscosity of the continuous phase increases. Finally, a scaling law is established to predict the droplet size.

SIMULATIONS OF DROPLET FORMATION IN A T-JUNCTION MICRO-CHANNEL USING THE PHASE FIELD METHOD

2014 ◽  
Vol 11 (04) ◽  
pp. 1350096 ◽  
Author(s):  
L. L. WANG ◽  
G. J. LI ◽  
H. TIAN ◽  
Y. H. YE
Keyword(s):  
Contact Angle ◽  
Flow Rate ◽  
Capillary Number ◽  
Rate Ratio ◽  
Droplet Formation ◽  
Field Method ◽  
Leakage Rate ◽  
Phase Field Method ◽  
Flow Rate Ratio ◽  
Micro Channel

Micro-fabrication techniques are developed rapidly because they offer numerous benefits for chemical and biological industries. Numerical simulations (based on incompressible Navier–Stokes equations) are presented of the two-phase flow in a cross-flowing T-junction micro-channel using the phase field method and the results are in agreement with experimental measurements. The leakage rate in the gap between the droplet and lower wall decreases during the droplet formation, the relationship between the leakage rate and the derivative of the up-stream droplet size is obtained, which is applicable when the droplet contacts with the lower wall on the wetted conditions or expands to the up-stream in the main channel. The droplet formation is related to several factors, including the capillary number, the contact angle, the flow rate ratio, and the micro-channel shape. The critical capillary number could distinguish between the squeezing and dripping regimes for the generation of different kinds of droplets. The simulations show that the critical capillary number is 0.012. Influence of those factors on the droplet length is related to the leakage rate. The leakage rate of the continuous phase decreases slowly as the flow rate ratio decreases or contact angle increases. In the squeezing regime, the leakage rate is weakly influenced by the contact angle at the small flow rate ratio and is different in three type micro-channels, the droplet length increases with the increase in contact angle which intensifies growth at the big flow rate ratio, and the longest droplet is obtained in the Y-junction micro-channel. In the dripping regime, at the big flow rate ratio the leakage rate is almost independent to the contact angle and micro-channel shape, and the droplet length also is same.

scholarly journals Drop formation in cross-junction micro-channel, using lattice Boltzmann method

2018 ◽  
Vol 22 (2) ◽  
pp. 909-919 ◽  
Author(s):  
Kayvan Fallah ◽  
Moahammad Rahni ◽  
Alireza Mohammadzadeh ◽  
Mohammad Najafi
Keyword(s):  
Contact Angle ◽  
Lattice Boltzmann Method ◽  
Flow Rate ◽  
Lattice Boltzmann ◽  
Rate Ratio ◽  
Viscosity Ratio ◽  
Flow Rate Ratio ◽  
Drop Formation ◽  
Micro Channels ◽  
Boltzmann Method

Drop formation in cross-junction micro-channels is numerically studied using the lattice Boltzmann method with pseudo-potential model. To verify the simulation, the results are compared to previous numerical and experimental data. Furthermore, the effects of capillary number, flow rate ratio, contact angle, and viscosity ratio on the flow patterns, drop length, and interval between drops are investigated and highlighted. The results show that the drop forming process has different regimes, namely, jetting, drop, and squeezing regimes. Also, it is shown that increasing in the flow rate ratio in the squeezing regime causes increment in drop length and decrement in drops interval distance. On the other hand, the drops length and the interval between the generated drops increase as contact angle increases. Also, the drop length and distance between drops is solely affected by viscosity ratio.

scholarly journals Examining the Effect of Flow Rate Ratio on Droplet Generation and Regime Transition in a Microfluidic T-Junction at Constant Capillary Numbers

Inventions ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 54 ◽  
Author(s):  
Katerina Loizou ◽  
Voon-Loong Wong ◽  
Buddhika Hewakandamby
Keyword(s):  
Transition Region ◽  
Flow Rate ◽  
Capillary Number ◽  
Rate Ratio ◽  
Continuous Phase ◽  
Flow Rate Ratio ◽  
Phase Flow ◽  
Regime Transition ◽  
Droplet Volume ◽  
Rate Ratios

The focus of this work is to examine the effect of flow rate ratio (quotient of the dispersed phase flow rate over the continuous phase flow rate) on a regime transition from squeezing to dripping at constant capillary numbers. The effect of the flow rate ratio on the volume of droplets generated in a microfluidic T-junction is discussed, and a new scaling law to estimate their volume is proposed. Existing work on a regime transition reported by several researchers focuses on the effect of the capillary number on regime transition, and the results that are presented in this paper advance the current understanding by indicating that the flow rate ratio is another parameter that dictates regime transition. In this paper, the transition between squeezing and dripping regimes is reported at constant capillary numbers, with a transition region identified between squeezing and dripping regimes. Dripping is observed at lower flow rate ratios and squeezing at higher flow rate ratios, with a transition region between the two regimes at flow rate ratios between 1 and 2. This is presented in a flow regime map that is constructed based on the observed mechanism. A scaling model is proposed to characterise droplet volume in terms of flow rate ratio and capillary number. The effect of flow rate ratio on the non-dimensional droplet volume is presented, and lastly, the droplet volume is expressed in terms of a range of parameters, such as the viscosity ratio between the dispersed and the continuous phase, capillary number, and the geometrical characteristics of the channels.

Parametric Study of Droplet Formation and Characteristics Within Microfluidic Devices — A Case Study

2020 ◽  
Vol 12 (07) ◽  
pp. 2050077
Author(s):  
Seyedeh Sarah Salehi ◽  
Amir Shamloo ◽  
Siamak Kazemzadeh Hannani
Keyword(s):  
Interfacial Tension ◽  
Physical Properties ◽  
Flow Rate ◽  
Viscosity Ratio ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Phase Flow ◽  
Phase Density ◽  
Size And Shape ◽  
The Impact

Droplet-based microfluidics technologies hold great attention in a wide range of applications, including chemical analysis, drug screening, and food industries. This work aimed to describe the effects of different physical properties of the two immiscible phases on droplet formation in a flow-focusing microfluidic device and determining proper flow rates to form a droplet within the desired size range. A numerical model was developed to solve the governing equations of two-phase flow and the results were validated with previous experimental results. The results demonstrate different types of droplet formation regimes from dripping to jetting and different production rates of droplets as a consequence of the impact of each property on fluid flow, including the viscosity ratio, density, interfacial tension, and the flow rate ratio. Based on the results, flow rate, viscosity, and interfacial tension strongly affect the droplet formation regime as well as its size and shape. Droplet diameter increases by increasing the dispersed to continuous phase flow rate as well as the interfacial tension while it decreases by increasing the viscosity ratio and the continuous phase density. Moreover, the formation of satellite droplets was modeled, and the effect of interfacial tension, the viscosity of the dispersed phase and the continuous phase density were found to be important on the conditions that the satellite droplets are suppressed. Since the formation of the satellite droplets induces polydispersity in droplet size, this phenomenon is avoided. Collectively, choosing appropriate aqueous and oil phases with proper physical properties is crucial in forming monodisperse droplets with defined size and shape.

Slug Formation Analysis of Liquid–Liquid Two-Phase Flow in T-Junction Microchannels

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Jin-yuan Qian ◽  
Xiao-juan Li ◽  
Zan Wu ◽  
Zhi-jiang Jin ◽  
Junhui Zhang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Two Phase Flow ◽  
Continuous Phase ◽  
Channel Width ◽  
Flow Rate Ratio ◽  
Width Ratio ◽  
Phase Flow ◽  
Channel Depth ◽  
Two Phase

Slug flow is a common flow pattern in the liquid–liquid two-phase flow in microchannels. It is an ideal pattern for mass transfer enhancement. Many factors influence the slug formation such as the channel geometries (channel widths, channel depth), flow rates of the two phase, and physical properties. In this paper, in order to investigate the liquid–liquid two-phase slug formation in a T-junction microchannel quantitatively, the volume of fluid (VOF) method is adopted to simulate the whole slug formation process. With the validated model, the effects of the disperse phase channel width, channel depth, and two-phase flow rate ratio on slug formation frequency and slug size (slug volume and slug length) are analyzed with dimensionless parameters. Dimensionless parameters include the disperse-to-continuous phase channel width ratio, height-to-width ratio, and two-phase flow rate ratio. Results show that both the channel geometry and two-phase flow rate ratio have a significant influence on slug formation. Compared with the conventional slug formation stages, a new stage called the lag stage emerges when the disperse phase channel width decreases to half of the continuous phase channel width. When the channel depth decreases to one third of the continuous phase channel width, the flow patterns become unstable and vary with the two-phase flow rate ratio. Moreover, empirical correlations are proposed to predict the slug formation frequency. The correlation between slug formation frequency and slug volume is quantified.

Numerical Simulation of the Droplet Formation in a T-Junction Microchannel by a Level-Set Method

2018 ◽  
Vol 71 (12) ◽  
pp. 957 ◽  
Author(s):  
Wenbo Han ◽  
Xueye Chen
Keyword(s):  
Numerical Simulation ◽  
Contact Angle ◽  
Interfacial Tension ◽  
Level Set Method ◽  
Level Set ◽  
Flow Rate ◽  
Rate Ratio ◽  
Continuous Phase ◽  
Flow Rate Ratio ◽  
Control Parameters

To satisfy the increasingly high demands in many applications of microfluidics, the size of the droplet needs accurate control. In this paper, a level-set method provides a useful method for studying the physical mechanism and potential mechanism of two-phase flow. A detailed three-dimensional numerical simulation of microfluidics was carried out to systematically study the generation of micro-droplets and the effective diameter of droplets with different control parameters such as the flow rate ratio, the continuous phase viscosity, the interfacial tension, and the contact angle. The effect of altering the pressure at the x coordinate of the main channel during the droplet formation was analysed. As the simulation results show, the above control parameters have a great influence on the formation of droplets and the size of the droplet. The effective droplet diameter increases when the flow rate ratio and the interfacial tension increase. It decreases when the continuous phase viscosity and the contact angle increase.

Numerical Study on Droplet Formation in a Microchannel T-Junction Using the VOF Method

2010 ◽  
Author(s):  
Shobeir Aliasghar Zadeh ◽  
Rolf Radespiel
Keyword(s):  
Surface Tension ◽  
Flow Rate ◽  
Capillary Number ◽  
Numerical Study ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Vof Method ◽  
Experimental Results ◽  
Glycerol Solution ◽  
Hexahedral Elements

The liquid-liquid two-phase flow in a T-junction was numerically investigated applying the VOF method and is compared with experimental results. The geometry was generated and meshed using the software Gridgen, and the corresponding equations for the CFD analysis were solved by using the commercial software Fluent (Fluent 12). The generated mesh consists of block-structured grids with hexahedral elements. Water-Glycerol solution (to-be-dispersed phase) and silicone oil (continuous phase) at room conditions are considered as fluids for this work. The effect of various parameters such as flow rate of the phases, width of the channel, viscosity and surface tension on the droplet formation are investigated and compared with available experimental results [1]. The breakup mechanism of droplets in various capillary-number regimes are explained. The numerical results of the length of the generated droplets as a function of the capillary number (varying the flow rate of the continuous phase) are in good agreement with the experimental values, which were measured using the same geometrical and physical properties. Further studies indicate that at a constant flow rate of the continuous phase, the droplet length rises strongly if the flow rate of the disperse phase increases, whereas the relative effects of the viscosity of the continuous phase, and the surface tension between phases on the length of droplets are moderate.

Numerical simulation and experiment of droplet formation in circular cross-section micro-channels

2019 ◽  
Vol 33 (18) ◽  
pp. 1950200
Author(s):  
Hongcheng Wang ◽  
Chengxin Tang ◽  
Miaomiao Zhao ◽  
Liqun Wu ◽  
Baohua Yu
Keyword(s):  
Interfacial Tension ◽  
Cross Section ◽  
Droplet Size ◽  
Flow Rate ◽  
Microfluidic Chip ◽  
Capillary Number ◽  
Circular Cross Section ◽  
Continuous Phase ◽  
Micro Channel ◽  
Micro Channels

In recent decades, microfluidics in biological applications have experienced significant growth due to their advantages of small volume, low cost, short reaction time and high throughput. Almost all cross-section shapes of micro-channels in microfluidic chips are rectangular or triangular by the existing chip fabricating technologies, including hot embossing, lithography, etching and injection molding, etc. However, compared with the above micro-channel shapes, the circular one has the advantages in aspects of fluid flow, droplet generating, heat transfer and its replication for blood vessels. This paper presents a T-junction droplet microfluidic chip with circular cross-section micro-channels. The effect of micro-channel wettability, interfacial tension, velocity and flow rate of continuous phase on droplet size are simulated and mechanism of droplets generating process is explored. Comparing with continuous phase viscosity and interfacial tension, flow rate plays a decisive role in determining the droplet size which is in the range of 100–350 [Formula: see text]m according to the simulation result. The Capillary number is affected by the above three parameters and an estimating numerical method for generated droplet size was proposed according to the above simulation results and calculated by Capillary number. The droplets, the sizes of which were in the range of 20–400 [Formula: see text]m, were produced by varying the parameters of water and oil flow rates in the designed T-junction droplet microfluidic chip with circular cross-section micro-channels.

Determination of flow rate ratio for plate valve operating in two-phase medium

1989 ◽  
Vol 25 (7) ◽  
pp. 394-396
Author(s):  
V. E. Shcherba ◽  
I. S. Berezin ◽  
S. S. Danilenko ◽  
I. E. Titov ◽  
P. P. Filippov
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Flow Rate Ratio ◽  
Two Phase ◽  
Plate Valve ◽  
Phase Medium

Study of Fingering Dynamics of Two Immiscible Fluids in a Homogeneous Porous Medium with Considering Wettability Effects Using a Pore-Scale Multicomponent Lattice Boltzmann Model

2021 ◽  
Author(s):  
Eslam Ezzatneshan ◽  
Reza Goharimehr
Keyword(s):  
Porous Medium ◽  
Dynamic Viscosity ◽  
Lattice Boltzmann ◽  
Capillary Number ◽  
Viscosity Ratio ◽  
Viscous Fingering ◽  
Immiscible Fluids ◽  
Pore Scale ◽  
Homogeneous Porous Medium ◽  
Wetting Fluid

In the present study, a pore-scale multicomponent lattice Boltzmann method (LBM) is employed for the investigation of the immiscible-phase fluid displacement in a homogeneous porous medium. The viscous fingering and the stable displacement regimes of the invading fluid in the medium are quantified which is beneficial for predicting flow patterns in pore-scale structures, where an experimental study is extremely difficult. Herein, the Shan-Chen (S-C) model is incorporated with an appropriate collision model for computing the interparticle interaction between the immiscible fluids and the interfacial dynamics. Firstly, the computational technique is validated by a comparison of the present results obtained for different benchmark flow problems with those reported in the literature. Then, the penetration of an invading fluid into the porous medium is studied at different flow conditions. The effect of the capillary number (Ca), dynamic viscosity ratio (M), and the surface wettability defined by the contact angle (θ) are investigated on the flow regimes and characteristics. The obtained results show that for M<1, the viscous fingering regime appears by driving the invading fluid through the pore structures due to the viscous force and capillary force. However, by increasing the dynamic viscosity ratio and the capillary number, the invading fluid penetrates even in smaller pores and the stable displacement regime occurs. By the increment of the capillary number, the pressure difference between the two sides of the porous medium increases, so that the pressure drop Δp along with the domain at θ=40∘ is more than that of computed for θ=80∘. The present study shows that the value of wetting fluid saturation Sw at θ=40∘ is larger than its value computed with θ=80∘ that is due to the more tendency of the hydrophilic medium to absorb the wetting fluid at θ=40∘. Also, it is found that the magnitude of Sw computed for both the contact angles is decreased by the increment of the viscosity ratio from Log(M)=−1 to 1. The present study demonstrates that the S-C LBM is an efficient and accurate computational method to quantitatively estimate the flow characteristics and interfacial dynamics through the porous medium.

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