A computational study on phase velocity mediated droplet splitting and its mechanism at T-junction microchannel

Biswas, Saikat; Pattader, Partho Sarathi Gooh; Mandal, Tapas Kumar

doi:10.1007/s40430-021-03107-0

Cited by 5 publications

(2 citation statements)

References 25 publications

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“…The PRESTO (PREssure STaggering Option) method was cast off to determine pressure. The QUICK (Quadratic Upstream Interpolation for Convective Kinematics) (Biswas et al 36 ) technique was cast off to discretize the spatial derivatives.…”

Section: Volume Of Fluid Methodsmentioning

confidence: 99%

Three‐dimensional simulation of dripping and jetting phenomenon in a flow‐focusing geometry

Biswas,

Pattader,

Mandal

2024

Asia-Pacific J Chem Eng

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Abstract3D simulations have been achieved on a flow‐focusing geometry employing the VOF method to study the consequence of viscosity, surface tension, wettability, and geometry on drop generation for the dripping regime. Here the dispersed phase is the PDMS oil (polydimethylsiloxane), and the continuous phase is the water. Simulations were performed at different oil‐to‐water viscosity ratios of 3, 12, 27, and 50. The interfacial tension between PDMS oil and water is 0.0118 N/m. It has been abridged to 0.008 N/m, 0.005 N/m, and 0.002 N/m, and simulations were performed. The walls of the microchannel are considered to be PMMA surfaces. The contact angle of an oil droplet on the PMMA surface in the presence of water is 140°. The effect of wettability was shown at various contact angles (angle created by water droplet on the PMMA surface in the presence of oil) of 0°, 40°, 90°, 135° and 180°. The frequency of droplet generation (1/s), non‐dimensional droplet length (L/Wc), droplet volume (nl), and droplet velocity (m/s) have been calculated for each of the cases. A flow pattern map has been industrialized classifying the dripping and jetting regimes. A comparison between normal geometry and two constricted geometries (having different orifice lengths) based on the frequency of droplet, non‐dimensional drop length, drop volume, and drop velocity has been made for both dripping and jetting regimes. Prediction of simulated non‐dimensional droplet length has also been made using dimensional analysis.

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Section: Volume Of Fluid Methodsmentioning

confidence: 99%

Three‐dimensional simulation of dripping and jetting phenomenon in a flow‐focusing geometry

Biswas,

Pattader,

Mandal

2024

Asia-Pacific J Chem Eng

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“…The pressure was applied using pressure staggering option (PRESTO). The quadratic upstream interpolation for convective kinematics (QUICK) [ 36 ] technique was used to discretize the spatial derivatives.…”

Section: Computational Modelmentioning

confidence: 99%

Droplet splitting in multi‐furcating microchannel: A three‐dimensional numerical simulation study

2023

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This work investigates the splitting of a droplet in a multi‐furcating microfluidic channel for a two‐phase system employing 3D simulation. The simulations were performed using an explicit volume of fluid (VOF) method and have been validated using experimental data taken from the literature. The width ratio of the branch channel to the main channel is set to 0.25 for five branches of the multi‐furcating microchannel, as it is the width ratio at which multiple splitting takes place. Simulations have been carried out at different oil velocities (Vo) ranging from 0.12 to 0.22 m/s and at different water velocities (Vw) ranging from 0.002 to 0.10 m/s. Oil fraction data in the main channel has been recorded and compared with the homogenous model. The average difference between the homogeneous model and the 3D simulations is 22.68%. Analysis of dimensionless droplet length in ±0°, ± 40°, and 90° branch channels has been done. α (length of the droplet in branch channel/width of the main channel) increases up to a flow rate ratio of 0.38, and then decreases, whereas β (length of the droplet in the main channel/width of the main channel) increases with an increase in flow rate ratio. A flow pattern map has been developed to identify the various droplet breakup regimes at the junction. Frequency (counts per unit time) of droplet generation increases with capillary number for all the branch channels except for the 0° branch channel, where the regime is that the droplet passes through three branch channels. The volume distribution ratio (λ) decreases at first, then increases with an increase in capillary number for 0°:90° and 40°:90° angle branch channels for the regime where the droplet passes through five branch channels. For the regime where the droplet passes through three branch channels, the trend is likely linear with λ = 0.3 ± 0.04. The dimensionless mother droplet length increases with an increase in capillary number for Vo = 0.13 and 0.16 m/s, but for Vo = 0.19 and 0.22 m/s, the dimensionless mother droplet length becomes constant after capillary number = 0.26 and 0.30 respectively. The droplet breakup time (t) for regime (a), where the droplet passes through three branch channels, is 0.002 s; for regime (b), where the droplet passes through five branch channels, it is 0.001 s; and for regime (c), where multi‐furcation and coalescence of the droplet occurs, it is 0.0005 s. Multiple splitting is a topic covered in this paper that can be applied to upcoming microfluidic platform‐based devices.

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A computational study on transition mechanism of dripping to jetting flow in a flow‐focusing geometry

Biswas,

Jha,

Kayal

et al. 2024

Can J Chem Eng

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Abstract2D simulations have been performed to investigate flow regimes in a flow‐focusing geometry by changing the dispersed phase and continuous phase velocities. The dispersed phase is polydimethylsiloxane (PDMS), and the continuous phase is water. Simulations have been performed in a range of oil–water viscosity ratio from 3 to 50, and interfacial tension ranges from 0.0118 to 0.002 N/m. The walls of the microchannel are considered to be poly(methyl methacrylate) (PMMA) surfaces. The contact angle (θ) of an oil droplet in the presence of water wetting the PMMA surface is 140°. Our study observed two types of flow regimes, namely dripping and jetting, by changing the dispersed phase and continuous phase velocities. The sequential time steps of void fraction contour have been presented to explore the droplet formation mechanism. The droplet pinch‐off time and jet growth time have been calculated for the dripping and jetting regime, respectively. The outcomes are summarized in the form of a flow pattern map at a viscosity ratio of 12 and interfacial tension of 0.0118 N/m, which shows the transition boundary between dripping and jetting phenomena. The simulated transition boundary agrees well with the analytical solution available in the literature. The effect of oil–water viscosity ratio and interfacial tension on droplet size is also investigated. These findings will help understand different flow regimes and their transition in a flow focusing geometry and will directly apply to microfluidic platform‐based devices.

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A computational study on phase velocity mediated droplet splitting and its mechanism at T-junction microchannel

Cited by 5 publications

References 25 publications

Three‐dimensional simulation of dripping and jetting phenomenon in a flow‐focusing geometry

Three‐dimensional simulation of dripping and jetting phenomenon in a flow‐focusing geometry

Droplet splitting in multi‐furcating microchannel: A three‐dimensional numerical simulation study

A computational study on transition mechanism of dripping to jetting flow in a flow‐focusing geometry

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