Rotational instabilities in microchannel flows

Sengupta, Srijan; Ghosh, Sukhendu; Saha, Sandeep; Chakraborty, Suman

doi:10.1063/1.5088438

Cited by 13 publications

(8 citation statements)

References 51 publications

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“…The higher growth rate due to spanwise disturbances reduces the magnitude of critical Reynolds number considerably. 11,67,68 In figure and (b)) , which is in contrast to earlier findings for streamwise two-dimensional disturbances. 32,56 Although the critical Reynolds number is not distinguishable in the figure 6(c) and (d), the same can be concluded for shear-thinning index 0.3568 n = .…”

Section: Numerical Validationcontrasting

confidence: 93%

“…The higher growth rate due to spanwise disturbances reduces the magnitude of critical Reynolds number considerably. 11,67,68 In figure 6(a)-(d), the neutral stability boundaries are shown by varying the time constant λ , with (see figure 6(a) and (c)) and without (see figure 6 µ′ ≠ . The effect of shear-thinning (increasing λ ) for spanwise system of rotation is progressively destabilizing in the Re β − plane for shear-thinning index 0.2 n = (see figure 6(a)…”

Section: Stability Curves and Critical Parametersmentioning

confidence: 99%

“…In traditional stationary microfluidic devices, mixing occurs predominantly due to diffusion, posing significant challenges towards achieving a homogeneous solution. 10 However, in a rotating platform, enhanced mixing becomes possible by means of Coriolis force, 4,11 which generates secondary flow into the rotating system (see figure 1). On introducing secondary flow caused by Coriolis forces, an enhanced level of mixing at such a small scale, thus, becomes achievable.…”

Section: Introductionmentioning

confidence: 99%

“…In order to facilitate mixing processes by triggering rotational instabilities, various simple configurations have been devised, where the Coriolis force overwhelms the centrifugal force. 1,11,[25][26][27] This has led to the realization of important biological operations, for example, separation of blood constituents from whole blood. 3,[28][29][30][31] However, the underlying procedure can be made more rapid and efficient only by developing a more comprehensive understanding of the mechanism of instability under various rotational forces on a revolving CD based device, amidst rheologically complex constitution of the fluid medium.…”

Section: Introductionmentioning

confidence: 99%

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Coriolis force-based instability of a shear-thinning microchannel flow

2020

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Instability mechanism based on Coriolis force, on a rapidly rotating portable device handling shear-thinning fluids such as blood, is of utmost importance for eventual detection of diseases by mixing with the suitable reagents. Motivated by this proposition, the present study renders a modal stability analysis of shear-thinning fluids in a rotating microchannel modelled by the Carreau rheological law. When a microchannel is engraved a rotating compact disc (CD)-based device, the centrifugal force acts as the driving force that actuates the flow and the Coriolis force enhances the mixing process in significantly short span by destabilizing the flow. An Orr-Sommerfeld-Squire analysis is performed to explore the role of these forces on the linear stability of rotating shear-thinning flow. Reported results on shear-thinning flow with streamwise disturbances indicate that the critical Reynolds number for the flow transition with viscosity perturbation is nearly half of that of the critical value for the same without viscosity perturbation. In sharp contrast, the present analysis considering spanwise disturbances reveals that the critical Reynolds numbers with and without viscosity perturbation remain virtually unaltered under rotational effects. However, the viscosity variation has no significant influence on the Coriolis force-based instability. Numerical results confirm that a momentous destabilization is possible by aid of the Coriolis force via generating secondary flow inside the channel. Interestingly, the roll cells corresponding to the instabilities at lower time constants exhibit the existence of two distinct vortices, and the centre of the stronger one is essentially settled towards the unstable "stratified" region. Moreover, for a higher value of the time constant, only one vortex occupies the entire channel. This in turn, may turn out to be of fundamental importance in realizing new instability regimes facilitating efficient mixing in rotationally actuated fluidic devices deployed for biochemical analysis and medical diagnostics.

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Section: Numerical Validationcontrasting

confidence: 93%

Section: Stability Curves and Critical Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coriolis force-based instability of a shear-thinning microchannel flow

2020

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“…Recently, instabilities of single-phase flow in different geometries have also been investigated in the inertial regime with the aim to enhance fluid mixing [ 17 , 18 ]. In this article, we use linear stability analysis and lattice Boltzmann simulations to investigate the viscosity-driven instability of a multi-component microfluidic flow at finite Reynolds numbers.…”

Section: Introductionmentioning

confidence: 99%

Instability of a liquid sheet with viscosity contrast in inertial microfluidics

Patel

Stark

2021

Eur. Phys. J. E

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Flows at moderate Reynolds numbers in inertial microfluidics enable high throughput and inertial focusing of particles and cells with relevance in biomedical applications. In the present work, we consider a viscosity-stratified three-layer flow in the inertial regime. We investigate the interfacial instability of a liquid sheet surrounded by a density-matched but more viscous fluid in a channel flow. We use linear stability analysis based on the Orr–Sommerfeld equation and direct numerical simulations with the lattice Boltzmann method (LBM) to perform an extensive parameter study. Our aim is to contribute to a controlled droplet production in inertial microfluidics. In the first part, on the linear stability analysis we show that the growth rate of the fastest growing mode $$\xi ^{*}$$ ξ ∗ increases with the Reynolds number $$\text {Re}$$ Re and that its wavelength $$\lambda ^{*}$$ λ ∗ is always smaller than the channel width w for sufficiently small interfacial tension $$\Gamma $$ Γ . For thin sheets we find the scaling relation $$\xi ^{*} \propto mt^{2.5}_{s}$$ ξ ∗ ∝ m t s 2.5 , where m is viscosity ratio and $$t_{s}$$ t s the sheet thickness. In contrast, for thicker sheets $$\xi ^{*}$$ ξ ∗ decreases with increasing $$t_s$$ t s or m due to the nearby channel walls. Examining the eigenvalue spectra, we identify Yih modes at the interface. In the second part on the LBM simulations, the thin liquid sheet develops two distinct dynamic states: waves traveling along the interface and breakup into droplets with bullet shape. For smaller flow rates and larger sheet thicknesses, we also observe ligament formation and the sheet eventually evolves irregularly. Our work gives some indication how droplet formation can be controlled with a suitable parameter set $$\{\lambda ,t_{s},m,\Gamma ,\text {Re}\}$$ { λ , t s , m , Γ , Re } . Graphical Abstract

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Review article: Microscale evaporative cooling technologies for high heat flux microelectronics devices: Background and recent advances

Nahar

Guye

et al. 2021

Applied Thermal Engineering

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Rotational instabilities in microchannel flows

Cited by 13 publications

References 51 publications

Coriolis force-based instability of a shear-thinning microchannel flow

Coriolis force-based instability of a shear-thinning microchannel flow

Instability of a liquid sheet with viscosity contrast in inertial microfluidics

Review article: Microscale evaporative cooling technologies for high heat flux microelectronics devices: Background and recent advances

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