Mixing process of immiscible fluids in microchannels

Bălan, C.; Broboana, Diana; Bălan, Corneliu

doi:10.1016/j.ijheatfluidflow.2010.06.008

Cited by 17 publications

(6 citation statements)

References 33 publications

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“…[ 45,46 ] For pressure‐driven channel flows, such as the ones investigated in this work, where one characteristic velocity would determine the Er of the channel flow, [ 51 ] it is important to note that locally in the channel cross section there is a velocity gradient and as a consequence the shear rate varies locally. [ 52 ] Thus, near the channel walls, where the velocity gradients are high, viscous forces would be expected to dominate resulting in a director orientation in the flow direction. In contrast, in the center of the flow domain the local shear rates are low, liquid crystal elastic forces are dominant.…”

Section: Resultsmentioning

confidence: 99%

In Situ Visualization of the Structural Evolution and Alignment of Lyotropic Liquid Crystals in Confined Flow

Rodríguez-Palomo

Lutz‐Bueno

Cao

et al. 2021

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Self‐assembled materials such as lyotropic liquid crystals offer a wide variety of structures and applications by tuning the composition. Understanding materials behavior under flow and the induced alignment is wanted in order to tailor structure related properties. A method to visualize the structure and anisotropy of ordered systems in situ under dynamic conditions is presented where flow‐induced nanostructural alignment in microfluidic channels is observed by scanning small angle X‐ray scattering in hexagonal and lamellar self‐assembled phases. In the hexagonal phase, the material in regions with high extensional flow exhibits orientation perpendicular to the flow and is oriented in the flow direction only in regions with a high enough shear rate. For the lamellar phase, a flow‐induced morphological transition occurs from aligned lamellae toward multilamellar vesicles. However, the vesicles do not withstand the mechanical forces and break in extended lamellae in regions with high shear rates. This evolution of nanostructure with different shear rates can be correlated with a shear thinning viscosity curve with different slopes. The results demonstrate new fundamental knowledge about the structuring of liquid crystals under flow. The methodology widens the quantitative investigation of complex structures and identifies important mechanisms of reorientation and structural changes.

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Section: Resultsmentioning

confidence: 99%

In Situ Visualization of the Structural Evolution and Alignment of Lyotropic Liquid Crystals in Confined Flow

Rodríguez-Palomo

Lutz‐Bueno

Cao

et al. 2021

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“…Soleymani et al 9 simulated the effects of the angle of the Y‐mixer on the pressure drop and the mixing efficiency at Re = 120 and showed that both quantities increased with increasing angles between 15° and 105°. Balan et al 16 simulated the mixing of two immiscible liquids for Re in the range of 0.01–200 in a Y‐mixer ( θ = 75°) and showed that interfacial forces controlled the vortex formation and shapes. Shi et al 17 numerically studied the mixing of reactive flows, using a segregation coefficient at Re = 845 in Y‐mixers, and showed that maximum mixing occurred at ∼60°.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Flow Patterns and Concentration Profiles in Y‐Mixers

et al. 2016

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The fluid flow patterns and associated concentration fields in Y-mixers are investigated using lattice Boltzmann method-based models. The focus lies on the impact of the mixing angle on the flow and concentration fields, with the mixing angle varying between acute (q = 10°) and obtuse (q = 130°) angles. Residence time distributions are determined to study the effect of the angles on the mixing and velocity patterns, in particular, different flow regimes, i.e., stratified laminar, vortex, and engulfment flow. The results from the simulations are validated with literature data and found to be in good agreement. Maximum mixing occurs in the 100°obtuse-angle Y-mixer, attributed to the extensive engulfment of flows in the mixing channel.

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“…Fully three-dimensional velocimetry techniques now find increasing use in microfluidic investigations [1,2]. Some recent examples of three-dimensional three-component (referred to as 3D-3C) velocity measurements for micro flows include (a) mixing at the T-junction of micro channels (Balan et al [3], Lindken et al [4]), (b) an evaporating droplet (Pereira et al [5]), (c) a liquid immersion droplet on a moving substrate (Kim et al [6]), (d) the behavior of swimming micro-organisms (Choi et al [7]) and (e) Brownian motion of a particle (Kihm et al [8], Park et al [9]).…”

Section: Introductionmentioning

confidence: 99%

Comparison of Tomo-PIV and 3D-PTV for microfluidic flows

Kim

Westerweel

Elsinga

2012

Meas. Sci. Technol.

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Two 3D-3C velocimetry techniques for micro-scale measurements are compared: tomographic particle image velocimetry (Tomo-PIV) and 3D particle-tracking velocimetry (3D-PTV). Both methods are applied to experimental data from a confined shear-driven liquid droplet over a moving surface. The droplet has 200 μm height and 2 mm diameter. Micro 3D-PTV and Tomo-PIV are used to obtain the tracer particle distribution and the flow velocity field for the same set of images. It is shown that the reconstructed particle distributions are distinctly different, where Tomo-PIV returns a nearly uniform distribution over the height of the volume, as expected, and PTV reveals a clear peak in the particle distribution near the plane of focus. In Tomo-PIV, however, the reconstructed particle peak intensity decreases in proportion to the distance from the plane of focus. Due to the differences in particle distributions, the measured flow velocities are also different. In particular, we observe Tomo-PIV to be in closer agreement with mass conservation. Furthermore, the random noise level is found to increase with distance to the plane of focus at a higher rate for 3D-PTV as compared to Tomo-PIV. Thus, for a given noise threshold value, the latter method can measure reliably over a thicker volume.

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Mixing process of immiscible fluids in microchannels

Cited by 17 publications

References 33 publications

In Situ Visualization of the Structural Evolution and Alignment of Lyotropic Liquid Crystals in Confined Flow

In Situ Visualization of the Structural Evolution and Alignment of Lyotropic Liquid Crystals in Confined Flow

Numerical Investigation of Flow Patterns and Concentration Profiles in Y‐Mixers

Comparison of Tomo-PIV and 3D-PTV for microfluidic flows

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