Numerical study of the effect of channel aspect ratio on particle focusing in acoustophoretic devices

Abstract Acoustophoretic microfluidic devices are promising non-contact and high-throughput tools for particle manipulation. Although the effectiveness of this technique has been widely demonstrated for applications based on micrometer-sized particles, the manipulation and focusing of sub-micrometer ones is challenging due to the presence of acoustic streaming. In this article, our study has the aim to investigate and understand which geometrical parameters could be changed to limit the acoustic streaming effect. We numerically study the well-known rectangular cross section of a microfluidic channel and perform a parametric study of the aspect ratio for several particle sizes. The efficiency of the focusing, is explored for different sized particles in order to identify a trend for which the acoustic streaming does not drastically influence the focusing motion of the particles. The possibility to efficiently separate different solid components in liquid suspensions, i.e. the whole blood, is crucial for all applications that require a purified medium such as plasmapheresis or an increase of the concentration of specific subpopulation as the outcome, such as proteomics, cancer biomarker detections and extracellular vesicles separation.

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A Numerical Study of Dean Instability in Non-Newtonian Fluids

Journal of Fluids Engineering ◽

10.1115/1.2136926 ◽

2005 ◽

Vol 128 (1) ◽

pp. 34-41 ◽

Cited By ~ 23

Author(s):

H. Fellouah ◽

C. Castelain ◽

A. Ould El Moctar ◽

H. Peerhossaini

Keyword(s):

Aspect Ratio ◽

Cross Section ◽

Power Law ◽

Numerical Study ◽

Rectangular Cross Section ◽

Newtonian Fluids ◽

Dean Number ◽

Bingham Number ◽

Curved Channels ◽

Power Law Index

We present a numerical study of Dean instability for non-Newtonian fluids in a laminar 180deg curved-channel flow of rectangular cross section. A methodology based on the Papanastasiou model (Papanastasiou, T. C., 1987, J. Rheol., 31(5), pp. 385–404) was developed to take into account the Bingham-type rheological behavior. After validation of the numerical methodology, simulations were carried out (using FLUENT CFD code) for Newtonian and non-Newtonian fluids in curved channels of square or rectangular cross section and for a large aspect and curvature ratios. A criterion based on the axial velocity gradient was defined to detect the instability threshold. This criterion was used to optimize the grid geometry. The effects of curvature and aspect ratio on the Dean instability are studied for all fluids, Newtonian and non-Newtonian. In particular, we show that the critical value of the Dean number decreases with increasing curvature ratio. The variation of the critical Dean number with aspect ratio is less regular. The results are compared to those for Newtonian fluids to emphasize the effect of the power-law index and the Bingham number. The onset of Dean instability is delayed with increasing power-law index. The same delay is observed in Bingham fluids when the Bingham number is increased.

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GS52 Numerical Study of the Micromixer Using the Taylor-Dean Flow : Effect of the Channel Aspect Ratio

The Proceedings of the Fluids engineering conference ◽

10.1299/jsmefed.2015._gs52-1_ ◽

2015 ◽

Vol 2015 (0) ◽

pp. _GS52-1_-_GS52-3_

Author(s):

Toshihiko KAWABE ◽

Yasutaka HAYAMIZU ◽

Shinichiro YANASE ◽

Takeshi GONDA ◽

Shinichi MORITA ◽

...

Keyword(s):

Aspect Ratio ◽

Numerical Study ◽

Flow Effect ◽

Dean Flow ◽

Channel Aspect Ratio

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Flow in Slowly Varying Microchannels of Rectangular Cross-Section

Volume 1: Symposia, Parts A, B and C ◽

10.1115/fedsm2009-78183 ◽

2009 ◽

Author(s):

Mohsen Akbari ◽

David Sinton ◽

Majid Bahrami

Keyword(s):

Cross Section ◽

Numerical Study ◽

Rectangular Cross Section ◽

Three Dimensional ◽

Numerical Data ◽

Arbitrary Cross Section ◽

Fully Developed Flow ◽

Deviation Factor ◽

Channel Aspect Ratio ◽

Compact Models

Laminar fully developed flow in streamwise-periodic microchannels of rectangular cross-section has been studied in this work. Based on the lubrication approximation, an analytical approach is proposed for the frictional flow resistance. Using the analytical model developed for straight channels of arbitrary cross-section, compact models are developed for linear and sinusoidal wall shapes. The models are then examined with two asymptotic two-dimensional flows of: (a) very narrow and (b) very tall channels and compared with the available experimental and numerical data in the literature. An independent numerical study is also performed to evaluate the proposed models for the three-dimensional flow case. Effects of the channel aspect ratio and deviation factor on the pressure drop are also investigated. Results for the three-simensional flow show that the proposed compact models capture the trend of the numerical data with good accuracy.

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A Triangular Double Layer Microchannel Heat Sink: Effect of Parallel and Counter Flow

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1115.433 ◽

2015 ◽

Vol 1115 ◽

pp. 433-439

Author(s):

Hazli Manaf ◽

Shugata Ahmed ◽

Mirghani I. Ahmed ◽

M.N.A. Hawlader

Keyword(s):

Reynolds Number ◽

Aspect Ratio ◽

Heat Sink ◽

Numerical Study ◽

Parallel Flow ◽

Microchannel Heat Sink ◽

Counter Flow ◽

Flow Configuration ◽

Aspect Ratios ◽

Channel Aspect Ratio

A numerical study is conducted by using ANSYS CFX 14.5, a commercial computational fluid dynamics program to predict the thermal performance of a counter and parallel flow on triangular double layered microchannel heat sink for various channel aspect ratios. Findings reveal that the counter flow configuration leads to a better heat transfer performance for low channel aspect ratio (α < 4) and higher Reynolds Number (Re > 700). For the parallel flow configuration, improved performance is normally shown when channel aspect ratio, α is more than 4 and lower Reynolds Number (Re < 700).

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Numerical study of a high-work low-aspect-ratio turbine stage

10.2514/6.1995-3043 ◽

1995 ◽

Cited By ~ 1

Author(s):

Suk Kim ◽

Robert Stubbs

Keyword(s):

Aspect Ratio ◽

Numerical Study ◽

Turbine Stage ◽

Low Aspect Ratio ◽

High Work

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Numerical Study on the Surface Plasmon Resonance Tunability of Spherical and Non-Spherical Core-Shell Dimer Nanostructures

Nanomaterials ◽

10.3390/nano11071728 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1728

Author(s):

Joshua Fernandes ◽

Sangmo Kang

Keyword(s):

Refractive Index ◽

Optical Properties ◽

Surface Plasmon Resonance ◽

Aspect Ratio ◽

Surface Plasmon ◽

Plasmon Resonance ◽

Shell Thickness ◽

Numerical Study ◽

Field Enhancement ◽

Core Shell

The near-field enhancement and localized surface plasmon resonance (LSPR) on the core-shell noble metal nanostructure surfaces are widely studied for various biomedical applications. However, the study of the optical properties of new plasmonic non-spherical nanostructures is less explored. This numerical study quantifies the optical properties of spherical and non-spherical (prolate and oblate) dimer nanostructures by introducing finite element modelling in COMSOL Multiphysics. The surface plasmon resonance peaks of gold nanostructures should be understood and controlled for use in biological applications such as photothermal therapy and drug delivery. In this study, we find that non-spherical prolate and oblate gold dimers give excellent tunability in a wide range of biological windows. The electromagnetic field enhancement and surface plasmon resonance peak can be tuned by varying the aspect ratio of non-spherical nanostructures, the refractive index of the surrounding medium, shell thickness, and the distance of separation between nanostructures. The absorption spectra exhibit considerably greater dependency on the aspect ratio and refractive index than the shell thickness and separation distance. These results may be essential for applying the spherical and non-spherical nanostructures to various absorption-based applications.

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Heat transfer characteristics of nanofluids from a sinusoidal corrugated cylinder placed in a square cavity

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211027208 ◽

2021 ◽

pp. 095440622110272

Author(s):

Salaika Parvin ◽

Nepal Chandra Roy ◽

Litan Kumar Saha ◽

Sadia Siddiqa

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Rayleigh Number ◽

Aspect Ratio ◽

Average Nusselt Number ◽

Numerical Study ◽

Heat Transfer Characteristics ◽

Number Range ◽

Transfer Characteristics ◽

Wide Range

A numerical study is performed to investigate nanofluids' flow field and heat transfer characteristics between the domain bounded by a square and a wavy cylinder. The left and right walls of the cavity are at constant low temperature while its other adjacent walls are insulated. The convective phenomena take place due to the higher temperature of the inner corrugated surface. Super elliptic functions are used to transform the governing equations of the classical rectangular enclosure into a system of equations valid for concentric cylinders. The resulting equations are solved iteratively with the implicit finite difference method. Parametric results are presented in terms of streamlines, isotherms, local and average Nusselt numbers for a wide range of scaled parameters such as nanoparticles concentration, Rayleigh number, and aspect ratio. Several correlations have been deduced at the inner and outer surface of the cylinders for the average Nusselt number, which gives a good agreement when compared against the numerical results. The strength of the streamlines increases significantly due to an increase in the aspect ratio of the inner cylinder and the Rayleigh number. As the concentration of nanoparticles increases, the average Nusselt number at the internal and external cylinders becomes stronger. In addition, the average Nusselt number for the entire Rayleigh number range gets enhanced when plotted against the volume fraction of the nanofluid.

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Influence of nozzle exit geometrical parameters on supersonic jet decay

International Journal of Turbo and Jet Engines ◽

10.1515/tjeng-2020-0047 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Prasanta Kumar Mohanta ◽

B. T. N. Sridhar ◽

R. K. Mishra

Keyword(s):

Aspect Ratio ◽

Nozzle Exit ◽

Ambient Air ◽

Schlieren Image ◽

Geometrical Parameters ◽

Image Study ◽

Aspect Ratios ◽

Core Length ◽

Supersonic Core Length ◽

The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

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