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Recent Advances in Single and Multiphase Flows in Microchannels, Volume...
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Recent Advances in Single and Multiphase Flows in Microchannels, Volume II

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: closed (31 August 2022) | Viewed by 13621

Special Issue Editor

Dr. Beatrice Pulvirenti

E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Bologna, viale Risorgimento, 2, 40136 Bologna, Italy
Interests: numerical methods; heat transfer; turbulent flows; two-phase flow; microchannels; micro-junctions
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Heat and mass transport in microchannels is key to diverse applications that span many disciplines in science and engineering, from mechanical, chemical, energy, and environmental engineering, to biological and medical science.

Notable examples range from the thermal management of power electronics to the mobilisation of pollutants in unsaturated soil, the capillary-cleaning of fouling and biofilms, microencapsulation for drug delivery, the medical treatment of diseased tissues, the deformability of cells in biofluids, and (bio)chemical microreactor technology, to name a few.

Within microchannels, unlike large-scale flows, phenomena such as viscous heating, surface tension, interfacial resistance to heat and mass transfer, van der Waals interactions, diffusiophoresis, and diffusioosmosis can have dominant effects on the transport mechanisms.

Although recent advances in microfabrication techniques such as micromilling, embossing technology, additive manufacturing, and photolithography have allowed substantial reduction in microchannel size and manufacturing cost, there is still a great deal of uncertainty in our understanding of the underlying flow physics.

Therefore, new insight into the governing flow/heat-transfer mechanisms at the microscale, required for the optimal development, design, and operation of the next-generation microfluidic devices, is the driving motivation of this Special Issue.

This Special Issue welcomes contributions that focus on recent developments in single and multiphase flows in microchannels, including but not restricted to gas–liquid, liquid–liquid, particle-laden, and colloidal-suspension flows; the impact of channel geometry on fluid dynamics and heat transfer; fundamental aspects of thin-film dynamics and evaporation; flow boiling heat transfer and critical heat flux; flow boiling instabilities in multimicrochannel evaporators; the enhancement of single-phase cooling; microstructured surfaces; thermally and surfactant-driven Marangoni flows; electrokinetics; diffusiophoresis; diffusioosmosis; and theoretical approaches such as lubrication theory and asymptotics.

We invite contributions in all areas of experimental and computational methods, multiscale models, and theoretical approaches that focus on the aforementioned mechanisms dominated by the microscale.

Dr. Beatrice Pulvirenti
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microfluidics
  • single-phase flow
  • multiphase flow
  • flow boiling
  • thin films
  • computational fluid mechanics
  • multiscale modelling

Published Papers (5 papers)

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Research

30 pages, 593 KiB  
Article
Stochastic Modeling of Particle Transport in Confined Geometries: Problems and Peculiarities
by Giuseppe Procopio and Massimiliano Giona
Fluids 2022, 7(3), 105; https://doi.org/10.3390/fluids7030105 - 12 Mar 2022
Cited by 4 | Viewed by 1921
Abstract
The equivalence between parabolic transport equations for solute concentrations and stochastic dynamics for solute particle motion represents one of the most fertile correspondences in statistical physics originating from the work by Einstein on Brownian motion. In this article, we analyze the problems and [...] Read more.
The equivalence between parabolic transport equations for solute concentrations and stochastic dynamics for solute particle motion represents one of the most fertile correspondences in statistical physics originating from the work by Einstein on Brownian motion. In this article, we analyze the problems and the peculiarities of the stochastic equations of motion in microfluidic confined systems. The presence of solid boundaries leads to tensorial hydrodynamic coefficients (hydrodynamic resistance matrix) that depend also on the particle position. Singularity issues, originating from the non-integrable divergence of the entries of the resistance matrix near a solid no-slip boundary, determine some mass-transport paradoxes whenever surface phenomena, such as surface chemical reactions at the walls, are considered. These problems can be overcome by considering the occurrence of non vanishing slippage. Added-mass effects and the influence of fluid inertia in confined geometries are also briefly addressed. Full article
(This article belongs to the Special Issue Recent Advances in Single and Multiphase Flows in Microchannels, Volume II)
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16 pages, 25287 KiB  
Article
Design and Numerical Simulation of Biomimetic Structures to Capture Particles in a Microchannel
by Lung-Jieh Yang, Vivek-Jabaraj Joseph, Neethish-Kumar Unnam and Balasubramanian Esakki
Fluids 2022, 7(1), 32; https://doi.org/10.3390/fluids7010032 - 12 Jan 2022
Cited by 2 | Viewed by 2949
Abstract
The study of separating different sizes of particles through a microchannel has been an interest in recent years and the primary attention of this study is to isolate the particles to the specific outlets. The present work highly focuses on the design and [...] Read more.
The study of separating different sizes of particles through a microchannel has been an interest in recent years and the primary attention of this study is to isolate the particles to the specific outlets. The present work highly focuses on the design and numerical analysis of a microchip and the microparticles capture using special structures like corrugated dragonfly wing structure and cilia walls. The special biomimetic structured corrugated wing is taken from the cross-sectional area of the dragonfly wing and cilia structure is obtained from the epithelium terminal bronchioles to the larynx from the human body. Parametric studies were conducted on different sizes of microchip scaled and tested up in the range between 2–6 mm and the thickness was assigned as 80 µm in both dragonfly wing structure and cilia walls. The microflow channel is a low Reynolds number regime and with the help of the special structures, the flow inside the microchannel is pinched and a sinusoidal waveform pattern is observed. The pinched flow with sinusoidal waveform carries the particles downstream and induces the particles trapped in desired outlets. Fluid particle interaction (FPI) with a time-dependent solver in COMSOL Multiphysics was used to carry out the numerical study. Two particle sizes of 5 µm and 20 µm were applied, the inlet velocity of 0.52 m/s with an inflow angle of 50° was used throughout the study and it suggested that: the microchannel length of 3 mm with corrugated dragonfly wing structure had the maximum particle capture rate of 20 µm at the mainstream outlet. 80% capture rate for the microchannel length of 3 mm with corrugated dragonfly wing structure and 98% capture rate for the microchannel length of 2 mm with cilia wall structure were observed. Numerical simulation results showed that the cilia walled microchip is superior to the corrugated wing structure as the mainstream outlet can conduct most of the 20 µm particles. At the same time, the secondary outlet can laterally capture most of the 5 µm particles. This biomimetic microchip design is expected to be implemented using the PDMS MEMS process in the future. Full article
(This article belongs to the Special Issue Recent Advances in Single and Multiphase Flows in Microchannels, Volume II)
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21 pages, 12171 KiB  
Article
Header Shape Effect on the Inlet Velocity Distribution in Cross-Flow Double-Layered Microchannel Heat Sinks
by Stefano Savino and Carlo Nonino
Fluids 2022, 7(1), 7; https://doi.org/10.3390/fluids7010007 - 24 Dec 2021
Cited by 2 | Viewed by 2213
Abstract
Counter-flow double-layered microchannel heat sinks are very effective for thermal control of electronic components; however, they require rather complicated headers and flow maldistribution can also play a negative role. The cross-flow configuration allows a much simpler header design and the thermal performance becomes [...] Read more.
Counter-flow double-layered microchannel heat sinks are very effective for thermal control of electronic components; however, they require rather complicated headers and flow maldistribution can also play a negative role. The cross-flow configuration allows a much simpler header design and the thermal performance becomes similar to that provided by the counter-flow arrangement if the velocity distribution in the microchannels is not uniform. The aim of this work is to show the possibility of achieving a favorable flow distribution in the microchannels of a cross-flow double-layered heat sink with an adequate header design and the aid of additional elements such as full or partial height baffles made of solid or porous materials. Turbulent RANS numerical simulations of the flow field in headers are carried out with the commercial code ANSYS Fluent. The flow in the microchannel layers is modeled as that in a porous material, whose properties are derived from pressure drop data obtained using an in-house FEM code. It is demonstrated that, with an appropriate baffle selection, inlet headers of cross-flow microchannel heat sinks yield velocity distributions very close to those that would allow optimal hotspot management in electronic devices. Full article
(This article belongs to the Special Issue Recent Advances in Single and Multiphase Flows in Microchannels, Volume II)
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29 pages, 8847 KiB  
Article
Shapes and Rise Velocities of Single Bubbles in a Confined Annular Channel: Experiments and Numerical Simulations
by Andrea Cioncolini and Mirco Magnini
Fluids 2021, 6(12), 437; https://doi.org/10.3390/fluids6120437 - 2 Dec 2021
Cited by 3 | Viewed by 3361
Abstract
Shapes and rise velocities of single air bubbles rising through stagnant water confined inside an annular channel were investigated by means of experiments and numerical simulations. Fast video imaging and image processing were used for the experiments, whilst the numerical simulations were carried [...] Read more.
Shapes and rise velocities of single air bubbles rising through stagnant water confined inside an annular channel were investigated by means of experiments and numerical simulations. Fast video imaging and image processing were used for the experiments, whilst the numerical simulations were carried out using the volume of fluid method and the open-source package OpenFOAM. The confinement of the annular channel did not affect the qualitative behavior of the bubbles, which exhibited a wobbling rise dynamic similar to that observed in bubbles rising through unconfined liquids. The effect of the confinement on the shape and rise velocity was evident; the bubbles were less deformed and rose slower in comparison with bubbles rising through unconfined liquids. The present data and numerical simulations, as well as the data collected from the literature for use here, indicate that the size, shape, and rise velocity of single bubbles are closely linked together, and prediction methods that fail to recognize this perform poorly. This study and the limited evidence documented in the literature indicate that the confinement effects observed in non-circular channels of complex shape are more complicated than those observed with circular tubes, and much less well understood. Full article
(This article belongs to the Special Issue Recent Advances in Single and Multiphase Flows in Microchannels, Volume II)
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24 pages, 5688 KiB  
Article
Computational Study of the Dynamics of the Taylor Bubble
by Evgenii L. Sharaborin, Oleg A. Rogozin and Aslan R. Kasimov
Fluids 2021, 6(11), 389; https://doi.org/10.3390/fluids6110389 - 29 Oct 2021
Cited by 5 | Viewed by 2466
Abstract
We perform high-resolution numerical simulations of three-dimensional dynamics of an elongated bubble in a microchannel at moderate Reynolds numbers up to 1800. For this purpose, we use the coupled Brinkman penalization and volume of fluid methods implemented in the open-source framework Basilisk. The [...] Read more.
We perform high-resolution numerical simulations of three-dimensional dynamics of an elongated bubble in a microchannel at moderate Reynolds numbers up to 1800. For this purpose, we use the coupled Brinkman penalization and volume of fluid methods implemented in the open-source framework Basilisk. The new results are validated with available experimental data and compared with previous numerical and theoretical predictions. We extend existing results to regimes with significant inertia, which are characterized by intense deformations of the bubble, including cases with azimuthal symmetry breaking. Various dynamical features are analyzed in terms of their spatiotemporal characteristics, such as frequencies and wavelengths of the bubble surface undulations and vortical structures in the flow. Full article
(This article belongs to the Special Issue Recent Advances in Single and Multiphase Flows in Microchannels, Volume II)
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