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Transport in Viscoelastic Fluids
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Transport in Viscoelastic Fluids

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Non-Newtonian and Complex Fluids".

Deadline for manuscript submissions: closed (31 August 2022) | Viewed by 6930

Special Issue Editor

Prof. Dr. Robert Handler

E-Mail Website
Guest Editor
Department of Mechanical Engineering, George Mason University, Fairfax, VA 22030, USA
Interests: turbulence; viscoelastic fluids; drag reduction; direct numerical simulations
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Much attention has been devoted to technological advances related to miniaturization, with a particular emphasis on micro-scale and milli-scale devices, many of which involve the flow of fluids. The field of microfluidics has grown out of a need to understand the transport of heat, mass, and momentum in these devices. Research in this field is driven by a wide variety of important applications, such as those in biotechnology, biosensor development, and in the design of micro-electro-mechanical systems. As the length scale of these devices is reduced, the physical processes which were applicable at larger scales are reduced in importance, as other forces and processes become dominant. These physical forces and processes include capillarity, buoyancy, fluid elasticity, and electro-chemical processes. Recently, instabilities due solely to viscoelasticity have been observed in these flows, in spite of the dominance of viscosity. In particular, a chaotic flow called elastic-turbulence has been found in viscoelastic fluid flows. In this topic, we seek contributions that emphasize the effects of fluid viscoelasticity in promoting the transport of mass, momentum, and heat in such devices at the micro-scale and milli-scale. Theoretical, experimental, and computational approaches are all welcome.

Prof. Dr. Robert Handler
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
  • viscoelasticity
  • instabilities
  • elastic-turbulence
  • polymers

Published Papers (3 papers)

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Research

20 pages, 5351 KiB  
Article
Characterization of Effective Diffusion within Viscoelastic Fluids with Elastic Instabilities
by Valerie Hietsch, Phil Ligrani and Mengying Su
Fluids 2022, 7(1), 33; https://doi.org/10.3390/fluids7010033 - 13 Jan 2022
Cited by 2 | Viewed by 1840
Abstract
We considered effective diffusion, characterized by magnitudes of effective diffusion coefficients, in order to quantify mass transport due to the onset and development of elastic instabilities. Effective diffusion coefficient magnitudes were determined using different analytic approaches, as they were applied to tracked visualizations [...] Read more.
We considered effective diffusion, characterized by magnitudes of effective diffusion coefficients, in order to quantify mass transport due to the onset and development of elastic instabilities. Effective diffusion coefficient magnitudes were determined using different analytic approaches, as they were applied to tracked visualizations of fluorescein dye front variations, as circumferential advection was imposed upon a flow environment produced using a rotating Couette flow arrangement. Effective diffusion coefficient results were provided for a range of flow shear rates, which were produced using different Couette flow rotation speeds and two different flow environment fluid depths. To visualize the flow behavior within the rotating Couette flow environment, minute amounts of fluorescein dye were injected into the center of the flow container using a syringe pump. This dye was then redistributed within the flow by radial diffusion only when no disk rotation was used, and by radial diffusion and by circumferential advection when disk rotation was present. Associated effective diffusion coefficient values, for the latter arrangement, were compared to coefficients values with no disk rotation, which were due to molecular diffusion alone, in order to quantify enhancements due to elastic instabilities. Experiments were conducted using viscoelastic fluids, which were based on a 65% sucrose solution, with different polymer concentrations ranging from 0 ppm to 300 ppm. Associated Reynolds numbers based on the fluid depth and radially averaged maximum flow velocity ranged from 0.00 to 0.5. The resulting effective diffusion coefficient values for different flow shear rates and polymer concentrations quantified the onset of elastic instabilities, as well as significant and dramatic changes to local mass transport magnitudes, which are associated with the further development of elastic instabilities. Full article
(This article belongs to the Special Issue Transport in Viscoelastic Fluids)
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26 pages, 6084 KiB  
Article
Numerical Simulation and Linearized Theory of Vortex Waves in a Viscoelastic, Polymeric Fluid
by Robert A. Handler and Michael J. Buckingham
Fluids 2021, 6(9), 325; https://doi.org/10.3390/fluids6090325 - 09 Sep 2021
Cited by 2 | Viewed by 1933
Abstract
In a high viscosity, polymeric fluid initially at rest, the release of elastic energy produces vorticity in the form of coherent motions (vortex rings). Such behavior may enhance mixing in the low Reynolds number flows encountered in microfluidic applications. In this work, we [...] Read more.
In a high viscosity, polymeric fluid initially at rest, the release of elastic energy produces vorticity in the form of coherent motions (vortex rings). Such behavior may enhance mixing in the low Reynolds number flows encountered in microfluidic applications. In this work, we develop a theory for such flows by linearizing the governing equations of motion. The linear theory predicts that when elastic energy is released in a symmetric manner, a wave of vorticity is produced with two distinct periods of wave motion: (1) a period of wave expansion and growth extending over a transition time scale, followed by (2) a period of wave translation and viscous decay. The vortex wave speeds are predicted to be proportional to the square root of the initial fluid tension, and the fluid tension itself scales as the viscosity. Besides verifying the predictions of the linearized theory, numerical solutions of the equations of motion for the velocity field, obtained using a pseudo-spectral method, show that the flow is composed of right- and left-traveling columnar vortex pairs, called vortex waves for short. Wave speeds obtained from the numerical simulations are within 1.5% of those from the linear theory when the assumption of linearity holds. Vortex waves are found to decay on a time scale of the order of the vortex size divided by the solution viscosity, in reasonable agreement with the analytical solution of the linearized model for damped vortex waves. When the viscoelastic fluid is governed by a nonlinear spring model, as represented by the Peterlin function, wave speeds are found to be larger than the predictions of the linear theory for small polymer extension lengths. Full article
(This article belongs to the Special Issue Transport in Viscoelastic Fluids)
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20 pages, 4270 KiB  
Article
Migration and Alignment of Three Interacting Particles in Poiseuille Flow of Giesekus Fluids
by Bing-Rui Liu, Jian-Zhong Lin and Xiao-Ke Ku
Fluids 2021, 6(6), 218; https://doi.org/10.3390/fluids6060218 - 11 Jun 2021
Cited by 2 | Viewed by 2170
Abstract
Effect of rheological property on the migration and alignment of three interacting particles in Poiseuille flow of Giesekus fluids is studied with the direct-forcing fictitious domain method for the Weissenberg number (Wi) ranging from 0.1 to 1.5, the mobility parameter ranging [...] Read more.
Effect of rheological property on the migration and alignment of three interacting particles in Poiseuille flow of Giesekus fluids is studied with the direct-forcing fictitious domain method for the Weissenberg number (Wi) ranging from 0.1 to 1.5, the mobility parameter ranging from 0.1 to 0.7, the ratio of particle diameter to channel height ranging from 0.2 to 0.4, the ratio of the solvent viscosity to the total viscosity being 0.3 and the initial distance (y0) of particles from the centerline ranging from 0 to 0.2. The results showed that the effect of y0 on the migration and alignment of particles is significant. The variation of off-centerline (y0 ≠ 0) particle spacing is completely different from that of on-centerline (y0 = 0) particle spacing. As the initial vertical distance y0 increased, the various types of particle spacing are more diversified. For the off-centerline particle, the change of particle spacing is mainly concentrated in the process of cross-flow migration. Additionally, the polymer extension is proportional to both the Weissenberg number and confinement ratio. The bigger the Wi and confinement ratio is, the bigger the increment of spacing is. The memory of shear-thinning is responsible for the reduction of d1. Furthermore, the particles migrate abnormally due to the interparticle interaction. Full article
(This article belongs to the Special Issue Transport in Viscoelastic Fluids)
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