Waves 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 (1 December 2022) | Viewed by 1158

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Department of Mechanical Engineering, George Mason University, Fairfax, VA 22030, USA
Interests: turbulence; viscoelastic fluids; drag reduction; direct numerical simulations
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Dear Colleagues,

Considerable attention has been devoted to technological advances related to miniaturization, with particular attention to micro-scale and milli-scale devices, many of which involve the flow of fluids. Research in this field is driven by a wide variety of important applications, such as those in biotechnology, biosensor development, and the design of micro-electro mechanical systems. The discovery of elastic instabilities in viscoelastic microfluidic flows and related theoretical work have raised interest in the possibility that elastic waves may exist in these fluids. The existence of such waves may be important, not only for theoretical reasons, but may also have implications regarding enhanced transport in microflows. However, experimental evidence for these waves is scant. In this topic, we seek theoretical, experimental, and computational contributions that can elucidate the underlying physics of elastic waves in viscoelastic fluids.

Prof. Dr. Robert Handler
Guest Editor

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Keywords

  • vortex waves
  • elastic waves
  • microfluidics
  • viscoelasticity
  • instabilities
  • elastic turbulence
  • polymers

Published Papers (1 paper)

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Research

15 pages, 4592 KiB  
Article
Morphology of Anisotropic Banded Structures in an Emulsion under Simple Shear
by Jairo Eduardo Leiva Mateus, Marco Antonio Reyes Huesca, Federico Méndez Lavielle and Enrique Geffroy Aguilar
Fluids 2023, 8(9), 240; https://doi.org/10.3390/fluids8090240 - 25 Aug 2023
Viewed by 882
Abstract
The formation of flow-induced, oriented structures in two-phase systems, as in this study, is a phenomenon of considerable interest to the scientific and industrial sectors. The main difficulty in understanding the formation of bands of droplets is the simultaneous interplay of physicochemical, hydrodynamic, [...] Read more.
The formation of flow-induced, oriented structures in two-phase systems, as in this study, is a phenomenon of considerable interest to the scientific and industrial sectors. The main difficulty in understanding the formation of bands of droplets is the simultaneous interplay of physicochemical, hydrodynamic, and mechanical effects. Additionally, banded structure materials frequently show multiple length scales covering several decades as a result of complex time-dependent stress fields. Here, to facilitate understanding a subset of these structures, we studied water in oil emulsions and focused on the effects of three variables specifically: the confinement factor (Co=2R/H), the viscosity ratio (p), and the applied shear rate (γ˙). The confinement (Co) is the ratio between the drop’s diameter (2R) and the separation of (the gap between) the circular rotating disks (H) containing the emulsion. We carried out (a) observations of the induced structure under different simple shear rates, as well as (b) statistical and morphological analysis of these bands. At low shear rates, the system self-assembles into bands along the direction of the flow and stacked normal to the velocity gradient direction. At higher shear rates is possible to observe bands normal to the vorticity direction. Here, we show that a detailed analysis of the dynamics of the band structures is amenable, as well as measurements of flow field anomalies simultaneously observed. The local emulsion viscosity varies in time, increasing in regions of higher droplet concentration and subsequently inducing velocity components perpendicular to the main flow direction. Thus, the emulsion morphology evolves and changes macroscopically. A relatively plausible explanation is attributed to the competitive effects of coalescence and the rupture of drops, where p values less than one predominate coalescence. Full article
(This article belongs to the Special Issue Waves in Viscoelastic Fluids)
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