Issue 23, 2024

Heterogeneity-induced retraction in viscoelastic fluids following cessation of flow

Abstract

Complex fluids including colloidal suspensions, microgels, and entangled wormlike micelles (WLMs) can develop heterogeneous flow regions under imposed steady shear. In some of these systems, the evolution to this flow state from rest is accompanied by flow reversal – when a portion of the fluid moves opposite to the imposed flow direction. Flow reversal was proposed to occur in shear startup when (1) the fluid has significant elasticity, and (2) the flow becomes heterogeneous immediately following the stress overshoot [McCauley et al., J. Rheol., 2023, 67, 661–681]. To verify this hypothesis, a new method is developed for measuring flow heterogeneity. Upon cessation of the imposed flow, elasticity and flow heterogeneity cause retraction of the fluid, which is quantified with particle tracking velocimetry. Flow is stopped at key times during shear startup in two systems: a gel-like WLM that exhibits flow reversal before heterogeneous flow and a viscoelastic, fluid-like WLM that does not. The degree of flow heterogeneity is inferred from the shape and magnitude of velocity profiles measured during retraction. Flow heterogeneity develops earlier in gel-like WLMs – supporting the proposed flow reversal criteria. For comparison, heterogeneous Couette flows described with the upper-convected Maxwell or Germann–Cook–Beris models are analyzed. These theoretical flow problems confirm that stark differences in rheological properties across the flow geometry can cause significant fluid retraction and reproduce key features of the experimentally observed retraction. This new method can be used to extract quantitative information about spatially heterogeneous flows in viscoelastic complex fluids, whether or not flow reversal occurs.

Graphical abstract: Heterogeneity-induced retraction in viscoelastic fluids following cessation of flow

Supplementary files

Article information

Article type
Paper
Submitted
11 Cʼhwe. 2024
Accepted
21 Mae 2024
First published
22 Mae 2024

Soft Matter, 2024,20, 4567-4582

Heterogeneity-induced retraction in viscoelastic fluids following cessation of flow

P. J. McCauley, S. Kumar and M. A. Calabrese, Soft Matter, 2024, 20, 4567 DOI: 10.1039/D4SM00203B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements