Slip length and drag reduction of superhydrophobic surfaces in shear-thinning fluid flows.

Zhang, Linsheng, Zhou, Weixing, Crick, Colin R, Ng, Henry C-H ORCID: 0000-0003-4926-7622 and Poole, Robert J ORCID: 0000-0001-6686-4301 (2025) Slip length and drag reduction of superhydrophobic surfaces in shear-thinning fluid flows. Journal of colloid and interface science, 685. pp. 468-475. ISSN 0021-9797, 1095-7103

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Abstract

<h4>Hypothesis</h4>We hypothesise that superhydrophobic surfaces can achieve effective interfacial slip and drag reduction even under non-Newtonian, shear-thinning fluid flows. Unlike Newtonian fluids, where slip is primarily influenced by viscosity and surface tension, we anticipate that the shear-thinning nature of these fluids may enhance slip length and drag reduction.<h4>Experiments and numerical analysis</h4>The superhydrophobic surfaces used in this study, featuring a dual-scale random topography, were fabricated via a spray coating process, and low-concentration xanthan gum solutions (50-250 ppm) were used as model shear-thinning fluids of low elasticity. Drag reduction was experimentally measured using a rheometric cone-and-plate system, while slip length was calculated through a newly developed integral expression for power-law fluids.<h4>Findings</h4>Experimental results revealed a significant increase in slip length for xanthan gum solutions compared to distilled water, indicating that shear-thinning effects lead to substantial increases in slip length. Specifically, xanthan gum solutions with a power-law index of approximately 0.8 achieved over a 25% increase in slip length compared to equivalent Newtonian fluids. Furthermore, analytical and numerical analyses confirmed that shear-thinning fluids enhance the slip effect over superhydrophobic surfaces while shear-thickening fluids diminish it. The strong agreement between theoretical and experimental results underscores the potential of superhydrophobic surfaces to reduce drag in shear-thinning fluid flows.

Item Type:	Article
Uncontrolled Keywords:	Superhydrophobic surfaces, Drag reduction, Slip length, Shear-thinning fluids
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Engineering
Depositing User:	Symplectic Admin
Date Deposited:	03 Feb 2025 08:43
Last Modified:	28 Feb 2026 14:12
DOI:	10.1016/j.jcis.2025.01.152
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3190024
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