Simulations of laminar flow past a superhydrophobic sphere with drag reduction and separation delay

Gruncell, Brian, Sandham, Neil and McHale, Glen (2013) Simulations of laminar flow past a superhydrophobic sphere with drag reduction and separation delay. Physics of Fluids, 25 (4). 043601. ISSN 1070-6631

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Official URL: http://dx.doi.org/10.1063/1.4801450

Abstract

Superhydrophobic surfaces have potential for reducing hydrodynamic drag by combining a structured surface and hydrophobicity to retain a lubricating air layer (plastron) at the surface. In the present contribution, numerical simulations of laminar flow past a superhydrophobic sphere are conducted using a two-phase flow representation. The results show drag reductions in Stokes flow of up to 19% for an air-water system, in agreement with previous analytic work, and demonstrate an increased effect as the Reynolds number is increased to 100. Drag reductions of up to 50% are achieved due to reduction in viscous drag and suppression of separation by the plastron, resulting in a narrower wake. To explore a less idealised model of the plastron, baffles have also been introduced to simulate the support of a plastron by roughness elements. The baffles lead to the attached vortex regime no longer being suppressed, but separation is delayed and drag reductions are evident in comparison to a solid sphere. Increasing the area solid fraction results in a diminished drag reduction due to the plastron, however drag reductions of up to 15% can still be achieved with solid fractions of 10%.

Item Type: Article
Uncontrolled Keywords: drag, superhydrophobic
Subjects: F200 Materials Science
F300 Physics
H100 General Engineering
Department: Faculties > Engineering and Environment > Physics and Electrical Engineering
Related URLs:
Depositing User: Glen McHale
Date Deposited: 02 Jan 2014 11:29
Last Modified: 15 May 2017 15:16
URI: http://nrl.northumbria.ac.uk/id/eprint/14935

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