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

Simulations of laminar flow past a superhydrophobic sphere with drag reduction and separation delay
Simulations of laminar flow past a superhydrophobic sphere with drag reduction and separation delay
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%.
1070-6631
1-16
Gruncell, B.
ce124772-ddfb-4c3b-91fe-eef686af7f6c
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Mchale, G.
07342075-4853-4b61-9d00-a5d9b2a41e54
Gruncell, B.
ce124772-ddfb-4c3b-91fe-eef686af7f6c
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Mchale, G.
07342075-4853-4b61-9d00-a5d9b2a41e54

Gruncell, B., Sandham, N.D. and Mchale, G. (2013) Simulations of laminar flow past a superhydrophobic sphere with drag reduction and separation delay. Physics of Fluids, 25, 1-16. (doi:10.1063/1.4801450).

Record type: Article

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%.

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More information

Published date: 16 April 2013
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 360899
URI: http://eprints.soton.ac.uk/id/eprint/360899
ISSN: 1070-6631
PURE UUID: db7d34f8-8658-4291-90e9-ccd14276c801
ORCID for N.D. Sandham: ORCID iD orcid.org/0000-0002-5107-0944

Catalogue record

Date deposited: 08 Jan 2014 12:44
Last modified: 21 Nov 2021 02:47

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Contributors

Author: B. Gruncell
Author: N.D. Sandham ORCID iD
Author: G. Mchale

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