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Experimental study of the transitional flow of a sphere located at the free surface

Experimental study of the transitional flow of a sphere located at the free surface
Experimental study of the transitional flow of a sphere located at the free surface
The investigation of transitional flow past a sphere at the free surface is a challenging problem due to a complex interaction between the free surface and evolution of the boundary layer and resultant separation on the sphere’s surface. An increased knowledge about the fluid phenomena around bluff bodies would be of benefit to the design of offshore structures and ships’ bulbous bows. In this paper, experiments conducted in a towing tank environment are presented for a 225mm-diameter sphere towed at the free surface across the diameter based Reynolds number range 1.6 x105 < Re < 3.8 x105. Measurements of the total resistance using a bespoke dynamometer are combined with above-water photographs to provide further insight. An abrupt change in flow regime was observed as speed increased to reach Re ~ 3.5 x105. The bow breaking wave grows until transition occurs into a smooth flow over the top of the sphere. This change in flow condition resulted in a 60% decrease in total resistance. This paper considers why this drag crisis phenomenon takes place around Re ~ 2.6 - 3.6 x105, which is similar to single-phase flows. The inertial effect of the free surface deformation as opposed to the influence of the laminar to turbulent boundary layer transition is investigated.
1-7
James, Marion
aaf059b7-05ec-4560-be35-7fc1bfe46f07
Forrester, Alex
176bf191-3fc2-46b4-80e0-9d9a0cd7a572
Hudson, Dominic
3814e08b-1993-4e78-b5a4-2598c40af8e7
Taunton, Dominic
10bfbe83-c4c2-49c6-94c0-2de8098c648c
Turnock, Stephen
d6442f5c-d9af-4fdb-8406-7c79a92b26ce
James, Marion
aaf059b7-05ec-4560-be35-7fc1bfe46f07
Forrester, Alex
176bf191-3fc2-46b4-80e0-9d9a0cd7a572
Hudson, Dominic
3814e08b-1993-4e78-b5a4-2598c40af8e7
Taunton, Dominic
10bfbe83-c4c2-49c6-94c0-2de8098c648c
Turnock, Stephen
d6442f5c-d9af-4fdb-8406-7c79a92b26ce

James, Marion, Forrester, Alex, Hudson, Dominic, Taunton, Dominic and Turnock, Stephen (2015) Experimental study of the transitional flow of a sphere located at the free surface. 9th International Workshop on Ship and Marine Hydrodynamics, Glasgow, United Kingdom. 25 - 26 Aug 2015. pp. 1-7 .

Record type: Conference or Workshop Item (Paper)

Abstract

The investigation of transitional flow past a sphere at the free surface is a challenging problem due to a complex interaction between the free surface and evolution of the boundary layer and resultant separation on the sphere’s surface. An increased knowledge about the fluid phenomena around bluff bodies would be of benefit to the design of offshore structures and ships’ bulbous bows. In this paper, experiments conducted in a towing tank environment are presented for a 225mm-diameter sphere towed at the free surface across the diameter based Reynolds number range 1.6 x105 < Re < 3.8 x105. Measurements of the total resistance using a bespoke dynamometer are combined with above-water photographs to provide further insight. An abrupt change in flow regime was observed as speed increased to reach Re ~ 3.5 x105. The bow breaking wave grows until transition occurs into a smooth flow over the top of the sphere. This change in flow condition resulted in a 60% decrease in total resistance. This paper considers why this drag crisis phenomenon takes place around Re ~ 2.6 - 3.6 x105, which is similar to single-phase flows. The inertial effect of the free surface deformation as opposed to the influence of the laminar to turbulent boundary layer transition is investigated.

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More information

e-pub ahead of print date: 27 August 2015
Venue - Dates: 9th International Workshop on Ship and Marine Hydrodynamics, Glasgow, United Kingdom, 2015-08-25 - 2015-08-26
Organisations: Engineering Science Unit

Identifiers

Local EPrints ID: 382010
URI: http://eprints.soton.ac.uk/id/eprint/382010
PURE UUID: 7344cb32-dee5-4ea4-a0f5-ec85fde63536
ORCID for Marion James: ORCID iD orcid.org/0000-0002-6964-4598
ORCID for Dominic Hudson: ORCID iD orcid.org/0000-0002-2012-6255
ORCID for Dominic Taunton: ORCID iD orcid.org/0000-0002-6865-089X
ORCID for Stephen Turnock: ORCID iD orcid.org/0000-0001-6288-0400

Catalogue record

Date deposited: 15 Oct 2015 13:03
Last modified: 15 Mar 2024 03:00

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Contributors

Author: Marion James ORCID iD
Author: Alex Forrester
Author: Dominic Hudson ORCID iD
Author: Dominic Taunton ORCID iD
Author: Stephen Turnock ORCID iD

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