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Air cushioning with a lubrication/ inviscid balance

Smith, F.T.; Li, L.; Wu, G.X.; (2003) Air cushioning with a lubrication/ inviscid balance. Journal of Fluid Mechanics , 482 pp. 291-318. 10.1017/S0022112003004063. Green open access


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The air cushioning effect in the gap between an almost inviscid body of water and a nearby solid wall (or another body of water) is studied theoretically and is found to depend on predominantly lubricating forces in the air, in certain applications. The situation in which the density and viscosity in air are taken as small compared with those in water is investigated. In this situation potential-flow dynamics in the water couples with lubrication behaviour in the air, leading to a nonlinear integro-differential system for the evolution of the interface. The numerical values of the main parameters are investigated and indicate a wide range of practical applications. Specifically, the lubrication/inviscid balance holds for typical global Reynolds numbers below the order of the viscosity ratio divided by the cube of the density ratio, i.e. below about 10$^{7}$ in the case of air and water; for Reynolds numbers of that order the lubrication behaviour is replaced by an unsteady boundary-layer response, whereas above that order formally the response is totally inviscid. A variety of spatio-temporal flow solutions are presented for the lubrication/inviscid system and these all indicate a relatively rapid closure of the gap, in a common form which is analysed.

Type: Article
Title: Air cushioning with a lubrication/ inviscid balance
Open access status: An open access version is available from UCL Discovery
DOI: 10.1017/S0022112003004063
Publisher version: http://dx.doi.org/10.1017/S0022112003004063
Language: English
Additional information: Published by Cambridge University Press
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/11745
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