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Aerodynamics of an aerofoil in transonic ground effect: numerical study at full-scale Reynolds numbers

Published online by Cambridge University Press:  27 January 2016

G. Doig ,
T. J. Barber ,
A. J. Neely  and
D. D. Myre
G. Doig*
Affiliation:
School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, Australia
T. J. Barber
Affiliation:
School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, Australia
A. J. Neely
Affiliation:
School of Aerospace, Civil and Mechanical Engineering, The University of New South Wales at the Australian Defence Force Academy, Canberra, Australia
D. D. Myre
Affiliation:
Aerospace Engineering Department, The United States Naval Academy, Maryland, USA
*
g.doig@unsw.edu.au
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Abstract

The potential positive effects of ground proximity on the aerodynamic performance of a wing or aerofoil have long been established, but at transonic speeds the formation of shock waves between the body and the ground plane would have significant consequences. A numerical study of the aerodynamics of an RAE2822 aerofoil section in ground effect flight was conducted at freestream Mach numbers from 0·5 to 0·9, at a range of ground clearances and angles of incidence. It was found that in general the aerofoil’s lifting capability was still improved with decreasing ground clearance up until the point at which a lower surface shock wave formed (most commonly at the lowest clearances). The critical Mach number for the section was reached considerably earlier in ground effect than it would be in freestream, and the buffet boundary was therefore also reached at an earlier stage. The flowfields observed were relatively sensitive to changes in any given variable, and the lower surface shock had a destabilising effect on the pitching characteristics of the wing, indicating that sudden changes in both altitude and attitude would be experienced during sustained transonic flight close to the ground plane. Since ground proximity hastens the lower surface shock formation, no gain in aerodynamic efficiency can be gained by flying in ground effect once that shock is present.

Type
Research Article
Information
The Aeronautical Journal , Volume 116 , Issue 1178 , April 2012 , pp. 407 - 430
Copyright
Copyright © Royal Aeronautical Society 2012 

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