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Flow over a glider canopy

Published online by Cambridge University Press:  27 January 2016

A. S. Jonker ,
J. J. Bosman ,
E. H. Mathews  and
L. Liebenberg
A. S. Jonker
Affiliation:
School of Mechanical and Nuclear Engineering, North-West University (Potchefstroom campus), Potchefstroom, South Africa
J. J. Bosman
Affiliation:
School of Mechanical and Nuclear Engineering, North-West University (Potchefstroom campus), Potchefstroom, South Africa
E. H. Mathews
Affiliation:
Centre for Research and Continued Engineering Development, North-West University (Pretoria campus), Lynnwood Ridge, South Africa
L. Liebenberg*
Affiliation:
Centre for Research and Continued Engineering Development, North-West University (Pretoria campus), Lynnwood Ridge, South Africa
*
[email protected]
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Abstract

In order to minimise drag, the front part of most modern glider fuselages is shaped so that laminar flow is preserved to a position close to the wing-to-fuselage junction. Experimental investigations on a full-scale JS1 competition glider however revealed that the laminar boundary layer in fact trips to turbulent flow at the fuselage-to-canopy junction position, increasing drag. This is possibly due to ventilation air leaking from the cockpit to the fuselage surface through the canopy seal, or that the gap is merely too large and therefore trips the boundary layer to turbulent flow. The effect of air leaking from the fuselage-to-canopy gap as well as the size of the gap was thus investigated with the use of computational fluid dynamics. It was found that if air was leaking through this gap the boundary layer would be tripped from laminar to turbulent flow. It was also found that the width of the canopy-to-fuselage gap plays a significant role in the preservation of laminar flow. If the gap is less than 1mm wide, the attached boundary layer is able to negotiate the gap without being tripped to turbulent flow, while if the gap is 3mm and wider, it will be tripped from laminar to turbulent flow. The work shows that aerodynamic drag on a glider can be significantly minimised by completely sealing the fuselage-to-canopy gap and by ensuring a seal gap-width of less than 1mm.

Type
Research Article
Information
The Aeronautical Journal , Volume 118 , Issue 1204 , June 2014 , pp. 669 - 682
Copyright
Copyright © Royal Aeronautical Society 2014 

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