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Unsteady aerodynamics of two interacting yacht sails in two-dimensional potential flow

Published online by Cambridge University Press:  16 December 2010

F. C. GERHARDT ,
R. G. J. FLAY  and
P. RICHARDS
F. C. GERHARDT
Affiliation:
Yacht Research Unit, Department of Mechanical Engineering, The University of Auckland, Private Bag 92019, Auckland, New Zealand
R. G. J. FLAY*
Affiliation:
Yacht Research Unit, Department of Mechanical Engineering, The University of Auckland, Private Bag 92019, Auckland, New Zealand
P. RICHARDS
Affiliation:
Yacht Research Unit, Department of Mechanical Engineering, The University of Auckland, Private Bag 92019, Auckland, New Zealand
*
†Email address for correspondence: [email protected]
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Abstract

In this paper, unsteady thin aerofoil theory is extended to the case of two interacting aerofoils that oscillate harmonically perpendicular to the direction of the incident flow. The two aerofoils represent the headsail and mainsail of a yacht that sails upwind in waves. The developed theory is validated against theoretical data from the literature and results from wind tunnel tests with rigid, high-aspect ratio sail models oscillating at reduced frequencies from k = 0 to k = 0.68. Good agreement is found between the predicted and measured chordwise pressure distributions. An application of the theory to the case of an International America's Cup Class yacht reveals that the time-varying components of the aerodynamic forces are small and that the thrust gain is minimal, i.e. only very little energy can be extracted from the unsteady flow about the sails. No attempt is made to investigate the influence of the flexibility of the sails, three-dimensional effects or phenomena related to dynamic stall.

JFM classification

Mathematical Foundations: Computational methods Vortex Flows: Vortex shedding Wakes/Jets: Wakes/Jets
Type
Papers
Information
Journal of Fluid Mechanics , Volume 668 , 10 February 2011 , pp. 551 - 581
Copyright
Copyright © Cambridge University Press 2010

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References

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