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A simple fluid-flow model of ground effect on hovering

Published online by Cambridge University Press:  19 April 2006

James Lighthill
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Abstract

Hoverming motions, by which an animal (or a helicopter) in stationary fluid generates a downflow to support its weight, entail energy costs that include the induced power (power supplied to that downflow). The simplest classical model for induced power is the actuator-disk model. This paper shows how a relatively insignificant modification can be made to that model to make it aerodynamically self-consistent. The modified simple model of the downflow may be evaluated in fluid that either is unbounded or is bounded below by horizontal ground. Comparison of the calculated induced powers in the two cases (even though made in this paper not for the true axisymmetric flow patterns but for the corresponding two-dimensional flow patterns) appears to give a more satisfactory analysis than was previously available of the observed reduction of induced power associated with proximity to the ground.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 93 , Issue 4 , 29 August 1979 , pp. 781 - 797
Copyright
© 1979 Cambridge University Press

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References

Batchelor, G. K. 1967 An Introduction to Fluid Dynamics. Cambridge University Press.
Blake, R. W. 1979 The energetics of hovering in mandarin fish (Synchropus picturatus). To appear in J. exp. Biol.
Bramwell, A. R. S. 1976 Helicopter Dynamics. London: Edward Arnold.
Glauert, H. 1935 Airplane propellers, vol. IV, div. L of Aerodynamic Theory (ed. W. F. Durand). Springer.
Knight, M. & Hefner, R. A. 1941 Analysis of ground effect on the lifting rotor. Nat. Adv. Comm. Aeron. Tech. Note 835.Google Scholar
Lamb, H. 1932 Hydrodynamics (6th ed.). Cambridge University Press. Also New York: Dover (1945).
Lighthill, J. 1975 Aerodynamic aspects of animal flight. In Swimming and Flying in Nature (2 vols., ed. T. Y. Wu, C. J. Brokaw and C. Brennen), pp. 423–91. New York: Plenum Press.
Lighthill, J. 1977 Introduction to the scaling of aerial locomotion. In Scale Effects in Animal Locomotion (ed. T. J. Pedley), pp. 365–404. London: Academic Press
Rayner, J. M. V. 1979 A vortex theory of animals flight. Part 1. The vortex wake of a hovering animal. J. Fluid Mech. 91, 397–730.Google Scholar
Theodobsen, T. 1969 Theory of static propellers and helicopter rotors. Proc. 25th Ann Nat. Forum Amer. Helicopter Soc. p. 236.
Weis-Fogh, T. 1973 Quick estimates of flight fitness in hovering animals, including novel mechanisms for lift production. J. Exp. Biol. 59, 169–230.Google Scholar
Zbrozek, J. 1950 Ground effect on the lifting rotor. Aero. Res. Counc. Rep. and Memor. no. 2347. London: Her Majesty's Stationery Office.Google Scholar