Hostname: page-component-8448b6f56d-cfpbc Total loading time: 0 Render date: 2024-04-17T17:31:36.291Z Has data issue: false hasContentIssue false
  • English
  • Français

The unsteady quasi-vortex-lattice method with applications to animal propulsion

Published online by Cambridge University Press:  19 April 2006

C. E. Lan
C. E. Lan
Affiliation:
Department of Aerospace Engineering, University of Kansas
Get access Rights & Permissions [Opens in a new window]

Abstract

In the early theoretical study of aquatic animal propulsion either the two-dimensional theory or the large aspect-ratio theory has been generally used. Only recently has the unsteady lifting-surface theory with the continuous loading approach been applied to the study of this problem by Chopra & Kambe (1977). Since it is well known that the continuous loading approach is difficult to extend to general configurations, a new quasi-continuous loading method, applicable to general configurations and yet accurate enough for practical applications, is developed in this paper. The method is an extension of the steady version of Lan (1974) and is particularly suitable for predicting the unsteady lead-edge suction during harmonic motion.

The method is applied to the calculation of the propulsive efficiency and thrust for some swept and rectangular planforms by varying the phase angles between the pitching and heaving motions. It is found that with the pitching axis passing through the trailing edge of the root chord and the reduced frequency k equal to 0·75 the rectangular planform is quite sensitive in performance to the phase angles and may produce drag instead of thrust. These characteristics are not shared by the swept planforms simulating the lunate tails. In addition, when the pitching leads the heaving motion by 90°, the phase angle for nearly maximum efficiency, the planform inclination caused by pitching contributes to the propulsive thrust over a large portion of the swept planform, while, for the rectangular planform, only drag is produced from the planform normal force at k = 0·75. It is also found that the maximum thrust is not produced with maximum efficiency for all planforms considered. The theory is then applied to the study of dragonfly aerodynamics. It is shown that the aerodynamically interacting tandem wings of the dragonfly can produce high thrust with high efficiency if the pitching is in advance of the flapping and the hindwing leads the forewing with some optimum phase angle. The responsible mechanism allows the hindwing to extract wake energy from the forewing.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 93 , Issue 4 , 29 August 1979 , pp. 747 - 765
Copyright
© 1979 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Albano, E. & Rodden, W. P. 1969 A.I.A.A. J. 7, 279, 2169.
Bennett, A. G. 1970 Ph.D. thesis, University of Illinois.
Bosch, H. 1972 Diplom-Ingenieur Thesis, Technical University, Munich.
Chadwick, L. E. 1940 Bull. Brooklyn Entomological Soc. 35, 109.
Chopra, M. G. 1974 Swimming and Flying in Nature, vol. 2 (ed. T. Y. Wu et al.), p. 635. Plenum Press.
Chopra, M. G. & Kambe, T. 1977 J. Fluid Mech. 79, 49.
Davies, D. E. 1963 Aero. Res. Counc. E. & M. no. 3409.
Hertel, H. 1966 Structure-Form-Movement. New York: Reinhold.
Jordan, P. F. 1976 Z. Flugwiss. 24, 205.
Kálmán, T. P., Giesing, J. P. & Rodden, W. P. 1970 J. Aircraft 7, 574.
Lan, C. E. 1974 J. Aircraft 11, 518.
Lan, C. E. 1975 Univer. Kansas Center Res. Inc., Lawrence, Kansas, Tech. Rep. KU — FRL–400.
Lan, C. E. 1976 N.A.S.A. SP–405, paper no. 21.
Lan, C. E. & Lamar, J. E. 1977 N.A.S.A. Tech. Note D–8513.
Laschka, B. 1975 AGARD — R–645.
Lighthill, M. J. 1970 J. Fluid Mech. 44, 265.
Pringle, J. W. S. 1957 Insect Flight. Cambridge University Press.
Richardson, J. R. 1955 Aero Res. Counc. R. & M. no. 3157.
Sparenberg, J. A. & Wiersma, A. K. 1974 Swimming and Flying in Nature, vol. 2 (ed. T. Y. Wu et al.), p. 891. Plenum Press.
Stahl, B., Kálmán, T. P., Giesing, J. P. & Rodden, W. P. 1968 Douglas Aircraft Co., U.S.A. Rep. DAC–67201.
Wu, T. Y. 1971 J. Fluid Mech. 46, 521.
Wu, T. Y. 1972 J. Ship Res. 14, 66.