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Lunate-Tail Swimming Propulsion

  • M. G. Chopra

Abstract

The non-uniform motion of a thin wing of finite-aspect ratio, with rounded leading edge and sharp trailing edge, executing heaving and pitching oscillations at zero mean lift, characterizing the horizontal lunate tail of a cetacean mammal, has been investigated. These very oscillations turned through 90° to become horizontal motions of sideslip and yaw characterize the vertical lunate tails of the fast swimming Percomorphi fishes. An oscillating vortex sheet consisting of streamwise and spanwise components is shed to trail behind the wing and it is the streamwise component resulting from the finiteness of the wing that makes this study a generalization of the two-dimensional treatment of lunate-tail propulsion by Lighthill (1970). Dependence of the forward thrust and hydromechanical propulsive efficiency on the aspect ratio, reduced frequency, feathering parameter, and the position of the pitching axis has been studied. The possibility of the use of this analysis to the study of the wing making finite amplitude motion has also been discussed.

Keywords

Vortex Wake Suction Force Thrust Coefficient Pitching Axis Propulsive Efficiency 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 1975

Authors and Affiliations

  • M. G. Chopra
    • 1
  1. 1.University of CambridgeCambridgeEngland

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