Extraction of Flow Energy by Fish and Birds in a Wavy Stream

  • Theodore Y. Wu
  • Allen T. Chwang


This paper makes an attempt to explore the possibility for birds and aquatic animals to extract intrinsic flow energy from a wavy (or even turbulent) stream for enhancing their locomotion through the fluid medium. Sea gulls and pelicans have been observed to skim ocean waves over a long distance without making noticeable flapping of their wings as in ordinary flight. In a study of migrating salmon, Osborne (1960) found that an increased flow rate in a swollen river did not slow down the salmon, while en route to spawn, by nearly as much a margin as would be predicted by the law of resistance in proportion to the square of their velocity relative to the flowing water. A few possible reasons have been proposed, including the prospect that the flow energy associated with the waves and eddies in a stream can be extracted and used to generate thrust for locomotion.


Primary Wave Optimum Motion Primary Flow Suction Force Thrust Coefficient 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Lang, T. G. and Daybell, D. A. 1963 Porpoise performance tests in a sea-water tank. NAVWEPS Rep. 8060, NOTS TP 3063. Naval Ordnance Test Station, China Lake, California.Google Scholar
  2. Lighthill, M. J. 1970 Aquatic animal propulsion of high hydro-mechanical efficiency. J. Fluid Mech. 44, 265–301.CrossRefGoogle Scholar
  3. Osborne, M. F.M. 1960 The hydrodynamical performance of migratory salmon. J. Exp. Biol. 38, 365–390.Google Scholar
  4. Wu, T. Y. 1971a Hydromechanics of swimming propulsion. Part 1. Swimming of a two-dimensional flexible plate at variable forward speeds in an inviscid fluid. J. Fluid Mech. 46, 337–355.CrossRefGoogle Scholar
  5. Wu, T. Y. 197lb Hydromechanics of swimming propulsion. Part 2. Some optimum shape problems. J. Fluid Mech. 46, 521–544.CrossRefGoogle Scholar
  6. Wu, T. Y. 1972 Extraction of flow energy by a wing oscillating in waves. J. Ship Res. 14, No. 1, 66–78.Google Scholar
  7. Wu, T. Y., Chwang, A. T. and Wang, P. K. C. 1972 Optimization problems in hydrofoil propulsion. In Optimization and Stability Problems in Continuum Mechanics, (P. K. C. Wang, ed.), Lecture notes in physics, 21, 38–62, Springer-Verlag.Google Scholar

Copyright information

© Springer Science+Business Media New York 1975

Authors and Affiliations

  • Theodore Y. Wu
    • 1
  • Allen T. Chwang
    • 1
  1. 1.California Institute of TechnologyPasadenaUSA

Personalised recommendations