A Numerical Study on Jet-Stream Propulsion of Oscillating Bodies

概要

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A Computational Fluid Dynamics (CFD) study on the jet-stream propulsion of rigidily oscillating and undulating bodies has been undertaken, by the unsteady solutions to the two-dimensional incompressible Navier-Stokes equations in conservative form, which are discretized with the finite volume method, using the pseudo-compressibility technique. Computational validation confirmed that the present method was capable to reasonably predict highly unsteady flows of biological problems. Numerical study on an oscillating hydrofoil (NACA 0012) reveals that there exists a problem of optimal propeller efficiency in generating the jet-stream in wake, but within a narrow region of the Strouhal numbers. Further analysis on a tadpole-shaped object and a fish-like body swimming in realistic kinematics, shows that the kinematics effectively produces a jet-stream propulsion with much higher propulsive efficiency than that of achieved by the oscillating hydrofoil. Investigation of Reynolds number effect for the undulatory swimming indicates that the propeller efficiency increases with increasing Reynolds number with no Re ceiling in generating the jet-stream.
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