Publication Detail

Forces on Oscillating Foils for Propulsion and Maneuvering

Douglas A Read, Franz Hover, Michael Triantafyllou
21 pp.
MITSG 03-30J
$4.00 DOM

Experiments were performed on an oscillating foil to assess its performance in producing large forces for propulsion and effective maneuvering. First, experiments on a harmonically heaving and pitching foil were performed to determine its propulsive efficiency under conditions of significant thrust production, as function of the principal parameters: the heave amplitude, Strouhal number, angle of attack, and phase angle between heave and pitch. Planform area thrust coefficients of 2.4 were recorded for 35 degree maximum angle of attack and efficiencies of up to 71.5% were recorded for 15 degree maximum angle of attack. A plateau of good efficiency, in the range of 50—60%, is noted. A phase angle of 90—100 degrees between pitch and heave is found to produce the best thrust performance. Also, the introduction of higher harmonics in the heave motion, so as to ensure a sinusoidal variation in the angle of attack produced much higher thrust coefficient at high Strouhal numbers. Second, experiments on a harmonically oscillating foil with a superposed pitch bias, as well as experiments on impulsively moving foils in still water, were conducted to assess the capability of the foil to produce large lateral forces for maneuvering. Mean side force coefficients of up to 5.5, and instantaneous lift coefficients of up to 15 were recorded, demonstrating an outstanding capability for maneuvering force production.

type: Technical reports

Parent Project

Project No.: 2001-RT-2/RD-13
Title: Biomimetic Rigid Hull Vehicle with Flapping Foils for Enhanced Agility in the Surf Zone and Cluttered Environments