Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Science in Ocean Engineering

Department

Ocean Engineering

First Advisor

Stephen C. Licht

Abstract

Force production from an underwater flapping foil near a solid boundary was experimentally studied in order to characterize the three dimensional flow effects. The experimental apparatus consisted of a dual canister system that actuated a harmonic oscillation of a NACA 0012 rectangular planform foil in pitch and roll. The flapping foil was towed at constant velocity through water in a tow tank in both a freestream and near boundary condition while forces and torques were measured by a six axis dynamometer. Experimental tests showed that for the chosen kinematic conditions and foil geometry, average maximum instantaneous lift forces increased 16-29% in ground effect compared to the freestream. It was also found that for the kinematic conditions evaluated there is a 9% increase in mean thrust production when in ground effect. Additionally, tests were performed at varying altitudes from the solid boundary with foil down biasing in an attempt to characterize the three dimensional flow changes as a function of height above bottom. Preliminary results have shown that the strength of ground effect observed through force sensing can be modulated through foil biasing and potentially provide useful information for altitude control of a flapping foil powered autonomous underwater vehicle (AUV).

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