Date of Award

Spring 2025

Project Type

Thesis

Program or Major

Ocean Engineering

Degree Name

Master of Science

First Advisor

Martin Wosnik

Second Advisor

Thomas Lippmann

Third Advisor

Tracy Mandel

Abstract

The University of New Hampshire (UNH) and Ocean Renewable Power Company (ORPC) collaborated on the fabrication and testing of various blade shapes for cross-flow turbines (CFT). The UNH Wave and Tow Tank was used to test seven different 1.0 m scale, three-bladed cross-flow turbines with modified NACA 0018, 0021, and 0024 hydrofoil profiles with trailing edge thickness of 0.4%, 4.0%, and 8.0% of chord length. The effects of different foil thicknesses and trailing edge thicknesses on the performance of cross-flow turbines were examined motivated by factors such as manufacturability, cost, and structural integrity. These blades were constructed using a novel technique, with 3D-printed sections secured onto a rectangular steel core. Turbine performance was evaluated using metrics including rotor drag, torque, and lateral forces. The turbines were tested in an operating regime where performance approaches independence of Reynolds number, at Re_D>10^6 and Re_c,avg(C_P,max)=2.3 - 2.7*10^5. Thicker foils resulted in power coefficients of up to C_P,max = 0.284 at slightly lower tip speed ratios of TSR = 2.3 for NACA 0024 foils compared to thinner NACA 0018 foils with C_P,max = 0.256 peaking at TSR = 2.6. Thicker trailing edges resulted in lower power coefficients, such as C_P = 0.194 for a NACA 0018 foil with 8.0% of chord trailing edge. These results indicate that modifying the trailing edge to be thicker would not be a recommended method of reducing the costs of tidal turbine manufacturing. However, increasing the thickness of the foil is an acceptable way to increase the structural strength of blades while positively impacting performance.

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