Surface gravity waves can significantly impact operating conditions for a marine current turbine, imparting unsteady velocities several orders of magnitude larger than the ambient turbulence. The influence of surface waves on the performance characteristics of a two-bladed horizontal axis marine current turbine was investigated experimentally in a large towing tank facility at the United States Naval Academy. The turbine model had a 0.8 m diameter (D) rotor with a NACA 63-618 cross section, which is Reynolds number independent with respect to lift coefficient in the operating range of Rec 4 x 105. The torque, thrust and rotational speed were measured at a range of tip speed ratios (TSR) from 5 < TSR < 11. Tests were performed at two rotor depths (1.3D and 2.25D) with and without waves. The average turbine performance characteristics were largely unchanged by depth or the presence of waves. However, tests with waves indicate large variations in thrust, rotational speed, and torque occurred with the passage of the wave. These results demonstrate the impact of surface gravity waves on power production and structural loading and suggest that turbines should be positioned vertically within the water column at a depth which maximizes power output while minimizing material fatigue.

Item Type:	Refereed Conference Paper
Keywords:	marine current turbine, tidal turbine, towing-tank experiments, surface gravity waves, fatigue loading, phase averaging
Research Division:	Engineering
Research Group:	Maritime Engineering
Research Field:	Ocean Engineering
Objective Division:	Energy
Objective Group:	Renewable Energy
Objective Field:	Tidal Energy
Author:	Walker, JM (Dr Jessica Walker)
ID Code:	86389
Year Published:	2013
Deposited By:	NC Maritime Engineering and Hydrodynamics
Deposited On:	2013-09-11
Last Modified:	2018-04-06
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