The Effect of Wave Parameters on the Performance of an Axial-Flow Hydrokinetic Turbine

The installation of axial-flow marine hydrokinetic turbines has been proposed for a variety of geographic locations, each with its own unique bathymetry, navigation requirements, environmental considerations, etc. One of the environmental factors that should be taken into consideration is the impact of waves. Surface waves impose an unsteady velocity that can significantly impact turbine power quality and structural loading. In order to further understanding of the impact of surface waves on turbine performance, a series of tests were performed in the small towing-tank facility at the U.S. Naval Academy. The turbine used in the present experiment was a 1:44 scale turbine measuring 0.45 m in diameter and featuring a NACA 4415 airfoil cross-section. Three testing phases, each focusing on a different wave parameter, were run. It was shown that increasing wave height or wavelength, while holding all other parameters constant increased the range of the resulting power coefficient. However, when wave energy per unit width was held constant, even while changing the other parameters, the resulting range of power coefficient values was nearly constant. This suggests that the energy of the wave, not the other parameters, has the most impact on turbine performance.