The current drive to generate energy from sustainable renewable resources has led to an increased interest in generating power through exploiting the kinetic energy in faster flowing tidal streams. Much of the knowledge gained from the development of wind turbines has been applied to the tidal stream turbine. However, the hostile marine environment introduces new technological challenges. The tidal turbine operates under highly unsteady, turbulent flow conditions and the occurrence of marine biofouling adds further complication to the issue. The main objective of the present work is to advance the understanding of the effect marine fouling has on the unsteady hydrodynamic loading and performance of tidal turbine blade sections.
To investigate this challenging fluid phenomenon, a series of two-dimensional static and unsteady experiments were designed and conducted in the dynamic stall test rig at the University of Glasgow's Handley Page wind tunnel facility. The test matrix was constructed to cover the full operating envelope of a blade from MW-scale turbines, and included three thicker, cambered blade sections from two radial positions on the blade - a NACA 63-619 and two proprietary AHH designs. Chordwise integrated force and pitching moment coefficients were obtained from surface pressure measurements for three representative blade fouling configurations: an aerodynamically clean baseline; a light level of widely distributed microfouling roughness; and the addition of macrofouling with a single instrumented barnacle protuberance.
This work has generated what is believed to be a unique database of unsteady tidal turbine blade section performance and, more importantly, the negative impact marine biofouling is likely to have on these investigated parameters. The approach followed through the work has been to assess the impact of marine biofouling on the individual blade sections and then assess the consequences of marine biofouling on the turbine by combining the blade section findings in a BEMT numerical performance model.