Interactions between turbulent open channel flow, power and the wake of an axial-flow marine turbine

I. Introduction Until recently, an understanding of the range of scales of turbulent flow and its dynamic interaction with the performance and wake characteristics of axial-flow marine hydrokinetic turbines was lacking. Advancing this area of knowledge within the field of marine and hydrokinetic energy research, development, and deployment will lead to more efficient turbine operations and reduced cost of energy. Laboratory experiments were carried out at St. Anthony Falls Laboratory (SAFL) at the University of Minnesota (UMN) to a) investigate the performance and wake characteristics in a nearly fully developed turbulent open-channel flow, and b) study the effect of energetic coherent motions on the performance and wake characteristics of a model axial-flow hydrokinetic turbine. The measurements provide novel insights into the interaction of the surrounding turbulent environment and turbine power characteristics, details on near-and far-field wake characteristics, and the role of strong energetic coherent motions on turbine power fluctuations, tip vortex stability, and mean flow recovery in the turbine wake. Implications of these findings can be directly applied towards the efficient operation of hydrokinetic turbines in natural waterways.