Effects of upstream structures on power output and wake evolution of hydrokinetic turbine

Hydrokinetic turbines (HKTs) have the potential to generate cheap and reliable power by harnessing the kinetic energy of rivers. In order to optimally deploy an array of turbines in the field, an accurate model of wake evolution and power output is needed. However, most previous experimental HKT studies took place under homogeneous incoming flow conditions, only varying velocity and turbulent intensity. The effect of upstream structures such as piles, boulders, or vegetation patches on the power output and wake evolution of HKTs has received limited attention. These structures create incoming flow with strong vertical and horizontal velocity gradients, a broad range of turbulence and vorticity length scales, and energetic coherent motions. These conditions may more accurately mimic flow found in a real river. To assess the impact of the upstream structures, Acoustic Doppler velocimetry (ADV) and particle image velocimetry (PIV), were used to measure the flow around full-scale models of horizontal- and vertical-axis HKTs in the open racetrack flume at the Ecohydraulics and Ecomorphodynamics Laboratory (EEL) at the University of Illinois Urbana-Champaign. The wake evolution under these heterogeneous incoming flows was compared to existing wake models, and a new model sought to incorporate their effects. This research will help inform the optimal deployment location of HKTs in the field.