Hydrodynamic Optimization of Cross-flow Turbines with Large Chord to Radius Ratios

INTRODUCTION Cross-flow turbines present several advantages over axial flow types for power generation from moving water. First, the rectangular form factor is well suited to take advantage of the hydrokinetic energy often concentrated in shallow channels. This form factor presents an opportunity to construct arrays with high blockage (ratio of swept area to channel cross-sectional area), potentially increasing energy extraction beyond the Betz limit for unconfined flows [1]. Second, in bidirectional tidal flows, yaw control is unnecessary. Thirdly, for high-solidity cross-flow turbines, the maximum blade speed is typically lower than axial flow turbines, reducing the risk of cavitation, acoustic pollution, and harmful interactions between devices and marine fauna. Though the foil kinematics in a cross-flow turbine exhibit just one degree of freedom, the resulting fluid dynamics are complex and highly dependent on turbine geometric parameters [2], [3]. In this study we examine the performance implications of altering the blade pitch angle and the number of blades on crossflow turbines.