Near Wake Dynamics of a two Cross-flow Turbine Array

Cross-flow turbines, also known as vertical-axis turbines, convert the kinetic energy in moving fluid to mechanical energy using blades that rotate about an axis perpendicular to the incoming flow. In these experiments, the performance and wake of a two-turbine array in a fence configuration (side-by-side) were characterized. The turbines were operated under coordinated control, characterized by synchronous rotation rates with a mean phase difference. Measurements were made with turbines co-rotating, counter-rotating with the blades advancing upstream at the array midline, and counter-rotating with the blades retreating downstream at the array midline. From the performance data, we found individual turbine and array efficiency to depend significantly on rotation direction and phase difference. Similar variations are observed in the wake and, using these data, we hypothesize how rotation direction and phase influence interactions between adjacent turbines.