Wake measurement behind a loaded vertical axis hydrokinetic turbine in field test

Continuous high frequency velocity field measurements were conducted in wake of a 5 kW vertical axis hydrokinetic turbine (VAHT). An Acoustic Doppler Velocimetry probe (ADV) measured flow velocity at a sampling rate of 16 Hz. Velocity measurements were done on freewheeling and also for various electric loads up to 1300 W on the turbine generator. Measurements were also done while turbine was being pulled out of the water. Results show a slight increase in mean velocity as loads on the turbine decrease. A significant increase in mean velocity was measured by removing turbine out of water. Power curve shows that the turbine was operating at higher tip speed ratios than the maximum performance point.