PERFORMANCE AND NEAR-WAKE MEASUREMENTS FOR A VERTICAL AXIS TURBINE AT MODERATE REYNOLDS NUMBER

Experiments were performed with a 1 m diameter, 1 m tall three-bladed vertical axis turbine in a towing tank. Rotor power and drag (or thrust) were measured at a tow speed of 1 m/s, corresponding to a turbine diameter Reynolds number Re-D = 10(6) and an approximate blade chord Reynolds number Re-c = lambda U(infinity)c/v similar to 10(5). Mechanical exergy efficiency estimates were computed from power and drag measurements using an actuator disk approach. Characteristics of the turbine's near-wake were measured at one turbine diameter downstream. Variation of all three mean and fluctuating velocity components in the vertical and cross-stream directions were measured at peak turbine power output via acoustic Doppler velocimeter. The effect of tip speed ratio on near-wake mean velocity was observed at the turbine center line. Transverse profiles of mean velocity, fluctuating velocity, and Reynolds stresses were also measured at the turbine's quarter height for two tip speed ratios of interest. Results are compared and contrasted with previous lower Reynolds number studies, and will provide a detailed data set for validation of numerical models.