摘要

Novel flow visualization methods using smoke tracers and flow streamers were developed for investigating rotor tip vortices generated by a 2.5-MW MOD-2 wind turbine through full-scale field experiments. Smoke tracers were released from smoke generators tethered to the turbine tower and placed just downwind of the rotor or launched from model rockets. Flow streamers made of long and thin crepe papers and/or fabric strips were tethered to a parafoil kite. Each method reveals different perspectives of the tip vortices. Several vortex phenomena have been discovered from the new field results. These phenomena were not revealed in small-scale laboratory experiments because of failure to achieve dynamic similarity. Of particular interest are the physical separation of the helical vortex trajectories and the wind turbine wake and reversal of the tip vortex. A core-within-a-core is one of the dramatic scenes displayed by smoke tracers as the tip vortex retracts through its original course during vortex reversal.