沙漠蝗虫通过翅振产生的时变跨越效率研究
The flight performance of animals depends greatly on the efficacy with which they generate aerodynamicforces. Accordingly, maximum range, load-lifting capacity and peak accelerations duringmanoeuvres are all constrained by the efficiency of momentum transfer to the wake. Here, we usehigh-speed particle image velocimetry (1 kHz) to record flow velocities in the near wake of desertlocusts (Schistocerca gregaria, Forska?l).We use the measured flow fields to calculate time-varyingspan efficiency throughout the wing stroke cycle. The locusts are found to operate at a maximumspan efficiency of 79 per cent, typically at a plateau of about 60 per cent for the majority of thedownstroke, but at lower values during the upstroke. Moreover, the calculated span efficienciesare highest when the largest lift forces are being generated (90% of the total lift is generatedduring the plateau of span efficiency) suggesting that the combination of wing kinematics andmorphology in locust flight perform most efficiently when doing the most work.