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 aerodynamic
forces. Accordingly, maximum range, load-lifting capacity and peak accelerations during
manoeuvres are all constrained by the efficiency of momentum transfer to the wake. Here, we use
high-speed particle image velocimetry (1 kHz) to record flow velocities in the near wake of desert
locusts (Schistocerca gregaria, Forska˚l).We use the measured flow fields to calculate time-varying
span efficiency throughout the wing stroke cycle. The locusts are found to operate at a maximum
span efficiency of 79 per cent, typically at a plateau of about 60 per cent for the majority of the
downstroke, but at lower values during the upstroke. Moreover, the calculated span efficiencies
are highest when the largest lift forces are being generated (90% of the total lift is generated
during the plateau of span efficiency) suggesting that the combination of wing kinematics and
morphology in locust flight perform most efficiently when doing the most work. 德国LaVision PIV/PLIF粒子成像测速场仪 时间分辨粒子成像测速系统(TR-PIV) 自适应粒子成像测速场仪（PIV）