Meeting Abstract
101.3 Sunday, Jan. 6 Efficiency of lift production in six species of hawk moths HENNINGSSON, P.*; BOMPHREY, R. J.; Univ. of Oxford, UK; Univ. of Oxford, UK per.henningsson@zoo.ox.ac.uk
The efficiency of lift production is important for all flying animals because it directly influences the limits of performance. For both fixed-wing vehicles and flapping animals the efficiency of lift production, span efficiency (ei), can be estimated using quantitative flow diagnostics and fundamental aerodynamic theory. Wings generating lift in the most aerodynamically efficient way do so by deflecting the oncoming airflow uniformly across the span, creating a uniform spanwise induced flow distribution. Any deviation from uniformity is associated with an extra cost as induced drag increases. By quantifying how large this deviation is, the increase in drag and the reduction in span efficiency can be calculated. We used high speed stereo Particle Image Velocimetry (stereo-PIV) with a repetition rate of 1 kHz to capture the near wake from six species of hawk moths flying tethered in a wind tunnel in forward flight. The selected species represent a range in wingspan from 40mm to 110mm (2.75 times) and in mass from 0.2g to 1.5g (7.5 times). From the high spatio-temporal resolution flow fields we extracted downwash distributions behind the animals and calculated instantaneous values of ei throughout the wingbeat cycle as well as multi-wingbeat averages. Here we present how span efficiency differs between the six moth species and discuss the effect of force generation and kinematics.
