Abstract
ABSTRACTTwo-dimensional computational fluid dynamics (CFD) is applied to better understand the effects of wing cross-sectional morphology on flow field and force production. This study investigates the influence of wing cross-section on insect scale flapping flight performance, for the first time, using a morphologically representative model of a bee (Bombus pensylvanicus) wing. The bee wing cross-section was determined using a micro-computed tomography scanner. The results of the bee wing are compared with flat and elliptical cross-sections, representative of those used in modern literature, to determine the impact of profile variation on aerodynamic performance. The flow field surrounding each cross-section and the resulting forces are resolved using CFD for a flight speed range of 1 to 5 m/s. A significant variation in vortex formation is found when comparing the ellipse and flat plate with the true bee wing. During the upstroke, the bee and approximate wing cross-sections have a much shorter wake structure than the flat plate or ellipse. During the downstroke, the flat plate and elliptical cross-sections generate a single leading edge vortex, while the approximate and bee wings generate numerous, smaller structures that are shed throughout the stroke. Comparing the instantaneous aerodynamic forces on the wing, the ellipse and flat plate sections deviate progressively with velocity from the true bee wing. Based on the present findings, a simplified cross-section of an insect wing can misrepresent the flow field and force production. We present the first aerodynamic study using a true insect wing cross-section and show that the wing corrugation increases the leading edge vortex formation frequency for a given set of kinematics.
Highlights
Biological flapping flight is an extraordinarily complex phenomenon, which occurs across multiple phylums of the animal kingdom, with wide disparities in the balance between aerodynamic performance and efficiency (Ellington, 1985; Walker et al, 2014; Mao and Gang, 2003; Miyake, 2008)
Flow characteristics The flow fields at τ=11.25 (τ=0.25 in Fig. S2) and 11.68 are shown in Figs 1 and 2, respectively, to gain insight into the underlying aerodynamics that manifests as differences in lift and drag
Four different representations of an insect wing cross-section were compared using the cross-section from a micro-computed tomography scan of an actual bee wing and an approximation of that bee wing cross-section
Summary
Biological flapping flight is an extraordinarily complex phenomenon, which occurs across multiple phylums of the animal kingdom, with wide disparities in the balance between aerodynamic performance and efficiency (Ellington, 1985; Walker et al, 2014; Mao and Gang, 2003; Miyake, 2008). The powered flight of insects is inherently unique for its combination of mechanical simplicity and high flapping frequency, resulting in a complicated vortical flow field. These flight characteristics result in agile and maneuverable flight. Bees are of particular interest because of the utilization of humuli to attach their front and hind wings together during flight, causing the front and hind wings to move as one body (Basibuyuk and Quicke, 1997). Bee aerodynamics is uniquely applicable to the future direction of micro-air vehicle (MAV) research as another possible solution to low velocity, low Reynolds number, large payload flight (Ma et al, 2012; Yan et al, 2001; Bai et al, 2007)
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