Meeting Abstract

10.6  Tuesday, Jan. 4  Effects of Wing Morphology on Aerodynamics in Birds Revealed Using Revolving-Wing Models. TOBALSKE, B.W.*; WARRICK, D.R.; HEERS, A.M; DIAL, T.R.; CRANDELL, K.E.; Univ. of Montana; Oregon State Univ.; Univ. of Montana; Univ. of Utah; Univ of Montana bret.tobalske@mso.umt.edu

Previous empirical research has demonstrated that morphology has important consequences for aerodynamics during gliding flight, when the avian wing is translating through incident air uniformly from wing root to tip. More recent work modeling flapping by using a revolving-wing (propeller) model had indicated that performance is largely unaltered by dramatic differences in gross morphology (e.g. aspect ratio). We undertook a series of studies to further explore this counterintuitive observation. We used a propeller model to test for wing planform effects (i) among taxa (rufous hummingbird, chukar partridge, mallard duck, rock dove), (ii) among ontogentic stages in precocial species (chukar and duck), and (iii) between wing postures (downstroke and upstroke in rock dove). We observed differences in lift:drag (L:D) ratio among species (range 4 – 12) attributable in part to differences in aspect ratio, with maximum L:D occurring in hummingbirds. We also observed differences in peak coefficients of lift (1.5 – 2.1; greatest in ducks). Coefficients of lift and drag and L:D ratio increased throughout chukar and duck wing development; this trend was correlated with changes in feather morphology (e.g. vane asymmetry, barbule overlap) rather than changes in overall planform morphology. Upstroke posture produced almost half (49%) the average lift of downstroke at in vivo angles of attack, and exhibited a maximum L:D ratio of 2.5. Collectively, our results demonstrate that as in gliding flight, wing morphology and posture may significantly affect hovering and slow (flapping) flight performance. Supported by NSF grants IOS -0923606 and IOS-0919799.