An experimental investigation of Reynolds number effects on the aerodynamics of insect-like revolving wings

Abstract

Revolving wing studies for insect-like wing planforms provide useful insights into the aerodynamic characteristics within the primary translational phase of a flapping wing stroke. This study aims to quantify the combined effects of wing planform shape and Reynolds number on the aerodynamic force coefficients measured for insect-like revolving wings. Six wing models, representing two aspect ratios and three wing centroid locations, are systematically tested at three Reynolds numbers, Re = 5x103, 10x103, 15x103, approximately representative of the flight conditions of bumblebees, hawkmoths, and hummingbirds, respectively. Thickness-to-chord ratio is kept constant for all wing models. Our experiments revealed a number of useful insights; however, the two most notable outcomes are: (1) the lift curve slope is considerably influenced by the wing centroid location and Reynolds number with the increase in both leading to lower lift curve slope values; and (2) the zero-lift drag coefficient is significantly affected by aspect ratio with the decrease in aspect ratio from three to two leading to approximately three times higher zero-lift drag coefficient values.