Aerodynamic Characteristics of Bristled Wings in Flapping Flight

Abstract

This study focuses on the aerodynamics of the smallest flying insects’ bristled wings. We measured and analyzed wing morphological data from 38 specimens of Mymaridae. Bristled wing flight was numerically simulated at Reynolds numbers from 1 to 80. The aerodynamic force, power, and efficiency of bristled wings using lift-based stroke, drag-based stroke, and clap-and-fling mechanism were evaluated. An unusual clap-and-fling pattern considering bristle crossing was first proposed. Our study shows that with a reduction in the wingspan of Mymaridae, the proportion of the wingtip bristled area increases. A lift-based stroke is superior to a drag-based stroke in terms of vertical force production and aerodynamic efficiency at 5 ≤ Re ≤ 20. Bristled wings employing the clap-and-fling mechanism achieve both vertical force and efficiency augmentation, while bristle crossing incurs a substantial horizontal force and contributes little to vertical force augmentation.

Fluid–structure interactions of bristled wings: the trade-off between weight and drag

“…Experimentally, with its rectangular design for the bristled strips, the reduced physical model ignored the diverse shapes found in biological wings (figure 1 a ), thus leaving a large design space unexplored. The experiments also neglected the complex flight kinematics used by bristled-winged insects [27,33,36,37]. However, as we have mentioned in §2, our results are relevant to drag-based flight mechanisms using bristled wings, given that drag at high angles of attack is the main source of lift and thrust [26,34–36].…”

“…The experiments also neglected the complex flight kinematics used by bristled-winged insects [27,33,36,37]. However, as we have mentioned in §2, our results are relevant to drag-based flight mechanisms using bristled wings, given that drag at high angles of attack is the main source of lift and thrust [26,34–36].…”

“…The smallest flying insects have been reported to flap their wings in a figure-of-eight cycle, where the wings are engaged at a large angle of attack for much of the stroke cycle [26,[34][35][36]. The aerodynamic force responsible for generating lift during the flapping motion arises primarily from the drag force acting in opposition to the wing motion.…”

“…Flow near the bristles and around the wing is difficult to visualize experimentally [42,43]. As such, computational models have been widely used to gather data on the dynamics of the shear layers between bristles due to flapping [45] and due to perturbation to steady steaming flow [46], and the changing force production and aerodynamic efficiency due to variations in bristle parameters [32,36,47,48].…”

“…In addition, the flight characteristics of several species of bristled-winged insects have been quantified by high-speed videos, allowing for analysis and numerical simulations of flight kinematics and aerodynamics at extremely small size scales [26,27,29–32]. These studies revealed that instead of the horizontal sweeping stroke used commonly by larger insects, miniature insects engage bristled wings in a figure-of-eight stroke cycle [26,30,33–36]. The Reynolds number ( Re ) of the bristled wing is usually estimated based on the wing chord length ( Re c ) and has been reported to be Rec=Ofalse(1false)–Ofalse(10false) [16,35,37].…”