Numerical investigation of an insect-scale flexible wing with a small amplitude flapping kinematics

Abstract

To maintain flight, insect-scale air vehicles must adapt to their low Reynolds number flight conditions and generate sufficient aerodynamic force. Researchers conducted extensive studies to explore the mechanism of high aerodynamic efficiency on such a small scale. In this paper, a centimeter-level flapping wing is used to investigate the mechanism and feasibility of whether a simple motion with certain frequency can generate enough lift. The unsteady numerical simulations are based on fluid structure interaction (FSI) method and dynamic mesh technology. The flapping motion is in a simple harmonic law of small amplitude with high frequency, which corresponds to the flapping wing driven by a piezoelectric actuator. The inertial and aerodynamic forces of the wing can cause chordwise torsion, thereby improving aerodynamic performance. The concerned flapping frequency refers to the structural modal frequency and FSI modal frequency. The study shows that this flapping motion can satisfy the requirements of lift to sustain the flight on this scale. At a certain frequency, the flapping wing can effectively utilize the strain energy storage and release mechanism of the flexible wing to provide sufficient lift. The modal frequency of the structure can amplify the deformation of the wing, but it cannot improve the aerodynamic performance, however, the aerodynamic efficiency can achieve the highest at the first order FSI modal frequency. There is a flapping frequency smaller than the first order FSI modal frequency maximizes the aerodynamic force in the vertical direction.

Development of an FSI Environment for the Aerodynamic Performance Assessment of Flapping Wings

“…These allow to analyze and optimize different wing shapes, kinematics, and materials with reduced set-up efforts. Recently, [4] studied the influence of the flapping frequency for insect-scale wings while [5] optimized the twist level of rectangular wings and [6] analyzed the influence of wing flexibility on bat wings. These studies couple Computational Structural Mechanics (CSM) and Computational Fluid Mechanics (CFD) solvers through a coupling code.…”