Numerical Investigation of Aerodynamic and Stability Behavior of Corrugated Airfoils at Low Reynolds Number

A comprehensive computational study of the aerodynamic performance and stability characteristics of corrugated airfoils has been conducted at the Low-Reynolds number corresponding to the flight regime of micro-aerial vehicles (MAVs). This research aims to explore the applicability of bio-inspired airfoils in the design of MAVs and to study the effect of corrugations, and thus the entrapped vortices on the inherent tendency of airfoils to diminish flight disturbances. Computational fluid dynamics (CFD) analyses have been performed on three dragonfly-based corrugated airfoils, flat plate, and a "smoothened version" of a pleated airfoil; a comparison of their aerodynamic coefficients is discussed. The stability aspect of these airfoils is studied by estimating dynamic longitudinal damping coefficients at different angles of attack. These damping coefficients are calculated by inducing forced sinusoidal oscillations centered at the quarter-chord of each airfoil while maintaining the reduced frequency (k) in a quasi-steady aerodynamic regime. The interlink relation of the time-step size of transient simulations with the angular frequency of oscillations is also discussed concisely. The aerodynamic results show little-to-no difference between the pleated and smoothened version of the airfoil; thus, further strengthening the notion of the existence of a "switch-over" region from pleated airfoil to smoothened airfoil near Reynolds number (Re) of 100,000. Similarly, the perusal of dynamic damping coefficients of airfoils also suggests a negligible effect of corrugations or entrapped vortices on the stability behavior of airfoil.