Experimental and Computational Investigation of the Aero-Acoustics of Flying Beetles

The sounds of flapping wing insects are typically dominated by a fundamental with higher harmonics, but the underlying structure and aero-acoustics beyond the frequency and amplitude are not well understood especially for beetles. However, the aerodynamics and acoustics of invasive species of beetles are of interest in terms of fundamentals of flight and passive detection methods.  The Coconut Rhinoceros Beetle (Oryctes rhinoceros) and the Oriental Flower Beetle (Protaetia orientalis) have been studied during tethered flight with synchronized microphone array measurements and high speed videos (1000-10,000 fps).  The larger Coconut Rhinoceros Beetles have fundamental ~ 50 Hz with a distinctive torsional wing rotation compared that of the Oriental Flower Beetle (~100 Hz).  Computational fluid dynamics simulations were performed using an unsteady compressible flow solver (CAESIM, from Adaptive Research) using a high resolution (TVD) methodology.  Models of the wing flapping motion were accomplished using mesh deformation techniques with the flapping following from rotation with a prescribed bending, coupled rotation and an originating  translation from the wing’s hinge position.  Fluid structure interaction simulations, with respect to the wing’s flexibility, are planned for an extended experimental comparison.