Sound Generation Mechanisms in the Flapping Flight of Insects

Aero-acoustics of insect flight has received less attention than aerodynamics whch is typically modeled with an incompressible assumption. The fundamental harmonic of the generated sound corresponds to the flapping wing frequency, but the sound generation mechanisms for the higher order harmonics are not understood. The flapping wings induce complicated vortex structures which related to the sound production. The leading edge, wing tip and trailing vortices associated with the wing dynamics in both hovering and forward flight relate to fluid structure interactions from the wing deformation. Better understanding of the the fluid structure interactions in terms of the sound production as well as lift and drag is needed. The flight sound generation of adult Coconut Rhinoceros Beetle (Oryctes rhinoceros) and the Oriental Flower Beetle (Protaetia orientalis) was studied at an invasive species center at the University of Hawaii Manoa.The individual beetles were measured in terms of size, wing span and weight. A four element microphone array with a synchronized high speed camera (X-Stream, Inc.) at 1000-5000 fps measured the tethered flight sounds. The wing motion was digitized from high speed video for computation with the unsteady, compressible flow solver (CAESIM, Adaptive Research, Inc.). The models of the wing motion were obtained using mesh deformation methods for a moving body. The flapping was modeled with a prescribed bending along with a coupled rotation and translation from a hinge position..