Aeroelastic Analysis for Highly Flexible Flapping Wing in Hover

Abstract

Aeromechanics of a flexible flapping wing is a complex nonlinear fluid-structure interaction problem and therefore, cannot be analyzed using conventional linear aeroelasticity methods. This paper presents a stand-alone coupled aeroelastic framework for highly flexible flapping wings in hover for Micro Aerial Vehicle (MAVs) application. A realistic hover-capable flapping-wing MAV utilizes highly flexible wings operating at high frequencies/amplitudes, which causes extreme wing deflections and highly unsteady, vortical flows. The strong fluid-structure coupling and the complicated flow physics make the performance of such a system extremely difficult to predict. The MAV-scale flapping wing is modeled using fully nonlinear beam and shell theories. A potential-flow-based unsteady aerodynamic model is then coupled with the structural model to generate high fidelity coupled aeroelastic framework. Both the structural and aerodynamic models are validated independently before coupling. Direct numerical transient analysis is performed using the Newmark-b method. The instantaneous lift force and wing deflection predictions from the coupled aeroelastic model correlated well with the force and deflection measurements (using Digital Image Correlation, DIC) obtained from in-house flapping wing experiments at both moderate (13 Hz) and high (20 Hz) flapping frequencies.