Flexible wings and fluid-structure interactions for micro-air vehicles

Aerodynamics, structural dynamics, and flight dynamics of natural flyers intersect with some of the richest problems in micro-air vehicles (MAVs), including massively unsteady three-dimensional separation, transition in boundary and shear layers, vortical flows, unsteady flight environment, aeroelasticity, and adaptive control being just a few examples. A challenge is that the scaling of both fluid dynamics and structural dynamics between smaller natural flyer and practical flying hardware/lab experiment (larger dimension) is fundamentally difficult. The interplay between flexible structures and aerodynamics motivated by the MAV development is discussed in this chapter. For fixed wings, membrane materials exhibit self-initiated vibration even in a steady free stream which lowers the effective angle of attack of the membrane structure compared to that of the rigid wing. For flapping wings, structural flexibility can enhance leading-edge suction via increasing the effective angle of attack, resulting in higher thrust generation.