Thrust Generation Caused by Flapping Airfoils in a Biplane Configuration

Unsteady, viscous ows over apping airfoils in a biplane conguration are computed on moving overset grids.The overset grid solutions are obtained in parallel in a distributed memory environment. Unsteady owelds are described by particle traces. Time-averaged thrust values are obtained from the integration of the unsteady drag coefcient. It is shownthat airfoils in a biplane conguration and oscillating in acombined pitchand plunge motion with a proper phase shift between them produce 20 – 40 % more thrust than a single apping airfoil. Turbulence in the ow further augments the thrust generation. For a maximum thrust at a given a pping frequency, an optimiza tion of the apping motion para meters is needed.