Optimization of unstalled pitching and plunging motion of an airfoil

Abstract

The motion parameters of a sinusoidally pitching and plunging NACA 0012 airfoil in a uniform stream of low speeds are optimized for high propulsive efficiency and/or high time-averaged thrust coefficient by the inviscid version of a three-dimensional unsteady compressible Euler/Navier-Stokes flow solver. A limited maximum effective angle of attack is applied on the optimization to ensure fully attached flow. Preliminary optimization is obtained by means of the classical linear theory, and then refined optimization is performed by the Euler computation. The highest inviscid propulsive efficiency of 90% with a time-averaged inviscid thrust coefficient of 0.24, and the highest inviscid thrust coefficient of 0.86 with a propulsive efficiency of 65% are obtained at the freestream Mach number of 0.1 and zero mean angle of attack. The mean angle of attack has little effect on the time-averaged thrust coefficient and the propulsive efficiency and can be ignored in the optimization.