Theoretical determination of subsonic oscillatory airforce coefficients

Abstract

Methods for calculating generalised airforce coefficients on a harmonically oscillating flat plate wing in subsonic flow based on linearised theory, have been in the course of development for many years. The linearised theory is used to set up an integral equation relating the unknown loading distribution to the known upwash distribution on the wing. Basically two methods have been in the course of development for solving the integral equation numerically. In the one the loading distribution is replaced by a distribution of concentrated loads on certain lines and is known as the doublet lattice method, whereas in the other the loading distribution is replaced by an approximation which is continuous over the wing except in the neighbourhood of its leading edge and is known as the lifting surface method. There are also methods which are not based on the above-mentioned integral equation, for example the vortex lattice method. In this paper we concern ourselves exclusively with the lifting surface method.