An Experimental Study of Wing Flutter

Abstract

While many experimental studies use springs to model the bending and torsional motions of a fluttered wing in wind tunnel experiments, the mass of the spring is often neglected in flutter calculation. In large test facilities, the spring mass is usually small compared to the mass of the wing. For smaller wind tunnels, however, the mass of the springs is larger relative to the mass of the test wing, and so perhaps should not be neglected. The purpose of this dissertation is to determine the sensitivity of flutter measurements to non-negligible spring mass effects, and thereby qualify a source of uncertainty present in a wide range of flutter experiments reported in the literature. For this purpose of research, two sets of experimental apparatus were designed and built to demonstrate classical two-degree of freedom flutter in open-return, low-speed wind tunnel in the Aerospace and Engineering Mechanics Department at university of Minnesota. In the first set-up, torsion and tension springs were used to provide the pitch and plunge motions, while in the second set-up, tension springs only were used. This apparatus was used to experimentally determine flutter speed for a range of supporting springs. Classical aerodynamic theory was used to calculate flutter speeds to determine how to model added mass due to supporting springs so as to make theory and experiment agree.