Calculations showing the influence of aerodynamic damping on binary wing flutter

Abstract

The influence of damping is examined by comparing the flutter critical speeds and frequencies obtained using the complete equations of motion and those obtained when all the damping terms are omitted. The calculations are made for binary flexure-torsion flutter of a wing in incompressible flow and the comparisons extend over ranges of values of the principal parameters. When the ratio of air density to wing density is high, the damping terms are found to raise the flutter speed by a large amount. But when the ratio of air density to wing density is low, a condition often occurring in practice, it appears that, over a wide range of parameter variation, the flutter speed obtained in the absence of damping is reasonably close to that obtained from the complete equations. Further experience is obviously needed before any general conclusions can be reached, but the present results offer some hope of reducing either the extent of, or the accuracy needed in, the aerodynamic information used for wing flutter calculations. It is pointed out that with constant aerodynamic coefficients the flutter speed for an undamped system is independent of the wing density.