Measurements of the direct oscillatory derivatives for a linear bending mode on four rigid half-span models at subsonic and transonic speeds, in closed and slotted tunnels

Abstract

Measurements have been made of the direct damping and stiffness derivatives for four rigid half-span models oscillating in a linear bending mode about an axis near the root in high-speed wind tunnels. A Mach number range of 0.6 to 1.1 was covered and the frequency parameter varied between 0.12 to 0.04. The effect of converting the slotted tunnel to a closed tunnel gave large changes in the stiffness derivatives, whilst the damping derivatives showed only small to moderate changes. Comparison with theory for the damping derivatives showed reasonable agreement, especially under closed-tunnel conditions.