Parametric Study of the Flutter Stability of a Semi-Rigid 3D Wing-With-Engine Nacelle Model in Subsonic Flow.

Kurzfassung

A parametric investigation is performed of the aeroelastic flutter stability behaviour of a semi-rigid 3D wing-with-engine nacelle model in subsonic flow. The system under investigation is a wind tunnel model that was flutter tested some years ago. It consists of a swept-back half wing with a pylon mounted engine nacelle, representative of modern large transport aircraft, and is elastically restrained at its wing root, so that it may execute decoupled (rigid body) rolling and pitching oscillations about two orthogonal axes. For this binary aeroelastic system, first the equations of motion and then the aeroelastic stability equations are set up in terms of generalized coordinates. In addition to the basic wind tunnel model configuration, two artificial configurations with other positions of the rotation axes and corresponding mode shapes are investigated. For the computation of the motion-induced generalized airloads, a panel technique is used for both the wing and the engine nacelle that is replaced by an annular wing. Numerical results are presented for several systematic parameter variations and Mach numbers, where special emphasis is placed on the effects of the motion-induced unsteady airloads acting on the engine nacelle, the position of the rotation axes, and the frequency ratio of the two modes in roll and pitch. Moreover, a comparison is made with some wind tunnel test results.