Real-time assessment of flutter stability based on automated output-only modal analysis

Abstract

During the development of new aircraft wind tunnel testing of 2D and 3D airfoils or even complete aircraft is essential. The structural integrity of the wind tunnel model needs to be assured for the test campaign because a failure can cause severe damage on the wind tunnel facility and means the loss of the costly model itself. To enhance the level of safety, a detection of the flutter stability while testing is necessary. This paper addresses a method for fast and reliable identification of eigenfrequencies and damping ratios using operational modal analysis methods. The developed procedure has been applied in a wind tunnel test campaign by the Institute of Aeroelasticity of the German Aerospace Center (DLR) in the Transonic Wind Tunnel in Göttingen, Germany. A 2D airfoil was tested in a so-called flutter test rig with two degrees of freedom for pitch and heave motion. The main focus of the presented method is the time efficiency of the algorithm which enables the user for quasi “real time assessment” of the flutter stability.