Flutter Prediction of Multimode Systems from their Turbulent Responses by Jury’s Criterion

Abstract

This paper presents a further development of the latest simulation analysis, which consists of generating sequential responses of multiple-mode aeroelastic systems excited by flow turbulence, likely observed in a wind-tunnel flutter test, and also applying to them the flutter boundary prediction based on Jury’s stability criterion. Accurate prediction of the flutter speed based on the conventional damping approach is usually very difficult, because the damping coefficient of the critical mode often scatter very much and has tendency to suddenly become negative near the flutter boundary with increasing speed. Since 1980's, the present author and his coworkers have investigated the flutter boundary prediction based on digital data techniques, focusing on the stability of wing systems by using Jury's stability criterion defined in the discrete-time domain. Although all the previous studies showed that this prediction method was more effective than the damping approach, most analyses were limited to binary-mode systems. Hence, in the latest study a new multiple-mode flutter system excited by air turbulence in the flow was formulated. Here the simulation analysis of the boundary prediction using response signals of systems with four modes has further been developed to examine its feasibility. Numerical results show that the digital prediction method is very effective in estimating the flutter boundary of the multimode aeroelastic system from a sufficiently lower dynamic pressure range, too.