Flutter: history, theory and simulations

Abstract

The nature of wing and bridge flutter is investigated in this study. Through comparisons, it isnintended to gain an understanding of the cross disciplined nature of flutter. In order for this tonbe achieved the historical development and pertinent theories are initially analysed. From here,nnumerical modelling and computational fluid dynamics simulations are engaged to provide anquantitative aspect to the investigation.nFrom the historical review, it was revealed that flutter has primarily manifested itself in variousnaircraft lifting structures. Subsequently, much of the early flutter theory was centred around developing analytical solutions for an oscillation aerofoil. However, the collapse of the TacomanNarrows Bridge in 1940 cast a new light on flutter and rendered it as an integral designnconsideration for that of long span suspension bridges. This also led to a surge in the worknconcerned with the development of theory for the prediction of the bridge critical flutter speed.nAn exploration of the theory first involved comparing the mechanism of instability for fourntypes of flutter. These included classical wing flutter, torsional bridge flutter, classical bridge flutter and wing stall flutter. The two classical forms involve modal coupling whereby the motion of the structure contribute to the self-excited forces causing flutter. Conversely,ntorsional bridge flutter and stall flutter are a consequence of flow separation and vortexnshedding that is influenced by the oscillatory motion of the respective structures.nThe unsteady aerodynamic models are then presented for the wing and bridge flutter cases. Duento the premise of potential flow theory upon which the wing model is based, it is deduced thatnits application to the bridge flutter problem is inappropriate. Rather, the complex nature of thenfluid-structure interaction that is facilitated by both forms of bridge flutter necessitates a modelnthat is semi-empirical.nRespective aerofoil and bridge flutter models are developed through the consolidation of thenstructural and aforementioned aerodynamic sub-models. This allowed for a numerical ninvestigation to proceed where the critical speed for the different types of flutter is ascertained. nFollowing this, a parametric study was completed in which the influence of various parametersnon the flutter boundaries was ascertained. Finally, computational fluid dynamics simulationsnwere generated to illustrate the nature of the fluid-structure interaction that is necessary for thendifferent types of flutter.n