Towards Industrialisation of Bifurcation Analysis in Rotorcraft Aeroelastic Problems

Abstract

The dynamics of rotary wing systems is complex and typically features highly nonlinear and often unsteady aerodynamics as well as aeroelastic influences. In the helic opter industry and in ongoing efforts to reduce noise and vibration, the incorporation of active devices such as trailing edge flaps on the rotor blades is being studied. Such devices can introduce further nonlinearities. Therefore, it is important to be able to evaluate the stability of the overall system with sufficient insight into the global nonlinear behaviour. Numerical bifurcation analysis is well suited to this need, and this paper presents examples of the technique being used in efficiently evaluating the stability of helico pter rotor systems. The first example investigates the aeroelastic stability of rotor blades of a medium-sized helicopter in hover and the periodically forced forward flight condition, in both trimmed and untrimmed cases. In the second example, bifurcation analysis is used to predict the nonlinear stability of trailing edge flaps ‐ inco rporated in elastic blades ‐ over a range of design parameters, whereas the last example illustrates a case where bifurcation tools are used to study the nonlinear dynamics of a basic rotor model created in a commercial multi-body software.