Multibody analysis of whirl flutter stability on a tiltrotor wind tunnel model

Abstract

Tiltrotor aircraft are equipped with large rotors, usually driven by heavy engines in nacelles located at the tip of the wings. This combination of large rotors and high masses on wings which form a relatively elastic support makes whirl flutter a critical phenomenon for the design of the aircraft and its performance. In this article, a multibody-based simulation model of a tiltrotor wind tunnel model is presented, combining a mixed finite element/multibody representation of the support, a detailed kinematic model of the rotor hub and a strip-wise definition of air loads on the blades. Investigations on the effect of parameter changes and non-linearities on the calculation of the aeroelastic stability boundary are executed. The selected operational points are taken from wind tunnel experiments performed by a consortium of partners in the course of the European ADYN project. The regarded wind tunnel model is a half model of a tiltrotor wing, simplified for the use in whirl flutter investigations. The rotor is four-bladed; the rotor hub is of a gimbal type. Structural dynamics properties of the model are known from detailed experimental investigations. Numerical analyses of the dynamic behaviour of the model are performed in the frequency and in the time domain. Results show considerable differences for linear and non-linear models. This paper describes the simulation approach, the model setup and the comparison of the data with selected experimental results.