Development and Applications of a Virtual Hybrid Platform for Multiscale Analysis of Advanced Structures of Aircraft (DEVISU)

This paper outlines the main findings of the project “DEvelopment and applications of a VIrtual hybrid platform for multiscale analysis of advanced StructUres of aircraft” (DEVISU), which deals with failure of composite structures and noise/vibration reduction, along with investigation of new materials for aerospace applications

Example of a non-smooth Hopf bifurcation in an aero-elastic system

We investigate a typical aerofoil section under dynamic stall conditions, the structural model is linear and the aerodynamic loading is represented by the Leishman-Beddoes semi-empirical dynamic stall model. The loads given by this model are non-linear and non-smooth, therefore we have integrated the equation of motion using a Runge-Kutta-Fehlberg algorithm equipped with event detection. The main focus of the paper is on the interaction between the Hopf bifurcation typical of aero-elastic systems, which causes flutter oscillations, and the discontinuous definition of the stall model. The paper shows how the non-smooth definition of the dynamic stall model can generate a non-smooth Hopf bifurcation. The mechanisms for the appearance of limit cycle attractors are described by using standard tools of the theory of dynamical systems such as phase plots and bifurcation diagrams. © 2012 Elsevier Ltd © 2012 Elsevier Ltd. All rights reserved

On the use of the theory of dynamical systems for transient problems: A preliminary work on a simple model

This paper is a preliminary work to address the problem of dynamical systems with parameters varying in time. An idea to predict their behavior is proposed. These systems are called transient systems, and are distinguished from steady systems in which parameters are constant. In particular, in steady systems the excitation is either constant (e.g.; nought) or periodic with amplitude, frequency, and phase angle which do not vary in time. We apply our method to systems, which are subjected to a transient excitation that is neither constant nor periodic. The effect of switching-off and full-transient forces is investigated. The former can be representative of switching-off procedures in machines; the latter can represent earthquake vibrations, wind gusts, etc.; acting on a mechanical system. This class of transient systems can be seen as the evolution of an ordinary steady system into another ordinary steady system, for both of which the classical theory of dynamical systems holds. The evolution from a steady system to the other is driven by a transient force, which is regarded as a map between the two steady systems. © 2013 Springer Science+Business Media Dordrecht