טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDomany Elad
SubjectTargeted Energy Transfer in Dynamical Systems with self-
Excitation
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Oleg Gendelman
Full Thesis textFull thesis text - English Version


Abstract

Models of self-excited oscillations, which involve autonomous systems with stable limit cycle (or more complicated attractors), arise in various engineering problems. LCOs (Limit Cycle Oscillations) are known to be one of the most dangerous phenomena in mechanical structures in general, and more specifically in fighter aircrafts at high subsonic and transonic speeds. Sustained LCOs in the wing structure due to flutter can cause structural damage, including fatigue, which in turn can cause failure of the wings of the aircraft.

 The purpose of this research project is to develop a design for suppression of these undesired self-excited oscillations, based on the concept of nonlinear energy sink (NES). This idea is based on adding to the primary system a relatively small and spatially localized attachment, which leads to essential changes in the properties of the whole system.

In this work, we consider modeling the primary mass which approximates real fluttering systems. The ultimate goal is to design and optimize passive attachments for suppression of flutter, by analyzing the reliable dynamical model of the system with approximate analytical and numerical methods.

In addition to the flutter problem, we present the preliminary analytical calculations and results of a model of a cylinder atop an elastic foundation in a flow. The suppression of Vortex Induced Vibrations (VIV) in this system is averaged with the same method used for the model problem of flutter suppression, however here we are unable to use asymptotic methods for further simplifications.

The research results consist of a variety of dynamical cases which were found for different sets of parameters, and later verified with the help of numerical simulations for the time response and the instantaneous frequency of the system.