טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAriel Drachinsky
SubjectLimit-Cycle Oscillation of a Pretensed
Membrane Strip
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Raveh Daniella


Abstract

A computational and experimental study of the nonlinear aeroelastic response of a pre-tensed, high aspect-ratio, thin membrane strip is presented. The goal of the study is to derive and validate a computational model that can be used for analysis and design of membrane strips, for the purpose of energy harvesting from flutter at low airspeeds.

The mathematical model is based on a beam model, accounting for stiffening effects due to pretension and large deformations. The aerodynamic model is a potential flow model. The equations of motion are written as a set of nonlinear ordinary differential equations, using Galerkin’s method, and are simulated numerically. The equations are rewritten in non-dimensional form and the numerical analysis is followed by an asymptotic analysis using the Multiple Scales method. The nonlinear aeroelastic model is used to study the oscillation characteristics of the membrane strip in the various stability regions.

The effects of the initial pretension and non-linear stiffening on the energy-harvesting potential of the system are studied. The combined effect of the preload on the flutter onset speed, on the flutter frequency and amplitude, and on the loss of orbital stability, indicate that an optimal preload can be determined based on the intended airspeed range for energy harvesting.

A series of wind tunnel tests is conducted, in which the flutter onset velocity, and the post-flutter frequencies and amplitudes are measured. Flutter modes are observed using a stroboscope. Good agreement between the experimental data and computational results validate the computational model.