Limit-cycle oscillations of a pre-tensed membrane strip

The paper presents a computational and experimental study of the nonlinear aeroelastic response of a pre-tensed, high aspect-ratio, thin membrane strip. 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 pre-tensed-beam model, accounting for bending and torsional 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 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 are conducted, in which the flutter onset velocity, and the post-flutter frequencies and amplitudes are measured. Good agreement between the experimental data and computational results validate the computational model.