Flutter and limit cycle oscillations of two-dimensional panels in three-dimensional axial flow

Abstract

Experimental flutter and limit cycle oscillations (LCO) of two-dimensional elastic plates in three-dimensional axial flow were observed. The plate is clamped at its leading edge and free at its trailing edge, i.e., it is a “flag” albeit one dominated by its bending stiffness. In the companion theoretical model the structural nonlinearity arises in both the bending stiffness and the mass inertia. Aerodynamic nonlinearities are neglected, however, and linear three-dimensional incompressible vortex lattice aerodynamic theory and a corresponding reduced order aerodynamic model were used to calculate the linear flutter boundary and also the LCO (that occur beyond the linear flutter boundary). The results from the theory and experiment are in good agreement for the onset of flutter, including the critical flow velocity at which the aeroelastic system becomes unstable, as well as the aeroelastic mode of oscillation and frequency. However, there are significant differences between the present theory and experiment for large-amplitude LCO. It is hypothesized that aerodynamic nonlinearities (not modelled in the present theory) are the primary cause of these differences.