Nonlinear oscillations of aerodynamically coupled oscillators

An array of airfoils is considered as an energy harvesting system. Each airfoil is attached to an elastic cantilever instrumented with piezoceramic patches, and this combination represents a piezoelastic airfoil oscillator. The airfoils are arranged in a parallel configuration and allowed to have unequal chord lengths. Aerodynamic interactions amongst the piezoelastic airfoil oscillators are computationally studied by using a co-simulation scheme. In this scheme, an unsteady vortex lattice method scheme is used to obtain aerodynamic loads, and a reduced-order model is employed for each piezoelastic oscillator. Two and three airfoil oscillator systems are considered, and in the computational investigations, the airfoil chord length is varied across a selected range. Nonlinear oscillations of these systems are examined with respect to parameter variations in the freestream speed, streamwise inter-airfoil spacing, and cross-stream inter-airfoil spacing. Particular attention is paid to flutter instabilities and post-flutter dynamics and the observed qualitative changes in the system response are discussed in terms of pitch responses, pitch phase ratios, and plunge amplitudes. The findings of the work suggest that certain parallel configurations of airfoil arrays with cross-stream stagger and streamwise stagger may be desirable for energy harvesting.