New Concept for Flutter Suppression Based on Nonlinear Energy Pumping

摘要

The principal goal of this project was the attenuation and elimination, through the use of nonlinear energy sinks (NESs), of limit cycle oscillations (LCOs) that occur in aeroelastic systems. The NES is a fully passive device that is able to drastically modify the global dynamics of a system, despite being a local modification. It was demonstrated, through analysis and simulation, that the implementation of the NES on a Van der Pol oscillator, which is well known to exhibit limit cycle behavior, leads to suppression of the LCO over a wide range of the NES parameter space. Examination of the well-known aeroelastic scenario of a cubically nonlinear rigid wing in a quasi-steady flow field showed, for the first time, that LCO formation is a consequence of a series of resonance captures and escapes, and that the heave mode response is the unique trigger for the pitch mode LCO. Implementation of the NES on an aeroelastic system revealed that suppression occurs over a broad range of NES parameters in one of three distinct flavors: complete elimination; burst and elimination; and attenuation. All predictions for this configuration were confirmed in a series of wind tunnel tests in the nonlinear aeroelastic test apparatus (NATA) at Texas A&M University. Analysis and simulation indicate an NES with the same total mass distributed among multiple degrees of freedom can be even more effective.