Gust Energy Harvesting of a Free-Flying Aircraft Model by CFD/CSD Simulation and Wind Tunnel Testing

The purpose of this study was to investigate the energy-harvesting performance of a piezoelectric free-flying aircraft model under discrete gust. A fluid-structure-electric coupled simulation framework was established by loose coupling the computational fluid dynamics (CFD) solver and the electromechanical finite-element model. The field velocity method was used to introduce vertical gust velocities to the CFD computation. The pitch and plunge rigid degrees of freedom (DOF) were considered, together with elastic DOF in the electromechanical finite-element model by means of multibody dynamics. The output energy density and mean power were used to evaluate the harvesting performance. The effects of external load resistance, free-flow velocity, and gust frequency, especially the rigid DOFs were studied, respectively. A prototype of the piezoelectric free-flying aircraft model was fabricated. The output voltage was tested at different flow velocities and different sinusoidal gust frequencies with a given external load resistance of 10.3 Mω in the wind tunnel test. The macrofiber composite (MFC) received an optimal voltage of 107 V and an optimal mean power of 0.188 mW at the flow velocity of 22 m/s and a gust frequency of 3.5 Hz, around the first bending mode. Moreover, the electromechanical finite-element model and the coupled simulation framework were verified by the ground vibration test and the wind tunnel test, respectively. Results indicated that the rigid pitch and plunge DOF may decrease the harvested energy to only one-third of the energy of a wall-mounted structure. The present work provides an effective theoretical and experimental basis for further studying the energy harvesting and vibration control of free-flying aircraft.