Control of Aeroelastic Structures via Prescribed Upstream Aerodynamic Disturbances

This grant will advance the national prosperity and security through a scientific understanding of fluid-structure interactions that will advance the fields of aerodynamics, structural dynamics, and vibration control favorable for future high-efficiency aircraft, extended endurance in swarms of swimming or flying robots, enhanced wind and hydrokinetic energy generation, and protection of infrastructure like bridges and pipelines from fatigue damage due to wind and water flows. This award supports fundamental research on modifying and controlling fluid-structure interactions by way of introducing prescribed flow disturbances from an upstream disturbance generator. Depending on the application, it may be desirable to suppress a flutter instability or attenuate oscillations (as in an aircraft wing or turbine blade), increase the amplitude of oscillations (as in an oscillating flow energy harvester), or reshape an oscillation to beneficially affect fluid-structure energy transfer (as in a swarm of swimming or flying robots synchronizing to minimize energy consumption). The approach studied here will enable any of these distinct behaviors to be generated on-demand. The multi-disciplinary approach, and the education activities at the middle school through doctoral levels, will help broaden the participation of underrepresented groups in research and positively impact engineering education.

The objective of this project is to enable distinct aeroelastic system behaviors including equilibrium stabilization / destabilization or limit cycle oscillation amplitude increase / decrease to be created, controlled, and modified on-demand by prescribing aerodynamic disturbances that interact with a target aeroelastic wing. The project aims to understand, model, and formulate control approaches for aeroelastic wings being affected by canonical flow disturbances such as convecting vortices. The first goal is to understand and map the spatiotemporal relationships between incoming flow disturbances and the unsteady aerodynamic forces and moments on a wing using a custom discrete vortex method with a model for external flow disturbances (LDVM-Disturbance) and wind tunnel experiments for validation. A second goal is to establish the effects of incoming flow disturbance topology, strength, frequency content, and phasing on the stability and nonlinear oscillation behavior of an aeroelastic wing. This will be investigated in simulation by coupling the LDVM-Disturbance model with an aeroelastic structural dynamics model, and in validation experiments by measuring the response of an aeroelastic wing section downstream of an actuated disturbance generator. A third goal is to create a sequence of feed-forward system inversions that allows required disturbance generator motions to be determined to produce desired responses in the downstream aeroelastic wing. The results will be used to demonstrate open-loop control of aeroelastic stability and oscillation phenomena in wind tunnel experiments.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.