GVT-based ground flutter test without wind tunnel

A new experimental technique is conceived and validated for the determination of the flutter speed and frequency of vehicles or wings without the need for a wind tunnel. The testing is carried out on the full scale structure subjected to forces, equivalent to the aerodynamic loads, exerted by shakers. The close coupling between the structural response and the aerodynamics is simulated in real time by measuring the response, computing the corresponding aerodynamic forces from a linear state space model, and applying these forces to the structure through the shakers. Besides a significant reduction in cost as compared to wind tunnel testing, the proposed testing strategy also allows for the consideration of structural nonlinearity and the inclusion of flight control system while using the same hardware as would be used in a classic ground vibration test (GVT). The key challenges, successfully resolved here, were the reduction of the distributed aerodynamic loaded to a few concentrated forces and the control of the shakers to provide the necessary force. The technique is demonstrated on a rectangular plate with three different mass distributions and a very good agreement of the observed flutter speeds and frequencies with their counterparts computed from an updated finite element model is obtained.