Identification of Unsteady Aerodynamic Forces from Forced Motion Wind Tunnel Experiments

Abstract

The Active Aeroelastic Test Bench is used for the study of low subsonic unsteady aerodynamics through forced motion experiments of rigid wings in pitch and plunge. The use of highly dynamic electric linear actuators allows for arbitrary motion in both the pitch and plunge degrees of freedom. In this paper, we discuss the forces measured on a constant section NACA 0018 wing subjected to isolated single and multisine motion in pitch or plunge. A data-driven approach is used, in which the importance of filtering and averaging of the noisy wind tunnel data is discussed. It is concluded from the forced motion experiments that a good agreement between the single and multisine experiments exists. However, only the pitch experiments agree with predictions from Theodorsen’s unsteady aerodynamics theory. The plunge experiments show the presence of major nonlinear contributions in the measured force response. Because of friction in the linear bearings of the setup, it cannot be excluded that these are generated by the plunging mechanism or the setup itself. Additionally, it is illustrated how the use of multisine signals for the identification of unsteady aerodynamic transfer function models allows for a reduction of wind tunnel test time by a factor of 10.