S. Orlando, M. Brughmans, T. Karaağaçlı, Ü. Ceyhan, Ö. Sümer, M.E. Cerit, B. Durak
DOI Number: N/A
Conference number: IFASD-2015-175
Modal dampings and frequencies obtained from flight tests of F-16 aircraft with external stores are compared to damping and frequency estimates of computational aeroelastic analyses based on Euler flow. Experimental modal parameters have been determined by performing operational modal analysis (OMA) to wing tip acceleration data with flutter module of LMS Test Lab© [1]. In order to adequately excite the wing and store modes of interest, two annular wing exciters (rotating vanes) located at the wing tips have been used. Aeroelastic analyses have been performed by using MLOADS module of ZEUS© [2]. In this module, a static aeroelastic analysis is carried out first to obtain mean flow solution from which the transient response analysis starts, using the time domain unsteady Euler computation. Given the time history of the control surface deflections as input, MLOADS computes the transient acceleration response of the structural grid points located at the wing tips. Damping and frequency estimates of the aeroelastic simulations have been obtained by the post-processing of the numerical results with OMA as in the case of flight test. The comparison of modal frequencies of the most dominant mode between numerical predictions and flutter tests has shown a good agreement. On the other hand, modal dampings estimated from test have shown some underestimation and discrepancy compared to simulation results. Although modal dampings obtained from test and analysis do not agree in a quantitative sense, the evolution of the damping curves of the most dominant mode with respect to the speed of the aircraft exhibits a very similar trend. This proves that damping estimates of both test and simulation for the most dominant mode are added values to the safety of the flutter testing.