Computational and Experimental Study of a Transonic All-Movable Fin With Freeplay

This study presents an aeroelastic wind tunnel model of a transonic all-movable fin with freeplay. To investigate the aeroelastic behavior under combined nonlinearities, both numerical simulation and wind tunnel testing were conducted. The numerical simulation employed a coupled computational fluid dynamics/computational structural dynamics approach to analyze the time-domain response of the fin under different dynamic pressures at Mach 0.9, accounting for both linear and nonlinear structural behaviors. The results revealed that both the linear fin (without freeplay) and the nonlinear fin (with freeplay) exhibit limit cycle oscillations at Mach 0.9. However, the nonlinear fin shows a significantly lower onset dynamic pressure for limit cycle oscillations and higher oscillation amplitudes under the same dynamic pressure compared with the linear fin. Wind tunnel tests further demonstrated that the transonic all-movable fin with freeplay experiences significant limit cycle oscillations between dynamic pressures of 66.7–69.7 kPa, with flutter occurring near 71.3 kPa. These experimental findings align well with the numerical results.