Investigation of control surface buzz in transonic flow

Spoilers are usually used to suppress the control surface buzz, but no research has been done as to why they can suppress the buzz. Taking into consideration the effects of gap and spoiler, we investigated transonic control surface buzz by numerical method. In order to consider the effects of gap and spoiler, the unstructured dynamic mesh technique is introduced to simulate the movement of the control surface. A finite volume algorithm based on center difference is used to solve the Euler equations. The full implicit dual-time scheme is adopted to treat the unsteady aerodynamic problem. The control surface motion equation is solved by Runge-Kutta method in time domain. When Mach number is 0.75, control surface oscillation is convergent, so control surface buzz does not happen. When Mach number reaches 0.875, there is a nonlinear limit cycle oscillation and control surface buzz takes place. The instantaneous pressure contours of control surface oscillation show that control surface buzz is driven by the phase hysteresis of the shock vibration interacting with the motion of the control surface. When Mach number is 0.875, control surface oscillation with the spoiler is convergent, so the spoiler is in a position to suppress control surface buzz. The spoiler restrains the shock vibration, so the spoiler suppresses control surface buzz.