Abstract:
Wing rock is a highly nonlinear complex phenomenon in which an aircraft undergoes self excited roll oscillations about its longitudinal axis, also known as Limit Cycle Oscillations (LCO).
This phenomenon usually occurs at low flight speeds when an aircraft flies at higher angles of
attack. Wing rock poses some serious challenges to stability, maneuverability and safety aspects
of an aircraft.
This study aims to investigate wing rock phenomenon on a rectangular wing of aspect ratio
two and Reynolds number of 100,000. These conditions are typical of fixed-wing Micro Air
Vehicle (MAV). The numerical study is conducted to find the static and dynamic stability
derivatives in roll from 0˚ to 30˚ angle of attack, and a reduced frequency of 0.0346 through forced
roll oscillations of 40˚ amplitude. The forced roll oscillations on the rectangular wing were
implemented through the sliding mesh technique in a CFD solver.
The loss in roll moment damping, a necessary condition of wing rock, was observed in the
vicinity of the stall. The flow physics of the vortex dynamics revealed that the wing rock
phenomenon starts to occur due to bursting of side tip vortex and its interaction with the leading
edge separated vortex at an angle of attack near stall. The damping derivative in roll is
approximated through cubic polynomial. This research work can be extended to locate the onset
of wing rock phenomenon for a range of aspect ratios. Moreover, one can also dive into the other
relating vortex induced vibrations phenomena.
