03.1 - Aerodynamics – CFD Methods and Validation
NUMERICAL INVESTIGATION OF WING ROCK PHENOMENON ON LOW ASPECT RATIO RECTANGULAR WINGS AT LOW REYNOLDS NUMBER
A. Sultan¹, A. Maqsood¹, T.H. Go, Raytheon Missile Systems, United States; R. Riaz¹; ¹National University of Sciences & Technology, Pakistan
The wing rock phenomena involves complex multiple degree of freedom non-linear dynamics, which results in the aircraft undergoing self-excited Limit Cycle Oscillations (LCO) primarily in the roll axis. It usually occurs at relatively low flight speeds when the aircraft is flying at high angle of attack. The wing rock phenomenon has been most intensively studied on delta wings, however, very little work has been done to decipher the wing rock on rectangular wings planform. Study of wing rock on rectangular wing planform is important because these planforms are quite commonly used in Micro Air Vehicles (MAVs). Low aspect ratio rectangular wings haves additional two side-tip vortices, the interaction of these vortices with leading edge vortex can give rise to instabilities at such higher angle of attacks. rnLow aspect ratio rectangular wings possess some unique and peculiar aerodynamic characteristics. In addition to linear lift which is generated due to the circulation of flow around wing they also generate nonlinear lift which is mainly due to the presence of additional wingtip vortices. Separation bubbles and laminar to turbulent transition make this flow regime even more complex to study. rnIn this research a small low aspect ratio rectangular wing at low reynolds number is used to relate the vortical structures and flow physics with the dynamic stability derivatives i.e. the loss of roll damping in the vicinity of the stall. rn This numerical study was performed to locate the wing rock phenomenon on a two-aspect ratio rectangular wing at a low Reynolds number of 100,000 by finding the static and dynamic stability derivatives in roll, at 5?-20? angle of attack with an increment of 5°, and a reduced frequency of 0.0346 by the application of forced roll oscillations of magnitude 40? using Computational Fluid Dynamics. At all angle of attacks the numerical results showed a negative value of static stability derivat