Tip Vortex Control via a Tab Deflecting at Higher Harmonic Frequencies

Abstract

The impact of a trailing-edge tab, actuated at different start times and higher harmonic frequencies, on the size and strength and the position of a tip vortex generated by an oscillating NACA 0015 wing was investigated. The results show that for all the tab control cases tested, the peak tangential velocity of the tip vortex was found to be a weak function of the tab motion, whereas the core radius and circulation were strongly dependent upon the tab deflection. The 2/revolutions higher harmonic tab control actuated during pitch up produced the largest reduction in the peak tangential velocity and the greatest increase in the core radius and also provided the most promising blade-vortex-interaction suppression. Similar control effectiveness was also observed for 3/revolutions higher harmonic tab control motion but to a lesser extent. The 4/revolutions higher harmonic tab control was, however, most effective during the pitch-down flow-reattachment process.