Experimental and Numerical Investigations of Mini-Tab Device for Active Flow Control

Abstract

The next generation of aircraft is likely to exhibit a breadth of aeromechanic and aeroelastic behaviors that will be exacerbated by the turbulent flows generated in urban environments. Exploitation of novel flow control technologies will be critical in offering greater control authority to enable this new generation of aerial vehicles for faster, safer, and more efficient flight. This study experimentally investigates the efficacy of a mini-tab active flow control device using a novel dynamic test rig. Under steady conditions, the mini-tab response exhibited nonlinearity with deployment height. Under dynamic conditions, the lift and pitching moments displayed hysteresis around their quasi-steady counterparts at low reduced frequencies (k=0.05) but displayed significant deviations at middle to high reduced frequencies (k=0.15 to 0.31) due to the formation of a tab vortex that propagates downstream. It was demonstrated, for the first time experimentally, that mini-tab dynamic performance is insensitive to unsteady airfoil motions in pitch and plunge—representative of flutter onset. Finally, an existing mini-tab model was extended to capture vortex formation on the upper and lower airfoil surfaces and modified to incorporate mini-tab rate-dependence on vortex initiation. The model showed good agreement with experimental data in both periodic and transient scenarios.