Aerodynamic Load Alleviation Using Minitabs

Abstract

Increased aerodynamic loads during gusts, turbulence, and maneuvers define the outer envelope of aircraft structural design. Minitabs, which are small spanwise strips that protrude normal to the airfoil’s upper surface, have been studied to alleviate this requirement. To investigate the minitab’s steady-state effects, force and particle image velocimetry measurements were conducted at on a NACA0012 airfoil. Minitabs with heights of and 0.04 were placed at a wide range of chordwise locations. In general, the optimum location for peak lift reduction moved toward the leading edge as the angle of attack increased, with significant effect on the lift curve gradient. Trailing-edge placement was effective at small angles. Placement close to the midchord provided a constant effect across the range of . For both locations, the baseline flow separation progressed ahead of the minitab with increasing , which reduced effectiveness at stall. In comparison, placement close to the leading edge was ineffective for small . At high , a large flow separation reduced lift by up to but increased the unsteady forces.