Performance of leading edge tubercles for a thin airfoil
Adson Agrico de Paula1; Julio Romano Meneghini2; Bruno Ricardo Massucatto Padilha1; Bento Silva de Mattos1; Roberto Gil Annes da Silva1
1 Technological Institute of Aeronautics; 2 Polytechnic School of the University of São Paulo
doi:10.20906/CPS/COB-2015-1699
Resumo
In the 1990's decade, a biomechanical study justified the morphology of the humpack whale as an adaptive form to survive in the nature. It was supposed that tubercules on the leading edge of humpack whale flippers enhance maneuverability during prey attack and capture. This study motivates the outbreak of many researches, in the 2000's decade, investigating the phenomenon of the sinusoidal leading edge on airfoils. The geometry of the airfoil, wing planform and tubercles, and also Reynolds number regime are variables considered for understanding of the complex phenomenon regards tubercles performance. This work carried out wind tunnel tests for full-span model comparing a baseline thin airfoil (NACA0012) to a modified with sinusoidal leading edge in order to investigate aerodynamic performance changes caused by tubercles. The dependence of the sinusoidal leading edge geometry (amplitude and wavelength) as well as Reynolds number effect (Re= 50.000 to 250.000) on tubercles efficiency were evaluated. The results show different performance for tubercles at post- and pre-stall regime. At pre-stall condition, the presence of tubercles deteriorates aerodynamic characteristics decreasing lift and increasing drag. In the other hand, at post-stall condition, the modified profile has a smooth stall whereas the baseline airfoil has an abrupt stall. The decrease in amplitude and increase in wavelength improve tubercles performance. In terms of Reynolds number effect, an increase in Reynolds number improves tubercle efficiency. In order to understand better the tubercle phenomenon, flow visualization using mini-tufts was also performed to evaluate the flow characteristics at post- and pre-stall conditions.
Palavras-chave: Aerodynamics; Thin airfoil; Tubercles performance; Low Reynolds number; Flow control