The effect of leading-edge tubercle on a tapered swept-back SD7032 airfoil at a low Reynolds number

Abstract

An experimental study is performed to research the effect of the implemented leading-edge tubercles on the tapered swept-back SD7032 airfoil at Re of 5.5 × 104 and 1.1 × 105. In this study, along with a baseline model with no tubercles (T0), in total four different configurations are used for analysis of the aerodynamic characteristics. In the other three models (T1, T2, T3) mainly different amplitude and wavelength modulations are studied. In all experimental studies, force measurements are performed by using a six-axis load cell force measurement device. To achieve detailed information on the flow field of all models, surface oil flow visualization technique is used for visualization purposes at Re = 1.1 × 105. The geometric specifications of the model are the sweep angle of 30⁰, the tip chord of 37.5 mm, the root chord of 112.5 mm, and the span of 300 mm. Airfoil models with the LE tubercles significantly improve lift curve at almost all AoAs as compared to the baseline model. The streamwise vortices are positioned together more closely leading to interaction with each other. Consequently, these interactions lead to an increase in turbulence. This increase in turbulence may lead to a better mixing and increase in momentum exchange in the boundary layer. Amongst the models (T1-T3), the best airfoil model is determined as T3, having a1 = 0.06c, λ1 = 0.5c, a2 = 0.015c, and λ2 = 0.125c parameters, in terms of lift, drag and CL/CD ratios.