The thickness effects on symmetrical airfoil flow characteristics at low Reynolds number

Abstract

© 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The interest in studying the aerodynamic performance of airfoils at low Reynolds number has been increasing recently. There are many applications for airfoil design at low Reynolds number as design point. These applications include sailplanes, propellers, unmanned aerial vehicles (UAVs) and micro air vehicles (MAVs). However, there are few works evaluating the thickness effect as a design parameter for airfoil performance at low Reynolds number regime as well as data from flow visualizations in order to clarify the aerodynamic phenomena regarding thickness variation. In this sense, the aim of this work is to investigate the thickness effect on flow characteristics and performance of symmetrical airfoils at low Reynolds number regime by experimental investigation correlating force measurements with mini-tuft and oil flow visualization data. In an overall view, this work intends to contribute for investigations of desirable flow and geometric conditions of airfoils applied in UAV and MAV designs. Experimental tests were carried out at subsonic blower-type wind tunnel of open loop with closed section at ITA (Technological Institute of Aeronautics). A set of three symmetrical airfoils with different thickness (NACA 0012, NACA 0020 and NACA 0030) were tested at Reynolds number regime between 50,000 and 290,000. The results show distinct thickness effect for Reynolds number condition borders where at Re = 50,000 the thickest airfoil causes full flow separation with a great aerodynamic deterioration. In contrast, at Re = 290,000 the thickest airfoil achieves the highest maximum lift value.