Surface Pressure Distributions on 4% Circular Arc Airfoil at Low Reynolds Number

Abstract

V ERY small aircraft, called micro air vehicles (MAVs), are of high interest because electronic equipment can be miniaturized to allow for the easy manufacture of a vehicle whose entire mass is only a few dozen grams. Small-sized MAVs operate at chord Reynolds numbers below 1:0 10. Because of the influence of viscosity, thin and sharp leading edge airfoils with thickness ratios less than about 5%offer better aerodynamic characteristics than thick and blunt edge airfoils with Reynolds numbers lower than 1:0 10 [1]. Mueller has measured the aerodynamic forces acting on a circular arc airfoil for MAVs; however, compared with thick and blunt edge airfoils, very little literature is available for thin and sharp leading-edge airfoils [1,2], which indicates that more research needs to be done for the low Reynolds number region. Cosyn and Vierendeels [3] numerically studied the low Reynolds number aerodynamics of a flat plate and an S5010 airfoil, which is an airfoil with a 10% thickness ratio. They have also pointed out that low Reynolds number flows exhibit complex flow phenomena, such as laminar separation, which was described by Mueller and DeLurier [4]. For the design and manufacture of MAVs, it is important to know the details of their aerodynamic characteristics, such as surface pressure distribution. However, there is no space inside of the circular arc airfoil for plumbing the pipes from the static pressure port to the pressure transducer. Thus, as far as the authors know, there are no experimental data measuring surface pressure distributions over a circular arc airfoil except for [2], which used luminescent, pressuresensitive paint. In this study, to measure the surface static pressure of the circular arc airfoil, wemade a 4% cambered-airfoil sectionmodel with a 1% thickness ratio by soldering copper pipes. We also conducted surface flow visualizations using the oil flow technique. The present experimental results at a chord Reynolds number of Re 62; 000 are expected to provide useful information for understanding the flowfield of the circular arc airfoil at a low Reynolds number aswell as for confirming the accuracy of numerical estimations concerning a circular arc airfoil.