2014 年 62 巻 1 号 p. 24-30
Aerodynamic performances of four kinds of airfoils are examined in flows with low-Reynolds number. The aim of the present study is to find the airfoil shape, which provides a large value of a maximum lift-drag ratio in order to develop a high efficiency propeller for the Mars exploration airplane. A triangle airfoil is a base contour of the test airfoils and effects of blunt trailing edges on airfoil characteristics are examined using numerical simulations. Furthermore, a variation of aerodynamic characteristics of one airfoil with a blunt trailing edge due to decreased thickness and increased camber is also examined. The numerical results are verified by experiments. As the trailing edge thickness is increased, the lift-drag ratio becomes larger and values of the lift and the drag forces become smaller at the angle of attack where the lift-drag ratio becomes maximum. By increasing the trailing edge thickness, the boundary layer separation is suppressed and the aerodynamic forces are reduced. The increased camber and decreased thickness yield a significant lift increase of the airfoil with the blunt trailing edge and a small amount of drag increase. As a result, the airfoil with the blunt trailing edge yields large value of the lift-drag ratio in the flows with low-Reynolds numbers.