AIAA学习资料-Aerodynamics.docxVIP

Aerodynamics The aerodynamic analysis should aim at performance optimization and safety, as well as cost minimization. According to RFP requirements, a minimum five-minute aerobatic action and a nine-hour endurance are our primary focuses. Specifically, a five-minute inverted fly and a climb rate of at least 1,500 fpm at sea level are two critical parts in wing design. The section is developed as follows: First wing planform and airfoil are selected; then some determining parameters are settled; finally, performance analysis is discussed and evaluated. 1 Wing Planform Combined with the RFP requirements and research of existing LSA planes, a modified tapered wing is chosen to be the wing shape, which gives significant aerodynamic and structural advantages under low speed. [1] 2 Airfoil Selection Myriads of factors need proper consideration when selecting an airfoil. First of all, regarding to the RFP requirements, we select low-speed airfoils, i.e. NACA series and modern airfoils. Next, other considerations are stated bellow: Consider lift: The airfoil we choose is supposed to satisfy the following restrictions: a) the +6/-5 G loads; b) the wing load of 9.8lb/ft2; c) the 180°/s at maximum level cruise speed, i.e. a high lift airfoil is needed. Additionally, a five-minute inverted fly limits the maximum camber to a relatively low range. Consider drag: The friction contributes mostly to the total drag of a low-speed aircraft. Generally, to satisfy the requirement of drag reduction, an effective way to reduce friction is to decrease the camber. According to the basis above, the GAW (General Aviation Wing) of modern airfoil are considered to best meet these requirements. The relation between lift coefficient of airfoil and angle of attack, the drag coefficient of five GAW airfoil are shown below. As we can see from the figure above, the lift coefficient of the five airfoils are not significantly different. However, under large angle of attack, the drag coefficient of LAN