A Design Method of High Lift Airfoil

• Main Authors: Hao-Kun Chu, 朱浩坤
• Other Authors: Sheng-Jii Hsieh
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/62520957668948480130

碩士 === 國立成功大學 === 航空太空工程學系 === 87 === ABSTRACT Subject : A Design Method of High Lift Airfoil Student : Hao-Kun Chu Advisor : Sheng-Jii Hsieh A method of inverse airfoil design for incompressible potential flow presented by Selig and Maughmer is used in this study. The problem, from a given surface velocity distribution determine the corresponding airfoil shape, is solved by conformal mapping method. After determining the relation of mapping, one may compute the airfoil shape from the unit circle. The prescription of upper surface velocity distribution obeys the Liebeck''s high lift laws, including constant-velocity region, followed by a Stratford-type zero-skin-friction portion to ensure the flow unseparate when decelerates, and ensure the average velocity of upper surface as large as possible. By assuming an initial input of lower surface velocity distribution, and then modifying a portion of the lower surface by the use of least squares and Lagrangian multipliers, one can ensure the velocity distribution satisfies the constraints of inverse method, and minimizes the profile of closure condition. Two high lift airfoils are designed respectively for airfoil trailing-edge angle 0°and 16°, with angle of attack α= 8°. In corporated with the vortex panel method, one may obtain the relation of lift coefficient and angle of attack, and get the maximum lift coefficient and maximum lift-to-drag ratio , for each designed high lift airfoil. For the first high lift airfoil (zero trailing-edge angle case), the stall angle of attack is α=20°, and the maximum lift coefficient is 2.05, but the lift-to-drag ratio is only 24.37. However, when α=8°, the lift coefficient is 1.57, but there has maximum lift-to-drag ratio 73.52. For the second high lift airfoil (trailing-edge angle 16°case), the stall angle of attack is α=15°, and the maximum lift coefficient is 1.735, but the lift-to-drag ratio is only 10.73. However, whenα= 10°, the lift coefficient is 1.55, but there has lift-to drag ratio 82.03,. This study provides a practical computer program for high lift airfoil design, but for the calculation of lower surface velocity distribution, one should search better method to deal with the singularity around leading edge, so as to obtain the problem resulting of high lift but low lift-to-drag ratio.