自然层流机翼气动外形优化研究

摘要

层流技术在飞行器尤其是民用客机减阻方面具有较好的应用潜力。采用全速势方程（TRANAIR）、序列二次规划（Sequential Quadratic Programming，SQP）优化算法及自适应笛卡尔网格技术，用两种不同的参数化建模方法，类函数／型函数变换（Class function／Shape function Transformation，CST）和非均匀有理 B 样条（Non-Uniform Rational B-Spline，NURBS）方法，对某自然层流机翼进行了多点优化设计，设计点为：CL ＝0．45（M：0．735，0．755，0．765，0．775），CL ＝0．50（M：0．755），约束条件为：升力、俯仰力矩和翼型20％、80％及最大厚度不得低于初值。优化结果表明：虽然 CST 方法在翼型描述上具有先天优势，NURBS 方法更多用于三维曲面，而对于文中自然层流机翼算例，NURBS 的优化效果更好；在 CL ＝0．45（M：0．755）状态下，优化后上翼面转捩位置明显后移，层流区域变广，总阻力减小了4．5％；采用的优化方法在进行五点优化时仍然具有较高的计算效率，具有较强的工程实用能力。%Natural laminar wing is a potential technology to minimize the drag coefficient of an aircraft.The code of TRANAIR is used to optimize a natural laminar wing with subject to the constraints on lift coefficient,pitching moment coefficient and geometries height(20%,80% and max height),and the optimization are carried out with multi-points conditions,CL =0.45 (M:0.735,0.755,0.765,0.775)and CL =0.50(M:0.755).The nonlinear full potential equation is used to solve flow field,sequential quadratic programming and adaptive refinement Cartesian grids are applied to optimize the aerodynamic shape.Two parameter methods,non-uniform relational B-spline (NURBS)and class function/shape function transformation (CST),are used to represent wing shape and update the new geometry,although the CST method is usually used to describe aerofoil and the NURBS is more applied on three-dimensional curved surface.The optimization results shown that the NURBS method is better than the CST one,and the transi-tion position of laminar flow to turbulent flow are moved backward obviously,the laminar region are more wide than before,and the CD of the optimized wing decreased 4.5% at CL =0.45(M:0.755).