【作者】 潘秀东；

【导师】 薛雷平； 宋文滨；

【作者基本信息】 上海交通大学 ， 流体力学， 2011， 硕士

【摘要】 翼梢小翼具有减少诱导阻力的作用,对于运输机而言,安装小翼可以提高其气动性能。但是,翼梢小翼又会导致翼根弯矩增加,影响机翼结构强度。多参数控制的NURBS曲线具有很强的成形能力,适合于构建新型翼梢小翼参数模型。小翼翼型对小翼气动性能影响较大,设计中需要选择合适的翼型。此外,气动计算方法和优化策略的选择直接影响优化结果的好坏。本文以小翼减阻最大化为设计目标,以翼根弯矩增加量小于5%为约束,以商用飞机的巡航状态为设计状态,对所设计的新型小翼进行优化。本文首先根据小翼特点,确定小翼翼型的选择标准,然后通过叠加Hicks-Henne函数方法优选得到合适的翼型。其次,利用基于NURBS原理的自由曲线构造小翼的前后缘线,最后利用曲面扫掠形成模型。第三,考虑到涡格法计算速度快,CFX计算精度高,全局优化范围广,分级优化能降低优化规模,本文将它们组合成两种策略:基于涡格法的全局优化、基于CFX的分级优化。同时,加入基于涡格法的分级优化用于对比,全局优化分为后缘有约束和无约束两种设计。最后,对优化结果进行分析,将其与简单增展机翼的减阻效果和机理进行对比。结果表明:本文所设计的翼梢小翼通过不同优化策略得到的小翼都有良好的减阻效果,其中后缘有约束的全局优化得到的小翼和基于CFX的分级优化得到的小翼分别减阻力7.02%和6.7%。在近场,简单增展机翼能够使翼尖涡远离机翼,而翼梢小翼不仅如此,还能将较强翼尖涡分散成强度降低的涡。在远场,小翼和简单增展机翼都没能加快翼尖涡消散。更多还原

【Abstract】 Application of winglet on transport will lead to improvement of aerodynamic characteristics for it is able to reduce induced drag of wing. However, Wing Root Bending Moment (WRBM) will also increase due to the winglet, and then the structure of wing has to be adapted. NURBS curve controlled by a lot of number is able to from various forms, thus it is suit for modeling a novel winglet. Airfoil used in the model of winglet should be selected particularly for it has large effect on the performance of winglet. Besides, the calculating method and strategies of optimization used in optimal design have direct influence on the results.The design target of the optimization of winglet modeled in this paper is to reduce the drag of wing with winglet, which subjects to the constraint that the percent of increase of WRBM should be less than 5%, and the design status is cruise phase of commercial aircraft. Firstly, the criteria of choosing suitable airfoil is setup according to the feature of winglet, and then a good airfoil is carried out by Hicks-Henne function method. Secondly, surface model of winglet is established by couple of freestyle curve based on NURBS and airfoil chose in CATIA. Thirdly, considering that Vortex Lattice Method (VLM) is a fast method, CFX is of high fidelity, global optimization is able to search in large scale; stratified optimization can reduce the amount of calculation, this paper put them into two strategies: Global Optimization based on VLM and Stratified Optimization based on CFX. To make some comparison, stratified optimization base on VLM is also adopted in Optimization of winglet; Global Optimization based on VLM with the constraint of trailing edge in small range is also conducted. Finally, the flow field of winglet and simple extension of wing with same span are analyzed and compared to figure out the mechanism of winglet reducing drag. The results indicate that:Winglets designed in this paper via different methods and strategies achieve large reduction of drag, particularly winglet designed by global optimization with constraint and the one by stratified optimization based on CFX reduce drag by 7.02% and 6.7% respectively. Winglet can reduce drag by scattering the strong tip vortex into several vortex of less strength in the neighborhood of wingtip and moving the tip vortex away while simple extension of wing can only move vortex away. However, in far field, all of winglets and extension of wing have little effect on scattering wingtip vortex.更多还原