复合材料机翼结构的气动弹性优化设计与风洞颤振试验

Aeroelastic Optimization of a Composite Wing Structure and Wind Tunnel Flutter Test

本文介绍了一种用于复合材料机翼结构设计与优化的气动弹性剪裁方法。该方法应用所谓的双线性拉格朗日(Lagrange)形函数来创建用于复合机翼结构气动弹性剪裁的设计变量。目前常用的基于单元设计变量的方法使得蒙皮/翼梁/肋板的厚度分布不光滑,可能导致制造问题或应力集中。而形函数方法假设机翼蒙皮或沿着翼梁/肋板的厚度分布可以通过一组形状函数叠加。这样,设计变量就变成形函数的系数。在应用优化算法求解这些系数之后,可以通过将形函数叠加来确定每个单元的厚度,可保证相邻单元间厚度分布的平滑度。此外,应用基于计算流体力学(CFD)的颤振分析方法可精确地捕获跨声速颤振边界,并且在优化过程中可用作颤振约束。为了验证本文所介绍的气动弹性优化方法,优化设计了一个民用飞机复合机翼结构。其次,以优化后的机翼结构为基础,设计并制作了风洞缩比颤振模型,并进行了高速风洞颤振试验,以验证优化机翼结构的颤振特性。最后,风洞颤振试验成功验证了本文所提出的气动弹性优化设计方法的有效性。

This paper introduces an aeroelastic tailoring method for a composite wing structure design and optimization. This method applies a so called bilinear Lagrange shape function to create the design variables for aeroelastic tailoring of a composite wing structure. Comparing to the common element-based design variable approach which may generate a non-smooth thickness distribution on skin/spar that may introduce manufacturing problems or stress concentration, the shape function approach assumes that the thickness distribution on a wing skin or along a spar can be superimposed by a set of shape functions. In this way, the design variables become the coefficients of the shape functions. As a result, after the optimizer solves these coefficients, the thickness on each element can be determined by superimposing the shape function together, and the smoothness of the thickness distribution is guaranteed. In addition,a CFD based flutter method is applied to accurately capture the transonic flutter mechanism and utilized as the flutter constraints during the optimization. To illustrate the introduced aeroelastic optimization method, a composite wing structure of a transport aircraft is optimized and designed. Furthermore, based on the optimized wing structure, a scaled wind tunnel flutter model is thereafter designed and fabricated, and a high speed wind tunnel flutter test is implemented to validate the flutter mechanism of optimized wing structure. Finally, the wind tunnel flutter test result successfully demonstrates that the proposed aeroelastic optimization method is an efficient approach for aeroelastic tailoring application.