民机翼型跨音速风洞颤振模型的模态分析

民用飞机在跨音速区的颤振特性是其设计的关键限制之一，与飞机的安全性息息相关．跨音速颤振的计算会遇到激波、流动分离等高度非线性的气动问题，因此在计算跨音速颤振问题时往往把注意力放在气动力的计算精度上．但是，如果模态分析的计算精度不够，同样无法获得可靠的颤振计算结果．本文采用HyperMesh软件进行有限元建模，主要结构件均保留了原始结构的几何信息，通过设置材料密度模拟结构的质量分布．由NASTRAN软件的Lanczos求解器完成模态分析并给出主要关注的四阶模态，经过简单的有限元模型修正，使四阶模态的计算频率与试验频率一致，计算和试验的固有振型一致，为后续的跨音速颤振分析打下基础．

Modal Analysis of the Flutter Model of a Civil Airfoil in the Transonic Wind Tunnel

In order to select the blade surface parameters of the bulldozer properly, the EDEM software based on Discrete Element Method (DEM) was used to simulate the scraping process in this paper. Three different shapes of stone mixed material were selected as the bulldozed medium. The working resistances on three circular-arc blades with different curvature radii and two line-arc mixed blades during the horizontal bulldozing process were compared with each other. It is shown that the horizontal working resistance was the dominating resistance for all kinds of bulldozer surfaces. With the increase of curvature radii, the horizontal resistances of circular-arc blades decreased, and the vertical resistances changed from positive value to negative value gradually. In addition, the horizontal resistance of the arc-below-line mixed blade is always larger than that of the line-below-arc mixed one. The lateral resistances on all blades are nearly negligible.