NASA TrapWing高升力标模数值模拟研究

针对NASA TrapWing高升力全展襟翼构型,采用计算流体力学（ CFD）方法进行三维复杂流场仿真模拟,考察网格尺度和湍流模型对高升力模型气动特性的影响。采用“超立方体”概念,生成绕TrapWing模型的不同网格密度高质量多块结构网格,通过求解雷诺平均Navier-Stokes方程,研究网格尺度对高升力模型气动特性的影响。在此基础上选取中等规模计算网格,考察Spalart Allmaras和Menter k-ωSST湍流模型对高升力全展构型流场模拟能力,分析湍流模型对气动特性的影响。研究结果表明：网格策略具有较好的网格收敛性;湍流模型对翼稍附近位置上翼面压力系数的预测稍有影响,SA湍流模型预测的压力系数较SST更接近实验值。确认研究工作为大型飞机增升装置数值模拟提供了一定的参考。     

SA和SST湍流模型对高超声速边界层强制转捩的适应性

凸起物是高超声速流动中常用的一种人工转捩装置。采用高阶精度算法模拟了高超声速进气道压缩面上的强制转捩流动,转捩装置为一排高度为1mm的钻石型凸起物和斜坡型凸起物。考察了Spalart-Allmaras(SA)模型和剪切应力输运(SST)湍流模型对该问题的适应性。在考察过程中通过丰富的算例分析了网格规模、可压缩修正和空间离散格式等对计算结果的影响。在层流区,计算能与试验取得非常一致的结果。但在湍流区,计算得到的热流通常高出试验数据。经分析发现其原因是强制转捩的湍流边界层与自然转捩的湍流边界层在涡结构上存在较大差别,使得湍流模型的效果较差。针对高超强制转捩湍流涡结构丰富的特点,对SST湍流模型进行了修改。计算结果表明,该修改方法对提高热流精度具有一定效果。     

Comparison analyses on the 150 × 150 lunar gravity field models by gravity/topography admittance,correlation and precision orbit determination

We analyzed the 150 × 150 lunar gravity field models, LP150Q, GLGM-3 and SGM150, using the power spectrum on the lunar nearside and farside, the lunar global and localized gravity/topography admittance and correlation, and Chang’E-2 precision orbit determination to investigate which model is a more effective tool to estimate geophysical parameters and determine the lunar satellite precision orbit. Results indicate that all gravity field models can be used to estimate the lunar geophysical parameters of the nearside of the Moon. However, SGM150 is better in such computation of the farside. Additionally, SGM150 is shown to be the most useful model for determining the lunar satellite orbit.     

分级型进化算法及其在翼型跨声速气动优化中的应用

提出了变精度模型的分级型进化算法并对初始翼型为NACA0012的二维翼型进行了跨声速流动下的形状增升优化。借鉴自然进化中不同进化阶段个体适应度评估环境不同的机理,构造了分级精度模型以加速优化过程。对翼型进行了给定气动条件下的形状增升优化,给出了优化结果,并与传统基因算法及单精度模型算法结果进行了对比。     

Corner-milling of Thin Walled Cavities on Aeronautical Components

This article presents a mathematical model of helical end-milling forces through experimental identification of the cutting coefficients and analyzes the changes of corner-milling forces under different conditions. In allusion to the corner-milling process, the relationship between working parameters and the corner coordinates is investigated by way of combination of tool tracing and cutting geometrodynamics. The milling parameters are optimized by changing the coordinates of tool center and working parameters without altering cutting forces. By applying the optimized parameters to milling practice, a comparison is made to show the improved product quality. Based on these optimized parameters, a finite element method (FEM) program is used to compute deformation values of a workpiece's corner, which evidences few effects that optimized parameters can exert on the corner deformation.     

舰载飞机的滑跳起飞过程及其数学描述

简要地阐述了舰载飞机滑跳起飞的过程，给出了描述滑跳起飞跑道斜坡段形状的实用工程计算公式，并逐一建立了舰载飞机滑跳起飞在每个起飞阶段的运动方程，特别是在斜坡两轮滑跑段的运动方程（数学模型）。这些数学模型有助于分析舰载飞机滑跳起飞的动态特性。