应用于翼型绕流的线性/非线性湍流模式的研究

本文选取了四个线性湍流模式、四个非线性涡粘性湍流模式和一个显式代数应力模式对绕翼型的不可压缩分离流动进行了数值模拟.因计算鲁棒性的需要,其中部分模式在壁面附近耦合了一方程模式.通过与实验结果的比较,对翼型在大攻角情况下流动产生分离的气动特性进行了评估.计算结果表明,非线性模式能够较好地反映湍流的各向异性和曲率影响.     

用非线性涡粘性模式计算三维湍流边界层

针对非线性涡粘性模式在求解三维湍流边界层流动时的不足，本文从压力－变形率关联项中的快速项出发，考虑流动非均匀影响，在显式代数应力模式的雷诺应力表达式中引入了反映雷诺应力“松驰”效应的速度二阶导数项，构造了一个新的非线性涡粘性模式。通过对典型算例－翼体角隔流动的计算结果表明，新模式能较好地再现出三维湍流边界层内雷诺切应力方向的发展滞后于速度梯度方向发展这一流动特性。     

一种新的非线性K-ε两方程湍流模型

本文基于理论分析和对标准Ｋ－ε两方程湍流模型数值模拟结果的分析,在标准Ｋ－ε两方程模型的雷诺应力表达式中加入６高阶非线性项;并在模型的涡粘性系数μ１中考虑流动各向异性的影响,将涡粘性系数中参数Ｃμ取为表征流动各向异性的参数Ａ的一个线性函数,从而得到了一个新的非线性Ｋ－ε两方程湍流模型。     

多尺度湍流模式在压缩拐角绕流中的应用

 应用4 个多尺度涡粘性湍流模式对一个二维压缩拐角流动进行了数值模拟,通过与实验结果以及两个基准模式(一个单尺度k-ε两方程模式和一个零方程模式) 的计算结果的比较,结合压缩性对湍能输运的作用、湍流的非平衡性对多尺度湍流模式在拐角非平衡湍流中的应用进行了评估。     

超声速燃烧的湍流流场数值模拟

选择了6个有代表性的湍流模型,对超声速燃烧湍流流场开展了数值模拟.采用的模型包括5个线性涡粘性模型和1个非线性模型,在非线性模型中同时引入了可压缩修正.数值结果表明,本文发展的数值方法可以成功地应用于求解可压缩、含化学反应的多组分N-S方程.同时引入可压缩性修正的二阶涡粘性模型给出的结果较好.     

低雷诺数κ-ε封闭模式在三维湍流边界层计算中的应用

本文采用低雷诺数形式的k-ε湍流模型,计算具有大横向流的不可压缩三维湍流边界层。在湍流模型中,应用了涡粘性的各向异性系数。本文所得结果与用混合长模型所得结果以及量测结果的比较表明:对于边界层的不同特征量,湍流模型和涡粘性各向异性对计算结果的影响程度是不同的。总的来说,应用考虑涡粘性各向异性的k-ε模型,较之应用混合长模型,所得计算结果有所改善,但还不是根本性的改善。     

翼型动态失速的数值研究

用不可压缩流动的求解算法，结合WilcoxDC提出的k－ω模式和k－ωSST湍流模式，对翼型的动态失速进行了数值模拟。通过对典型的振荡翼型轻失速和深失速算例的计算结果分析可以看出：（1）绕动态失速翼型的流场结构十分复杂，轻失速和深失速在流动特性上有很大区别。计算结果显示：轻失速主要是由于后缘分离引起，分离涡的影响范围主要是在后缘附近。而深失速则首先形成很大的前缘分离涡，该分离涡在翼型表面上运动，并诱发出二次分离涡，引起翼型升、阻力系数的显著变化。（2）对于动态失速的翼型绕流，k－ωSST湍流模式是较为有效的，计算出的气动力系数迟带曲线变化趋势与实验结果符合得比较好。     

洁净室流场大涡模拟

应用湍流大涡模拟方法对矢流洁净室和全顶棚送风下部两侧回风式洁净室进行了数值模拟。计算中使用了隐含流线抑风耗散作用的具有三阶部分展开的Taylor-Galerkin离散格式，导出了经Gauss滤波后的基本方程组的有限元列式，应用涡粘性亚格子模式的湍流大涡模拟方法进行数值模拟。数值计算结果与实验结果符合较好，表明湍流大涡模拟能够较准确地捕捉到洁净室流场中旋涡的位置和尺度，在洁净室的数值仿真方面，与标准的K－ε湍流模式相比，湍流大涡模拟结果具有较高的可靠性。     

湍流附面层方程的有限差分解

本文用三点隐式有限差分法数值求解了轴对称流动的层流、转捩和湍流可压缩附面层方程,湍流附面层用两层概念处理,而每一层用适当的涡粘性模型代替Reynolds应力项,用常值湍流Prandtl数将湍流热流项与Reynolds应力关联起来。支配方程用迭代法求解。计算结果表明,采用本文改进的涡粘性模型和涡粘性分布的平滑办法,对文中所计算的几种情况,都给出了满意的结果。     

Sajben跨声速扩压器分离流动中湍流模式数值研究

为研究湍流模式对激波/湍流边界层干扰内流流动的影响,提高数值计算准确度,使用SA,SST k-ω,非线性EASM k-ω,Gao-Yong四个湍流模式对Sajben扩压器内激波/湍流边界层干扰流动进行了数值计算。对流项采用Roe格式离散,扩散项采用二阶中心格式离散,离散后的控制方程用多步Runge-Kutta显示时间推进法求解。文中展示了四个湍流模式计算得到的壁面压力、速度剖面、摩阻系数等分布。计算值与实验值符合很好,四个湍流模式总体上能够较好地模拟扩压器内激波/湍流边界层干扰复杂分离流动。Gao-Yong湍流模式对分离区内的压力、速度型的模拟更加准确,而非线性EASM k-ω模式对分离再附点位置计算最理想。     

ν-gap度量及其在飞行控制律评估中的应用

 传统控制律评估方法主要用于单输入单输出（SISO）系统，且对模型参数摄动考虑不够全面,针对这些不足，研究了ν-gap度量方法。在介绍系统广义稳定裕度相关概念的基础上，给出了ν-gap度量的定义、特点和性质以及近似摄动模型的计算，提出ν-gap度量评估控制律的步骤。实例结果表明，该方法不仅克服了上述传统评估方法的缺陷，而且还有根据所求的各摄动影响情况忽略影响小的元素，以减少计算量及可以找到最坏情况下的参数摄动组合等优点。     

Integrated Entry Guidance for Reusable Launch Vehicle

A method for the implementation of integrated three-degree-of-freedom constrained entry guidance for reusable launch vehicle is presented. Given any feasible entry conditions, terminal area energy management interface conditions, and the reference trajectory generated onboard then, the method can generate a longitudinal guidance profile rapidly, featuring linear quadratic regular method and a proportional-integral-derivative tracking law with time-varying gains, which satisfies all the entry corridor constraints and meets the requirements with high precision. Afterwards, by utilizing special features of crossrange parameter, establishing bank-reversal corridor, and determining bank-reversals according to dynamically adjusted method, the algorithm enables the lateral entry guidance system to fly a wide range of missions and provides reliable and good performance in the presence of significant aerodynamic modeling uncertainty. Fast trajectory guidance profiles and simulations with a reusable launch vehicle model for various missions and aerodynamic uncertain-ties are presented to demonstrate the capacity and reliability of this method.     

基于飞机油箱模型形状特征油量测量切片步长选择方法研究

 在分析飞机数字式油量测量过程中目前广泛使用的切片法油量测量原理的基础上,针对现有的定步长切片法无法得到准确、可靠的燃油质量特性数据库的缺陷,结合对飞机油箱模型形状特征的分析,提出了基于飞机油箱模型形状特征的油量测量切片步长选择方法。此方法包括切片步长整体和局部选择两个过程,整体选择以实现相邻两切片平面所夹油箱模型体积近似相等为目的来确定切片步长,以体现油箱模型截面整体变化规律;局部选择以设计切片平面与截面突变平面重合或尽可能接近的方式,突出油箱截面的局部变化特征。实验结果表明：该切片步长选择方法较定步长方法能够建立更为合理、可靠的燃油质量特性数据库,从而提高了油量测量精度。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

二维翼段颤振的μ控制

 采用超声电机作为作动器来实现含控制面的翼段颤振鲁棒抑制。针对作者设计的二维翼段颤振主动抑制系统，通过理论与实验相结合的方法，建立了考虑沉浮方向阻尼和作动器模型参数不确定性的控制系统模型，设计了μ控制器，并对控制器做了降阶处理。数值仿真和风洞试验表明，μ控制器可有效地抑制颤振的发生，将颤振临界速度提高23.4%。相对于H_∞控制器，μ控制器的控制效果和鲁棒性更好。     

航空发动机管路测量数据分割方法

 为了提高航空发动机管路测量数据的反求建模效率,提出了一种区域增长分割算法。该方法主要是利用管路表面在曲面索引系数映射、主曲率映射、高斯映射上的特性,并基于均值漂移算法和遗传算法提出了区域分割算法中种子区域的选择策略。然后利用区域增长分割方法实现了对管路测量数据的分割。经过仿真和实测数据验证,所提管路分割算法具有较好的分割质量和效率。     

Abnormal Shape Mould Winding

为解决网格化芯模的缠绕问题,本文提出了复合材料面片缠绕机理;接着详细分析了面片缠绕过程中的芯模凹曲面上纤维滑线和架空现象,应用微分几何曲面理论和空间几何理论,提出判据及其解决方案;最后,针对飞机发动机进气道的缠绕成型,编制缠绕控制程序并进行相应的实验,验证了面片缠绕方法的可行性。     

Interfacial Properties Modification of Carbon Fiber/ Polyarylacetylene Composites

This work was dedicated to performing surface oxidation and coating treatments on carbon fibers (CF) and investigating the changes of fiber surface properties after these treatments, including surface composition, relative volume of functional groups, and sur- face topography with X-ray photoelectron spectroscopy (XPS) and atom force microscopy (AFM) technology. The results show that, after oxidation treatments, interfacial properties between CF and non-polar polyarylacetylene (PAA) resin are remarkably modified by removing weak surface layers and increasing fiber surface roughness. Coating treatment by high char phenolic resin solution after oxida- tion makes interface of CF/PAA composites to be upgraded and the interfacial properties further bettered.     

Thermal Stresses and Cracks During the Growth of Large-sized Sapphire with SAPMAC Method

本文利用有限元法对冷心放肩微量提拉法(SAPMAC)生长大尺寸蓝宝石单晶过程中的热应力进行了模拟计算,应用临界缺陷理论解释了裂纹的萌生与扩展机理。研究表明,晶体内的热应力主要与晶体生长速率,环境温度和结晶取向有关;较大热应力多出现在结晶界面,放肩、收尾以及直径急剧变化等位置;最大热应力总是出现在籽晶与新生晶体的界面附近。裂纹将在临界缺陷位置产生,并在应力作用下沿a或m面扩展。计算结果与实验结果基本吻合,通过晶体生长系统和生长工艺的改进,对晶体的开裂问题得到了有效的抑制。     

Optimization Design System for Composite Structures Based on Grid Technology

To solve the topology optimization of complicated multi-objective continuous/discrete design variables in aircmit structure design, a Parallel Pareto Genetic Algorithm （PPGA） is presented based on grid platform in this paper. In the algorithm, the commercial finite element analysis （FEA） software is integrated as the calculating tool for analyzing the objective functions and the filter of Pareto solution set based on weight information is introduced to deal with the relationships among all objectives. Grid technology is utilized in PPGA to realize the distributed computations and the user interface is developed to realize the job submission and job management locally/remotely. Taking the aero-elastic tailoring of a composite wing for optimization as an example, a set of Pareto solutions are obtained for the decision-maker. The numerical results show that the aileron reversal problem can be solved by adding the limited skin weight in this system. The algorithm can be used to solve complicated topology optimization for composite structures in engineering and the computation efficiency can be improved greatly by using the grid platform that aggregates numerous idle resources.