Transonic Aeroelastic Numerical Simulation in Aeronautical Engineering

A lower-upper symmetric Gauss-Seidel (LU-SGS) subiteration scheme is constructed for time-marching of the fluid equations. The Harten-Lax-van Leer-Einfeldt-Wada (HLLEW) scheme is used for the spatial discretization. The same subiteration formulation is applied directly to the structural equations of motion in generalized coordinates. Through subiteration between the fluid and structural equations, a fully implicit aeroelastic solver is obtained for the numerical simulation of fluid/structure interaction. To improve the ability for application to complex configurations, a multiblock grid is used for the flow field calculation and transfinite interpolation (TFI) is employed for the adaptive moving grid deformation. The infinite plate spline (IPS) and the principal of virtual work are utilized for the data transformation between the fluid and structure. The developed code was first validated through the comparison of experimental and computational results for the AGARD 445.6 standard aeroelastic wing. Then, the flutter character of a tail wing with control surface was analyzed. Finally, flutter boundaries of a complex aircraft configuration were predicted

Study on Parallel Computation and Load Balance Strategy Based on Multiblock Structured Grid

从并行计算流体力学程序的稳定性和效率两大问题入手,针对多块结构网格的通用数据传输方法和基于遗传优化算法的负载平衡方法,并在已有串行多块结构网格程序基础上发展了相应的并行程序。该并行程序以物理区域分割为基础,采用MPI实现消息传递,适用于各种不同的并行机体系结构,具有很好的可移植性。大量数值实验证明,本文发展的并行程序具有良好的稳定性和并行效率,可以进一步应用于大规模实际工程计算

Prevalence and risk factors associated with HIV infection among female sex workers in Mengzi City

目的了解云南省蒙自市女性性工作者(FSWs)艾滋病病毒(HIV)的感染情况及HIV感染相关危险因素,为制定艾滋病防控策略和行为干预提供依据。方法于2010年10-11月采用方便抽样的方法,招募云南省红河州蒙自市娱乐场所FSWs,调查其社会人口统计学、行为学、HIV/AIDS知识以及生殖健康状况,并采集静脉血进行HIV血清学检测,分析FSWs人群HIV感染率及其危险因素。结果本次共调查423名FSW,HIV抗体阳性19人,HIV抗体阳性率为4.5%。最近一个月与客人发生性行为时坚持使用安全套的比例为87.0%。多因素分析显示,与HIV感染相关的危险因素为在低档性服务场所服务(校正OR=10.0,95%CI:3.77~26.67,P<0.001)和从事性服务时间≥2年(校正OR=3.8,95%CI:1.39~10.20,P=0.01)。结论蒙自市FSWs有较高的HIV感染率,在低档性服务场所服务及从事性服务时间长是HIV感染的危险因素,需针对低档和中高档FSWs的危险行为特征分别实施不同的干预措施,控制HIV的传播流行。Objective To explore the prevalence and risk factors of HIV infection among female sex workers( FSWs) in Mengzi City,Yunnan Province,so as to provide scientific evidence for formulating HIV prevention and control strategy and behavior intervention measures. Methods From October to November,2010,the convenience sampling method was used to recruit FSWs in the entertainment venues in Mengzi City in Yunnan Province to investigate their demographic information,sexual behavior,HIV / AIDS knowledge and reproductive health status. Venous blood was collected to test HIV. The prevalence and risk factors of HIV infection were analyzed. Results Totally,423 FSWs were recruited,among whom 19 were confirmed to be HIV antibody positive and the prevalence rate of HIV was 4. 5%. The proportion of the FSWs with consistent condom use when having sex with clients in the last month was 87. 0%. Multivariate logistic analysis indicated that the factors associated with HIV infection were working in low level sex work venues( adjusted OR = 10. 0,95% CI: 3. 77-26. 67,P < 0. 001) and time engaged in sexual work for 2 years or more( adjusted OR = 3. 8,95% CI: 1. 39-10. 20,P = 0. 01). Conclusions The prevalence of HIV is high among female sex workers in Mengzi City. FSWs who work in low-grade sex work venues and engage in sexual work for long time are at higher risk of HIV infection. Intervention measures targeted at dangerous behavior of FSWs working in different levels of sex work venues should be carried out to control the spread and prevalence of HIV / AIDS.国家“十一五”重大专项(2008ZX10001-003

Optimal windbreak design for wind-erosion in high-speed railway

It is also very important to improve resistant capabilities of wind resistance and structural stability of the windbreak while reducing train aerodynamic load. This article proposes a new type of windbreak with double-layer structure forming a cavity chamber with hole for energy dissipation of crosswind. Numerical simulation was used to analysis the wind protection effect of two kinds of windbreak and their own wind-resistance performance. The results showed that the two types of windbreaks can significantly reduce the train aerodynamic load under the action of crosswind, and the force act on the windbreak with cavity chamber structure is small than on another one with single layer structure. The new windbreak has better effect in aerodynamic load shedding for the train, stronger resistant capabilities of wind resistance and safety of structure. This new windbreak with cavity chamber will provides useful references for design of the wind protection system for high speed train. © 2013 Taylor & Francis Group

Numerical Algorithm of Euler Equations on Arbitrary Polyhedral Grids

发展并验证了一种新的支持多面体网格的欧拉方程离散算法,采用Fortran 95编写了支持任意网格拓扑及三维复杂外形的通用求解器。在空间离散上,基于径向基函数理论提出了一种新的梯度计算方法,并采用动能通量分裂格式来得到准确并且稳定的二阶精度重构。该方法不依赖于网格几何形状,因此对网格质量不敏感。由于在时间方向采用了点隐松弛推进方法,使得该求解器在大时间步长上仍能保持稳定性。最后通过若干数值算例对本文所发展的算法进行了验证,证明了本文的算法及求解器具有稳定、准确的特性及宽广的网格类型适应性

中国科学院力学研究所流固耦合系统力学重点实验室;

大展弦比机翼即使在正常的飞行状态下也会产生大变形,需要考虑几何非线性对静平衡位置与稳定性的影响。采用平板气动模型和非线性有限元,对大展弦比机翼进行非线性气动弹性分析。对于静变形问题通过多次迭代求解,划分多个气动平板,并让气动平板跟随结构变形,从而更新气动网格,反复迭代计算气动力和非线性结构变形直到收敛,这一过程通常在10步迭代内完成。计算结果表明在变形达到半展长20%前,线性结果与非线性结果差别小于5%。但结构大变形对动力学特性影响较大,故必须要考虑几何非线性对颤振的影响。给定来流速度求得平衡位置,再对结构动力学方程进行线化处理,利用线性理论中p-k法计算颤振边界,通常这样预测的颤振速度与原先..

双翼振动的预处理数值方法和性能研究(二)

本文利用非定常双时间NS方程的预处理方法对摆翼地效推进器进行了推力和推进性能的分析,结果显示沉浮振动的推力和效率与速度的变化关系表现出一致性;固定频率,改变速度,发现推力和效率存在极大值点;随着频率增大,极大值点右移。最大推力和效率的动力攻角为6°～9°,利用速度矢量图和压力云图显示了分离涡的输运和扩散,再一次展示了地效的存在

基于GA-GRNN的高速列车头型三维优化设计

针对CRH380A型高速列车头部外形的气动减阻问题, 设计了一种新型的基于自由曲面变形的局部型函数参数化方法, 提出了一套基于实数编码遗传算法的变光滑因子广义回归神经网络响应面模型(GA-GRNN)的气动外形优化方法. 优化结果表明: 局部型函数参数化方法操作简单、实现方便, 使用少量的设计参数可以控制较大变形区域, 且能保证变形的光顺性和不同变形区域间的光滑过渡; 使用同样的样本点进行训练, GA-GRNN 比GRNN的预测精度高, 更容易得到全局最优解; 优化后, CRH380A 三辆编组简化外形气动阻力减小8.7%, 本文提出的优化设计方法简单、高效, 为高速列车气动外形的工程优化设计提供了新思路