单层柱面网壳结构抗风敏感度研究

以风敏感度概念为基础,对结构风敏感度计算理论中的若干关键问题进行探讨,并对相关计算方法进行改进,推导了背景效应系数、耦合效应系数以及系统应变能等公式。以单层柱面网壳结构为研究对象,系统研究了跨度、杆件截面、矢跨比、约束形式等参数对结构风敏感度的影响,建立了单层柱面网壳结构风敏感度分级体系。研究发现:单层柱面网壳结构风敏感度主要受结构刚度和振动模式的影响,实际设计中可通过结构自振基频、矢跨比和约束形式三个参数来判断;以结构自振基频等于1.5 Hz作为分界线,小于该值时结构共振响应较大,需进行结构动力分析,大于该值时结构以背景响应为主,据此提出了以背景响应为基础的简化风致振动计算方法。

结构抗风设计敏感性分析

从结构随机风振分析的基本理论出发,通过对脉动风荷载特性与结构动力特性的探讨,提出了影响结构风振响应的3种关键效应,即尺度效应、频率效应和模态效应,推导了表征这3种关键效应的无量纲系数;在此基础上,提出了结构风敏感度的概念,并推导了以系统应变能为响应指标、以尺度效应系数、频率效应系数和模态效应系数表示的结构风敏感度计算公式;通过对典型屋盖结构的风敏感度分析,验证了相关理论的正确性。研究表明,风敏感度概念反映了结构的风振响应本质特征,实现了对结构风敏感性问题的客观、定量描述,是对现有结构抗风设计理论的一个补充。

基于连续伴随的汽车后视镜风噪敏感度分析方法

后视镜回流区内湍流流动产生的Lighthill体声源是车内风噪声的重要来源。采用连续伴随方法,以体声源强度为目标函数对汽车后视镜进行了风噪敏感度分析研究。通过风噪敏感度分析得出后视镜敏感度云图,用于指导后视镜的优化设计,从而减小由后视镜带来的气动噪声。使用开源软件OpenFOAM对某车型后视镜单体完成网格划分、流场计算以及敏感度分析,并通过对后视镜流场进行分析以论证所得到的敏感度云图的正确性。结果表明,基于连续伴随的敏感度分析方法可以有效地计算风噪敏感度并应用于风噪优化。

Sensitivity of WRF simulated typhoon track and intensity over the Northwest Pacific Ocean to cumulus schemes

Here discussed is the sensitivity of simulated typhoon track and intensity over the Northwest Pacific Ocean to different cumulus schemes.The results from the 20 typhoon cases during 2003-2008 show that the simulation of typhoon track and intensity are very sensitive to cumulus schemes.The relationship between simulations of typhoon track and cumulus schemes can be case dependent.Different best tracks obtained from different case studies depend on which cumulus scheme we chose.However,simulations of typhoon intensity exhibit different features.The Kain-Fritsch scheme simulation obtains the most intensive typhoon,whereas the Betts-Miller-Janjic scheme and the Grell-Devenyi scheme obtain weaker typhoons.The sensitivity of simulated typhoon track and intensity to different cumulus schemes is due mainly to different hypotheses and precipitation calculations.The difference of simulated large scale circulations using different cumulus schemes leads to the difference of typhoon tracks.The closer the simulations are compared to observations,the less the errors of simulated typhoon tracks.The difference of simulated typhoon intensity is due mainly to the difference of simulated vertical heating of the atmosphere.These lead to different strengths of convection which causes the difference of cumulus precipitation and latent heat.The KF scheme simulation obtains the strongest vertical convection,the obvious warm core structure,more cumulus precipitation,and stronger intensity.By contrast,the BMJ scheme and the GD scheme obtain weaker convection,less cumulus precipitation,and weaker intensity.