安防监控系统防雷设计要点

根据住宅小区安防监控系统的雷击事故案例,对安防监控系统受雷击主要原因以及雷电可能的侵入途径进行了分析,阐述安防监控系统防雷设计要点,以及日常使用维护过程应注意的问题.     

应力路径法控制5万m3油罐地基稳定

介绍了一种直观评判油罐地基稳定性的方法,即应力路径法.应力路径为应力点在应力空间的运动轨迹,分为总应力路径TSP和有效应力路径ESP.应力路径法的解题思路,先建立土体的破坏临界状态线(kf线),对比非线性弹性模型计算典型土体单元在加荷过程中的应力路径,根据p-q平面上的破坏准则得出地基稳定性安全系数Fs.应力路径法最大优点是简单且直观,作为现场控制地基稳定手段十分方便.     

Water-tank experiment on the thermal circulation induced by the bottom heating in an asymmetric valley

Water tank experiments were carried out to investigate the thermal convection due to the bottom heating in an asymmetrical valley under neutral and stably stratified approach flows with the Particle Image Velometry (PIV) visualization technique. In the neutral stratification approach flow, the ascending draft induced by bottom heating is mainly located in the center of the valley in calm ambient wind. However~with ambient wind flow, the thermal convection is shifted leeward, and the descending draft is located on the leeward side of the valley, while the ascending draft is located on the windward side. The descending draft is minorly turbulent and organized, while the ascending draft is highly turbulent. With the increase of the towing speed, the descending and ascending drafts induced by the mechanical elevation begin to play a more dominant role in the valley flow, while the role of the thermal convection in the valley airflow becomes limited. In the stable stratification approach flow, the thermal convection is limited by the stable stratification and no distinct circulation is formed in calm ambient wind. With ambient wind, agravity wave appears in the upper layer in the valley. With the increase of the ambient wind speed, a gravity wave plays an important role in the valley flow, and the location and intensity of the thermal convection are also modulated by the gravity internal waves. The thermal convection has difficulty penetrating the upper stable layer. Its exchange is limited between the air in the upper layer and that in the lower layer in the valley, and it is adverse to the diffusion of pollutants in the valley.     

对流槽湍流涡旋结构特征的小波分析

为研究夹卷层的湍流特性,用对流槽模拟大气对流边界层并做湍流温度测量.能谱分析表明,混合层湍流谱幂律接近“-5/3”次律;而夹卷层湍流谱幂律有明显的分段特征.利用离散正交小波对其湍流脉动信号进行去噪和尺度分解,将原始信号分成均匀各向同性小尺度涡旋成分和大尺度涡旋成分,并对分解后的信号做能谱分析.结果表明,不论是在混合层还是在夹卷层,小涡都能很好地满足Kolmogorov的“-5/3”次律;而大尺度涡旋则在混合层和夹卷层中表现出不同的特征.     

Benchmark computations of wave run-up on single cylinder and four cylinders by naoe-FOAM-SJTU solver

The benchmark simulations of wave run-up on a fixed single truncated circular cylinder and four circular cylinders are presented in this paper. Our in-house CFD solver naoe-FOAM-SJTU is adopted which is an unsteady two-phase CFD code based on the open source package OpenFOAM. The Navier-Stokes equations are employed as the governing equations, and the volume of fluid (VOF) method is applied for capturing the free surface. Monochromatic incident waves with the specified wave period and wave height are simulated and wave run-up heights around the cylinder are computed and recorded with numerical virtual wave probes. The relationship between the wave run-up heights and the incident wave parameters are analyzed. The numerical results indicate that the presented naoe-FOAM-SJTU solver can provide accurate predictions for the wave run-up on one fixed cylinder and four cylinders, which has been proved by the comparison of simulated results with experimental data.     

波浪水槽中振动格栅湍流特征的实验研究

在波浪水槽中采用格栅振动的方式产生湍流,研究振动格栅产生湍流的特征。本文开展了4类实验,调节测量点到格栅平均位置的距离、格栅振动频率、振动冲程,采用ADV测量水体中单点的脉动速度。实验结果显示,湍流强度在一定范围内随离格栅距离的增大而逐渐减小,随着振动频率的增大而呈幂指数增大,随着振动冲程的增大而呈幂指数增大。同时还比较了两个不同格栅产生湍流的不同。结果显示,在波浪水槽中,振动格栅产生湍流的强度还与格栅的长度尺寸有关,这与在水箱中振动格栅产生湍流的特征不同。     

An Experimental Investigation on the Dynamic Response of a Damaged Ship with a realistic arrangement of the flooded compartment

The dynamics of a damaged ship in waves is a complex phenomenon regarding fluid and structure interactions. Flooded water motions in the damaged compartment could be influenced by decks, obstructions and obstacles in the compartment. This becomes particularly relevant in case of flooding in the engine room that is usually characterized by the presence of large objects such as engines and machineries. In such cases the possibility to better understand the behavior of a damaged ship, influenced by the fluid and structure interactions, could provide novel outcomes and thus enhance the damaged ship safety.In this paper an experimental campaign is conducted on a passenger ferry hull. The effects of obstacles in the engine room compartment, such as decks and engines, on ship roll responses, are studied. Roll decay in still water and steady roll responses in beam regular waves at zero speed are measured for the empty compartment and for the compartment with obstructions, as defined above.The main outcomes from the conducted experiments disclose a mitigation of the resonant behavior of the coupled system, ship with damaged compartment, by having engine shapes occupying the flooded engine room. Moreover it is possible to observe how the resonant frequency of the ship modifies having a more realistic arrangement of damaged compartment and how motion RAOs and roll decay characteristics modify accordingly.     

Neyman-Pearson决策准则及在海洋风暴潮预报中的应用

给出了Neyman-Pearson全局预报方法,以期在保持一给定虚警率的前提下提高预报率。增加了算法的实用性,使算法能够适合真实环境。该方法用于海洋风暴潮预报,能够较好地平衡预报率与虚警率间的关系。     

泥石流的径流量与流量分布特征

在泥石流危险度评价中，泥石流的规模和频率通常被视为最重要的两个特征因子，但在区域性的研究中，两者之间的关系并没有充分地表现出来。利用蒋家沟的大量观测数据，对流量、径流量这两个最能反映泥石流规模的参数，进行统计分析，分析流量与径流量的分布特征，从一个侧面反映泥石流规模和频率之间的关系。结果表明，尽管频率随流量和径流量规模的增大而减小，但在定量上，不同事件之间存在明显的差异，这是由泥石流的自身特征决定的，因而分布特征也反映了泥石流活动的本质。     

液压阻尼系统控制浮放立式储罐提离失稳

立式圆柱储罐在油田、石油化工等企业用途广泛，多用作存贮易燃、易爆介质，一旦遭遇震害，后果将十分严重。本文针对浮放立式储罐地震响应的提离失稳问题，采用液压阻尼系统（HDS）用以控制储罐的提离反应，建立了安装HDS储罐的力学分析模型并进行了数值计算，对安装HDS后储罐的提离反应进行了分析。仿真计算结果表明：HDS可以有效地减小提离应力，从而地震烈度可以降低1度进行储罐的提离设计。