Study on the dynamic response of polyurea coated steel tank subjected to blast loadings

Steel tanks are widely used in the storage of various chemical liquids, and the blast resistance of the tanks is very important because of the explosiveness of these liquids. To explore a feasible method to improve the blast resistance of steel tanks, the effect of polyurea coating on the blast resistance of steel storage tank is investigated in this paper. The responses of monolithic steel tanks and polyurea coated tanks under blast loads are studied by field blast experiments using TNT explosive, and the results shows that the polyurea layers are effective in reducing the maximum and residual displacements of the tank. Numerical simulations are performed and validated, and the deformation process and stress and strain distribution of the tanks are analyzed accordingly. The increase on the bending moment of the plastic hinge lines of the tanks and the increase of the area density of the cylindrical shell induced by the polyurea layers are believed to be the two main factors contributing to the displacement reduction effect of polyurea in this paper. The validated numerical model is used to study the influence of polyurea layer's thickness on the deflection of the tank, and a nearly inversely proportional relationship between the thickness and the maximum displacement is found. Three deformation modes of the tanks are identified when subjected to blast load with varying intensity and it is found that the displacement reduction effect of polyurea varies in different deformation modes.     

Large eddy simulation and experimental study of the effect of wire mesh on flame behaviours of methane/air explosions in a semi-confined pipe

Preventing the propagation of flames in a pipeline is an effective measure for avoiding gas explosion accidents and reducing losses. To evaluate the effect of wire mesh, acting as a porous media, experimental and simulation studies are conducted to determine the influence of the wire mesh on the dynamics of premixed methane/air flame propagation in a semi-closed pipe. Four different kinds of wire mesh with different numbers of layers are chosen in the experiments and simulation, and the mechanism of wire mesh quenching of the flame is investigated. The experimental and simulation results are consistent. Flames are quenched when 4 layers of 40-mesh or 3 layers of 60-mesh wire mesh are used; however, once the flame propagates through the wire mesh, the risk of methane combustion may increase. The wire mesh becomes the key factor causing flame folds and acceleration, and the greater the number of layers or the larger the mesh size is, the more obvious the folds after the flame passes through the wire mesh. Moreover, the combination of heat absorption and disruption of the continuous flame surface by the mesh causes flame quenching. Wire mesh can effectively attenuate the flame temperature during premixed flame propagation in a pipe, and the attenuated maximum rate reaches approximately 79% in the case of adding 3 layers of 60-mesh wire mesh.     

考虑儿童运动特性的小学教学楼楼梯间人员疏散研究

为研究小学教学楼楼梯间人员运动行为以及影响人员疏散的因素,开展人员疏散实验并构建疏散模拟场景。基于疏散实验研究不同实验场景的出口流量和人员运动速度,通过疏散仿真模拟,分析不同人员运动速度、人员数量及疏散策略对疏散的影响。结果表明:排队下楼的人员运动速度比紧急疏散人员低22.7%,自由上楼人员运动速度比排队上楼人员高8%;人员总疏散时间随人员运动速度的增加而降低,但总疏散时间随速度增加而降低的幅度变小;加入分层疏散策略会增加人群疏散总时间,但整个疏散过程人员分布均匀,在建筑瓶颈不易产生人员过度拥挤现象,因而在疏散过程中应适当采用分层疏散策略。     

缝洞型管道瓦斯爆炸特性数值模拟研究

为探究采空区遗煤、松散破碎岩块对瓦斯爆炸的影响,建立缝洞型管道模型,采用数值模拟与理论分析结合方法研究采空区内缝洞型管道内瓦斯爆炸的传播规律及管道长径比对瓦斯爆炸过程中速度与冲击波的影响。研究结果表明:在缝洞型结构内,随着火焰沿管道向前传播,各监测点速度逐渐变大、压力先增加后降低,而压力上升速率则表现出不规则的变化;缝洞结构加剧了火焰燃烧的剧烈程度,提高了管道内各监测点的温度峰值;在缝洞型管道内随长径比r增加,各监测点最大压力峰值以及速度大小依次降低。     

波浪与抛石潜堤相互作用的MPS法数值模型研究

为了研究波浪与抛石潜堤相互作用过程中大自由表面变形和堤内渗流等强非线性紊流运动问题,利用改进的MPS法,建立了模拟波浪与抛石潜堤相互作用的MPS法数值计算模型。模型将抛石潜堤假定为均质多孔介质,采用Drew的二相流运动方程描述多孔介质内外的流体运动;通过在动量方程中增加非线性阻力项,并引入亚粒子尺度紊流模型,模拟波浪与可渗结构物相互作用过程中的紊流运动。选取“U”型管中多孔介质内渗流过程和孤立波与可渗潜堤相互作用两个典型的渗流问题,通过将数值计算结果与理论解和实测值的对比分析,对所提出的MPS法紊流渗流模型的模拟精度进行验证。结果表明：基于改进的MPS法构建的垂向二维紊流渗流模型可以很好地再现 “U”型管中多孔介质内渗流以及波浪作用下可渗潜堤内外的复杂流场,显著缓解流-固界面处的压力震荡与粒子分布不均匀问题,实现了较高的模拟精度。     

Community-Based Environmental Management in Atlantic Canada: The Impacts and Spheres of Influence of the Atlantic Coastal Action Program

The Atlantic Coastal Action Program (ACAP) is a unique, community-based program initiated by Environment Canada in 1991 to help Atlantic Canadians restore and sustain watersheds and adjacent coastal areas. ACAP is the eastem-most Environment Canada Ecosystem Initiative. The ACAP family is currently made up of 14 ecosystem-based organizations in the four Atlantic provinces. Each one of these non-profit organizations operates independently, but is formally linked under the umbrella of ACAP to represent a force stronger than the individual parts. In Environment Canada's experience, the program consistently demonstrates the value of a community-based approach and produces results on an ecosystem basis. This paper will examine some of the impacts of ACAP in terms of economics, credible community science, and environmental results which most often align with Environment Canada's objectives. It will explore the influences of the community-based approach to environmental management on multiple scales (local, regional, etc.). Through examples, the paper will demonstrate the effectiveness of ACAP in influencing some of the policies, programs and attitudes of various levels of government and industry in the region, as well as describe how the community-based model has been exported internationally. The paper will conclude with a discussion on a planned path forward for ACAP.     

A Simulation Study to Assess the Sensitivity of a Forest Health Monitoring Network to Outbreaks of Defoliating Insects

The sensitivity of the United States Forest Health Monitoring network to outbreaks of defoliating insects was examined by means of a simulation study. A model constructed specifically for the study was used to generate a wide variety of defoliation patterns in forested landscapes. Forest configuration was that of Minnesota, USA, as expressed by the GAP land cover classification. Combinations of model parameters were based on a Latin Hypercube sample. The relationship between the average number of plots defoliated and outbreak characteristics was then examined via multiple regression. Both theoretical and model results pointed to a strong, linear relationship between the average number of plots defoliated and outbreak size. Model results provided additional insight, suggesting a significant relationship between the average number of plots defoliated and other outbreak characteristics after outbreak size was taken into account.     

气象条件对静电除尘器低温腐蚀的影响分析

在已建成投产的静电除尘器当中,低温腐蚀是严重影响除尘器使用寿命的因素之一。以某烧结厂静电除尘器为研究对象,利用CFD软件,采用标准k-ε湍流模型对除尘器内部流场及温度场的分布进行数值模拟研究,得到静电除尘器内部流场和温度场分布特征,分析这些数据可知除尘器温度最低部位位于灰斗处,外界气温对壳体温度具有正相关的影响,在此基础之上有针对性地提出对静电除尘器壳体低温腐蚀的防治措施。     

Effects of falling weight impact on industrial safety helmets used in conjunction with eye and face protection devices

Industrial workplaces pose concurrent hazards to the upper part of the head and the eyes. Under the circumstances, workers may use protective helmets in conjunction with protective goggles or spectacles. In order to assess the compatibility of this equipment, a method and a test stand for evaluating the behavior of safety helmets and protective goggles/spectacles upon the impact of a falling weight were designed. The results of tests concerning the displacement and deformation of helmets and spectacles/goggles, the forces acting on the helmets, as well as the forces exerted by the spectacles/goggles on the headform upon falling weight impact are presented. The results revealed the ways in which the tested equipment interacted with each other. The influence of equipment construction on the test results was analyzed and inferences concerning the safety of the studied protective devices were made. Some general construction guidelines were formulated for the compatibility of the equipment.     

基于FDS的加油站便利店火灾模拟

为了研究加油站便利店火灾的发展规律,选择合理的疏散路线,使用 FDS软件对某加油站便利店进行火灾数值模拟。通过观察烟气扩散和动态升温过程,分析便利店的烟气扩散和升温规律,对比分析不同疏散路线上温度、烟气层高度和能见度的数据变化规律,分析选择不同疏散路线对人员安全疏散的影响。结果表明:在无火灾报警设备的情况下,卫生间等有隔断的设施会延迟设施内人员获得火灾信息的时间,不利于安全疏散;同等高度下靠墙区域受高温烟气影响较中央开阔区域更大;疏散时选择合理的疏散路线可以显著延长安全疏散时间。