浮顶式储油罐的爆炸冲击失效

通过模型实验与数值模拟结果对比,探讨了浮顶油罐在可燃蒸气云爆炸冲击作用下的变形过程和破坏机理。研究发现,罐体失稳破坏的主要原因与爆炸冲击波和油罐内液体的复合冲量作用有关,在爆炸冲击作用下浮顶油罐模型产生剧烈振动,迎爆面上部罐壁形成动应力集中现象,最终导致罐体失稳并产生内凹动力屈曲破坏。     

不同荷载模式下矿用救生舱受力性能的数值模拟

针对某煤矿井下救生舱,利用ANSYS和LS-DYNA软件建立救生舱、瓦斯/瓦斯煤尘和巷道三维有限元模型。分别进行了真实内瓦斯/瓦斯煤尘爆炸作用下救生舱流固耦合数值分析,等效三角波爆炸冲击荷载作用下救生舱动态模拟和静水压力荷载作用下救生舱的极限承载力和极限变形的数值计算,确定救生舱动/静态承载能力变化规律和变形模式,给出瓦斯/瓦斯煤尘爆炸超压与救生舱承载能力和变形模式的变化规律。研究结果表明,等效三角波爆炸冲击荷载作用下该救生舱整体结构的极限超压明显比流固耦合计算分析结果大,流固耦合计算分析结果更接近于实验结果。该救生舱满足爆炸冲击波荷载下的变形要求时,其在静水压荷载作用下的变形也能满足。     

用环形激波聚焦实现爆轰波直接起爆的数值模拟

利用基元反应模型和有限体积法对环形激波在可燃气体中聚焦实现爆轰波直接起爆进行了数值模拟。研究结果表明，标准状态下的氢气-空气混合气体在马赫数为3.1以上的环形激波聚焦产生的高温高压区作用下会诱发可燃气体的直接起爆形成爆轰波，爆轰波与激波和接触间断相互作用产生了复杂的波系结构；爆轰波爆点位置在对称轴上并不是固定的点，而是随着初始激波马赫数的变化而发生移动；可燃气体初始温度和压力对起爆临界马赫数都有影响，但是初始温度的影响大得多。     

惰性气体对氢氧混合气体爆轰性能的影响

将不同种类、不同浓度的惰性气体充入不同浓度的可燃气体中,用C—J理论和实验得到混合气体的爆轰参数,比较了惰性气体种类对可燃气体爆炸特征参数的影响;讨论了氮气、水蒸气和二氧化碳的惰化性能和惰化机理的区别。理论计算和实验表明：氮气体积分数在60％以下时,计算值和实验值吻合较好,在60％以上时氮气可以完全抑制氢氧混合气体爆炸;二氧化碳、水蒸气和氮气的惰化能力依次降低。     

爆炸荷载下沉箱重力式码头模型毁伤效应

在野外条件下开展了不同爆炸荷载条件下沉箱重力式码头模型毁伤效应实验,得到了沉箱重力式码头模型在1 kg TNT当量空中爆炸、水下爆炸以及结构内部爆炸后的毁伤模式,并针对不同毁伤模式给出了相应的抢修建议。实验结果表明:空中爆炸荷载下码头仅面板局部破坏形成爆坑;水下爆炸荷载下码头迎爆面及相近区域形成大量裂缝;结构内部爆炸荷载下码头仓格大变形破坏且中间面板被掀飞;从横向对比来看,在相同爆炸当量下空中爆炸荷载下码头毁伤程度最小,结构内部爆炸荷载下码头毁伤程度最大。     

管道内流动气体爆炸问题的实验研究

利用ＤＢＺ １ 型爆炸实验装置,通过测定３ｍ 爆炸噪声级,对管道内流动气体爆炸的若干问题进行了研究。这些问题主要包括:爆炸随可燃气体浓度变化的特征、流动阻碍作用和流量对爆炸性能的影响等。对有关结果进行了理论分析和讨论。     

爆炸荷载下钢筋混凝土梁的变形和破坏

利用爆炸压力模拟器进行钢筋混凝土简支梁爆炸冲击实验,详细介绍了实验设计,通过实验系统分析了钢筋混凝土(RC)梁变形破坏特征以及钢筋作用机理和对变形破坏的影响,并建立了RC梁的分离式有限元模型,利用LS-DYNA分析了实验过程,对计算结果与实验结果进行了比较,分析了误差产生的原因,得到了爆炸冲击荷载作用下RC梁的损伤破坏特征和机理,可为毁伤评估和结构抗爆设计提供参考。     

水下爆炸冲击荷载下混凝土重力坝的抗爆性能

在水下爆炸冲击荷载作用下,结构动力响应较之静态荷载和地震荷载作用下要复杂得多。通过大 量的数值模拟,探讨了混凝土重力坝在水下爆炸冲击荷载作用下,大坝高度、库前水位对大坝抗爆性能的影 响,为大坝抗爆性能评估和防护设计提供基础。数值计算中,构建了重力坝水下爆炸全耦合数值模型,并考虑 爆炸冲击作用下混凝土的高应变率效应。研究结果表明:对于混凝土重力坝,随着大坝高度的增加,大坝的抗 爆性能增强;库前水位对大坝的抗爆性能影响较大,通过降低库前水位可有效提高大坝的抗爆性能。     

防护模型在接触爆炸作用下的破坏

根据大型舰船的多层防护结构,制作了具有多层隔舱的模型,在外层板中心分别进行了3种药量的接触爆炸。通过分析破口的形状、破坏程度来研究舰船多层防护的作用。通过试验得出,多层防护的空舱对爆轰产物和爆炸冲击波具有良好的膨胀衰减作用,液舱则对粒子流、爆轰产物和冲击波的衰减作用明显。舰船的多层防护体系对减小爆炸冲击的损伤具有重要作用。     

近距离爆炸比例爆距的界定标准及荷载模型

如何准确界定“近距离爆炸（close-in explosion）”一直是防护工程研究领域的热点。本文中基于已被充分验证的精细化有限元模型,研究了TNT球形装药自由场爆炸冲击波传播与爆轰产物高速膨胀共同作用的特点和规律,发现在比例爆距小于0.80 m/kg1/3的范围内,爆轰产物对刚性壁面的爆炸荷载影响显著,提出球形装药近距离爆炸的比例爆距界定标准为0.30～0.80 m/kg1/3。研究发现,在近距离爆炸下,爆炸波在入射角为0°～5°范围内的刚性壁面反射荷载峰值会出现急剧下降的现象,这是由爆轰产物喷射的不均匀性和随机性导致的;近距离爆炸下,刚性壁面反射超压出现了两个峰值的现象,这是由冲击波和爆轰产物分别与刚性壁面相互作用导致的。提出了近距离爆炸情况下两个荷载峰值的计算公式,以及适合工程结构响应计算的简化荷载模型;揭示了近距离爆炸下刚性壁面反射超压的分布规律。     

An experimental investigation into the buckling of cylindrical shells of variable-wall thickness under radial external pressure

Cylindrical shells, with wall thickness-to-diameter ratios varying in steps from 1:2000 to 1:500 are used in large floating-roof storage tanks, where buckling under partial vacuum is a potential risk. To examine the validity of several methods of analysis, aluminum models with a nominal diameter of 150 mm were tested. Some models exhibited a sudden buckling, at the pressure predicted by one of the methods of analysis, others deformed at increased rate as the critical pressure was approached. A gradual change in, modal-buckling pattern, under decreasing pressure, was also observed.     

Performances of LES and RANS Models for Simulation of Complex Flows in a Coaxial Jet Mixer

Flow and mixing processes in a classical coaxial jet mixer have been investigated numerically. Calculations have been performed using three Large Eddy Simulation models and three unsteady RANS models. The time averaged mixture fraction and axial velocity, their rms values and energy spectra are compared with LIF and LDA measurements for both j- and r-modes of the jet mixer flow. A special attention is paid to the ability of different models to reproduce unsteady effects. The analysis demonstrates the superiority of the LES method with the dynamic mixed SGS model (DMM) with respect to other RANS and LES models.     

Simulation of the dynamic (frequency-dependent) permeability and electrical conductivity in porous materials based on the concept of an ensemble of pores

The class of models of porous media based on the concept of an ensemble of pores with a certain distribution of the main geometrical parameters (e.g., pore size) is studied. The case of the saturation of the pore space with a single-phase multicomponent fluid mixture is studied with and without taking into account the transfer of electric charges. Transfer laws are derived from the condition of decreasing free energy. The hydrodynamic connectivity of pores (and electrical conductivity) is described by two kernels: one kernel describes the connectivity of pores in space, and the other describes the connectivity of pores in the elementary macrovolume. The frequency dependences of the dynamic permeability determined in laboratory experiments and the electrical conductivity of the porous medium were determined using the concept of an ensemble of pores. The relationship between the models considered and relaxation filtration models is established.     

旋转功能梯度智能结构的刚-柔耦合动力学分析

基于一次耦合模型理论建立了中心刚体-压电层-功能梯度材料智能梁系统的刚柔耦合动力学模型．研究了开环状态下将压电材料作为传感器的压电效应和质量刚度效应对系统动力学特性的影响．通过仿真算例与另两种不同建模理论（传统零次近似耦合模型、一次近似耦合模型）作了对比．随着中心刚体外驱动力矩的增大,零次近似耦合模型和一次近似耦合模型计算结果逐渐发散,而本文的一次耦合模型的计算结果始终保持收敛,较其他近似耦合模型具有一定优势．对三种不同的结构的计算结果表明,压电材料的压电效应对系统的动力学特性影响显著,压电材料的质量刚度效应也会影响智能梁的动力学行为,前者比后者的影响大得多．此外,功能梯度材料功能梯度指数对系统动力学特性的影响也较大．     

Mechanically alloyed nanocrystalline iron and copper mixture: behavior and constitutive modeling over a wide range of strain rates

A comprehensive study on the response of a nanocrystalline iron and copper mixture (80% Fe and 20% Cu) to quasi-static and dynamic loading is performed. The constitutive model developed earlier by Khan, Huang & Liang (KHL) is extended to include the responses of nanocrystalline metallic materials. The strain rate and grain size dependent behaviors of porous nanocrystalline iron-copper mixture were determined experimentally for both static and dynamic loading. A viscoplastic model is formulated by associating the modified KHL model (representing the fully dense matrix behavior), and Gurson's plastic potential which provides the yield criteria for porous material. Simulations of uniaxial compressive deformations of iron-copper mixture with different initial porosity, grain size and at a wide range of strain rate (10⁻⁴ to 10³ s⁻¹) are made. The numerical results correlate well with the experimental observations.     

Two non-probabilistic set-theoretical models for dynamic response and buckling failure measures of bars with unknown-but-bounded initial imperfections

This paper is concerned with the problem of comparison of two non-probabilistic set-theoretical models for dynamic response and buckling failure measures of bars with unknown-but-bounded initial imperfections. Two kinds of non-probabilistic set-theoretical models are convex models and interval analysis models. In convex models and interval analysis models, the uncertain quantities are considered to be unknown except that they belong to given sets in an appropriate vector space. In this case, all information about the dynamic response and buckling failure measures of bars is provided by the set of dynamic responses and buckling failure measures consistent with the constraints on the uncertain quantities. The dynamic response estimate is actually a set in appropriate response space rather than a single vector. The set estimate is the smallest calculable set which contains the uncertain dynamic response, but it is usually impractical to calculate this set. Two set estimate methods are developed which can calculate the time varying box or hyperrectangle, i.e. interval vector in the response space that contains the true dynamic response. Comparison between convex models and interval analysis models in mathematical proofs and numerical calculations shows that, under the condition of the outer enclosed ellipsoid from a hyperrectangle or an interval vector, the set dynamic response predicted by interval analysis models is smaller than that yielded by convex models; under the condition of the outer enclosed hyperrectangle or an interval vector from an ellipsoid, the dynamic response set calculated by convex models is smaller than that obtained by interval analysis models.     

Turbulence Resolution Scale Dependence in Large-Eddy Simulations of a Jet Flame

The explicit dependence of LES fields on the turbulence resolution scale Δ implies that LES statistics usually vary with Δ and exhibit different convergence behaviors for different types of statistics, flow variables and subgrid LES models. The present work compares the performance of two popular subgrid models—the dynamic Smagorinsky model and the Vreman model—based on the convergence of their LES statistics with respect to Δ for a piloted methane-air (Sandia D) flame. The Δ-dependence of the LES statistics is studied based on five grids with progressively increased resolution ranging from 3 × 10⁵ to about 10.4 × 10⁶ cells. The simulation results show that the resolved velocity statistics converge for the finest grids with some weak Δ-dependence observed in the variance fields. The mixture fraction statistics are found to be more sensitive to the turbulence resolution scale upstream in the flame signifying the importance of the estimation of the Δ-invariant LES statistics at the DNS limit. For the considered flame the Vreman subgrid model exhibits good performance with the statistics being very close to those given by the dynamic Smagorinsky model, and being rather insensitive to a choice of the model constant.     

水平油水两相流流型对阻抗式含水率计的影响研究

实验研究了水平条件下20mm管径油水两相流的流动特性对阻抗式含水率计测量的影响.首先利用阻抗式含水率计测量不同含水率和流量条件下的混合物电阻率,并使用高速摄像记录对应的流型特征,进而分析流型对测量值的影响.通过对低、高流量分别采用电学和流体动力学模型分析后发现:低流量下混合物电阻率的主要影响因素是油水两相之间的速度滑脱,采用双流体动力学模型能有效地反映其变化规律.而高流量下(水包油分散流时)速度滑脱很小可以忽略,油水两相的空间结构对混合物电阻率的影响是问题的关键.近似绝缘的油滴分散在导电的水中形成的含孔导体电阻率高于实心导体,适用的电学模型是Maxwell电阻率模型.