助推器附近二维激波边界层干扰的数值分析

本文利用二维雷诺平均的Navier-Stokes方程，采用K-ε湍流模式，运用有限体积法，对大型运载火箭的助推器与芯级的激 波边界层干扰进行了二维数值模拟.数值结果表明在助推器激波的干扰下，芯级边界层流场明显出现了分离和再附过程。助推器头 部形状对流场有显著的影响，在半球助推器头形状情形下由于产生丁较强的弓形激波，边界层的分离和再附过程最显著，压力分布 最复杂。助推器与芯级距离对流场也有显著的影响，距离较小时，压力系数较大，激波边界层的强干扰会产生分离区甚至分离泡。     

助推器附近二维激波边界层干扰的数值分析

本文利用二维雷诺平均的Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程,采用κ－ε湍流模式,运用有限体积法,对大型运载火箭的助推器与芯级的激波边界层干扰进行了二维数值模拟．数值结果表明在助推器激波的干扰下,芯级边界层流场明显出现了分离和再附过程．助推器头部形状对流场有显著的影响,在半球助推器头形状情形下由于产生了较强的弓形激波,边界层的分离和再附过程最显著,压力分布最复杂．助推器与芯级距离对流场也有显著的影响,距离较小时,压力系数较大,激波边界层的强干扰会产生分离区甚至分离泡．     

既有多层砌体结构隔震加固数值模拟分析

以某4层砌体结构教学楼一层楼盖下部隔震加固工程实例为研究对象,使用SAP2000有限元软件建立该教学楼3种情况下的模型,即原有结构、1层楼盖下部隔震结构及基础隔震结构的模型,进行数值模拟,运用模态分析法和动力时程分析法对结构进行对比分析。结果表明,2种方式隔震加固后的砌体结构在地震动作用下抗震性能均明显改善,隔震装置布置合理,并且在实际应用中,结构基础不适合做基础隔震的情况下,将隔震装置布置在一层楼盖下部,同样会获得良好的隔震效果,且便于实施。     

数值模拟技术在建筑结构加固教学中的应用

在教学资源相对缺乏的情况下,为激发学生的学习热情,帮助学生理解基本概念,把数值模拟技术引入到建筑结构加固的授课过程中,形象逼真的模拟建筑构件加固前后的破坏过程。     

基于振型数据的塔架结构损伤数值模拟分析

近年来对结构的损伤分析方法甚多,本文利用ANSYS有限元软件对塔架结构的损伤进行数值模拟分析,基于结构损伤前后的振型数据,实现了对一平面塔架结构的较精确的损伤状态评估。数值模拟结果表明对塔架结构的损伤评估具有一定现实意义。     

数值模拟在《工程结构抗震》课程教学中的应用

《工程结构抗震》课程涵盖大量抽象概念和结构动力学方面的知识,给学生的学习增加了难度.为了帮助学生更好的理解工程抗震原理及结构的抗震设计方法,本文借助大型通用有限元分析软件ANSYS将数值模拟引入工程结构抗震课程教学中,在讲解振型分解反应谱法、时程分析法、"强柱弱梁"等理论时,让学生直观认识到地震作用下构件和结构的受力特点和破坏形态,有助于启发学生的主动思维、提高课堂教学质量.     

鲨鱼皮盾鳞结构减阻性能数值模拟

海洋中快速游动的鲨鱼因其皮肤表面具有减少摩擦阻力的肋条状盾鳞结构,从而受到研究学者的广泛关注。为了指导减阻表面的设计与制造,选用数值模拟的方法对鲨鱼皮盾鳞结构的减阻机理进行了研究。通过扫描电子显微镜(scanning electron microscope,SEM)观察,获取鲨鱼盾鳞的微观结构,构建出简化的几何模型单元,并设计了不同分布规则和排布的单元阵列,形成了大面积非光滑仿生结构表面。利用Fluent软件对建立的计算域模型进行流体动力学仿真,同时与传统的矩形沟槽非光滑表面进行比较。数值模拟结果表明:仿生非光滑表面均减少了摩擦阻力,并且相较于矩形沟槽非光滑表面,简化盾鳞结构表面的减阻率明显增加;当入口速度为5 m/s时,对齐排布的简化盾鳞结构表面的减阻率可达到17.86%。最后,从壁面附近区域的流体流速和湍流动能2个方面对非光滑表面的减阻机理进行了分析。研究结果可望对设计和制备具有减阻功能的海洋装备仿生表面起到指导作用。     

用Matlab数值模拟非线性电路混沌实验

该文简单介绍了非线性电路混沌实验的实验原理，并用Matlab软件对非线性电路混沌实验进行了数值模拟，指出了数值模拟的重要意义。     

圆柱周围湍流场的数值模拟

In practical problems, the variation of the free surface around a circular pier is severe. For the Fluent CFD, the multiphase flow models cannot be used together with the LES model to calculate the free surface. Present paper provides a two-step method which joints the 2D compressible ideal-gas equations and the LES model to calculate the 3D flow field with free surface around the pier. The effects of the free surface on the flow structures are studied in detail.     

“油藏数值模拟”课程教学探讨

＂油藏数值模拟＂是一门综合性很强的课程。本文从＂油藏数值模拟＂课程的结构设置特点和该课程在现场应用的实际特点分析入手,提出了有助于改变该课程目前现状的教学方法和思路。     

Study of interaction between shock wave and unsteady boundary layer

ＩＮＴＲＯＤＵＣＴＩＯＮＳｈｏｃｋｗａｖｅｒｅｆｌｅｃｔｉｏｎｆｒｏｍａｗａｌｌｓｕｒｆａｃｅ,ｄｉｆｆｒａｃｔｉｏｎａｌｏｎｇａｃｕｒｖｅｄｓｕｒｆａｃｅ ,ｐｒｏｐａｇａｔｉｏｎｔｈｒｏｕｇｈａｃｈａｎｎｅｌｏｒａｔｕｂｅｗｉｔｈｖａｒｙｉｎｇｃｒｏｓｓ     

Study of interaction between shock wave and unsteady boundary layer

This paper reports theoretical and experimental study of a new type of interaction of a moving shock wave with an unsteady boundary layer. This type of shock wave-boundary layer interaction describes a moving shock wave interaction with an unsteady boundary layer induced by another shock wave and a rarefaction wave. So it is different from the interaction of a stationary shock wave with steady boundary layer, also different from the interaction of a reflected moving shock wave at the end of a shock tube with unsteady boundary layer induced by an incident shock. Geometrical shock dynamics is used for the theoretical analysis of the shock wave-unsteady boundary layer interaction, and a double-driver shock tube with a rarefaction wave bursting diaphragm is used for the experimental investigation in this work. Projects (No. X61151) supported by Centre for Engineering Research at Zhejiang University of Technology, China     

Numerical simulation of water mitigation effects on shock wave with SPH method

The water mitigation effect on the propagation of shock wave was investigated numerically. The traditional smoothed particle hydrodynamics (SPH) method was modified based on Riemann solution. The comparison of numerical results with the analytical solution indicated that the modified SPH method has more advantages than the traditional SPH method. Using the modified SPH algorithm, a series of one-dimensional planar wave propagation problems were investigated, focusing on the influence of the air-gap between the high-pressure air and water and the thickness of water. The numerical results showed that water mitigation effect is significant. Up to 60% shock wave pressure reduction could be achieved with the existence of water, and the shape of shock wave was also changed greatly. It is seemly that the small air-gap between the high-pressure air and water has more influence on water mitigation effect.     

冲击氧化铝单晶中失效波弛豫时间因子的测量

在冲击动压为133GPa的氧化铝单晶的冲击实验中,测量了在850nm处冲击氧化铝单晶的辐射曲线,发光信号显示被冲击压缩的单晶中存在延迟发射现象;该现象表明氧化铝单晶在冲击波到达后经历了一个再压缩过程,该过程可用失效波解释;通过实验曲线拟合到在133GPa下失效波的弛豫时间为0．107ms／cm．     

Simulation of Airblast Load and Its Effect on RC Structures

In the analysis of a structure subjected to an explosion event, the determination of the blast load constitutes a crucial step. The effect of the blast load on the structure depends not only on the peak shock overpressure, but also the impulse (hence the duration). For structures with a regular geometry, the blast load may be fairly well estimated using appropriate empirical formulae; however, for more complex situations, a direct simulation using appropriate computational techniques is necessary. This paper presents a numerical simulation study on the prediction of the blast load in free air using a hydrocode, with focus on the sensitivity of the simulated blast load to the mesh grid size. The simulation results are compared with empirical predictions. It is found that the simulated blast load is sensitive to the mesh size, especially in the close-in range, and with a practically affordable mesh grid density, the blast load tends to be systematically underestimated. The study is extended to internal blast cases. An example concrete slab under internal explosion is analyzed using a coupled analysis scheme. The internal blast load from the simulation is examined and the response of the RC slab is commented.     

冲击过程中能量匹配分析

简论了冲击过程中采用应力波方法分析能量匹配问题 ,得出 :冲击机械中入射应力波如满足理想波形时 ,从冲击对象反射回来的反射应力波能量达最小 ,冲击机械的能效达到最大值     

挡墙对爆炸形成的空气冲击波防护效应的三维数值模拟研究

本文对爆轰产物采用JWL状态方程，通过多流体网Euler型算法，应用自行编制MMIC3D程序，模拟了在爆点附近有无障碍物的三雏爆炸场的初始发展的情况，以及不同形状的防护挡墙对爆炸效应的影响，计算结果基本符合物理规律，这说明本文采用的模型及算法是合理的，并可用来进一步模拟爆炸对远场的作用效应，得到了对实际具有参考价值的计算结果。     

Mesh size effect in numerical simulation of blast wave propagation and interaction with structures

Numerical method is popular in analysing the blast wave propagation and interaction with structures.However,because of the extremely short duration of blast wave and energy trans-mission between different grids,the numerical results are sensitive to the finite element mesh size.Previous numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case,even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accu-rate numerical results.Therefore,both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with structures.Based on the numerical results and their comparison with field test re-sults and the design charts in TM5-1300,a numerical modification method was proposed to correct the influence of the mesh size on the simulated results.It can be easily used to improve the accu-racy of the numerical results of blast wave propagation and blast loads on structures.     

Study on pile drivability with one dimensional wave propagation theory

INTRODUCTIONInterestinonedimensionalwavepropagationtheoryforapplicationtounderstandingpiledriv ingismorethanacenturyold .ImportantworkdirectlyrelatedtocurrentapplicationstopiledrivabilitystartedshortlyaftertheSecondWorldWarandcontinuedtothepresent,assuchp…     

A study on dynamic response of slopes under wave action using simulation tests

1. Introduction At present, the construction of large-scale reservoirworks has given rise to many large-scale reservoirareas, the stabilization of slopes in these reservoirdistricts will be influenced by water waves. Thecirculating hydraulic loading caused by the waveproduces a great force on the slope, and especiallyforms a vibration wave force on the boundary of water surface and the slope earth, and even breaks the water-soil interface, leading to the excess pore pressurechanging along diff…