污染扩散浓度场激光散斑测量原理研究

提出了一种利用激光散斑和散斑照相技术的污染扩散非定常瞬时全场浓度测量的新方法。根据污染烟雾粒子成像、粒子散射、统计光学以及数字图像处理技术,从理论上详细论证了浓度场全场测量的原理和此方法测量的局限性,为进一步设计浓度场测量系统提供了参考依据。     

污染扩散瞬态浓度场的非线性特征实验研究

为了探讨污染扩散瞬态浓度场是否具有非线性特征,利用基于数字图像处理技术和光学粒子散射理论的污染扩散瞬态浓度场光学测量系统,获得了污染扩散浓度场的二维时间和空间湍流信息,运用这些信息分析了分形和混沌等非线性特征,得出其嵌入维数为9,关联维数为3．218,Kolmogorov熵为0．138541,最大Lyapunov指数为0．63691。结果表明,污染扩散瞬态浓度场的瞬态浓度具有低维非线性特征,存在奇异吸引子,是混沌的。     

DM8148的射流扩散试验图像处理系统研究

将实时快速图像处理技术引入射流浓度场检测领域,结合自主研发的浓度场扩散试验装置,设计了一套以DM8148为图像处理核心,CCS5.5.0和Matlab为软件平台的射流浓度场检测系统.在实验水槽射流扩散实验中,CMOS相机采集示踪物质浓度扩散的一系列瞬时图像,并提取示踪物质扩散区域,通过图像处理算法使示踪剂的扩散图像以等浓度线图形式显示,实现流场浓度分布可视化.实验表明,本系统对污染物扩散规律研究及水环境质量评价均有借鉴意义,同时也表明本系统在水体污染物浓度场测量中具有一定的可行性.     

同轴数字全息用于粒径测量的影响因素分析

采用同轴数字全息技术测量研究粒子场,其高分辨力的再现像和粒径高精度测量受到诸多因素的影响.本文简要介绍了同轴数字全息的基本概念、原理、方法及其在粒子直径测量中的应用,主要通过计算机仿真研究了记录距离和粒子浓度这两个因素对粒径测量精度的影响,给出了记录距离的范围,同时提出了基于灰度梯度提取粒子边缘进行粒径测量的方法,并通过实验进行了验证.     

螺旋流抑制杆管偏磨的PIV实验研究

为了研究聚驱采出井偏心环空中流体流动状态与抽油杆所受法向力的关系,在模拟井筒中产生轴向流和螺旋流,利用粒子图像测速技术（PIV）,测量了不同质量浓度聚合物溶液,在偏心环空窄间隙、宽间隙中轴向流和螺旋流的速度瞬时特性,并将它们的轴向速度梯度进行了比较。利用设计的实验装置测量了介质为不同质量浓度聚合物溶液时,轴向流和螺旋流...     

复杂气候条件下LNG扩散特性的数值模拟

结合随机游走模型与拉格朗日粒子模型(LPDM),计算了湍流输送程度的表征量:平均水平输送速度,水平与垂向速度场以及水平与垂向的脉动速度.计算结果与风洞试验数据的对比显示:水平脉动速度小于实验值.近地层的垂向脉动速度计算值小于实测值,超过600 m高度后,垂向脉动速度计算值大于实测值.在速度场模拟的基础上,进一步计算了下风向的地面浓度、水平方向的羽流扩散宽度和垂直方向的羽流扩散宽度等扩散参数,并讨论了经验公式与模拟结果的差异.     

基于化学发光溶液示踪的射流浓度场测试分析系统

基于化学发光具有灵敏度高、不受外界光源干扰的优势,研究将化学发光溶液作为射流示踪剂的可行性,并开发了一套用于射流浓度场扩散规律研究的实验装置和测试分析系统。开展了化学发光体系的选择与优化、射流扩散实验装置的设计与开发（水槽实验装置、射流实验装置、图像采集与图像处理）、动水条件下射流浓度场扩散实验3方面的研究工作。构建的实验系统的特点在于以化学发光溶液作为射流浓度场的示踪剂,利用图像采集装置和图像处理程序来捕捉、分析射流浓度场时空动态变化的扩散过程。研究结果表明,过氧草酸酯类化学发光体系可以作为射流示踪剂来定量描述和分析射流浓度场的扩散特性,设计开发的实验装置和分析系统可以完成测定和分析动水条件下射流浓度场的任务。     

基于光流法的气流场测量研究

气流场的测量是许多研究领域的难点问题,其中的核心问题是示踪粒子的选取。该文从适应业务工程需求的角度出发,着眼于气流场测量的难点问题,基于光流法原理,采用蒲公英种子为示踪粒子,开展气流场测量的实验研究。实验研究中以小型风洞的气流场作为研究对象,利用高速摄像机连续拍摄粒子运动,再采用光流法计算粒子的轨迹、方向和速度,以此反映气流场的情况。结果表明:基于光流法并结合蒲公英种子作为示踪粒子的气流场测量方法是一种有效的新型测量方法,蒲公英种子的随流性较好,能够真实反映出气流场的特征,可进一步开发推广应用于各研究领域的气流场的测量。     

基于粒子系统的空气污染扩散模拟研究

通过基于粒子系统构建虚拟地理环境的方法进行了空气污染扩散的动态模拟研究.粒子系统将动态、模糊的污染物定义为微观粒子的集合,根据随机过程理论对污染气流扩散进行约束,从而实现在客观上对空气污染扩散的动态性和随机性的有效描述.该研究方法从粒子发射域、粒子运动、粒子绘制等关键环节,在满足视觉效果的前提下进行效率优化,并以珠江三角洲空气污染为案例,建立了虚拟地理环境原型系统,开展了空气污染动态扩散模拟,进行了实时交互查询与分析.实验结果证明,上述的方案能够达到模拟效果的逼真性和交互操作的实时性.     

激光衍射式粒度分布测试仪用于粒子浓度的测定

根据Fraunhofer理论研制的激光衍射式粒庆分布测试仪具有在一个较宽的粒度分布范围内进行实时测量的优点。但是，分散粒子的浓度在很多仪器上无法显示出来。本文根据固定检测器的测量电压与衍射光强度之间的关系特性，研究了一种测量不同形状粒子（如：球形、方形及拟柱体）的对数—正态分布来测量分散粒子浓度的方法。研究结果表明，根据测量的中位径和检测器测定的最高电压的关系，可提出一个粒子浓度的近似方程，这个方程适用于不同形状的粒子，如球形、方形、拟柱体。而且，这一技术可用于结晶器中晶体生长过程中粒子浓度的连续测定。…     

Moore响度在车内噪声分析中的应用

针对某客车变速器异响噪声的非稳态特性,在ANSI_S3.4 2005标准基础上建立了Moore瞬时响度模型,并引入目前主流声学软件采用的Zwicker响度模型进行对比验证,最后将瞬时响度模型应用于车内噪声信号的识别及其定量评价。结果表明：Moore响度模型计算精度及其瞬时特征响度谱能量分布的清晰度均比Zwicker模型的结果更高,采用Moore瞬时响度有助于非稳态过程中的噪声源识别及噪声机理分析,用Moore响度来定量评价噪声具有可行性。     

Large eddy simulation of a horizontal particle-laden turbulent planar jet

Numerical simulations of the particle-vortex interactions for an unforced, incompressible, spatially developing horizontal particle-laden turbulent planar jet are reported. Effects of the initial two-phase velocity slip on the instantaneous concentration distribution of particles with and without the influence of gravity are studied. Continuous phase simulation is performed by the method of large eddy simulation (LES) while the particle phase is solved by a Lagrangian method. Extensive results on the particle-laden jet flow are obtained. Simulation of the gas-phase reproduces the essential features of the coherent structures in the planar jet. Length of the potential core and essential features of the coherent structures in the planar jet are compared with experimental and other theoretical results. The simulation shows that initial two-phase velocity slip plays an important role in enforcing particle transverse dispersion in the jet region and sharply changes the instantaneous particle distribution. Furthermore, results demonstrate the influence of gravity on particle dispersion and sedimentation. Such pronounced effect of gravity on instantaneous concentration of particles with increased Stokes number and initial slip coefficients emphasize the need for the consideration of gravity for horizontal particle-laden jet. Received 6 September 2000     

Dispersion of contaminant in oscillatory flow through a pipe — Computation of moments

Summary Finite—difference implicit scheme is adopted to solve the Aris-moment equations of dispersion of solute in an oscillatory flow through a pipe for all time. Mean concentration distribution have been calculated from first four central moments by using Hermite polynomials and the deviations from Gaussianity have also been examined for unsteady flow.With 3 Figures     

Unsteady flow of a dusty fluid through a circular pipe with impulsive pressure gradient

Summary The unsteady flow of a dusty fluid through a circular pipe induced by a time dependent impulsive pressure gradient, has been studied. The governing equations have been solved using Laplace transform technique. Results have been discussed with the help of graphs. It is observed that the velocity of the fluid phase as well as that of the particle phase decreases with increase of either volume fraction or mass concentration of particle phase. The instantaneous rate of discharge of fluid as well as that of the particle phase decreases with increase of mass concentration of particles. They increase with time and attain a steady state for large time.     

突风作用下圆柱结构气动特性的试验研究

突风(平均风速随时间快速变化)作用在结构或构件上时,结构的气动力和振动状态与平稳风作用下的结果有何不同,是值得研究的问题。在风洞实验室,利用电压控制的方法,实现了具有一定风速加速度的突升和突降的风速变化过程,测试了圆柱结构在突变风速平稳风速作用下的气动力和振动状态,试验结果表明：当突升风速作用在模型上时,采用瞬时风速和气动力算得的力系数和在平稳风速下的结果一致;当突降风速作用在模型上时,采用瞬时风速和气动力算得的力系数虽然在大小上和在平稳风速下的结果一致,但是其对应的临界雷诺数范围比平稳风速对应的临界雷诺数范围,整体向小的方向上偏移了一定的量值。当不涉及到临界雷诺数时,本文的突变风速不会激发模型的大幅振动;当风速升至或降至临界雷诺数区域时,模型将发生稳定的大幅振动;当风速经过临界雷诺数时,在临界雷诺数对应的风速下发生大幅振动,随着风速的升高或降低使得对应的雷诺数离开临界区域时,振动逐渐消失     

Dispersion in a two-zone packed tube: An extended Taylor’s analysis

Taylor’s classical analysis for scalar dispersion in a single phase fluid flow is rigorously generalized for an instantaneous release of scalar substances into a fully developed flow through a long tube of two zones distinctively packed with porous media. A formulation for the dispersion is presented by cross-sectionally averaging the concentration transport equations and introducing a closure model for the concentration deviation terms produced in the averaging procedure. The velocity distribution of the flow through the tube is derived, with existing solution for a single zone tube flow included as a special case. Corresponding dispersivity is analytically determined, and Taylor’s well-known result for a single phase flow in a single-zone tube is recovered by setting corresponding parameters as unity. The effects of relevant parameters on both velocity profile and Taylor dispersivity are illustrated.     

Continuous-time state-space unsteady aerodynamic modeling based on boundary element method

In this paper a continuous-time state-space aerodynamic model is developed based on the boundary element method. Boundary integral equations governing the unsteady potential flow around lifting bodies are presented and modified for thin wing configurations. Next, the BEM discretized problem of unsteady flow around flat wing equivalent to the original geometry is recast into the standard form of a continuous-time state-space model considering some auxiliary assumptions. The system inputs are time derivative of the instantaneous effective angle of attack and thickness/camber correction terms while the outputs are unsteady aerodynamic coefficients. To validate the model, its predictions for aerodynamic coefficients variations due to the various unsteady motions about different wing geometries are compared to the results of the direct BEM computations and verified numerical and theoretical solutions. This comparison indicates a good agreement. Since the resulting aerodynamic model is in the continuous-time domain, it is particularly useful for optimization and nonlinear analysis purposes. Moreover, its state-space representation is the appropriate form for an aerodynamic model in design or control applications.     

Investigation of the propagation of pollutants in water reservoirs

A mathematical model for investigating the problem of the propagation of pollutants in water reservoirs on salvoed (instantaneous) discharge is suggested. To calculate dilution, a method developed on the basis of the equation of turbulent diffusion in cylindrical coordinates is suggested. The method allows one to determine the concentration of pollutants at an arbitrary distance from the place of their discharge. The conditions for the formation of local pollution zones in a water reservoir are considered.