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首页> 外文学位 >Flow visualization/digital image analysis of saltating particle motions in a wind-generated boundary-layer.
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Flow visualization/digital image analysis of saltating particle motions in a wind-generated boundary-layer.

机译：气流可视化/数字图像分析在风边界层中盐化颗粒的运动。

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摘要

A novel flow-visualization/digital-image-analysis technique to obtain quantitative information on individual mono-dispersed silica-sand particle motions in a wind-generated turbulent boundary-layer has been developed and implemented. The motions of mono-dispersed particles have been examined for three different sand-particle diameters (125 {dollar}mu{dollar}m, 195 {dollar}mu{dollar}m and 325 {dollar}mu{dollar}m) and various boundary-layer surface-shear velocities. The technique involves recording particle trajectories, which have been illuminated with a strobed plane of light generated via a He-Ne laser, on 35 mm black and white film with a 35 mm SLR camera, converting the negatives into 512 {dollar}times{dollar} 512 digital images, enhancing the images via Fast Fourier Transforms, extracting 'dashed' particle lines and then linking the lines together to reconstruct the particle trajectory. The result is a Lagrangian description of the particle path of flight, obtained with the aid of the basic principles of computer vision/artificial intelligence. The relevant wind-field data are obtained with the aid of cross-wire/hot-wire anemometry.; In many cases, the entire particle trajectory cannot be viewed because of particles moving into and out of the camera's depth and field of view. Accordingly, a two-dimensional Lagrangian model based on the particles' equations of motion is developed in order to estimate particle ejection and impact velocities and angles, and lengths and heights of trajectories from the measured image data and the measured wind field data. The RMS error associated with the calculated particle coordinates relative to the measured coordinates is approximately 20%.; The results indicate that the particle ejection velocity increases with particle diameter and is about 1.3 times greater than the surface-friction velocity. The vertical and horizontal ejection velocities decrease and increase respectively with increasing surface-friction velocity, resulting in a lower and shorter trajectory and a lowering of the ejection angle. As well, the impact angle increases with increasing diameter and the impact velocity is significantly smaller than the particle's terminal velocity.; The digital image analysis process and Lagrangian simulation were developed on the University of Toronto Mechanical Engineering Department's Sun 3-180 computer and subsequently implemented on the Cray X-MP/22 supercomputer of the Ontario Centre for Large Scale Computations. The result was a 20 to 30 fold increase in speed.
机译：已经开发并实现了一种新颖的流动可视化/数字图像分析技术，该技术可获取有关风产生的湍流边界层中单个单分散硅砂颗粒运动的定量信息。已经检查了三种不同的沙粒直径（125 {μm}μm{dollar} m，195 {dollar}μm{dollarm} m和325 {dollar}μm{dollar} m）的单分散颗粒的运动和各种边界层表面剪切速度。该技术涉及用35毫米SLR相机在35毫米黑白胶片上记录粒子轨迹，该轨迹已通过He-Ne激光产生的光的频闪平面照明，将负片转换为512 {美元}倍{dollar } 512个数字图像，通过快速傅立叶变换对图像进行增强，提取“虚线”粒子线，然后将这些线链接在一起以重建粒子轨迹。结果是借助计算机视觉/人工智能的基本原理获得的粒子飞行路径的拉格朗日描述。相关的风场数据是通过交叉线/热线风速仪获得的。在许多情况下，由于粒子进入和移出相机的深度和视野，因此无法看到整个粒子轨迹。因此，建立了基于粒子运动方程的二维拉格朗日模型，以便从测量的图像数据和测量的风场数据估计粒子的喷射以及撞击速度和角度以及轨迹的长度和高度。与计算的粒子坐标相关的RMS误差相对于测量的坐标约为20％。结果表明，粒子的喷射速度随粒径的增加而增加，约为表面摩擦速度的1.3倍。垂直和水平喷射速度随着表面摩擦速度的增加而分别减小和增加，从而导致轨迹的减小和缩短以及喷射角的减小。同样，撞击角随直径的增加而增加，并且撞击速度明显小于粒子的末端速度。数字图像分析过程和拉格朗日模拟是在多伦多大学机械工程系的Sun 3-180计算机上开发的，随后在安大略省大型计算中心的Cray X-MP / 22超级计算机上实现。结果是速度提高了20到30倍。

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  • 作者

    Ciccone, Anthony Donato.;

  • 作者单位

    University of Toronto (Canada).;

  • 授予单位 University of Toronto (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 1988
  • 页码
  • 总页数
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
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