这项工作是由机械科学与工程学院，伊利诺伊大学厄巴纳 - 香槟分校，部作为莱昂纳多P.查莫洛的开办包的一部分支持。

1.实验室安全<ol><li>查看所选照明光源的安全指导方针（ 如激光，LED产业，卤素）。 注意：在这个实验中，一组五个250瓦卤素聚光灯被用作照明。该光源的基本安全性和推荐方面描述如下。 <ol><li>避免与卤灯，它在高温下（〜3000色温）下操作的直接接触。 </li><li>采集数据时，为了避免加热的条件下考虑流动保持光ON而已。 </li><li>远离可燃所有材料靠近光源，包括任何种类的纸张。 </li></ol></li></ol> 2.实验装置<ol><li>选择合适的镜头<ol><li>选择低像差镜头，以避免校准问题。推荐镜头类型长焦或微透镜。 </li><li>确保镜头涵盖的obj中所需的字段的视图（FOV）等的距离，O，通过估计所需的放大倍率， 男 。 注意：倍率是相机芯片到FOV的长度的比例，和对象距离可以计算为O = F（1 / M + 1），其中f是透镜的焦距。在该实验中，摄像头芯片的长度为20.34毫米和相应的视场，或主镜，为50毫米的有限物距ø≤250毫米。 （物距被抑制由于在摄像机和视图分离器被安装在滑动件的有限长度。）的倍率为M = 20.34 / 50 = 0.41，和与对象的距离的给定范围近似焦距为f ≤72.7毫米。因此，微透镜具有60mm的焦距用于以f / 2.8D的焦率。 </li></ol></li><li>安装和调整与分流查看相机。 <ol><li>通过滑动MIR水平的审讯卷的主镜的中心沿着垂直安装后ROR和修正柱支架镜像。注意，此步骤是在安装次级镜之前进行。 </li><li>安装摄像机，并设置图像重合的中心与主镜的中心。 </li><li>调整摄像机视图的宽度和高度刚好盖住通过控制感兴趣区域（ROI）的区域主镜的录音软件设置。这个过程是为了减少图像尺寸和图像噪声。注意：在这个实验中，主反射镜的尺寸为5×5厘米2（1728点¯x1728像素）。 </li><li>设计一个（可定制）3D校准目标。它应包围整个调查音量。确保分路器的每个视图捕获所有目标标记，以便统一校准。 注：在本演示中，目标是3D印刷用Vero细胞回塑料。它有一个台阶状与尺寸35×35×30mm的3，用直径1毫米的白色目标点分隔符编2,5 mm开始，在5mm和10mm的垂直，流向和翼展方向。目标的精确几何形状是关键的，因为它伸入一个校准模型和摄像机位置相对于所述水槽。 </li></ol></li><li>将校准目标进审讯音量。 <ol><li>对相机面临的一个可调节高度的平台上标定目标位置。 </li><li>通过调整目标平台的高度相匹配与询问体积的中心校准目标的中心的高度。 注意：在本实施例中，校准目标的中心标记与射流喷嘴的中心20厘米的高度调平。气泡水平仪可以用于水平目标。 </li></ol></li><li>安装和调整四视图分路器的次镜。 <ol><li>找到从确保充分捕捉审讯的距离主镜。这为0.2μm此演示（FIGURË1）。 </li><li>在它的大致位置时，在来自主镜的各侧摄像机视图大致与副镜对准贴装副镜。通过将其固定到辅助镜的垂直安装柱固定副镜。 </li><li>重复此过程，对于其他三面镜子。检查所有次级镜的几何对称性相对于所述主​​镜。 </li><li>使通过调整次级反射镜的反射镜安装，以确保每个的四个视图包围整个校准目标最终的调整。检查镜&#39;的位置和角度的一个有效的方法是使用激光指示器来可视化各视图的图像的路径。 </li><li>检查用于通过移动一个反射镜子图像的重叠。 注意：如果只有一个视图改变，那么重叠区域可以忽略不计。否则，重复步骤2.4.2至2.4.5，直到重叠区域最小化。 </li></ol></li><li>将光源（S）直接面对审讯音量。确保将相机调光，以避免相机传感器损坏时覆盖。 <ol><li>检查光源是在整个调查体积均匀分布的。 </li><li>增强的光强度，如果需要的话，由下光源直接放置一个放大镜。注意：在这个实验中，使用焦距f 0 = 450nm 10mm的平凸放大镜加紧的照明。 </li></ol></li></ol> 3.建立优化<ol><li>打开并调整相机设置以提高图像质量。 <ol><li>调整镜头倍率，直到通过主镜的反射聚焦同样在所有四个视图次要镜子。 </li><li>检查从视图分离器的图像是对称的，并且通过从四个视图观察校准目标图像的对称性捕获询问体积。 </li><li>调整f数来捕获从摄像机最接近的和最远的校准目标点。 注意：这使得相机捕捉示踪粒子只有在审讯量的深度。在这个例子中，F数是11。 </li><li>设置所需的帧速率550赫兹（这取决于具体的应用，见简介）和录音软件相应最大限度的光敏感度。 </li></ol></li><li>通过一个直播相机视图观察分离器的每个视图的颗粒密度差检查主镜的每个视图照明。 注意：如果多个光源用来照亮所述询问体积，它是可能具有在分离器的每个视图的差异。在该实验中，顶部的两个次级镜，因为照明来自顶部接收较少的光。在水槽底部的使用平面镜可以帮助减少光变跨越的意见。 </li><li>采用3D-PTV光源前，请关闭房间内的灯光背景。 </li><li>调整相机的G＆B的水平，以更好地捕获粒子光散射。记录与各种G＆B水平几个短序列，发现通过观察粒子轨迹的分布和密度的最优的一个。 注意：在这个实验中，G＆B水平的范围是0-500，和黑色（B）的电平设定为500，以亮调光器的光散射，而，增益（G）设定介质，300，以适度放大图像信号和避免过度使图像变亮。 </li></ol> 4.校准<ol><li>放置在侦查卷中的校准目标添加示踪粒子之前，采取一些校正图像。使用调光器光源（ 如 LED闪光灯光）照射目标。 </li><li>除以校准图像分成四个独立的子图像，使一个文本文件包含指ENCE协调目标标记的位置。 OpenPTV软件（http://www.openptv.net）在这里被用于此目的。 注意：以后的处理等同于采用多个摄像机设置的用户。 </li><li>点击“创建校准”选项卡中保存图像，并在步骤4.2在软件的“CAL”文件夹中获得的文本文件后启动校准过程。 </li><li>点击“修改校准参数”选项卡，然后选择“校准定向参数”选项卡，每个拆分视图中心和校准目标的原点之间定义放大，旋转角度和距离。 注意：第一个行是从原点校准目标在X，Y，Z方向上的相机传感器的距离。第二行表示角度，单位为弧度，绕x，Y，Z轴。接着，一个3×3的数据表示旋转矩阵。然后，两个下列各行是x的针孔距离和<em&gt; y坐标从图像中心（毫米），焦距轴。最后一行包含水槽玻璃在相对 ​​于原点的目标在X，Y，Z方向上的位置。 </li><li>点击“检测”和“显示初始猜测”调查的“猜测”点与检测到的目标点相匹配。 </li><li>所有四个视图，直到&#39;猜&#39;点重复步骤4.4与所设定的校正图像的对齐。 </li><li>点击“取向”重构询问体积的方向。 注意：校准可以通过调整透镜畸变和仿射变换得到改善。现在，调查体积校准并准备处理数据。见笔者的附加 ​​说明论文36校准过程。 </li></ol> 5.流量设置/数据采集<ol><li>来自帧速率的估计在每个摄像机视图捕获颗粒的最大数量二维最大流速。在这个演示中，给定速度为U≈0.4米/秒，帧速率为550赫兹和4〜×4×4 立方厘米体积审讯。这导致〜每帧1000个粒子。 </li><li>打开相机，在步骤3中得到的最优化设置。 </li><li>添加播种颗粒和等待数平均停留时间，从而使流动达到稳定状态。如果需要加入更多的粒子，但避免高接种密度，在步骤5.1，这可能会导致模糊度估计。 注意：在该实例中，〜1.6克为1.1g / cm 3的密度为100微米银包覆空心陶瓷球体被用作种子用于流体介质（2×0.4×0.4米3）。 </li><li>记录流图像的期望数目。 注意：在这个实验中，在550赫兹9000图像用记录软件被抓获。如果相机和/或视图分路器移动（即使是轻微的运动可以严重影响结果）重复步骤2.4至5.3。 </li></ol> 6.数据处理（通过OpenPTV软件） <ol><li>除以在步骤5.4获得分成四个独立的子图像的原始图像。 </li><li>点击“开始”选项卡下的“初始化/重新启动”，从四个视图加载初始图像。 </li><li>右键单击“运行”目录，然后单击“主参数的摄像头，折射率，粒子识别，图像序列，观察量和标准对应的个数来控制数量。 <ol><li>定义的用于“常规”选项卡下的实验相机（意见）的数量。在这个实验中，设置的摄像机的数量为4。 </li><li>定义沿着“折射率”选项卡下的摄影机视图折射率。 </li><li>定义最小和像素检测以及灰度值的阈值MAX数量，优化了“粒子识别”选项卡下的粒子检测的所有四个视图数。德像素的最小和最大号tection和灰度阈值确定用于颗粒探测像素大小和亮度级别。它消除了噪音和颗粒失焦。 </li><li>定义&#39;的序列处理参数“下图像处理的数量。 </li><li>定义“观察音量”选项卡下的观察量。 </li><li>定义下的“标准对应”，包括立体匹配总频带参数（毫米）对应的相关性。 </li></ol></li><li>点击“预处理”标签下的“高通滤波器”。这加剧在所有四个观点粒子光散射。 </li><li>点击“粒子探测”，以确定检测到的颗粒在所有四个视图亚像素级的重心。重复步骤6.2和6.3，直到类似于在步骤5.1计算颗粒的预期数检测颗粒的数量。 </li><li>点击“对应关系”，建立立体correspondenCES在每个视图。 注意：要重建检测到粒子的三维位置，对应至少应该从三个意见确定。 </li><li>点击“3D位置”来获得基于所述校准检测粒子三维位置。 </li><li>点击“不带显示屏的序列&#39;重复步骤，从6.4到6.7的所有图像序列的过程。 注意：这将创建包含检测粒子与制表符分隔文本文件格式框架总结每个图像设定&#39;rt_is&#39;文件。 </li><li>右键单击“运行”目录，然后单击“跟踪参数”来定义半径球体，（ 如 dvxmin和dvymin毫米/帧）的参数，以搜索候选粒子进行跟踪。 </li><li>点击“跟踪不显示&#39;来定义步骤6.7获得重建的颗粒的标识（ID）。 注意：用于使用一个四帧predic跟踪相关的相邻帧的序列器预测-校正方案24。这个过程创造了包含在帧中检测到粒子的跟踪信息的每个图像集ptv_is文件;前两列分别示出了粒子的ID中的前一帧和下一帧。 </li><li>点击“显示轨迹”可视化轨迹中的每个摄影机视图。 </li></ol> 7.后处理（祈愿） 注：范围和后处理的类​​型取决于个人的需求和它，因此，可定制。这里，指向基底计算简单说明作为例子。 <ol><li>获得拉格朗日帧数据（通过Matlab的）。 <ol><li>提取每个粒子及其相关的ID从ptv_is文件的三维位置。它允许连接的图像序列中检测粒子重建轨迹。 </li><li>计算从给定帧速率的每个轨迹的速度和颗粒的加速度。在此示范，粒子的速度和加速度由低通用移动三次样条34,37滤波该位置信号来计算。 </li><li>使含三维位置，三维速度，加速度3D和时间戳以及每个轨迹的轨迹ID字段的结构阵列格式。在该数据格式中， 结构体数组的长度代表轨迹号。 </li></ol></li><li>获得欧拉帧数据（通过Matlab的）。 <ol><li>结构体阵列（步骤7.1.3）转换到使用每个颗粒的时间戳的时间之一。这将在步骤7.1.3得到同样的结构排列的结构，但结构体数组的长度现在代表帧号，这是在这个实验9000元。 </li><li>内插的时间结构数组为每个时间段三维网格，以获得欧拉坐标瞬时速度场。在这个演示中，有趣的GridDataction在Matlab用于执行内插。 </li></ol></li></ol>

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G., Gruen, D., Papantoniou, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+tracking+velocimetry+in+three-dimensional+flows.">Particle tracking velocimetry in three-dimensional flows.</a> Exp Fluids. 15, 133-146 (1993).</li><li>Kasagi, N., Matsunaga, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+particle+tracking+velocimetry+measurement+of+turbulence+statistics+and+energy+budget+in+a+backward-facing+step+flow.">Three-dimensional particle tracking velocimetry measurement of turbulence statistics and energy budget in a backward-facing step flow.</a> Int J Heat Fluid Fl. 16, 477-485 (1995).</li><li>Virant, M., Dracos, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+PTV+and+its+application+on+Lagrangian+motion.">3D PTV and its application on Lagrangian motion.</a> Meas Sci Technol. 8, 1539 (1997).</li><li>Willneff, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> A spatio-temporal matching algorithm for 3 D particle tracking velocimetry. , (2003).</li><li>Rosi, G. A., Sherry, M., Kinzel, M., Rival, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterizing+the+lower+log+region+of+the+atmospheric+surface+layer+via+large-scale+particle+tracking+velocimetry.">Characterizing the lower log region of the atmospheric surface layer via large-scale particle tracking velocimetry.</a> Exp Fluid. 55, 1-10 (2014).</li><li>Fu, S., Biwole, P. H., Mathis, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+Tracking+Velocimetry+for+indoor+airflow+field:+A+review.">Particle Tracking Velocimetry for indoor airflow field: A review.</a> Build Environ. 87, 34-44 (2015).</li><li>Kolaas, J., Jensen, A., Mielnik, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+and+measurements+of+flows+in+micro+silicon+Y-channels.">Visualization and measurements of flows in micro silicon Y-channels.</a> Eur Phys J E. 36, 1-11 (2013).</li><li>G&#252;lan, U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+study+of+aortic+flow+in+the+ascending+aortavia+Particle+Tracking+Velocimetry.">Experimental study of aortic flow in the ascending aortavia Particle Tracking Velocimetry.</a> Exp Fluids. 53, 1469-1485 (2012).</li><li>Mei, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Velocity+fidelity+of+flow+tracer+particles.">Velocity fidelity of flow tracer particles.</a> Exp Fluids. 22, 1-13 (1996).</li><li>Tropea, C., Yarin, A. L., Foss, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Springer handbook of experimental fluid mechanics. 1, (2007).</li><li>Melling, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracer+particles+and+seeding+for+particle+image+velocimetry.">Tracer particles and seeding for particle image velocimetry.</a> Meas Sci Technol. 8, 1406 (1997).</li><li>Hering, F., Leue, C., Wierzimok, D., J&#228;hne, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+tracking+velocimetry+beneath+water+waves.+Part+I:+visualization+and+tracking+algorithms.">Particle tracking velocimetry beneath water waves. Part I: visualization and tracking algorithms.</a> Exp Fluids. 23, 472-482 (1997).</li><li>Biferale, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lagrangian+structure+functions+in+turbulence:+A+quantitative+comparison+between+experiment+and+direct+numerical+simulation.">Lagrangian structure functions in turbulence: A quantitative comparison between experiment and direct numerical simulation.</a> Phys Fluids. 20, 065103 (2008).</li><li>L&#252;thi, B., Tsinober, A., Kinzelbach, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lagrangian+measurement+of+vorticity+dynamics+in+turbulent+flow.">Lagrangian measurement of vorticity dynamics in turbulent flow.</a> J Fluid mech. 528, 87-118 (2005).</li><li>Hoyer, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3d+scanning+particle+tracking+velocimetry.">3d scanning particle tracking velocimetry.</a> Exp Fluids. 39, 923-934 (2005).</li><li>Kim, J. -. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Three-dimensional particle tracking velocimetry for turbulence applications. , (2015).</li><li>L&#252;thi, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Some+aspects+of+strain,+vorticity+and+material+element+dynamics+as+measured+with+3D+particle+tracking+velocimetry+in+a+turbulent+flow.">Some aspects of strain, vorticity and material element dynamics as measured with 3D particle tracking velocimetry in a turbulent flow.</a> ETH Z&#252;rich. , (2002).</li><li>Pope, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Turbulent flows. , (2000).</li></ol>

作者宣称，他们没有竞争的经济利益。

<html> 3D-PTV具有很大的潜力，以解开各种湍流，如在低层大气中25，室内空气分布26，或脉动流的大规模动荡运动的复杂的物理主动脉拓扑28在许多其他之中。但是，它的优点和局限性，以及经验的理解是必不可少最大限度地发挥其潜力。试错的初步测试和优化设置，包括帧速率，照明光源，G＆B级和图像滤波方法详尽的迭代，直接与重建一套（ 例如示踪）粒子的拉格...

湍流喷流是在工程应用中普遍存在。这种流动的详细描述是在从大型环保排放系统涵盖电子微尺度器件的实际问题广泛至关重要。由于其对一些广阔的应用前景影响，喷气流量已经深入研究了1 - 4。几个实验技术，包括热线测速仪4 - 8，激光多普勒测速仪（LDV）4，9 - 12，和粒子图像测速（PIV）12 - 16，都被用来描述飞机在大范围的雷诺数和边界流向条件。近日，采用3D-PTV研究湍流/非湍流界面的喷气流17，18已做了一些研究。 3D-PTV是特别合适的描述复杂湍流音响的技术从不同的角度的视场。它允许粒子轨迹在使用多视点立体参考拉格朗日框架体积内重建。该技术最早是由19张和介绍了由RACCA和杜威20进一步发展。此后，许多方面做了改进的3D-PTV算法和实验设置21 - 24。与这些成绩和以往的作品，该系统已被成功地用于研究各种流体的现象，如在4米x 2米×2米25，室内气流场26的一个结构域的大型流体运动，脉动流27和主动脉血流28 。 一个三维PTV测量的工作原理包括数据采集系统设置，记录/前处理，校准，3D的对应，时间跟踪和后处理。精确的校准允许的粒子位置的精确检测秒。在三个以上的图像视图检测到的粒子的对应允许基于对极几何形状的三维粒子位置的重建。从连续的图像帧的连锁导致定义粒子轨迹S（t）的一个时间跟踪。所述3D-PTV系统的优化是必需最大化多粒子可追溯性的可能性。 优化的第一步是获取合适的数据采集系统，包括高速摄像机，照明光源和播种颗粒的功能。与询问体积的大小沿所述照相机分辨率定义像素尺寸，因此，所需要的籽晶颗粒大小，这应该是比单一像素大。检测的颗粒的质心通过取由亮度21加权粒子像素的平均位置具有子像素精度估计。摄像机的帧率是密切associat编与雷诺数和检测到的颗粒链接的能力。较高的帧速率可以用于解决更快流量或粒子的数量较多，因为当图像之间的平均位移超过所述颗粒的平均分离的跟踪变得更加困难。 快门速度，光圈和灵敏度有三个因素在图像采集来考虑。快门速度应该足够快，以最小化颗粒，从而降低颗粒质心位置的不确定性围绕模糊。相机光圈应调整到询问体积的景深，以减少的容积之外探测粒子的概率。由于摄像机的最大感光度是固定的，作为帧速率的增加，所需要的必要的光以照亮颗粒应相应增加。不像PIV，复合光学设置以及高功率激光器没有严格要求在3D-PTV，只要光源足够粪便从示踪粒子到相机羊羔。连续LED或卤素灯属于跳过同步21，需要良好的成本效益的方案。 在3D-PTV，像其他光流的测量技术，示踪粒子速度被假设为在本地瞬时流体速度29。然而，这仅仅是对空的直径和惯性的理想示踪剂的情况下示踪颗粒应足够大，以由照相机捕获。有限微粒的保真度可以通过斯托克斯数式 T来确定， 即颗粒的弛豫时间尺度的比率和感兴趣紊流结构的时间尺度。一般来说，S T应当比1小很多对于式 T≤0.1流跟踪误差在1％以下30。在深入讨论可以在梅等人发现29 - 31 </sup&gt;。推荐的粒径为3D-PTV实验取决于光源和摄像机的灵敏度而变化。卤素或LED灯作为照明源，相对较大的颗粒被使用（ 例如 50-200微米）32，而较小的颗粒（ 例如 ，1-50微米）33，34可以用高功率激光可使用（ 例如 80-100瓦CW激光）。具有高反射率对于一个给定波长的光粒子，就像在卤素灯银涂层，可以放大自己的印记成图像。接种密度为成功的3D-PTV测量的另一个重要参数。少数颗粒导致低轨迹数，而颗粒的数量过多会导致在建立对应和跟踪歧义。在建立对应歧义包括重叠粒子和检测沿定义极线多名候选人。在跟踪的过程中，模糊性由于高seedin<html>是因为颗粒的相对短平均间隔的发生g密度。 第二步骤是在记录/预处理最佳设置，以提高图像质量。照相的设置，如增益和黑电平（G B）的，在优化图像质量方面发挥了重要的作用。黑电平限定在图像的最暗部分的亮度水平，而增益放大的图像的亮度。对G＆B水平的轻微变化可以显著影响可追溯性的可能性。事实上，高G＆B可能过亮的图像，并最终损坏相机传感器。为了说明这一点，在流程再造G＆B水平的影响也研究过这个文章。在预处理步骤中，图像被过滤，用一个高通滤波器，以从颗粒强调光散射。像素大小和灰度调整以最大化询问体积内的颗粒探测。 t“的&gt;优化的第三步是在立体成像，这是基于对极几何，照相机参数（焦距，主点，并且失真系数），以及折射率的变化的精确校准。此过程是必不可少的，以尽量减少在3D基准目标点的重构误差。极几何使用相对距离和倾斜角度（摄像机和询问体积之间）从目标图像。沿着通过询问体积相机视图折射率变化可以基于质谱的方法来考虑等 21上 。在该实验中，以规则分布的目标点的三维阶梯状结构被用作靶。 在3D-PTV实验中，虽然只需要两个图像，以确定一个三维粒子位置，典型地更多的摄像机被用来减少模糊度21。昂贵的设置有多个高速摄像机另一种是viEW分离器，由Hoyer 等人提出的。35，用于使用3D-PTV的和由Gulean 等人 28的生物医学应用最近应用。该视图分路器由一个金字塔形的镜子（关于此主镜）和四个调节后视镜（关于此副镜）组成。在这项工作中，一个四视图分离器和一个摄像机被用来从四个摄像机模仿立体成像。该系统是用于表征一个管喷射的中间流场与直径d H = 1cm到重新 ≈7,000拉格朗日和欧拉在约14.5-18.5直径下游射流原点帧。

<table border="0" cellpadding="0" cellspacing="0" width="749">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">ImageOps</td>
			<td style="width:119px;">CAMMC4082</td>
			<td style="width:407px;">High-speed camera</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">ImageOps</td>
			<td style="width:119px;">FBD-4XCXP6</td>
			<td>Frame Grabber</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:223px;">Potters Industries LLC</td>
			<td style="width:119px;">AG-SL150-30-TRD</td>
			<td>Seeding Paritcles</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:223px;">Upstate Technical Equipment CO.,INC</td>
			<td style="width:119px;">MISNOR-STP-6-S-CL</td>
			<td>Camera appliation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Photrack AG</td>
			<td style="width:119px;"></td>
			<td>Customized part and necessary if performing 3D-PTV with one camera</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">General Electrics&#160;</td>
			<td style="width:119px;">23719</td>
			<td>Light source</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">OpenPTV(http://www.openptv.net)</td>
			<td style="width:119px;"></td>
			<td>Open source particle tracking software (Note: available as a service for anyone who wants to use it without all the installation mess or computer power availability problems).</td>
		</tr>
	</tbody>
</table>

three-dimensional particle tracking velocimetry for turbulence applications: case of a jet flow

3D-PTV是一个定量的流量测量技术，该技术的目的是跟踪使用图像序列的立体记录三个维度的一组颗粒的拉格朗日路径。其基本组件，功能，约束和3D-PTV拓扑结构由高速摄像头，支持四视图分路器的优化技巧进行了描述和本文中讨论。该技术是在重新 ≈7000施加到圆形射流的中间流场（5 &lt;X / D &lt;25）。在欧拉帧拉格朗日流动特征和湍流量围绕射流原点的下游10的直径，并在从所述喷射芯各种径向距离估计。拉格朗日属性包括轨迹，速度和选定的颗粒的加速度，以及流路，其从所述的Frenet-Serret等式获得的曲率。在位于十的横平面围绕喷射心轴的三维速度和湍流场的推定直径射流的下游与文献相比较，并在从喷射芯各种径向距离得到大规模流向速度运动的功率谱。

的照片，并将设置的示意图示于图 1和2。校准目标，在基准标记上反射的视图分离器和3D校准重建在图 3中示出。公认的校准目标的RMS为7.3微米，5.7微米和141.7微米的流向X，翼展方向y和深度z方向。在z -协调的相对较高的RMS是由于相对于那些在其它方向和相比x和y坐标与z轴四个视图相对小角度的减小目标...

Watch this Scientific Journal Video about Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow at JoVE.com

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

这里描述了基于高速摄像头，四视图分路器上的三维粒子跟踪测速（3D-PTV）系统。该技术是下游在雷诺数Re≈7000施加到从圆形管在十个直径附近的喷流。

湍流应用三维粒子跟踪测速：一喷流病例

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

three-dimensional-particle-tracking-velocimetry-for-turbulence

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12.1K 次观看.  University of Illinois at Urbana-Champaign. 这里描述了基于高速摄像头，四视图分路器上的三维粒子跟踪测速（3D-PTV）系统。该技术是下游在雷诺数Re≈7000施加到从圆形管在十个直径附近的喷流。 

视频: Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

Echo Particle Image Velocimetry

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 Consequently, a prerequisite for understanding, predicting, and controlling fluid flows is the capability to measure the velocity field with adequate spatial and temporal resolution.2 For velocity measurements in optically opaque fluids or through optically opaque geometries, echo particle image velocimetry (EPIV) is an attractive diagnostic technique to generate "instantaneous" two-dimensional fields of velocity.3,4,5,6 In this paper, the operating protocol for an EPIV system built by integrating a commercial medical ultrasound machine7 with a PC running commercial particle image velocimetry (PIV) software8 is described, and validation measurements in Hagen-Poiseuille (i.e., laminar pipe) flow are reported.
For the EPIV measurements, a phased array probe connected to the medical ultrasound machine is used to generate a two-dimensional ultrasound image by pulsing the piezoelectric probe elements at different times. Each probe element transmits an ultrasound pulse into the fluid, and tracer particles in the fluid (either naturally occurring or seeded) reflect ultrasound echoes back to the probe where they are recorded. The amplitude of the reflected ultrasound waves and their time delay relative to transmission are used to create what is known as B-mode (brightness mode) two-dimensional ultrasound images. Specifically, the time delay is used to determine the position of the scatterer in the fluid and the amplitude is used to assign intensity to the scatterer. The time required to obtain a single B-mode image, t, is determined by the time it take to pulse all the elements of the phased array probe. For acquiring multiple B-mode images, the frame rate of the system in frames per second (fps) = 1/&delta;t. (See 9 for a review of ultrasound imaging.)
For a typical EPIV experiment, the frame rate is between 20-60 fps, depending on flow conditions, and 100-1000 B-mode images of the spatial distribution of the tracer particles in the flow are acquired. Once acquired, the B-mode ultrasound images are transmitted via an ethernet connection to the PC running the PIV commercial software. Using the PIV software, tracer particle displacement fields, D(x,y)[pixels], (where x and y denote horizontal and vertical spatial position in the ultrasound image, respectively) are acquired by applying cross correlation algorithms to successive ultrasound B-mode images.10 The velocity fields, u(x,y)[m/s], are determined from the displacements fields, knowing the time step between image pairs, &Delta;T[s], and the image magnification, M[meter/pixel], i.e., u(x,y) = MD(x,y)/&Delta;T. The time step between images &Delta;T = 1/fps + D(x,y)/B, where B[pixels/s] is the time it takes for the ultrasound probe to sweep across the image width. In the present study, M = 77[&mu;m/pixel], fps = 49.5[1/s], and B = 25,047[pixels/s]. Once acquired, the velocity fields can be analyzed to compute flow quantities of interest.

An echo particle image velocimetry (EPIV) system capable of acquiring two-dimensional fields of velocity in optically opaque fluids or through optically opaque geometries is described, and validation measurements in pipe flow are reported.

回声粒子图像测速技术

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 ...

科研

工程学

Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.

The Vaporization of a Sacrificial Component (VaSC) process is used to fabricate microvascular structures. This procedure uses sacrificial poly(lactic) acid fibers to form hollow microchannels with precise 3D geometric positioning provided by laser micromachined guide plates.

制作三维微结构，用牺牲部分汽化过程

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material ...

High-speed Particle Image Velocimetry Near Surfaces

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. 
Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (&gt; 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows.
A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included.

A procedure for studying transient flows near boundaries using high-resolution, high-speed particle image velocimetry (PIV) is described here. PIV is a non-intrusive measurement technique applicable to any optically accessible flow by optimizing several parameter constraints such as the image and recording properties, the laser sheet properties, and analysis algorithms.

表面附近的高速粒子图像测速

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The ...

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

高速喷液嵌塞对移动表面的可视化

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model

Analysis of the size distribution of nanocrystals is a critical requirement for the processing and optimization of their size-dependent properties. The common techniques used for the size analysis are transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). These techniques, however, are not suitable for analyzing the nanocrystal size distribution in a fast, non-destructive and a reliable manner at the same time. Our aim in this work is to demonstrate that size distribution of semiconductor nanocrystals that are subject to size-dependent phonon confinement effects, can be quantitatively estimated in a non-destructive, fast and reliable manner using Raman spectroscopy. Moreover, mixed size distributions can be separately probed, and their respective volumetric ratios can be estimated using this technique. In order to analyze the size distribution, we have formulized an analytical expression of one-particle PCM and projected it onto a generic distribution function that will represent the size distribution of analyzed nanocrystal. As a model experiment, we have analyzed the size distribution of free-standing silicon nanocrystals (Si-NCs) with multi-modal size distributions. The estimated size distributions are in excellent agreement with TEM and PL results, revealing the reliability of our model.

We demonstrate how to determine the size distribution of semiconductor nanocrystals in a quantitative manner using Raman spectroscopy employing an analytically defined multi-particle phonon confinement model. Results obtained are in excellent agreement with the other size analysis techniques like transmission electron microscopy and photoluminescence spectroscopy.

使用拉曼光谱与多颗粒的声子坐月子型号纳米大小分布的特征

Analysis of the size distribution of nanocrystals is a critical requirement for the processing and optimization of their size-dependent properties. The ...

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

实验装置的研制归还系数在真空条件下测量

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing technology is used to fabricate particles with slender arms connected at a common center. Shapes explored are crosses (two perpendicular rods), jacks (three perpendicular rods), triads (three rods in triangular planar symmetry), and tetrads (four arms in tetrahedral symmetry). Methods for producing on the order of 10,000 fluorescently dyed particles are described. Time-resolved measurements of their orientation and solid-body rotation rate are obtained from four synchronized videos of their motion in a turbulent flow between oscillating grids with R&#955; = 91. In this relatively low-Reynolds number flow, the advected particles are small enough that they approximate ellipsoidal tracer particles. We present results of time-resolved 3D trajectories of position and orientation of the particles as well as measurements of their rotation rates.

We use 3D printing to fabricate anisotropic particles in the shapes of jacks, crosses, tetrads, and triads, whose alignments and rotations in turbulent fluid flow can be measured from multiple simultaneous video images.

测量的方向和旋转速率方法3D打印在湍流颗粒

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing ...

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data acquisition times with high spatial resolution. In the electronics industry there is serious interest in performing failure analysis on 3D microelectronic packages, many which contain multiple levels of high-density interconnections. Often in tomography there is a trade-off between image resolution and the volume of a sample that can be imaged. This inverse relationship limits the usefulness of conventional computed tomography (CT) systems since a microelectronic package is often large in cross sectional area 100-3,600 mm2, but has important features on the micron scale. The micro-tomography beamline at the Advanced Light Source (ALS), in Berkeley, CA USA, has a setup which is adaptable and can be tailored to a sample&#39;s properties, i.e., density, thickness, etc., with a maximum allowable cross-section of 36 x 36 mm. This setup also has the option of being either monochromatic in the energy range ~7-43 keV or operating with maximum flux in white light mode using a polychromatic beam. Presented here are details of the experimental steps taken to image an entire 16 x 16 mm system within a package, in order to obtain 3D images of the system with a spatial resolution of 8.7 &#181;m all within a scan time of less than 3 min. Also shown are results from packages scanned in different orientations and a sectioned package for higher resolution imaging. In contrast a conventional CT system would take hours to record data with potentially poorer resolution. Indeed, the ratio of field-of-view to throughput time is much higher when using the synchrotron radiation tomography setup. The description below of the experimental setup can be implemented and adapted for use with many other multi-materials.

For this study synchrotron radiation micro-tomography, a non-destructive three-dimensional imaging technique, is employed to investigate an entire microelectronic package with a cross-sectional area of 16 x 16 mm. Due to the synchrotron&#39;s high flux and brightness the sample was imaged in just 3 min&#160;with an 8.7 &#181;m spatial resolution.

利用同步辐射微断层调查的多尺度三维微电子封装

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data ...

Three-Dimensional Ultrasonic Needle Tip Tracking with a Fiber-Optic Ultrasound Receiver

Ultrasound is frequently used for guiding minimally invasive procedures, but visualizing medical devices is often challenging with this imaging modality. When visualization is lost, the medical device can cause trauma to critical tissue structures. Here, a method to track the needle tip during ultrasound image-guided procedures is presented. This method involves the use of a fiber-optic ultrasound receiver that is affixed within the cannula of a medical needle to communicate ultrasonically with the external ultrasound probe. This custom probe comprises a central transducer element array and side element arrays. In addition to conventional two-dimensional (2D) B-mode ultrasound imaging provided by the central array, three-dimensional (3D) needle tip tracking is provided by the side arrays. For B-mode ultrasound imaging, a standard transmit-receive sequence with electronic beamforming is performed. For ultrasonic tracking, Golay-coded ultrasound transmissions from the 4 side arrays are received by the hydrophone sensor, and subsequently the received signals are decoded to identify the needle tip&#39;s spatial location with respect to the ultrasound imaging probe. As a preliminary validation of this method, insertions of the needle/hydrophone pair were performed in clinically realistic contexts. This novel ultrasound imaging/tracking method is compatible with current clinical workflow, and it provides reliable device tracking during in-plane and out-of-plane needle insertions.

Accurate and efficient visualization of invasive medical devices is extremely important in many ultrasound-guided minimally invasive procedures. Here, a method for localizing the spatial position of a needle tip relative to the ultrasound imaging probe is presented.

基于光纤超声接收机的三维超声针尖跟踪

Ultrasound is frequently used for guiding minimally invasive procedures, but visualizing medical devices is often challenging with this imaging modality. ...

Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine micro-organisms, and/or sediments in the ocean, or fluidized bed reactors and combustion processes in engineered systems. In order to study the effect of turbulence on the kinematics of particles in such flows, simultaneous measurements of both the flow and particle kinematics are required. Non-intrusive, optical flow measurement techniques for measuring turbulence, or for tracking particles, exist but measuring both simultaneously can be challenging due to interference between the techniques. The method presented herein provides a low cost and relatively simple method to make simultaneous measurements of the flow and particle kinematics. A cross section of the flow is measured using a particle image velocimetry (PIV) technique, which provides two components of velocity in the measurement plane. This technique utilizes a pulsed-laser for illumination of the seeded flow field that is imaged by a digital camera. The particle kinematics are simultaneously imaged using a light emitting diode (LED) line light that illuminates a planar cross section of the flow that overlaps with the PIV field-of-view (FOV). The line light is of low enough power that it does not affect the PIV measurements, but powerful enough to illuminate the larger particles of interest imaged using the high-speed camera. High-speed images that contain the laser pulses from the PIV technique are easily filtered by examining the summed intensity level of each high-speed image. By making the frame rate of the high-speed camera incommensurate with that of the PIV camera frame rate, the number of contaminated frames in the high-speed time series can be minimized. The technique is suitable for mean flows that are predominantly two-dimensional, contain particles that are at least 5 times the mean diameter of the PIV seeding tracers, and are low in concentration.

The technique described herein offers a low cost and relatively simple method to simultaneously measure particle kinematics and turbulence in flows with low particle concentrations. The turbulence is measured using particle image velocimetry (PIV), and particle kinematics are calculated from images obtained with a high-speed camera in an overlapping field-of-view.

流成像技术同时测量湍流和粒子运动学

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine ...