Name: visualizing hyporheic flow through bedforms using dye experiments and simulation
Uploaded: 2015-11-18T15:00:00.000+00:00
Duration: 9 min 49 s
Description: Watch this Scientific Journal Video about Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation at JoVE.com

This material is based upon work supported by National Science Foundation grants EAR-0810270, EAR-1215898, and EAR-1344280, as well as an&#160;NSF Graduate Research Fellowship.

1.仿真软件<ol><li>使用本节所述的软件。 <ol><li>下载并安装免费/开源的多智能体建模语言和仿真平台，的NetLogo（可用<a href="http://ccl.northwestern.edu/netlogo/">:http://ccl.northwestern.edu/netlogo/，</a>版本5.1或更高版本）。 注:该软件是免费提供的成本和运行在所有主要操作系统（Windows / Mac上/ Linux的）。 </li><li>下载伴随该实验室过程中的两个具体的仿真脚本文件（mousedrop.nlogo和interface.nlogo）。 (Available: <a href="http://modelingcommons.org/browse/one_model/4259">http://modelingcommons.org/browse/one_model/4259</a> and <a href="http://modelingcommons.org/browse/one_model/4258">http://modelingcommons.org/browse/one_model/4258</a> ) 注意:一旦仿真平台的安装和这些文件下载完毕后，双击这些文件会自动打开牛逼他模拟了起来，准备运行。 </li></ol></li></ol> 2.水槽演示<ol><li>建立实验室水槽，以便所有的参数（ 表1）落入mousedrop仿真参数范围限制内。 注意:约束可以在mousedrop进行调整，如果通过编辑滑块所需的物理系统。 <ol><li>倒入一层沙子约15-25厘米到水槽。测量和记录下列标准方法32,33的水力传导率沙和孔隙率。 </li><li>随着水约20-30厘米填写的水槽。 </li><li>启动水槽和提高流速的水平，是足够快，以移动砂粒，从而创造底形。 注:流速可以进一​​步调节到缩小底形特征与实践。底形尺寸的流速，水的深度和砂性能的结果。 </li><li>允许底形发展FO- [R 12-24小时，形成天然的沙丘/波纹形态。为了加快这一进程，人工塑造定期的沙丘，然后允许输沙为4-12小时。另外，手动形成规则的三角形沙丘。 注意:常规三角沙丘将产生定期潜流交换模式，但将不会显示尽可能多的复杂性，因为天然沙丘/波纹底形。 </li><li>一旦所需的河床得以实现，减少水流量，直到底泥运输放缓，底形特征不再变化。 <ol><li>直观地观察沉积物颗粒，包括床上运动，减少流量，直至运动停止。 注意:这将保留在床的形态为实验的持续时间。 </li><li>为了证实慢，情景运动不发生，标记或照片底形的位置，然后观察在以后的时间。 注意:唯一重要的是底形不要过度实验的时间帧显著移动，所以，可提供足够的观测时间，以确认底形是稳定的。 </li></ol></li><li>调整水槽斜率和/或水深度，以实现下的简化的流率均匀流动。 <ol><li>通过设备控制通道坡度构造成水槽，通常是电动千斤顶或手摇。通过添加或从水槽中除去水调整水的深度。 注:在实验装置用在这里，在整个水槽上安装在下游端的枢轴，且斜率由机动千斤顶在上游端设置的。 </li><li>当泵在运行中，选择标有垂直于水槽的底部线两纵位置。在这些位置，用尺子来测量沿着这些垂直线的距离，水的表面与水槽的底部之间。 注意:根据所述水槽设置，水槽的底部可以用作比水槽的底部更好的倾斜基准线。选择LARGER纵向距离将产生更高的精度。 </li><li>调整水槽和/或水深度和重新测量的斜率，直到垂直距离的测量是相同的，达到均匀流动。测量沿两个纵向位置之间的水槽的底部的倾斜水平距离。 </li></ol></li><li>停泵并等待水停止移动;这将提供一个水平面上。重新测量水槽的顶部和水面之间的距离，在每个纵向位置。 注意:通道斜率等于这些测量之间的差，通过它们之间的倾斜的水平距离除以。 </li><li>重新启动水泵。 </li><li>选择一个测试段，这应该是接近其中沙丘已经形成的规则图案水槽的中间或下游端的一个位置。确保此部分包括至少一个完整的底形。 </li><li>测量并记录平均输沙深度（D）的日与任何手工测量色器件Ë试验段（透明的统治者是理想的）。为简单起见，用一个波峰和波谷的平均距离水槽底部。 </li><li>测量并记录平均底形高度在试验部分中，限定为在用尺子槽沉积物深度在波峰和沉积物深度之间的差异。测量几个底形，以获得平均的良好估计。 </li><li>再次使用标尺，测量并记录平均水深度（d）在试验部分中，定义为从水表面到砂床的平均距离。同样，使用平均水深在沙丘波峰和波谷的简单性。 </li><li>记录来自流量计的信道流量（Q），并计算出平均流速为 Q /（D * w）的 ， 其中 w是水槽的宽度，d是水深。 注意:我们的流量计被插入水槽的再循环回路。 </li><li>测量并记录在试验段的平均底形波长。典型地，测量波长为连续沙丘波峰之间的距离。 </li><li>打开Mousedrop模拟（中的NetLogo平台），并检查所有的测量是在模拟用户界面中指定的变量范围之内。如果测得的参数落在约束范围之外，调整由参数"滑​​块"右键单击仿真参数范围，选择"编辑"，并调整最大/最小值。 </li></ol></li><li>可视化潜流交换。 <ol><li>将相机设置在固定的位置（优选在三脚架）正交指着水槽壁与中心在图片中的测试部分的单个底形。 注意:这将避免倾斜的角度看问题。 </li><li>以一个测试图片来验证条件。调整灯光的反射，如果是一个问题。 </li><li>使用注射器和针头，使2-3小染料我njections靠近水槽壁。确保这些注射形成〜2厘米的圆形有色孔隙水的贴剂在不同的垂直和水平位置。请小心，在注射过程中尽量减少干扰沙床。 注:小体积的染料注射让用户看到更多的细节和查看单个流的路径。 </li><li>记录染料注射的开始时间，并采取的初始图象。 可选:它可以是教育跟踪的初始染料前沿与透明纸标记，使染料运动是容易观察到在实验室中，但是这些轮廓也将阻止在图象的染料方面的一小部分，所以有一个与贸易关闭。 </li><li>捕获在适当的时间间隔染料前沿位置。对于时间间隔摄影，用30秒的时间间隔给予流畅的效果。 </li></ol></li></ol> 3.模拟<ol><li>运行仿真1:Mousedrop和观察到的染料运输比较。<ol><li>打开名为Mousedrop.nlogo仿真脚本。 <img alt="图3" src="/files/ftp_upload/53285/53285fig2.jpg" width="600" /> 图2. Mousedrop。这说明，其中示踪剂是在一次7个不同的实例。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53285/53285fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> </li><li>调整表 1所示的，以匹配水槽实验条件的物理系统参数（具体地说拉姆达，BedformHeight，BedDepth，HydrCond，孔隙率，ChannelVelocity，深度，和斜率）。请务必输入输入参数时要特别注意单位。 </li><li>调整滑块时间1，时间2等 ，表明时候模拟跟踪颜色会发生变化。设置这些颜色变化，以便于仿真结果与观察的对比匹配观测时间。 注意:如果时间参数都设置为0，模拟将显示在整个单一的颜色。 </li><li>在所有参数设置，点击设置按钮 。 注:底形应该出现在模拟图。 </li><li>点击鼠标拖放按钮，表示虚拟示踪剂的起始位置。需要注意的是在该床的多个位置可以被点击。按住鼠标以释放更多的虚拟示踪剂。当模拟染料的运动，用鼠标或者跟踪染料方面（围绕染料的边界）或填写染区域的整个区域。 注:引入更多的虚拟示踪剂将导致仿真运行更慢。最佳的视觉效果将与计算机的性能有所不同。 </li><li>一旦所有的虚拟示踪剂已放置，你可以点击进入下一个计时按钮，将开始模拟，然后停止它在第一时间，或者你可以点击Go /停止按钮开始SIMUL通货膨胀下去。不要重复点击设置按钮，或示踪剂将不得不重新放置。 注意:一旦仿真开始运行时，速度被根据用于100模拟秒的速度场，然后在新的位置的速度计算计算出基于仿真参数各示踪剂的位置在等式4和5示踪剂移动并且过程重复进行，直至示踪剂离开系统。 </li><li> （可选）， 点击 Go /停止按钮反复暂停/继续模拟。在时间上比较在不同点的模拟和测量染料分布。 </li></ol></li><li>运行仿真2:接口。 <ol><li>打开名为接口脚本。 <img alt="图3" src="/files/ftp_upload/53285/53285fig3.jpg" width="600" /> 图3界面。这说明370示踪剂使用接口模拟通过地下流动。示踪PA部份效果显示，其中每个示踪剂已经因为它是在表面的水的地下界面启动。最终，所有的流动路径应该回归到地表水。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53285/53285fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 注:此脚本介绍了虚拟示踪剂在河床表面的通量加权方式的基础上计算出来的地下速度。这提供的水流入（和退出）的相对量的河床在不同位置的视觉表示。 </li><li>点击设置然后去/停止开始。 注意:这将运行使用默认设置的模拟。 再滴？开关被初始设置为关闭，所以累计停留时间分布将被绘制为时间的经过。 </li><li>观察使用默认参数的模拟后，点击进入/停止停止模拟。 </li><li&gt;更改一个或多个参数，然后点击设置然后去/停止 。 注意:这将重新开始模拟与已经选择的参数。 </li></ol></li></ol>

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The authors have nothing to disclose.

中联，水槽示范和粒子跟踪模拟提供了一个全面的介绍潜流流量的的受众。各级参加者提供视觉证据潜流交换的发生引起的河床，并在地下流动路径的可变性强下底形。这些程序可以作为孔隙水流动的一个简单的演示本科生或K-12的学生，也可以用在研究生课程结合了更深入介绍河流水力学，泥沙输移和潜流交换的机制。无论水平如何，使用这种简单的可视化模型作为互动技术可以让学生形成这些复杂和重要的现象比将通过抽象的理论和讨论达到一个更深入的了解。 虽然使用这些方法，物理系统和simulati之间的差异上不应该被看作是"错误"，但作为代替"教育时机"， 即起点，这将最终导致更大的学习的讨论。学生领导考虑了一些问题，其中包括:什么是所有的误差源（模型，测量和实验室程序）？哪一项可能有助于模拟和观测之间的差异？在模型的制定作了哪些简化假设？重要的是如何微小的差异，以及他们做模型"错"？由于统计学家乔治箱有句名言:"从本质上讲，所有的模型都是错误的，但有些是有用的。"34良好的科学模型捕获系统的某些基本特征，从而导致更好的了解，同时也忽略了细节，相关性较小到手头的问题。这个水槽实验室实验和相应的仿真n提供让学生在了解双方的优势和实验方法的模型和弱点了很好的学习。因此，不但学生获得更大的流畅性与潜流交换和溶质运移的核心概念，但他们已经了解的理论建设和数据收集之间的互补关系（和有时复杂的相互作用），计算机模拟和实验室试验之间。此外，实验室和模拟这种耦合促进通过质疑我们所知道的，我们如何知道它的重要的认知技能35约知识是如何通过科学的研究过程中获得的经验，发展。越来越多的研究证明体教学元认知的效果（即高层次思维）技能36-38。 有许多原因观测和模拟追踪轨迹之间的偏差。的过度横向移动在注射过程中针会造成在沙滩上的优惠流道，使染料直接逃进了水柱。我们的速度方程不包括横向或纵向扩散。在水槽中，底形几何比在仿真中定义的理想化正弦更加不对称。沉积物从来没有完全均匀;变化的包装和沉积物的大小会影响到当地的水力传导系数和孔隙度。虽然最好是通过降低水槽泵的转速使得染料注射之前，以尽量减少底形的迁移，某些迁移仍可能发生。底形迁移改变相对于底形波峰到所注入的染料，从而改变地下流体力学的位置。实验流道将始终从模拟不同，但示踪剂运动的一般模式不应该改变。根据这里所使用的实验条件下，存在的模型模拟和观察到的染色剂流速之间有很强的协议。 Additio<html>最终的复杂性，如沉淀物的异质性，分形底形地貌，地下水排泄，三维地形，跨渠道流动，而在水流的时空变化发生在许多自然系统。此处所描述的染料示踪方法可以用于通过料槽实验设置的适当修改，以探索这些过程的影响。这种方法可用于研究以及教学目的，如流动可视化是常用的测试假说约理事过程，并且还可以用来计算材料通量和质量平衡，对于流和沉积物床之间例子潜流交换通量21。染料示踪方法相似，这里描述已被用来确定河床形态，沉积物的异质性，地下水排放的影响，以及再充电潜流交换，以及评估诸如孔隙水引起的海浪39-42流相关进程。 内容"&gt;虽然这里使用的简单的流程模型表现出了相当忠实地再现严格控制的实验室条件下潜流流动，其​​在模拟复杂的自然系统的使用是有限的。我们的剧本写于的NetLogo编程语言，在这里主要是作为教学工具，因为它提供了一个简单的，免费的，开源的基于代理的仿真平台，因为它支持出色的可视化和方便用户操作的输入参数，便于学习。其他的方法已经发展到模拟出更复杂的系统的几何14潜流交换，20和泥沙结构43,44。多种免费/开源的工具 （例如，MODFLOW）和商业软件（ 例如，COMSOL）采用有限差分和有限元方法可能有助于在更复杂的建模潜流流几何形状和地下异质性15,45-48。

由于地表水的动作在流，河流或潮间带它创建头梯度驱动的水流入和流出的沉积物1。在河流系统的河床沉积物，其中该交换发生的部分是被称为潜流带2,3。这个区域是非常重要的，因为许多营养物质和污染物的存储，存放，或潜流带4-9范围内改变。的时间示踪剂花费在沉积物的量被称为停留时间。既停留时间和流动通道的位置会影响转化过程。影响流过泥沙的过程中认识的提高是需要预测溶质运移的河流和解决从材料的传播导致，如营养物质（例如沿海缺氧10,11）大环境的问题。尽管潜流交换的重要性，它往往不是在本科课程水文描述，流体力学，水力学等教育工作者希望增加潜流交换他们的课程可能会发现它有用有实验和数值模拟可视化，明确表明了这一过程。 河道弯度，周围的地下水水位和河床地形（如酒吧，河床和生物丘）都会影响潜流交换不同程度12-17。这项研究的重点河床，如沙丘和波纹，这通常是影响潜流流14,15键地貌特征。我们创建了一个数值模拟和实验室实验过有规律的一系列底形的可视化流程。此模拟基于以前的研究有关潜流流路，以容易观察到的系统特性15,18-21的本体。作为这项研究形成了科学背景的模拟，理论的主要方面简要总结如下。底形地形，T（X），计算公式如下: 方程1: <img alt="式（1）" src="/files/ftp_upload/53285/53285eq1.jpg" /> 其中 H是两倍底形的幅度，k是波数，和x是平行于平均河床表面的纵向尺寸。本底形地形的一个例子示于图1。 <img alt="图1" src="/files/ftp_upload/53285/53285fig1.jpg" /> 图1.参数定义和设置由用户控制在 接口 ，示踪粒子被释放在水/沉积物界面焊剂加权方式，并通过沉淀跟踪。如果节目径？"上"水示踪标记，他们一直在，展示自己的路径。当示踪剂返回到地表水，这改变吨他系统中的示踪剂的总数， 再下降时？设置为 "关"。的累积停留时间分布曲线示出这种变化通过绘制残留在沉积物床的初始数量作为时间的函数的示踪剂的数量的比率。如果再滴？是"上"，那么示踪剂让系统被替换在同一个流量加权的方式原厂颗粒，累积情节被禁用。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53285/53285fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <table fo:keep-together.within-page="1"><tbody><tr><td> 参数名称 </td><td> 单位 </td><td colspan="3"> 定义 </td><td> 接口 </td><td> Mousedrop </td></tr><tr><td>拉姆达（λ） </td><td>厘米</td><td colspan="3">底形的波长（见图1）&lt;/ TD&gt; <td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td> BedformHeight（H）的</td><td>厘米</td><td colspan="3">在两次底形幅度（见图1） </td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td> BedDepth（D） </td><td>厘米</td><td colspan="3">沉积物的深度（参见图1） </td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td> HydrCond（K） </td><td>厘米/秒</td><td colspan="3">导水率</td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>孔隙度（θ）的</td><td></td><td colspan="3">孔隙度</td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td> ChannelVelocity（U） </td><td>厘米/秒</td><td colspan="3">平均速度在地表水或通道</td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>深度（d） </td><td>厘米</td><td colspan="3">水深度（见图1） </td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>斜率（S） </td><td></td><td colspan="3">在河床和水面坡度</td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><tD&gt; <img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td> NumParticles </td><td></td><td colspan="3">释放到系统的粒子数。 </td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td></td></tr><tr><td> TIMEX（时间1，时间2 ..） </td><td>分</td><td colspan="3">在每个颜色发生变化的时间</td><td></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td> 模拟按钮 </td><td></td><td colspan="3"> 定义 </td><td> 接口 </td><td> Mousedrop </td></tr><tr><td>建立</td><td></td><td colspan="3">设定的最高使用参数显示的模拟</td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>去/停止</td><td></td><td colspan="3">启动和停止模拟</td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>步骤</td><td></td><td colspan="3">单击步骤会使一次性地通过。这使得用户可以减缓代码，看看在100秒的情况完全相同。 </td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td></td></tr><tr><td>清晰的路径</td><td></td><td colspan="3">清除所有从屏幕上，他的蓝色粒子的路径</td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>前进到下一次</td><td></td><td colspan="3">这将导致程序运行，直到下一个颜色变化时（TIMEX）</td><td></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>鼠标拖放</td><td></td><td colspan="3">这个按钮必须被点击之前的颗粒可以通过点击在地下位置被放置在地下。 </td><td></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>秀径？ </td><td></td><td colspan="3">如果显示，路径？处于"打开"的水粒子离开的蓝色表示在他们已经一条路径（参见图1）。 </td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td></tr><tr><td>重新降？ </td><td></td><td colspan="3">如果再下降？处于"打开"的颗粒被替换的助熔剂加权方式为每一个颗粒，它退出系统，累积积不起作用。当汉邦第一百退出潜流带如果再滴颗粒在系统中的数量减少？为"关"（见图1）。 </td><td><img alt="复选标记" src="/files/ftp_upload/53285/checkmark.jpg" /></td><td></td></tr></tbody></table> 表1.潜流参数和模拟控制。每个参数，按钮，滑块，可以由用户进行调整，给出在此表以及一个定义。 在该模拟中，两个过程诱导流体速度在沙床上。首先是因为与底形流流的相互作用。的速度头在诱导底形的水/沉积物接口也是近似正弦波，并通过从底形本身22的四分之一波长偏移。的速度头功能在表面地下界面上的幅度已近似从测量值作为16: GE ="总是"&gt; 方程2: <img alt="公式（2）" src="/files/ftp_upload/53285/53285eq2.jpg" /> 其中 U是平均表面水流速度，g为重力常数，d是水（图1中示出）的深度。的速度头函数由下式给出: 公式3: <img alt="公式3" src="/files/ftp_upload/53285/53285eq3.jpg" />该磁头函数然后可以用于通过求解拉普拉斯方程以恒定砂床深度20来计算的地下速度函数的底形为基础的部分。的孔隙水速度的第二组分是由系统，S，其对应于重力梯度头的斜率确定，收率 ​​流在下游方向成正比S / ftp_upload / 53285 / 53285eq_S_inline.jpg"/&gt;的最终功能孔隙水的速度是: 公式4: <img alt="公式4" src="/files/ftp_upload/53285/53285eq4.jpg" /> 公式5: <img alt="公式5" src="/files/ftp_upload/53285/53285eq5.jpg" /> 其中 ，u表示所述纵向速度分量，v是垂直速度分量，K为沉积物的平均水力传导率，是沉积物的平均孔隙率，y是垂直坐标，D是沉积物的深度。 粒子跟踪模拟创建，它使用的NetLogo建模语言和仿真平台23。这两种实现方式（Mousedrop.nlogo和Interface.nlogo）利用这些方程模型HYPorheic流着相同的模拟核心。主要的区别是示踪粒子的初始位置。Mousedrop允许用户放置地下内的任何地方模拟示踪剂。地下速度等式4和5是用来移动示踪以模拟染料注射实验。在接口方面，示踪总是沿着表面/地下边界放在通量加权方式。这模仿递送溶解和悬浮材料从表面的水进入孔隙水，这是理解潜流交换。示踪剂然后地下内移动，直到它重新到达流水。跟踪在水槽染料路径和模拟使用的NetLogo路径产生的流场的流线，只要在观察期间的流动条件和底形形态保持稳定。Interface.nlogo创建累积停留时间分布，其示出了的数量的比值示踪粒子残留在沉积物放置在时间0作为时间的函数示踪粒子的初始数量。 由于在最近的文献调查24所讨论的，仍然大约动手实验室实验与模拟实验室和计算机模型的相对优点中的教育研究界相当大的争议。在一方面，有些人认为"实践经验是学习的心脏"25，并警告说，节省成本的论点可能会助长更换动手基于计算机的模拟实验活动的，对损害学生的理解26。而另一方面，一些研究人员在科学/工程教育认为，模拟是至少一样有效，传统的动手实验室27，或在培养学生为中心的"发现式学习"28讨论计算机模拟的好处。尽管共识并没有被重新疼痛难忍，许多研究人员得出结论认为，理想状态下，计算机模拟应补充，而不是取代，动手实验室实验29,30。也有一些在科学和工程教育的举措，同时耦合物理实验和真实世界的感知与现象的计算机模拟; 例如 ，见"双焦建模"31。 学生可以有更深刻的概念性知识并通过与两个物理系统，以及基于计算机的仿真该系统的相互作用的更好的理解科研过程。此过程涉及具有学生进行溶质运输实验演示引力和底形诱导的潜流交换流动，匹配其自己的实验装置和结果用计算机模拟的相同的现象。这比较有利于学生的重要学习成果，和T的深入讨论他科学的方法和模型/理论建设，并通过数据收集实证验证之间的相互作用。执行此对比后，学生还可以利用基于计算机模拟的好处，通过改变模型参数快速探索多种替代方案。

<table><tbody><tr><td>Flume</td><td>Engineering Laboratory Design</td><td>Custom</td><td>Laboratory flume with clear sides for 24-48 hours. Alternatively a small teaching flume can be constructed for under 300 dollars following the guidelines provided in our supplementary materials.</td></tr><tr><td>Flowmeter</td><td>Rosemount&amp;nbsp;</td><td>8800 vortex&amp;nbsp;</td><td>This is located inside the recirculation loop of the flume</td></tr><tr><td>Sand</td><td>US. Silica</td><td>F30</td><td>Research-grade sand to form a layer 10-20 cm deep throughout the flume</td></tr><tr><td>Dye</td><td>Samples from food companies</td><td></td><td>Water-soluble food grade dye made into an aqueous solution. Dark colors like red, blue and green work best. (Avoid food dyes in propylene glycol.)</td></tr><tr><td>Syringe</td><td>HSW</td><td>4100.000V0</td><td>5-10 ml, &lt;em&gt;e.g.&lt;/em&gt; HSW Norm-Ject 2-part disposable syringe</td></tr><tr><td>Pipetting Needle</td><td>Cadence Science</td><td>7942</td><td>14-gage, 6-in blunt end,&amp;nbsp; to inject the dye deep into the sand.</td></tr><tr><td>Digital Camera</td><td>Any</td><td></td><td>Digital camera with steady tripod. (Time lapse cameras can be used to collect rapid evenly spaced data.) We used a Nikon D7000.</td></tr><tr><td>Ruler</td><td>Any</td><td></td><td>Transparent is best.</td></tr><tr><td>Measuring Tape</td><td>Any</td><td></td><td></td></tr><tr><td>Netlogo Software</td><td>CCL</td><td></td><td>&lt;a href=&quot;http://ccl.northwestern.edu/netlogo/&quot;&gt;http://ccl.northwestern.edu/netlogo/&lt;/a&gt;</td></tr><tr><td>Mousedrop.nlogo</td><td>Netlogo Commons</td><td>4259</td><td>&lt;a href=&quot;http://modelingcommons.org/browse/one_model/4259&quot;&gt;http://modelingcommons.org/browse/one_model/4259&lt;/a&gt;</td></tr><tr><td>Interface.nlogo</td><td>Netlogo Commons</td><td>4258</td><td>&lt;a href=&quot;http://modelingcommons.org/browse/one_model/4258&quot;&gt;http://modelingcommons.org/browse/one_model/4258&lt;/a&gt;</td></tr></tbody></table>

visualizing hyporheic flow through bedforms using dye experiments and simulation

沉积物孔隙空间和上覆水柱，堪称河流环境潜流交换之间的对流交换，推动河流和许多重要的生物地球化学过程溶质运移。为了提高通过视觉展示这些过程的了解，我们创建了一个潜流流动模拟的多主体的计算机建模平台的NetLogo。仿真结果表明虚拟示踪剂流经长满了二维河床一个河床。沉积物，流，和底形特性被用作输入变量的模型。我们举例说明如何将这些模拟匹配实验观测到的实验室水槽实验，根据测得的输入参数。染料被注入到水槽沉积物形象化孔隙水流动。用于比较的虚拟示踪粒子被放置在模拟中相同的位置。这加上模拟和实验室实验已成功应用于本科和graduaTE实验室直视河孔隙水的相互作用，并展示如何基于物理的流动模拟可以再现环境现象。生了该床的照片通过透明水槽壁和比较它们的染料在模拟同一次的形状。这导致非常相似的趋势，这使得学生更好地理解流动模式的数学模型两者。模拟还允许用户通过运行多个模拟快速查看每个输入参数的影响。这个过程也可以用在研究中的应用来说明基本流程，涉及界面通量和孔隙水运输，并支持定量的过程的建模。

在实验中结合使用模拟可以让学生观察的相似和理想化的数学模型和更复杂的真实系统之间的差异。 图4示出了比较染料注射的照片与Mousedrop模拟的例子。初始照片被用于确定在零时间的放置模拟染料示踪物，然后将模拟运行为34.2分钟，并与在当时拍摄的照片进行比较。总体模型对捕捉染色水的运动超过这个时间间隔一个出色的工作。第一染料斑点，位于底形的背风面，退出在模拟和实验系统，这两个沉积物。第二伸长和向下行进形成月牙形状，因为它展开，从而使一些示踪剂的离开原来的位置和一些上游的下游。最后染料斑点传播上游和一些示踪剂的行进更深<html>成沉淀物。这表明，潜流交换下的河床和潜流交换流量的模式涉及到底形几何形状发生。仿真和实验之间的强有力的协议，验证了模型方程为一阶的水平。这个过程也清楚地表明，潜流交换，与底形大小缩放一个显著的过程，并且在底形的孔隙水的，几乎一半上游流动。在仔细检查，但是，小的差异，可以观察到的和模拟染料交通之间看到。模拟比实际染料图案平滑和不作为深深伸入沉淀物。这些差异导致的测量误差和二阶物理效应从不规则底形的几何形状，可变性在沉积物填料等造成，如表2所记载的组合。 4"SRC ="/文件/ ftp_upload / 53285 / 53285fig4.jpg"/&gt; 图4.比较水槽染料前沿到模拟。染料注入到水槽和一个图片拍摄在时间0示踪物放入用Mousedrop在相同地点染料地下。示踪剂然后移动为34.2分钟模拟和仿真然后比较初始图象之后拍摄34.2分的图象。观察到的染料模式和模拟比较以及在以后的时间。还有由于不是由模型所捕获的流场空间变化有些差异。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53285/53285fig4large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <table fo:keep-together.within-page="1"><tbody><tr><td> 差异的常见来源 </td><td colspan="2"> 预期结果 </td></tr><tr><td>实际的头部轮廓差异ERS从假设的正弦曲线</td><td colspan="2">不对称的底形下的孔隙水流量</td></tr><tr><td>不规​​则系列底形</td><td colspan="2">在观测位置潜在偏差的流场</td></tr><tr><td>沙床不够深入</td><td colspan="2">在孔隙水分布的垂直压缩</td></tr><tr><td>非均匀（即，随时间变化）流过该床</td><td colspan="2">附加高程头组件叠加孔隙水流的一个附加组件（例如，底形下增加的孔隙水环流 ​​单元的非对称性。） </td></tr><tr><td>异质性包装沉积物</td><td colspan="2">在孔隙水的流动空间变异（沉积物具有较高的和较低的速度补丁） </td></tr><tr><td>沉积物时注射染料显著中断</td><td colspan="2">染料释放垂直通过量小时喷射孔</td></tr><tr><td>使用非水溶性染料或溶解不足或染料注射之前混合</td><td colspan="2">在孔隙水，非均匀孔隙水运输或慢动员染料从喷射位置汇集染料。 </td></tr><tr><td>测量不准确（通常是由于单位） </td><td colspan="2">这会导致显着错误的结果</td></tr><tr><td>假设的缺乏分散在模拟</td><td colspan="2">某些扩展是染料的形状</td></tr></tbody></table> 表2.资源差异的观察与模拟。错误的常见原因清单列举在此表中。

Watch this Scientific Journal Video about Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation at JoVE.com

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

可视化潜流流通过底形用染料试验及仿真

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

visualizing-hyporheic-flow-through-bedforms-using-dye-experiments

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Unit 1

Dimensional Analysis, Similitude, and Modeling

SCIENTISTS IN ACTION

12.1K 次观看.  St. Ambrose University. This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes. 

视频: Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Image-based Lagrangian Particle Tracking in Bed-load Experiments

Image analysis has been increasingly used for the measurement of river flows due to its capabilities to furnish detailed quantitative depictions at a relatively low cost. This manuscript describes an application of particle tracking velocimetry (PTV) to a bed-load experiment with lightweight sediment. The key characteristics of the investigated sediment transport conditions were the presence of a covered flow and of a fixed rough bed above which particles were released in limited number at the flume inlet. Under the applied flow conditions, the motion of the individual bed-load particles was intermittent, with alternating movement and stillness terms. The flow pattern was preliminarily characterized by acoustic measurements of vertical profiles of the stream-wise velocity. During process visualization, a large field of view was obtained using two action-cameras placed at different locations along the flume. The experimental protocol is described in terms of channel calibration, experiment realization, image pre-processing, automatic particle tracking, and post-processing of particle track data from the two cameras. The presented proof-of-concept results include probability distributions of the particle hop length and duration. The achievements of this work are compared to those of existing literature to demonstrate the validity of the protocol.

The manuscript presents a protocol for the conduction of bed-load sediment transport experiments where the moving particles are tracked by image analysis. The experimental facility, the procedures for run realization and data processing, and finally some proof-of-concept results are presented here.

基于图像的拉格朗日粒子跟踪在床载荷实验

Image analysis has been increasingly used for the measurement of river flows due to its capabilities to furnish detailed quantitative depictions at a ...

科研

环境科学

Visualization of Flow Field Around a Vibrating Pipeline Within an Equilibrium Scour Hole

An experimental method is presented in this paper to facilitate visualization of the detailed flow fields and determination of the near-boundary shear and normal stresses within an equilibrium scour hole induced by a vibrating pipeline. This method involves the implementation of a pipeline vibration system in a straight flume, a time-resolved particle image velocimetry (PIV) system for pipeline displacement tracking and flow fields measurements. The displacement time-series of the vibrating pipeline are obtained by using the cross-correlation algorithms. The steps for processing raw particle laden images obtained by using the time-resolved PIV are described. The detailed instantaneous flow fields around the vibrating pipeline at different vibrating phases are calculated by using a multiple-time-interval cross-correlation algorithm to avoid displacement bias error in the flow regions with a large velocity gradient. By applying the wavelet transform technique, the captured images that have the same vibrating phase are accurately cataloged before the phase-averaged velocity fields are obtained. The key advantages of the flow measurement technique described in this paper are that it has a very high temporal and spatial resolution and can be simultaneously used to obtain the pipeline dynamics, flow fields, and near-boundary flow stresses. By using this technique, more in-depth studies of the 2-dimensional flow field in a complex environment, such as that around a vibrating pipeline, can be conducted to better understand the associated sophisticated scour mechanism.

The goal of the protocol is to enable visualization of the detailed flow fields and determination of the near-boundary shear and normal stresses within an equilibrium scour hole induced by a vibrating pipeline.

平衡闪烁孔内振动管道周围流动场的可视化

An experimental method is presented in this paper to facilitate visualization of the detailed flow fields and determination of the near-boundary shear and ...

Combining Fluidic Devices with Microscopy and Flow Cytometry to Study Microbial Transport in Porous Media Across Spatial Scales

Understanding the transport, dispersion and deposition of microorganisms in porous media is a complex scientific task comprising topics as diverse as hydrodynamics, ecology and environmental engineering. Modeling bacterial transport in porous environments at different spatial scales is critical to better predict the consequences of bacterial transport, yet current models often fail to up-scale from laboratory to field conditions. Here, we introduce experimental tools to study bacterial transport in porous media at two spatial scales. The aim of these tools is to obtain macroscopic observables (such as breakthrough curves or deposition profiles) of bacteria injected into transparent porous matrices. At the small scale (10-1000 &#181;m), microfluidic devices are combined with optical video-microscopy and image processing to obtain breakthrough curves and, at the same time, to track individual bacterial cells at the pore scale. At larger scale, flow cytometry is combined with a self-made robotic dispenser to obtain breakthrough curves. We illustrate the utility of these tools to better understand how bacteria are transported in complex porous media such as the hyporheic zone of streams. As these tools provide simultaneous measurements across scales, they pave the way for mechanism-based models, critically important for upscaling. Application of these tools may not only contribute to the development of novel bioremediation applications but also shed new light on the ecological strategies of microorganisms colonizing porous substrates.

Breakthrough curves (BTCs) are efficient tools to study the transport of bacteria in porous media. Here we introduce tools based on fluidic devices in combination with microscopy and flow cytometric counting to obtain BTCs.

将流体设备与显微镜和流式细胞学相结合，研究跨空间尺度的多孔介质中的微生物传输

Understanding the transport, dispersion and deposition of microorganisms in porous media is a complex scientific task comprising topics as diverse as ...

The Diffusion of Passive Tracers in Laminar Shear Flow

A simple method to experimentally observe and measure the dispersion of a passive tracer in a laminar fluid flow is described. The method consists of first injecting fluorescent dye directly into a pipe filled with distilled water and allowing it to diffuse across the cross-section of the pipe to obtain a uniformly distributed initial condition. Following this period, the laminar flow is activated with a programmable syringe pump to observe the competition of advection and diffusion of the tracer through the pipe. Asymmetries in the tracer distribution are studied and correlations between the pipe cross-section and the shape of the distribution is shown: thin channels (aspect ratio &#60;&#60; 1) produce tracers arriving with sharp fronts and tapering tails (front-loaded distributions), while thick channels (aspect ratio ~1) present the opposite behavior (back-loaded distributions). The experimental procedure is applied to capillary tubes of various geometries and is particularly relevant to microfluidic applications by dynamical similarity.

A protocol for the study of the diffusion of passive tracers in laminar pressure-driven flow is presented. The procedure is applicable to various capillary pipe geometries.

无源示踪剂在层流剪切流中的扩散

A simple method to experimentally observe and measure the dispersion of a passive tracer in a laminar fluid flow is described. The method consists of ...

工程学

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to turbulent flow conditions are presented. For that purpose, the incipient motion of a single bead is studied on regular substrates that consist of a monolayer of fixed spheres of uniform size that are regularly arranged in triangular and quadratic symmetries. The threshold is characterized by the critical Shields number. The criterion for the onset of motion is defined as the displacement from the original equilibrium position to the neighboring one. The displacement and the mode of motion are identified with an imaging system. The laminar flow is induced using a rotational rheometer with a parallel disk configuration. The shear Reynolds number remains below 1. The turbulent flow is induced in a low-speed wind tunnel with open jet test section. The air velocity is regulated with a frequency converter on the blower fan. The velocity profile is measured with a hot wire probe connected to a hot film anemometer. The shear Reynolds number ranges between 40 and 150. The logarithmic velocity law and the modified wall law presented by Rotta are used to infer the shear velocity from the experimental data. The latter is of special interest when the mobile bead is partially exposed to the turbulent flow in the so-called hydraulically transitional flow regime. The shear stress is estimated at onset of motion. Some illustrative results showing the strong impact of the angle of repose, and the exposure of the bead to shear flow are represented in both regimes.

Two different methods for characterizing the incipient particle motion of a single bead as a function of the sediment bed geometry from laminar to turbulent flow are presented.

从层流到湍流条件下的规则基底表面初始粒子运动的可视化表征

Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to ...

Methods for Characterizing the Co-development of Biofilm and Habitat Heterogeneity

Biofilms are surface-attached microbial communities that have complex structures and produce significant spatial heterogeneities. Biofilm development is strongly regulated by the surrounding flow and nutritional environment. Biofilm growth also increases the heterogeneity of the local microenvironment by generating complex flow fields and solute transport patterns. To investigate the development of heterogeneity in biofilms and interactions between biofilms and their local micro-habitat, we grew mono-species biofilms of Pseudomonas aeruginosa and dual-species biofilms of P. aeruginosa and Escherichia coli under nutritional gradients in a microfluidic flow cell. We provide detailed protocols for creating nutrient gradients within the flow cell and for growing and visualizing biofilm development under these conditions. We also present protocols for a series of optical methods to quantify spatial patterns in biofilm structure, flow distributions over biofilms, and mass transport around and within biofilm colonies. These methods support comprehensive investigations of the co-development of biofilm and habitat heterogeneity.

Biofilms have complex interactions with their surrounding environment. To comprehensively investigate biofilm-environment interactions, we present here a series of methods to create heterogeneous chemical environment for biofilm development, to quantify local flow velocity, and to analyze mass transport in and around biofilm colonies.

方法表征的共同发展生物膜和生境异质性

Biofilms are surface-attached microbial communities that have complex structures and produce significant spatial heterogeneities. Biofilm development is ...

生物工程

Window on a Microworld: Simple Microfluidic Systems for Studying Microbial Transport in Porous Media

Microbial growth and transport in porous media have important implications for the quality of groundwater and surface water, the recycling of nutrients in the environment, as well as directly for the transmission of pathogens to drinking water supplies. Natural porous media is composed of an intricate physical topology, varied surface chemistries, dynamic gradients of nutrients and electron acceptors, and a patchy distribution of microbes. These features vary substantially over a length scale of microns, making the results of macro-scale investigations of microbial transport difficult to interpret, and the validation of mechanistic models challenging. Here we demonstrate how simple microfluidic devices can be used to visualize microbial interactions with micro-structured habitats, to identify key processes influencing the observed phenomena, and to systematically validate predictive models. Simple, easy-to-use flow cells were constructed out of the transparent, biocompatible and oxygen-permeable material poly(dimethyl siloxane). Standard methods of photolithography were used to make micro-structured masters, and replica molding was used to cast micro-structured flow cells from the masters. The physical design of the flow cell chamber is adaptable to the experimental requirements: microchannels can vary from simple linear connections to complex topologies with feature sizes as small as 2 &mu;m. Our modular EcoChip flow cell array features dozens of identical chambers and flow control by a gravity-driven flow module. We demonstrate that through use of EcoChip devices, physical structures and pressure heads can be held constant or varied systematically while the influence of surface chemistry, fluid properties, or the characteristics of the microbial population is investigated. Through transport experiments using a non-pathogenic, green fluorescent protein-expressing Vibrio bacterial strain, we illustrate the importance of habitat structure, flow conditions, and inoculums size on fundamental transport phenomena, and with real-time particle-scale observations, demonstrate that microfluidics offer a compelling view of a hidden world.

Microfluidic devices can be used to visualize complex natural processes in real time and at the appropriate physical scales. We have developed a simple microfluidic device that mimics key features of natural porous media for studying growth and transport of bacteria in the subsurface.

窗口上的一个微观世界：简单的微流体系统为研究多孔介质中的微生物运输

Microbial growth and transport in porous media have important implications for the quality of groundwater and surface water, the recycling of nutrients in ...

生物学

Flow Visualization in a Water Tunnel: Observing the Leading-edge Vortex Over a Delta Wing

Source: Jose Roberto Moreto, Gustaaf Jacobs and Xiaofeng Liu, Department of Aerospace Engineering, San Diego State University, San Diego, California
The delta wing, shown in Figure 1D, is a popular design in high-speed airplanes due to its superb performance in transonic and supersonic flight regimes. This type of wing has a small aspect ratio and high sweep angle, which reduces drag at high subsonic, transonic and supersonic flight regimes. The aspect ratio is defined as the wing span divided by the average chord <img align="middle" src="/files/ftp_upload/10459/10459eq1a.jpg" />.
An important advantage of the delta wing is its high stall angle. The stall of a delta wing is delayed compared to the stall of a high aspect ratio wing. This is because the lift of a delta wing is enhanced by the leading-edge vortex over the wing.
An effective way to observe this vortex flow phenomenon and study the vortex breakdown in a delta wing is by visualizing the flow in a water tunnel. By injecting dye in the flow surrounding a model from dye ports on the leading-edge, the vortex development and breakdown can be observed and its position measured. The data can also be used to estimate the stall angle.
<img src="/files/ftp_upload/10459/10459fig1.jpg" />
Figure 1. Typical wing planform shapes: A) Rectangular, with constant chord along span, B) elliptical, C) tapered, with variable chord along the span, and D) delta wing, an aft-swept wing with zero taper ratio.

Flow in a Water Tunnel: Leading-edge Vortex over a Delta Wing

水隧道中的流量可视化:在三角洲翼上观察前沿涡流

Source: Jose Roberto Moreto, Gustaaf Jacobs and Xiaofeng Liu, Department of Aerospace Engineering, San Diego State University, San Diego, California
The ...

教育

JoVE Science Education

航空工程

Surface Dye Flow Visualization: A Qualitative Method to Observe Streakline Patterns in Supersonic Flow

Flow visualization around or on a body is an important tool in aerodynamics research. It provides a method to qualitatively and quantitatively study flow structure, and it also helps researchers theorize and verify fluid flow behavior. Flow visualization can be divided into two categories: off-the-surface visualization and surface flow visualization. Off-the-surface flow visualization techniques involve determining the flow characteristics around the body of interest. They include but are not restricted to particle image velocimetry (PIV), Schlieren imaging, and smoke flow visualization. These techniques can provide qualitative as well as quantitative data on the flow around a body. However, these techniques are generally expensive and difficult to set-up. Surface flow visualization techniques, on the other hand, involve coating the body of interest with a dye to study flow on the surface. These techniques, which are more invasive in practice, include dye flow visualization and, more recently, use pressure-sensitive paint, which gives a detailed image of the flow on the body&#39;s surface. This allows researchers to visualize different flow features, including laminar bubbles, boundary layer transitions, and flow separation. Dye flow visualization, the technique of interest in the current experiment, provides a qualitative picture of the surface flow and is one of the simplest and most cost-effective surface flow visualization methods, specifically for visualizing gaseous flows on a body.
In this experiment, the surface flow behavior on six bodies are studied in supersonic flow. The streakline patterns are obtained using the dye flow visualization technique, and the flow paths, degree of flow attachment and separation, and location and type of shocks are identified and studied from the flow images.

Surface Dye Flow: Streakline Patterns in Supersonic Flow

表面染料流可视化:观察超音速流中条纹模式的定性方法

Flow visualization around or on a body is an important tool in aerodynamics research. It provides a method to qualitatively and quantitatively study flow ...

Visualization of Flow Past a Bluff Body

Source: Ricardo Mejia-Alvarez, Hussam Hikmat Jabbar and Mahmoud N. Abdullatif, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
Owing to the non-linear nature of its governing laws, fluid motion induces complicated flow patterns. Understanding the nature of these patterns has been the subject of intense scrutiny for centuries. Although personal computers and supercomputers are extensively used to deduce fluid flow patterns, their capabilities are still insufficient to determine the exact flow behavior for complex geometries or highly inertial flows (e.g. when momentum dominates over viscous resistance). With this in mind, a multitude of experimental techniques to make flow patterns evident have been developed that can reach flow regimes and geometries inaccessible to theoretical and computational tools.
This demonstration will investigate fluid flow around a bluff body. A bluff body is an object that, due to its shape, causes separated flow over most of its surface. This is in contrast to a streamlined body, like an airfoil, which is aligned in the stream and causes less flow separation. The purpose of this study is to use hydrogen bubbles as a method of visualizing flow patterns. The hydrogen bubbles are produced via electrolysis using a DC power source by submerging its electrodes in the water. Hydrogen bubbles are formed in the negative electrode, which needs to be a very fine wire to ensure that the bubbles remain small and track fluid motion more effectively. This method is suitable for steady and unsteady laminar flows, and is based on the basic flow lines that describe the nature of the flow around objects. [1-3]
This paper focuses on describing the implementation of the technique, including details about the equipment and its installation. Then, the technique is used to demonstrate the use of two of the basics flow lines to characterize the flow around a circular cylinder. These flow lines are used to estimate some important flow parameters like flow velocity and the Reynolds number, and to determine flow patterns.

Flow Around a Bluff Body, Bubbles and Von Karman Vortex Street

通过钝体流的可视化

Source: Ricardo Mejia-Alvarez, Hussam Hikmat Jabbar and Mahmoud N. Abdullatif, Department of Mechanical Engineering, Michigan State University, East ...