测量的方向和旋转速率方法3D打印在湍流颗粒
Summary
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.
Abstract
实验方法都用于测量在湍流流体流动各向异性颗粒的旋转和平移运动。三维印刷技术用于制造具有在一个共同的中心连接的细长臂的颗粒。探索形状杂交（两个垂直杆），插孔（三个垂直杆），黑社会（三个杆三角平面对称），和四分体（四臂在四面体对称）。为年产10000荧光染色的颗粒的顺序上的方法进行说明。它们的取向和固体旋转速度的时间分辨测量从他们的运动四个同步视频中的紊流被Rλ= 91振荡网格在这种相对低雷诺数流之间得到的平流输送颗粒是足够小它们近似椭圆示踪粒子。我们提出的作为粒子的位置和方向时间分辨三维轨迹的结果以及它们的旋转速度的测量。
Introduction
在最近发布，我们推出了使用多个修长的手臂，用于测量动荡1粒子的旋转运动由粒子组成的。这些颗粒可以利用三维打印机使用多个摄像机的旋转速度来制造，并且可以精确地测量他们的位置，方向，和。使用工具从细长体理论，可以证明，这些粒子有对应的有效椭球2，并且这些粒子的旋转运动是相同的各自的有效的椭球。与相同长度的对称武器的粒子旋转球一样。一个这样的颗粒是插口，其具有附接在其中心三个相互垂直的臂。调整千斤顶的臂的相对长度可形成粒子等同于任何三轴椭球。如果一个臂的长度被设定等于零，这创建了一个交叉，其等效椭圆体是一个磁盘。修长制成颗粒武器背起他们的固体椭同行的固体体积的一小部分。其结果是，他们滓更慢，这使得它们更容易密度匹配。这允许更大的颗粒的研究比是方便与固体椭圆颗粒。此外，成像可以在高得多的粒子浓度，因为颗粒阻挡来自其它颗粒的光的较小部分进行。
在本文中，对于制造和3D印刷颗粒的跟踪方法被记录。用于跟踪由多个相机所看到从粒子位置球形颗粒的平移运动的工具已被几个小组3,4-开发的。伯尔萨等 5扩展这种方法来跟踪使用由多个摄像机看到的杆的位置和方向的棒。这里，我们提出的用于制造的各种各样的形状的颗粒和重建他们的3D取向的方法。这提供日Ë可能性具有复杂形状的颗粒3D追踪扩展到范围广泛的新应用。
该技术有进一步的发展，因为宽范围的粒子的形状可设计的巨大潜力。许多这些形状在环境流量，其中浮游生物，种子和冰晶进来形状繁多直接应用。粒子的旋转和湍流6基本小型性质之间的联系表明，这些粒子的旋转研究提供了新的方式来看待汹涌的级联过程。
Protocol
Representative Results
Discussion
涡度和湍流流体流动粒子的旋转测量已长期被认为是在实验流体力学的重要目标。小球在湍流的固体旋转等于一半的流体涡，但球的旋转对称性还使他们的固体旋转困难的直接测量。传统上，流体涡已经使用复杂的多传感器测量，热丝探头14。但是这些传感器只获得在具有大的平均流速的气流单点涡测量。其他涡测量方法已经开发了。例如，苏和达姆采用基于标图像15LÜTHI，Tsinober…
Disclosures
The authors have nothing to disclose.
Acknowledgements
我们感谢Susantha Wijesinghe谁设计和建造我们使用了图像压缩系统。我们承认从美国国家科学基金会资助DMR-1208990的支持。
Materials
| Condor Nd:YAG 50W laser | Quantronics | 532-30-M | |
| High speed camera | Basler | A504k | |
| High speed camera | Mikrotron | EoSens Mc1362 | |
| Rhodamine-B | ScienceLab.com | SLR1465 | |
| Sodium Hydroxide | Macron | 7708 | Pellets. |
| 500 Connex 3D printer | Objet | Used to make smaller particles. Particles ordered from RP+M (rapid prototyping plus manufacturing). | |
| VeroClear | Stratasys | RGD810 | Objet build material. |
| Form 1+ 3D printer | Formlabs | Used to make larger particles. | |
| Clear Form 1 Photopolymer Resin | Formlabs | ||
| Cylindrical and spherical lenses | |||
| 200, 100, 50 mm macro camera lenses | F-mount. | ||
| Ultrasonic bath | Sonicator | ||
| Calcium Chloride | Spectrum Chemical Mfg. Corp. | CAS 10043-52-2 | Pellets. |
| LabVIEW System Design Software | National Instruments | Used to trigger cameras, control grid, and trigger laser. | |
| XCAP Software | EPIX | Used with LabVIEW to trigger cameras. | |
| MATLAB | Mathworks | Used for all image and data analysis. Programs for extracting 3D orientations from multiple images are included with this publication. | |
| OpenPTV: Open Source Particle Tracking Velocimetry | OpenPTV Consortium | ||
| ParaView | Kitware | ||
| AutoCAD | AutoDesk | Used to design all particles. Screenshots of particle designs are all of AutoCAD. | |
| Mesh with 0.040 x 0.053 inch holes | Industrial Netting | XN5170–43.5 | |
| Camera filters | Schneider Optics | B+W 040M |
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