平衡闪烁孔内振动管道周围流动场的可视化
Summary
该协议的目标是使详细流动场可视化，并在振动管道引起的平衡冲刷孔中确定近边界剪切和正常应力。
Abstract
本文提出了一种实验方法，用于对振动管道引起的平衡冲刷孔内的详细流动场进行可视化，确定近边界剪切和法线应力。该方法涉及在直线烟道中实现管道振动系统，用于管道位移跟踪和流量场测量的时间解析粒子图像速度测量（PIV）系统。利用交叉相关算法获得振动管道的位移时间序列。介绍了使用时间解析的 PIV 获取的原始粒子载重图像的步骤。使用多时间间隔交叉关联算法计算振动管道周围不同振动阶段的详细瞬时流量场，以避免具有较大速度梯度的流区域的位移偏置误差.通过应用小波变换技术，在获得相平均速度场之前，可以准确采集具有相同振动相的捕获图像。本文所述流量测量技术的主要优点是具有非常高的时空分辨率，可同时用于获取管道动力学、流场和近边界流应力。通过利用这一技术，可以更深入地研究复杂环境中的二维流场，例如振动管道周围的流场，以更好地了解相关的复杂冲刷机制。
Introduction
海底管道广泛用于海上环境，用于流体或氢碳产品输送。当管道被放置在可腐蚀的海底时，由于管道本身的波浪、电流或动态运动（强迫振动或涡旋引起的振动）1、2 ，管道周围的冲刷孔可能会形成。为了增进对海底管道周围冲刷机制的理解，除了管道-流体-海底相互作用区域内的湍流场测量和床切和正常应力估计外，还有必要测量冲刷孔尺寸1，2，3，4，5，6，7。在床切和正常应力极难确定的环境中，由于流场不稳定且底部边界粗糙，可测量瞬时近边界应力（在边界上方约 2 mm 处）用作他们的代理8，9。在过去的几十年中，在振动管道周围的冲刷被研究和出版，没有定量地呈现在冲刷孔3，4，管道周围复杂的流动场的值。 5，10，11，12，13，14，15，16，17， 18.因此，该方法的目的是为详细流场的可视化提供一种新的实验方案，并确定由强制振动管道引起的平衡冲刷孔内的近边界剪切和法线应力。应该指出的是，本研究中的管道-流体-海底相互作用过程是在静止的水环境中，而不是单向电流和波的。
该实验方法由两个重要部分组成，即：（1）管道（强制）振动模拟;和 （2） 管道周围流动场的测量。在第一个组件中，使用振动系统（具有伺服电机、两个连接弹簧和管道支撑框架）在实验烟道中模拟振动管道。通过调整连接弹簧的电机速度和位置，可以模拟不同的振动频率和振幅。在第二个组件中，采用时间解析粒子图像速度测量（PIV）和小波变换技术，以获得不同管道振动阶段的高时空分辨率流场数据。时间解析的 PIV 系统由连续波激光器、高速摄像机、种子粒子和交叉相关算法组成。虽然PIV技术已被广泛用于获得稳定的湍流场19，20，21，22，23，24，25在复杂的不稳定流动场条件下的应用，如管道-流体-海底相互作用的情况，在8、9、26、27等情况下相对有限。原因可能是PIV技术传统的单时间隔交叉关联算法无法准确捕获存在相对高速梯度的不稳定流动场中的流特征9。 20.本文所描述的方法可以使用多时间间隔交叉关联算法9，28来解决这个问题。
Protocol
1. 实验室安全检查 查看与使用激光和烟道系统相关的安全规则。 确保满足实验室的安全培训要求。注：在本实验中，使用了一组波长为532nm的5W空气冷却连续波激光器，以及一个尺寸为11米、宽0.6米、深度0.6米的玻璃面直流波激光器（图1）。这两种装置的基本安全建议如下： 在测试前检查激光视线中的潜在反射表面;操作激光设备时佩戴安全护目镜。…
Representative Results
图3显示了管道位移跟踪和瞬时速度计算的原始图像与处理图像的比较示例。如图3 b所示，对原始图像中的播种颗粒和噪声进行过滤，并保留闪亮的管道边缘，以获得位移时间序列。如图3c所示，拉普拉西亚滤波器过滤出种子颗粒、管道边缘和海底表面周围的光散射/反射。振动管道的位移时间序列示例如图4</stron…
Discussion
本文提出的方案描述了一种利用PIV技术在平衡冲刷孔中对二维流动场进行可视化和在强制振动管道周围近边界流动应力场的测定方法。由于设计的管道运动沿y方向是一维的，因此准备和调整管道模型和振动系统以实现这一目标是成功实现的关键前提。管道沿x方向的任何不良运动都可能导致不对称的流动场和围绕振动管道的冲刷孔形成。除装置效果外，为实验选择管道的振动频率和?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
这项工作得到了国家自然科学基金（51709082）和中央大学基础研究基金（2018B13014）的支持。
Materials
| Camera control software | Vision Research | Phantom PCC 2.6 | Camera control, image data acquisition and processing |
| Camera lens | Nikon Chiyoda | Nikor 60mm, f=2.8 prime lens | |
| Continuous wave laser | Beijing Laserwave optoelectronics technology co. ltd. | PIV Laser source; Nd:YAG laser, 532 nm; air-cooling | |
| High-speed camera | Vision Research | Phantom Miro 120 | Image data recording |
| Laser sheet forming optics | Thorlabs Inc | Transform the point laser to a thin laser sheet | |
| Pipeline model | ZONCEPZ SOLUTIONS | Acrylic cylinder with a diameter of 35 mm | |
| Pipeline vibration system | ZONCEPZ SOLUTIONS | Consists of a sever motor, two connecting springs and pipeline supporting frames. | |
| PIV calcuation software | AXESEA Engineering Technology Limited Co. | PISIOU | Image data processing for obtaining flow fields and pipeline displacements |
| PIV seeding materials | Shimakyu | Aluminum powder with a diameter of 10um | |
| Recirculating flume | SZU ENGINEERING PTE LTD | Glass-sided, 11 m long, 0.6 m wide, and 0.6 m deep | |
| Tri-pod | MANFROTTO | SKU MT190GOC4US 410 | Camara supporting |
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Cite This Article
Guan, D., Chiew, Y., Wei, M., Hsieh, S. Visualization of Flow Field Around a Vibrating Pipeline Within an Equilibrium Scour Hole. J. Vis. Exp. (150), e59745, doi:10.3791/59745 (2019).