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首页> 外文期刊>Flow Measurement and Instrumentation >Rotating microchannel flow velocity measurements using the stationary micro-PIV technique with application to lab-on-a-CD devices
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Rotating microchannel flow velocity measurements using the stationary micro-PIV technique with application to lab-on-a-CD devices

机译：使用静止微型PIV技术旋转微通道流速测量，应用于实验室-A-CD设备

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The measurement of microfluidic flows is an essential instrument to understand the governing physical mechanisms at small scales. This fact has motivated the adaptation of well-established "macroscale" experimental technics to deal with the specificities of microfluidic flows; a prominent example is the micro particle image velocimetry (micro-PIV) technique. In a different manner, the progress experienced by experimental techniques to measure flows in rotating frames has been more limited, with most studies concerned with macroscale turbomachinery applications. It turns out that the scale reduction in this field establishes a new and important flow class, known as centrigually-driven microfluidics, with application to lab-on-a-CD devices. However, the experimental characterization of rotating microflows has been, so far, limited to bulk flow measurements and/or visualization practices. For that reason, in this work, we propose extending the stationary micro-PIV technique to undertake quantitative, whole-field, velocity measurements inside rotating microchannel flow platforms. For this task, actual lab-on-a-CD prototypes are used. This work develops in two parts. First, we describe the most relevant changes in the micro-Ply equipment viewing the introduction of the test section rotation, namely: (i) hardware changes related to the micro-PIV/CD synchronization and (ii) software changes aiming at the preservation of the velocity measurement accuracy, through the removal of the circumferential velocity component. While this last step follows a well-known methodology, called image de-rotation, we propose tackling it in a new and automated fashion by means of the image registration method, whose implementation and advantages are explained in detail here. The second part of this work evaluates the capabilities of the modified micro-Ply technique by critically assessing the results of preliminary tests undertaken in dynamical regimes where rotation is dominant. Here, we present for the first time velocity profile measurements of centrifugally-driven micro-channel flows, which display marked structural differences from classical stationary pressure-driven flows. The quality of these experimental profiles is further examined through comparisons with computational fluid dynamics simulations, based on the lattice Boltzmann method. Overall, this study indicates the effectiveness of the proposed micro-PIV system, which is able to accurately capture the most relevant physical features of rotating microfluidic flows over regions sufficiently far away from the walls. On the other hand, inside the boundary layers, the present micro-PIV measurements remain difficult to execute; the reasons for this limitation are discussed and clearly identified in the present preliminary studies, which pave the way for future studies in the field.
机译：微流体流动的测量是了解小尺度的控制物理机制的基本仪器。这一事实有动力适应建立的“Macroscale”实验技术来应对微流体流动的特异性;突出的例子是微粒图像速度（Micro-PIV）技术。以不同的方式，通过实验技术经历的旋转帧中的流动经历的进展已经更有限，大多数研究有关宏观涡轮机械应用。事实证明，该领域的规模减少建立了一种新的和重要的流量等级，称为中心的微流体，应用于实验室-A-CD设备。然而，到目前为止，旋转微流量的实验表征已经限于散装流量测量和/或可视化实践。因此，在这项工作中，我们提出延长静止微PIV技术来进行旋转微通道流平台内部的定量，全场，速度测量。对于此任务，使用实际的实验室-CL-CD原型。这项工作在两部分中发展。首先，我们描述了查看测试部分旋转引入的微层设备中最相关的变化，即：（i）与微PIV / CD同步相关的硬件变化和（ii）软件改变旨在保存通过移除圆周速度分量的速度测量精度。虽然该最后一步遵循了一种众所周知的方法，称为图像去旋转，但我们通过图像登记方法提出以一种新的和自动的方式解决其实现和优点。本作品的第二部分通过批判性地评估动态制度所采取的初步测试的结果来评估改性微型技术的能力。这里，我们介绍了离心驱动的微通道流的第一次速度分布测量，其显示与经典静止压力驱动的流动的显着的结构差异。通过与计算流体动力学模拟的比较，进一步检查这些实验轮廓的质量，基于格子Boltzmann方法。总的来说，该研究表明了所提出的微PIV系统的有效性，其能够精确地捕获旋转微流体流过远离墙壁的区域的最相关的物理特征。另一方面，在边界层内部，目前的微PIV测量仍然难以执行;在目前的初步研究中讨论和清楚地识别了这种限制的原因，这些研究可以为该领域的未来研究铺平道路。

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