Transition and Turbulent Drag Reducing Properties of Microfibrillated Cellulose and Papermaking Fibre Suspensions in Hagen Poiseuille Flow

这项工作将揭示一个长期存在的问题，在流体力学，即过渡到湍流管流，通过使用一种新的可视化技术。光学相干断层扫描（OCT），一个迅速崛起的技术，将与共焦扫描激光显微镜（CLSM）和超声多普勒测速（UDV），以创建详细的高分辨率的空间和时间的边界层中的流场的估计。通过这样做，我们将能够估计湍流量和捕获边界层中湍流结构的断层图像，并解决基本问题，如（i）流变学和表观壁面滑移之间的关系，（ii）湍流喷流和段塞在边界层中的结构的性质和（iii）湍流减阻的机制。虽然这项工作在许多自然和工业环境中的应用，该研究的动机是从纸浆和纸张的应用，即微纤化纤维素（MFC）和造纸悬浮液的流动行为。在过去的十年中，MFC在科学和商业领域的兴趣急剧增加。MFC具有独特的流变特性，进一步开发的关键是更深入地了解这种材料的流动特性。一个为期五年的项目拟由一名博士和一名硕士学生在机械工程化学进行。这项工作将主要是实验性的，对OCT图像进行某些方面的分析。

This work will shed light onto a longstanding problem in fluid mechanics, i.e. the transition to turbulence in pipe flow, through use of a novel visualization technique. Optical coherence tomography (OCT), a rapidly emerging technique, will be used in conjunction with confocal scanning laser microscopy (CLSM) and ultrasound Doppler velocimetry (UDV), to create detailed high-resolution spatial and temporal estimates of the flow field in the boundary layer. By doing so we will be able to estimate turbulence quantities and capture tomographic images of turbulent structures in the boundary layer and address fundamental questions such as (i) the relationship between rheology and apparent wall slip, (ii) the nature of the structure of the turbulent puffs and slugs in the boundary layer and (iii) the mechanism for turbulent drag reduction. Although this work has applications in a number of natural and industrial settings, the study is motivated from a pulp and paper application, namely the flow behavior of microfibrillated cellulose (MFC) and papermaking suspensions. The interest in MFC is dramatically increasing dramatically in both the scientific and commercial domains over the last decade. MFC has unique rheological properties and key to further development is a deeper understanding of the flow properties of this material. A five year project is proposed to be conducted by one PhD and one MASc student in either Chemical of Mechanical Engineering. The work will be primarily experimental, with some aspects of analysis of the OCT images.