Collaborative Research: Modifications of turbulent boundary layer structure by wall permeability and surface-subsurface interactions: an innovative experimental approach

在许多环境和工业流动中，例如在河流中，在植被覆盖的树冠上，在热交换器中，在膜管反应器和碳氢化合物井中，湍流在多孔、可渗透的表面上移动是无处不在的。然而，尽管这些流动在许多科学分支中具有广泛的重要性，但对可渗透边界的湍流物理学仍然知之甚少，目前阻碍了我们预测气体、颗粒、微生物和污染物进出这些表面的运动。该项目将开发和利用最新的光流测量技术，为可渗透表面上和表面内的3D流动结构提供独特的新数据，以及这些流动之间的相互作用。该项目有望改变对地表-地下湍流相互作用的理解，并能够测试有关这些表面上湍流性质的几个关键问题，以及随着渗透层类型的改变和上覆流速的变化，这种流动结构是如何变化的。实验室实验将与水流和沉积物的折射率相匹配，从而允许在可渗透沉积层的上方和内部进行光学测量。此外，新的全光学相机技术将用于定量三维体积内的三维流动，包括可渗透表面内部和上方。这些技术的结合打开了在如此复杂的流动中从未获得过的定量信息的可能性。该项目将在合作和跨学科的研究环境中培训两名博士研究生，掌握最先进的实验技术。这些独特的数据将有助于开发透水表面流动的新概念模型，并为指导这些流动的后续数值模拟提供必要的数据。这些数据将用于解释在一系列可渗透表面上移动的湍流如何被渗透率所改变，从而研究流体动力学对穿过流体-沉积物界面的细颗粒命运的控制。例如，这些结果将与解释天然河床的行为直接相关，其中砾石可以被细颗粒沉积物填充，并且可以控制纳米颗粒和污染物在地表和地下流动之间的交换。

1236527/1235726Best/ThurowTurbulent flows moving over a porous, permeable, surface are ubiquitous in many environmental and industrial flows, such as in rivers, over vegetated canopies, in heat exchangers, membrane tube reactors and hydrocarbon wells. However, despite the widespread importance of these flows in many branches of science, the physics of turbulence across permeable boundaries remains poorly understood, and currently hampers our ability to predict the movement of gases, particles, microbes and pollutants into and out of such surfaces. This project will develop and utilize the latest techniques in optical flow measurement to provide unique new data on the structure of 3D flow above and within permeable surfaces, and critically the interactions between these flows. The project is expected to transform the understanding of surface-subsurface turbulent flow interactions, and enable testing of several key questions concerning the nature of turbulence over such surfaces, and how this flow structure changes as the type of permeable bed is altered and the overlying flow velocity is varied. Laboratory experiments will match the refractive index of the flow and sediment, thus permitting optical measurements to be achieved above and within permeable sediment beds. Additionally, new plenoptic camera techniques will be used for the quantification of three-dimensional flow within a 3D volume, both within and above the permeable surface. The combination of these techniques opens up the possibility of quantitative information that has never been gained before within such complex flows. The project will enable the training of two PhD students in state-of-the-art experimental techniques within a collaborative and interdisciplinary research environment. These unique data will allow development of new conceptual models for flow over permeable surfaces and provide essential data to guide subsequent numerical modelling of these flows. These data will be used to explain how turbulent flows moving over a range of permeable surfaces may be modified by the permeability, and thus examine the fluid dynamic controls on the fate of fine particles moving across the fluid-sediment interface. For instance, these results will be of direct relevance in interpreting the behavior of natural river beds, where gravels can become infilled with fine-grained sediment, and which can control the exchange of nanoparticulates and contaminants between surface and subsurface flows.