Turbulent flow over walls and around solid objects

提出的研究程序采用数值和实验相结合的方法来研究湍流。湍流是工业和环境应用中最普遍的流动形式，其特点是动量和标量的输运水平增强。通常，湍流涉及到固体表面的存在，这会显著改变湍流结构，并使传输特性更难以预测以达到设计目的。提出的数值模拟和实验将加强我们对符合这一情景的流动的基本理解。这项研究将在四个具体项目的背景下进行，所有这些项目都与固体表面上的湍流有关。第一个应用考虑了安装在边界层流中的有限圆柱体后面的尾迹。特别令人感兴趣的是紧邻圆柱体后面的复杂尾流--或扰动流动区域。这种流动情景在某些方面类似于短排气烟囱。第二种流动考虑平坦表面上的平壁射流，平坦表面既可以是光滑的，也可以是覆盖着表面粗糙度的。对于粗糙表面，壁面射流上的表面摩擦阻力的行为还没有被很好地理解。请注意，在某些方面，有限圆柱体类似于单一的表面粗糙度元素。要考虑的第三种流动是含有固体颗粒的气体或液体的多相流动。在这种情况下，固体表面在流体中移动，固体粒子将产生微小的尾迹并相互作用。这种流动方案与一些农业机械应用中的颗粒材料气力输送和采矿应用中的液体泥浆流动有关。第四个项目是最新颖的，与流动通过多孔组织支架有关，这是一个正在开发的生物医学应用。正在提议的研究计划将在萨斯喀彻温大学机械工程流体动力学小组内进行。它将有助于促进我们的基本理解，并解决加拿大工业面临的一些紧迫的技术挑战。

The proposed research program uses both numerical and experimental methods to study turbulent flow. Turbulence is the most prevalent flow regime in industrial and environmental applications, and is characterised by enhanced levels of transport for momentum and scalar quantities. Often, turbulent flow involves the presence of a solid surface, which then significantly modifies the turbulence structure and makes the transport characteristics more complex to predict for design purposes. The numerical simulations and experiments being proposed will enhance our fundamental understanding of flows that fit this scenario. The research will be pursued in the context of four specific projects all of which relate to turbulent flow over a solid surface. The first application considers the wake behind a finite cylinder mounted in a boundary layer flow. Of special interest is the complex wake -- or region of disturbed flow -- immediately behind the cylinder. This flow scenario in some ways resembles a short exhaust stack. The second flow considers a plane wall jet over a flat surface, which can be either smooth or covered with surface roughness. The behaviour of the skin friction drag on the wall jet for rough surfaces is not yet well understood. Note that in some ways a finite cylinder resembles a single element of surface roughness. The third flow to be considered is the multiphase flow of a gas or liquid with solid particles. In this case, the solid surface is moving through the fluid, and the solid particles will generate small wakes as well as interact with each other. This flow scenario relates to pneumatic conveyance of granular material as in some agricultural machinery applications and liquid slurry flow in mining applications. The fourth project is the most novel and pertains to flow through a porous tissue scaffold, which is a developing biomedical application. The research program being proposed will be conducted within the fluid dynamics group in Mechanical Engineering at the University of Saskatchewan. It will serve to advance our fundamental understanding and also address some pressing technical challenges being encountered by Canadian industry.