MRI: Development of Combined Holographic and Tomographic PIV Systems for Time Resolved, Multiscale, 3D Velocity Measurements Within Turbulent Shear Flows

0923391 Katz“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“这项建议的目的是开发一种系统，可以执行多尺度，时间分辨，三维速度测量内的流体流动的有限样本体积。该仪器集成并扩展了两种最先进的3D流量测量技术的能力。有了这一独特的工具，将大大有助于解决各种各样的问题。近期的目标是集中在高雷诺数湍流边界层内的流动光滑和粗糙的墙壁，DHM完全解决内部和层析PIV覆盖整个边界层周围的全息体积。实验将在JHU的光学折射率匹配设施中进行，该设施可以实现无障碍的近壁测量，即使在粗糙度元件之间也是如此。时间分辨的3D测量将提供前所未有的分辨率和跨越四个数量级的尺度范围。数据将用于解决几个基本问题，包括：（i）外层结构对缓冲层湍流的影响;（ii）与LES有关的壁面模拟问题，例如惯性层结构和壁面应力之间的关系，以及不稳定性和瞬时流向曲率对壁面应力的影响;（iii）完全解析流动所需的长度尺度;（iv）粗糙子层上方粗糙度和湍流产生的流动结构之间的关系。该系统也将用于研究湍流冠层流。

0923391Katz"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."The objective of this proposal is to develop a system that can perform multiscale, time resolved, 3D velocity measurements within a finite sample volume of a fluid flow. This instrument integrates and extends the capability of two state-of-the-art, 3D flow measurement techniques. There is a wide range of problems that would greatly benefit from availability of this unique instrument. The near-term objective is to focus on the flow within high Reynolds number turbulent boundary layers over smooth and rough walls, with DHM fully resolving the inner part and tomographic PIV covering the entire boundary layer surrounding the holographic volume. Experiments will be performed in the optically index-matched facility at JHU that enables unobstructed near-wall measurements, even between roughness elements. The time-resolved 3D measurements will provide unprecedented resolution and range of scales spanning four orders of magnitude. Data will be used for addressing several fundamental issues including: (i) Impact of outer layer structures on buffer layer turbulence; (ii) Wall modeling issues related to LES, e.g. relationships between inertial layer structures and wall stresses, and impact of unsteadiness and instantaneous streamwise curvature on wall stress; (iii) Required length scales for fully resolving the flow; and (iv) Relationships among flow structures generated by roughness and turbulence above the roughness sublayer. This system will also be used for investigating turbulent canopy flows.