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

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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.