Simultaneous Flow Visualization and Hot-Film Measurements

by Fabi?n L?pez, Univ of Illinois, Urbana, United States,
Yarko Ni?o, Univ of Illinois, Urbana, United States,
Marcelo Garc?a, (A.M.ASCE), Univ of Illinois, Urbana, United States,



Document Type: Proceeding Paper

Part of: Fundamentals and Advancements in Hydraulic Measurements and Experimentation

Abstract:

High-speed video recording of flow visualizations in the near wall region of a turbulent open channel flow was synchronized with hot-film measurements of flow velocity and bed shear stress probes. Analysis of the video images provided information about coherent flow structures associated with the occurrence of ejections near the wall. These structures consisted mainly of oscillating shear layers that were convected in the downstream direction and lifted away from the wall. A visual detection criterion was used to obtain ensemble averages of the velocity and shear stress data during ejection events. Preliminary results obtained from the application of cross-correlation and VITA analyses of the hot-film data were compared with those obtained from the visual analysis, and a general good agreement was found. Further analysis is required to define better criteria to set the parameters required by the VITA algorithm, and also to obtain a better understanding on how wall shear stress and velocity signals relate to the observed coherent structures in the wall region.

Subject Headings: Flow measurement | Flow visualization | Shear stress | Turbulent flow | Stress analysis | Shear walls | Walls

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