Turbulent Coherent Structures in the Near Wall Region of Open Channel Flows

Abstract

The present work describes an investigation aimed at characterizing turbulent coherent structures in the near wall region of open channel flows. High-speed video recordings (500 Hz) of flow visualizations were synchronized with hot-film measurements of flow velocity and bed shear stress, allowing the acquisition of unprecedented information both visual and quantitative. Analysis of the information allowed the identification as well as the geometric and kinematic characterization of observed structures and the associated flow field. Results reveal the intermittent nature of coherent structures and also their intimate relationship with the mechanism responsible for the transfer of mean flow energy towards large-scale turbulent fluctuations.