On determining the geometric and kinematic characteristics of coherent flow structures over a gravel bed: a new approach using combined PLIF‐PIV |
| |
| Authors: | RJ Hardy JL Best DR Parsons GM Keevil |
| |
| Institution: | 1. Department of Geography, Durham University, Science Laboratories, South Road, Durham, DH1 3LE, UK;2. Departments of Geology, Geography and Mechanical Science and Engineering and Ven Te Chow Hydrosystems Laboratory, University of Illinois, 1301 W. Green St., Urbana, Illinois 61801, USA;3. School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK |
| |
| Abstract: | In gravel‐bed rivers, the microtopography of the bed is known to exert a significant influence on the generation of turbulent flow structures that owe their origin to fluid shear generated near the bed. Although field and laboratory measurements have indicated that flows over gravel beds contain a range of coherent flow structures, the kinematic and dynamic properties of these structures are still poorly understood. This paper describes a new experimental methodology to quantify simultaneously both the kinematic and dynamic characteristics of coherent flow structures based upon combined planar laser‐induced fluorescence and particle imaging velocimetry (PLIF‐PIV). The results confirm that the primary generative mechanism of coherent flow structures is at the bed, where merging hairpin vortices form around bed clasts and generate larger‐scale fluid motions that advect downstream. Copyright © 2010 John Wiley & Sons, Ltd. |
| |
| Keywords: | coherent flow structures planar laser‐induced fluorescence particle imaging velocimetry |
|
|
