Detection of coherent structures associated with bursting events in an open-channel flow by a two-point measuring technique using two laser-Doppler velocimeters

Publisher Website
Google Scholar
Abstract
Large‐scale structures in the wall region of an open‐channel flow were investigated experimentally using the two‐point measuring technique of Komori and Ueda [J. Fluid Mech. 1 5 2, 337 (1985)] which used two laser‐Doppler velocimeters and a conditional (pattern‐) averaging technique. Instantaneous streamwise and vertical velocities were measured simultaneously at two positions—a reference and a movable position—and the spatial and temporal distributions of the fluctuating velocity vectors, Reynolds stress, and turbulent kinetic energy associated with the bursting events were computed using a pattern‐averaging technique based on the variable‐interval time‐averaging method. The results clearly show the time evolution of the coherent structure associated with the bursting events. They also supported the flow visualization results published hitherto, and gave a physical and qualitative basis for them.