Author(s): Fereshteh Bagherimiyab; Ulrich Lemmin
Linked Author(s): Ulrich Lemmin
Keywords: No Keywords
Abstract: Understanding unsteady sediment-laden water flows in rivers and open channels and the resultant sediment transport is important because of their impact on river dynamics and the ecological system. In the present study, turbulent unsteady (accelerating), open-channel flow over a movable (but not moving) coarse gravel bed (D50 = 5.5 mm) was investigated. In the hydrograph, the duration of the unsteady flow range was 30 s. Detailed, quasi-instantaneous velocity profiles resolving turbulence scales were measured using an Acoustic Doppler Velocity Profiler (ADVP). They were repeated 20 times. The unsteady flow was segmented into more than 100 time slices for the analysis. During the unsteady flow, the profiles of mean longitudinal velocity have a logarithmic shape in the inner layer. Bottom shear velocity increased more rapidly during the initial phase of the unsteady range than the mean velocity. Reynolds stress profiles throughout most of the unsteady flow were reasonably smooth, but become noisy in the final phase.
Year: 2009