Abstract
In this paper the bed erosion dynamics during flushing events are analyzed. The hydraulic structures studied are gated weirs, which are largely utilized in run-of-the-river hydroelectric plants. The investigation is performed utilizing an experimental scale model. The bed material adopted in the model consists of light plastic material to reproduce at laboratory scale, the sediment transport modality by suspension. The experiments show that exists a strong dependency between the eroded volume and the flow rate. In particular the extension of the scour area, both in the upstream and in lateral direction, is analyzed and show different velocity propagation during flushing operations. In order to explain the mechanism of erosion process, the velocity field (strongly tridimensional) is measured with 3D Micro Acoustic Doppler Velocimeter and Particle Tracking Velocimetry technique. In particular, the formation of horizontal and vertical axis recirculation currents implicate the scour extension and the lateral erosion process.