Assessment of Critical Shear Stress and Threshold Velocity in Shallow Flow with Sand Particles

In this study, the incipient motion of four groups sand, ranging from medium to very coarse particles, was experimentally examined using an acoustic Doppler velocimeter (ADV) in different water depths under hydraulically transitional flow condition. The transport criterion Kramer visual observation method used determine threshold conditions. Some equations for calculating average and near-bed velocities were derived. Results showed that velocity directly proportional both sediment particle size depth. vertical distributions Reynolds shear stress increase bed about 0.1 water’s depth, after performing a damping area, then decrease toward surface. By extending linear portion upper zone area bed, critical stress, number, Shields parameter calculated. located curve, showing no motion. This indicates particles occurred with smaller than estimated diagram region. reason could be related differences between features present experiment those experiments development diagram, including approaches define conditions, accuracy experimental tools estimate characteristics. Therefore, change specifications on which has been based led deviation estimation real at least region sand particles.