Definition of critical hydrodynamic conditions for sediment motion initiation using optical technique

Abstract

Sediment motion initiation experiments were performed in a glass rectangular channel, with a loose bed in the central part. The main goal is to obtain the critical hydrodynamic characteristics that causes sediment bed motion initiation, for different cohesionless sediment grain sizes. The optical technique of Particle Tracking Velocimetry (PTV) was used in order to determine the critical velocity profiles for sediment initiation of motion. Between the parameters that define this critical velocity profile is the one known as bed rugosity which represents the height of asperities in the bed. For conditions near bed motion initiation experimental velocity profiles were obtained and they allowed us also to define fluctuating velocities u´, v´ and a value of bed rugosity ks related to a representative grain size of the bed. It was shown that obtained critical velocity profiles are in good agreement with other works in the scientific literature provided an appropriate definition of bed rugosity is made.