Digital Imaging Characterization of the Kinematics of Water-Sediment Interaction

Digital imaging techniques especially geared towards the laboratory characterization of the kinematics of water-sediment interaction are presented. More specifically, the methods proposed apply to the motion of cohesionless spherical particles in transient water flow, with the aim of obtaining both particle velocity and concentration fields from sequences of digital images. A special particle identification algorithm is devised in order to deal with densely packed particles (in contrast to the sparse seedings of tracers used in studies of pure fluid kinematics) and to allow application of digital particle tracking velocimetry (DPTV). A procedure for extracting the concentration field from the knowledge of the discrete particle positions is then detailed. Finally, the various tools are illustrated for the laboratory case of a dambreak wave over a movable bed.