Settling process and shock wave of cohesive sediment

This research is an experimental study on the settling process. Major topic is focused on the transition between gravitational settling and hindered settling, formation of shock wave, and settling behaviors at different water conditions. An array of Optical Backscatter Sensors (OBS) was used to monitor and track shock waves, and to calculate mass flux. Furthermore, the variation of settling velocity with concentration was obtained by depth-integrated mass conservation equation and position of maximum concentration gradient. The results reveals: Not only interaction between diffusive dispersion and gravitational settling have influence on settling behavior, but also buoyancy and aggregation will affect settling process as salinity changes. Two distinct settling mechanisms were found in this experiment, which are (1) diffusive dispersion dominate process in low sediment concentration and (2) hindered settling dominate process in high sediment concentration cases.