| The measurement of suspended-sediment concentrations, the study of the variability of concentration, quantification of lateral mixing in sediment-laden flows, and the effect of suspended sediment on turbulence are important areas in the study of river hydraulics. Suspended-sediment load is a key indicator for assessing the effect of land-use changes and engineering practices in watercourses. In this dissertation, methods for measuring suspended-sediment concentration are reviewed in detail, resulting in the conclusion that acoustic techniques are the most in need of further use and development. The variability of time series of suspended-sediment concentration data taken at a single point and taken simultaneously at two laterally separated positions in both dune and upper-stage plane beds is examined. Concentration was found to vary greatly in both conditions, with no correlation between simultaneous samples. A new method for calculating the transverse diffusion coefficient using turbulent velocity fluctuations and transverse velocity gradients in a sediment-laden flow is described, with results comparable to those measured in natural rivers and in previous flume studies. Velocity profiles, turbulence intensities, and suspended-sediment concentrations obtained in supercritical conditions in a sediment-laden flow were compared to theory. Velocity profiles showed good agreement with the law of the wall, the magnitude of turbulence intensities was found to depend on the measurement technique, and the Rouse equation was modified to better-fit concentration profiles over flat, mobile beds. Throughout this work, sediment refers to non-cohesive particles in the sandsize fraction, 0.062--2 mm. |
