Diffusion of Sediment in Developing Flow

The suspension of sediment particles by turbulent eddy diffusion in a nonuniform flow region was studied, using the convective-diffusion equation as a mathematical model. A simplified form of the equation, for which mixing characteristics and flow velocities was assumed uniform, was found to accurately describe the sediment concentration profiles which had been measured in a 24-ft-long flume. Although diffusivities in the nonuniform region tended towards uniformity with downstream distance, the vertical diffusive transport rate was related to depth as a power law function. Measured diffusion coefficients were found to depend on the relative roughness of the mobile bed.