Vertical concentration profile of nonuniform sediment

A new formula for the concentration profile of nonuniform sediment is derived using the diffusion differential equation with equilibrium bed concentration. The interaction coefficient for nonuniform sediment particles as a function of both relative diameter and geometric standard deviation of nonuniform sediment is taken into account in the settling velocity. The diffusion coefficient is obtained from the logarithmic velocity profile. This new formula possesses several advantages as follows: (1) avoids theoretical defect of the Rouse formula, which states that the sediment concentration is infinite at the bottom and zero at the water surface. (2) suitable for an arbitrary fraction of nonuniform sediment, and (3) easy to apply with a simple form. The formula yields less difference among concentration profiles for various particles than that for uniform sediment and reveals the law for fractional concentration distribution of nonuniform sediment. The calculated concentration agrees well with the measured data from the Yangtze River. (C) 2020 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research. Published by Elsevier B.V. All rights reserved.

Automated summary

The new formula for the concentration profile of nonuniform sediment accounts for the relative diameter and geometric standard deviation of sediment particles, avoids the theoretical defect of the Rouse formula, is suitable for any fraction of nonuniform sediment, and is easy to apply. It reveals the law for fractional concentration distribution of nonuniform sediment and shows good agreement with measured data from the Yangtze River.