Density Functions for Entrainment and Deposition Rates of Nonuniform Sediment

Abstract

A model was developed for the prediction of the density functions of entrainment and deposition rates of nonuniform sediment. The model incorporated both statistical and deterministic parameters in its formulation. The model parameters were related to the hydraulic conditions of the flow and the properties of the sediment mixtures using dimensional and multivariate regression analyses. Laboratory experiments were conducted to identify the shape of the density functions for various grain-size fractions and to advance the theoretical formulations of the model. The experiments were also used to validate and estimate the model parameters. The experiments have shown that the density functions of the total entrainment and deposition rates can be approximated quite satisfactorily with the normal distribution curve; however, the density functions of the individual fractions within the sediment mixture depart from the normal distribution curve assuming various distributions. Therefore, the normal distribution equation was modified by introducing a bias-function to adjust the normal distribution curve to fit the distributions of various grain-size fractions within the sediment mixtures. The proposed model approximated satisfactorily the density functions of various grain-size fractions of the sediment mixtures. The deviation between the measured and predicted values was less than 25% for most of the fractions, which confirms the validity of the proposed approach for the prediction of the entrainment and deposition rates of various fractions.