Combined effects of mean flow and turbulence on sediment pickup rate

Abstract

This paper aims to explore the combined main flow and turbulence influence on sediment pickup rates by investigating four purposely devised cases, namely, (1) unobstructed flow over a plane bed; (2) unobstructed flow over a rigid‐dune bed; (3) flow obstructed by a horizontal pipe; and (4) flow obstructed by a vertical pipe. The four cases were used to represent typical scenarios of mean flow combined with turbulence of varying intensities. By analyzing the dependence of sediment pickup rate on different combinations of the mean and turbulent flow parameters, a modified densimetric Froude number, incorporating both the bulk‐averaged velocity and maximum root‐mean‐square value of the fluctuating velocity, is found to be reasonably correlated with the measured pickup rates for all the four cases. Consequently, by relating the pickup rate with the dimensionless particle diameter and the modified densimetric Froude number, a generalized equation that predicts the pickup rates under both unobstructed as well as obstructed flow conditions is obtained.