Analysis of Existing Equations for Calculating the Settling Velocity

M Shiva Shankar,Manish Pandey,Anoop Kumar Shukla

doi:10.3390/w13141987

M Shiva Shankar, Manish Pandey + Show 1 more

Open Access

https://doi.org/10.3390/w13141987

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Abstract

The settling velocity of sediment is one of the essential parameters in studying freshwater reservoirs and transporting sediment in flowing water, mainly when the suspension is the dominant process. Hence, their quantitative measurements are crucial. An error during the prediction of the settling velocity may be increased by a factor of three or more in the estimation of the suspended load transport in the flowing water. Despite its significance, obtaining its real value in situ is practically impossible, and it is usually derived via laboratory tests or anticipated by empirical formulas. Numerous equations are available to calculate the settling velocity of the particle. However, it is exceedingly difficult to choose the best method when giving a specific solution for the same problem. Hence, a review of the existing equations is required. In this study, extensive data on settling velocity is collected from the literature, and previously proposed equations are analysed using graphical and statistical analysis.

Highlights

It occurs when drag force (Fd ) on a sediment particle and the buoyancy is equal to the downward force of gravity (FG ), and the particle stops accelerating and continues falling at a constant velocity that is known as terminal velocity
The data set has been divided into two groups: one is without the shape factor; the second is with the shape factor
It would have been shown to be in good agreement when the shape factor is considered; the results showed low agreement because of the complex equation and insufficient data of all parameters

Summary

Introduction

Previous studies on concentrated suspensions of cohesive sediment flocs [5,16] and non-cohesive sediment particles [5,8] revealed that the three unique mechanisms associated to the existence of the cohesive floc/non-cohesive particle concentration cause the impeded settling characteristics, viz.: (i) generating a return flow and forming a wake; (ii) an increase in the viscosity of the mixture; and (iii) influence of buoyancy. In the present study, several existing equations for settling the velocity of particles were tested for reliability and accuracy using data collected from the literature

Existing Equations for Settling Velocity of Sediments

Data Description

Performances of Existing Equations

Statistical Performance Analysis of Equations

Conclusions