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Abstract of the Article

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Comparison Between Settling Velocity Equations

Authors:
[ Seyed Morteza Sadat Helbar ] - M.S Student of Hydraulic Structures of Water & Soil Engineering Faculty University of Tehran
[ Ebrahim Amiri ] - Assistant Professor of Water & Soil Engineering Faculty University of Tehran

Abstract:

Settling velocity of natural particles plays an important role in determination of settling basin dimension in water conveyance network. Not accurate estimations of this parameter leads to undergoing unnecessary construction expense or damages due to sediment transport into the networks. In this study, equations which are developed and published from 1933 to 2005 are collected. Finally 15 equations are chosen out of this collection and are compared together as 22 separated equations. Affecting parameters are the same in all above called studies. So, in order to facilitate the comparison, they are arranged as a combination of dimensionless numbers, Reynolds number (Re) and effective diameter (Dgr). Limitation of application range of each equation are considered. Equation with not enough accuracy, witch have a considerable difference with others (25%), are eliminated and mean settling velocity for each diameter is measured, separately. Finally a graph is developed that shows mean settling velocities measured from different equation versus related diameter. This graph is in consistant with experimental data of same researchers, ( e.g. Hallermeier, 1981 ) . thus this graph can be used for prediction of settling velocity.

Keywords:

Settling velocity , Sediment , Settling basin , Natural particle