The Effect of Cross-Sectional Shape on the Roughness Coefficient

Verryn Aisha Uzhelia; Indratmo Soekarno

Verryn Aisha Uzhelia Master Program of Water Resources Management, Faculty of Civil and Environmental Engineering, Bandung Institute of Technology, MPSDA Building, Jalan Ganesa No. 10, Bandung 40132, West Java, Indonesia
Indratmo Soekarno Faculty of Civil and Environmental Engineering, Bandung Institute of Technology, FTSL Building, Jalan Ganesa No. 10, Bandung 40132, West Java, Indonesia

Keywords: coefficient roughness, cross sectional shape, uniform flow, hydraulic modeling, Manning’s

Abstract

This study examines the effect of cross-sectional shape on the value of the Manning’s roughness coefficient of a channel. The study was conducted using hydraulic laboratory experiment. There were 120 scenarios with 4 different types of sections (90º, 60º, 45º and 35º) and 2 types of channel roughness (coated roughness only at the bottom of the channel and roughness coated with wire mesh on the walls and on the of the channel). To get the coefficient value, it is necessary to get a uniform flow from the experiment. From the experiments results there is a correlation between the average Manning coefficient value of each section with the difference in the shape of the cross section. Then it can be concluded from the experiment that the greatest value of the roughness coefficient is at a cross section of 90° and with the roughness being coated with wire on the walls and bottom of the channel. Chart the explaining the relathionship between the average value of the Manning coefficient obtained with the shape of the cross section, so that the equation is obtained from the graph.Then from the research it can be concluded the cross-sectional shape of the channel greatly influences the roughness coefficient.

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