Journal of New Approaches in Water Engineering and Environment
Scientific Journal

Impact of Surface Roughness on Discharge Coefficient of Crump Weirs: An Analytical Investigation

Document Type : Original Article

Author

Abbas Parsaie

Department of Water engineering, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran

https://doi.org/10.22034/nawee.2025.510942.1146
Abstract
Weirs are one of the most common hydraulic structures for measuring and controlling water surface elevation and are widely used in hydraulic engineering projects and irrigation and drainage networks. In this paper, the effect of surface roughness on the discharge coefficient (C_d) of the crump weir was studied and compared with that of the crump weir with a smooth surface. For this purpose, laboratory models of crump weirs were considered, whose surfaces were separately coated with sand and gravel of different grain sizes. Analysis of this issue based on dimensional analysis technique explained that the effect of surface roughness on C_d can be evaluated using two dimensionless parameters including the ratio of upstream head to weir height (H⁄P) and the ratio of surface roughness to flow head (k_s⁄H) by simultaneously considering the relative roughness values (k_s⁄P). The results showed that increasing the roughness at low values of upstream head causes the C_d to decrease by about 12.8 percent. However, as the upstream head increases, the effect of k_s⁄P decreases to the point where its impact is negligible.

Keywords

Surface Roughness
Discharge Capacity
Flow Measurement
Concrete Hydraulic Structure
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Journal of New Approaches in Water Engineering and Environment
Volume 4, Issue 2
Special Issue: Guest Editor: Prof. Ozgur Kisi
September 2025
Pages 180-187

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