Circular‑crested stepped spillways: semicircular versus quarter‑circular

Articles in Press

Document Type : Original Article

Authors

1 Shahid Chamran University

2 Water Engineering Department, Lorestan University, Khorramabad, Iran

10.22044/jhwe.2026.15216.1040

Abstract

In this study, the hydraulic properties of stepped spillways with semi (SC) and quarter-circular (QC) crest including the discharge coefficient (C_d) and energy dissipation (Ed) were investigated. Results declared that the discharge coefficient (C_d) of QC variate between 1.3 and 1.5 versus the variation of the relative upstream head (h_up⁄R) between 0.3 and 2.5, whereas at the same range of h_up⁄R, the C_dof SC changes between 0.9 and 1.4. For values of h_up⁄R less than one, the C_dof QC is greater than the SC about 50 percent and for more values, their differences gradually reduced to about 10 percent. The reason for the higher Cd is the formation of a negative pressure zone just behind the crest of QC, however, With the gradual increase of the upstream head, the vortex flow in this area is gradually formed and completed, which further reduces the effect of negative pressure zone. Both models can dissipate the energy of flow about 95 and 45 percent and their performances are almost close together.

Keywords

Journal of Hydraulic and Water Engineering

Articles in Press, Accepted Manuscript
Available Online from 02 August 2026

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