Assessing the Hydraulic Performance of Innovative Circular Spillway Inlet Shapes

Anani E. Anani1, *, Anas M. El-Molla1, Amir M. Mobasher1, Mamdouh A. Dardeer1, Ahmed H. Mahmoud1
1 Civil Department, Faculty of Engineering, Al-Azhar University, Cairo, Egypt

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© 2023 Anani et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Civil Department, Faculty of Engineering, Al-Azhar University, Cairo, Egypt; E-mail:



In terms of the significance of spillways on dams' stability, this research was initiated to propose innovative spillway inlet shapes with the CS “Circular Spillway” and assess their hydraulic performance experimentally. Primarily, previous studies in the field of CSs were accumulated and investigated. Innovative spillway shapes with triangular or rectangular edge notches were proposed.


A model was constructed, and 140 experiments were carried out on the proposed spillway, where the model was initially calibrated. The entrance shapes were replaced, and their impact on the COD “Coefficient of Discharge” was determined. For comparison purposes, a reference case without notches was investigated. Measurements were undertaken; analyzed, and 2 empirical eqs. were established.


The results flagged that the most reasonable inlet shape was the triangular shape, which improved COD by 143.1% relative to the reference case. Accordingly, the research acknowledged the triangular notches rather than rectangular ones.


Consequently, the research recommended their implementation. Moreover, the research accredited the established eqs. to assist engineers during spillway design.

Keywords: Circular apillway, Coefficient of discharge, Cs-triangular, Notch-rectangular, Notch spillway crest, Reservoirs of dams.