Karim R. GubashiThis email address is being protected from spambots. You need JavaScript enabled to view it., Saad Mulahasan, and Haider Ali Al-Mussawy
Department of Water Resources Engineering, College of Engineering, Mustansiriyah University, Baghdad, 10047, Iraq.
Received: October 14, 2025 Accepted: January 3, 2026 Publication Date: February 14, 2026
Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.
In this study an experimental work was conducted to characterize the hydraulic properties of flow through a wall containing rectangular vertical openings under both partially and fully submerged conditions. Laboratory tests were carried out at the hydraulics and hydrology laboratory at Mustansiriyah University in a tilting recirculating flume with controlled opening configurations and flow rates. Dimensional analysis was performed to derive the governing parameters, and in contrast, empirical correlations were determined through regression analysis. It was found that the discharge coefficients are highly dependent on submergence, head loss ratio, and Froude number. For partially submergence, the discharge coefficient for partially submerged outlets increases with flow and Froude number, while for fully submerged outlets, discharge coefficients decrease with increasing discharge, but positively with Froude number. The head loss was dependent on the flow discharge and showed a direct proportion which confirms the importance of dissipation of energy effects. With strong coefficients of determination, the empirical equations that are produced are accurate and dependable for hydrological design predictive analysis. The improvement of rivers, sluice gates, spillways, and drainage systems is made possible by these studies, which also help to clarify the flow patterns through rectangular apertures.
Keywords: orifice flow, fully and partially submerged outlet, discharge coefficient, experiments, head loss.
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