Al-Qadisiyah Journal for Engineering Sciences

Interface shapes and flow behavior in duct systems under critical and sub-critical flow conditions

Document Type : Research Paper

Authors

Manar A. Abdulrahman 1
Suha I. S. Al-Ali 1
Mohammed Nsaif Abbas 2

1 Department of Mathematics, College of Computer Science and Mathematics, Tikrit University, Tikrit, Iraq

2 Materials Engineering Department, College of Engineering, Mustansiriyah University, Baghdad, Iraq.

10.30772/qjes.2023.143635.1037
Abstract
This article delves into the intricate dynamics of groundwater flow within duct systems, examining both critical and sub-critical flow conditions. Employing mathematical models, sophisticated potential methodologies, numerical simulations, and flow net analysis, the research investigates the behaviour of the phreatic surface under varying flow coefficients m and slope angles θ. Noteworthy discoveries include the significant influence of the flow coefficient on the curvature and deflection of the phreatic surface, with higher m values resulting in steeper slopes. Additionally, the study emphasizes that changes in slope angle θ impact the interface's shape, leading to variations in flow depth. Innovative visualizations incorporating streamlines and velocity potential contours offer insights into flow patterns, recirculation zones, and potential turbulence areas. These critical findings supply essential insights for enhancing environmental strategies, optimizing water resource management, and improving the efficiency of fluid systems. The study emphasises how important it is to use flow net analysis and thoroughly investigate critical and sub-critical flow scenarios in order to handle issues related to groundwater management and sustainability. Stakeholder can enhance their capacity for fluid system optimization by applying these analytical tools, leading to improved environmental outcomes and informed decision-making.

Keywords

Interface shapes
Critical flow
Sub-critical flow
Flow net patterns
Potential contours
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Al-Qadisiyah Journal for Engineering Sciences
Volume 19, Issue 1
Winter 2026
Pages 20-25

  • Receive Date 04 October 2024
  • Revise Date 10 June 2025
  • Accept Date 13 November 2025

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