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This technical note introduces a computational fluid dynamics (CFD)-based semiautomated flow rating methodology for hydraulic structures in South Florida. The approach uses the ANSYS Workbench, CFD code FLUENT, IronPython, and Visual Basic programming languages to incorporate the CFD flow data generation process into a semiautomated interactive flow rating platform. The framework includes multiple functions such as overall flow rating status, interactive planning of boundary conditions, automated CFD flow data generation, and hybrid flow rating development using field measurements and CFD-generated flow results. The platform can reduce the complexity of CFD application to flow data generation, optimize central processing unit (CPU) usage, greatly reduce simulation times, and significantly improve flow rating analysis efficiency for the water control structures maintained and operated by the South Florida Water Management District. About 30%–40% simulation time was saved by reducing CPU idle time and automizing geometry adjustments and mesh regeneration. In addition, a 40%–50% reduction in manual work for rating development was achieved with the approach presented. [ABSTRACT FROM AUTHOR]

Water control operations in South Florida often involve the estimation of transition flow at low-head gated spillways for flood control, water supply, and water quality compliance purposes. Approaches to nontransitional flow computation have been extensively investigated, and their accuracy and applicability have been rigorously verified. However, computational algorithms for transitional flows have not generally been accepted by engineering practitioners; arguments even exist with regard to the criteria used to delineate different transitional flow regions. In this study, a generalized discharge rating equation for spillways is proposed that, in contrast to the classical flow-type-separation approaches, can estimate both transitional and nontransitional flow rates. Several verification tests were performed, including a consistency analysis of the proposed equation compared to classical flow equations for different flow conditions and its verification with field and laboratory data. The performance of the proposed equation in transitional flow regions was further evaluated using computational fluid dynamics (CFD) simulations. The discharge estimates agree well with measurements and classical rating equations, with overall computation absolute relative errors of less than 8%. Finally, the inherent limitations of traditional spillway flow-type-separation approaches were analyzed, and the analysis suggested that the generalized equation is a better alternative to overcome the hard-to-define transition thresholds and resolve the discharge discontinuity issue. [ABSTRACT FROM AUTHOR]

A calibrated flow rating equation is often used to determine the flow rate through a hydraulic structure as a convenient and relatively inexpensive method to avoid the difficulties of direct discharge measurements in an open channel. In South Florida, there are hundreds of gated culverts, where accurate and quick estimation of discharge in real time is critical for effective water resource management. Flow through culverts under various conditions and geometries has been studied extensively; however, studies of stage-discharge relationships through gate-controlled culverts are rare and, to the authors' knowledge, not discussed in any open-channel hydraulics books, relevant journals, or design manuals. In this paper, two approaches to improve the stage-discharge relationships at gated culverts are presented, and case studies demonstrate their successful and cost-effective use: first, the application of computational fluid dynamics (CFD) for flow data simulation to supplement field measurements to resolve data limitations and, second, the application of dimensional analysis to improve gated-culvert rating equations. The proposed nondimensional flow rating approach is useful for data planning and consistency testing of hybrid data (field flow data and CFD results) and reduces the flow types occurring at a culvert, making the flow classification less complex while maintaining reasonable rating accuracy within 6% of field flow measurements. [ABSTRACT FROM AUTHOR]