Flow Algorithms Development of Compound Culverts by Computational Fluid Dynamics

Flow through South Florida Water Management District's (District) structures is computed based on real time water stages and operating settings measured using site-specific hydraulic rating equations. Typically the rating parameters of flow equations are calibrated and validated with the field flow measurements and the supplemented CFD-simulated flow data if necessary. The District's culverts are mainly functioning on water drainage in urban sewer system, and water quality control in the Everglades area. Among the District's hydraulic structures, there are about 362 culverts including simple culverts and compound culverts. For simple culverts, only barrel(s) with gate(s) installed at one of barrel ends, the rating algorithms have been well developed and widely used. For example, the United States Geological Survey classification system (Bodhanie, 1968) can be easily applied to calculate flow through simple culverts. However, no universal rating algorithms are currently available for flow computation at compound culverts because of their specific inlet structures. The flow through compound culverts might be controlled by inlet structures or by barrel, which depends on the possible combination of water stages and operating settings. In this paper, flows rating of two types of compound culverts have been developed: one is 2-end-gated culvert, barrel with 2 gates installed respectively at each of barrel ends; another is a middle-chamber-gated culvert, a barrel with gate installed at the chamber in the middle of barrel. The studies show that the two new proposed algorithms are able to accurately predict flow for a complex flow structure. The studies also display that CFD can be a very useful tool to study flow algorithm and flow physics for a very complex hydraulic structure.