Introduction: This research delves into the intricate hydraulic dynamics of open channel flows, with a specific focus on the significant impact exerted by a central baffle structure when implemented within channels of varying geometric cross-sections—namely, simple and composite rectangular configurations. The overarching objective of this study is to meticulously evaluate and quantitatively compare how these distinct channel geometries, in conjunction with the central baffle, influence critical flow parameters. These include, but are not limited to, flow velocity, shear stress distribution, drag and lift forces acting on the structure, the rate of energy dissipation within the channel, and the detailed profiles of velocity and flow depth. A profound understanding of these interactions is not merely academic; it is fundamentally essential for the efficient design of hydraulic structures, the optimization of open channel conveyance systems, and the accurate prediction of various flow-related phenomena, such as erosion, sediment transport, and structural stability. Recognizing the complexity inherent in such flows, particularly the generation of vortices, turbulence, and free surface instabilities around obstructions, this investigation aims to provide a comprehensive elucidation of how the synergistic interplay between channel geometry and baffle design dictates overall flow behavior. The ultimate goal is to identify optimal configurations that enhance hydraulic performance and operational efficiency for a range of practical engineering applications.
Methodology: The methodological framework of this research is strategically designed as a robust hybrid approach, integrating advanced numerical modeling techniques with rigorous experimental validation. For the numerical simulations, the widely recognized and powerful OpenFOAM software suite was employed. Specifically, the two-phase flow solver, commonly known as interFOAM, was selected for its proven efficacy in handling free surface flows and air-water interfaces. Complementing this, the k–ω SST turbulence model was adopted. This model offers a superior balance between accuracy and computational efficiency, particularly in predicting flow separation and adverse pressure gradients, which are characteristic of flows around bluff bodies like baffles. The geometric configurations under scrutiny comprised two distinct channel designs: a standard, simple rectangular channel and a more complex channel featuring a composite rectangular cross-section. In both channel types, a centrally positioned baffle structure was incorporated. Standard hydraulic boundary conditions were applied, including a specified inflow discharge rate at the channel inlet and an atmospheric pressure condition at the outlet to simulate open channel flow. After the computational fluid dynamics (CFD) simulations were executed and transient flow fields were established, the obtained numerical results—encompassing velocity profiles, flow depth variations, and shear stress distributions—were subjected to a stringent comparison against meticulously collected experimental data. The accuracy and reliability of the numerical model were quantitatively assessed using established statistical metrics such as absolute error, normalized mean squared error (NRMSE), and the correlation coefficient R2, thereby ensuring the fidelity of the simulation in representing the real-world hydraulic phenomena.
Results and Discussion: The detailed analysis of the simulation outcomes yielded several key findings regarding the distinct hydraulic responses observed in the simple versus composite channel configurations. In the simple rectangular channel, the presence of the central baffle was found to induce significant flow perturbations. These included the generation of highly turbulent flow regimes, the formation of unstable vortex structures downstream of the baffle, and a notable increase in energy losses throughout the channel reach. Furthermore, the drag and lift forces exerted on the baffle exhibited considerable fluctuations, indicative of unsteady flow conditions. The shear stress distribution along the channel bed and walls was also found to be spatially variable and relatively elevated in this configuration.
In stark contrast, the composite rectangular channel, when equipped with the same central baffle, presented a markedly different flow behavior. A primary observation was the substantial reduction in the drag force acting on the baffle, narrowing its range significantly (from a broad spectrum of 1.198 to 12.702 in the simple channel to a more constrained range of 4.99 to 6.53). Concurrently, the shear stress along the channel bed experienced a dramatic decrease, approaching near-zero values in certain regions. This indicates a substantial dampening of turbulent energy near the boundaries. However, this enhanced flow control came with a trade-off: the lift forces acting on the baffle became considerably more pronounced and exhibited greater oscillatory behavior, spanning a wider range from -9.035 to +10.316.
A critical parameter, the energy dissipation rate, revealed a significant difference between the two setups. The composite channel exhibited a substantially higher energy dissipation rate, reaching approximately 75% of the total incoming flow energy, compared to roughly 33% in the simple channel. This heightened dissipation in the composite channel is primarily attributed to the synergistic interaction between the modified cross-section and the baffle, which effectively promotes the formation and shedding of large-scale vortices, thereby consuming kinetic energy more rapidly.
Crucially, the rigorous validation of the numerical model against experimental data provided strong evidence for its predictive capabilities. The model achieved a high degree of accuracy, evidenced by a low mean error (3.81% for the simple channel and 2.35% for the composite channel), a low normalized mean squared error (NRMSE) of 0.076 and 0.083, respectively, and an exceptionally high correlation coefficient ® of 0.99. These metrics collectively affirm the model’s reliability in accurately simulating the complex flow phenomena observed in both channel configurations.
Conclusion: This comprehensive study successfully elucidated the distinct hydraulic impacts of channel geometry (simple versus composite rectangular) when integrated with a central baffle structure in open channels. The composite channel configuration demonstrated a superior capacity for flow management, characterized by a significant reduction in drag forces and a more controlled dissipation of energy, albeit with increased oscillatory lift forces compared to the simple channel. The high fidelity of the OpenFOAM numerical model, validated against experimental data, underscores its utility for simulating such complex flows. These findings collectively highlight the significant potential of employing composite channel geometries in conjunction with appropriate flow-control structures like baffles to optimize the design and operational efficiency of hydraulic systems.