A Reproducible Computational Fluid Dynamics Framework for Sliding Irrigation Gates Built from Public Water-Resources Data: Application to the Rímac Basin, Peru

Irrigation systems in Peru rely on numerous sliding gates for water distribution, yet detailed computational fluid dynamics (CFD) studies built from openly reproducible data remain scarce for Andean irrigation systems. This study develops a three-dimensional CFD model, parameterized entirely from public records of Peru’s National Water Resources Authority (ANA) observatory (SNIRH), to characterize the discharge behavior of a typified sliding irrigation gate. Six steady-state Reynolds-Averaged Navier-Stokes (RANS, k-ε) simulations were performed in OpenFOAM across gate apertures of 25-95% and discharges of 3.0-6.0 m³/s, referenced to the public design discharge of the Carapongo intake structure on the Rímac River (5.0 m³/s). A five-block hexahedral mesh (31,200-68,160 cells) was verified with checkMesh and confirmed mesh-independent, with the discharge coefficient (Cd) changing by less than 0.01% between the working mesh (44,400 cells) and a 4.5-times finer mesh (199,680 cells). At the most-throttled aperture (25%), the CFD-derived Cd (0.665) agreed with classical hydraulic literature formulas to within 2-9%. At fixed 50% aperture, Cd proved invariant with discharge to within 0.02% across a two-times flow-rate range, confirming the internal consistency of the numerical model. Across the full aperture sweep, Cd increased from 0.665 at 25% aperture to 0.739 at 50% aperture, characterizing the operating range relevant to fine flow regulation in irrigation practice. This fully public, reproducible CFD framework, spanning data acquisition, mesh generation, simulation, and validation, offers a transferable methodology for characterizing sliding-gate hydraulics in Peru and other data-constrained regions lacking public engineering drawings or rating curves.