A Flow-Bench-Supported, Configuration-Additive CFD Framework for Decoupling the Hydraulic Loss and Regulator Load of an Integrated Irrigation Hydrant: A Comparison of the Conventional and Redesigned Bodies

In pressurized irrigation networks, water-intake hydrants combine flow regulation, shutoff and metering in a single cast body, and the resulting coupled resistance obscures how much each function costs. The conventional body of a DN100 (nominal diameter 100 mm) hydrant and a redesigned production variant were solved with an incompressible Reynolds-averaged Navier–Stokes (RANS) model in three functional configurations (bare body, +regulator, +metering line) at five inlet velocities (1–5 m s−1, Re ≈ 1.0 × 105–5.0 × 105). The mesh was selected after a four-level refinement study, and the quarter-symmetry assumption was verified against two full-domain calculations with both symmetry planes removed: the reduced domain costs 1.0% in pressure drop, and the transverse forces and the net moment on the regulator vanish in the time mean, leaving the axial thrust as the only physically meaningful regulator load. The redesigned body lowers the bare-body loss coefficient by 30.9% and raises Kv by 20.3%. Adding the regulator removes that advantage—ξ becomes 3.0% worse and the full-device axial thrust 11.9% higher—and adding the metering line widens the gap to 37.0% in loss and 60.8% in thrust. Loss and mechanical load therefore reverse sign together at integration, so a body improvement demonstrated in isolation cannot be assumed to survive assembly. The decomposition also acted as a consistency check: a negative metering-line increment in the conventional device, impossible for a passive addition, was traced to a 23.5% passage enlargement present in the supplied full-device geometry rather than to the flow. Wall data give a minimum static pressure of 0.20 bar and a local cavitation number of 1.39, a margin five times narrower than a lumped estimate suggests. Flow-bench measurements on the finished product provide an independent order-of-magnitude reference rather than a validation. The configuration-additive decomposition and the axial-thrust indicator together form an evaluation approach transferable to other devices that combine sub-functions in one body, subject to confirmation on further geometries and Reynolds ranges.