Reimagining flow measurement with CFD: accuracy for non-standard hydraulic structures

Accurate flow measurement is essential for process control, billing, regulatory compliance, and the realization of digital twins in water utilities. However, many legacy open-channel devices, such as flumes and weirs, deviate from idealized designs, leading to significant measurement errors. While traditional field calibration is accurate, it is often costly, labor-intensive, and limited to specific flow conditions. This study presents a high-fidelity framework using Computational Fluid Dynamics (CFD) and Lidar-derived ‘as-built’ geometries to re-calibrate non-standard structures at two facilities: a modified Parshall flume in Colorado and a rectangular weir in California. High-resolution simulations resolved complex velocity non-uniformity and kinetic energy gradients, identifying maximum deviations of 25% and 21%, respectively. CFD-derived rating curves stabilized depth-discharge relationships to within ±2%, reducing operational errors to a manageable 2–10% range. This work establishes a physics-based baseline for event-driven Digital Twins, demonstrating CFD’s role in enabling adaptive, cost-effective flow monitoring.