Methodology For velocity Field Measurements in Pilot-Scale Stirred Vessels Using 2-D Particle Tracking Velocimetry

Reliable validation of computational fluid dynamics (CFD) simulations of mixing in pilot- and industrialscale vessels is hindered by the scarcity of experimental data, particularly for non-standard geometries and operating conditions. To address this gap, a large-scale Particle Tracking Velocimetry (PTV) measurement methodology was developed, implemented, and critically evaluated. The methodology was applied to a pilot-scale rectangular stirred vessel operated in four configurations, comprising single- and dual-impeller arrangements with either Rushton turbines or pitched blade turbines. The contribution presents a comprehensive description of the experimental setup, including illumination, image acquisition, and seeding strategy, as well as the data processing workflow. Particular attention is given to trajectory reconstruction, validation criteria, and filtering procedures used to remove spurious or physically inconsistent particle trajectories. The resulting velocity and turbulent kinetic energy fields are analyzed with emphasis on their applicability for the validation of Reynolds-Averaged Navier–Stokes simulations. The advantages and limitations of the proposed PTV approach are critically discussed. While the methodology enables spatially resolved velocity measurements over large volumes and captures key flow structures, several shortcomings are identified. These include reduced accuracy of velocity estimates in high-speed regions near impeller discharge, limited reliability of turbulent kinetic energy estimation, and particle settling effects in low-velocity zones. Overall, the study provides practical guidance on the capabilities and limitations of large-scale PTV measurements and offers valuable experimental insights for validating CFD models of mixing in complex, industrially relevant vessels.