The hydraulic behaviour of filling jets inside navigation locks strongly influences momentum redistribution and the hydrodynamic forces acting on vessels during filling operations. Reduced-order numerical tools such as VUL_SLUIS are commonly used to estimate flow conditions while maintaining limited computational requirements. However, the adopted jet schematization does not always reproduce accurately the downstream evolution of the filling jet. This research investigates turbulent filling jets generated through concentrated openings in navigation lock gates using a combined numerical and experimental approach. Experimental measurements were performed at Flanders Hydraulics using a physical scale model and Particle Tracking Velocimetry techniques. Comparisons with the original VUL_SLUIS implementation revealed discrepancies regarding jet spreading, downstream sinking behaviour, and wall-jet development.