Flow profile calibration measurement using PIV, limited to the region of possible overlap with the LPT measurements, which are conducted within a ~1 cm³ region centred within the vessel with an accuracy of ~0.5 cm. Top panel: measured mean velocity (blue dots), and parabolic fit (purple line), limited to the central 2 cm of the flow vessel. Errorbars represent the standard deviation of the time-series PIV data. Bottom panel: calculation of the relative difference invelocity from the maximum centre-line velocity. The shaded region represents the uncertainty range due to error bars in the top panel.