Low-cost surface particle image velocimetry for hydraulic model studies

An application of a large-scale PIV technique on a scaled hydraulic model of a hydroelectric powerplant was performed. A detailed study regarding the relationship between the tracer size (paper confetti) and the spatial resolution settings of the statistical correlation program was carried out. The validated parameters and operational procedures were used for the flow characterization in two areas: the spillway approaching area and the tailrace channel. The larger tracer (10 mm diameter) performed better. The manual particle seeding showed to produce negative bias effects in velocity measurements, due to particle agglomeration. The low-cost measurements resulted in velocity field information of a resurgence flow in the tailrace channel measured with only 10 pairs of images. The study showed, as a proof of concept, that hydraulic model studies could easily be complemented with LS-PIV techniques providing spatial and temporal variations of velocity fields for flow analysis with advantages against intrusive point-based measurement techniques.