Scale effects in experimental modelling of nappe flows

Scale effects in experimental modelling of nappe flows

This project investigates the scale effects in the experimental modeling of impact pressures induced by free-surface flows on dissipation basins downstream of spillway dams—structures essential to dam safety and overflow risk mitigation. With climate change increasing the frequency and intensity of spillway use, ensuring safe and effective operation is crucial, particularly given aging infrastructure and future climate uncertainties. Current knowledge on pressures exerted by overflow on dissipation structures is limited, especially concerning scale effects in physical modeling. This doctoral research aims to quantify and characterize these effects to improve the accuracy of impact pressure predictions for free-surface flows.

The research centres on physical modeling of a single waterfall at different geometric scales using a series of model setups, including an existing 1-meter model and facilities for creating falls of around 3 meters. Pressures induced by free-surface flow on the dissipation basin floor will be measured with piezoresistive sensors at a sampling frequency high enough to capture pressure fluctuations. High-frequency, long-duration data acquisition will enable detailed statistical analysis of temporal pressure distribution, allowing precise characterization of scale effects. Beyond scale variation, the tests will systematically examine the influence of water cushion thickness in the dissipation basin, and airflow rate will be artificially adjusted to evaluate the impact of entrained air. Ultimately, this project aims to develop a reliable extrapolation method to translate model results to prototype applications, enhancing the design and safety of real-world spillway dissipation systems.