Free-surface mapping of air-water flows in a stilling basin

Abstract

Energy dissipation is an important aspect in the design of hydraulic structures. Stilling basins are a common type of energy dissipator in which a hydraulic jump dissipates large amounts of the flow energy. The energetic processes in hydraulic jumps are closely linked with air entrainment and non-stationary interactions of roller and free-surface motions. Free-surface motions may provide information on the overall performance of a stilling basin. Recently LIDAR technology was pioneered as a method to measure highly aerated hydraulic jumps providing continuous non-intrusive free-surface measurements with high temporal and spatial resolution. In the present study, the LIDAR technology was applied to a hydraulic jump in a laboratory-scale stilling basin. A LIDAR measured the time-varying free-surface features at seven longitudinal and six transverse cross-sections across the stilling basin. A three-dimensional free-surface map was created providing a detailed and integrated free-surface image. Three dimensionalities of free-surface profiles and fluctuations are presented and opportunities of free-surface mapping discussed.