Author(s): Rui Li, Laura Montano, Kristen Splinter, Stefan Felder
Keywords: Air-water flows; Free-surface; Hydraulic jump; LIDAR; Stilling basin;
Abstract: Air-water flows are found in fast-flowing natural waters and in human-made water infrastructure such as flow conveyance and energy dissipation systems. Typical examples include hydraulic jumps and high-velocity flows on spillways. Air-water flows are characterized by interactions between air and water phases at various scales as well as strong fluctuations of the free-surface at the air-water interface above the flows. Typical instrumentation for the recording of free-surface elevations and free-surface properties include pointer gauges, wire gauges and acoustic displacement meters as well as indirect flow depth estimates with phase-detection intrusive probes. These instruments provide information at one spatial location at a time. Newly applied instrumentation in air-water flow research is the LIDAR technology which allows the recording of strongly aerated hydraulic phenomena. The LIDAR scans continuously in two dimensions recording the distance between LIDAR and aerated surface and the corresponding angle. New experiments were conducted of fully aerated hydraulic jumps demonstrating the LIDAR’s performance in 3-dimensional complex air-water flows. These tests provided new insights into the effect of filtering of the raw LIDAR data on the mean profiles and the standard deviation of the free-surface, into the repeatability of measurements in terms of free-surface data and jump toe characteristics and into the best positioning of the LIDAR relative to the hydraulic jump. New opportunities of usage of LIDAR technology in air-water flows are discussed including the design of stilling basins and the possibility of prototype measurements.