LIDAR measurements of air-water flows in a creek

Abstract

Accurate measurements of the free-surface of air-water flows are a challenge due to the strong entrainment and entrapment of air caused by the flow’s violent nature and large spatial and temporal variability. Best practice air-water flow instrumentation such as phase-detection intrusive probes only take measurements at fixed locations. The use of such instrumentation at prototype scale also remains a challenge, while proto type data are needed for validation of laboratory-developed design approaches, as well as physical and numerical models. Herein, remote sensing technology such as video cameras and LIDAR technology provide new opportunities for safe and reliable collection of air-water flow data in the field, as well as more detailed spatial and temporal observations at laboratory scale that can improve fundamental understanding and engineering design. With previous advancements in the use of LIDAR technology for free-surface observations in a range of air-water flow phenomena at laboratory scale, this paper explores LIDAR technology in field measurements at a low-head weir and a river rapid in a creek. The LIDAR was able to capture the strong free-surface motions in the aerated flows and was able to produce mean free-surface profiles in aerated and non-aerated flow regions. Combining several transects of LIDAR measurements produced 3D channel bed and free surface maps that were consistent with the observed flow patterns. The successful field measurements confirmed the suitability of LIDAR technology for continuous free-surface measurements in field conditions paving the way for LIDAR applications at larger hydraulic structures