LIDAR Scanning as an Advanced Technology in Physical Hydraulic Modelling: The Stilling Basin Example

Abstract

In hydraulic engineering, stilling basin design is traditionally carried out using physical models, conducting visual flow observations as well as point-source measurements of pressure, flow depth, and velocity at locations of design relevance. Point measurements often fail to capture the strongly varying three-dimensionality of the flows within the stilling basin that are important for the best possible design of the structure. This study introduced fixed scanning 2D LIDAR technology for laboratory-scale physical hydraulic modelling of stilling basins. The free-surface motions were successfully captured along both longitudinal and transverse directions, providing a detailed free-surface map. LIDAR-derived free-surface elevations were compared with typical point-source measurements using air–water conductivity probes, showing that the elevations measured with LIDAR consistently corresponded to locations of strongest air–water flow interactions at local void fractions of approximately 50%. The comparison of LIDAR-derived free-surface elevations with static and dynamic pressure sensors confirmed differences between the two measurement devices in the most energetic parts of the jump roller. The present study demonstrates that LIDAR technology can play an important role in physical hydraulic modelling, enabling design improvement through detailed free-surface characterization of complex air–water flow motions beyond the current practice of point measurements and visual flow observations.

A Review on Methods for Measurement of Free Water Surface

“…Because of its speed, accuracy, and efficiency, airborne and terrestrial LIDAR scanning is increasingly replacing traditional geodetic methods of measurement [ 33 , 34 ]; it facilitates the capture of data required for archaeological research [ 35 , 36 ] and detailed reconstruction of buildings [ 37 , 38 ], and with the classification of raw point clouds with enhanced algorithms, the data can be used in forestry [ 39 , 40 , 41 ], geomorphology [ 42 ], laser bathymetry [ 43 ], etc. LIDAR-acquired topography data are also widely used in hydroengineering, particularly for preparing geometry in physical and numerical modeling [ 44 , 45 , 46 , 47 ], with a notion that water bodies usually greatly affect the performance and accuracy of measurements. In these applications, water represents a layer that must be penetrated by the laser beam to obtain the topography of an underlying solid surface.…”

“…Laser scanning also provided free-surface features in fully aerated flows over a stepped spillway and down a laboratory still basin at high spatial and temporal resolutions [ 19 , 46 ]. Both studies highlight the applicability and capability of LIDAR to provide information in the field of physical modelling and to provide data with improved spatial and temporal resolution, enabling design improvement through detailed characterization of the free surface of complex air–water flow motion, as well as other advantages over traditional point measurements in situ.…”