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.

Highlights

  • The LIDAR was able to capture the distinct differences in flow patterns between the two stilling basin designs at high temporal and spatial resolution

  • Comparing LIDAR to traditional in situ measurements reveals that the mean free-surface elevations recorded by the LIDAR were close to the elevation with 50%

  • Void fraction as measured by an air–water conductivity probe and that the 90% percentile of the LIDAR elevations is in close agreement with y90

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Summary

Introduction

In hydraulic engineering, both the interfacial aeration processes, which increase the flow depth and reduce drag, as well as the internal dynamic pressures and forces, are important for the safe design of hydraulic structures including stilling basins [1,2,3]. Physical hydraulic modelling plays a key role in understanding these processes and is used to test and optimize hydraulic structure design before prototype construction. The design of stilling basins with baffle elements has been much less fundamentally researched despite their common use in engineering practice. While standard stilling basin designs exist [3], often these have site- and dam-specific modifications to the baffle elements in the stilling basin that require testing in laboratory-scale physical models

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