An innovative method for measuring the three-dimensional water surface morphology of unsteady flow using light detection and ranging technology

High-resolution free-surface elevation measurement is challenging due to the rapid evolution of unsteady flow. In this study, using dam-break flow as an example, the applicability of a low-cost sensor, the Intel® RealSense™ L515 solid-state light detection and ranging (LiDAR) probe, for the free-surface elevation measurement was evaluated. A white inorganic pigment was added to the water to improve the water's laser reflection. A series of dam-break flow experiments were systematically conducted, including asymmetric flow with obstacles in downstream rivers. The results demonstrate that the single-point time-domain process and water surface profile as measured by the LiDAR probe showed good consistency with acoustic displacement meter measurements with uniform correction of the free-surface elevation deviation. The proposed method's advantage is that the unsteady flow's free surface can be obtained with high temporal and spatial resolution; in addition, the volume flow rate and cross-sectional average velocity can be indirectly obtained, thus providing a useful reference for measuring the free surface of unsteady flow under laboratory conditions.