Author(s): Urban Pavlovcic; Gasper Rak; Marko Hocevar; Matija Jazersek

Linked Author(s): GAŠPER RAK, Marko Hočevar

Keywords: Turbulent water flow; Water surface ranging; Laser triangulation; LIDAR

Abstract: Complex hydraulic phenomena in terms of high-speed flow and particularly air flow features are expected as future challenges in hydraulic structure design and the main research topics. Accurate and reliable measurements that provide new information and knowledge about phenomena and processes as well as quality data for calibration and verification of numerical models are crucial. This paper presents the applicability of laser triangulation-based ranging of turbulent water surface with epipolar lines for enhanced spatial resolution. The experiment was conducted on the measuring station of supercritical junction flow, where distinctively 3D, turbulent, two-phase flow occurs. The system for acquisition of transversal profile of the water surface and the range of water surface fluctuation was composed of LIDAR device as light source only, and a high-speed camera with frame rate of 100 kfps. Since the light reflection from the water surface is far more complex compared to the one from a diffuse surface, single point illumination was used. The approach enables application of the epipolar lines in the image post-processing and more efficient distinction between primary reflection, used for water surface ranging, and secondary reflections, which introduce noise in the measurements and consequently increase measuring uncertainty. The results show that parameters of the algorithm, developed for analysis of free-water-surfaces based on the laser triangulation, have almost an order of magnitude smaller influence than the measuring uncertainty of the applied measuring system.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022573

Year: 2022