Turbulent free-surface monitoring with an RGB-D sensor: the hydraulic jump case

Measuring flow depths in free-surface turbulent flows can be challenging due to their fast dynamics and the presence of aeration. This study analyses the suitability of a low-cost sensor, the Intel (R) RealSense (TM) D435 RGB-D camera, for characterization of a highly aerated case study: the hydraulic jump. As with all instrumentation, special care must be taken to ensure accurate measurements. In this case, two different methods to calibrate depth estimations (accounting for set-up and any instrument precision) are presented, both leading to similar results. The main advantage of the presented instrumentation is its capability to measure 3D surfaces with high temporal and spatial resolution. Results are presented primarily in 2D in order to evaluate the flow depth estimation quality of this new technique with 2D data available in literature. The employed sensor showed a similar level of uncertainty as previous, well-established instrumentation for the study of free-surface elevations, amplitudes and frequencies of turbulent fluctuations.