Free-Surface Maps and Profiles of Hydraulic Jumps Measured with a Depth Camera

Abstract Hydraulic jumps are natural energy dissipation mechanisms characterized by highly complex phenomena such as turbulence, air entrainment, and bubble transport. Recent technological advances have facilitated the increasing use of nonintrusive instruments for measuring free-surface profiles and fluctuations in aerated flows. In this experimental study, five different hydraulic jumps with Froude numbers ranging from 4.5 to 9.1 and Reynolds numbers from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="9.2 times 10 Superscript 4" display="inline" overflow="scroll"> <mml:mn>9.1</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>4</mml:mn> </mml:msup> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="1.2 times 10 Superscript 5" display="inline" overflow="scroll"> <mml:mn>1.2</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>5</mml:mn> </mml:msup> </mml:math> were investigated in a 1-m-wide horizontal flume. A depth camera (Intel RealSense D435if) was used to acquire three-dimensional free-surface data, enabling the reconstruction of the three-dimensional free-surface geometry, allowing to extract different longitudinal and transverse sections. The camera-based results were compared against air fraction profiles obtained from a single-tip conductivity probe with a 0.20-mm copper electrode, previously tested in a calibration bench. Close agreement between both methods confirmed that the depth camera accurately captured the aerated free-surface fluctuations and free-surface profiles of the hydraulic jumps. The dominant free-surface fluctuation frequencies in the longitudinal direction ranged from 0.35 to 3.0 Hz, aligning well with previous hydraulic jump research. Overall, the use of a depth camera offers a reliable, economic, and nonintrusive approach for three-dimensional free-surface characterization in highly aerated, turbulent flows.