Start Date

2018 11:15 AM

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

Hydraulic jumps are complex turbulent phenomena characterized by a rapid transition from fast shallow flows to slow deep flows. Strong energy dissipation, air entrainment and large-scale turbulence are some of the key features of hydraulic jumps. The understanding of the free-surface characteristics is limited. Previous experiments have been conducted with pointer gauges, wire gauges and acoustic displacement meters limiting the measurements to a fixed point per sensor along the surface of the hydraulic jump. Recent experiments with a LIDAR measured a continuous and time-varying free-surface profile of an aerated hydraulic jump providing basic statistical free-surface properties. The present study investigated more advanced parameters including the turbulent characteristics of the free-surface in a fully aerated hydraulic jump. Auto- and cross-correlation analyses were performed along the hydraulic jump and the auto- and cross-correlation time scales were calculated. An integration of the maximum correlation coefficients along the hydraulic jump provided the longitudinal free-surface integral turbulent length scales. The comparison with previous studies showed turbulent scales of the same order of magnitude. The turbulent scales in the present study exceeded past results which may be linked with the extended integration range due to the high resolution of measurement points along the hydraulic jump. The present study presented the most spatially detailed description of the turbulent free-surface characteristics in hydraulic jumps to date, including the turbulent free-surface scales in the jump toe region. Further research is needed to identify the effects of instrumentation and raw signal filtering on the free-surface integral scales.

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May 17th, 11:15 AM

LIDAR Measurements of Free-surface Profiles and Turbulent Scales in a Hydraulic Jump

Hydraulic jumps are complex turbulent phenomena characterized by a rapid transition from fast shallow flows to slow deep flows. Strong energy dissipation, air entrainment and large-scale turbulence are some of the key features of hydraulic jumps. The understanding of the free-surface characteristics is limited. Previous experiments have been conducted with pointer gauges, wire gauges and acoustic displacement meters limiting the measurements to a fixed point per sensor along the surface of the hydraulic jump. Recent experiments with a LIDAR measured a continuous and time-varying free-surface profile of an aerated hydraulic jump providing basic statistical free-surface properties. The present study investigated more advanced parameters including the turbulent characteristics of the free-surface in a fully aerated hydraulic jump. Auto- and cross-correlation analyses were performed along the hydraulic jump and the auto- and cross-correlation time scales were calculated. An integration of the maximum correlation coefficients along the hydraulic jump provided the longitudinal free-surface integral turbulent length scales. The comparison with previous studies showed turbulent scales of the same order of magnitude. The turbulent scales in the present study exceeded past results which may be linked with the extended integration range due to the high resolution of measurement points along the hydraulic jump. The present study presented the most spatially detailed description of the turbulent free-surface characteristics in hydraulic jumps to date, including the turbulent free-surface scales in the jump toe region. Further research is needed to identify the effects of instrumentation and raw signal filtering on the free-surface integral scales.