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

Author(s): L. Montano; S. Felder

Linked Author(s): Stefan Felder

Keywords: Hydraulic jumps; LIDAR; Free-surface fluctuations; Jump toe oscillations; Integral turbulent scales

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, wiregaugesandacousticdisplacementmeterslimitingthemeasurementstoafixedpointpersensoralongthesurfaceofthe hydraulicjump. RecentexperimentswithaLIDARmeasuredacontinuousandtime-varyingfree-surfaceprofileof anaerated hydraulicjumpprovidingbasicstatisticalfree-surfaceproperties. Thepresentstudyinvestigatedmoreadvancedparameters 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.


Year: 2018

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