Pressure, turbulence and two-phase flow measurements in hydraulic jumps

Wang, Hang, Murzyn, Frédéric and Chanson, Hubert (2014) Pressure, turbulence and two-phase flow measurements in hydraulic jumps. Hydraulic Model Report CH CH95/14, School of Civil Engineering, The University of Queensland.

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Author Wang, Hang
Murzyn, Frédéric
Chanson, Hubert
Title Pressure, turbulence and two-phase flow measurements in hydraulic jumps
School, Department or Centre School of Civil Engineering
Institution The University of Queensland
Open Access Status Other
Report Number CH95/14
Series Hydraulic Model Report CH
Publication date 2014
Start page 1
End page 154
Total pages 156
Publisher School of Civil Engineering, The University of Queensland
Language eng
Formatted Abstract/Summary
A hydraulic jump takes place when a shallow high-speed free-surface flow impinges into a deeper slower flow region. Besides a sudden increase in depth, the most significant flow features include large turbulence seen both at the free-surface and inside the jump roller, as well as substantial air entrainment into the roller. The flow hydrodynamics is extremely complicated because of the interactions between a large number of turbulent two-phase flow properties with a broad range of relevant length and time scales. This report presents a detailed experimental study of the hydraulic jump. The total pressure field was measured in a series of vertical cross sections conducted in the roller, using a miniature probe. The air-water flow properties were measured simultaneously at the same location with a dual-tip phase-detection probe. The instantaneous free surface positions were scanned non-intrusively with a series of acoustic displacement meters, including immediately above the total pressure and air-water flow measurement location. The investigations were characterised by partially developed inflow conditions with Froude numbers ranging from 3.8 to 8.5 corresponding to Reynolds numbers between 3.5×104 and 8.0×104. The time-averaged free surface and air-water flow properties showed good agreement with previous findings. The free-surface fluctuation amplitude and frequency were larger in the first half roller close to the toe, than in the second half of roller. The longitudinal jump toe oscillations were associated with an instantaneous deformation of the roller free-surface. The vertical distributions of time-averaged air-water flow properties showed two main air-water flow regions: namely the turbulent shear layer for y < y* and a recirculation region above. The total pressure measurement was validated in the shear layer through a comparison with theoretical calculations based upon the measured two-phase flow data. The results showed that the pressure distribution was quasi-hydrostatic in the roller taking into account the flow aeration. In the shear layer, the vertical profiles of mean pressure and pressure fluctuations exhibited some marked maxima. The magnitudes of mean and fluctuation maxima increased with increasing Froude numbers and decreased with increasing distance from the jump toe for a given Froude number. Some cross-correlation analyses were performed between any two instantaneous signals of the horizontal jump toe oscillations, vertical free surface fluctuations, instantaneous total pressure and instantaneous void fraction. Some marked maximum correlation coefficients indicated the co-variation relationships. The simultaneous sampling of instantaneous free-surface, total pressure and void fraction fluctuations indicated two different sub-regions in the shear layer: the main shear layer and the lower shear layer next to the invert. The characteristic differences of each sub-region were discussed in terms of the two-phase flow and turbulence properties.
Keyword Hydraulic jump
Free-surface measurements
Total pressure measurements
Two-phase flow measurement
Interactions between turbulence and air entrainment
Additional Notes The report is open access. The full bibliographic details are: WANG, H, MURZYN, F., and D., CHANSON, H. (2014). "Pressure, Turbulence and Two-Phase Flow Measurements in Hydraulic Jumps." Hydraulic Model Report No. CH95/14, School of Civil Engineering, The University of Queensland, Brisbane, Australia, 154 pages (ISBN 9781742721064).

Document type: Department Technical Report
Collection: School of Civil Engineering Publications
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Created: Mon, 05 May 2014, 07:01:37 EST by Hubert Chanson on behalf of School of Civil Engineering