https://orcid.org/0000-0003-2362-7239
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Abstract
Hydraulic jumps are characterized by three-dimensional motions, air entrainment and energy dissipation. While extensive air–water flow research has been conducted for classical hydraulic jumps, the air–water flow properties in hydraulic jumps on slopes remain widely unexplored. New air–water flow experiments were conducted of Type B and D jumps for slopes of 1.25°, 2.5° and 5°. Comparative analyses of the sloped jumps with classical hydraulic jumps for the same Froude and Reynolds numbers showed that hydraulic jumps on slopes were more stable. Close similarities in aeration and energy dissipation performances were found between the classical hydraulic jumps and Type B jumps while Type D jumps showed lower energy dissipation efficiency and aeration. Combining the observations of flow aeration and stability, the present results suggested that a Type B jump may be an optimum hydraulic jump achieving large energy dissipation while providing increased jump toe stability.
Notation
| C | = | void fraction (–) |
| Cmax | = | maximum void fraction (–) |
| d1 | = | upstream conjugate depth (m) |
| d2 | = | downstream conjugate depth (m) |
| F | = | bubble count rate (Hz) |
| Fcl | = | cluster count rate (Hz) |
| Fmax | = | maximum bubble count rate in the shear region (Hz) |
| Ftoe | = | jump toe frequency (Hz) |
| F1 | = | inflow Froude number (–) |
| H1 | = | total upstream head (m) |
| H2 | = | total downstream head (m) |
| q | = | flow rate per unit width (m2 s−1) |
| Re | = | Reynolds number (–) |
| tch | = | chord time (s) |
| tch,mean | = | time-averaged chord time (s) |
| V | = | interfacial velocity (m s−1) |
| V1 | = | inflow velocity (m s−1) |
| W | = | channel width (m) |
| x | = | distance from the jump toe (m) |
| Xtoe | = | jump toe position (m) |
| Xtoe′ | = | standard deviation of the jump toe oscillations (m) |
| y | = | elevation above channel bed (m) |
| y′ | = | standard deviation of the free-surface fluctuations (m) |
| z1 | = | vertical distance from the horizontal channel bed to the jump toe (m) |
| η | = | efficiency of energy dissipation (–) |
| θ | = | channel slope (–) |
Acknowledgements
The authors thank Rob Jenkins and Larry Paice (WRL, UNSW) for their technical assistance and Rui Li (WRL, UNSW) for her assistance with collecting and processing of the LIDAR data.
ORCID
Laura Montano http://orcid.org/0000-0003-2362-7239
Stefan Felder http://orcid.org/0000-0003-1079-6658