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ABSTRACT
A tidal bore is a hydraulic jump in translation, propagating upstream as the tide turns to rising and the flood flow advances in a funnel-shaped river mouth under spring tide conditions. This study focused on the unsteady turbulence induced by a breaking tidal bore. Detailed free-surface and velocity measurements were conducted with a high temporal resolution using non-intrusive free-surface measurement probes and acoustic Doppler velocimetry sampled at 200 Hz. The laboratory data were systematically compared with an earlier series of field measurements conducted in the breaking bore of the Sélune River (France). Key findings include the agreement, in terms of dimensionless instantaneous free-surface and velocity data, between laboratory and field observations as well as the existence of a transient recirculation region near the bed.
Acknowledgements
The first writer acknowledges the assistance of his former students Mr Chu Cheng (Adrian) Yao and Pei Yuan Yeo, and Ms Winnie Man, as well as the technical assistance of Ahmed Ibrahim and Jason Van Der Gevel (The University of Queensland). He further thanks Professor Colin Apelt (The University of Queensland) for his valuable suggestions.
Notation
| A | = | cross-section area (m2) |
| A1 | = | inflow cross-section area (m2) |
| A2 | = | conjugate cross-section area (m2) |
| a | = | acceleration (m s–2) |
| amax | = | maximum deceleration (m s–2) |
| B | = | channel width (m) |
| B′ | = | characteristic channel width (m) |
| B1 | = | inflow free-surface width (m) |
| d | = | water depth (m) |
| d1 | = | inflow depth (m) |
| d2 | = | conjugate flow depth (m) |
| 1 | = | inflow Froude number (–) |
| g | = | gravity acceleration (m s–2) |
| hrecirc | = | recirculation height (m) |
| ks | = | equivalent sand roughness height (m) |
| Lrecirc | = | recirculation region length (m) |
| Lroller | = | roller length (m) |
| P | = | pressure (Pa) |
| Rxx | = | normalized auto-correlation function |
| So | = | bed slope (–) |
| Trecirc | = | recirculation region duration (s) |
| Troller | = | breaking roller duration (s) |
| Ttoe | = | roller toe passage time (s) |
| Tvx | = | integral time scale of longitudinal velocity component (s) |
| Tvy | = | integral time scale of transverse velocity component (s) |
| Tvz | = | integral time scale of vertical velocity component (s) |
| t | = | time (s) |
| U | = | bore celerity (m s–1) |
| Vrecirc | = | maximum recirculation velocity (m s–1) |
| Vx | = | longitudinal velocity component (m s–1) |
| Vy | = | transverse velocity component (m s–1) |
| Vz | = | vertical velocity component (m s–1) |
| V1 | = | inflow velocity (m s–1) |
| V2 | = | conjugate flow velocity (m s–1) |
| v | = | velocity fluctuation (m s–1) |
| vx | = | longitudinal velocity fluctuation (m s–1) |
| vy | = | transverse velocity fluctuation (m s–1) |
| vz | = | vertical velocity fluctuation (m s–1) |
| vx′ | = | longitudinal velocity fluctuation root mean square (m s–1) |
| vy′ | = | transverse velocity fluctuation root mean square (m s–1) |
| vz′ | = | vertical velocity fluctuation root mean square (m s–1) |
| x | = | longitudinal distance along the channel bottom (m) |
| y | = | transverse distance (m) |
| z | = | vertical elevation (m) above the invert |
| μ | = | dynamic viscosity (Pa.s) of water |
| θ | = | channel slope |
| ρ | = | water density (m3 s–1) |
| σ | = | surface tension (N m–1) |
| τ | = | time lag (s) |