Hubert Chanson

Turbulence and energy dissipation on stepped spillways

In recent years, the design floods of a number of dams were re-evaluated and the revised flows were often larger than those used for the original designs. In many cases, occurrence of the revised design floods would result in dam overtopping because of the insufficient storage and spillway capacity of the existing reservoir. A number of overtopping protection systems were developed for embankments and earthfill dams. These include concrete overtopping protection systems, timber cribs, sheet-piles, riprap and gabions, reinforced earth, Minimum Energy Loss weirs, and the precast concrete block protection systems developed by the Russian engineers (http://www.uq.edu.au/~e2hchans/over_st.html). Recent studies demonstrated a strong correlation between air entrainment, stepped chute hydrodynamics and turbulence. The findings imply that the rate of energy dissipation on stepped spillways might be drastically affected by the interactions between entrained air and flow turbulence.

Tidal bore processes in estuaries

When a river mouth has a flat, converging shape and when the tidal range exceeds 6 to 9 m, the river may experience a tidal bore (http://www.uq.edu.au/~e2hchans/tid_bore.html). A tidal bore is basically a series of waves propagating upstream as the tidal flow turns to rising. It is a positive surge. As the surge progresses inland, the river flow is reversed behind it. The best historically documented tidal bores are probably those of the Seine river (France) and Qiantang river (China). The mascaret of the Seine river was documented first during the 7th and 9th centuries AD, and in writings from the 11th to 16th centuries (http://www.uq.edu.au/%7Ee2hchans/mascaret.html). It was locally known as "la Barre". The Qiantang river bore, also called Hangzhou bore, was early mentioned during the 7th and 2nd centuries BC, and it was described in 8th century writings. The bore was then known as "The Old Faithful" because it kept time better than clocks. A tidal bore on the Indus river might have wiped out the fleet of Alexander the Great. Another famous tidal bore is the "pororoca" of the Amazon river observed by Pinzon and La Condamine in the 16th and 18th centuries respectively. The Hoogly (or Hooghly) bore on the Gange was documented in 19th century shipping reports. Smaller tidal bores occur on the Severn river near Gloucester, England, on the Garonne and Dordogne rivers, France, at Turnagain Arm and Knik Arm, Cook Inlet (Alaska), in the Bay of Fundy (at Petitcodiac and Truro), on the Styx and Daly rivers (Australia), and at Batang Lupar (Malaysia). In the present study, physical modelling will be used to reprodduced full-scale observations and to gain new insights in the unsteady hydrodynaics. The results will provide some new understanding of mixing processes in tidal-bore-affected estuaries.

Turbulence in unsteady rapidly-varied open channel flows

In water supply channels, the brusque operation of control gates may induce large unsteady flow motion called surges. Such a rapid operation of gates must often be restricted, although it may be conducted to scour silted channels and sewers. Herein a physical study will be conducted under controlled flow conditions to study the turbulent mixing in the very-close vicinity of a rapidly opening/closing gate, with a focus on the unsteady transient mixing induced by the gate operation. The processes are associated with large Reynolds stress levels. A succession of rapid closure and opening of undershoot gates may provide optimum conditions to scour silted canals, and the present study will provide some detailed insights into the physical processes.

Hydrodynamics of fish-friendly culverts

Man-made instream structures (e.g. dams and road crossings) have contributed to major declines in native fish numbers, with > 6,000 barriers to fish migration occurring in NSW alone. Recognising this, this project will integrate data on the swimming ability of Australian fish species with culvert hydraulic modelling to better understand fish requirements in and around road crossings. These data will strengthen national design guidelines and provide the tools engineers and planners need to balance fish migration with effective water management.

This project will provide data on the ability of Australian fish to successfully ascend through road crossings (culverts). These data will be used to develop National recommendations for ‘fish-friendly’ road crossing designs which better integrate the requirements of native fish with the need for cost-effective water management around roads.