Explicit equations for critical depth in open channels with complex compound cross sections. A discussion

In open channel hydraulics, the notion of critical flow conditions and critical depth are not restricted to open channel flows with hydrostatic pressure distributions. This contribution shows an extension of the concept of critical flow conditions linked with the minimum specific energy, as introduced by Bakhmeteff [1] and extended by Liggett [9] and Chanson [5]. It demonstrated that the critical depth may be defined more broadly including when the pressure field is not hydrostatic

Should Field Works Be Compulsory in Hydraulic Engineering Courses ?

Engineering graduates should be familiar with real-world problems, practical applications and relevant solutions. Hydraulic engineers are no exception, but the teaching of open channel hydraulics is a major challenge. In open channel flows, the free surface rises and falls in response to perturbations to the flow (e.g., changes in channel slope or width). Field studies complement traditional lectures and laboratory work. Student fieldwork was introduced systematically in a series of hydraulic engineering subjects within undergraduate civil and environmental engineering curricula. Anonymous student feedback demonstrated a strong student interest for the fieldwork. This was associated with greater motivation for the course, leading in turn to lower failure rates. Feedback from former students indicated that fieldwork experience was an important component of their studies and helped their professional development. Employers testified that fieldwork are an essential component of a hydraulic engineering course and that it should be a requirement in all civil/environmental engineering curricula. This pedagogical experience demonstrated the very-significant role of fieldwork in the teaching of hydraulic engineering. Lecturers and professionals should not be complacent with university hierarchy and administration clerks intent on cutting costs by eliminating field studies. Although the preparation of fieldwork with large class sizes is a major effort, the outcome is very rewarding for the students and the lecturer. Yes, fieldwork should be definitely compulsory in each and every hydraulic engineering course

Coastal Observations: North Stradbroke Island, Moreton Bay, Australia

North Stradbroke Island is located 30 km southeast of Brisbane, Queensland, Australia. It is part of a series of three large sandy islands separating Moreton Bay from the Pacific Ocean. These are South Stradbroke Island, North Stradbroke Island and Moreton Island. On Sept. 3, 1894, the barque Cambus Wallace wrecked off Stradbroke Island around the narrow isthmus of Tuleen. Explosives from the salvaged cargo were detonated, weakening the dunes. Storms and rough seas in the following years helped the sea to break through Stradbroke island, creating the Jumpinpin Bar. North Stradbroke Island is about 38 km long and 11 km wide. On the Pacific Ocean side, Main Beach extends for 32 km. Locally known as "Straddie", North Stadbroke Island has several freshwater lakes, waterways and lagoons. Whales, dolphins, turtles and manta rays are regularly spotted from Point Lookout headland and the North Gorge. More than 253 species of bird life live here, including Little Penguin, Wandering Albatross, Great Cormorant, Black Swan, Whistling Kite, White-bellied Sea-Eagle, Galah, Tawny Frogmouth, Azure Kingfisher, Forest Kingfisher, Red-backed Kingfisher and Sacred Kingfisher. Figure 6 shows a whale spotted off Main Beach

Current knowledge in hydraulic jumps and related phenomena: A survey of experimental results

The hydraulic jump is the sudden transition from a high-velocity open channel flow regime to a subcritical flow motion. The flow properties may be solved using continuity and momentum considerations. In this review paper, recent advances in turbulent hydraulic jumps are developed: the non-breaking undular hydraulic jump, the positive surge and tidal bore, and the air bubble entrainment in hydraulic jumps with roller. The review paper demonstrates that the hydraulic jump is a fascinating turbulent flow motion and the present knowledge is insufficient, especially at the scales of environmental and geophysical flows

Jet Flow on Stepped Spillways

The authors provided interesting data on stepped spillway flows. The writer would like to add some information on flow resistance of skimming flows and discuss the energy dissipation on stepped chutes. It will be shown that the author's results are not dissimilar with results previously obtained by other researchers (table A1)

Research Quality, Publications and Impact in Hydraulic Engineering into the 21st Century. Publish or Perish, Commercial versus Open Access, Internet versus Libraries

One of the main objectives of the first International Junior Researcher and Engineer Workshop on Hydraulic Structures is to provide an opportunity for young researchers and engineers to present their research. But a research project is only completed when it has been published and shared with the community. Referees and peer experts play an important role to control the research quality. While some new electronic tools provide further means to disseminate some research information, the quality and impact of the works remain linked with some thorough expert-review process and the publications in international scientific journals and books. Importantly unethical publishing standards are not acceptable and cheating is despicable

Hydraulics of Roman Aqueducts : Steep Chutes, Cascades and Dropshafts

This paper examines the archaeological evidence for steep chutes, cascades, and dropshafts in Roman aqueducts. It also presents comparative data on steep-descent water flow in aqueducts based on physical model tests. It is suggested that the Romans were aware of the hydraulic problems posed by supercritical water flows and that the technological solutions they imposed were rudimentary but sound: for example, they understood the need for energy dissipation devices such as the stilling basin and the dropshaft

Drag Reduction in Skimming Flow on Stepped Spillways by Aeration

In skimming flows on stepped spillway, flow resistance is predominantly a form drag process. Cavity recirculation and air entrainment are intense. The interactions between entrained air bubbles and mixing layers may cause some reduction in flow resistance. The paper presents new evidence showing a reduction in friction factor in skimming flow with increasing free-surface aeration. The experimental data are based upon detailed air-water flow measurements in large size models and may be extended to prototypes. The results might suggest some drag reduction, although comparable clear-water flow data are rare