Roughness of reverse flow over dunes and its application to the modelling of the Pitt River

1988 ◽  
Vol 15 (4) ◽  
pp. 547-552
Author(s):  
Y. L. Lau
Keyword(s):  
Key Words ◽  
Friction Factor ◽  
Reverse Flow ◽  
Tidal Flow ◽  
Fraser River ◽  
Upstream Side ◽  
Bed Roughness

Experiments using artificial dunes show that the friction factor is reduced when the steep face of the dune is on the upstream side, i.e., when the direction is reverse that of normal. Calculations using bedform regime relationships show that this configuration of reverse flow over dune profiles could have existed in the Pitt River, causing the decrease in bed roughness which was found during the calibration runs. Key words: friction factor, dunes, tidal flow, Fraser River, bedform roughness, Pitt River.

Construction of the Iona Outfall submarine section

1990 ◽  
Vol 17 (1) ◽  
pp. 113-118 ◽  
Author(s):  
T. W. Lively ◽  
C. D. Gowe ◽  
H. R. Woodhead
Keyword(s):  
Key Words ◽  
Joint Venture ◽  
Sewage Treatment ◽  
Bolted Joints ◽  
Fraser River ◽  
Strait Of Georgia ◽  
Alternative Method

In February 1987, the Greater Vancouver Sewerage and Drainage District awarded an $8.5 million contract for the construction of the Iona Outfall submarine section. The contract awarded to the Dillingham–Manson joint venture involved the installation of approximately 3200 m of twin 2.3 m diameter steel outfall, of which 500 m was twin 2.1, 1.8, and 1.4 m diameter steel diffuser sections. The outfall extended from the end of the Iona Jetty into the Strait of Georgia near the mouth of the Fraser River and was 107 m deep at the end of the diffuser. The tender documents suggested a method of installation such that the entire twin outfall pipe was fabricated on an existing jetty complete with flotation pipe and pulled into the water. The contractor submitted an alternative method with the tender and was the successful low bidder. The proposed installation method was to assemble the pipe into nominal 300 m lengths in Dillingham's North Vancouver yard, launch them, tow them to the site, and sink and bolt them together underwater. This paper discusses the more interesting aspects of the project. Key words: construction, pipelines, robotics, sewage treatment, bolted joints.

Optimal swimming speeds and forward-assisted propulsion: energy-conserving behaviours of upriver-migrating adult salmon

2000 ◽  
Vol 57 (12) ◽  
pp. 2470-2478 ◽  
Author(s):  
Scott G Hinch ◽  
Peter S Rand
Keyword(s):  
Swimming Speed ◽  
Sockeye Salmon ◽  
Reverse Flow ◽  
Fraser River ◽  
Fitness Costs ◽  
Transport Costs ◽  
Long Distance ◽  
Energetic Costs ◽  
Unit Distance ◽  
Energy Conserving

Anadromous salmon migrations are energetically expensive. Long-distance migrants should be efficient in their use of energy and minimize swimming costs wherever possible. We explore swimming strategies and energy-saving tactics employed by three long-distance-migrating sockeye salmon (Oncorhynchus nerka) stocks in the Fraser River watershed, British Columbia. We used stereovideography and bank-side observations to estimate swimming speeds (from tailbeat frequency) and ground speeds (using distance traveled and duration) for individuals at several sites. Salmon were highly efficient at migration (i.e., ground speeds equaled or exceeded swimming speeds) through reaches with relatively low encountered currents (<0.25 m·s-1). We speculate that salmon exploit small reverse-flow vortices to achieve this feat. With low encountered currents, most salmon migrated according to an optimal swimming speed model: migrants minimized transport costs per unit distance traveled. Generally, salmon were less efficient at migration with fast currents, although the Chilko stock were superoptimal migrants, possibly owing to unique morphology and (or) behaviours. The risk of significant delays is enhanced when fast currents are encountered. Under these conditions, relatively fast swimming speeds could minimize travel time, despite high costs. Migrants may be balancing energetic costs of migration against the fitness costs of spawning delays.

Influence of delta growth on paleo‐tidal flow: Fraser River delta, British Columbia—Part 2: Tidal model

1989 ◽  
Vol 13 (3) ◽  
pp. 229-243 ◽  
Author(s):  
T. S. Murty ◽  
D. K. Lee ◽  
M. C. Roberts
Keyword(s):  
British Columbia ◽  
Tidal Flow ◽  
River Delta ◽  
Fraser River ◽  
Tidal Model ◽  
Fraser River Delta ◽  
Delta Growth

DISTRIBUTION OF SULPHUR FORMS IN SIX FACIES OF PEATS OF THE FRASER RIVER DELTA

1985 ◽  
Vol 65 (3) ◽  
pp. 531-541 ◽  
Author(s):  
L. E. LOWE ◽  
R. M. BUSTIN
Keyword(s):  
Key Words ◽  
Brackish Water ◽  
River Delta ◽  
Fraser River ◽  
Organic Form ◽  
Organic S ◽  
Organic Sulphur ◽  
Inorganic Sulphate ◽  
Fraser River Delta

The distribution of organic and inorganic S forms was examined in peats formed under the influence of fresh and brackish water on the Fraser River Delta. Six peat facies classified as sphagnum, ericaceous sphagnum, freshwater sedge, brackish sedge, freshwater clay or brackish clay were found to contain variable levels of sulphur. Brackish systems contained much more S than freshwater-derived materials. Highest S contents (mean 3.0%) were found in brackish sedge peat samples, and the lowest in sphagnum-derived peat (mean 0.19%). For all facies examined, organic S was dominant and accounted for 90–97% of Total S. Carbon-bonded S was the dominant organic form and was much more abundant than organic sulphate S. Inorganic sulphate, elemental S, pyritic S and H2S made minor contributions to the total S. Increasing degree of decomposition of peat is associated with increasing S content. Key words: Sulphur forms, organic sulphur, peat sulphur, degree of decomposition

scholarly journals Modelling Tidal Flow Hydrodynamics of Sunda Strait, Indonesia

2020 ◽  
Vol 25 (4) ◽  
pp. 165-172
Author(s):  
Munawir Bintang Pratama ◽  
Vengatesan Venugopal ◽  
Harman Ajiwibowo ◽  
Juventus Welly Ginting ◽  
Franto Novico
Keyword(s):  
Boundary Conditions ◽  
Water Level ◽  
Current Velocity ◽  
Tidal Flow ◽  
Tidal Currents ◽  
Recreational Fisheries ◽  
The Past ◽  
Northern Side ◽  
Bed Roughness ◽  
Good Agreement

In the past years, Indonesian people put more attention to Sunda Strait located between Java and Sumatra Islands, one of the busiest straits occupied with residential, recreational, fisheries, transportation, industrial and mining activities. Previous works on numerical modelling of tidal flow hydrodynamics of the Sunda Strait have resulted in good agreement against field data; however, the calibration of the models used was not described in detail. This paper presents the process of setting up the model, extensive calibration, validation and prediction of tidal currents for the Sunda Strait. A two-dimensional tidal-driven model is constructed using Delft3D, an open-source developed by Deltares. Four different bathymetry datasets, four different boundary condition configurations, and various bed roughness values are used, and their suitability in predicting tidal water level and current are investigated. It is found that changing the bathymetry and boundary conditions improve the model validation significantly. GEBCO_2019 bathymetry dataset outperforms the Batnas, even though it has a coarser resolution. For boundary conditions, the combination of water level and current velocity results in a better validation compares to using water level or current velocity only. However, the bed roughness shows an insignificant influence in predicting tidal conditions. The averaged current velocity is lower at the Southern than the Northern side of the strait due to a larger cross-section, consequence of deeper water. High tidal currents of magnitude around 2 m.s-1 are seen at the bottleneck of the strait.

Multislice imaging of gastrointestinal stromal tumors

2018 ◽  
pp. 3-14
Keyword(s):  
Computed Tomography ◽  
Key Words ◽  
Gold Standard ◽  
Gastrointestinal Stromal Tumors ◽  
Mesenchymal Tumors ◽  
Stromal Tumors ◽  
Preferential Localization ◽  
Multislice Imaging ◽  
Computed Tomography Diagnosis

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the digestive tract (1%). These tumors express the CD 117 in 95% of cases. The stomach is the preferential localization (70%). Diagnosis is difficult and sometimes late. Progress of imaging has greatly improved the management and the prognosis. Computed tomography (CT) is the gold standard for diagnosis, staging, and treatment follow-up. The increasing recognition of GIST’s histopathology and the prolonged survival revealed some suggestive imaging aspects. Key words: gastro-intestinal stromal tumors; computed tomography; diagnosis

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