Somewhere on the River Bend

2021 ◽  
pp. 15-32
Keyword(s):  
River Bend

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

A Review of the PSA Model Truncation Convergence Issues at Some ENS Plants

2006 ◽  
Author(s):  
Fatma Yilmaz
Keyword(s):  
Safety Assessment ◽  
Recent Model ◽  
Probabilistic Safety Assessment ◽  
Rule Of Thumb ◽  
Model Update ◽  
The Subject ◽  
River Bend ◽  
Probabilistic Safety

This study provides the insights gained from the Probabilistic Safety Assessment (PSA) model update of several Entergy Nuclear South (ENS) plants with respect to truncation convergence based on the limited guidance on the issue in the industry. The industry rule of thumb, the ASME and NRC guidance and requirements on the subject have been reviewed. The recent model updates performed at some of the ENS plants (River Bend, ANO 1 and 2) considered these criteria. Based on the current criteria used in the industry for truncation convergence, the recent PSA model update results for the River Bend Station (RBS) and ANO-1 are not converging even at a low truncation limit of 1E−11/reactor-year (yr). Many improvements were introduced in the recent model updates and convergence was expected at higher truncation values. This paper discusses the issues identified that are related to the convergence of the PSA results at low truncation limits.

Molluscan biostratigraphy of the lower River Bend Formation at the Martin Marietta Quarry, New Bern, North Carolina

1991 ◽  
Vol 65 (1) ◽  
pp. 80-118 ◽  
Author(s):  
Thomas J. Rossbach ◽  
Joseph G. Carter
Keyword(s):  
North Carolina ◽  
Coastal Plain ◽  
Warm Water ◽  
Gulf Coastal Plain ◽  
Generic Level ◽  
Evolutionary Transitions ◽  
Molluscan Fauna ◽  
Molluscan Diversity ◽  
Molluscan Species ◽  
River Bend

The lower River Bend Formation at the Martin Marietta New Bern quarry in Craven County, North Carolina, contains a diverse and abundant moldic molluscan fauna. This fauna, reconstructed by latex casts, suggests a Vicksburgian or a post-Vicksburgian, pre-Chickasawhayan age for the New Bern exposure. Forty-one molluscan species and subspecies are presently identified from the lower River Bend Formation, 11 of which are new: Turritella caelatura alani, Turritella neusensis, Galeodaria britti, Phalium newbernensis, Cymatium planinodum, Oocorys vadosus, Ecphora wheeleri, Lyria concinna, Scaphella saintjeani, Turricula (Orthosurcula) aequa, and Lucina (Stewartia) micraulax. This fauna is virtually identical at the generic level and similar at the species level to the Vicksburgian faunas of the Gulf Coastal Plain. About 37 percent of the New Bern species also occur in the Vicksburgian of Mississippi, although many of these species reach considerably larger sizes at New Bern. Apparent evolutionary transitions between previously known Vicksburgian and Chickasawhayan mollusks suggest a time of deposition intermediate between these two Oligocene stages.Moderately high molluscan diversity, the abundance of characteristically warm-water genera, and associated carbonate-rich sediments suggest that the lower River Bend Formation represents a subtropical, open-marine, predominantly carbonate environment immediately seaward of a nearshore lagoonal or barrier island complex.The lower River Bend Formation at New Bern differs faunally, climatically, and sedimentologically from the upper River Bend Formation in quarry exposures near Belgrade, North Carolina. The upper River Bend Formation contains a lower diversity molluscan fauna with marked dominance diversity and few warm-water taxa. It represents a slightly cooler nearshore, open-marine environment in a transitional siliciclastic-carbonate sedimentary regime. The considerable taxonomic and sedimentologic differences between the lower and upper parts of the River Bend Formation corroborate microfossil evidence suggesting that they represent temporally distinct depositional cycles.

scholarly journals Studi Pengaruh Sudut Belokan Sungai Terhadap Volume Gerusan

2017 ◽  
Vol 4 (1) ◽  
pp. 60 ◽  
Author(s):  
Hasdaryatmin Djufri
Keyword(s):  
Experimental Model ◽  
Water Flow ◽  
Model Tests ◽  
Sand Layer ◽  
Flow Discharge ◽  
Layer Density ◽  
Artificial Channel ◽  
River Bends ◽  
The Stability ◽  
River Bend

Scouring occurs along the streams and generally increases in their bend areas. This occurence threaten the stability of buildings and facilities built around those areas. This study was conducted by experimental model tests in a laboratory using an artificial channel made of sand with diameter of 0,47 mm and the sand layer density of 1,47 gr/cm3. To assess the effect of river bends on the extent of scours, the water flow was simulated on the artificial channel in 9 times i.e.; 3 variations in the angle of river bends (α) and 3 variations in the flow discharge (Q) for each river bend variation. This study revealed that the volume of scours positively correlated to the angle of river bends. The volume of scours decreased more 20% when the angle of river bends decresed from 60º to 30º. The increase of the flow discharge also enlarged the volume of scours more than 100% at the river bends with small angles

Sustainable aquaculture development in oxbow lakes with emphasis on the involvement of women.

2020 ◽  
Author(s):  
Md. Kibria
Keyword(s):  
Fish Farming ◽  
Active Participation ◽  
Economic Effects ◽  
Oxbow Lake ◽  
General Idea ◽  
Oxbow Lakes ◽  
Pond Aquaculture ◽  
And Gender ◽  
Aquaculture Development ◽  
River Bend

Abstract A total of 600 oxbow lakes are located in the southwestern part of Bangladesh, covering 5,488 ha. An oxbow lake (baor) is an old cut-off river bend, usually in the shape of a horseshoe. Pond aquaculture for women was introduced in oxbow lakes in 1995-1996 to allow their active participation in aquaculture as a livelihood activity. The shallow and silted parts of the baor were excavated into 0.5 to 1.5 ha size fishponds. This study was conducted in 1999 in two selected oxbow lakes in Jessore district to assess the technological and socio-economic effects of fish farming groups (FFGs) and pond aquaculture in oxbow lakes with emphasis on the involvement of women. Three categories of questions (socio-economic, technical and gender) were asked of FFG members. This study shows that initially when the women became involved in pond excavation and dike compaction, as members of the FFGs, most of their men members did not like this. As Bangladesh is a Muslim-dominant country, there is a general idea among men that women should not work outside together with men. However, after a few years, once the success of the women's fish farming activities and marketing became clear, their social status and respect in the society and family increased through their active participation in this process. A total of 23 oxbow lakes in five districts around Jessore, covering 1,400 ha, have been handed over from the Ministry of Land to the Department of Fisheries (DOF). Subsequently, the DoF transferred the user-rights to the beneficiaries for a period of 50 years.

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