scholarly journals Experimental investigation of scouring around a single spur under clear water conditions

2021 ◽  
Author(s):  
Cansu Özyaman ◽  
Cahit Yerdelen ◽  
Ebru Eris ◽  
Rasoul Daneshfaraz
Keyword(s):  
Orientation Angle ◽  
Scour Depth ◽  
Clear Water ◽  
Spur Dike ◽  
Wide Range ◽  
Contraction Effect ◽  
Scouring Process ◽  
Spur Angle ◽  
Spur Length ◽  
Made In

Abstract This study presents the effect of different parameters on scouring process around spur dikes. Our research group's stated objective was to evaluate the effects of sediment gradation, flow depth, spur angle and spur length on scouring process. Since most existing studies generally employed uniform sediment; in this study uniform and non-uniform sediment were selected. Experiments were made in a rectangular open channel in uniform flow conditions. Results showed that the effect of the spur dike length and the orientation angle on sediment scour varies with the type of sediment used. Scour volumes were 40% greater in uniform sediments than in non-uniform sediments. Measured scour depth was maximum at spurs perpendicular to the flow, whereas the scour volume was maximum at spurs directed upstream. The scour depth increased with an increase in the spur length; however, effect of spur length on scouring varied at a contraction rate of 0.29 for uniform sediments and 0.36 for non-uniform sediments. A multiple regression analysis was also performed, and four equations were suggested to predict the scour depth and scour volume. Comparisons were made with the literature equations applicable for clear-water scouring to check the suggested equation. Because of a wide range of contraction ratios considered in this study, the equations which considered the contraction effect yielded better estimates.

Numerical investigation on the effect of bluntness factor on scouring mechanism by using lenticular geometry piers

2020 ◽  
Vol 47 (3) ◽  
pp. 279-290
Author(s):  
Yousef Hassanzadeh ◽  
Milad Khosravi ◽  
Nazila Kardan
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Flow Separation ◽  
Width Ratio ◽  
Scour Depth ◽  
Clear Water ◽  
Eddy Simulation ◽  
Water State ◽  
Large Eddy ◽  
Scouring Process

Local scour and flow field around cylinders with lenticular geometry and different bluntness factors under the clear-water state were investigated numerically. To examine the scouring, large eddy simulation with a WMLES-Omega sub-grid model incorporating the sediment transport and morphodynamic model was applied. Streamlined geometry of the pier significantly affected the scour pattern and flow field in the lenticular model with length to width ratio of 5 and bluntness factor of zero. In the mentioned case, a very small scoured region was estimated at the sides of the pier, so it can be concluded that scour depth and scoured region decreases as the length to width ratio increases. Investigation of the scouring process and the flow field revealed that, the flow separation can affect the scour mechanism more in comparison to down-flow.

scholarly journals A Non-Tuned Machine Learning Technique for Abutment Scour Depth in Clear Water Condition

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 301 ◽  
Author(s):  
Hossein Bonakdari ◽  
Fatemeh Moradi ◽  
Isa Ebtehaj ◽  
Bahram Gharabaghi ◽  
Ahmed A. Sattar ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Fundamental Equation ◽  
Percentage Error ◽  
Scour Depth ◽  
Clear Water ◽  
Dimensionless Variable ◽  
Sediment Size ◽  
Wide Range ◽  
Abutment Scour ◽  
The Impact

Abutment scour is a complex three-dimensional phenomenon, which is one of the leading causes of marine structure damage. Structural integrity is potentially attainable through the precise estimation of local scour depth. Due to the high complexity of scouring hydrodynamics, existing regression-based relations cannot make accurate predictions. Therefore, this study presented a novel expansion of extreme learning machines (ELM) to predict abutment scour depth (ds) in clear water conditions. The model was built using the relative flow depth (h/L), excess abutment Froude number (Fe), abutment shape factor (Ks), and relative sediment size (d50/L). A wide range of experimental samples was collected from the literature, and data was utilized to develop the ELM model. The ELM model reliability was evaluated based on the estimation results and several statistical indices. According to the results, the sigmoid activation function (correlation coefficient, R = 0.97; root mean square error, RMSE = 0.162; mean absolute percentage error, MAPE = 7.69; and scatter index, SI = 0.088) performed the best compared with the hard limit, triangular bias, radial basis, and sine activation functions. Eleven input combinations were considered to investigate the impact of each dimensionless variable on the abutment scour depth. It was found that ds/L = f (Fe, h/L, d50/L, Ks) was the best ELM model, indicating that the dimensional analysis of the original data properly reflected the underlying physics of the problem. Also, the absence of one variable from this input combination resulted in a significant accuracy reduction. The results also demonstrated that the proposed ELM model significantly outperformed the regression-based equations derived from the literature. The ELM model presented a fundamental equation for abutment scours depth prediction. Based on the simulation results, it appeared the ELM model could be used effectively in practical engineering applications of predicting abutment scour depth. The estimated uncertainty of the developed ELM model was calculated and compared with the conventional and artificial intelligence-based models. The lowest uncertainty with a value of ±0.026 was found in the proposed model in comparison with ±0.50 as the best uncertainty of the other models.

scholarly journals Bridge Abutment Protection against Scouring for Unsteady Flow Conditions

2021 ◽  
Author(s):  
Maryam Khajavi ◽  
Seyed Mahmood Kashefipour ◽  
Mahmood Shafai Bejestan
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Clear Water ◽  
Flow Conditions ◽  
Spur Dike ◽  
Base Time ◽  
Bridge Abutment ◽  
Water Conditions ◽  
Scouring Process ◽  
Spur Dikes

The bridge abutment is one of the main parts of a bridge and significantly contributes to bridge stability. This study experimentally investigated the effect of the unsteadiness characteristics of hydrographs on the scouring phenomenon around the bridge abutment under clear water conditions. The ability of the permeable and impermeable spur dikes and their distances from the abutment at its upstream on the control of scouring around the bridge abutment was also investigated. The experimental observations imply that the effect of unsteady flow on the scouring process is relatively similar to the steady flow conditions. The results showed that the base time of hydrographs, the type of spur dikes, and the distance of spur dikes from the bridge abutment were the dominant parameters among the considered parameters in this study on the scouring process around the abutment. The results also revealed that the impermeable spur dike was able to completely eliminate scouring around the bridge abutment for two distances of 2L and 3L (where L is the abutment length) for both steady and unsteady flow conditions.

Analysis of Clear-Water Scour at Bridge Contractions in Cohesive Soils

2002 ◽  
Vol 1797 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Oktay Güven ◽  
Joel G. Melville ◽  
John E. Curry
Keyword(s):  
Scour Depth ◽  
Cohesive Soils ◽  
Clear Water ◽  
Maximum Value ◽  
Total Head ◽  
Long Time ◽  
Simplifying Assumptions ◽  
Bed Materials ◽  
Cohesive Bed ◽  
Made In

A new, simplified theory for the analysis of the time-dependent development of the depth of scour at bridge contractions in cohesive soils under clear-water conditions is presented. The new theory is an extension of the clear-water scour theory for a long contraction currently used for non-cohesive bed materials. It is based on the “scour rate in cohesive soils” concepts introduced recently by Briaud and his colleagues at Texas A&M University. A description of the simplifying assumptions made in the development of the theory and several applications with different bed soils and flow conditions are presented to illustrate the effects of various assumptions on the estimate of the scour depth. Limitations of the theory are also discussed. The results indicate that a very long time may be required in some cohesive soils for the scour depth to reach its maximum value for a given flow condition. The results also indicate that significant differences in the estimate of the scour depth may occur depending on the assumptions made about the behavior of the water surface elevation and the total head in the contraction during the development of the scour in the contraction.

scholarly journals Simultaneous Effect of Collar and Roughness on Reducing and Controlling the Local Scour around Bridge Abutment

2017 ◽  
Vol 65 (2) ◽  
pp. 491-499
Author(s):  
Hamed Shahsavari ◽  
Manouchehr Heidarpour ◽  
Mohammad Mohammadalizadeh
Keyword(s):  
Local Scour ◽  
Hydraulic Structures ◽  
Scour Depth ◽  
River Engineering ◽  
Crucial Importance ◽  
Clear Water ◽  
Simultaneous Effect ◽  
Bridge Abutment ◽  
Scouring Process ◽  
Local Roughness

Investigation of local scour around hydraulic structures particularly bridges is of crucial importance in river engineering. Bridge destruction mostly occurs as a result of scour phenomenon around piers and abutments, not because of structural weaknesses. Hence, finding a solution to reduce scour depth is momentous. In this study which was conducted in the conditions of clear water scour, the effect of local roughness and collar and also impact of using them simultaneously around bridge abutment were evaluated. The results demonstrated that the existence of roughness causes a reduction in the severity of scouring process and its final depth and the use of collar leads to a delay in the scouring process in addition to the ultimate reduction in the scour depth, which in case of using them simultaneously, scour depth decreases by about 83%.

A Comprehensive Review on C-3 Functionalization of β-Lactams

2019 ◽  
Vol 16 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Reshma Nagpal ◽  
Jitender Bhalla ◽  
Shamsher S. Bari
Keyword(s):  
Scientific Community ◽  
Organometallic Reagent ◽  
Reaction Conditions ◽  
Biological Potential ◽  
Wide Range ◽  
Economic Strategies ◽  
Synthetic Utility ◽  
Recent Advancement ◽  
Equivalent Method ◽  
Made In

Background:A lot of advancement has been made in the area of β-lactams in recent times. Most of the research is targeted towards the synthesis of novel β-lactams, their functionalization and exploring their biological potential. The C-3 functionalization of β-lactams has continued to attract considerable interest of the scientific community due to their utility as versatile intermediates in organic synthesis and their therapeutic applications. This has led to the significant increase in efforts towards developing efficient and economic strategies for C-3 functionalized β-lactams.Objective:The present review aims to highlight recent advancement made in C-3 functionalization of β-lactams.Conclusion:To summarize, functionalization of β-lactams at C-3 is an essential aspect of β-lactam chemistry in order to improve/modify its synthetic utility as well as biological potential. The C-3 carbocation equivalent method has emerged as an important and convenient strategy for C-3 functionalization of β-lactam heterocycles which provides a wide range of β-lactams viz. 3-alkylated β-lactams, 3-aryl/heteroarylated β-lactams, 3- alkoxylated β-lactams. On the other hand, base mediated functionalization of β-lactams via carbanion intermediate is another useful approach but their scope is limited by the requirement of stringent reaction conditions. In addition to this, organometallic reagent mediated α-alkylation of 3-halo/3-keto-β-lactams also emerged as interesting methods for the synthesis of functionalized β-lactams having good yields and diastereoselectivities.

scholarly journals Multiplexed Genetic Analysis Using an Expanded Genetic Alphabet

2004 ◽  
Vol 50 (11) ◽  
pp. 2019-2027 ◽  
Author(s):  
Scott C Johnson ◽  
David J Marshall ◽  
Gerda Harms ◽  
Christie M Miller ◽  
Christopher B Sherrill ◽  
...  
Keyword(s):  
Newborn Screening ◽  
Cftr Gene ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Genetic Tests ◽  
Wide Range ◽  
Additional Base ◽  
A Prospective Study ◽  
Cystic Fibrosis Transmembrane ◽  
Made In

Abstract Background: All states require some kind of testing for newborns, but the policies are far from standardized. In some states, newborn screening may include genetic tests for a wide range of targets, but the costs and complexities of the newer genetic tests inhibit expansion of newborn screening. We describe the development and technical evaluation of a multiplex platform that may foster increased newborn genetic screening. Methods: MultiCode® PLx involves three major steps: PCR, target-specific extension, and liquid chip decoding. Each step is performed in the same reaction vessel, and the test is completed in ∼3 h. For site-specific labeling and room-temperature decoding, we use an additional base pair constructed from isoguanosine and isocytidine. We used the method to test for mutations within the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The developed test was performed manually and by automated liquid handling. Initially, 225 samples with a range of genotypes were tested retrospectively with the method. A prospective study used samples from >400 newborns. Results: In the retrospective study, 99.1% of samples were correctly genotyped with no incorrect calls made. In the perspective study, 95% of the samples were correctly genotyped for all targets, and there were no incorrect calls. Conclusions: The unique genetic multiplexing platform was successfully able to test for 31 targets within the CFTR gene and provides accurate genotype assignments in a clinical setting.

Evaluation of Selected Pier-Scour Equations Using Field Data

1996 ◽  
Vol 1523 (1) ◽  
pp. 186-195 ◽  
Author(s):  
Mark N. Landers ◽  
David S. Mueller
Keyword(s):  
Field Measurements ◽  
Bridge Piers ◽  
Critical Ratio ◽  
Scour Depth ◽  
Flow Depth ◽  
Clear Water ◽  
Pier Scour ◽  
Logarithmic Space ◽  
State Highway ◽  
Federal Highway

Field measurements of channel scour at bridges are needed to improve the understanding of scour processes and the ability to accurately predict scour depths. An extensive data base of pier-scour measurements has been developed over the last several years in cooperative studies between state highway departments, the Federal Highway Administration, and the U.S. Geological Survey. Selected scour processes and scour design equations are evaluated using 139 measurements of local scour in live-bed and clear-water conditions. Pier-scour measurements were made at 44 bridges around 90 bridge piers in 12 states. The influence of pier width on scour depth is linear in logarithmic space. The maximum observed ratio of pier width to scour depth is 2.1 for piers aligned to the flow. Flow depth and scour depth were found to have a relation that is linear in logarithmic space and that is not bounded by some critical ratio of flow depth to pier width. Comparisons of computed and observed scour depths indicate that none of the selected equations accurately estimate the depth of scour for all of the measured conditions. Some of the equations performed well as conservative design equations; however, they overpredict many observed scour depths by large amounts. Some equations fit the data well for observed scour depths less than about 3 m (9.8 ft), but significantly underpredict larger observed scour depths.

scholarly journals Dust Explosion Prevention and Mitigation, Status and Developments in Basic Knowledge and in Practical Application

2009 ◽  
Vol 2009 ◽  
pp. 1-12 ◽  
Author(s):  
Rolf K. Eckhoff
Keyword(s):  
Process Design ◽  
Basic Knowledge ◽  
Industrial Plant ◽  
Practical Application ◽  
Process Industries ◽  
Wide Range ◽  
Firm Knowledge ◽  
Systematic Education ◽  
Training Of Personnel ◽  
Made In

Right from the early days of the process industries, continuous efforts have been made to develop and improve measures for prevention and mitigation of dust explosions in these industries. Nevertheless this hazard continues to threaten industries that manufacture, use and/or handle powders and dusts of a wide range of combustible materials. To improve methods for predicting explosion development in real industrial plant has been one major challenge. Hence, during the last years comprehensive numerical simulation codes, for addressing this problem, have been developed. Progress has also been made in other areas, for example, ignition source prevention. The importance of adopting inherently safer process design, by building on firm knowledge in powder science and technology, and of systematic education/training of personnel, is also emphasized.

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