scholarly journals Experimental Study of Local Scour around Caissons under Unidirectional and Tidal Currents

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 640 ◽  
Author(s):  
Qiqi Xiang ◽  
Kai Wei ◽  
Fang Qiu ◽  
Changrong Yao ◽  
Yadong Li
Keyword(s):  
Cross Sections ◽  
Tidal Current ◽  
Opposite Effect ◽  
Tidal Currents ◽  
Local Scour ◽  
Bridge Engineering ◽  
Scour Depth ◽  
Factors Affecting ◽  
Main Factors ◽  
The Difference

Local scour around caissons under currents has become one of the main factors affecting the safety of foundation construction and operation in coastal and offshore bridge engineering. Local scour occurs not only in the operation stage, when the caisson has settled into the sediment, but also in the construction stage, when the caisson is suspended in water. In this study, the local scour induced by unidirectional and tidal currents around settled caissons with different cross-sections (circular, square, and diamond) was experimentally investigated. Circular and square caissons were selected to investigate the difference in local scour of suspended caissons under unidirectional and tidal currents. The main findings from the experimental results were: (1) the temporal development of scour under tidal current was slower than that of unidirectional current; (2) the effect of current type can significantly influence the size and location of maximum scour depth around circular and square caissons; (3) the appropriate choice of cross-section could reduce the maximum scour depth around the settled caisson; (4) the maximum scour depth of tidal current was smaller than that of unidirectional current when the caisson was settled into the sediment, while the opposite effect occurred when the caisson was suspended in water.

scholarly journals Scale Model Experiment on Local Scour around Submarine Pipelines under Bidirectional Tidal Currents

2021 ◽  
Vol 9 (12) ◽  
pp. 1421
Author(s):  
Zhiyong Zhang ◽  
Yakun Guo ◽  
Yuanping Yang ◽  
Bing Shi ◽  
Xiuguang Wu
Keyword(s):  
Tidal Current ◽  
Tidal Cycle ◽  
Engineering Application ◽  
Prediction Method ◽  
Tidal Currents ◽  
Local Scour ◽  
Scale Model ◽  
Hangzhou Bay ◽  
Scour Depth ◽  
Steady Current

In nearshore regions, bidirectional tidal flow is the main hydrodynamic factor, which induces local scour around submarine pipelines. So far, most studies on scour around submarine pipelines only consider the action of unidirectional, steady currents and little attention has been paid to the situation of bidirectional tidal currents. To deeply understand scour characteristics and produce a more accurate prediction method in bidirectional tidal currents for engineering application, a series of laboratory scale experiments were conducted in a bidirectional current flume. The experiments were carried out at a length scale of 1:20 and the tidal currents were scaled with field measurements from Cezhen pipeline in Hangzhou Bay, China. The experimental results showed that under bidirectional tidal currents, the scour depth increased significantly during the first half of the tidal cycle and it only increased slightly when the flow of the tidal velocity was near maximum flood or ebb in the following tidal cycle. Compared with scour under a unidirectional steady current, the scour profile under a bidirectional tidal current was more symmetrical, and the scour depth in a bidirectional tidal current was on average 80% of that under a unidirectional, steady current based on maximum peak velocity. Based on previous research and the present experimental data, a more accurate fitted equation to predict the tidally induced live-bed scour depth around submarine pipelines was proposed and has been verified using field data from the Cezhen pipeline.

Formula Type of Local Scour Depth on Spur Dike Nose

2014 ◽  
Vol 641-642 ◽  
pp. 271-274
Author(s):  
Qiang Ying
Keyword(s):  
Formation Process ◽  
Local Scour ◽  
Scour Depth ◽  
Calculation Methods ◽  
Spur Dike ◽  
Scour Hole ◽  
Main Factors ◽  
Formula Type ◽  
Suggested Formula

This passage introduces the formation process of scour hole, analyzes the main factors contributed to the local scour hole’s depth and classifies today’s calculation methods of scour depth into three categories. Then, given the conditions where those methods can be applied and drawbacks of those methods, this article also recommends some suggested formula in calculation.

scholarly journals LOCAL SCOUR CHARACTERISTICS OF GROINS AT TIDAL WATERWAYS AND THEIR SIMULATION

2011 ◽  
Vol 1 (32) ◽  
pp. 66
Author(s):  
Xiping Dou ◽  
Xinzhou Zhang ◽  
Xiao-dong Zhao ◽  
Xiangming Wang
Keyword(s):  
Mathematical Model ◽  
Sediment Transport ◽  
Steady Flow ◽  
Tidal Current ◽  
River Regulation ◽  
Local Scour ◽  
Hydraulic Structures ◽  
Scour Depth ◽  
Channel Regulation ◽  
Tidal Rivers

For the channel regulation in tidal rivers, groins are often used as typical hydraulic structures. Precisely predicting the local scour depth at the groin head is the key for the project of river regulation. The local scour of groins for tidal rivers is significantly different from that for the undirectional steady flow of general rivers. In the present paper, a three-dimendional (3D) mathematical model for turbulence and sediment transport are establishmented. The local scour near the groin under the actions of tidal current and steady flow are simulated by established 3D turbulence and sediment transport numerical model.The differences of the scour development and the scour pattern near the groin under these two actions are compared.

Seismic performance and improvements of split-foundation buildings in across-slope direction

2019 ◽  
Vol 23 (4) ◽  
pp. 749-763
Author(s):  
Gang Xu ◽  
Ruijun Zhang ◽  
Aiqun Li
Keyword(s):  
Seismic Performance ◽  
Design Procedure ◽  
Factors Affecting ◽  
Damage Pattern ◽  
Frame Buildings ◽  
Earthquake Action ◽  
Main Factors ◽  
The Difference ◽  
Foundation Structure ◽  
Slope Direction

The seismic performance and damage pattern of the split-foundation frame buildings in across-slope direction are studied. In view of the characteristics of split-foundation structure, the parameter analyses of split-foundation structure with different spans and floors of lower and upper parts are studied, and the main factors affecting the torsional effect of split-foundation structure are also studied theoretically. Finally, the improvements and design procedure of split-foundation structure are put forward to reduce the difference in ductility demands between the upper ground columns and the lower part. Results show that the torsional effect of split-foundation structure is very significant because of the rigidity eccentric. The upper ground columns are the weakest parts of split-foundation structure which are destroyed first under the earthquake action; then, the lower floors are destroyed in succession. Lower ductility demands of the upper ground columns and better seismic performance of the split-foundation structure can be achieved by the designed improvements.

An experimental study into local scour in a channel caused by a 90° bend

2006 ◽  
Vol 33 (7) ◽  
pp. 902-911 ◽  
Author(s):  
Jueyi Sui ◽  
Daxian Fang ◽  
Bryan W Karney
Keyword(s):  
Froude Number ◽  
Flow Direction ◽  
Local Scour ◽  
Scour Depth ◽  
Factors Affecting ◽  
Downstream Section ◽  
Series Of Experiments ◽  
Bed Material ◽  
Hydraulic Variables

Based on a series of experiments, this paper explores the influence of a 90° change in flow direction on local scouring. The influence on local scour patterns due to hydraulic parameters such as the Froude number, the slope of the protection wall, the width of the protection apron along the outside wall of the downstream section, and the grain size of the channel bed material is examined. Protection-wall slopes ranging from 1:0.5 to 1:4 (vertical to horizontal) were investigated, as were different widths of the protection apron; the goal was to ascertain the role of these variables in local scour patterns in the vicinity of the bend. The factors affecting local scour depth are related through empirical equations to key hydraulic variables, the slope of the protection wall, and the width of the protection apron.Key words: bent flume, channel erosion, Froude number, scour depth, slope of protection wall (SPW), width of protection apron (WPA).

scholarly journals Velocity profiles and turbulence intensities around side-by-side bridge piers under ice-covered flow condition

2020 ◽  
Vol 68 (1) ◽  
pp. 70-82
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui
Keyword(s):  
Flow Condition ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Measured Velocity ◽  
Acoustic Doppler Velocimetry ◽  
The Difference ◽  
Do So

AbstractRecent studies have shown that the presence of ice cover leads to an intensified local scour pattern in the vicinity of bridge piers. To investigate the local scour pattern in the vicinity of bridge pier under ice-covered flow condition comparing to that under open channel flow condition, it is essential to examine flow field around bridge piers under different flow conditions. In order to do so, after creation of smooth and rough ice covers, three-dimensional timeaveraged velocity components around four pairs of bridge piers were measured using an Acoustic Doppler velocimetry (ADV). The ADV measured velocity profiles describe the difference between the velocity distributions in the vicinity of bridge piers under different covered conditions. Experimental results show that the vertical velocity distribution which represents the strength of downfall velocity is the greatest under rough covered condition which leads to a greater scour depth. Besides, results show that the turbulent intensity increases with pier size regardless of flow cover, which implies that larger scour depth occurs around piers with larger diameter.

scholarly journals A fractal model for pressure drop through a cigarette filter

2020 ◽  
Vol 24 (4) ◽  
pp. 2653-2659 ◽  
Author(s):  
Zhanping Yang ◽  
Zhang Li ◽  
Dou Feng ◽  
Jie Li ◽  
Wenxuan Wan ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Cross Sections ◽  
Fractal Dimensions ◽  
Continuous Model ◽  
Fractal Model ◽  
Cigarette Filter ◽  
Factors Affecting ◽  
Filter Structure ◽  
Fractal Derivative ◽  
Main Factors

A fractal model for pressure drop through a cigarette filter is suggested, the fractal dimensions of both a single fiber and the filter?s cross-sections are calculated, which are two main factors affecting the pressure drop. The two-scale transform is made to convert the fractal derivative model on a smaller scale to an approximate continuous model on a larger scale, so that the model can be easily solved. An optimal filter structure is suggested for minimal pressure drop.

I Like Her, Because I Like Myself: Self-Evaluation as a Source of Interpersonal Attitudes

2003 ◽  
Vol 50 (4) ◽  
pp. 239-246 ◽  
Author(s):  
Eva Walther ◽  
Claudia Trasselli
Keyword(s):  
Opposite Effect ◽  
Learning Phase ◽  
The Self ◽  
Attitude Formation ◽  
Formation Processes ◽  
False Feedback ◽  
Self Evaluation ◽  
Evaluation Group ◽  
Group A ◽  
The Difference

Abstract. Two experiments tested the hypothesis that self-evaluation can serve as a source of interpersonal attitudes. In the first study, self-evaluation was manipulated by means of false feedback. A subsequent learning phase demonstrated that the co-occurrence of the self with another individual influenced the evaluation of this previously neutral target. Whereas evaluative self-target similarity increased under conditions of negative self-evaluation, an opposite effect emerged in the positive self-evaluation group. A second study replicated these findings and showed that the difference between positive and negative self-evaluation conditions disappeared when a load manipulation was applied. The implications of self-evaluation for attitude formation processes are discussed.

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