scholarly journals On Local Scouring at Single Piers

2021 ◽  
Vol 1 (1) ◽  
pp. 1-16
Author(s):  
António Heleno Cardoso ◽  
◽  
Cristina Maria Sena Fael ◽  
Rui Miguel Madeira Lança ◽  
◽  
...  
Keyword(s):  
Scour Depth ◽  
Empirical Equations ◽  
Flow Intensity ◽  
Sand Size

The paper mostly summarizes disperse contributions of the authors published during the last fifteen years on the scour depth at single piers. These contributions rely on unique experiments in the sense that they are systematically longer than most of those found in the literature. The characterization of the effects of flow intensity, relative sand size, flow shallowness, time and pier shape and alignment is significantly improved as compared with existing literature. Our contributions consist on refinements of the model suggested by the school of Auckland, initiated by Raudkivi and boosted by Melville and his students. A considerable number of empirical equations and charts expresses those contributions.

scholarly journals Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations

2019 ◽  
Vol 8 (1) ◽  
pp. 4 ◽  
Author(s):  
Bingchen Liang ◽  
Shengtao Du ◽  
Xinying Pan ◽  
Libang Zhang
Keyword(s):  
Influencing Factors ◽  
Local Scour ◽  
Future Research ◽  
Scour Depth ◽  
Empirical Equations ◽  
Research Directions ◽  
Fundamental Knowledge ◽  
Future Research Directions ◽  
Flow Intensity ◽  
Bridge Failure

Scour induced by currents is one of the main causes of the bridge failure in rivers. Fundamental knowledge and mechanisms on scour processes due to currents are often taken as a basis for scour studies, which are the focus of this review. Scour development induced by waves and in combined wave–current conditions are also briefly discussed. For the design of structure foundations, the maximum scour depths need to be estimated. The mechanisms of local scour and predictions of maximum local scour depths have been studied extensively for many years. Despite the complexity of the scour process, a lot of satisfying results and progresses have been achieved by many investigators. In order to get a comprehensive review of local scour for vertical piles, major progresses made by researchers are summarized in this review. In particular, maximum scour depth influencing factors including flow intensity, sediments, pile parameters and time are analyzed with experimental data. A few empirical equations referring to temporary scour depth and maximum scour depth were classified with their expressing forms. Finally, conclusions and future research directions are addressed.

Clear-water local scour at wide piers in shallow-water flow

2014 ◽  
Vol 9 (3) ◽  
pp. 331-343 ◽  
Author(s):  
N. Ahmad ◽  
T. Mohamed ◽  
F. H. Ali ◽  
B. Yusuf
Keyword(s):  
Laboratory Data ◽  
Local Scour ◽  
The Other ◽  
Scour Depth ◽  
Temporal Development ◽  
Clear Water ◽  
Shallow Water Flow ◽  
Equilibrium Time ◽  
Sediment Size ◽  
Flow Intensity

Laboratory data for local scour depth regarding the size of wide piers are presented. Clear water scour tests were performed for various pier widths (0.06, 0.076, 0.102, 0.14 and 0.165 m), two types of pier shapes (circular and rectangular) and two types of uniform cohesionless bed sediment (d50 = 0.23 and d50 = 0.80 mm). New data are presented and used to demonstrate the effects of pier width, pier shape and sediment size on scour depth. The influence of equilibrium time (te) on scouring processes is also discussed. Equilibrium scour depths were found to decrease with increasing values of b/d50. The temporal development of equilibrium local scour depth with new laboratory data is demonstrated for flow intensity V/Vc = 0.95. On the other hand, the results of scour mechanism have shown a significant relationship between normalized volume of scoured and deposited with pier width, b. The experimental data obtained in this study and data available from the literature for wide piers are used to evaluate predictions of existing methods.

scholarly journals Investigation of Local Scour around L-Shape Submerged Groynes in Clearwater Conditions

2021 ◽  
Vol 28 (3) ◽  
pp. 159-169
Author(s):  
Saleh Issa Khassaf ◽  
Budoor Mohammed Rashak
Keyword(s):  
Froude Number ◽  
Local Scour ◽  
Scour Depth ◽  
Contour Lines ◽  
Low Profile ◽  
Scour Hole ◽  
Number Flow ◽  
Flow Intensity ◽  
Good Determination ◽  
New Formula

Submerged Groynes are low profile linear structures that are generally located on the outside bank to form Groynes fields and prevent the erosion of stream banks by redirecting high-velocity flow away from the bank. This research was studied in detail through two major stages. The first stage of the study is based on laboratory experiments to measure the development of local scour around L-shape submerged Groyne with the time, and special attention is given to the effects of different hydraulic and geometric parameters on local scour. Also; maps were drawn showing contour lines that represented the bed levels for maximum scour depth after reaching the equilibrium case. The result showed that a decrease in the scour depth ratio due to the increasing submerged ratio, and the number of Groynes. While the scour hole geometry will increase with the Froude number, flow intensity, and the spacing between Groynes, the decreasing percentage in the scour hole was measured to be about (4.3) % and (4.4) % for decreasing the spacing between Groynes from (2Lg) to (1.5Lg). Besides, it was range about (11.1) % and (14.0) % when reducing the spacing from (1.5Lg) to (Lg) under the same value of maximum Froude number. The second stage of the study is based on experimental results. A new formula was developed by using statistical analysis and it was found that a good determination coefficient.

Importance of Latitude and Organic Color on Phytoplankton Primary Productivity in Florida Lakes

1991 ◽  
Vol 48 (7) ◽  
pp. 1145-1150 ◽  
Author(s):  
John R. Beaver ◽  
Thomas L. Crisman
Keyword(s):  
Primary Production ◽  
Chlorophyll A ◽  
Primary Productivity ◽  
Phytoplankton Biomass ◽  
Nutrient Concentrations ◽  
Empirical Equations ◽  
Strongly Correlated ◽  
Florida Lakes ◽  
Vegetative Season

A characterization of primary productivity patterns in subtropical Florida lakes along increasing gradients of both dissolved organic color and phytoplankton biomass is presented. Volumetric expression of gross primary productivity was more strongly correlated with chlorophyll a and nutrient concentrations than was areal expression. Primary production in clearwater (<75 Pt units) lakes was more predictable than colored (>75 Pt units) lakes. Areal production in Florida lakes was intermediate to the tropical and temperate regions, although volumetric productivity during the vegetative season (May–September) was not significantly different from temperate zone lakes for the same period. Predictive abilities of empirical equations describing primary productivity in Florida lakes are improved by distinguishing colored and clear lakes.

scholarly journals Sensitivity analysis of bridge pier scour depth predictive formulae

2013 ◽  
Vol 15 (3) ◽  
pp. 939-951 ◽  
Author(s):  
Roberto Gaudio ◽  
Ali Tafarojnoruz ◽  
Samuele De Bartolo
Keyword(s):  
Sensitivity Analysis ◽  
Scour Depth ◽  
Relative Importance ◽  
Pier Scour ◽  
Sediment Size ◽  
Causative Factors ◽  
Flow Intensity ◽  
Influencing Parameters ◽  
Input Variables ◽  
Bridge Pier Scour

Sensitivity analysis is an approach to recognising the behaviour of models and relative importance of causative factors. In this paper, behaviours of six pier scour depth empirical formulae are evaluated on the basis of an analytical method. The sensitivity of predicted scour depth is analysed with respect to the following independent parameters: approach flow depth, riverbed slope and median sediment size. Also their combined influence is studied examining the relative importance of each parameter with respect to the total variation of the maximum scour depth. Results show that: (1) sensitivity significantly depends on flow intensity for most of the selected formulae, whereas for the others it is a constant value or depends on other influencing parameters; (2) different formulae demonstrate various level of sensitivity to the input variables, so that, for a certain error in the input variables, the error in the results may vary consistently; (3) some formulae are very sensitive to the input parameters under some conditions, hence an error in an input variable may be amplified in the output results; and (4) most of the formulae are more sensitive to the variations of the influencing parameters in clear-water than in live-bed conditions.

scholarly journals Application of Improved GMDH Models to Predict Local Scour Depth at Complex Bridge Piers

2020 ◽  
Vol 6 (1) ◽  
pp. 69-84 ◽  
Author(s):  
Habibeh Ghodsi ◽  
Mohammad Javad Khanjani
Keyword(s):  
Local Scour ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Group Method ◽  
Scour Depth ◽  
Empirical Equations ◽  
Depth Prediction ◽  
Pile Cap ◽  
Data Points ◽  
Statistical Criteria

Scour depth prediction is a vital issue in bridge pier design. Recently, good progress has been made in the development of artificial intelligence (AI) to predict scour depth around hydraulic structures base such as bridge piers. In this study, two hybrid intelligence models based on combination of group method of data handling (GMDH) with harmony search algorithm (HS) and shuffled complex evolution (SCE) have been developed to predict local scour depth around complex bridge piers using 82 laboratory data measured by authors and  615 data points from published literature. The results were compared to conventional GMDH models with two kinds of transfer functions called GMDH1 and GMDH2. Based upon the pile cap location, data points were divided into three categories. The performance of all utilized models was evaluated by the statistical criteria of R, RMSE, MAPE, BIAS, and SI. Performances of developed models were evaluated by experimental data points collected in laboratory experiments, together with commonly empirical equations. The results showed that GMDH2SCE was the superior model in terms of all statistical criteria in training when the pile cap was above the initial bed level and completely buried pile cap. For a partially-buried pile cap, GMDH1SCE offered the best performance. Among empirical equations, HEC-18 produced relatively good performances for different types of complex piers. This study recommends hybrid GMDH models, as powerful tools in complex bridge pier scour depth prediction.

Characterization of flow intensity in continuous centrifuges for the development of laboratory mimics

2001 ◽  
Vol 56 (16) ◽  
pp. 4759-4770 ◽  
Author(s):  
M Boychyn ◽  
S.S.S Yim ◽  
P Ayazi Shamlou ◽  
M Bulmer ◽  
J More ◽  
...  
Keyword(s):  
Flow Intensity

scholarly journals Electromechanical and Dynamic Characterization of In-House-Fabricated Amplified Piezo Actuator

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
P. K. Panda ◽  
B. Sahoo ◽  
S. Raja ◽  
Vijaya Kumar M. P. ◽  
V. Shankar
Keyword(s):  
Numerical Modeling ◽  
Amplification Factor ◽  
Piezo Actuator ◽  
Empirical Equations ◽  
Dynamic Characterization ◽  
Frequency Range ◽  
Maximum Displacement ◽  
Abaqus Software

A diamond-shaped amplified piezo actuator (APA) fabricated using six multilayered piezo stacks with maximum displacement of 173 μm at 175 V and the amplification factor of 4.3. The dynamic characterization of the actuator was carried out at different frequencies (100 Hz–1 kHz) and at different AC voltages (20 V–40 V). The actuator response over this frequency range was found neat, without attenuation of the signal. Numerical modeling of multilayered stack actuator was carried out using empirical equations, and the electromechanical analysis was carried out using ABAQUS software. The block force of the APA was 81 N, calculated by electromechanical analysis. This is similar to that calculated by dynamic characterization method.

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