scholarly journals Scour downstream of a corrugated apron under wall jets

2021 ◽  
Author(s):  
Rakesh Kumar Chaudhary ◽  
Zulfequar Ahmad ◽  
Surendra Kumar Mishra
Keyword(s):  
Flow Parameter ◽  
Empirical Equation ◽  
Wave Length ◽  
Flow Characteristics ◽  
Scour Depth ◽  
Wall Jets ◽  
Factors Affecting ◽  
Scour Holes ◽  
Velocity Turbulence ◽  
Single Size

Abstract Experiments were performed over smooth and corrugated aprons with different corrugation dimensions to study the scour and flow characteristics under submerged wall jets condition. The scour depth and length are significantly lower for corrugated than smooth rigid aprons. The maximum reductions in scour depth and length are 79 and 83%, respectively. Optimum scour depth and length are found for aspect ratio (ratio of corrugation wave length to amplitude) three for corrugated apron. The factors affecting scour depth and length were analyzed graphically, and empirical equations are proposed for predicting maximum scour depth and length, and the point of maximum scour depth for corrugated aprons. Velocity, turbulence characteristics, and Reynolds stress in scour holes for smooth and corrugated aprons were also studied. HIGHLIGHT This paper presents the scour downstream of corrugated apron and flow characteristics under submerged wall jets. Here scour depth and length reduces significantly than other apron. In this we have tried to develop empirical equation on single size sediment considering all the flow parameter and apron parameter. Besides this we have also conducted study related to turbulence and shear stress and velocity vector profile.

Experimental Study of Scour Due to Breaking Waves in Front of Vertical-Wall Breakwaters

2004 ◽  
Author(s):  
Ali Hasanzadeh Daloui ◽  
Mirmosadegh Jamali
Keyword(s):  
Experimental Study ◽  
Empirical Equation ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Scour Depth ◽  
Regular Waves ◽  
Factors Affecting ◽  
Wave Flume ◽  
Wave Heights

Scour is an important cause of instability of breakwaters. In case of vertical-wall breakwaters, toe scour can cause collapse of the whole structure. This paper is concerned with an experimental study of the effects of regular breaking waves on scour at toe of vertical-wall breakwaters. Experiments were carried out in a wave flume with regular waves for two cases of a beach with and without a breakwater. Bed profiles and scour depths for various wave heights, periods and depths were recorded. For the case of a beach without a breakwater, the observed bed profile types are compared to predictions. For the case of a beach with a breakwater, factors affecting the scour are investigated, and an empirical equation for scour depth at toe of a vertical wall is proposed.

Effects of Stenosis Asymmetry on Blood Flow in Stenotic Arteries and Wall Compression

1999 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Zhongdan Huan ◽  
David N. Ku
Keyword(s):  
Thrombus Formation ◽  
Flow Characteristics ◽  
Wall Stress ◽  
Critical Flow ◽  
Factors Affecting ◽  
Wall Deformation ◽  
Stenosis Severity ◽  
Wall Compliance ◽  
Stenotic Arteries ◽  
Considerable Work

Abstract Severe stenoses in arteries cause critical flow conditions which may be related to thrombus formation, artery compression and plaque cap rupture. The exact mechanism of these events and the conditions causing them are not well understood. Considerable work for flow in stenotic tubes have been reported in last twenty years and many interesting phenomena such as flow limitation, choking, flutter and wall collapse have been observed [3]. Stenosis severity, wall compliance and pressure conditions have been identified as dominating factors affecting wall deformation and flow and pressure fields. However, real arteries are rarely axisymmetric. Stenosis asymmetry may have considerable effects on wall stress and the critical flow characteristics.

scholarly journals Using Bayesian networks for the assessment of underwater scour for road and railway bridges

2020 ◽  
pp. 147592172095657
Author(s):  
Andrea Maroni ◽  
Enrico Tubaldi ◽  
Dimitri V Val ◽  
Hazel McDonald ◽  
Daniele Zonta
Keyword(s):  
Bayesian Networks ◽  
Bayesian Network ◽  
River Flow ◽  
Flow Characteristics ◽  
The United States ◽  
Monitoring Systems ◽  
Scour Depth ◽  
Bridge Scour ◽  
Railway Bridges ◽  
Scour Monitoring

Flood-induced scour is among the most common external causes of bridge failures worldwide. In the United States, scour is the cause of 22 bridges fails every year, whereas in the UK, it contributed significantly to the 138 collapses of bridges in the last century. Scour assessments are currently based on visual inspections, which are time-consuming and expensive. Nowadays, sensor and communication technologies offer the possibility to assess in real time the scour depth at critical bridge locations; yet, monitoring an entire infrastructure network is not economically feasible. A way to overcome this limitation is to instal scour monitoring systems at critical bridge locations, and then extend the piece of information gained to the other assets exploiting the correlations present in the system. In this article, we propose a scour hazard model for road and railway bridge scour management that utilises information from a limited number of scour monitoring systems to achieve a more confined estimate of the scour risk for a bridge network. A Bayesian network is used to describe the conditional dependencies among the involved random variables and to update the scour depth distribution using data from monitoring of scour and river flow characteristics. This study constitutes the first application of Bayesian networks to bridge scour risk assessment. The proposed probabilistic framework is applied to a case study consisting of several road bridges in Scotland. The bridges cross the same river, and only one of them is instrumented with a scour monitoring system. It is demonstrated how the Bayesian network approach allows to significantly reduce the uncertainty in the scour depth at unmonitored bridges.

scholarly journals Basal-flow characteristics of a non-linear flow sliding frictionless over strongly undulating bedrock

1997 ◽  
Vol 43 (143) ◽  
pp. 80-89 ◽  
Author(s):  
G. Hilmar Gudmundsson
Keyword(s):  
Flow Parameter ◽  
Flow Characteristics ◽  
Critical Value ◽  
Main Flow ◽  
Sliding Velocity ◽  
Flow Circulation ◽  
The Mean ◽  
Glacier Flow ◽  
Basal Shear ◽  
Basal Flow

AbstractThe flow field of a medium sliding without friction over a strongly undulating surface is calculated numerically. The results are used to elucidate the basal-flow characteristics of glacier flow and they are discussed with reference to known analytical solutions. Extrusion flow is found to become increasingly pronounced as the value of n, where n is a parameter in Glen’s flow law, becomes larger. For sinusoidal bedrock undulations, a flow separation occurs if the amplitude-to-wavelength ratio exceeds a critical value of about 0.28. The main flow then sets up a secondary flow circulation within the trough, and the ice participating in this circular motion theoretically never leaves it. The sliding velocity is calculated numerically as a function of the mean basal shear stress, the amplitude-to-wavelength ratio and the flow parameter n. For moderate and high slope fluctuations, the sliding velocity is significantly different from what would be expected from results based on the small-slope approximation.

scholarly journals Estimation of maximum scour depth downstream of an apron under submerged wall jets

2019 ◽  
Vol 21 (4) ◽  
pp. 523-540 ◽  
Author(s):  
Mohammad Aamir ◽  
Zulfequar Ahmad
Keyword(s):  
Scour Depth ◽  
Regression Equations ◽  
Wall Jets ◽  
Statistical Parameters ◽  
Densimetric Froude Number ◽  
Sediment Size ◽  
Fuzzy Interference System ◽  
Interference System ◽  
Neuro Fuzzy ◽  
Artificial Neural Network Ann

Abstract An analysis of laboratory experimental data pertaining to local scour downstream of a rigid apron developed under wall jets is presented. The existing equations for the prediction of the maximum scour depth under wall jets are applied to the available data to evaluate their performance and bring forth their limitations. A comparison of measured scour depth with that computed by the existing equations shows that most of the existing empirical equations perform poorly. Artificial neural network (ANN)- and adaptive neuro-fuzzy interference system (ANFIS)-based models are developed using the available data, which provide simple and accurate tools for the estimation of the maximum scour depth. The key parameters that affect the maximum scour depth are densimetric Froude number, apron length, tailwater level, and median sediment size. Results obtained from ANN and ANFIS models are compared with those of empirical and regression equations by means of statistical parameters. The performance of ANN (RMSE = 0.052) and ANFIS (RMSE = 0.066) models is more satisfactory than that of empirical and regression equations.

scholarly journals Numerical and experimental investigation for the effect of permeability of spur dikes on local scour

2019 ◽  
Vol 21 (2) ◽  
pp. 335-342 ◽  
Author(s):  
Riham Mohsen Ezzeldin
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Empirical Equation ◽  
Coefficient Of Determination ◽  
Scour Depth ◽  
Performance Indices ◽  
Relative Maximum ◽  
Spur Dikes ◽  
International River ◽  
Acceptable Agreement

Abstract The effect of using permeable spur dikes on the produced maximum scour depth compared to that of solid spur dikes is numerically investigated. The numerical model used for such purpose is the Nays-2DH model of the International River Interface Cooperative (iRIC) software package for bed and bank erosion. The model results are verified using the experimental data collected in this study by conducting experiments on five different models of spur dikes having different opening ratios. Using the statistical performance indices, the root mean square error and the coefficient of determination, the results showed an acceptable agreement between the numerical model results for the relative maximum scour depth defined by the ratio of the maximum scour depth to the flow depth and their corresponding observed values. A new empirical equation using nonlinear regression is developed using the experimental data collected in this study and tested with another existing empirical equation available in the literature for their accuracy in determining the relative maximum scour depth.

scholarly journals Factors affecting warmth comfort and stuffiness in domestic rooms

1947 ◽  
Vol 45 (4) ◽  
pp. 434-442
Author(s):  
K. W. Yarnold
Keyword(s):  
Air Temperature ◽  
Large Scale ◽  
Wave Length ◽  
Field Work ◽  
The Body ◽  
Equivalent Temperature ◽  
Factors Affecting ◽  
Two Factors ◽  
Striking Change ◽  
The Subject

One object of the investigation was to determine the ideal contributions to warmth comfort in small ‘domestic’ rooms of air heating and radiation. It was soon found that in rooms heated by fires, subjects usually complained of cold backs when the equivalent temperature was in the region of 60–65° F., the accepted standard for buildings heated by convection, and preferred equivalent temperatures above 70° F.Since large-scale trials, using many observers, were clearly necessary, the reliability of 5 min. test periods was studied; these short periods were proved reliable so long as the subject had previously been in a comfortable room for an hour or so.It was found necessary, in rooms heated by fires, to treat separately the side of the subject facing the fire and remote from it. The cooler side must be exposed to an equivalent temperature not much less than 65° F., while radiation falling on the warm side is to be regarded as a very desirable, but nonessential, bonus. These conclusions were confirmed by field work in the subjects' own homes.The eupatheoscope and globe thermometer were modified to enable conditions acting on the two sides of the body to be assessed separately.The extent to which radiation acting on the front of the body could compensate for a cold back to produce what was called ‘minimum comfort’ was also studied. It was shown that down to back equivalent temperatures of about 56° F. an increase of 2° in front equivalent temperature will compensate for a fall of 1° in back equivalent temperature, but below 56° F. compensation fails.The physical basis of sensations of stuffiness and freshness were also investigated. Throughout these experiments care was taken to ensure that the subjects were neither too hot nor too cold. In these conditions, only two factors appear to be important. First, the air temperature should be as low as possible. To obtain warmth comfort with a low air temperature some high temperature source of radiation is generally necessary. The peak wave-length of the radiation emitted by the fire is also of great importance, a striking change in the personal sensations occurring, for example, as the wave-length increases from 2 to 3μ. In general, those wavelengths which are absorbed in the outer layers of the skin cause sensations of stuffiness, and those which are not give rise to feelings of freshness. Peaks at 3, 4·1 and 4·7 μ should therefore be avoided in the design of gas and electric fires.

Local scour of cohesive beds downstream of a rigid apron

2017 ◽  
Vol 44 (11) ◽  
pp. 935-944 ◽  
Author(s):  
Hossein Hamidifar ◽  
Mohammad Hossein Omid
Keyword(s):  
Grain Size ◽  
Empirical Equation ◽  
Scour Depth ◽  
Removal Mechanism ◽  
Sediment Grain Size ◽  
Scour Hole ◽  
Hole Profile ◽  
The Mean ◽  
New Equation ◽  
Individual Particles

In this paper, the physics of scour hole in a mixed sand–clay bed downstream of an apron is studied experimentally. Seven combinations of sand–clay mixtures including clay contents, Cc, ranging from 0 to 0.4 were used. The results show that Cc = 0.4 can reduce the maximum scour depth, εm, up to about 80% for all the densimetric Froude numbers in the range of the present study. An empirical equation has been proposed for calculation of εm in sand–clay mixtures with the mean error of 0.12. The removal mechanism of sediments from the bed was different based on the Cc. For low clay contents, i.e., Cc ≤ 15%, individual particles were detached from the bed. At higher Cc, clusters of particles were separated and moved downstream with the flow. A new equation has been proposed to predict the dimensionless scour hole profile in mixed sand–clay sediments. Dimensionless graphs have been presented for incorporating the effect of tailwater depth and sediment grain size on the main characteristics lengths in sand–clay mixtures.

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