scholarly journals Scour depth in confluences considering tributary flow, bank slope, and post-confluence conditions

2020 ◽  
Vol 20 (6) ◽  
pp. 2389-2399
Author(s):  
Payam Khosravinia ◽  
Amir Malekpour ◽  
Mohammad Reza Nikpour ◽  
Ali Hosseinzadeh Dalir
Keyword(s):  
Froude Number ◽  
Slope Angle ◽  
Main Channel ◽  
Maximum Effect ◽  
Scour Depth ◽  
Empirical Relationships ◽  
Point Bar ◽  
Densimetric Froude Number ◽  
Bank Slope ◽  
Discharge Ratio

Abstract In this paper, scouring in confluences was experimentally studied considering the effects of bank slope angle (θ) of the main channel, discharge ratio (Qr) of tributary channel and densimetric Froude number (Frg3) of the post-confluence channel. The experiments were conducted using a constant confluence angle (α) equal to 90° and various bank slope angles of 45°, 60°, 75° and 90°. Applying different Qr and Frg3, the maximum effect of θ on scour depth was observed when the minor Qr was used in the tributary channel. The mildest bank slope angle caused the minimum scour depth for any given Frg3. Generally, the experiment using θ = 45° and Qr = 0.194 showed the best performance and reduced the maximum scour depth by 46%. Considering two obtained empirical relationships, it was concluded that the effect of θ on the height of the point bar is more than its effect on the scour depth. Finally, Frg3 and θ demonstrated their greatest influences on dimensionless scour depth (dse/y3) and dimensionless height of point bar (Hse/B3), respectively.

scholarly journals Impact of armour layer on the depth of scour hole around side-by-side bridge piers under ice-covered flow condition

2019 ◽  
Vol 67 (3) ◽  
pp. 240-251
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui
Keyword(s):  
Grain Size ◽  
Froude Number ◽  
Large Scale ◽  
Bridge Piers ◽  
Scour Depth ◽  
Flow Conditions ◽  
Densimetric Froude Number ◽  
Open Flow ◽  
Scour Holes ◽  
The Impact

Abstract In the present study, experiments were conducted in a large-scale flume to investigate the issue of local scour around side-by-side bridge piers under both ice-covered and open flow conditions. Three non-uniform sediments were used in this experimental study. Analysis of armour layer in the scour holes around bridge piers was performed to inspect the grain size distribution curves and to study the impact of armour layer on scour depth. Assessments of grain size of deposition ridges at the downstream side of bridge piers have been conducted. Based on data collected in 108 experiments, the independent variables associated with maximum scour depth were assessed. Results indicate that the densi-metric Froude number was the most influential parameter on the maximum scour depth. With the increase in grain size of the armour layer, ice cover roughness and the densimetric Froude number, the maximum scour depth around bridge piers increases correspondingly. Equations have been developed to determine the maximum scour depth around bridge piers under both open flow and ice covered conditions.

Application of Particle Densimetric Froude Number for Evaluating the Maximum Culvert Scour Depth

2020 ◽  
Vol 146 (8) ◽  
pp. 04020020 ◽  
Author(s):  
Sheau Maan Tan ◽  
Siow-Yong Lim ◽  
Maoxing Wei ◽  
Nian-Sheng Cheng
Keyword(s):  
Froude Number ◽  
Scour Depth ◽  
Densimetric Froude Number

Effect of particle size on flip bucket scour

2016 ◽  
Vol 43 (8) ◽  
pp. 759-768 ◽  
Author(s):  
Mehmet Ali Kökpinar ◽  
Serhat Kucukali
Keyword(s):  
Particle Size ◽  
Reynolds Number ◽  
Froude Number ◽  
Physical Model ◽  
Physical Basis ◽  
Scour Depth ◽  
Empirical Formulas ◽  
Densimetric Froude Number ◽  
Effect Of Particle Size

This study quantifies the dimensionless maximum scour depth ds/D50 downstream of flip buckets as a function of the square of the densimetric Froude number Frd2, jet Reynolds number Re, lip angle, and sediment non-uniformity constant. The proposed formula is valid for Frd = 2.9–29.69, Re = 8.9 × 103–4.2 × 105, and We > 32. Moreover, the scour profiles for different sediment sizes (D50 = 3–17 mm) are presented from the Kigi Dam physical model and the effect of the Reynolds number on scour process is discussed. The prediction capacity of the proposed formula is compared with the existing empirical formulas in the literature and it is shown that the proposed dimensionally homogenous formula made better estimations. The procedure described here has a sound physical basis and it can be used to estimate the maximum scour depth downstream of flip buckets.

Experimental Studies of Sedimentation Basin Dynamics

1977 ◽  
Vol 12 (1) ◽  
pp. 77-90
Author(s):  
J.F. Cordoba-Molina ◽  
P.L. Silveston ◽  
R. R. Hudgins
Keyword(s):  
Dynamic Response ◽  
Froude Number ◽  
Flow Model ◽  
Experimental Studies ◽  
Densimetric Froude Number ◽  
Number Range ◽  
The Real ◽  
Highly Correlated ◽  
Sedimentation Basins ◽  
Simple Flow

Abstract A simple Flow Model is proposed to describe the dynamic response of sedimentation basins. The response predicted by this model is linear as opposed to the real response of the basin which is nonlinear. However, the real response of the basin is highly correlated with its densimetric Froude number, and as a consequence our linear model effectively predicts the response of the basin in a restricted densimetric Froude Number range. Our experiments show that the response of the basin becomes more sluggish and erratic as the densimetric Froude number decreases.

Numerical Investigation of Local Scour Around Submerged Pipeline in Shoaling Conditions

2018 ◽  
Author(s):  
Ming-ming Liu ◽  
Ming Zhao ◽  
Lin Lu
Keyword(s):  
Water Waves ◽  
Slope Angle ◽  
Suspended Load ◽  
Local Scour ◽  
Navier Stokes ◽  
Bed Load ◽  
Scour Depth ◽  
Two Dimensional ◽  
Sediment Mass ◽  
Subsea Pipelines

Water waves play an important role in local scour around subsea pipelines laid on the sandy seabed, especially in shallow water regions. In this paper, a two-dimensional numerical model is employed to predict local scour around submarine pipelines under water waves in shoaling condition. The motion of water under waves is simulated by solving the Reynolds Averaged Navier-Stokes (RANS) equations. The evolution of the seabed surface near the pipeline is predicted by solving the conservation of the sediment mass, which transport in the water in the forms of bed load and suspended load. The main aim of this study is to investigate the effect of the seabed slope on the scour profiles and scour depth. To achieve this aim, numerical simulations of scour around a pipeline on a flat seabed and on a slope seabed with a slope angle of 15° are conducted for various wave conditions.

scholarly journals Nose-Angle Bridge Piers as Alternative Countermeasures for Local Scour Reduction

2018 ◽  
Vol 13 (2) ◽  
pp. 110-120 ◽  
Author(s):  
Ibtesam Abudallah Habib ◽  
Wan Hanna Melini Wan Mohtar ◽  
Atef Elsaiad ◽  
Ahmed El-Shafie
Keyword(s):  
Froude Number ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Skew Angle ◽  
Flow Angle ◽  
Sediment Size ◽  
Low Froude Number ◽  
Skew Angles ◽  
Depth Reduction

This study investigates the performance nose-angle piers as countermeasures for local scour reduction around piers. Four nose angles were studied, i.e., 90°, 70°, 60° and 45° and tested in a laboratory. The sediment size was fixed at 0.39 mm whereas the flow angle of attack (or skew angle) was varied at four angles, i.e., skew angles, i.e., 0°, 10°, 20° and 30°. Scour reduction was clear when decreasing nose angles and reached maximum when the nose angle is 45°. Increasing the flow velocity and skew angle was subsequently increasing the scour profile, both in vertical and transversal directions. However, the efficiency of nose angle piers was only high at low Froude number less than 0.40 where higher Froude number gives minimal changes in the maximum scour depth reduction. At a higher skew angle, although showed promising maximum scour depth reduction, the increasing pier projected width resulted in the increase of transversal lengths.

The Critical Densimetric Froude Number of Subaqueous Gravity Currents Can Be Non-Unity or Non-Existent

2009 ◽  
Vol 79 (7) ◽  
pp. 479-485 ◽  
Author(s):  
H. Huang ◽  
J. Imran ◽  
C. Pirmez ◽  
Q. Zhang ◽  
G. Chen
Keyword(s):  
Froude Number ◽  
Gravity Currents ◽  
Densimetric Froude Number

scholarly journals Origin of the scaling laws of sediment transport

2017 ◽  
Vol 473 (2197) ◽  
pp. 20160785 ◽  
Author(s):  
Sk Zeeshan Ali ◽  
Subhasish Dey
Keyword(s):  
Sediment Transport ◽  
Froude Number ◽  
Scaling Laws ◽  
Scaling Law ◽  
Bedload Transport ◽  
Inertial Range ◽  
Channel Width ◽  
Densimetric Froude Number ◽  
Relative Roughness ◽  
Contraction Ratio

In this paper, we discover the origin of the scaling laws of sediment transport under turbulent flow over a sediment bed, for the first time, from the perspective of the phenomenological theory of turbulence. The results reveal that for the incipient motion of sediment particles, the densimetric Froude number obeys the ‘(1 +  σ )/4’ scaling law with the relative roughness (ratio of particle diameter to approach flow depth), where σ is the spectral exponent of turbulent energy spectrum. However, for the bedforms, the densimetric Froude number obeys a ‘(1 +  σ )/6’ scaling law with the relative roughness in the enstrophy inertial range and the energy inertial range. For the bedload flux, the bedload transport intensity obeys the ‘3/2’ and ‘(1 +  σ )/4’ scaling laws with the transport stage parameter and the relative roughness, respectively. For the suspended load flux, the non-dimensional suspended sediment concentration obeys the ‘ − Z ’ scaling law with the non-dimensional vertical distance within the wall shear layer, where Z is the Rouse number. For the scour in contracted streams, the non-dimensional scour depth obeys the ‘4/(3 −  σ )’, ‘−4/(3 −  σ )’ and ‘−(1 +  σ )/(3 −  σ )’ scaling laws with the densimetric Froude number, the channel contraction ratio (ratio of contracted channel width to approach channel width) and the relative roughness, respectively.

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