Numerical model of local scour considering the unsteady sediment inflow and sediment sorting: Application to scour upstream of slit weir

In this paper, the mechanism of local scour around submarine pipeline is studied numerically based on a Renormalized Group (RNG) turbulence model. To validate the numerical model adopted in this paper, the equilibrium profiles of local scour for two cases are simulated and compared with the experimental data. It shows that the RNG turbulence model can give an appropriate prediction for the configuration of equilibrium scour hole, and it is applicable to this situation. The local scour mechanism around submarine pipeline including the flow structure, shear stress distribution and pressure field is then analyzed and compared with experiments. For the further comparison and validation, especially for the flow structure, a numerical model of Large Eddy Simulation (LES) is also developed in this paper. The numerical results of RNG demonstrate that the critical factor governing the equilibrium profile is the seabed shear stress distribution in the case of bed load sediment transport, and the two-equation RNG turbulence model coupled with the law of wall is capable of giving a satisfying estimation for the bed shear stress. Moreover, the piping phenomena due to the great difference of pressure between the upstream and downstream parts of pipeline and the vortex structure around submarine pipeline are also simulated successfully, which are believed to lead to the onset of local scour.

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Numerical Simulation of Local Scour around Three Cylindrical Piles in a Tandem Arrangement

Water ◽

10.3390/w13243623 ◽

2021 ◽

Vol 13 (24) ◽

pp. 3623

Author(s):

Jyh-Haw Tang ◽

Aisyah Dwi Puspasari

Keyword(s):

Numerical Simulation ◽

Experimental Study ◽

Numerical Model ◽

Experimental Studies ◽

Horseshoe Vortex ◽

Local Scour ◽

Scour Depth ◽

Pile Groups ◽

Tandem Arrangement ◽

Flow Acceleration

Scouring is one of the most common potential causes of bridge pile foundation failure, with loss of life, economic and environmental impacts. Comprehensive studies on the numerical simulation of local scour around pile groups are still limited. This paper presents a numerical simulation using Flow-3D software to calculate the maximum sediment scour depth and investigate the mechanism around the groups of three cylinders in a tandem arrangement. A validation using the experimental study was carried out to confirm the reliability of the present numerical model. By using the Van Rijn transport rate equation and RNG k-ε turbulence model, the results of time evolution of scour depth and bed elevation contour show good agreement with the experimental study. The numerical simulation of three cylinders in a tandem arrangement were conducted with pile spacing ratios, G/D of 2 and 3. The local scour is affected by the horseshoe vortex from the downflow driven by the downward pressure gradient and rotates in front of the pile and the high bed shear stress, triggered by flow acceleration. The deepest maximum local scour depth is always obtained by the front pile as a shield pile, followed by the piles behind. The trend of the maximum local scour depth in a tandem arrangement is in accordance with the experimental studies and has a better agreement than previous numerical studies with the same model setup. This means that the numerical model used to simulate pile groups is accurate and capable of calculating the depth of sediment scour.

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Numerical Study of Local Scour around a Submarine Pipeline with a Spoiler Using a Symmetry Boundary Condition

Symmetry ◽

10.3390/sym13101847 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1847

Author(s):

Chuan Zhou ◽

Jianhua Li ◽

Jun Wang ◽

Guoqiang Tang

Keyword(s):

Numerical Model ◽

Stokes Equations ◽

Numerical Study ◽

Lift Coefficient ◽

Numerical Results ◽

Local Scour ◽

Navier Stokes ◽

Scour Depth ◽

Submarine Pipeline ◽

The Mean

A two-dimensional numerical model for solving the Navier–Stokes equations was developed to investigate the local scour around a submarine pipeline with a spoiler. Both the suspended load and the bed load were considered in the present numerical model. The focus of the present study is to investigate the effects of the spoiler length on the hydrodynamic forces on the pipeline and the spoiler as well as the local scour around the submarine pipeline. The corresponding numerical results show that the mean drag coefficients of the pipeline and the spoiler increase with the increase of the spoiler length. As for the mean lift coefficient, a general decreasing trend with the increasing spoiler length is observed for the pipeline. However, the mean lift coefficient of the spoiler first increases and then decreases with the increasing spoiler length. In addition, it is found that a larger spoiler length leads to a deeper scour depth, and an empirical equation was proposed for predicting the non-dimensional scour depth of submarine pipelines with non-dimensional spoiler length based on the numerical results.

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Hydromorphological Numerical Model of the Local Scour Process Around Bridge Piers

Arabian Journal for Science and Engineering ◽

10.1007/s13369-018-3359-z ◽

2018 ◽

Vol 44 (5) ◽

pp. 4183-4199 ◽

Cited By ~ 1

Author(s):

H. Omara ◽

S. M. Elsayed ◽

G. M. Abdeelaal ◽

H. F. Abd-Elhamid ◽

A. Tawfik

Keyword(s):

Numerical Model ◽

Local Scour ◽

Bridge Piers

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Laboratory experiments and numerical model of local scour around submerged sharp crested weirs

Journal of King Saud University - Engineering Sciences ◽

10.1016/j.jksues.2019.01.001 ◽

2020 ◽

Vol 32 (3) ◽

pp. 167-176 ◽

Cited By ~ 6

Author(s):

Thulfikar Razzak Al-Husseini ◽

Abdul-Sahib T. Al-Madhhachi ◽

Zainab A. Naser

Keyword(s):

Numerical Model ◽

Laboratory Experiments ◽

Local Scour

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Orientation of groins for wide and dynamic lowland rivers

World Journal of Engineering ◽

10.1260/1708-5284.11.4.431 ◽

2014 ◽

Vol 11 (4) ◽

pp. 431-440

Author(s):

M. Alauddin ◽

T. Tsujimoto

Keyword(s):

Experimental Data ◽

Numerical Model ◽

Bank Erosion ◽

Main Channel ◽

High Flow ◽

Local Scour ◽

Low Flow ◽

Alluvial Rivers ◽

Lowland Rivers ◽

2D Numerical Model

Alluvial rivers at lowland are very complex in nature. Severe bank erosion at high flow and undue sedimentation at low flow are very common there. Groins are not functioning successfully with their present arrangements. This study investigates various orientations of groins to identify the optimum one for the effective functioning at high flow and low flow both. A 2D numerical model, RIC-Nays is utilized upon confirmation through detailed experimental data. Two types of groins: non-permeable and permeable, and four orientations: 100°, 90°, 80° and 70° to the bank line downstream are considered. Computation reveals that smaller angled groins function better through deepening the main channel and minimizing the local scour, except deposition near bank reduces.

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Numerical Modeling of Local Scour at the Junction of Open Channels in Flow3D Numerical Model

Civil Engineering Journal ◽

10.28991/cej-2016-00000050 ◽

2016 ◽

Vol 2 (9) ◽

pp. 474-483 ◽

Cited By ~ 3

Author(s):

Behnam Shamohamadi ◽

Ali Mehboudi

Keyword(s):

Numerical Model ◽

Numerical Modelling ◽

Relative Error ◽

Hydraulic Properties ◽

Numerical Models ◽

Local Scour ◽

Physical Models ◽

Maximum Relative Error ◽

Flow Properties ◽

Level Profile

At the junction of channels, the two corresponding flows of the main and submain channels are diverted from their main alignment and the form and the flow properties change at the junction. Changes in water level profile and depth of flow, velocity distribution, stagnation zone, constriction of public channel, energy loss and also formation of hydraulic jump are among the most important hydraulic variables in this location. For accurate recognition of hydraulic properties of flow and local scour at the junction of channels, physical models are made and constructed. Setting up a physical model requires many conditions and high costs which sometimes are not justifiable, hence appropriate numerical models could be proposed for such options. In this research using Flow3D numerical model, the numerical modelling of the flow has been performed in 3D form utilizing the available laboratory information which is calibrated and validated and accuracy of the numerical modelling, and the corresponding relative error are determined. The calibration and validation of the numerical model results demonstrate that the maximum relative error of the numerical model when simulating for maximum values of scour depth at the flow junction is equal to 8.2%. Also using the numerical model it was found that with passage of time in numerical model, from .....

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