scholarly journals NUMERICAL STUDY ON THE INFLUENCE OF INFILTRATION ON SWASH HYDRODYNAMICS AND SEDIMENT TRANSPORT IN THE SWASH ZONE

2017 ◽  
pp. 3
Author(s):  
Alejandro M. Hammeken ◽  
Richard R. Simons
Keyword(s):  
Sediment Transport ◽  
Numerical Study ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Swash Zone ◽  
Depth Data ◽  
Run Up ◽  
Opposing Effects ◽  
Phase Stresses ◽  
Bed Shear Stresses

Infiltration and exfiltration processes have a significant influence on the hydrodynamics of the swash zone. Such processes need to be taken into account in the modelling of cross-shore sediment transport and the prediction of beach profile evolution. This paper presents a numerical study of the swash hydrodynamics using a 2D Volume-Averaged Reynolds-Averaged Navier-Stokes model, which was calibrated and validated against new experimental data. The model was used to simulate wave run-up from regular waves over permeable and impermeable fixed slopes. Swash flow velocities and water depth data were obtained from the simulations and used to estimate bed shear stresses at three different locations on the beach slope. The results show that infiltration can have opposing effects on the bed shear stress when compared to equivalent swash on an impermeable slope. During the uprush phase, stresses are directly increased due to boundary layer thinning, whereas, during the backwash phase, there is a significant reduction of flow leading to a decrease in the bed shear stresses.

scholarly journals BEACHFACE EVOLUTION UNDER TWO SWASH EVENTS BY TWO SOLITARY WAVES

2018 ◽  
pp. 16
Author(s):  
Fangfang Zhu ◽  
Nicholas Dodd
Keyword(s):  
Energy Dissipation ◽  
Sediment Transport ◽  
Numerical Simulations ◽  
Morphological Change ◽  
Solitary Waves ◽  
Shear Stresses ◽  
Swash Zone ◽  
Numerical Work ◽  
Shock Interactions ◽  
Bed Shear Stresses

Swash zone morphodynamics is of great signi cance for nearshore morphological change, and it is important to provide reliable numerical prediction for beachface evolution in the swash zone. Most of the numerical work on swash zone morphodynamics carried out so far has focused primarily on beach evolution under one single swash event. In reality, multiple swash events interact, and these swash interactions have been recognised as important in the beachface evolution. Swash-swash interactions leads to energy dissipation, enhanced bed shear stresses and sediment transport (Puleo and Torres- Freyermuth, 2016). In this paper, we investigate the beachface evolution under two swash events using numerical simulations, in which shock-shock interactions are described by dam-break problems.

The swash of solitary waves on a plane beach: flow evolution, bed shear stress and run-up

2015 ◽  
Vol 779 ◽  
pp. 556-597 ◽  
Author(s):  
Nimish Pujara ◽  
Philip L.-F. Liu ◽  
Harry Yeh
Keyword(s):  
Shear Stress ◽  
Solitary Waves ◽  
Large Scale ◽  
Breaking Waves ◽  
Shear Stresses ◽  
Bed Shear Stress ◽  
Swash Zone ◽  
Flow Evolution ◽  
Run Up ◽  
Bed Shear Stresses

The swash of solitary waves on a plane beach is studied using large-scale experiments. Ten wave cases are examined which range from non-breaking waves to plunging breakers. The focus of this study is on the influence of breaker type on flow evolution, spatiotemporal variations of bed shear stresses and run-up. Measurements are made of the local water depths, flow velocities and bed shear stresses (using a shear plate sensor) at various locations in the swash zone. The bed shear stress is significant near the tip of the swash during uprush and in the shallow flow during the later stages of downrush. In between, the flow evolution is dominated by gravity and follows an explicit solution to the nonlinear shallow water equations, i.e. the flow due to a dam break on a slope. The controlling scale of the flow evolution is the initial velocity of the shoreline immediately following waveform collapse, which can be predicted by measurements of wave height prior to breaking, but also shows an additional dependence on breaker type. The maximum onshore-directed bed shear stress increases significantly onshore of the stillwater shoreline for non-breaking waves and onshore of the waveform collapse point for breaking waves. A new normalization for the bed shear stress which uses the initial shoreline velocity is presented. Under this normalization, the variation of the maximum magnitudes of the bed shear stress with distance along the beach, which is normalized using the run-up, follows the same trend for different breaker types. For the uprush, the maximum dimensionless bed shear stress is approximately 0.01, whereas for the downrush, it is approximately 0.002.

scholarly journals RANS MODELLING OF CROSS-SHORE SEDIMENT TRANSPORT AND MORPHODYNAMICS IN THE SWASH-ZONE

2020 ◽  
pp. 14
Author(s):  
Joost Kranenborg ◽  
Geert Campmans ◽  
Niels Jacobsen ◽  
Jebbe van der Werf ◽  
Robert McCall ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Navier Stokes ◽  
Swash Zone ◽  
Rans Equations ◽  
Model Based ◽  
Numerical Studies ◽  
Reynolds Averaged Navier Stokes ◽  
Averaged Models

Most numerical studies of sediment transport in the swash zone use depth-averaged models. However, such models still have difficulty predicting transport rates and morphodynamics. Depth-resolving models could give detailed insight in swash processes but have mostly been limited to hydrodynamic predictions. We present a depth-resolving numerical model, based on the Reynolds Averaged Navier-Stokes (RANS) equations, capable of modelling sediment transport and morphodynamics in the swash zone.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/PB8Vs0LJq88

Numerical Study of Air Gap Response and Wave Impact Load on a Moored Semi-Submersible Platform in Predetermined Irregular Wave Train

2010 ◽  
Author(s):  
Xiufeng Liang ◽  
Jianmin Yang ◽  
Longfei Xiao ◽  
Xin Li ◽  
Jun Li
Keyword(s):  
Impact Load ◽  
Numerical Study ◽  
Wave Train ◽  
Air Gap ◽  
Navier Stokes ◽  
Design Stage ◽  
Wave Impact ◽  
Irregular Wave ◽  
Run Up ◽  
Steep Waves

The importance of understanding air gap response and potential deck impact is well-known in the design stage of semi-submersible platform. The highly non-linear nature of wave elevation around large structures in steep waves makes it difficult to accurately predict wave field under the deck and wave run up along the columns. Present engineering tools for the prediction of air gap response generally based on simplified models. Even the models accounting for nonlinear wave diffraction is not free of uncertainties. A method adopted here couples a Navier-Stokes solver, VOF technique capturing violent free surface and DNV/Seasam predicting motions of moored semi-submersible platform. Air gap response at different locations of the hull was evaluated in predetermined irregular wave train. Wave run up was also measured by wave probes near the columns. Load cells were mounted under the deck of the platform to trace potential deck impact. The predetermined irregular wave train was simulated in a numerical wave tank and verified against physical tank results. Analysis of the air gap response, wave run up and impact loads on the semi-submersible platform were conducted.

scholarly journals Numerical study of cascading dam-break characteristics using SWEs and RANS

2019 ◽  
Vol 20 (1) ◽  
pp. 348-360 ◽  
Author(s):  
Shubing Dai ◽  
Yong He ◽  
Jijian Yang ◽  
Yulei Ma ◽  
Sheng Jin ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Initial Conditions ◽  
Numerical Study ◽  
Air Entrainment ◽  
Dam Break ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Depth Ratio ◽  
Surface Profiles ◽  
Run Up

Abstract This paper investigates the cascading dam-break flood propagation on the downstream sloping channel and reservoir using the shallow water equations (SWEs) and the Reynolds-average Navier-Stokes equations (RANS). The calculated surface profiles, stage hydrographs and maximum run-up heights for 24 sets of initial conditions are elaborately compared with the experimental measurements, which show the SWEs reproduce the wave oscillation evolution and the maximum run-up height inaccurately. The maximum run-up heights calculated by the SWEs are all smaller than those by the RANS and the measured results, the maximum errors are within −10% to −25%, which may predict delay of the downstream dam-break. However, the maximum errors calculated by the RANS are within ±10%. So the RANS predict more accurate results than the SWEs. Additionally, the generation of short waves must be below a certain upstream-to-downstream ‘depth ratio’, roughly the ‘depth ratio’ <2/3 in this study. If the ratio is too high, it is difficult to form a wavy push due to air entrainment and turbulence. The SWEs predict more accurate results for shallow initial depths than deep initial depths. Therefore, the advantage of the RANS can be more obvious for deep initial depths.

Beach-face evolution in the swash zone

2010 ◽  
Vol 661 ◽  
pp. 316-340 ◽  
Author(s):  
DAVID MATTHEW KELLY ◽  
NICK DODD
Keyword(s):  
Sediment Transport ◽  
Swash Zone ◽  
Full Coupling ◽  
Bed Evolution ◽  
Run Up ◽  
The One ◽  
Offshore Transport ◽  
Bed Mobility ◽  
Upper Third ◽  
Fully Coupled

We investigate swash on an erodible beach using the one-dimensional shallow-water equations fully coupled to a bed-evolution (Exner) equation. In particular, the dam-break/bore-collapse initial condition of Shen & Meyer (J. Fluid Mech., vol. 16, 1963, pp. 113–125) and Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) is investigated using a numerical model based on the method of characteristics. A sediment-transport formula (cubic in velocity u: Au3) is used here; this belongs to a family of sediment-transport formulae for which Pritchard & Hogg (Coastal Engng, vol. 52, 2005, pp. 1–23) showed that net sediment transport under the Shen & Meyer (1963) bore collapse is offshore throughout the swash zone when a non-erodible bed is considered. It is found that full coupling with the beach, although still resulting in the net offshore transport of sediment throughout the swash zone, leads to a large reduction in the net offshore transport of sediment from the beach face. This is particularly true for the upper third of the swash zone. Moreover, in contradistinction to swash flows over non-erodible beds, flows over erodible beaches are unique to the bed mobility and porosity under consideration; this has very important implications for run-up predictions. The conclusion is that it is essential to consider full coupling of water and bed motions (i.e. full morphodynamics) in order to understand and predict sediment transport in the swash, regardless of other physical effects (e.g. turbulence, infiltration, pre-suspended sediment, etc.).

scholarly journals Numerical Study of the Hydrodynamics of Waves and Currents and Their Effects in Pier Scouring

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2256 ◽  
Author(s):  
Matias Quezada ◽  
Aldo Tamburrino ◽  
Yarko Niño
Keyword(s):  
Experimental Data ◽  
Relative Velocity ◽  
Numerical Study ◽  
Numerical Data ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Numeric Modeling ◽  
Waves And Currents ◽  
Cylindrical Piles ◽  
The Waves

The scour around cylindrical piles due to codirectional and opposite waves and currents is studied with Reynolds Averaged Navier–Stokes (RANS) equations via REEF3D numeric modeling. First, a calibration process was made through a comparison with the experimental data available in the literature. Subsequently, not only the hydrodynamics, but also the expected scour for a set of scenarios, which were defined by the relative velocity of the current ( U C W ), were studied numerically. The results obtained show that the hydrodynamics around the pile for codirectional or opposite waves and currents not have significant differences when analyzed in terms of their velocities, vorticities and mean shear stresses, since the currents proved to be more relevant compared to the net flow. The equilibrium scour, estimated by the extrapolation of the numerical data with the equation by Sheppard, enabled us to estimate values close to those described in the literature. From this extrapolation, it was verified that the dimensionless scour would be less when the waves and currents are from opposite directions. The U C W parameter is an indicator used to adequately measure the interactions between the currents and waves under conditions of codirectional flow. Nevertheless, it is recommended to modify this parameter for currents and waves in opposite directions, and an equation is proposed for this case.

scholarly journals Boundary-layer hydrodynamics and bedload sediment transport in oscillating water tunnels

2010 ◽  
Vol 667 ◽  
pp. 48-84 ◽  
Author(s):  
DAVID GONZALEZ-RODRIGUEZ ◽  
OLE SECHER MADSEN
Keyword(s):  
Boundary Layer ◽  
Sediment Transport ◽  
Water Tunnel ◽  
Shear Stresses ◽  
Engineering Research ◽  
Wave Flume ◽  
Experimental Facilities ◽  
Bedload Sediment ◽  
Analytical Expressions ◽  
Bed Shear Stresses

Oscillating water tunnels are experimental facilities commonly used in coastal engineering research. They are intended to reproduce near-bed hydrodynamic and sediment transport phenomena at a realistic scale. In an oscillating water tunnel, a piston generates an oscillatory motion that propagates almost instantaneously to the whole tunnel; consequently, flow is uniform along the tunnel, unlike the propagating wave motion in the sea or in a wave flume. This results in subtle differences between the boundary-layer hydrodynamics of an oscillating water tunnel and of a propagating wave, which may have a significant effect in the resulting sediment transport. In this paper, we present a zeroth-order analytical model of the turbulent boundary-layer hydrodynamics in an oscillating water tunnel. By using a time-varying eddy viscosity and by accounting for the constraints arising from the tunnel's geometry, the model predicts the oscillating water tunnel hydrodynamics and yields analytical expressions to compute bed shear stresses for asymmetric and skewed waves, both in the absence or presence of an imposed current. These expressions are applied to successfully quantify bedload sediment transport in oscillating water tunnel experiments.

scholarly journals NUMERICAL AND EXPERIMENTAL DESCRIPTION OF THE FLOW, BOUNDARY LAYER AND BED EVOLUTION IN BORE-DRIVEN SWASH ON A COARSE SEDIMENT BEACH

2012 ◽  
Vol 1 (33) ◽  
pp. 33 ◽  
Author(s):  
Riccardo Briganti ◽  
Nicholas Dodd ◽  
Dubravka Pokrajac ◽  
Tom O'Donoghue
Keyword(s):  
Sediment Transport ◽  
Shallow Water Equations ◽  
Swash Zone ◽  
Coupled Numerical Model ◽  
Stress Prediction ◽  
Bed Evolution ◽  
Run Up ◽  
Momentum Integral ◽  
The University ◽  
Fully Coupled

The paper presents the results of a comparison between a fully coupled numerical model for the hydro- and morphodynamics of the swash zone. The model solves simultaneously the Non-Linear Shallow Water Equations and the Exner equation for the bed updates. The model uses the simple Grass formula for the sediment transport and the momentum integral method for the bottom shear stress prediction. The laboratory tests were carried out at the University of Aberdeen swash facility and aimed at studying the hydrodynamics and sediment transport of a single, bore-generated swash event. The comparison is carried out in terms of water depth and horizontal velocity (depth average and profiles) and sediment transport. The model performs well in predicting these quantities, above all during the run-up.

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