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 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 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 FIELD MEASUREMENTS OF SHEET FLOW SEDIMENT TRANSPORT IN THE SWASH ZONE

2012 ◽  
Vol 1 (33) ◽  
pp. 78
Author(s):  
Thijs Lanckriet ◽  
Jack A. Puleo ◽  
Gerd Masselink ◽  
Ian Turner ◽  
Daniel Conley ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Field Measurements ◽  
Sediment Concentration ◽  
Shear Stresses ◽  
Concentration Profiles ◽  
Swash Zone ◽  
Pressure Gradients ◽  
Sheet Flow ◽  
Initial Field ◽  
Sediment Mobilization

A newly developed Conductivity Concentration Profiler (CCP), capable of rendering a 29-point sediment concentration profile at 1 mm vertical resolution, was deployed on a macrotidal beach in Perranporth, UK, as part of a comprehensive field study on swash zone hydrodynamics and sediment transport. Initial field results show the occurrence of sheet flow during both the uprush and backwash phases of the swash cycle. Concentration profiles in the sheet flow layer are approximately linear, with a power-law tail at the top of the layer. The data suggest that shear stresses are the dominant forcing for sediment mobilization, but pressure gradients provide a secondary mobilization mechanism.

scholarly journals Modeling swash zone sediment transport at Truc Vert Beach

2012 ◽  
Vol 1 (33) ◽  
pp. 105 ◽  
Author(s):  
Arnold Van Rooijen ◽  
Ad Reniers ◽  
Jaap Van Thiel de Vries ◽  
Chris Blenkinsopp ◽  
Robert McCall
Keyword(s):  
Sediment Transport ◽  
Shallow Water ◽  
Water Level ◽  
Morphological Change ◽  
Shallow Water Equations ◽  
Transport Model ◽  
Early Spring ◽  
Swash Zone ◽  
One Dimensional ◽  
Run Up

A one-dimensional hydrostatic version of the XBeach model (Roelvink et al., 2009) is applied to hindcast swash morphodynamics measured during an accretive, and an erosive tide at Le Truc Vert beach (France) in early spring 2008 (Masselink et. al, 2009; Blenkinsopp et al., 2011). Swash hydrodynamics are solved by applying the nonlinear shallow water equations, and sediment transport rates are obtained from a combined intra-wave Nielsen and Bagnold type transport model. Reasonable predictions of morphological change in the swash were obtained. Nevertheless, the model underpredicts the water level setup and/or wave run-up during the accretive tide, which is hypothesized to be related to 2D-effects.

scholarly journals On Uncertainties in Determination of Sediment Transport Rates in Coastal Regions

2016 ◽  
Vol 63 (4) ◽  
pp. 265-280
Author(s):  
Rafał Ostrowski
Keyword(s):  
Sediment Transport ◽  
Wave Transformation ◽  
Shear Stresses ◽  
Coastal Regions ◽  
Graded Properties ◽  
Physical Phenomena ◽  
Bed Shear Stresses ◽  
Coastal Hydrodynamics ◽  
Sediment Resources

Abstract The paper deals with research uncertainties, difficulties, inaccuracies and unreliabilities related to the modelling of physical phenomena involving coastal lithodynamics. The considerations are focused on processes of wave transformation, wave-driven currents and sediment transport itself. It is shown that possible inaccuracies at individual stages of the modelling of coastal hydrodynamics can lead to serious uncertainties with respect to the ultimate modelling output, namely bed shear stresses and sediment transport rates. These inaccuracies result mostly from arbitrarily assumed parameters and constants. Other modelling biases discussed in the paper comprise simplifications and approximations with respect to sediment resources and size-graded properties, randomness of hydrodynamic impacts, bottom roughness and land-borne factors involved in coastal lithodynamics.

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