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 MEASUREMENT AND MODELING OF SOLITARY WAVE INDUCED BED SHEAR STRESS OVER A ROUGH BED

2012 ◽  
Vol 1 (33) ◽  
pp. 21 ◽  
Author(s):  
Jaya Kumar Seelam ◽  
Tom E Baldock
Keyword(s):  
Shear Stress ◽  
Eddy Viscosity ◽  
Breaking Waves ◽  
Shear Stresses ◽  
Bed Shear Stress ◽  
Eddy Viscosity Model ◽  
Friction Factors ◽  
Convolution Model ◽  
Rough Bed ◽  
Bed Shear Stresses

Bed shear stresses generated by solitary waves were measured using a shear cell apparatus over a rough bed in laminar and transitional flow regimes (~7600 < Re < ~60200). Modeling of bed shear stress was carried out using analytical models employing convolution integration methods forced with the free stream velocity and three eddy viscosity models. The measured wave height to water depth (h/d) ratio varied between 0.13 and 0.65; maximum near- bed velocity varied between 0.16 and 0.47 m/s and the maximum total shear stress (sum of form drag and bed shear) varied between 0.565 and 3.29 Pa. Wave friction factors estimated from the bed shear stresses at the maximum bed shear stress using both maximum and instantaneous velocities showed that there is an increase in friction factors estimated using instantaneous velocities, for non-breaking waves. Maximum positive total stress was approximately 2.2 times larger than maximum negative total stress for non-breaking waves. Modeled and measured positive total stresses are well correlated using the convolution model with an eddy viscosity model analogous to steady flow conditions (nu_t=0.45u* z1; where nu_t is eddy viscosity, u* is shear velocity and z1 is the elevation parameter related to relative roughness). The bed shear stress leads the free stream fluid velocity by approximately 30° for non-breaking waves and by 48° for breaking waves, which is under-predicted by 27% by the convolution model with above mentioned eddy viscosity model.

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.

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.

Possible effects of the 1984 St. Clair River ice jam on bed changes

2015 ◽  
Vol 42 (9) ◽  
pp. 696-703 ◽  
Author(s):  
Tomasz Kolerski ◽  
Hung Tao Shen
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Open Water ◽  
Shear Stresses ◽  
Bed Shear Stress ◽  
Ice Jam ◽  
River Bed ◽  
Bed Changes ◽  
Large Flow ◽  
Bed Shear Stresses

This study examines the possible effect of the record ice jam of 1984 in the St. Clair River on river bed changes and conveyance. Numerical simulations were made to examine the flow and bed shear stresses during the jam formation and release periods. Simulation results indicate that the ice jam in the river did not cause a significant increase in bed shear stress compared to pre- and post-jam open water conditions. The insignificant change on bed shear stress during the ice jam period is the result of the large flow depth and the limited jam thickness. The bed shear stresses are much less than the critical shear stress for bed particle movement. This implies that the jam may not have had a significant impact on the channel conveyance.

scholarly journals Direct Measurements of Bed Shear Stress under Swash Flows on Steep Laboratory Slopes at Medium to Prototype Scales

2019 ◽  
Vol 7 (10) ◽  
pp. 358 ◽  
Author(s):  
Howe ◽  
Blenkinsopp ◽  
Turner ◽  
Baldock ◽  
Puleo
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Shear Stresses ◽  
Bed Shear Stress ◽  
Steady Flows ◽  
Swash Zone ◽  
Wave Runup ◽  
Transport Modelling ◽  
Friction Factors ◽  
Direct Measurements

Robust measurements of bed shear stress under wave runup flows are necessary to inform beachface sediment transport modelling. In this study, direct measurements of swash zone bed shear stress were obtained in medium and prototype-scale laboratory experiments on steep slopes. Peak shear stresses coincided with the arrival of uprush swash fronts and high-resolution measurement of swash surface profiles indicated a consistently seaward sloping swash surface with minimal evidence of a landward sloping swash front. The quadratic stress law was applied to back-calculate time-varying friction factors, which were observed to decrease with increasing Reynolds number on smooth slopes, consistent with theory for steady flows. Additionally, friction factors remained relatively constant throughout the swash cycle (except around flow reversal), with a variation of approximately ±20% from the mean value and with only small differences between uprush and backwash. Measured friction factors were observed to be larger than expected when plotted on the Moody or wave friction diagram for a given Reynolds number and relative roughness, consistent with previous field and laboratory studies at various scales.

scholarly journals RUN-UP OF PERIODIC WAVES ON BEACHES OF NON-UNIFORM SLOPE

1984 ◽  
Vol 1 (19) ◽  
pp. 23 ◽  
Author(s):  
Yoshinobu Ogawa ◽  
Nobuo Shuto
Keyword(s):  
Experimental Data ◽  
Wave Theory ◽  
Breaking Waves ◽  
Lagrangian Description ◽  
Periodic Waves ◽  
Swash Zone ◽  
Slope Method ◽  
Long Wave ◽  
Run Up ◽  
Better Than

Run-up of periodic waves on gentle or non-uniform slopes is discussed. Breaking condition and run-up height of non-breaking waves are derived "by the use of the linear long wave theory in the Lagrangian description. As to the breaking waves, the width of swash zone and the run-up height are-obtained for relatively gentle slopes (less than 1/30), on dividing the transformation of waves into dissipation and swash processes. The formula obtained here agrees with experimental data better than Hunt's formula does. The same procedure is applied to non-uniform slopes and is found to give better results than Saville's composite slope method.

A new model of shoaling and breaking waves. Part 2. Run-up and two-dimensional waves

2019 ◽  
Vol 867 ◽  
pp. 146-194 ◽  
Author(s):  
G. L. Richard ◽  
A. Duran ◽  
B. Fabrèges
Keyword(s):  
Large Scale ◽  
Turbulent Viscosity ◽  
Breaking Waves ◽  
Small Scale ◽  
Two Dimensional ◽  
Numerical Resolution ◽  
Wide Range ◽  
Scale Turbulence ◽  
Run Up ◽  
Averaged Model

We derive a two-dimensional depth-averaged model for coastal waves with both dispersive and dissipative effects. A tensor quantity called enstrophy models the subdepth large-scale turbulence, including its anisotropic character, and is a source of vorticity of the average flow. The small-scale turbulence is modelled through a turbulent-viscosity hypothesis. This fully nonlinear model has equivalent dispersive properties to the Green–Naghdi equations and is treated, both for the optimization of these properties and for the numerical resolution, with the same techniques which are used for the Green–Naghdi system. The model equations are solved with a discontinuous Galerkin discretization based on a decoupling between the hyperbolic and non-hydrostatic parts of the system. The predictions of the model are compared to experimental data in a wide range of physical conditions. Simulations were run in one-dimensional and two-dimensional cases, including run-up and run-down on beaches, non-trivial topographies, wave trains over a bar or propagation around an island or a reef. A very good agreement is reached in every cases, validating the predictive empirical laws for the parameters of the model. These comparisons confirm the efficiency of the present strategy, highlighting the enstrophy as a robust and reliable tool to describe wave breaking even in a two-dimensional context. Compared with existing depth-averaged models, this approach is numerically robust and adds more physical effects without significant increase in numerical complexity.

Critical bed shear for initial movement of sediments on a combined lateral and longitudinal slope

2004 ◽  
Vol 35 (2) ◽  
pp. 153-164 ◽  
Author(s):  
Subhasish Dey
Keyword(s):  
Shear Stress ◽  
Flow Direction ◽  
Side Wall ◽  
Shear Stresses ◽  
Bed Shear Stress ◽  
Conduit Flow ◽  
Sloping Bed ◽  
Stress Ratios ◽  
Closed Conduit ◽  
Initial Movement

An experimental study on critical bed shear-stress for initial movement of non-cohesive sediment particles under a steady-uniform stream flow on a combined lateral (across the flow direction) and longitudinal (streamwise direction) sloping bed is presented. The aim of this paper is to ascertain that the critical bed shear-stress on a combined lateral and longitudinal sloping bed is adequately represented by the product of critical bed shear-stress ratios for lateral and longitudinal sloping beds. Experiments were carried out with closed-conduit flow, in two ducts having a semicircular invert section, with three sizes of sediments. In laboratory flumes, the uniform flow is a difficult – if not impossible – proposition for a steeply sloping channel, and is impossible to obtain in an adversely sloping channel. To avoid this problem, the experiments were conducted with a closed-conduit flow. The critical bed shear-stresses for experimental runs were estimated from side-wall correction. The experimental data agree satisfactorily with the results obtained from the proposed formula.

LARGE SCALE EXPERIMENTS ON EVOLUTION AND RUN-UP OF BREAKING SOLITARY WAVES

2007 ◽  
Vol 01 (03) ◽  
pp. 257-272 ◽  
Author(s):  
KAO-SHU HWANG ◽  
YU-HSUAN CHANG ◽  
HWUNG-HWENG HWUNG ◽  
YI-SYUAN LI
Keyword(s):  
Solitary Wave ◽  
Wave Height ◽  
Solitary Waves ◽  
Water Depth ◽  
Large Scale ◽  
Scale Effects ◽  
Wave Heights ◽  
Run Up ◽  
Hydraulics Laboratory ◽  
The Waves

The evolution and run-up of breaking solitary waves on plane beaches are investigated in this paper. A series of large-scale experiments were conducted in the SUPER TANK of Tainan Hydraulics Laboratory with three plane beaches of slope 0.05, 0.025 and 0.017 (1:20, 1:40 and 1:60). Solitary waves of which relative wave heights, H/h0, ranged from 0.03 to 0.31 were generated by two types of wave-board displacement trajectory: the ramp-trajectory and the solitary-wave trajectory proposed by Goring (1979). Experimental results show that under the same relative wave height, the waveforms produced by the two generation procedures becomes noticeably different as the waves propagate prior to the breaking point. Meanwhile, under the same relative wave height, the larger the constant water depth is, the larger the dimensionless run-up heights would be. Scale effects associated with the breaking process are discussed.

Measurement and modeling of bed shear stress under solitary waves

2011 ◽  
Vol 58 (9) ◽  
pp. 937-947 ◽  
Author(s):  
Jaya Kumar Seelam ◽  
Paul A. Guard ◽  
Tom E. Baldock
Keyword(s):  
Shear Stress ◽  
Solitary Waves ◽  
Bed Shear Stress
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