scholarly journals LABORATORY EXPERIMENTS ON THE INFLUENCE OF WIND ON NEARSHORE WAVE BREAKING

1988 ◽  
Vol 1 (21) ◽  
pp. 46
Author(s):  
Scott L. Douglass ◽  
J. Richard Weggel
Keyword(s):  
Wind Direction ◽  
Wave Breaking ◽  
Laboratory Experiments ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Tank ◽  
Zone Width

The influence of wind on nearshore breaking waves was investigated in a laboratory wave tank. Breaker location, geometry, and type depended upon the wind acting on the wave as it broke. Onshore winds tended to cause waves to break earlier, in deeper water, and to spill: offshore winds tended to cause waves to break later, in shallower water, and to plunge. A change in wind direction from offshore to onshore increased the surf zone width by up to 100%. Wind's effect was greatest for waves which were near the transition between breaker types in the absence of wind. For onshore winds, it was observed that microscale breaking can initiate spilling breaking by providing a perturbation on the crest of the underlying wave as it shoals.

Acoustic Study of Wave-Breaking to Enhance the Understanding of Wave Physics

2020 ◽  
Author(s):  
Michael Odzer ◽  
Kristina Francke
Keyword(s):  
Wave Breaking ◽  
Ocean Waves ◽  
Breaking Waves ◽  
Video Data ◽  
Wave Tank ◽  
Potential Applications ◽  
Audio Data ◽  
Video And Audio ◽  
Bubble Sizes ◽  
Laboratory Tank

Abstract The sound of waves breaking on shore, or against an obstruction or jetty, is an immediately recognizable sound pattern which could potentially be employed by a sensor system to identify obstructions. If frequency patterns produced by breaking waves can be reproduced and mapped in a laboratory setting, a foundational understanding of the physics behind this process could be established, which could then be employed in sensor development for navigation. This study explores whether wave-breaking frequencies correlate with the physics behind the collapsing of the wave, and whether frequencies of breaking waves recorded in a laboratory tank will follow the same pattern as frequencies produced by ocean waves breaking on a beach. An artificial “beach” was engineered to replicate breaking waves inside a laboratory wave tank. Video and audio recordings of waves breaking in the tank were obtained, and audio of ocean waves breaking on the shoreline was recorded. The audio data was analysed in frequency charts. The video data was evaluated to correlate bubble sizes to frequencies produced by the waves. The results supported the hypothesis that frequencies produced by breaking waves in the wave tank followed the same pattern as those produced by ocean waves. Analysis utilizing a solution to the Rayleigh-Plesset equation showed that the bubble sizes produced by breaking waves were inversely related to the pattern of frequencies. This pattern can be reproduced in a controlled laboratory environment and extrapolated for use in developing navigational sensors for potential applications in marine navigation such as for use with autonomous ocean vehicles.

Research and Analysis on the Wave Transformation and Irregular Wave Breaking Criterion on the Shore

2016 ◽  
Vol 858 ◽  
pp. 354-358
Author(s):  
Tao You ◽  
Li Ping Zhao ◽  
Zheng Xiao ◽  
Lun Chao Huang ◽  
Xiao Rui Han
Keyword(s):  
Theoretical Model ◽  
Wave Height ◽  
Wave Breaking ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Breaking Wave ◽  
Height Distribution ◽  
Flume Experiments ◽  
Irregular Wave

Within the surf zone which is the region extending from the seaward boundary of wave breaking to the limit of wave uprush, breaking waves are the dominant hydrodynamics acting as the key role for sediment transport and beach profile change. Breaking waves exhibit various patterns, principally depending on the incident wave steepness and the beach slope. Based on the equations of conservation of mass, momentum and energy, a theoretical model for wave transformation in and outside the surf zone was obtained, which is used to calculate the wave shoaling, wave set-up and set down and wave height distributions in and outside the surf zone. The analysis and comparison were made about the breaking point location and the wave height variation caused by the wave breaking and the bottom friction, and about the wave breaking criterion under regular and irregular breaking waves. Flume experiments relating to the regular and irregular breaking wave height distribution across the surf zone were conducted to verify the theoretical model. The agreement is good between the theoretical and experimental results.

scholarly journals COMPARISON OF MODEL AND OBSERVED NEARSHORE CIRCULATION

1978 ◽  
Vol 1 (16) ◽  
pp. 46 ◽  
Author(s):  
James H. Allender ◽  
John D. Ditmars ◽  
Wyman Harrison ◽  
Robert A. Paddock
Keyword(s):  
Wave Breaking ◽  
Input Data ◽  
Lake Michigan ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Characteristics ◽  
Nearshore Circulation ◽  
Water Level Changes ◽  
Local Water ◽  
Offshore Wave

Results from a two-dimensional numerical model for nearshore circulation induced by waves and wind are compared with observations made during two storms at a beach on Lake Michigan. Model-input data include bathymetry, offshore wave characteristics, wind histories, and local water-level changes. The predicted locations of the breaker zone are in rough accord with those observed during the storms. Data for comparison with model results consist of wave and current observations across the surf zone, especially those acquired by using a towed, instrumented sled. The comparisons show that the model often predicts peak currents near the breaker zone quite well, but underestimates the decay of wave height and the strength of longshore currents across the surf zone. Wave breaking on the bar-trough beach structure prevalent in this study apparently is not well represented by the model. An improved breaking criterion, treatment of breaking waves as traveling bores, and inclusion of horizontal mixing of momentum might add to better simulation of surf-zone currents.

scholarly journals VALIDATION OF A BUOYANCY-MODIFIED TURBULENCE MODEL BY NUMERICAL SIMULATIONS OF BREAKING WAVES OVER A FIXED BAR

2018 ◽  
pp. 71
Author(s):  
Brecht Devolder ◽  
Peter Troch ◽  
Pieter Rauwoens
Keyword(s):  
Numerical Simulations ◽  
Wave Breaking ◽  
Surf Zone ◽  
Breaking Waves ◽  
Navier Stokes ◽  
Two Phase ◽  
Numerical Wave Flume ◽  
Wave Flume ◽  
Nearshore Sediment Transport ◽  
Run Up

The surf zone dynamics are governed by important processes such as turbulence generation , nearshore sediment transport , wave run-up and wave overtopping at a coastal structure. During field observations , it is very challenging to measure and quantify wave breaking turbulence . Complementary to experimental laboratory studies in a more controlled environment , numerical simulations are highly suitable to understand and quantify surf zone processes more accurately. In this study, wave propagation and wave breaking over a fixed barred beach profile is investigated using a two­ phase Navier-Stokes flow solver. We show that accurate predictions of the turbulent two-phase flow field require special attention regarding turbulence modelling. The numerical wave flume is implemented in the open­ source OpenFOAM library. The computed results (surface elevations , velocity profiles and turbulence levels) are compared against experimental measurements in a wave flume (van der A et al., 2017) .

scholarly journals Explosive ripple instability due to incipient wave breaking

2019 ◽  
Vol 863 ◽  
pp. 876-892
Author(s):  
Alexei A. Mailybaev ◽  
André Nachbin
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Surf Zone ◽  
Asymptotic Expression ◽  
Nonlinear Effects ◽  
Finite Depth ◽  
Breaking Waves ◽  
Theory Model ◽  
Intrinsic Frequency ◽  
Strong Compression

Considering two-dimensional potential ideal flow with a free surface and finite depth, we study the dynamics of small-amplitude and short-wavelength wavetrains propagating in the background of a steepening nonlinear wave. This can be seen as a model for small ripples developing on the slopes of breaking waves in the surf zone. Using the concept of wave action as an adiabatic invariant, we derive an explicit asymptotic expression for the change of ripple steepness. Through this expression, nonlinear effects are described using the intrinsic frequency and intrinsic gravity along Lagrangian (material) trajectories on a free surface. We show that strong compression near the tip on the wave leads to an explosive ripple instability. This instability may play an important role in the understanding of fragmentation and whitecapping at the surface of breaking waves. Analytical results are confirmed by numerical simulations using a potential theory model.

scholarly journals Numerical Simulations of Non-Breaking, Breaking and Broken Wave Interaction with Emerged Vegetation Using Navier-Stokes Equations

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2561 ◽  
Author(s):  
Xuefeng Zou ◽  
Liangsheng Zhu ◽  
Jun Zhao
Keyword(s):  
Wave Propagation ◽  
Wave Height ◽  
Wave Breaking ◽  
Surf Zone ◽  
Stokes Equations ◽  
Wave Interaction ◽  
Breaking Waves ◽  
Breaking Point ◽  
Navier Stokes ◽  
Inertia Force

Coastal plants can significantly dissipate water wave energy and services as a part of shoreline protection. Using plants as a natural buffer from wave impacts remains an attractive possibility. In this paper, we present a numerical investigation on the effects of the emerged vegetation on non-breaking, breaking and broken wave propagation through vegetation over flat and sloping beds using the Reynolds-average Navier-Stokes (RANS) equations coupled with a volume of fluid (VOF) surface capturing method. The multiphase two-equation k-ω SST turbulence model is adopted to simulate wave breaking and takes into account the effects enhanced by vegetation. The numerical model is validated with existing data from several laboratory experiments. The sensitivities of wave height evolution due to wave conditions and vegetation characteristics with variable bathymetry have been investigated. The results show good agreement with measured data. For non-breaking waves, the wave reflection due to the vegetation can increase wave height in front of the vegetation. For breaking waves, it is shown that the wave breaking behavior can be different when the vegetation is in the surf zone. The wave breaking point is slightly earlier and the wave height at the breaking point is smaller with the vegetation. For broken waves, the vegetation has little effect on the wave height before the breaking point. Meanwhile, the inertia force is important within denser vegetation and is intended to decrease the wave damping of the vegetation. Overall, the present model has good performance in simulating non-breaking, breaking and broken wave interaction with the emerged vegetation and can achieve a better understanding of wave propagation over the emerged vegetation.

scholarly journals SURF ZONE WAVE HEATING BY ENERGY DISSIPATION OF BREAKING WAVES

2018 ◽  
pp. 2 ◽  
Author(s):  
Zhangping Wei ◽  
Robert A. Dalrymple
Keyword(s):  
Internal Energy ◽  
Wave Energy ◽  
Water Waves ◽  
Wave Breaking ◽  
Surf Zone ◽  
Current System ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Conservation Of Energy ◽  
Wave Heating

This study investigates surf zone wave heating due to the dissipation of breaking wave energy by using the Smoothed Particle Hydrodynamics method. We evaluate the surf zone wave heating by examining the increase of internal energy of the system, which is computed based on the conservation of energy. The equivalent temperature profile is calculated based on a simple conversion relationship between energy and temperature. We first examine the surf zone wave heating based on long-crested wave breaking over a planar beach, and we consider spilling breaker and weakly plunging breaker. Numerical results show that breaking of water waves in the surf zone increases the internal energy of water body. Furthermore, the dissipation of incident wave energy is fully converted into the internal energy in a thermally isolated system, confirming the energy conservation of the present numerical approach. It is further found that the long-crested wave breaking generates undertow, which transports the generated wave heating from the surf zone to deep waters. We further carry out numerical experiments to examine surf zone wave heating due to short-crested wave breaking over a beach. The internal energy generation mainly follows the isolated wave breakers, and there is a 3D pattern of wave heating due to the complicated wave breaking process and current system. In general, the magnitude of the generated internal energy or temperature by dissipation of breaking wave energy in the surf zone is relatively small. The present study shows that the generated water temperature is in the order of 10^-3 Kelvin for wave breaking over a typical coastal beach.

scholarly journals BOUSSINESQ MODELLING OF SOLITARY WAVE PROPAGATION, BREAKING, RUNUP AND OVERTOPPING

2011 ◽  
Vol 1 (32) ◽  
pp. 15
Author(s):  
Jana Orszaghova ◽  
Alistair G. L. Borthwick ◽  
Paul H. Taylor
Keyword(s):  
Shallow Water ◽  
Shallow Water Equations ◽  
Wave Breaking ◽  
Laboratory Experiments ◽  
Boussinesq Equations ◽  
Breaking Waves ◽  
One Dimensional ◽  
Nonlinear Shallow Water Equations ◽  
Breaking Parameter ◽  
Surface Profiles

A one-dimensional hybrid numerical model is presented of a shallow-water flume with an incorporated piston paddle. The hybrid model is based on the improved Boussinesq equations by Madsen and Sorensen (1992) and the nonlinear shallow water equations. It is suitable for breaking and non-breaking waves and requires only two adjustable parameters: a friction coefficient and a wave breaking parameter. The applicability of the model is demonstrated by simulating laboratory experiments of solitary waves involving runup at a plane beach and overtopping of a laboratory seawall. The predicted free surface profiles, maximum runup and overtopping volumes agree very well with the measured values.

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