scholarly journals TOWARD A SIMPLE MODEL OF THE WAVE BREAKING TRANSITION REGION IN SURF ZONES

1986 ◽  
Vol 1 (20) ◽  
pp. 72 ◽  
Author(s):  
David R. Basco ◽  
Takao Yamashita
Keyword(s):  
Simple Model ◽  
Transition Region ◽  
Surf Zone ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Zone Model ◽  
Similarity Parameter ◽  
Set Up ◽  
Linear Growth Model ◽  
Semi Empirical

Breaking waves undergo a transition from oscillatory, irrotational motion, to highly rotational (turbulent) motion with some particle translation. On plane or monotonically decreasing beach profiles, this physically takes place in such a way that the mean water level remains essentially constant within the transition region. Further shoreward a rapid set-up takes place within the inner, bore-like region. The new surf zone model of Svendsen (1984) begins at this transition point and the new wave there contains a trapped volume of water within the surface roller moving with the wave speed. This paper describes a simple model over the transition zone designed to match the Svendsen (1984) model at the end of the transition region. It uses a simple, linear growth model for the surface roller area development and semi-empirical model for the variation of the wave shape factor. Breaking wave type can vary from spilling through plunging as given by a surf similarity parameter. The model calculates the wave height decrease and width of the transition region for all breaker types on plane or monotonically depth decreasing beaches.

scholarly journals STABILITY OF A SAND BED UNDER BREAKING WAVES

1974 ◽  
Vol 1 (14) ◽  
pp. 45 ◽  
Author(s):  
Ole Secher Madsen
Keyword(s):  
Pressure Gradient ◽  
Surf Zone ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Light Weight ◽  
Loss Of Stability ◽  
Vertical Flow ◽  
Sufficient Magnitude ◽  
The Stability ◽  
Bed Material

The possible effect on the stability of a porous sand bed of the flow induced within the bed during the passage of near-breaking or breaking waves is considered. It is found that the horizontal flow rather than the vertical flow within the bed may affect its stability. An approximate analysis, used in geotechnical computations of slope stability, indicates that a momentary bed failure is likely to occur during the passage of the steep front slope of a near-breaking wave. Experimental results for the pressure gradient along the bottom under near-breaking waves are presented. These results indicate that the pressure gradient is indeed of sufficient magnitude to cause the momentary failure suggested by the theoretical analysis. The loss of stability of the bed material due to the flow induced within the bed itself may affect the amount of material set in motion during the passage of a near-breaking or breaking wave, in particular, in model tests employing light weight bed material. The failure mechanism considered here is also used as the basis for a hypothesis for the depth of disturbance of the bed in the surf zone. The flow induced in a porous bed is concluded to be an important mechanism which should be considered when dealing with the wave-sediment interaction in the surf zone.

scholarly journals ENERGY LOSS AND SET-UP DUE TO BREAKING OF RANDOM WAVES

1978 ◽  
Vol 1 (16) ◽  
pp. 32 ◽  
Author(s):  
J.A. Battjes ◽  
J.P.F.M. Janssen
Keyword(s):  
Wave Height ◽  
Dissipation Rate ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Height Distribution ◽  
Random Waves ◽  
Dissipation Of Energy ◽  
Wave Height Distribution ◽  
Set Up ◽  
Local Depth

A description is given of a model developed for the prediction of the dissipation of energy in random waves breaking on a beach. The dissipation rate per breaking wave is estimated from that in a bore of corresponding height, while the probability of occurrence of breaking waves is estimated on the basis of a wave height distribution with an upper cut-off which in shallow water is determined mainly by the local depth. A comparison with measurements of wave height decay and set-up, on a plane beach and on a beach with a bar-trough profile, indicates that the model is capable of predicting qualitatively and quantitatively all the main features of the data.

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 COMPUTATION OF LONGSHORE CURRENTS

1974 ◽  
Vol 1 (14) ◽  
pp. 40 ◽  
Author(s):  
Ivar G. Jonsson ◽  
Ove Skovgaard ◽  
Torben S. Jacobsen
Keyword(s):  
Surf Zone ◽  
Numerical Algorithms ◽  
Field Measurements ◽  
Breaking Waves ◽  
Bottom Friction ◽  
Rip Currents ◽  
Longshore Current ◽  
Lateral Mixing ◽  
Set Up ◽  
The Given

The steady state profile of the longshore current induced by regular, obliquely incident, breaking waves, over a bottom with arbitrary parallel bottom contours, is predicted. A momentum approach is adopted. The wave parameters must be given at a depth outside the surf zone, where the current velocity is very small. The variation of the bottom roughness along the given bottom profile must be prescribed in advance. Depth refraction is included also in the calculation of wave set-down and set-up. Current refraction and rip-currents are excluded. The model includes two new expressions, one for the calculation of the turbulent lateral mixing, and one for the turbulent bottom friction. The term for the bottom friction is non-linear. Rapid convergent numerical algorithms are described for the solution of the governing equations. The predicted current profiles are compared with laboratory experiments and field measurements. For a plane sloping bottom, the influence of different eddy viscosities and constant values of bottom roughness is examined.

scholarly journals MODIFICATION OF WAVE SPECTRA ON THE CONTINENTAL SHELF AND IN THE SURF ZONE

2011 ◽  
Vol 1 (8) ◽  
pp. 2 ◽  
Author(s):  
Charles L. Bretschneider
Keyword(s):  
Continental Shelf ◽  
Shallow Water ◽  
Surf Zone ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Breaking Waves ◽  
Bottom Friction ◽  
Breaking Wave ◽  
Predominant Period ◽  
Significant Period

This paper discusses the problem pertaining to the modification of the wave spectrum over the continental shelf. Modification factors include bottom friction, percolation, refraction, breaking waves, ocean currents, and regeneration of wind waves in shallow water, among other factors. A formulation of the problem is presented but no general solution is made, primarily because of lack of basic data. Several special solutions are presented based on reasonable assumptions. The case for a steep continental shelf with parallel bottom contours and wave crests parallel to the coast and for which bottom friction is neglected has been investigated. For this case it is found that the predominant period shifts toward longer periods. The implication is, for example, that the significant periods observed along the U. S. Pacific coast are longer than those which would be observed several miles westward over deep water. The case for a gentle continental shelf with parallel bottom contour and wave crests parallel to the coast and for which bottom friction is important has also been investigated. For this case it is found that the predominant period shifts toward shorter periods as the water depth decreases. The implication is, for example, that the significant periods observed in the shallow water over the continental shelf are shorter than those which would be observed beyond the continental slope. In very shallow water, because shoaling becomes important, a secondary peak appears at higher periods. The joint distribution of wave heights and wave periods is required in order to determine the most probable maximum breaking wave, which can be of lesser height than the most probable maximum non-breaking wave. In very shallow water the most probable maximum breaking wave which first occurs would be governed by the breaking depth criteria, whereas in deepwater wave steepness can also be a governing factor. It can be expected that in very shallow water the period of the most probable maximum breaking wave should be longer than the significant period; and for deeper water the period of the most probable maximum breaking wave can be less than the significant period.

scholarly journals HYDRODYNAMICS UNDER LARGE-SCALE REGULAR AND BICHROMATIC BREAKING WAVES

2018 ◽  
pp. 90
Author(s):  
Dominic Van der A ◽  
Joep Van der Zanden ◽  
Ming Li ◽  
James Cooper ◽  
Simon Clark ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Surf Zone ◽  
Experimental Studies ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Small Scale ◽  
Breaking Wave ◽  
Wave Flume ◽  
Cfd Models

Multiphase CFD models recently have proved promising in modelling cross‐shore sediment transport and morphodynamics (Jacobsen et al 2014). However, modelling breaking wave turbulence remains a major challenge for these models, because it occurs at very different spatial and temporal length scales and involves the interaction between surface generated turbulence and turbulence generated in the bottom boundary layer. To an extent these challenges arise from a lack of appropriate experimental data, since most previous experimental studies involved breaking waves at small-scale, and have not permitted investigation of the turbulent boundary layer processes. Moreover, most existing studies have concentrated on regular waves, thereby excluding the flow and turbulence dynamics occurring at wave group time-scales under irregular waves within the surf zone. These limitations motivated a new experiment in the large-scale CIEM wave flume in Barcelona involving regular and irregular waves. The experiment was conducted in May-July 2017 within the HYDRALAB+ Transnational Access project HYBRID.

Longshore motion due to an obliquely incident wave group

1983 ◽  
Vol 137 ◽  
pp. 273-284 ◽  
Author(s):  
S. C. Ryrie
Keyword(s):  
Wave Equations ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Group ◽  
Edge Waves ◽  
Obliquely Incident ◽  
Long Wave ◽  
Circulation Cell ◽  
A Cell ◽  
Set Up

We consider longshore motion generated within the surf zone by obliquely incident breaking waves, and seek to describe the effect on such motion of variations, caused by wave grouping, in the incident longshore momentum flux. The effects of associated variations in set-up are not considered.We use the linear long-wave equations to describe the motion resulting from the longshore momentum contained in a wave group. This consists of a succession of edge waves which disperse along the beach, and, for the example considered, an eventual steady circulation cell at the position of the wave group. We suggest that such a cell is always likely to be formed if the wave group is sufficiently localized, and that higher-modenumber edge waves are more likely to be excited.We find timescales for the dispersal of the edge waves, and for the decay, due to bottom friction, of the circulation cell: we suggest that the latter may more generally be used, as a timescale for the effect of friction on longshore motion.

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.

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