Experimental and numerical investigation of the internal kinematics of a surf-zone plunging breaker

Even m shallow water, only a part of wave energy is lost by turbulent viscosity and bottom friction, most of wave energy transfer takes place m the narrow zone of surf at the shore. Till to the point of breaking, the theoretical conception of an one-phase flow may be applied to the problem. From beginning of breaking, however, the effect of aeration can not be neglected. Prom a simple physical consideration, the sudden reduction of wave height and wave energy inside the surf zone can be explained by the entrainment of air bubbles into the water. Except compression and surface tension effects, most of wave energy is stored at first by the static energy of the air bubbles which are driven into the water. Using idealized assumptions for calculation (uniform concentration of air bubbles a.s.o.), it can be shown that m a plunging breaker the wave energy is dissipated on a very short way (less than on wave length), for a spilling breaker however, this way is of the order of some wave lengths.

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NUMERICAL INVESTIGATION OF PLUNGING BREAKERS OVER A POROUS ARTIFICIAL SURF REEF

Coastal Engineering Proceedings ◽

10.9753/icce.v36.waves.70 ◽

2018 ◽

pp. 70

Author(s):

Bjarne Jensen ◽

Karl-SÃ¸ren Geertsen ◽

Johan RÃ¸nby ◽

Simon B. Mortensen

Keyword(s):

Numerical Model ◽

Numerical Investigation ◽

Breaking Waves ◽

General Analysis ◽

Coastal Protection ◽

Reef Structure ◽

New Locations ◽

Plunging Breaker

This paper presents the results of a numerical investigation of breaking waves over an artificial surf reef (ASR). In the surfing industry, it has become common to establish artificial surf reefs to enhance the surfability at popular surf locations, or to attract surfers to new locations. Besides enhancing the surfing quality, an ASR can also be seen as a submerged detached breakwater, which is a well known type of structure for coastal protection. The construction of an ASR can therefore have the additional purpose of acting as a measure for coastal protection. Hereby the ASR becomes a multi-purpose reef. In this paper, we focus on two aspects of an ASR in relation to the effect of the porous reef: 1) a general analysis of the hydrodynamics of a plunging breaker over a reef, and 2) evaluation of specific parameters for describing the surfability and safety of the plunging breaker. The novelty of the work presented lays in the detailed inclusion of the porous reef structure in a numerical model that is applied for designing and evaluating an ASR.

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Dynamics of surf-zone turbulence in a strong plunging breaker

Coastal Engineering ◽

10.1016/0378-3839(94)00036-w ◽

1995 ◽

Vol 24 (3-4) ◽

pp. 177-204 ◽

Cited By ~ 140

Author(s):

Francis C.K. Ting ◽

James T. Kirby

Keyword(s):

Surf Zone ◽

Plunging Breaker

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FIELD MEASUREMENTS OF IMPACT PRESSURES IN SURF

Coastal Engineering Proceedings ◽

10.9753/icce.v14.103 ◽

1974 ◽

Vol 1 (14) ◽

pp. 103

Author(s):

R.L. Miller ◽

S. Leverette ◽

J. O'Sullivan ◽

J. Tochko ◽

K. Theriault

Keyword(s):

Vertical Distribution ◽

Surf Zone ◽

Field Measurements ◽

Breaking Waves ◽

Breaking Wave ◽

Vertical Array ◽

Qualitative Explanation ◽

The Vertical Distribution ◽

Plunging Breaker ◽

Spilling Breaker

Field measurements were made of the vertical distribution of impact pressures exerted by breaking waves. Four distinct types are recognized and compared. These are near-breaking wave, plunging breaker, spilling breaker and post-breaking bore. The measurements were obtained by placing a 6 foot aluminum flat plate, backed by a cylinder in the surf zone, so that the fiat faced the approaching breakers. Five sensors were placed at one foot intervals on the flat. The sensors consisted of strain gage mounted aluminum diaphragms. Results indicated that impact pressure is significantly influenced by breaker type. The bore generated the largest impact pressures, followed in decreasing order by plunging breaker, spilling breaker and near breaking wave. In the vertical array, the largest impact pressures were recorded at or near the top, except for the bore where the reverse occurred. A qualitative explanation is given of various phenomena associated with impact pressures, by considering breaker mechanics.

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NUMERICAL SIMULATIONS OF SPILLING BREAKING WAVES

Coastal Engineering Proceedings ◽

10.9753/icce.v32.waves.11 ◽

2011 ◽

Vol 1 (32) ◽

pp. 11

Author(s):

Pierre Lubin ◽

Stéphane Glockner ◽

Olivier Kimmoun ◽

Hubert Branger

Keyword(s):

Surf Zone ◽

Early Stage ◽

Air Entrainment ◽

Breaking Waves ◽

Qualitative Comparison ◽

Vorticity Generation ◽

Mesh Grid ◽

The Waves ◽

Plunging Breaker ◽

White Foam

Numerical simulation of spilling breaking waves is still a very challenging aim to achieve since small interface deformations, air entrainment and vorticity generation are involved during the early stage of the breaking of the wave. High mesh grid resolutions and appropriate numerical methods are required to capture accurately the length scales of the complex mechanisms responsible for the start of the breaking (small plunging jet, white foam, etc.). Numerical works usually showed better agreements when simulating plunging breaking waves than the spilling case compared with available experimental data. Kimmoun and Branger (2007) recently experimented surf-zone breaking waves. Detailed pictures showed a short spilling event occurred at the crest of the waves, before degenerating into strong plunging breaker. This work is devoted to the qualitative comparison of our numerical results with the experimental observations, as we will focus on capturing and describing the spilling phase experimented.

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