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1
Bulanov, S. V., F. Pegoraro, A. M. Pukhov e A. S. Sakharov. "Transverse-Wake Wave Breaking". Physical Review Letters 78, n. 22 (2 giugno 1997): 4205–8. http://dx.doi.org/10.1103/physrevlett.78.4205.
Testo completo
2
Hwang, Paul A., Delun Xu e Jin Wu. "Breaking of wind-generated waves: measurements and characteristics". Journal of Fluid Mechanics 202 (maggio 1989): 177–200. http://dx.doi.org/10.1017/s002211208900114x.
Testo completoAbstract (sommario):
A method of using local wave properties to provide a detailed description of breakings in a random wave field is developed. These properties, derived through the Hilbert transform, include the angular frequency, phase velocity, and surface-velocity components. The breaking characteristics are presented, including the probability of breaking, its time- and lengthscales, its intensity, and the phase of its inception. The time- and lengthscales, of breaking events were found to be linearly proportional to the corresponding scales of underlying waves, and to indicate that the breaking region is geometrically similar. Consistent results were obtained from temporal and spatial measurements. Finally, on the basis of these results we have evaluated geometric and kinematic criteria for identifying breaking waves.
3
Li, Changfei, Fuping Gao e Lijing Yang. "Breaking-Wave Induced Transient Pore Pressure in a Sandy Seabed: Flume Modeling and Observations". Journal of Marine Science and Engineering 9, n. 2 (5 febbraio 2021): 160. http://dx.doi.org/10.3390/jmse9020160.
Testo completoAbstract (sommario):
Previous studies on wave-induced pore pressure in a porous seabed mainly focused on non-breaking regular waves, e.g., Airy linear waves or Stokes non-linear waves. In this study, breaking-wave induced pore pressure response in a sandy seabed was physically simulated with a large wave flume. The breaking-wave was generated by superimposing a series of longer waves onto the foregoing shorter waves at a specified location. Water surface elevations and the corresponding pore pressure in the process of wave breaking were measured simultaneously at three typical locations, i.e., at the rear, just at, and in front of the wave breaking location. Based on test results, characterization parameters are proposed for the wave surface elevations and the corresponding pore-pressures. Flume observations indicate that the wave height was greatly diminished during wave breaking, which further affected the pore-pressure responses. Moreover, the measured values of the characteristic time parameters for the breaking-wave induced pore-pressure are larger than those for the free surface elevation of breaking-waves. Under the action of incipient-breaking or broken waves, the measured values of the amplitude of transient pore-pressures are generally smaller than the predicted results with the analytical solution by Yamamoto et al. (1978) for non-breaking regular waves with equivalent values of characteristic wave height and wave period.
4
Tejerina-Risso, J., e P. Le Gal. "Around the Cusp Singularity and the Breaking of Waves". Leonardo 47, n. 1 (febbraio 2014): 80–82. http://dx.doi.org/10.1162/leon_a_00687.
Testo completoAbstract (sommario):
WAVES is an “Art-Science” project on water surface waves. The authors aim to visualize the behaviour of water waves during their evolution: generation, focusing and breaking. Relying on the general property of waves to focus when properly generated or reflected, the authors use a parabolically shaped wave maker to focus water waves in a region of the water surface called the Huygens cusp in optics and then record these breakings using a fast video camera. A novel and spectacular vision of wave breakings is obtained when playing at slow speed.
5
Seyama, Akira, e Akira Kimura. "THE MEASURED PROPERTIES OF IRREGULAR WAVE BREAKING AND WAVE HEIGHT CHANGE AFTER BREAKING ON THE SLOPE". Coastal Engineering Proceedings 1, n. 21 (29 gennaio 1988): 29. http://dx.doi.org/10.9753/icce.v21.29.
Testo completoAbstract (sommario):
Wave height change of the zero-down-cross waves on uniform slopes were examined experimentally. The properties of shoaling, breaking and decay after breaking for a total of about 4,000 irregular waves of the Pierson-Moskowitz type on 4 different slopes (1/10, 1/20, 1/30 and 1/50) were investigated. The shoaling property of the zero-down-cross waves can be approximated by the linear wave theory. However, the properties of breaking and decay after breaking differ considerably from those for periodic waves. The wave height water depth ratio (H/d) at the breaking point for the zero-down-cross waves is about 30% smaller than that for periodic waves on average despite the slopes. Wave height decay after breaking also differs from that for periodic waves and can be classified into three regions, i.e. shoaling, plunging and bore regions. Experimental equations for the breaking condition and wave height change after breaking are proposed in the study. A new definition of water depth for the zero-crossing wave analysis which can reduce the fluctuation in the plotted data is also proposed.
6
You, Tao, Li Ping Zhao, Zheng Xiao, Lun Chao Huang e Xiao Rui Han. "Research and Analysis on the Wave Transformation and Irregular Wave Breaking Criterion on the Shore". Applied Mechanics and Materials 858 (novembre 2016): 354–58. http://dx.doi.org/10.4028/www.scientific.net/amm.858.354.
Testo completoAbstract (sommario):
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.
7
Knobler, Sagi, Ewelina Winiarska, Alexander Babanin e Dan Liberzon. "Wave breaking probabilities under wind forcing in open sea and laboratory". Physics of Fluids 34, n. 3 (marzo 2022): 032122. http://dx.doi.org/10.1063/5.0084276.
Testo completoAbstract (sommario):
Water wave breaking represents one of the most arduous problems in fluid mechanics. Understanding the process of wave breaking and developing an ability to quantify the associated energy losses and redistribution are critical across a wide range of coastal oceanic applications, maritime navigation, and climate and hydrodynamic research. Naturally, waves become steeper toward the inception of breaking; however, there is still a lack of unanimity regarding the relationship between breaking probability statistics and wave steepness. Here, we present a detailed investigation of breaking vs non-breaking statistics estimated using a recently developed method for accurate detection of breaking waves, based on the phase-time approach to identify breaking-associated patterns in the instantaneous frequency variations of surface elevation fluctuations. The findings are based on data collected both in the open sea and in a laboratory wind wave flume. An in-depth examination of celerities and steepnesses of breaking and non-breaking waves is presented. The analysis, which involved wave-by-wave examination, produced skewed Gaussian-like steepness histograms, revealing that non-breaking waves and breaking waves can reach steeper profiles, above the Stokes limit. All extreme steepness values were investigated and are presented here.
8
Kishi, Tsutomu. "TRANSFORMATION, BREAKING AND RUN-UP OF A LONG WAVE OF FINITE HEIGHT". Coastal Engineering Proceedings 1, n. 8 (29 gennaio 2011): 5. http://dx.doi.org/10.9753/icce.v8.5.
Testo completoAbstract (sommario):
On studying the transformation, breaking and run-up of a relatively steep wave of a short period, the theory for waves of permanent type has given us many fruitful results. However, the theory gradually loses its applicability as a wave becomes flat, since a considerable deformation of the wave profile is inevitable in its propagation.
In § 1, a discussion concerning the transformation of a long wave in a channel of variable section is presented based on the non-linear shallow water theory. Approximate solutions obtained by G. B. Whitham's method (1958) are shown. Further, some brief considerations are given to the effects of bottom friction on wave transformation.
In § 2, breaking of a long wave is discussed. Breakings on a uniformly sloping beach and on a beach of parabolic profile are considered and the effects of beach profile on breaking are clarified. Finally in § 3, experimental results on wave run-up over l/30 slope are described in comparing with the Kaplan's results.
9
Banner, Michael L. "The influence of wave breaking on the surface pressure distribution in wind—wave interactions". Journal of Fluid Mechanics 211 (febbraio 1990): 463–95. http://dx.doi.org/10.1017/s0022112090001653.
Testo completoAbstract (sommario):
In reviewing the current status of our understanding of the mechanisms underlying wind-wave generation, it is apparent that existing theories and models are not applicable to situations where the sea surface is disturbed by breaking waves, and that the available experimental data on this question are sparse. In this context, this paper presents the results of a detailed study of the effects of wave breaking on the aerodynamic surface pressure distribution and consequent wave-coherent momentum flux, as well as its influence on the total wind stress.Two complementary experimental configurations were used to focus on the details and consequences of the pressure distribution over breaking waves under wind forcing. The first utilized a stationary breaking wave configuration and confirmed the presence of significant phase shifting, due to air flow separation effects, between the surface pressure and surface elevation (and slope) distributions over a range of wind speeds. The second configuration examined the pressure distribution, recorded at a fixed height above the mean water surface just above the crest level, over short mechanically triggered waves which were induced to break almost continuously under wind forcing. This allowed a very detailed comparison of the form drag for actively breaking waves and for waves of comparable steepness just prior to breaking (‘incipiently’ breaking waves). For these propagating steep-wave experiments, the pressure phase shifts and distributions closely paralleled the stationary configuration findings. Moreover, a large increase (typically 100%) in the total windstress was observed for the breaking waves, with the increase corresponding closely to the comparably enhanced form drag associated with the actively breaking waves.In addition to further elucidating some fundamental features of wind-wave interactions for very steep wind waves, this paper provides a useful data set for future model calculations of wind flow over breaking waves. The results also provide the basis for a parameterization of the wind input source function applicable for a wave field undergoing active breaking, an important result for numerical modelling of short wind waves.
10
Dao, M. H., H. Xu, E. S. Chan e P. Tkalich. "Modelling of tsunami wave run-up, breaking and impact on vertical wall by SPH method". Natural Hazards and Earth System Sciences Discussions 1, n. 3 (22 giugno 2013): 2831–57. http://dx.doi.org/10.5194/nhessd-1-2831-2013.
Testo completoAbstract (sommario):
Abstract. Accurate predictions of wave run-up and run-down are important for coastal impact assessment of relatively long waves such as tsunami or storm waves. Wave run-up is, however, a complex process involving nonlinear build-up of the wave front, intensive wave breaking and strong turbulent flow, making the numerical approximation challenging. Recent advanced modeling methodologies could help to overcome these numerical challenges. For a demonstration, we study run-up of non-breaking and breaking solitary waves on vertical wall using two methods, the enhanced Smoothed Particle Hydrodynamics (SPH) method and the traditional non-breaking nonlinear model Tunami-N2. The Tunami-N2 model fails to capture the evolution of steep waves at the proximity of breaking that observed in the experiments. Whereas, the SPH method successfully simulate the wave propagation, breaking, impact on structure and the reform and breaking processes of wave run-down. The study also indicates that inadequate approximation of the wave breaking could lead to significant under-predictions of wave height and impact pressure on structures. The SPH model shows potential applications for accurate impact assessments of wave run-up onto coastal structures.
11
Dao, M. H., H. Xu, E. S. Chan e P. Tkalich. "Modelling of tsunami-like wave run-up, breaking and impact on a vertical wall by SPH method". Natural Hazards and Earth System Sciences 13, n. 12 (23 dicembre 2013): 3457–67. http://dx.doi.org/10.5194/nhess-13-3457-2013.
Testo completoAbstract (sommario):
Abstract. Accurate predictions of wave run-up and run-down are important for coastal impact assessment of relatively long waves such as tsunami or storm waves. Wave run-up is, however, a complex process involving nonlinear build-up of the wave front, intensive wave breaking and strong turbulent flow, making the numerical approximation challenging. Recent advanced modelling methodologies could help to overcome these numerical challenges. For a demonstration, we study run-up of non-breaking and breaking solitary waves on a vertical wall using two methods, an enhanced smoothed particle hydrodynamics (SPH) method and the traditional non-breaking nonlinear model Tunami-N2. The Tunami-N2 model fails to capture the evolution of steep waves at the proximity of breaking that was observed in the experiments. Whereas the SPH method successfully simulates the wave propagation, breaking, impact on structure and the reform and breaking processes of wave run-down. The study also indicates that inadequate approximation of the wave breaking could lead to significant under-predictions of wave height and impact pressure on structures. The SPH model shows potential applications for accurate impact assessments of wave run-up on to coastal structures.
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Deike, Luc, Stephane Popinet e W. Kendall Melville. "Capillary effects on wave breaking". Journal of Fluid Mechanics 769 (25 marzo 2015): 541–69. http://dx.doi.org/10.1017/jfm.2015.103.
Testo completoAbstract (sommario):
We investigate the influence of capillary effects on wave breaking through direct numerical simulations of the Navier–Stokes equations for a two-phase air–water flow. A parametric study in terms of the Bond number, $\mathit{Bo}$, and the initial wave steepness, ${\it\epsilon}$, is performed at a relatively high Reynolds number. The onset of wave breaking as a function of these two parameters is determined and a phase diagram in terms of $({\it\epsilon},\mathit{Bo})$ is presented that distinguishes between non-breaking gravity waves, parasitic capillaries on a gravity wave, spilling breakers and plunging breakers. At high Bond number, a critical steepness ${\it\epsilon}_{c}$ defines the onset of wave breaking. At low Bond number, the influence of surface tension is quantified through two boundaries separating, first gravity–capillary waves and breakers, and second spilling and plunging breakers; both boundaries scaling as ${\it\epsilon}\sim (1+\mathit{Bo})^{-1/3}$. Finally the wave energy dissipation is estimated for each wave regime and the influence of steepness and surface tension effects on the total wave dissipation is discussed. The breaking parameter $b$ is estimated and is found to be in good agreement with experimental results for breaking waves. Moreover, the enhanced dissipation by parasitic capillaries is consistent with the dissipation due to breaking waves.
13
Ermakov, Stanislav, Vladimir Dobrokhotov, Irina Sergievskaya e Ivan Kapustin. "Suppression of Wind Ripples and Microwave Backscattering Due to Turbulence Generated by Breaking Surface Waves". Remote Sensing 12, n. 21 (5 novembre 2020): 3618. http://dx.doi.org/10.3390/rs12213618.
Testo completoAbstract (sommario):
The role of wave breaking in microwave backscattering from the sea surface is a problem of great importance for the development of theories and methods on ocean remote sensing, in particular for oil spill remote sensing. Recently it has been shown that microwave radar return is determined by both Bragg and non-Bragg (non-polarized) scattering mechanisms and some evidence has been given that the latter is associated with wave breaking, in particular, with strong breaking such as spilling or plunging. However, our understanding of mechanisms of the action of strong wave breaking on small-scale wind waves (ripples) and thus on the radar return is still insufficient. In this paper an effect of suppression of radar backscattering after strong wave breaking has been revealed experimentally and has been attributed to the wind ripple suppression due to turbulence generated by strong wave breaking. The experiments were carried out in a wind wave tank where a frequency modulated wave train of intense meter-decimeter-scale surface waves was generated by a mechanical wave maker. The wave train was compressed according to the gravity wave dispersion relation (“dispersive focusing”) into a short-wave packet at a given distance from the wave maker. Strong wave breaking with wave crest overturning (spilling) occurred for one or two highest waves in the packet. Short decimeter-centimeter-scale wind waves were generated at gentle winds, simultaneously with the long breaking waves. A Ka-band scatterometer was used to study microwave backscattering from the surface waves in the tank. The scatterometer looking at the area of wave breaking was mounted over the tank at a height of about 1 m above the mean water level, the incidence angle of the microwave radiation was about 50 degrees. It has been obtained that the radar return in the presence of short wind waves is characterized by the radar Doppler spectrum with a peak roughly centered in the vicinity of Bragg wave frequencies. The radar return was strongly enhanced in a wide frequency range of the radar Doppler spectrum when a packet of long breaking waves arrived at the area irradiated by the radar. After the passage of breaking waves, the radar return strongly dropped and then slowly recovered to the initial level. Measurements of velocities in the upper water layer have confirmed that the attenuation of radar backscattering after wave breaking is due to suppression of short wind waves by turbulence generated in the breaking zone. A physical analysis of the effect has been presented.
14
LI, YING, e FREDRIC RAICHLEN. "Non-breaking and breaking solitary wave run-up". Journal of Fluid Mechanics 456 (9 aprile 2002): 295–318. http://dx.doi.org/10.1017/s0022112001007625.
Testo completoAbstract (sommario):
The run-up of non-breaking and breaking solitary waves on a uniform plane beach connected to a constant-depth wave tank was investigated experimentally and numerically. If only the general characteristics of the run-up process and the maximum run-up are of interest, for the case of a breaking wave the post-breaking condition can be simplified and represented as a propagating bore. A numerical model using this bore structure to treat the process of wave breaking and subsequent shoreward propagation was developed. The nonlinear shallow water equations (NLSW) were solved using the weighted essentially non-oscillatory (WENO) shock capturing scheme employed in gas dynamics. Wave breaking and post-breaking propagation are handled automatically by this scheme and ad hoc terms are not required. A computational domain mapping technique was used to model the shoreline movement. This numerical scheme was found to provide a relatively simple and reasonably good prediction of various aspects of the run-up process. The energy dissipation associated with wave breaking of solitary wave run-up (excluding the effects of bottom friction) was also estimated using the results from the numerical model.
15
Zou, Xuefeng, Liangsheng Zhu e Jun Zhao. "Numerical Simulations of Non-Breaking, Breaking and Broken Wave Interaction with Emerged Vegetation Using Navier-Stokes Equations". Water 11, n. 12 (4 dicembre 2019): 2561. http://dx.doi.org/10.3390/w11122561.
Testo completoAbstract (sommario):
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.
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JIANG, LEI, MARC PERLIN e WILLIAM W. SCHULTZ. "Period tripling and energy dissipation of breaking standing waves". Journal of Fluid Mechanics 369 (25 agosto 1998): 273–99. http://dx.doi.org/10.1017/s0022112098001785.
Testo completoAbstract (sommario):
We examine the dynamics of two-dimensional steep and breaking standing waves generated by Faraday-wave resonance. Jiang et al. (1996) found a steep wave with a double-peaked crest in experiments and a sharp-crested steep wave in computations. Both waveforms are strongly asymmetric in time and feature large superharmonics. We show experimentally that increasing the forcing amplitude further leads to breaking waves in three recurrent modes (period tripling): sharp crest with breaking, dimpled or flat crest with breaking, and round crest without breaking. Interesting steep waveforms and period-tripled breaking are related directly to the nonlinear interaction between the fundamental mode and the second temporal harmonic. Unfortunately, these higher-amplitude phenomena cannot be numerically modelled since the computations fail for breaking or nearly breaking waves. Based on the periodicity of Faraday waves, we directly estimate the dissipation due to wave breaking by integrating the support force as a function of the container displacement. We find that the breaking events (spray, air entrainment, and plunging) approximately double the wave dissipation.
17
Kukulka, Tobias, Tetsu Hara e Stephen E. Belcher. "A Model of the Air–Sea Momentum Flux and Breaking-Wave Distribution for Strongly Forced Wind Waves". Journal of Physical Oceanography 37, n. 7 (1 luglio 2007): 1811–28. http://dx.doi.org/10.1175/jpo3084.1.
Testo completoAbstract (sommario):
Abstract Under high-wind conditions, breaking surface waves likely play an important role in the air–sea momentum flux. A coupled wind–wave model is developed based on the assumption that in the equilibrium range of surface wave spectra the wind stress is dominated by the form drag of breaking waves. By conserving both momentum and energy in the air and also imposing the wave energy balance, coupled equations are derived governing the turbulent stress, wind speed, and the breaking-wave distribution (total breaking crest length per unit surface area as a function of wavenumber). It is assumed that smaller-scale breaking waves are sheltered from wind forcing if they are in airflow separation regions of longer breaking waves (spatial sheltering effect). Without this spatial sheltering, exact analytic solutions are obtained; with spatial sheltering asymptotic solutions for small- and large-scale breakers are derived. In both cases, the breaking-wave distribution approaches a constant value for large wavenumbers (small-scale breakers). For low wavenumbers, the breaking-wave distribution strongly depends on wind forcing. If the equilibrium range model is extended to the spectral peak, the model yields the normalized roughness length (Charnock coefficient) of growing seas, which increases with wave age and is roughly consistent with earlier laboratory observations. However, the model does not yield physical solutions beyond a critical wave age, implying that the wind input to the wave field cannot be dominated by breaking waves at all wavenumbers for developed seas (including field conditions).
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Wang, David W., e Hemantha W. Wijesekera. "Observations of Breaking Waves and Energy Dissipation in Modulated Wave Groups". Journal of Physical Oceanography 48, n. 12 (dicembre 2018): 2937–48. http://dx.doi.org/10.1175/jpo-d-17-0224.1.
Testo completoAbstract (sommario):
AbstractIt has been recognized that modulated wave groups trigger wave breaking and generate energy dissipation events on the ocean surface. Quantitative examination of wave-breaking events and associated turbulent kinetic energy (TKE) dissipation rates within a modulated wave group in the open ocean is not a trivial task. To address this challenging topic, a set of laboratory experiments was carried out in an outdoor facility, the Oil and Hazardous Material Simulated Environment Test Tank (203 m long, 20 m wide, 3.5 m deep). TKE dissipation rates at multiple depths were estimated directly while moving the sensor platform at a speed of about 0.53 m s−1 toward incoming wave groups generated by the wave maker. The largest TKE dissipation rates and significant whitecaps were found at or near the center of wave groups where steepening waves approached the geometric limit of waves. The TKE dissipation rate was O(10−2) W kg−1 during wave breaking, which is two to three orders of magnitude larger than before and after wave breaking. The enhanced TKE dissipation rate was limited to a layer of half the wave height in depth. Observations indicate that the impact of wave breaking was not significant at depths deeper than one wave height from the surface. The TKE dissipation rate of breaking waves within wave groups can be parameterized by local wave phase speed with a proportionality breaking strength coefficient dependent on local steepness. The characterization of energy dissipation in wave groups from local wave properties will enable a better determination of near-surface TKE dissipation of breaking waves.
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Kuznetsov, Sergey, Yana Saprykina e Valentina Volkova. "DEPENDENCIES OF BREAKING TYPE, BREAKING CRITERIA AND ENERGY DISSIPATION ON AMPLITUDE-PHASE FREQUENCY STRUCTURE OF WAVES". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 72. http://dx.doi.org/10.9753/icce.v36.papers.72.
Testo completoAbstract (sommario):
Type of wave breaking - plunging or spilling - depends on symmetry of waves. The spilling waves are asymmetric against horizontal axis and are practically symmetric against vertical axis so the phase shift between first and second nonlinear harmonics (or biphase) is close to zero. The plunging breaking waves have larger asymmetry against vertical axis, (biphase is close to -pi/2), and near symmetric on horizontal axis (close to saw-toothed form). Non-linear wave transformation influences on depth-induced wave breaking. Breaking index depends on relation of wave energy in frequency range of second nonlinear harmonics to wave energy in frequency range of main harmonic and on biphase. The dissipation rate of spilling breaking waves energy quadratically depends on frequency, while in plunging breaking, this dependency is practically linear for all frequencies.
20
Rhee, Shin Hyung, e Fred Stern. "RANS Model for Spilling Breaking Waves". Journal of Fluids Engineering 124, n. 2 (28 maggio 2002): 424–32. http://dx.doi.org/10.1115/1.1467078.
Testo completoAbstract (sommario):
A RANS model for spilling breaking waves is developed, which can be implemented with ship hydrodynamics RANS CFD codes. The model is based on the Cointe & Tulin theory of steady breakers. The breaker cross section is assumed triangular with maximum height determined by the theoretical/experimental linear relationship with following wave height. Pressure and velocity boundary conditions are imposed on the dividing streamline between the breaker and underlying flow based on the hydrostatic and mixing layer models. An iterative solution procedure provides a unique solution for specified breaking criteria and simulation conditions. The model is implemented using CFDSHIP-IOWA and validated using spilling breaking wave benchmark data for two-dimensional submerged hydrofoils. As with other current RANS codes, wave elevations are under-predicted. However, for the first time in literature, the breaking wave wake is predicted. Results for total head, mean velocities, and Reynolds stresses are in agreement with available spilling breaking wave benchmark data.
21
Pujianiki, Ni Nyoman. "Numerical Simulation of Breaking Waves in a Wave Group by SPH". Applied Mechanics and Materials 776 (luglio 2015): 151–56. http://dx.doi.org/10.4028/www.scientific.net/amm.776.151.
Testo completoAbstract (sommario):
Smoothed Particle Hydrodynamic (SPH) numerical model is used to investigate wave group effects at breaking and after breaking by comparing individual waves in a group with equivalent regular waves. Regular wave break almost at the same position and with the same wave height. Meanwhile in a wave group, the wave breaks in the variant positions and with variant wave heights. These phenomena cause the breaking point to be more scattered in a wave group rather than in regular waves. Return flow due to the breaking of wave groups appears more significant and is extended to the full depth in the surf zone rather than in regular waves. Swash oscillations of the wave group in the surf zone appear irregular. Meanwhile in regular waves, swash oscillations are almost constant.
22
Liu, Shan, e Zhenyu Liu. "Influence of Currents on the Breaking Wave Forces Acting on Monopiles over an Impermeable Slope". Sustainability 15, n. 1 (22 dicembre 2022): 129. http://dx.doi.org/10.3390/su15010129.
Testo completoAbstract (sommario):
It is known that the wave breaking process is significantly affected by a current, but little attention has been paid to the effect of wave–current interaction on the breaking wave forces acting on a monopile. This study presented a total of 88 flume tests, among which solitary and regular breaking waves were generated with a following current. The waves propagated over an impermeable slope and induced impulsive loads on a vertical monopile. The moments on the monopile were measured utilizing a high-precision load cell, and the effect of current velocities on the peak moment was analyzed. Test results indicate that there was an obvious nonlinear effect between breaking waves and a following current. For solitary waves, a following current accelerated the breaking process, leading to an increase by 274.21% at maximum in breaking wave forces. However, for regular waves, both the wave heights and the reversing flow were restricted with the increasing velocity of a following current, delaying the wave breaking process; under the regular test conditions, the moment on the pile decreased by 65.25% at maximum.
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Amron. "NOISE CHARACTERISTICS OF SEA WAVES BASED ON ITS HEIGHT, PERIOD AND BREAKING WAVES". JOURNAL ONLINE OF PHYSICS 5, n. 2 (25 luglio 2020): 28–34. http://dx.doi.org/10.22437/jop.v5i2.9509.
Testo completoAbstract (sommario):
ABSTRACT
Wave sound is one of the sources of ambient noise in the waters which causes the role of sound as a transmission medium of information and communication becomes disrupted. The characteristics of wave noise can be influenced by their parameters, such as height and period of the waves and breaking waves. The study aimed to determine the characteristics of noise (intensity, frequency, pulse duration and interval duration) of waves based on its height, periods and breaking waves. Data acquisition for sound wave is obtained by hydrophones, visual of wave from CCTV cameras, and wave parameters is determined from ADCP data. Sound characteristics based its height, period and breaking waves were analyzed by Kruskal-Wallis analysis. The intensity of noise is affected by all wave parameters, while the pulse duration is significantly influenced by the changes in height and wave period, and the breaking waves velocity. Frequency of noise is only impacted by the breaking wave height. Other noise characteristics, the interval duration is not significantly influenced by all wave parameters.
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Schwendeman, Michael S., e Jim Thomson. "Sharp-Crested Breaking Surface Waves Observed from a Ship-Based Stereo Video System". Journal of Physical Oceanography 47, n. 4 (aprile 2017): 775–92. http://dx.doi.org/10.1175/jpo-d-16-0187.1.
Testo completoAbstract (sommario):
AbstractA new ship-based stereo video system is used to observe breaking ocean waves (i.e., whitecaps) as three-dimensional surfaces evolving in time. First, the stereo video measurements of all waves (breaking and nonbreaking) are shown to compare well with statistical parameters from traditional buoy measurements. Next, the breaking waves are detected based on the presence of whitecap foam, and the geometry of these waves is investigated. The stereo measurements show that the whitecaps are characterized by local extremes of surface slope, though the larger-scale, crest-to-trough steepness of these waves is unremarkable. Examination of 103 breaking wave profiles further demonstrates the pronounced increase in the local wave steepness near the breaking crest, as estimated using a Hilbert transform. These crests are found to closely resemble the sharp corner of the theoretical Stokes limiting wave. Results suggest that nonlinear wave group dynamics are a key mechanism for breaking, as the phase speed of the breaking waves is slower than predicted by the linear dispersion relation. The highly localized and transient steepness, along with the deviation from linear phase speed, explains the inability of conventional wave buoys to observe the detailed geometry of breaking waves.
25
Wei, Zhangping, e Robert A. Dalrymple. "SPH MODELING OF VORTICITY GENERATION BY SHORT-CRESTED WAVE BREAKING". Coastal Engineering Proceedings, n. 35 (23 giugno 2017): 1. http://dx.doi.org/10.9753/icce.v35.waves.1.
Testo completoAbstract (sommario):
This study investigates vorticity generation by short-crested wave breaking by using the mesh-free Smoothed Particle Hydrodynamics model, GPUSPH. The short-crested waves are created by generating intersecting wave trains in a numerical wave basin with a beach. The capability of GPUSPH to simulate short-crested waves is first validated by laboratory measurements. Then we examine short-crested wave breaking with two incident wave heights H = 0.2 m and 0.3 m. The larger incident wave breaks at the toe of the planar beach, while the smaller incident wave breaks above the planar beach. The breaking wave profile, current field, nearshore circulation pattern, and vertical vorticity field due to short-crested wave breaking are carefully compared between two incident waves.
26
Aggarwal, Ankit, Mayilvahanan Alagan Chella, Arun Kamath e Hans Bihs. "NUMERICAL INVESTIGATION OF BREAKING IRREGULAR WAVES OVER A SUBMERGED BAR WITH CFD". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 43. http://dx.doi.org/10.9753/icce.v36.waves.43.
Testo completoAbstract (sommario):
The study of breaking irregular waves is of great practical interest, because of the waves found in the nature. Regular waves are seldom found in the field. Irregular waves can be viewed as the superposition of a number of regular waves (wave components) with the different frequencies and the amplitudes. The breaking process for irregular waves is more complex as compared to breaking regular waves. The energy transfer between the individual wave components of different frequencies also takes place during the breaking process. Due to this, the spectral characteristics of the incident wave spectrum change during the breaking process. The main purpose of the study is to investigate the hydrodynamics during the interaction of breaking irregular waves with a submerged bar.
27
Babanin, Alexander V., Michael L. Banner, Ian R. Young e Mark A. Donelan. "Wave-Follower Field Measurements of the Wind-Input Spectral Function. Part III: Parameterization of the Wind-Input Enhancement due to Wave Breaking". Journal of Physical Oceanography 37, n. 11 (1 novembre 2007): 2764–75. http://dx.doi.org/10.1175/2007jpo3757.1.
Testo completoAbstract (sommario):
Abstract This is the third in a series of papers describing wave-follower observations of the aerodynamic coupling between wind and waves on a large shallow lake during the Australian Shallow Water Experiment (AUSWEX). It focuses on the long-standing problem of the aerodynamic consequences of wave breaking on the wind–wave coupling. Direct field measurements are reported of the influence of wave breaking on the wave-induced pressure in the airflow over water waves, and hence the energy flux to the waves. The level of forcing, measured by the ratio of wind speed to the speed of the dominant (spectral peak) waves, covered the range of 3–7. The propagation speeds of the dominant waves were limited by the water depth and the waves were correspondingly steep. These measurements allowed an assessment of the magnitude of any breaking-induced enhancement operative for these field conditions and provided a basis for parameterizing the effect. Overall, appreciable levels of wave breaking occurred for the strong wind forcing conditions that prevailed during the observational period. Associated with these breaking wave events, a significant phase shift is observed in the local wave-coherent surface pressure. This produced an enhanced wave-coherent energy flux from the wind to the waves with a mean value of 2 times the corresponding energy flux to the nonbreaking waves. It is proposed that the breaking-induced enhancement of the wind input to the waves can be parameterized by the sum of the nonbreaking input and the contribution due to the breaking probability.
28
Riedel, Hans Peter, e Anthony Paul Byrne. "RANDOM BREAKING WAVES HORIZONTAL SEABED". Coastal Engineering Proceedings 1, n. 20 (29 gennaio 1986): 68. http://dx.doi.org/10.9753/icce.v20.68.
Testo completoAbstract (sommario):
According to wave theories the depth limited wave height over a horizontal seabed has a wave height to water depth ratio (H/d) of about 0.8. Flume experiments with monochromatic waves over a horizontal seabed have failed to produce H/d ratios greater than 0.55. However designers still tend to use H/d 0.8 for their design waves. Experiments have been carried out using random wave trains in the flume over a horizontal seabed. These experiments have shown that the limiting H/d ratio of 0.55 applies equally well to random waves.
29
Doyle, James D., e Carolyn A. Reynolds. "Implications of Regime Transitions for Mountain-Wave-Breaking Predictability". Monthly Weather Review 136, n. 12 (1 dicembre 2008): 5211–23. http://dx.doi.org/10.1175/2008mwr2554.1.
Testo completoAbstract (sommario):
Abstract A suite of high-resolution two-dimensional ensemble simulations are used to investigate the predictability of mountain waves, wave breaking, and downslope windstorms. For relatively low hills and mountains, perturbation growth is weak and ensemble spread is small. Gravity waves and wave breaking associated with higher mountains exhibit rapid perturbation growth and large ensemble variance. Near the regime boundary between mountain waves and wave breaking, a bimodal response is apparent with large ensemble variance. Several ensemble members exhibit a trapped wave response and others reveal a hydraulic jump and large-amplitude breaking in the stratosphere. The bimodality of the wave response brings into question the appropriateness of commonly used ensemble statistics, such as the ensemble mean, in these situations. Small uncertainties in the initial state within observational error limits result in significant ensemble spread in the strength of the downslope wind speed, wave breaking, and wave momentum flux. These results indicate that the theoretical transition across the regime boundary for gravity wave breaking can be interpreted as a finite-width or blurred transition zone from a practical predictability standpoint.
30
Vollestad, P., A. A. Ayati e A. Jensen. "Experimental investigation of intermittent airflow separation and microscale wave breaking in wavy two-phase pipe flow". Journal of Fluid Mechanics 878 (18 settembre 2019): 796–819. http://dx.doi.org/10.1017/jfm.2019.660.
Testo completoAbstract (sommario):
We perform an experimental analysis of co-current, stratified wavy pipe flow, with the aim of investigating the effect of small scale wave breaking (microscale breaking) on the airflow. Particle image velocimetry is applied simultaneously in the gas and liquid phases. Active wave breaking is identified by high levels of vorticity on the leeward side of individual waves, and the statistics of the airflow above breaking and non-breaking waves are extracted from the gas-phase velocity fields. Keeping the liquid superficial velocity constant ($U_{sl}=0.1~\text{m}~\text{s}^{-1}$), we consider two experimental cases of different gas flow rates. The lowest flow rate ($U_{sg}=1.85~\text{m}~\text{s}^{-1}$) is slightly higher than the onset of microscale breaking, while the higher flow rate ($U_{sg}=2.20~\text{m}~\text{s}^{-1}$) is within the regime where wave breaking is observed to be frequent, and the root-mean-square interface elevation $\unicode[STIX]{x1D702}_{rms}$ is independent of gas flow rate. Results show that for the lowest gas flow rate considered, active wave breaking has a stabilizing effect on the airflow above the waves, reducing the sheltered region on the leeward side of the wave and the turbulence above the wave crest compared with non-breaking waves at similar steepness. At the higher gas flow rate the effect of active wave breaking is found to be small, and the main geometrical properties of the waves are found to dominate the evolution of the separated flow region.
31
Woods, Bryan K., e Ronald B. Smith. "Short-Wave Signatures of Stratospheric Mountain Wave Breaking". Journal of the Atmospheric Sciences 68, n. 3 (1 marzo 2011): 635–56. http://dx.doi.org/10.1175/2010jas3634.1.
Testo completoAbstract (sommario):
Abstract Recent stratospheric mountain wave measurements over the Sierra Nevada indicate that downgoing secondary waves may be common or even ubiquitous in large wave events. Because of their short wavelengths, they may dominate the vertical velocity field near the tropopause, and they give a remote indicator of wave breaking farther aloft. Using a 2D numerical model, the authors have simulated the secondary wave generation process with qualitative agreement in the wave location, phase speed, wavelength (i.e., 10–20 km), and amplitude. A key to the analysis was the use of Morlet wavelet cross spectra on both the observational and simulated fields. Several characteristics of the simulated secondary waves were unexpected. First, the secondary waves are generated with good efficiency, approaching 20% of the primary upgoing wave momentum flux. Second, whereas most of the secondary waves are downward, the shorter components reflect upward from the tropopause, giving a kind of lee wave trapping in the lower stratosphere. Long waves are also observed propagating upward and downward away from the wave breaking region. Third, the phase speed of the secondary waves is nearly zero so the Eliassen–Palm relationship between momentum and energy flux is satisfied. While the 2D results are robust to grid size and subgrid parameterization, an extension of the modeling to three dimensions is disappointing. The secondary waves’ amplitudes in the 3D runs are much smaller than observed.
32
Zappa, Christopher J., Michael L. Banner, Russel P. Morison e Sophia E. Brumer. "On the Variation of the Effective Breaking Strength in Oceanic Sea States". Journal of Physical Oceanography 46, n. 7 (luglio 2016): 2049–61. http://dx.doi.org/10.1175/jpo-d-15-0227.1.
Testo completoAbstract (sommario):
AbstractA spectral framework for quantifying the geometric/kinematic and dynamic/energetic properties of breaking ocean waves was proposed by Phillips in 1985. Phillips assumed a constant breaking strength coefficient to link the kinematic/geometric breaking crest properties to the associated excess energy and momentum fluxes from the waves to the upper ocean. However, a scale-dependent (spectral) breaking strength coefficient is needed, but is unavailable from measurements. In this paper, the feasibility of a parametric mean effective breaking strength coefficient valid for a wide range of sea states is investigated. All available ocean breaking wave datasets were analyzed and complemented with wave model behavior. Robust evidence is found supporting a single linear parameter relationship between the effective breaking strength and wave age or significant wave steepness. Envisaged applications for the effective breaking strength are described.
33
Liu, Zhenyu, Zhen Guo, Yuzhe Dou e Fanyu Zeng. "Characteristics of Breaking Wave Forces on Piles over a Permeable Seabed". Journal of Marine Science and Engineering 9, n. 5 (12 maggio 2021): 520. http://dx.doi.org/10.3390/jmse9050520.
Testo completoAbstract (sommario):
Most offshore wind turbines are installed in shallow water and exposed to breaking waves. Previous numerical studies focusing on breaking wave forces generally ignored the seabed permeability. In this paper, a numerical model based on Volume-Averaged Reynolds Averaged Navier–Stokes equations (VARANS) is employed to reveal the process of a solitary wave interacting with a rigid pile over a permeable slope. Through applying the Forchheimer saturated drag equation, effects of seabed permeability on fluid motions are simulated. The reliability of the present model is verified by comparisons between experimentally obtained data and the numerical results. Further, 190 cases are simulated and the effects of different parameters on breaking wave forces on the pile are studied systematically. Results indicate that over a permeable seabed, the maximum breaking wave forces can occur not only when waves break just before the pile, but also when a “secondary wave wall” slams against the pile, after wave breaking. With the initial wave height increasing, breaking wave forces will increase, but the growth can decrease as the slope angle and permeability increase. For inclined piles around the wave breaking point, the maximum breaking wave force usually occurs with an inclination angle of α = −22.5° or 0°.
34
Chalikov, Dmitry, e Alexander V. Babanin. "Simulation of Wave Breaking in One-Dimensional Spectral Environment". Journal of Physical Oceanography 42, n. 11 (1 novembre 2012): 1745–61. http://dx.doi.org/10.1175/jpo-d-11-0128.1.
Testo completoAbstract (sommario):
Abstract Results of numerical investigations, based on full dynamic equations, are presented for wave breaking in a one-dimensional environment with a wave spectrum. The breaking is defined as a process of irreversible collapse of an individual wave in physical space, and the incipient breaker is a wave that reached a dynamic condition of the limiting stability where the collapse has not started yet but is inevitable. The main attention is paid to documenting the evolution of different wave characteristics before the breaking commences. It is shown that the breaking is a localized process that rapidly develops in space and time. No single characteristic, such as wave steepness, wave height, and asymmetry, can serve as a predictor of the incipient breaking. The process of breaking is intermittent; it happens spontaneously and is individually unpredictable. The evolution of geometric, kinematic, and dynamic characteristics of the breaking wave describes the process of breaking itself rather than indicating an imminent breaking. It is shown that the criterion of breaking, valid for the breaking due to modulation instability in one-dimensional waves trains, is not universal if applied to the conditions of spectral environment. In this context, the development of algorithms for parameterization of breaking for wave prediction models and for direct wave simulations is more important.
35
Irisov, Vladimir, e Alexander Voronovich. "Numerical Simulation of Wave Breaking". Journal of Physical Oceanography 41, n. 2 (1 febbraio 2011): 346–64. http://dx.doi.org/10.1175/2010jpo4442.1.
Testo completoAbstract (sommario):
Abstract The wave breaking events in a continuous spectrum of surface gravity waves are investigated numerically in 2D within a framework of the potential motion model. It is claimed that the major physical mechanism leading to wave breaking is “squeezing” of relatively short waves by the surface currents due to longer waves (the “concertina” effect), which causes the shorter waves to steepen and become unstable. It is demonstrated that locations of the breaking events are well correlated with the maximum of local current convergence, although slightly worse correlation of the locations with the local steepness of undulating surface cannot reliably exclude the latter mechanism either. It is found also that the breaking events are very rare for random surfaces with a root-mean-square (RMS) current gradient below a threshold value of about 1 s−1. The process of wave breaking was investigated by two numerical codes. One of them is based on approximation of continuous media with a discrete Hamiltonian system, which can be integrated in time very efficiently and accurately but is limited to single-valued profiles. The other is the Laplacian approach, which can explicitly exhibit the overturning of plunging breakers. Study of the discrete system shows that wave breaking is associated with the explosive growth of a certain spatially localized mode of the system.
36
Barthelemy, X., M. L. Banner, W. L. Peirson, F. Fedele, M. Allis e F. Dias. "On a unified breaking onset threshold for gravity waves in deep and intermediate depth water". Journal of Fluid Mechanics 841 (23 febbraio 2018): 463–88. http://dx.doi.org/10.1017/jfm.2018.93.
Testo completoAbstract (sommario):
We revisit the classical but as yet unresolved problem of predicting the breaking onset of 2D and 3D irrotational gravity water waves. Based on a fully nonlinear 3D boundary element model, our numerical simulations investigate geometric, kinematic and energetic differences between maximally tall non-breaking waves and marginally breaking waves in focusing wave groups. Our study focuses initially on unidirectional domains with flat bottom topography and conditions ranging from deep to intermediate depth (depth to wavelength ratio from 1 to 0.2). Maximally tall non-breaking (maximally recurrent) waves are clearly separated from marginally breaking waves by their normalised energy fluxes localised near the crest tip region. The initial breaking instability occurs within a very compact region centred on the wave crest. On the surface, this reduces to the local ratio of the energy flux velocity (here the fluid velocity) to the crest point velocity for the tallest wave in the evolving group. This provides a robust threshold parameter for breaking onset for 2D wave packets propagating in uniform water depths from deep to intermediate. Further targeted study of representative cases of the most severe laterally focused 3D wave packets in deep and intermediate depth water shows that the threshold remains robust. These numerical findings for 2D and 3D cases are closely supported by our companion observational results. Warning of imminent breaking onset is detectable up to a fifth of a carrier wave period prior to a breaking event.
37
HULT, ERIN L., CARY D. TROY e JEFFREY R. KOSEFF. "The breaking of interfacial waves at a submerged bathymetric ridge". Journal of Fluid Mechanics 637 (17 settembre 2009): 45–71. http://dx.doi.org/10.1017/s0022112009008040.
Testo completoAbstract (sommario):
The breaking of periodic progressive two-layer interfacial waves at a Gaussian ridge is investigated through laboratory experiments. Length scales of the incident wave and topography are used to parameterize when and how breaking occurs. Qualitative observations suggest both shear and convection play a role in the instability of waves breaking at the ridge. Simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) measurements are used to calculate high resolution, two-dimensional velocity and density fields from which the local gradient Richardson number Rig is calculated. The transition to breaking occurred when 0.2 ≤ Rig ≤ 0.4. In these wave-ridge breaking events, the destabilizing effects of waves steepening in shallow layers may be responsible for breaking at higher Rig than for similar waves breaking through shear instability in deep water (Troy & Koseff, J. Fluid Mech., vol. 543, 2005b, p. 107). Due to the effects of unsteadiness, nonlinear shoaling and flow separation, the canonical Rig > 0.25 is not sufficient to predict the stability of interfacial waves. A simple model is developed to estimate Rig in waves between finite depth layers using scales of the incident wave scale and topography. The observed breaking transition corresponds with a constant estimated value of Rig from the model, suggesting that interfacial shear plays an important role in initial wave instability. For wave amplitudes above the initial breaking transition, convective breaking events are also observed.
38
Kukulka, Tobias, e Tetsu Hara. "The Effect of Breaking Waves on a Coupled Model of Wind and Ocean Surface Waves. Part II: Growing Seas". Journal of Physical Oceanography 38, n. 10 (1 ottobre 2008): 2164–84. http://dx.doi.org/10.1175/2008jpo3962.1.
Testo completoAbstract (sommario):
Abstract This is the second part of a two-part investigation of a coupled wind and wave model that includes the enhanced form drag of breaking waves. The model is based on the wave energy balance and the conservation of air-side momentum and energy. In Part I, coupled nonlinear advance–delay differential equations were derived, which govern the wave height spectrum, the distribution of breaking waves, and vertical air side profiles of the turbulent stress and wind speed. Numeric solutions were determined for mature seas. Here, numeric solutions for a wide range of wind and wave conditions are obtained, including young, strongly forced wind waves. Furthermore, the “spatial sheltering effect” is introduced so that smaller waves in airflow separation regions of breaking longer waves cannot be forced by the wind. The solutions strongly depend on the wave height curvature spectrum at high wavenumbers (the “threshold saturation level”). As the threshold saturation level is reduced, the effect of breaking waves becomes stronger. For young strongly forced waves (laboratory conditions), breaking waves close to the spectral peak dominate the wind input and previous solutions of a model with only input to breaking waves are recovered. Model results of the normalized roughness length are generally consistent with previous laboratory and field measurements. For field conditions, the wind stress depends sensitively on the wave height spectrum. The spatial sheltering may modify the number of breaking shorter waves, in particular, for younger seas.
39
Kjeldsen, Soren Peter, Alf Torum e Robert G. Dean. "WAVE FORCES ON VERTICAL PILES CAUSED BY 2- AND 3-DIMENSIONAL BREAKING WAVES". Coastal Engineering Proceedings 1, n. 20 (29 gennaio 1986): 142. http://dx.doi.org/10.9753/icce.v20.142.
Testo completoAbstract (sommario):
The present study deals with analysis of results from a new experiment in which local wave forces on a vertical pile penetrating the free surface were measured, both in transient breaking waves and in 2- and 3-dimensional irregular seas, regular waves, and waves and uniform currents superposed. The performance of the entire experimental programme showed that extreme wave load intensities are associated with transient 2- or 3-dimensional breaking waves, of relatively short wave periods, and not with the highest waves in the simulated sea states. The total integrated in-line force and the total overturning moment caused by breaking waves exceeded the values measured in monochromatic regular waves by a factor of 3. Inception of wave breaking was caused by phase superposition, and occurred also for very low values of wave steepness s = 0.05.
40
Pan, Yun, Yong Zhou Cheng, Qing Feng Li e Wen Cheng Wang. "Experimental Study on Changes of Sloping Sandy Bed Profile under Breaking Waves". Applied Mechanics and Materials 212-213 (ottobre 2012): 163–68. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.163.
Testo completoAbstract (sommario):
The wave breaking forces can exacerbate sediment transport, and lead to erosion of the seabed, coastal deformation and destruction of coastal structures. The experiment is carried out in a wave flume with a 1:30 sloping sandy seabed. A wide range of measurements from the regular wave runs are reported, including time series of wave heights, changes of bed profile. The video records are analysed to measure the time development of the seabed form and the characteristics of the orbital motion of the sand in the wave breaking region. The location and wave height at wave breaking point is measured by experiment. Formation and evolution of sand ripple and sand bar are studied under the breaking waves. It is found that effect of bed surface on wave breaking zone is more significant than wave non-breaking.
41
Hieu, Phung Dang, e Phan Ngoc Vinh. "A numerical model for simulation of near-shore waves and wave induced currents using the depth-averaged non-hydrostatic shallow water equations with an improvement of wave energy dissipation". Tạp chí Khoa học và Công nghệ biển 20, n. 2 (22 maggio 2020): 155–72. http://dx.doi.org/10.15625/1859-3097/20/2/15087.
Testo completoAbstract (sommario):
This study proposes a numerical model based on the depth-integrated non-hydrostatic shallow water equations with an improvement of wave breaking dissipation. Firstly, studies of parameter sensitivity were carried out using the proposed numerical model for simulation of wave breaking to understand the effects of the parameters of the breaking model on wave height distribution. The simulated results of wave height near the breaking point were very sensitive to the time duration parameter of wave breaking. The best value of the onset breaking parameter is around 0.3 for the non-hydrostatic shallow water model in the simulation of wave breaking. The numerical results agreed well with the published experimental data, which confirmed the applicability of the present model to the simulation of waves in near-shore areas.
42
Pizzo, N. E., Luc Deike e W. Kendall Melville. "Current generation by deep-water breaking waves". Journal of Fluid Mechanics 803 (22 agosto 2016): 275–91. http://dx.doi.org/10.1017/jfm.2016.469.
Testo completoAbstract (sommario):
We examine the partitioning of the energy transferred to the water column by deep-water wave breaking; in this case between the turbulent and mean flow. It is found that more than 95 % of the energy lost by the wave field is dissipated in the first four wave periods after the breaking event. The remaining energy is in the coherent vortex generated by breaking. A scaling argument shows that the ratio between the energy in this breaking generated mean current and the total energy lost from the wave field to the water column due to breaking scales as $(hk)^{1/2}$, where $hk$ is the local slope at breaking. This model is examined using direct numerical simulations of breaking waves solving the full two-phase air–water Navier–Stokes equations, as well as the limited available laboratory data, and good agreement is found for strong breaking waves.
43
Delisi, Donald P., e Timothy J. Dunkerton. "Laboratory Observations of Gravity Wave, Critical Layer Flows Using Single and Double Wave Forcing". Applied Mechanics Reviews 47, n. 6S (1 giugno 1994): S113—S117. http://dx.doi.org/10.1115/1.3124384.
Testo completoAbstract (sommario):
Laboratory measurements of gravity wave, critical layer flows are presented. The measurements are obtained in a salt-stratified annular tank, with a vertical shear profile. Internal gravity waves are generated at the floor of the tank and propagate vertically upward into the fluid. At a depth where the phase speed of the wave equals the mean flow speed, defined as a critical level, the waves break down, under the right forcing conditions, generating small scale turbulence. Two cases are presented. In the first case, the wave forcing is a single, monochromatic wave. In this case, the early wave breaking is characterized as Kelvin-Helmholtz breaking at depths below the critical level. Later wave breaking is characterized by weak overturning in the upper part of the tank and regular, internal mixing regions in the lower part of the tank. In the second case, the wave forcing is two monochromatic waves, each propagating with a different phase speed. In this case, the early wave breaking is again Kelvin-Helmholtz in nature, but later wave breaking is characterized by sustained overturning in the upper part of the tank with internal mixing regions in the lower part of the tank. Mean velocity profiles are obtained both before and during the experiments.
44
Svendsen, I. A., e J. Veeramony. "Wave Breaking in Wave Groups". Journal of Waterway, Port, Coastal, and Ocean Engineering 127, n. 4 (agosto 2001): 200–212. http://dx.doi.org/10.1061/(asce)0733-950x(2001)127:4(200).
Testo completo
45
Chakrabarti, Subrata K. "Measurement and Analysis of Laboratory Generated Steep Waves". Journal of Offshore Mechanics and Arctic Engineering 125, n. 1 (1 febbraio 2003): 17–24. http://dx.doi.org/10.1115/1.1556403.
Testo completoAbstract (sommario):
In many offshore locations, storm generated steep waves are common and the survival of offshore structures in their presence is an important design condition. The design environment in depth-limited waters often includes waves of breaking and near-breaking conditions, in which currents may be present. Experiments were carried out in a wave tank with simulated steep waves with and without steady in-line current in which the wave profiles and the corresponding kinematics were simultaneously measured. The waves included both regular and random waves and often approached the breaking wave height for the water depth. These waves were analyzed by higher-order wave theory. In particular, the regular waves were simulated by the regular and irregular stream function theory. Especially steep wave profiles within the random waves were computed using the irregular stream function theory. The theory allows inclusion of steady current in its formulation for computation of wave kinematics. The correlation of the measured wave kinematics with the higher-order stream function wave theory showed that the wave theory could predict the kinematics of these steep waves (with and without the presence of current) well. However, in breaking waves, the vertical water particle velocity was not predicted well, especially near the trough. The effect of breaking and near-breaking steep waves on a fixed vertical caisson was also studied. The forces measured on the vertical caisson from the wave tank testing were analyzed to determine the effect of these waves and currents on the forces. It was found that the measured forces (and overturning moments) on the caisson model matched fairly well by the proper choice of force coefficients from the design guideline and the nonlinear stream function theory of appropriate order.
46
Babanin, A. V., T. Waseda, T. Kinoshita e A. Toffoli. "Wave Breaking in Directional Fields". Journal of Physical Oceanography 41, n. 1 (1 gennaio 2011): 145–56. http://dx.doi.org/10.1175/2010jpo4455.1.
Testo completoAbstract (sommario):
Abstract Wave breaking is observed in a laboratory experiment with waves of realistic average steepness and directional spread. It is shown that a modulational-instability mechanism is active in such circumstances and can lead to the breaking. Experiments were conducted in the directional wave tank of the University of Tokyo, and the mechanically generated wave fields consisted of a primary wave with sidebands in the frequency domain, with continuous directional distribution in the angular domain. Initial steepness of the primary wave and sidebands, as well as the width of directional distributions varied in a broad range to determine the combination of steepness/directional-spread properties that separates modulational-instability breaking from the linear-focusing breaking.
47
Manasseh, Richard, Alexander V. Babanin, Cameron Forbes, Kate Rickards, Irena Bobevski e Andrew Ooi. "Passive Acoustic Determination of Wave-Breaking Events and Their Severity across the Spectrum". Journal of Atmospheric and Oceanic Technology 23, n. 4 (1 aprile 2006): 599–618. http://dx.doi.org/10.1175/jtech1853.1.
Testo completoAbstract (sommario):
Abstract A passive acoustic method of detecting breaking waves of different scales has been developed. The method also showed promise for measuring breaking severity. Sounds were measured by a subsurface hydrophone in various wind and wave states. A video record of the surface was made simultaneously. Individual sound pulses corresponding to the many individual bubble formations during wave-breaking events typically last only a few tens of milliseconds. Each time a sound-level threshold was exceeded, the acoustic signal was captured over a brief window typical of a bubble formation pulse, registering one count. Each pulse was also analyzed to determine the likely bubble size generating the pulse. Using the time series of counts and visual observations of the video record, the sound-level threshold that detected bubble formations at a rate optimally discriminating between breaking and nonbreaking waves was determined by a classification-accuracy analysis. This diagnosis of breaking waves was found to be approximately 70%–75% accurate once the optimum threshold had been determined. The method was then used for detailed analysis of wave-breaking properties across the spectrum. When applied to real field data, a breaking probability distribution could be obtained. This is the rate of occurrence of wave-breaking events at different wave scales. With support from a separate, laboratory experiment, the estimated bubble size is argued to be dependent on the severity of wave breaking and thus to provide information on the energy loss due to the breaking at the measured spectral frequencies. A combination of the breaking probability distribution and the bubble size could lead to direct estimates of spectral distribution of wave dissipation.
48
Schultz, William W., Jin Huh e Owen M. Griffin. "Potential energy in steep and breaking waves". Journal of Fluid Mechanics 278 (10 novembre 1994): 201–28. http://dx.doi.org/10.1017/s0022112094003678.
Testo completoAbstract (sommario):
We find that the RMS wave height (square root of the potential energy) rather than peak-to-peak wave height is a better experimental and analytic criterion for determining when a regular, two-dimensional deep-water wave will break. A spectral algorithm for two-dimensional potential flow is developed and used to compare breaking onset criteria for energy input from (i) converging sidewalls, (ii) a submerged disturbance, and (iii) wave focusing. We also find that wave-breaking criteria (potential energy or the more classical peak-to-peak wave height) are a function of the rate of energy input. Large plunging waves occur when energy input rates are large. As energy input rates become smaller there is a smooth transition to smaller spilling waves. The various energy input methods show similar breaking trends in the limit as the energy input rate becomes small - waves break when the potential energy becomes approximately 52 % of the energy for the most energetic Stokes wave, with the formation of a singularity immediately before the crest. The effects of wave modulation and reflection are briefly discussed and shown not to affect the potential energy breaking criterion significantly. The experimental scatter of the RMS wave height is shown to be half that of wave steepness during incipient breaking in wave packets.
49
Saoxian, Shen, Zhang Yang e Andrew Cornett. "WAVE LOADS ASSESSMENT FOR SUBMERGED WATER INTAKE DESIGN". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 56. http://dx.doi.org/10.9753/icce.v36.structures.56.
Testo completoAbstract (sommario):
Estimating wave-induced forces on water intake is challenging, particularly for large size intake (up to 15m in its cap diameter) subject to breaking waves in shallow water. The relationships between wave properties and wave loads are not well understood, and no simple methods are available to predict hydrodynamic loads on submerged intakes, particularly under breaking waves. This paper attempts to provide a method of assessing wave forces on water intake pipe and velocity cap using the Froude-Krylov formula, based on physical modeling test results for submerged intake under breaking waves.
50
Kukulka, Tobias, e Tetsu Hara. "The Effect of Breaking Waves on a Coupled Model of Wind and Ocean Surface Waves. Part I: Mature Seas". Journal of Physical Oceanography 38, n. 10 (1 ottobre 2008): 2145–63. http://dx.doi.org/10.1175/2008jpo3961.1.
Testo completoAbstract (sommario):
Abstract This is the first of a two-part investigation of a coupled wind and wave model that includes the enhanced form drag of breaking waves. In Part I here the model is developed and applied to mature seas. Part II explores the solutions in a wide range of wind and wave conditions, including growing seas. Breaking and nonbreaking waves induce air-side fluxes of momentum and energy above the air–sea interface. By balancing air-side momentum and energy and by conserving wave energy, coupled nonlinear advance–delay differential equations are derived, which govern simultaneously the wave and wind field. The system of equations is closed by introducing a relation between the wave height spectrum and wave dissipation due to breaking. The wave dissipation is proportional to nonlinear wave interactions, if the wave curvature spectrum is below the “threshold saturation level.” Above this threshold the wave dissipation rapidly increases so that the wave height spectrum is limited. The coupled model is applied to mature wind-driven seas for which the wind forcing only occurs in the equilibrium range away from the spectral peak. Modeled wave height curvature spectra as functions of wavenumber k are consistent with observations and transition from k1/2 at low wavenumbers to k0 at high wavenumbers. Breaking waves affect only weakly the wave height spectrum. Furthermore, the wind input to waves is dominated by nonbreaking waves closer to the spectral peak. Shorter breaking waves, however, can support a significant fraction, which increases with wind speed, of the total air–sea momentum flux.