scholarly journals Nonlinear Wave Transformation in Coastal Zone: Free and Bound Waves

Fluids ◽  
2021 ◽  
Vol 6 (10) ◽  
pp. 347
Author(s):  
Sergey Kuznetsov ◽  
Yana Saprykina
Keyword(s):  
Coastal Zone ◽  
Energy Exchange ◽  
Second Harmonic ◽  
Wave Transformation ◽  
Spatial Evolution ◽  
Wave Shape ◽  
Spatial Fluctuations ◽  
Second Wave ◽  
Wavelet Analyses ◽  
Sloping Bottom

The nonlinear transformation of waves in the coastal zone over the sloping bottom is considered on the base of field, laboratory, and numerical experiments by methods of spectral and wavelet analyses. The nonlinearity leads to substantial changes of wave shape during its propagation to the shore. Since these changes occur rapidly, the wave movement is non-periodical in space, and the application of linear theory concepts of wavenumber or wavelength results in some paradoxical phenomena. When analyzing the spatial evolution of waves in the frequency domain, the effect of periodic energy exchange and changes in the phase shift between the first and second wave harmonics are observed. When considering the wavenumber domain, the free and bound waves of both the first and second harmonics with constant in space amplitudes appear, and all spatial fluctuations of the wave parameters are caused by interference of these four harmonics. Practically important consequences such as the wave energy spatial fluctuations and of anomalous dispersion of the second harmonic are shown and discussed.

scholarly journals PARAMETERIZATION OF EVOLUTION OF BIPHASE DURING NONLINEAR TRANSFORMATION OF WAVES IN COASTAL ZONE

2017 ◽  
pp. 3
Author(s):  
Yana Saprykina ◽  
Sergey Kuznetsov ◽  
Margarita Shtremel
Keyword(s):  
Experimental Data ◽  
Phase Shift ◽  
Coastal Zone ◽  
Energy Exchange ◽  
Wave Motion ◽  
Empirical Relation ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Nonlinear Harmonics ◽  
Sloping Bottom

Based on experimental data, the problem of parametrization of spatial variation of the phase shift (biphase) between the first and second nonlinear harmonics of wave motion during wave transformation over sloping bottom in the coastal zone is discussed. It is revealed that the biphase values vary in the range [–π/2, π/2]. Biphase variations rigorously follow fluctuations in amplitudes of the first and second harmonics and the periodicity of energy exchange between them. The empirical relation applied in modern practice to calculate the biphase, which depends on the Ursell number, is incorrect for calculating the biphase for wave evolution in the coastal zone, because it does not take into account periodic energy exchange between the nonlinear harmonics. The new approximations of the biphase values for typical scenarios of wave transformations are suggested. It was demonstrated that the biphase of breaking waves defines breaking index and breaking type.

PHYSICAL INTERPRETATION OF WAVE BREAKING CRITERIA

2017 ◽  
Author(s):  
Sergey Kuznetsov ◽  
Sergey Kuznetsov ◽  
Yana Saprykina ◽  
Yana Saprykina ◽  
Boris Divinskiy ◽  
...  
Keyword(s):  
Nonlinear Wave ◽  
Wave Breaking ◽  
Second Harmonic ◽  
Vertical Axis ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Spectral Structure ◽  
Similarity Parameter ◽  
Nonlinear Harmonics ◽  
The Waves

On the base of experimental data it was revealed that type of wave breaking depends on wave asymmetry against the vertical axis at wave breaking point. The asymmetry of waves is defined by spectral structure of waves: by the ratio between amplitudes of first and second nonlinear harmonics and by phase shift between them. The relative position of nonlinear harmonics is defined by a stage of nonlinear wave transformation and the direction of energy transfer between the first and second harmonics. The value of amplitude of the second nonlinear harmonic in comparing with first harmonic is significantly more in waves, breaking by spilling type, than in waves breaking by plunging type. The waves, breaking by plunging type, have the crest of second harmonic shifted forward to one of the first harmonic, so the waves have "saw-tooth" shape asymmetrical to vertical axis. In the waves, breaking by spilling type, the crests of harmonic coincides and these waves are symmetric against the vertical axis. It was found that limit height of breaking waves in empirical criteria depends on type of wave breaking, spectral peak period and a relation between wave energy of main and second nonlinear wave harmonics. It also depends on surf similarity parameter defining conditions of nonlinear wave transformations above inclined bottom.

Characteristics of Transforming Waves Breaking Over a Fringing Reef

2019 ◽  
Author(s):  
Fuxian Gong ◽  
Manhar R. Dhanak
Keyword(s):  
Energy Flux ◽  
Wave Breaking ◽  
Reef Flat ◽  
Stokes Equations ◽  
Second Harmonic ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Fundamental Wave ◽  
Fringing Reef ◽  
Wave Shoaling

Abstract Direct numerical simulation (DNS), based on solution of the Navier Stokes equations, is used to study the characteristics of the transformation of monochromatic waves over a simplified fringing reef, including wave shoaling, and wave breaking that occurs under certain circumstances. The reef geometry involves a sloped plane beach extended with a simple submerged horizontal reef flat. The characteristics are studied for several case studies involving a selection of submergence depths on the reef flat and for a range of incident wave conditions, corresponding to nonbreaking, a spilling breaker and a plunging breaker, are considered. The results are compared with those of laboratory experiments (Kouvaras and Dhanak, 2018). Consistent with other studies, generation of harmonics of the fundamental wave frequency is found to accompany the wave transformation over the reef and the process of transfer of energy through wave breaking. The energy flux decreases dramatically in the onshore direction when the waves break. The more severe the wave breaking process, the greater the decrease in energy flux, particularly in the wave shoaling process. Most of the wave energy is carried by the first harmonic throughout its passage over the fringing reef. In nonbreaking waves, the energy gradually transfers from the first harmonic to the second harmonic due to bottom effects in terms of flat wave troughs and secondary waves. The further the distance away from the fore edge of the reef, the larger the percentage of the transmission, resulting in a single dominant harmonic frequency at the end of the wave surfing zone. For breaking waves, the energy carried by the first harmonic gradually decreases in the onshore direction. Energy transmission between harmonics is not as efficient as nonbreaking waves, while wave dissipation is significant in the wave breaking process.

scholarly journals Wave Characteristics in Breaststroke Technique with and Without Snorkel Use

2013 ◽  
Vol 39 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Ana Conceição ◽  
António J. Silva ◽  
José Boaventura ◽  
Daniel A. Marinho ◽  
Hugo Louro
Keyword(s):  
Normal Condition ◽  
Mass Velocity ◽  
Second Harmonic ◽  
Harmonic Wave ◽  
The Body ◽  
Swimming Velocity ◽  
Stroke Index ◽  
Stroke Length ◽  
Wave Characteristics ◽  
Second Wave

Abstract The purpose of this paper was to examine the characteristics of waves generated when swimming with and without the use of Aquatrainer® snorkels. Eight male swimmers performed two maximal bouts of 25 m breaststroke, first without the use of a snorkel (normal condition) and then using a snorkel (snorkel condition). The body landmarks, centre of the mass velocity, stroke rate, stroke length, stroke index, and Strouhal number (St) were quantified. Fourier analysis was conducted to determine the frequency, amplitude, and phase characteristics of the vertical undulations. We also determined the undulation period, the first and second harmonic wave percentage, and the contribution of these components to the power of each of the wave signals. The first wave harmonics had a frequency of 0.76 Hz (normal condition) and 0.78 Hz (snorkel condition), and the second wave harmonics had a frequency of 1.52 Hz (normal condition) and 1.56 Hz (snorkel condition). Under the normal conditions, the wave amplitude was higher on the vertex (0.72 m) and cervical (0.32 m) than that produced under snorkel conditions (0.71 m and 0.28 m, respectively). The lowest values were found in the hip (0.03 m in normal conditions, and 0.02 m in snorkel conditions) and in the trunk (0.06 m in normal conditions, and 0.04 m in snorkel conditions). It can be concluded that snorkel use seems to lead to slight changes in the biomechanical pattern in swimming velocity, as well as several stroke mechanical variables.

scholarly journals Efficient Generation of Coherent Stokes Field in Hydrogen Gas-Filled Hollow Core Photonic Crystal Fibres

2020 ◽  
Vol 30 (2) ◽  
pp. 143
Author(s):  
Thanh Doan Thai ◽  
Quy Quang Ho ◽  
Thang Manh Nguyen
Keyword(s):  
Photonic Crystal ◽  
Pulse Width ◽  
Energy Exchange ◽  
Hydrogen Gas ◽  
Spatial Evolution ◽  
Hollow Core ◽  
Generation Efficiency ◽  
Photonic Crystal Fibres ◽  
Temporal And Spatial ◽  
Stokes Generation

In this paper, we study of the coherent Stokes generation in a transient Raman regime by Hydrogen gas-filled hollow-core photonic crystal fibres (HC-PCFs) configuration. The temporal and spatial evolution of the pump and Stokes field envelopes as well as the coherence and population inversion is numerically observed. The influence of the pump pulse width and gas pressure on the energy exchange along fiber and Stokes generation efficiency is investigated.

scholarly journals SECONDARY WAVES IN COASTAL ZONE: PHYSICAL MECHANISMS OF FORMATION AND POSSIBLE APPLICATION FOR COASTAL PROTECTION

2012 ◽  
Vol 1 (33) ◽  
pp. 12 ◽  
Author(s):  
Sergey Kuznetsov ◽  
Yana Saprykina
Keyword(s):  
Coastal Zone ◽  
Wave Transformation ◽  
Secondary Wave ◽  
Coastal Protection ◽  
Weakly Nonlinear ◽  
Physical Mechanisms ◽  
Advantages And Disadvantages ◽  
Floating Breakwater ◽  
Mechanisms Of Formation ◽  
Underwater Structures

The formation of secondary wave in a coastal zone was investigated on the base of field, laboratory and numerical experiments. It was found that formation of secondary waves is essentially part of weakly nonlinear-dispersive wave transformation and determined by a periodic exchange of energy between the first and second harmonics. The formation of secondary waves depends on a stage of wave transformation and defined by amplitude of secondary harmonic and by phase shift between first and second harmonics. On the base of numerical modeling and laboratory experiments an idea of combination of underwater structures with floating breakwater is investigated. Waves propagating above submerged bar generate secondary waves that decrease the mean period of waves. Each additional bar reinforces and stabilizes this effect. Behind the bars the floating breakwater can be applied, because it suppresses successfully only short waves. Advantages and disadvantages of this idea are discussed.

scholarly journals The Method for Evaluating Cross-Shore Migration of Sand Bar under the Influence of Nonlinear Waves Transformation

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 214
Author(s):  
Margarita Shtremel ◽  
Yana Saprykina ◽  
Berna Ayat
Keyword(s):  
Sediment Transport ◽  
Nonlinear Wave ◽  
Maximum Amplitude ◽  
Field Measurements ◽  
Wave Transformation ◽  
Sandy Bottom ◽  
Divergence Point ◽  
Sand Bar ◽  
Wave Induced ◽  
Second Wave

Sand bar migration on the gently sloping sandy bottom in the coastal zone as a result of nonlinear wave transformation and corresponding sediment transport is discussed. Wave transformation on the intermediate depth causes periodic exchange of energy in space between the first and the second wave harmonics, accompanied by changes in the wave profile asymmetry. This leads to the occurrence of periodical fluctuations in the wave-induced sediment transport. It is shown that the position of the second nonlinear wave harmonic maximum determines location of the divergence point of sediment transport on the inclined bottom profile, where it changes direction from the onshore to the offshore. Such sediment transport pattern leads to formation of an underwater sand bar. A method is proposed to predict the position of the bar on an underwater slope after a storm based on calculation of the position of the maximum amplitude of the second nonlinear harmonic. The method is validated on the base of field measurements and ERA 5 reanalysis wave data.

A Physical Model of Wind Waves in the Coastal Zone

2008 ◽  
Author(s):  
Yana Saprykina ◽  
Natalia Andreeva ◽  
Sergey Kuznetsov ◽  
Zhivelina Cherneva ◽  
C. Guedes Soares
Keyword(s):  
Time Series ◽  
Coastal Zone ◽  
Wind Waves ◽  
Irregular Waves ◽  
Wave Transformation ◽  
Free Surface Elevation ◽  
Space And Time ◽  
Initial Stage ◽  
Instantaneous Values ◽  
The Waves

The variability of the amplitude-frequency structure of wind waves in space and time during their transformation in the coastal zone are considered. Wave time series, measured synchronously in 15 points along the wave propagation, obtained at field and laboratory experiments, were used for the analysis. Free surface elevation time series were represented as a sum of first and second harmonics with amplitudes slowly varying in time (or envelopes of the waves of corresponding frequency bands). Relative changes of these amplitudes in space and time were studied also. It was revealed, that at the initial stage of the wave transformation, the changes of amplitudes of the first and the second harmonics are similar and amplitudes of the second harmonics are proportional to the squared amplitudes of the first harmonics. At this stage the variability of parameters of individual irregular waves can be explained by Stokes theory. Nearer to the coast the instantaneous values of the amplitudes of the first and the second harmonics varies in time chaotically and is not possible to construct a simple model of the variability of the parameters of individual irregular waves. The main reason for this effect is the backward energy transfer from the second to the first harmonics of the waves during nearly resonant non-linear triad interactions.

Wave Breaking Type as a Typical Sign of Nonlinear Wave Transformation Stage in Coastal Zone

2020 ◽  
Vol 28 (1) ◽  
pp. 75-82
Author(s):  
Ya. V. Saprykina ◽  
S. Yu. Kuznetsov ◽  
O. A. Kuznetsova ◽  
I. V. Shugan ◽  
Yang-Yih Chen
Keyword(s):  
Nonlinear Wave ◽  
Coastal Zone ◽  
Wave Breaking ◽  
Wave Transformation ◽  
Typical Sign ◽  
Transformation Stage
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