scholarly journals PHYSICAL REQUIREMENTS FOR A TAKEOFF IN SURFING

2017 ◽  
pp. 30
Author(s):  
Akihiko Kimura ◽  
Taro Kakinuma
Keyword(s):  
Wave Front ◽  
Time Variation ◽  
Wave Breaking ◽  
Horizontal Component ◽  
Breaking Point ◽  
Front Face ◽  
The Waves

The conditions required for a takeoff in surfing, are discussed, with the waves simulated numerically, considering two types of wave breaking, i.e., a plunging type, and a spilling type. First, a surfer is required to obtain a sufficient value for the horizontal component of paddling speed, not to be overtaken by a wave peak. Second, when the surfer stops paddling, he needs to be floating at a location where the force on him is downward, along the wave front face. On the basis of both conditions, the time variation of the required value for the horizontal component of paddling speed, is evaluated for both the plunging-type, and spilling-type, cases. When the paddling speed is sufficient, the surfable area is larger in the former case, than in the latter, on the offshore side of the wave-breaking point.

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.

scholarly journals Wave Breaking in Undular Bores with Shear Flows

Water Waves ◽  
2021 ◽  
Author(s):  
Maria Bjørnestad ◽  
Henrik Kalisch ◽  
Malek Abid ◽  
Christian Kharif ◽  
Mats Brun
Keyword(s):  
Turbulent Flows ◽  
Wave Breaking ◽  
Vries Equation ◽  
Kdv Equation ◽  
Flow Depth ◽  
Present Contribution ◽  
Undular Bore ◽  
Wave Flume ◽  
The Kdv Equation ◽  
The Waves

AbstractIt is well known that weak hydraulic jumps and bores develop a growing number of surface oscillations behind the bore front. Defining the bore strength as the ratio of the head of the undular bore to the undisturbed depth, it was found in the classic work of Favre (Ondes de Translation. Dunod, Paris, 1935) that the regime of laminar flow is demarcated from the regime of partially turbulent flows by a sharply defined value 0.281. This critical bore strength is characterized by the eventual breaking of the leading wave of the bore front. Compared to the flow depth in the wave flume, the waves developing behind the bore front are long and of small amplitude, and it can be shown that the situation can be described approximately using the well known Kortweg–de Vries equation. In the present contribution, it is shown that if a shear flow is incorporated into the KdV equation, and a kinematic breaking criterion is used to test whether the waves are spilling, then the critical bore strength can be found theoretically within an error of less than ten percent.

An experimental investigation of incipient spilling breakers

2009 ◽  
Vol 633 ◽  
pp. 271-283 ◽  
Author(s):  
J. D. DIORIO ◽  
X. LIU ◽  
J. H. DUNCAN
Keyword(s):  
Wave Breaking ◽  
High Speed ◽  
Phase Speed ◽  
Breaking Waves ◽  
Front Face ◽  
Geometrical Parameters ◽  
Instability Mechanism ◽  
Scaling Relationships ◽  
Self Similar ◽  
Spilling Breakers

In the present paper, the profiles of incipient spilling breaking waves with wavelengths ranging from 10 to 120cm were studied experimentally in clean water. Short-wavelength breakers were generated by wind, while longer-wavelength breakers were generated by a mechanical wavemaker, using either a dispersive focusing or a sideband instability mechanism. The crest profiles of these waves were measured with a high-speed cinematic laser-induced fluorescence technique. For all the wave conditions reported herein, wave breaking was initiated with a capillary-ripple pattern as described in Duncan et al. (J. Fluid Mech., vol. 379, 1999, pp. 191–222). In the present paper, it is shown that at incipient breaking the crest shape is self-similar with two geometrical parameters that depend only on the slope of a particular point on the front face of the gravity wave. The scaling relationships appear to be universal for the range of wavelengths studied herein and hold for waves generated by mechanical wavemakers and by wind. The slope measure is found to be dependent on the wave phase speed and the rate of growth of the crest height prior to incipient breaking.

Prediction of Water Wave Breaking Height and Depth Using ANFIS

2011 ◽  
Author(s):  
Ehsan Delavari ◽  
Ahmad Reza Mostafa Gharabaghi ◽  
Mohammad Reza Chenaghlou
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Fuzzy Inference System ◽  
Wave Breaking ◽  
Fuzzy Inference ◽  
Breaking Point ◽  
Empirical Equations ◽  
Anfis Model ◽  
Inference System ◽  
Semi Empirical

Wave height as well as water depth at the breaking point are two basic parameters which are necessary for studying coastal processes. In this paper, the application of Fuzzy Inference System (FIS) and Adaptive Neuro-Fuzzy Inference System (ANFIS) and semi-empirical models are investigated. The data sets used in this study are published laboratory data obtained from regular wave breaking on plane, impermeable slopes collected from 22 sources. Results indicate that the developed ANFIS model provides more accurate and reliable estimation of breaking wave height, compared to semi-empirical equations. However, some of semi-empirical equations provide better predictions of water depth at the breaking point compared to the ANFIS model.

Wave-Follower Field Measurements of the Wind-Input Spectral Function. Part III: Parameterization of the Wind-Input Enhancement due to Wave Breaking

2007 ◽  
Vol 37 (11) ◽  
pp. 2764-2775 ◽  
Author(s):  
Alexander V. Babanin ◽  
Michael L. Banner ◽  
Ian R. Young ◽  
Mark A. Donelan
Keyword(s):  
Energy Flux ◽  
Water Waves ◽  
Wave Breaking ◽  
Field Measurements ◽  
Mean Value ◽  
Breaking Wave ◽  
Strong Wind ◽  
Local Wave ◽  
Wind Input ◽  
The Waves

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.

scholarly journals Wave Breaking in Dense Plumes

2014 ◽  
Vol 44 (2) ◽  
pp. 790-800 ◽  
Author(s):  
Paul R. Holland ◽  
Richard E. Hewitt ◽  
Matthew M. Scase
Keyword(s):  
Wave Breaking ◽  
Deep Ocean ◽  
The Novel ◽  
Conservation Equations ◽  
Hyperbolic Conservation ◽  
Dense Fluid ◽  
Bottom Waters ◽  
Novel Concept ◽  
Short Time ◽  
The Waves

Abstract Sinking dense plumes are important in many oceanographic settings, notably the polar formation of deep and bottom waters. The dense water sources feeding such plumes are commonly affected by tidal modulation, leading to plume variability on short time scales. In a simple unsteady theory of one-dimensional plumes (based on conservation equations for volume, momentum, and buoyancy), this plume variability is manifested as waves that travel down the resulting current. Using numerical techniques applied to the hyperbolic conservation equations, this study investigates the novel concept that these waves may break as they travel down the plumes, triggering intense local mixing between the dense fluid and surrounding ocean. The results demonstrate that the waves break at geophysically relevant distances from the plume source. The location of wave breaking is very sensitive to plume drag from the seabed, the properties of the dense source, and the amplitude and period of the source modulation. To the extent that the simple model represents the real world, these results suggest that wave breaking originating from the tidal modulation of dense plumes could lead to a strong and previously unexplored source of local deep-ocean mixing.

scholarly journals Internal wave breaking and the fate of planets around solar-type stars

2010 ◽  
Vol 6 (S271) ◽  
pp. 363-364
Author(s):  
Adrian J. Barker ◽  
Gordon I. Ogilvie
Keyword(s):  
Gravity Waves ◽  
Wave Breaking ◽  
Internal Gravity Waves ◽  
Amplitude Dependence ◽  
Tidal Dissipation ◽  
Short Period ◽  
Central Regions ◽  
Solar Type ◽  
The Waves ◽  
Solar Type Star

AbstractInternal gravity waves are excited at the interface of convection and radiation zones of a solar-type star, by the tidal forcing of a short-period planet. The fate of these waves as they approach the centre of the star depends on their amplitude. We discuss the results of numerical simulations of these waves approaching the centre of a star, and the resulting evolution of the spin of the central regions of the star and the orbit of the planet. If the waves break, we find efficient tidal dissipation, which is not present if the waves perfectly reflect from the centre. This highlights an important amplitude dependence of the (stellar) tidal quality factor Q′, which has implications for the survival of planets on short-period orbits around solar-type stars, with radiative cores.

scholarly journals Solitary Wave Formation from a Generalized Rosenau Equation

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
J. I. Ramos ◽  
C. M. García-López
Keyword(s):  
Wave Front ◽  
Fourth Order ◽  
Accurate Method ◽  
Amplitude Curve ◽  
Convective Term ◽  
Compact Finite Differences ◽  
Rosenau Equation ◽  
Spatial Derivatives ◽  
Fifth Order ◽  
The Waves

A generalized viscous Rosenau equation containing linear and nonlinear advective terms and mixed third- and fifth-order derivatives is studied numerically by means of an implicit second-order accurate method in time that treats the first-, second-, and fourth-order spatial derivatives as unknown and discretizes them by means of three-point, fourth-order accurate, compact finite differences. It is shown that the effect of the viscosity is to decrease the amplitude, curve the wave trajectory, and increase the number and width of the waves that emerge from an initial Gaussian condition, whereas the linear convective term pushes the wave front towards the downstream boundary. It is also shown that the effect of the nonlinear convective term is to increase the steepness of the leading wave front and the number of sawtooth waves that are generated behind it, while that of the first dispersive term is to increase the number of waves that break up from the initial condition as the coefficient that characterizes this term is decreased. It is also shown that, for reasons of stability, the second dispersion coefficient must be much smaller than the first one and its effects on wave propagation are relatively small.

scholarly journals THEORETICAL FORMS OF SHORELINES

1964 ◽  
Vol 1 (9) ◽  
pp. 14 ◽  
Author(s):  
W. Grijm
Keyword(s):  
Wave Front ◽  
Laboratory Tests ◽  
Coastal Engineering ◽  
Mathematical Treatment ◽  
Maximum Value ◽  
The Waves

Laboratory tests say that the littoral transport by waves reaches a maximum value when the waves approach the shore obliquely. In some way this must lead to peculiarities in the forms of shorelines. Therefore we put the question what types of shorelines can mathematically exist assuming the littoral transport is ruled by the function sin 2oC where c< is the angle between the wave front and the shoreline. This yields some basic types of shorelines. After a brief description of the mathematical treatment these results will be discussed. This paper is a continuation of the paper presented on the same subject at the 7 conference on coastal engineering.

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