Deep-water Waves Research Articles

Sediment textural characteristics and spatial variability of embayed sandy beaches in the west Guangdong

The grain size analysis has been widely used to characterize or distinguish sedimentary environments, identify transport patterns and infer sediment transport directions. However, what valuable information can sediment grain size analysis provide within the modern morphodynamic framework? This paper studied the structural characteristics and spatial variability of intertidal sediments for twelve embayed sandy beaches in the west Guangdong and attempted to answer this question. The results indicated that these beaches were mainly composed of fine- or medium-grained, moderately-well sorted, nearly symmetrical and mesokurtic intertidal sediments. It was found that the cumulative probability curve was not necessarily an effective method to distinguish longshore dynamic environments, and the bivariate scatter plots between grain size parameters cannot differentiate between the upper and lower intertidal sedimentary environments. The mean sizes of the intertidal sediments were significantly correlated with the intertidal gradients, but not significantly correlated with the deep-water wave heights. The mean sizes from the upper intertidal sediments were found to be an important indicator for most of the embayed sandy beaches, reflecting the longshore variation of modern hydrodynamics. In addition, it was highlighted for the role of sediment source and various past processes, which largely determined the basic characteristics of the studied beach sediments.

Coupling between resonant sloshing and lateral motions of a two-dimensional rectangular tank

Abstract

Note on estimating bed shear stress caused by breaking random waves

This note presents a method of how the bed shear stress caused by breaking random waves on slopes can be estimated. This is obtained by adopting the Sumer et al. (2013) bed shear stress formula due to spilling and plunging breaking waves on hydraulically smooth slopes combined with the Myrhaug and Fouques (2012) joint distribution of surf similarity parameter and wave height for individual random waves in deep water. The conditional mean value of the maxima of mean bed shear stress during wave runup given wave height in deep water is provided including an example for spilling and plunging breaking random waves corresponding to typical field conditions. Another example compares the present results with one case from Thornton and Guza (1983) estimating the wave energy dissipation caused by bed shear stress beneath breaking random waves.

Study of groin structures effectiveness for against abrasion in Padang Beach

This study was conducted to evaluating the performance of existing coastal protection structure to restrain the rate of erosion as a result of the influence of hydrodynamics process. Condition that reviewed was in form of distance shoreline as simulation results to initial reference line before. STWAVE module used to determine wave height at near shore as transformation of deep water wave height that determined before from SMB method. One Line Model was conducted to get shoreline change in each time step calculation. Model consists of two conditions, with the absence of coastal structures and with structure respectively. The simulation result show that potential erosion occurs at Batang Arau river mouth with no protection structure. Large erosion predicted around 59.04 meters from the shoreline position early. With coastal protection, model result obtained sedimentation of 7.33 meters coastline from its initial position. This occurs at a distance of 475 meters from the boundary domain. Modeling results also showed erosion is 18.39 meters at a distance of 250 m from the boundary domain. This is likely due to the limited modelling conditions that without reviewing of littoral transport direction that occurred in perpendicular to the coast. Result study show that the presence of a groins in Padang coasts looks already quite effective to maintain the shoreline of the littoral transport direction, however the installation of groins seemingly did not give significant meaning in the addition of the coastline.

A mechanism for the increased wave-induced drift of floating marine litter

Abstract

Bound Coherent Structures Propagating on the Free Surface of Deep Water

This article presents a study of bound periodically oscillating coherent structures arising on the free surface of deep water. Such structures resemble the well known bi-soliton solution of the nonlinear Schrödinger equation. The research was carried out in the super-compact Dyachenko-Zakharov equation model for unidirectional deep water waves and the full system of nonlinear equations for potential flows of an ideal incompressible fluid written in conformal variables. The special numerical algorithm that includes a damping procedure of radiation and velocity adjusting was used for obtaining such bound structures. The results showed that in both nonlinear models for deep water waves after the damping is turned off, a periodically oscillating bound structure remains on the fluid surface and propagates stably over hundreds of thousands of characteristic wave periods without losing energy.

On the breaking inception of unsteady water wave packets evolving in the presence of constant vorticity

Abstract

Vertical handover in heterogeneous networks using WDWWO algorithm with NN

ABSTRACT In heterogeneous networks, Vertical Handover (VH) plays a vital consequence of customer mobility as they have a high impact on networking performance like delay, throughput and call block probability. Even in the presence of various existing works, VH management exhibit certain drawbacks like method complexity, difficult network modelling and inaccurate handover. Thus, a hybrid methodology is proposed in this work which can provide accurate VH and considerable reduction in working complexity. Here, a combination of Deep Residual Neural (DRN) and Wind-Driven Water Wave Optimisation (WDWWO) is introduced to perform VH. Accurate prediction of Received Signal Strength (RSS) is a difficult task for mobile users while moving from one network to another. In order to tackle this situation, DRN is used with WDWWO based weight optimisation, hence the name Optimised DRN (ODRN). Almost every networking parameters like bandwidth, delay, throughput, velocity, BER, SNR, energy consumption, monetary cost and data traffic are included in ODRN modelling. The proposed work is implemented in NS2 platform and resultant performances like energy consumption, RSS, throughput, packet delivery ratio, packet loss, handover failure rate, algorithm convergence and latency are compared with conventional methods of D-TOPSIS, FIS-ENN and F-AHP.

FRACTAL LAKSHMANAN–PORSEZIAN–DANIEL MODEL WITH DIFFERENT FORMS OF NONLINEARITY AND ITS NOVEL SOLITON SOLUTIONS

The nonlinear Schrödinger equation (NLSE) can well identify the development of waves in deep water and optical fibers towards the least-order approximation. This study addresses the Lakshmanan–Porsezian–Daniel (LPD) fractal model which emerges from the application of the Heisenberg spin chain and fiber optics. This paper analyzes three types of nonlinear rules, namely Kerr law, quadratic law, and parabolic law. The variational approach to the combination of the Ritz idea is used to discover the new optical soliton solutions for the LPD-equation. It poses the requisite novel conditions for ensuring the existence of valid solitons. Three- and two-dimensional configurations are demonstrated by choosing the correct values for the parameters. This study focused on the pioneering research boundaries of the LPD-equation and other associated nonlinear evolution models in the field of communications network technology and optical fiber.

Persistence of hydrodynamic envelope solitons: Detection and rogue wave occurrence

The observation of a wave group persisting for more than 200 periods in the direct numerical simulation of nonlinear unidirectional irregular water waves in deep water is discussed. The simulation conditions are characterized by parameters realistic for broad-banded waves in the sea. Through solution of the associated scattering problem for the nonlinear Schrödinger equation, the group is identified as the intense envelope soliton with remarkably stable parameters. Most of the extreme waves occur on top of this group, resulting in higher and longer rogue wave events.

Perturbatively conserved higher nonlocal integral invariants of free-surface deep-water gravity waves

We exhibit a set of six explicit higher nonlocal integral invariants of free-surface deep-water gravity waves conserved in lowest nontrivial orders of perturbation in the amplitude of the surface displacement.

Wind-wave hindcast using modified ECMWF ERA-Interim wind field in the Mediterranean Sea

This study evaluates the usage of the SWAN model forced with modified wind field along the Mediterranean Sea. ECMWF ERA-Interim wind field was used to force the model. Third-generation SWAN model was applied in non-stationary mode with linear and exponential growth from wind including both deep and shallow water wave dissipation processes. Four locations have been considered to calibrate and validate the model on spatial and temporal scales, two wave buoys at Alghero and Mazara, Italy in the western Mediterranean during years 1990 and 1998; and two S4DW devices along the Egyptian Mediterranean Coast in the eastern Mediterranean during the years 2004 and 2010. ECMWF wind field and its influence on the different wave parameters were assessed. Model calibration results revealed that enhancing the ECMWF ERA-Interim wind field by 20%–25% gives good matching results in hindcasting significant wave height with better estimates of extreme events using a 25% enhancement factor. However, no considerable improvements were observed in simulating the wave period that is underestimated by the SWAN model. The validation results showed the high performance of the calibrated SWAN model with the modified wind field with an average RMSE and scatter index of about 0.29 m and 31% respectively. Increasing the wind field higher than 25% gives comparable results but with significant overestimation of the storm conditions. Considerable underestimations were detected for significant wave height below 1 m even with using Wind Enhancement Factor (WEF). These results were also validated by comparison with previous studies. A 31-years (1988–2018) wave atlas was obtained from which the general description of wave climate along the Mediterranean Sea was explained. The high-resolution SWAN model allows us to study the wave climate and extreme wave conditions along the southeastern Mediterranean basin providing necessary information for the development of this coastal zone.

Validation Experiment of a Single-View Image-Sequence Algorithm to Identify Scale and Sea-State Characteristics

In applied science and engineering contexts, ocean free-surface wave-field characterization is an ongoing research area relevant to many diverse applications. The use of optical means for this characterization, in particular, is an appealing solution due to the promise of relatively high spatial resolution and modest cost (i.e., applying off-the-shelf still cameras or video cameras). This work investigates the validity of a previously published algorithm related to visible-wavelength ocean free-surface wave-field videos. The first part of the algorithm uses the video content to determine scale from a single-perspective, uncalibrated video. The second part of the algorithm applies the video content to determine sea-state characteristics, such as dominant wave period and wavelength. Due to the complications of obtaining well-characterized real-world data sets, algorithms proposed within the literature are not always validated experimentally, but the scientific community relies on the process of verification and validation to build confidence in emerging scientific contributions. This work addresses the need to assess the performance of the existing algorithm through validation experiments. Video recordings of approximate deep-water waves are collected in a controlled indoor environment to experimentally validate the algorithm, and a suite of postprocessing parameters is explored to identify the algorithm's sensitivities for a chosen unit problem. Recommendations for the algorithm parameter selection and an assessment of the algorithm efficacy are offered for researchers interested in the implementation of this algorithm.

Accelerated reproduction of 2-D periodic waves

AbstractThe paper describes the attempt to develop the accelerated method of simulation of 2-D surface waves with a use of 2-D model derived by simplifications of 3-D equations for potential periodic deep-water waves. The derivation is based on separation of velocity potential in surface-fitted coordinates into linear and non-linear components and analysis of exact Poisson equation for non-linear component of potential on a free surface. This equation contains both the first and second derivatives of velocity potential. The analysis of very accurate multiple solutions for velocity potential obtained with 3-D model shows that these variables are linearly connected to each other, what allows to obtain the 2-D equation for first derivative of potential (i.e., the vertical velocity on a surface), what gives the closed 2-D formulation for 3-D problem of 2-D waves. The connection between first and second variables is not precise; hence, the method as a whole cannot be exact. However, the 2-D model derived is able to reproduce different statistical characteristics of 2-D wave field with good accuracy. The most evident advantage of new model consists of absence of calculation of 3-D structure of velocity potential what increases a speed of calculations by about two orders.

Nonlinear wave generation using a heaving wedge

This paper investigates the optimization of second-order control signals required to produce stable non-linear, deep-water waves using a wedge-shaped, plunger-type wave generator. Both numerical and experimental methods are utilized. A fully non-linear and dispersive potential flow (FNPF) solver developed at DTU is used for the numerical work, following improvements that reduce reflection to 1%. The numerical solver is validated against theoretical and experimental data. A defect correction optimization scheme is employed, resulting in optimized control signals for non-dimensional wave numbers of 2.04-8.17 and steepness of 3-7%. These control signals produce waves that are within 2% of stream function theory solutions for the fundamental harmonic component, and within 10% for the second-order harmonic component. The results demonstrate both the applicability of this optimization procedure and the suitability of a heaving wedge for generating stable non-linear deep-water waves.

Numerical investigation of third-order resonant interactions between two gravity wave trains in deep water

Intense resonant interactions between two deep-water gravity waves can lead to the bending and then splitting of crests and troughs. The curvatures of the crests and troughs increase with an increase of the primary wave's steepness and the resonant wave's propagation distance. For primary waves with small steepness, the crest and trough lines will eventually split, as long as the propagation distance is sufficiently large. The crest line is split into a longer segment with a larger wave crest and a shorter one with a smaller wave crest.

An analytical and numerical study of a vertically discretized multi-paddle wavemaker for generating free surface and internal waves

A vertically discretized multi-paddle wavemaker is proposed that generates various wave types without the depth-invariant flow condition limitation associated with conventional piston type wavemakers. A first-order mathematical formulation for the paddle stroke is derived and used to selectively generate free surface waves similar to either piston type or flap type wavemakers, depending on the number of utilized paddles. The mathematical formulation is further extended to a multi-phase internal wave case. Paddle discretization performance is evaluated using OpenFOAM, a numerical model that solves the Navier-Stokes equations for two (or more) immiscible and incompressible fluids. Dynamic meshing capability is incorporated in the model. Model results show multiple discrete paddles efficiently generate deep water waves under laminar flow conditions. In intermediate wave conditions, the multi-paddle discretization is less advantageous. Internal waves and resulting free surface waves among air, oil, and water phases are simulated using only two paddles and imposing a fast mode. Model results agree with flow characteristics for both internal and locked free surface waves.

On the statistical properties of surface elevation, velocities and accelerations in multi-directional irregular water waves

Abstract

Time-frequency energy analysis of deepwater explosion shock wave signals based on HHT

In order to study the time-frequency characteristics of shock wave signals under deep water explosion conditions, experiments are performed using water medium explosion containers to simulate different water depth conditions, and signal analysis is performed on the shock wave data obtained in the experiments. Traditional time-frequency analysis methods such as Fourier transform and wavelet transform have many limitations on deep-water explosion shock wave signal analysis, the HHT method is used to analyse the experimental data from the three-dimensional Hilbert spectrum, marginal spectrum and instantaneous energy spectrum. The results show that the time-frequency method can effectively extract the frequency components of the deep-water explosion load signal in different periods. It provides a reference for people to understand the time frequency characteristics of shock wave signals in deep water.

Nonlinear Spectral Synthesis of Soliton Gas in Deep-Water Surface Gravity Waves.

Soliton gases represent large random soliton ensembles in physical systems that exhibit integrable dynamics at the leading order. Despite significant theoretical developments and observational evidence of ubiquity of soliton gases in fluids and optical media, their controlled experimental realization has been missing. We report a controlled synthesis of a dense soliton gas in deep-water surface gravity waves using the tools of nonlinear spectral theory [inverse scattering transform (IST)] for the one-dimensional focusing nonlinear Schrödinger equation. The soliton gas is experimentally generated in a one-dimensional water tank where we demonstrate that we can control and measure the density of states, i.e., the probability density function parametrizing the soliton gas in the IST spectral phase space. Nonlinear spectral analysis of the generated hydrodynamic soliton gas reveals that the density of states slowly changes under the influence of perturbative higher-order effects that break the integrability of the wave dynamics.