Wave Obliquity Research Articles

Role of tidal range and coastline morphology on the evolution of two macrotidal sand spits

AbstractThe present study examines the stratigraphy of two sandspits that both appeared and developed since the middle of the 17th century during the Little Ice Age. The Arçay spit is located along the macrotidal Atlantic coast in South‐West France with a maximum tidal range of 6.5 m. The Pointe du Banc in the English Channel, North‐West France, is located in a hypertidal coastal setting with a tidal range of up to 14 m. The evolution of the two spit systems has been compared using historical maps, ground penetrating radar data and facies analysis and geochronological data from sediment cores. The Pointe du Banc spit developed between 1650 and 1750 CE, in a dominant seaward direction while the main mode of construction of the Arçay spit was in a longshore direction. It is proposed that this difference relates to sediment supply and coastline morphology. At the Pointe du Banc spit, the large tidal range causes a long wind fetch and sustained aeolian sediment supply. Moreover, the spit is located at the apex of a large‐scale embayment where sediment transport from north and south converges. Combined, these factors result in a positive sediment budget and seaward shoreline progradation. At the Arçay spit, high wave obliquity results in a large littoral drift and sustained longshore spit construction. At both locations, low gradient shorefaces may have favoured a net landward‐directed sediment flux that supply sand to the foreshore.

Investigation of solution structures in a nonlinear electric transmission network incorporating dissipative elements through physical phenomena analysis

This paper presents an innovative approach to solving the voltage equation in a multi-coupled nonlinear transmission network with dissipative elements. By employing the G′G2 -expansion method and fractional derivatives, we explore the behavior of current and voltage, considering memory effects. Our investigation delves into the impact of fractional calculus on signal transmission, revealing insights into period, amplitude, and propagation direction. Additionally, we analyze the influence of obliqueness angles and various fractional-order derivatives on voltage waveforms Stability analysis demonstrates the significant role of dissipative elements and modulation parameters on signal stability and network resistance to interference. Furthermore, we examine the effects of free parameters on signal transmission characteristics. Our findings highlight the intricate interplay between fractional order, wave obliqueness, and physical parameters on voltage propagation, addressing gaps in previous research.

Key Factors Determining Nightside Energetic Electron Losses Driven by Whistler‐Mode Waves

AbstractEnergetic electron losses by pitch‐angle scattering and precipitation to the atmosphere from the radiation belts are controlled, to a great extent, by resonant wave particle interactions with whistler‐mode waves. The efficacy of such precipitation is primarily modulated by wave intensity, although its relative importance, compared to other wave and plasma parameters, remains unclear. Precipitation spectra from the low‐altitude, polar‐orbiting ELFIN mission have previously been demonstrated to be consistent with energetic precipitation modeling derived from empirical models of field‐aligned wave power across a wide swath of local‐time sectors. However, such modeling could not explain the intense, relativistic electron precipitation observed on the nightside. Therefore, this study aims to additionally consider the contributions of three modifications—wave obliquity, frequency spectrum, and local plasma density—to explain this discrepancy on the nightside. By incorporating these effects into both test particle simulations and quasi‐linear diffusion modeling, we find that realistic implementations of each individual modification result in only slight changes to the electron precipitation spectrum. However, these modifications, when combined, enable more accurate modeling of ELFIN‐observed spectra. In particular, a significant reduction in plasma density enables lower frequency waves, oblique, or even quasi field‐aligned waves to resonate with near ∼1 MeV electrons closer to the equator. We demonstrate that the levels of modification required to accurately reproduce the nightside spectra of whistler‐mode wave‐driven relativistic electron precipitation match empirical expectations and should therefore be included in future radiation belt modeling.

Obliquely propagating optical wave patterns to the (2 + 1)-dimensional chiral nonlinear Schrödinger equation in the absence and presence of Atangana derivative

The study aims to explore obliquely propagating optical wave solutions to the (2 + 1)-dimensional chiral nonlinear Schrödinger (NLS) equation in both the absence and presence of the Atangana derivative. In order to convert the classical-order chiral nonlinear Schrödinger equation to an ordinary differential equation, a transformation associated with wave obliqueness is applied. Hereafter, the unified method is applied to the reduced equation. As outcomes, the dark, periodic singular with unequal wave length, periodic with equal wavelength, periodic, unsmooth periodic, singular periodic soliton solutions are received to the ordinary differential equation. Later, the acquired solutions are then put to the applied transformation associated with obliqueness. Moreover, the fractional-order chiral NLS equation is solved by using the spatiotemporal Atangana derivative with oblique wave transformation and the unified method. In terms of wave obliqueness, fractionality, and applied technique sense, all generated wave solutions are revealed to be novel. Along with their physical explanations, the impacts of obliqueness and fractionality on the solutions are graphically illustrated. It is exposed that as obliqueness and fractionality increase, the optical wave phenomena change. Additionally, it is discovered that the employed method can be used to obtain novel optical soliton features to the chiral nonlinear Schrödinger equation with or without fractional and obliqueness constraints. It can be assured that the utilized method is more powerful than the other methods. As a result, the method can be used in future research to explain the many physical phenomena that arise in optical fiber communication networks.

THE EFFECT OF WAVE OBLIQUITY ON DUNE EROSION: A FIELD EXPERIMENT

Storm conditions can lead to excessive dune erosion with potential floods as a consequence. Barrier islands and low-lying countries protected by dunes are especially vulnerable to dune erosion. To properly assess the risks these areas face, a clear understanding of the physical processes during dune erosion is required. One of such processes is the effect of wave obliquity on sediment transport in the surf zone. Classic dune erosion models assume that dune erosion volumes decrease under oblique wave attack, because the time-averaged cross-shore undertow decreases in magnitude and with that offshore directed sediment transport decreases (Steetzel, 1993). More recent process-based erosion models predict an increase in erosion quantities, because the generated longshore currents increase surf zone sediment concentrations, and with that offshore directed sediment transport increases (Den Heijer, 2013). The main objective of this study is to analyse the effect of wave obliquity on dune erosion through a field experiment, by quantifying the effect of the decreasing undertow but increasing alongshore current on sediment concentrations in the surf zone.

On the Stability of Rubble Mound Structures under Oblique Wave Attack

Slope stability formulae for rubble mound structures are usually developed for head-on conditions. Often, the effects of oblique waves are neglected, mainly because it is assumed that for oblique wave attack, the reduction in damage compared to perpendicular wave attack is insignificant. When the incident waves are oblique, the required armour size can be reduced compared to the perpendicular wave attack case. Therefore, it is important to consider the wave obliquity influence on slope stability formulae as a reduction factor. One of the most recent formulae for estimating the stability of rock-armoured slopes, referred to as Etemad-Shahidi et al. (2020), was proposed for perpendicular wave attack. The aim of this study is to develop a suitable wave obliquity reduction factor for the above-mentioned stability formula. To achieve this, first, laboratory experiment datasets from existing reliable studies were selected and analysed. Then, previously suggested reduction factors were evaluated and a suitable reduction factor for the mentioned stability formula were suggested. The suggested reduction factor includes the effect of wave obliquity and directional spreading explicitly. It is shown that the stability prediction is improved by using the wave obliquity reduction factor.

Topo-bathymetric behaviour of a beach controlled by a groyne field and a dune-seawall backshore

The advances in morphodynamics numerical modelling and the free availability of such updated models have made XBeach a powerful tool to predict the hydrodynamic and morphologic processes on sandy coasts. This paper addresses the impact of the sea-structure-sediments interactions in the morphological evolution of a coastal stretch which undergoes erosion and overtopping despite having a combined groyne field-dune-seawall defence scheme. Preliminary tests, tailored to conclude on the model mode-version to be applied in the case study, evidence the importance of considering the NH mode. After calibrated and validated, the model was applied for a set of cases to compute and discuss the effect of the individual defence scheme structural elements and the hydrodynamic driving factors, namely the wave energy and obliquity and the tidal range, on the morphodynamics. The results revealed that the seawall aggravates the erosion of the beach, despite being essential in the protection against overtopping and coastline retreat, and that the present configuration of the groyne field does not provide enough protection at the downdrift part of the stretch. The knowledge acquired can support the interpretation of the topo-bathymetric behaviour in similar coastal defence schemes existent worldwide.

Exact wave solutions and obliqueness of truncated M-fractional Heisenberg ferromagnetic spin chain model through two analytical techniques

This research is concerned to some modernistic wave solutions of truncated M-fractional Heisenberg ferromagnetic spin chains model. The collected solutions can be executed in exposing of this model in prominent form. The obtained results include the trigonometric, hyperbolic trigonometric and exponential functions. The verification of the results is also done by using Mathematica tool. Two techniques named as modified simplest equation (MSE) and Sardar sub-equation (SSE) techniques are employed to protect the results. The achieved results are also illustrated by 2-D, 3-D and contour plots for different values truncated M-fractional parameters as well as obliqueness. The gained results can also be fruitful for the development of model in the future.

Dynamical behaviours and fractional alphabetical-exotic solitons in a coupled nonlinear electrical transmission lattice including wave obliqueness

Dynamical behaviours and fractional alphabetical-exotic solitons in a coupled nonlinear electrical transmission lattice including wave obliqueness

On the properties of Alfvénic switchbacks in the expanding solar wind: The influence of the Parker spiral

Switchbacks—rapid, large deflections of the solar wind's magnetic field—have generated interest as possible signatures of the mechanisms that heat the corona and accelerate the solar wind. In this context, an important task for theories of switchback formation and evolution is to understand their observable distinguishing features, allowing them to be carefully assessed using spacecraft data. Here, we work toward this goal by studying how Alfvénic switchbacks evolve in the expanding solar wind beyond the Alfvén radius, when the background magnetic field also rotates due to the Parker spiral. Using simple analytic arguments based on the physics of one-dimensional spherically polarized (constant-field-magnitude) Alfvén waves, we find that, by controlling the wave's obliquity, a Parker spiral strongly impacts switchback properties. Surprisingly, parallel magnetic-field deflections (switchbacks) can grow faster in a Parker spiral than in a radial background field, even though normalized wave amplitudes grow more slowly. In addition, switchbacks become strongly asymmetric: large switchbacks preferentially involve magnetic-field rotations in the plane of the Parker spiral (tangential deflections) rather than perpendicular (normal) rotations, and such deflections are strongly “tangentially skewed,” meaning switchbacks always involve field rotations in the same direction (toward the positive-radial direction for an outward mean field). In a companion paper [Johnston et al., Phys. Plasmas 29, 072902 1346 (2022)], we show that these properties also occur in turbulent 3D fields with switchbacks, given various caveats. Given that these nontrivial asymmetries and correlations develop purely as a consequence of switchback propagation in the solar wind, our results show that in situ observed asymmetrical switchback features cannot be used straightforwardly to infer properties of sources in the low corona.

Hydrodynamic characteristics of a flexible floating anti-collision system under beam and oblique irregular waves

An experimental investigation on the coupled dynamics of a flexible floating anti-collision system is conducted to explore its violent responses in harsh wave conditions. Subjected to beam and oblique irregular waves, the buoy motions and mooring/connecting tensions are measured synchronously in a wave basin. The correlation between the relative motion of adjacent buoys and the connecting lines’ tensions is clarified considering various peak wave periods and significant wave heights. Particular attention is also paid on the strong nonlinearities of the connecting line tensions, which is closely associated with the relative surge and pitch between adjacent buoys. Based on the frequency spectra analysis, it is found that this multiple-wave-frequency characteristic is significantly affected by the wave obliquity, which provokes pronounced spikes in the connecting tensions for the heading angel of 45–90 deg. It is also demonstrated that the relative motions and the connecting tensions would be intensified due to wave conditions of shorter period.

Wave RUN-UP Measurements under very oblique wave incidence

Under the scope of the HYDRALAB+ transnational access project, the so-called RODBreak experiment was conducted in the multidirectional wave basin at the Marienwerden facilities of the Leibniz University Hannover (LUH). A stretch of a rubble-mound breakwater was built in the wave basin with a very gentle slope. Its armour layer was made of Antifer cubes, at the roundhead and adjoining trunk, and of rock, at the rest of the trunk. A set of tests was carried out to extend the range of wave steepness values analysed in wave run-up, overtopping and armour layer stability studies, focusing on oblique extreme wave conditions, with incident wave angles from 40º to 90º. The present study focuses on the analysis of measured wave run-up values obtained in the tests and on their on their variability as well as the influence of the wave obliquity and directional spreading. Keywords: rubble-mound breakwaters; run-up; oblique waves; physical modelling; RODbreak.

Coupled motion characteristics of a large-scale tunnel element suspended by immersion rigs in the vicinity of seabed

During the near-seabed immersion stage, the submerged tunnel element suspended by immersion rigs and anchored to the seabed is at risk of possible bottom grounding and collision with the installed elements. Specifically, the wall effect would have an important role on the motion characteristics of the tunnel element when it approaches the seabed (The wall effect is the influencing behavior of one large planar surface approaching another large planar surface underwater). To investigate this effect, this research conducts 3D experiments using a 1:60 scale model of a combined tunnel element and immersion rig system. The six-DOF motions of the tunnel and immersion rig are measured simultaneously for various regular wave conditions. The collected measurements for different relative clearances are compared in both time and frequency domain. Nonlinear effects of the near-seabed interference are found to be particularly significant when the relative clearance ratio (clearance beneath tunnel / height of tunnel element) is smaller than 0.26, especially when the incident wave period is near the resonant roll period of the tunnel/rigs. To further explore the contributing factors of the seabed interference and to determine suitable operating conditions in practice, a fully coupled tunnel-rig numerical model is built based on the potential flow theory. Additional damping is also included in the coupled motion equations for the resonant roll scenarios and good agreement with experimental data is achieved for relative clearance ratio of δ/d ≥ 0.42. Overall, the experimental and numerical results demonstrate that besides the relative clearance, the near-wall effect of the seabed is also closely associated with the roll of the tunnel element and thereby has a strong dependence on the incident wave height, wave period and wave obliquity. The study is expected to be helpful for understanding the near-seabed effect on the responses of large-scale rectangular floater so that the installation and positioning can be performed accurately and effectively.

Optical solutions to the Kundu-Mukherjee-Naskar equation: mathematical and graphical analysis with oblique wave propagation

This paper retrieves some new optical solutions to the Kundu–Mukherjee–Naskar (KMN) equation in the context of nonlinear optical fiber communication systems. In this regard, a complex transformation is applied to the integer-order KMN equation for converting it to an ordinary differential equation (ODE). Then, the generalized Kudryashov method (gKM) and the new auxiliary equation method (NAEM) are employed to the ODE. As consequence, dark, bright, periodic -shaped, and singular soliton solutions are explored to the ODE. The discrepancies between the results obtained in the present study and the previously obtained solutions through different methods are discussed. Furthermore, the time-fractional derivative and an oblique wave transformation in conjunction with the mentioned methods are executed to the fractional-order KMN equation. All obtained wave solutions are found to be new in terms of fractionality, wave obliqueness, and applied methods sense. The effects of obliqueness and fractionality on the attained solutions are demonstrated graphically along with its physical descriptions. It is found that the optical wave phenomena are changed with the increase of obliqueness as well as fractionality. It is also found that both the applied methods are suitable for acquiring new optical soliton features to the KMN equation with or without fractional and obliqueness conditions. However, the NAEM is capable of exploring more solutions of the considered equation over the gKM. Precisely, it can be assured that the utilized methods and the relevant transformation are powerful over the other methods. Therefore, the methods can be applied for further studies to explain the various physical phenomena arising in optical fiber communication systems.

On the propagation of alphabetic-shaped solitons to the (2 + 1)-dimensional fractional electrical transmission line model with wave obliqueness

This manuscript deals with the (2 + 1)-dimensional nonlinear electrical transmission line (NETL) equation of fractional-order to explain the dynamics of waves in the nonlinear network lines. The fractional transform with conformable derivative and wave obliqueness is applied to the model equation for converting it into an ordinary differential equation (ODE). To explore alphabetic-shaped solitons, an ansatz and the auxiliary equation methods are utilized to the ODE. The utilized transformation is then put back to the received solutions of the ODE. The solutions of the model equations representing alphabetic solitons are attained in terms of fractionality and wave obliqueness. It is seen that some of the beforehand generated solutions are the particular case of the newly derived solutions. The effects of fractionality, obliqueness, and free parameters on the attained solutions are tested and are demonstrated graphically with physical descriptions. Also, the behavior of the voltage wave propagation of the attained solutions are described. It is found that the alphabetic wave phenomena are changed with the change of obliqueness and fractionality, and the free parameters have substantial effects on the attained solutions. All the attained solitons propagate in the xy-plane as time (t) increases and the soliton propagation is found to be controlled by the free parameters, fractionality, and wave obliqueness. All the reported alphabetic-shaped solitons are found to be new in the sense of conformable derivative, wave obliqueness, and the applied methods.

High‐Energy Surf Zone Currents and Headland Rips at a Geologically Constrained Mesotidal Beach

AbstractWe analyze Eulerian and Lagrangian measurements of wave‐induced circulation collected during a 3‐week field experiment at a high‐energy mesotidal barred beach with the presence of a 500‐m headland and a submerged reef. Small changes in wave and tide conditions were found to largely impact circulation patterns. Three main regimes were identified depending on offshore wave obliquity: (1) Under shore‐normal configuration, the flow was dominated by cross‐shore motions, except for moderate waves at low tide, with the presence of a quasi‐steady circulation cell on the reef. (2) Under shadowed configuration, an onshore‐directed current flowing away from the headland and a weak oscillating eddy were present outside and inside the shadow region, respectively. (3) Under deflection configuration, a deflection rip flowing against the headland and extending well beyond the surf zone was present, with activity maximized around low tide for moderate waves. Under 4‐m oblique waves, the deflection rip was active regardless of the tide with mean depth‐averaged velocities up to 0.7 m/s 800‐m offshore in 12‐m depth, with energetic low‐frequency fluctuations. Our results emphasize the ability of deflection rips to transport materials far offshore, suggesting that such rips can transport sediment beyond the depth of closure. This study indicates that a wide variety of wave‐driven circulation patterns can occur and sometimes coexist on beaches with prominent geological settings. Changes in the dominant driving mechanism can occur as a result of small changes in wave and tide conditions, resulting in more spatially and temporally variable circulation than along open sandy beaches.

Reduction of Wave Overtopping and Force Impact at Harbor Quays Due to Very Oblique Waves

Physical model experiments were conducted in a wave tank at Flanders Hydraulics Research, Antwerp, Belgium, to characterize the wave overtopping and impact force on vertical quay walls and sloping sea dike (1:2.5) under very oblique wave attack (angle between 45° and 80°). This study was triggered by the scarce scientific literature on the overtopping and force reduction due to very oblique waves since large reduction is expected for both when compared with the perpendicular wave attack. The study aimed to compare the results from the experimental tests with formulas derived from previous experiments and applicable to a Belgian harbor generic case. The influence of storm return walls and crest berm width on top of the dikes has been analyzed in combination with the wave obliqueness. The results indicate significant reduction of the overtopping due to very oblique waves and new reduction coefficients were proposed. When compared with formulas from previous studies the proposed coefficients indicate the best fit for the overtopping reduction. Position of the storm return wall respect to the quay edge rather than its height was found to be more important for preventing wave induced overtopping. The force reduction is up to approximately 50% for the oblique waves with respect to the perpendicular wave impact and reduction coefficients were proposed for two different configurations a sea dike and vertical quay wall, respectively.

An adjoint compressible linearised Navier–Stokes approach to model generation of Tollmien–Schlichting waves by sound

The generation of the first-mode instability through scattering of an acoustic wave by localised surface roughness, suction or heating is studied with a time-harmonic compressible adjoint linearised Navier–Stokes (AHLNS) approach for subsonic flow conditions. High Strouhal number analytical solutions to the compressible Stokes layer problem are deduced and shown to be in better agreement with numerical solutions compared to previous works. The adjoint methodology of Hill in the context of acoustic receptivity is extended to the compressible flow regime and an alternative formulation to predict sensitivity to the angle of incidence of an acoustic wave is proposed. Good agreement of the acoustic AHLNS receptivity model is found with published direct numerical simulations and the simpler finite Reynolds number approach. Parametric investigations of the influence of the acoustic wave angle on receptivity amplitudes reveal that the linearised unsteady boundary layer equations are a valid model of the acoustic signature for a large range of acoustic wave obliqueness values, failing only where the wave is highly oblique and travels upstream. An extensive parametric study of the influence of frequency, spanwise wavenumber, local Reynolds number and free-stream Mach number over the efficiency function for the different types of wall perturbation mechanisms is undertaken.

Experimental investigation on the coupling between immersion rig and tunnel element during freeboard elimination

This study aims to investigate the coupled mechanism of the tunnel immersion system during freeboard elimination, one of the most critical scenarios for submerged tunnel construction. To address the coupling effect, synchronous measurements have been conducted on the tunnel/rig motions and the suspension tensions during freeboard elimination. The motion characteristics of the tunnel at zero-freeboard and immersion rigs are compared under regular and random waves. The effects of the wave period, wave height and wave obliquity on the dynamic responses of the system are examined. The results indicate that the coupling effect between the tunnel and rig is not only subjected to the wave height, but also the wave period. In particular, the most critical downward displacement of the tunnel and suspension tension were observed at the natural roll period of the coupled system T = Troll. In addition, green water has a significant effect on the downward displacement of the tunnel and leads to severe relative heave and critical dynamic suspension tensions.

River bank protection from ship-induced waves and river flow

A new equation is proposed for the design of armor units on protected river banks under the combined action of ship-induced waves and river flow. Existing observed field and experimental data in the literature have been examined and a valuable database has been developed. Different conditions, including the river water depth, flow velocity, river bank slope, Froude number, wave height, wave period, and wave obliquity have been considered. Results from an empirical equation (Bhowmik, 1978) that only considers the maximum wave height and river bank slope have been compared with the results calculated by the newly developed equation. Calculated results have also been verified against field data. Results show that not only the maximum wave height and river bank slope but also the water depth, flow velocity, wave length, wave obliquity, and wave period are important parameters for predicting the mean diameter of the armor units, highlighting the multivariate behavior of protecting the river bank in the presence of ship-induced waves and river flow velocity.