Generation Of Waves Research Articles

Gravitational wave signatures of first-order phase transition in two-component dark matter model

Here, we consider a classically scale-invariant extension of the Standard Model (SM) with two-component dark matter (DM) candidates, including a Dirac spinor and a scalar DM. We probe the parameter space of the model, constrained by relic density and direct detection, and investigate the generation of gravitational waves (GWs) produced by an electroweak first-order phase transition. The analysis demonstrates that there are points in the parameter space, leading to a detectable GW spectrum arising from the first-order phase transition, which is also consistent with the DM relic abundance and direct detection bounds. These GWs could be observed by forthcoming space-based interferometers such as the Big Bang Observer, Decihertz Interferometer Gravitational-wave Observatory, and Ultimate-Decihertz Interferometer Gravitational-wave Observatory. Published by the American Physical Society 2024

Time-dependent wave motion in a running stream due to initial disturbances in Magnetohydrodynamics

Abstract The generation of two-dimensional time-dependent magneto-hydrodynamic surface waves in a flowing stream is investigated in this paper. The waves here arise from some initial disturbances at the free surface of an electrically conducting field-free fluid, which is of finite depth. It is also assumed that a constant magnetic field exists outside the air-water interface. With the help of linearised theory, the present problem is modeled as an initial boundary value problem, and the Laplace-Fourier transform techniques are primarily used to obtain the form of free surface elevation through infinite integrals. These integrals are then interpreted asymptotically for large time t and distance x from the origin, using the method of stationary phase. Dispersion relation, phase, and group velocities are also studied. Numerical results of the asymptotic form of free surface elevation are obtained in a number of figures for different values of current speed, Alfven velocity, and various types of initial disturbances. Graphical representations demonstrate that the presence of a magnetic field has a significant effect on wave motion.

Efficient Second-Harmonic Generation in Thin-Film Lithium Tantalate Through Modal Phase-Matching

Lithium tantalate (LT) exhibits nonlinear optical properties that are comparable to those of lithium niobate (LN), yet the former surpasses the latter in several respects. These include an enhanced optical damage threshold, a wider transparency range, and lower birefringence. Consequently, LT is an excellent material for optical frequency conversion applications. In this study, we have devised a novel device based on thin-film lithium tantalate (TFLT) for the efficient generation of second-harmonic waves. The design employs modal phase-matching (MPM), which circumvents the intricacies of conventional poling techniques, and attains a normalised conversion efficiency of 120% W−1cm−2. In order to address the challenges presented by higher-order modes, a mode converter with an insertion loss of less than 0.1 dB has been developed, thereby ensuring the efficient utilisation of the second harmonic. This study not only demonstrates the potential of TFLT for high-performance SHG, but also promotes the development of integrated nonlinear TFLT platforms.

Simulating waves induced by landslide using coupled smoothed particle hydrodynamics and discrete element method: Evaluating the impact of irregular rock shapes

The morphology of rock plays an important role in the process of landslide-induced wave, yet it is often neglected in current studies. This work aims to fill this gap by investigating the impact of irregular rock shapes on landslide-induced wave generation and propagation via coupling smooth particle fluid dynamics and discrete element method from a multi-scale perspective. Initially, the wave induced by particle column collapse is reproduced and validated against existing results. Subsequently, the influence of rock shapes, particularly the aspect ratio of particles on landslide-induced waves, is analyzed. The findings indicate that spherical particles, due to their low self-locking tendency and simple force chain structure, exhibit higher average velocities and more stable velocity changes during the landslide process. Spherical particles generate larger free surface waves with smoother and more regular waveforms when entering the water. In contrast, irregular polyhedral particles produce multiple secondary wave peaks alongside the main wave. The wave height induced by these particles is negatively correlated with aspect ratio. Specifically, the maximum run-up height of waves generated by elliptical particles with the highest aspect ratio is 11.7% lower than that of spherical particles. This research highlights the influence mechanism of particle morphology on landslide and tsunami dynamics, which provides a theoretical foundation for disaster prediction and assessment.

Tsunami debris motion and loads in a scaled port setting: Comparative analysis of three state-of-the-art numerical methods against experiments

We present an international comparative analysis of simulated 3D tsunami debris hazards, applying three state-of-the-art numerical methods: the Material Point Method (MPM, ClaymoreUW, multi-GPU), Smoothed Particle Hydrodynamics (SPH, DualSPHysics, GPU), and Eulerian grid-based computational fluid dynamics (Simcenter STAR-CCM+, multi-CPU/GPU). Three teams, two from the United States and one from Germany, apply their unique expertise to shed light on the state of advanced tsunami debris modeling in both open source and professional software. A mutually accepted and meaningful benchmark is set as 1:40 Froude scale model experiments of shipping containers mobilized into and amidst a port setting with simplified and generic structures, closely related to the seminal Tohoku 2011 tsunami case histories which majorly affected seaports. A sophisticated wave flume at Waseda University in Tokyo, Japan, hosted the experiments as reported by Goseberget al. (2016b). Across dozens of trials, an elongated vacuum-chamber wave surges and spills over a generic harbor apron, mobilizing 3–6 hollow debris -modeling sea containers-, in 1–2 vertical layers against friction. One to two rows of 5 square obstacles are placed upstream or downstream of the debris, with widths and gaps of 0.66x and 2.2x of debris length, respectively. The work reports and compares results on the long wave generation from a vacuum-controlled tsunami wave maker, longitudinal displacement of debris forward and back, lateral spreading angle of debris, interactions of stacked debris, and impact forces measured with debris accelerometers and/or obstacle load-cells. Each team writes a foreword on their digital twin model, which are all open-sourced. Then, preliminary statistical analysis contrasts simulations originating off different numerical methods, and simulations with experiments. Afterward, team’s give value propositions for their numerical tool. Finally, a transparent cross-interrogation of results highlights the strengths of each respective method.

Low‐Frequency Whistler Waves Excited by Electron Butterfly Distributions in Turbulent Reconnection Outflow

AbstractWhistler waves, leading to electron scattering and energy transport, are frequently observed in magnetic reconnection. High‐energy electrons produced by magnetic reconnection are expected to excite low‐frequency whistler waves. However, the study on low‐frequency whistler waves in magnetic reconnection is still quite scarce. Utilizing high‐resolution data from the Magnetospheric Multiscale (MMS) mission, we provide observations of low‐frequency whistler waves in a turbulent reconnection outflow. The quasi‐antiparallel propagating whistler waves have power peaked at ∼0.1 and wave number of ∼0.43 in the plasma rest frame. It can be excited through the cyclotron resonance by the electron butterfly distributions, which can be interpreted by a model comprising the addition of electron beams hosting perpendicular anisotropy to electron isotropy distributions. The energy of resonant electrons is calculated as 1.06∼4.16 keV, the parts corresponding to lower frequency (<∼0.1) falling into suprathermal energy range. Our study can promote the understanding of generation of whistler waves in magnetic reconnection.

Generation of Fast Magnetoacoustic Waves in the Corona by Impulsive Bursty Reconnection

Fast-mode magnetohydrodynamic waves in the solar corona are often known to be produced by solar flares and eruptive prominences. Here, we simulate the effect of the interaction of an external perturbation on a magnetic null in the solar corona, which results in the formation of a current sheet (CS). Once the CS undergoes a sufficient extension in its length and squeezing of its width, it may become unstable to the formation of multiple impulsive plasmoids. Eventually, the plasmoids merge with one another to form larger plasmoids and/or are expelled from the sheet. The formation, motion, and coalescence of plasmoids with each other and with magnetic Y-points at the outer periphery of the extended CS are found to generate wavelike perturbations. An analysis of the resultant quasiperiodic variations of pressure, density, velocity, and magnetic field at certain locations in the model corona indicates that these waves are predominantly fast-mode magnetoacoustic waves. For typical coronal parameters, the resultant propagating waves carry an energy flux of 105 erg cm−2 s−1 to a large distance of at least 60 Mm away from the CS. In general, we suggest that both waves and reconnection play a role in heating the solar atmosphere and driving the solar wind and may interact with one another in a manner that we refer to as a “symbiosis of waves and reconnection.”

New Generation Site and Estimated Propagation of Nonlinear Internal Waves Under Varying Background Stratification in the Northeastern East China Sea

AbstractThis study investigates the generation and propagation of nonlinear internal waves (NLIWs) in the northeastern East China Sea (ECS), focusing on the impact of time‐varying background stratification. Using satellite imagery and tide‐generating body force, 327 groups of NLIWs were identified from 93 MODIS images collected between 2015 and 2019 and classified into three distinct types based on their propagation directions—Type‐A (∼42%), Type‐B (∼38%), and Type‐C (∼20%)—each originating from different generation sites. Type‐B NLIWs were found to originate from a newly identified site near southwestern Fukue Island reported here for the first time, whereas Type‐A and Type‐C originated from the northern Okinawa Trough and southwestern Jeju Island, respectively. Seasonal variations in NLIW propagation speed using historical CTD data revealed an increase in the speed from winter to spring and fall, peaking in summer due to strong stratification. Although spatial distribution varied by season, propagation was generally faster in the eastern region than in the western region attributed to deeper thermoclines and higher density gradients. During field observation in May 2015, the observed NLIWs had an amplitude of 5–6 m, a characteristic width of 380–450 m, southwestward propagating directions, and a speed of ∼0.54 m s−1. An empirical model, used to track and predict these waves, confirmed their generation locations from southwestern Fukue Island (Type‐B) and indicated fast arrival speeds, influenced by time‐varying stratification conditions during the stratification period. These findings highlight the impacts of varying background conditions on NLIW propagation and would facilitate their prediction.

Dynamic analysis of the air–water interface instability in a wind-wave flume: Initial conditions for wave generation

This paper aims to investigate the dynamic mechanism for a previously calm water surface under a background wind field, which would lose stability due to minor perturbations. When spatial distribution and growth rate of the shear wind field satisfy a certain relationship, an Orr–Sommerfeld equation can be derived from linearized Navier–Stokes equations, for the amplitude of perturbation waves at the air–water interface. After transforming its coordinates to a finite interval, this fourth-order linear ordinary differential equation with variable coefficients can turn into a linear singular differential equation. It is solved under the background flow fields of air and water using the corrected Fourier method that we previously developed, to yield two sets of four analytical solutions with physical significance. The perturbation flow at the air–water interface must satisfy the kinematic and dynamic matching conditions (continuity of velocity and smooth transition of shear stress), which results in a fourth-order homogeneous linear algebraic equation for four undetermined constants. Setting various parameters in accordance with measured data with a wind-wave flume, the corresponding perturbation waves solution is identified. Our calculation densely distributes the most unstable and readily growing waves among perturbation waves with small phase speeds, consistent with the experimental results. Our perturbation solutions over a flat air–water interface are only applicable to the short period after instability onset, which provides an initial condition for wave generation. The consequent interaction between small-amplitude waves and wind field is beyond the scope of our linear theory, which has indeed been sufficiently addressed in the literature.

Ultra-Wideband and Multi-Octave Tunable Millimeter Wave Generation Based on Photonic Multiplication and Delay-Matched Heterodyne

Ultra-Wideband and Multi-Octave Tunable Millimeter Wave Generation Based on Photonic Multiplication and Delay-Matched Heterodyne

Lamb wave S0/A0 mode conversion for imaging the internal structure of composite panel

Stiffened structures are utilised in various industries and their structural assessment is of paramount importance. In this paper, a novel, automated algorithm for internal structure imaging based on S0/A0 mode conversion effect is proposed. Moreover, a contrast indicator for the quantitative characterisation of structure imaging results was introduced. The research is exclusively experimental and focuses on fibre-reinforced, stiffened aerospace composite panel. Both non-contact (air-coupled transducer-ACT) and contact (piezoelectric transducer-PZT) methods of elastic wave generation were investigated. Low-frequency (40 kHz) wave generation was applied to ACT and PZT, while high-frequency excitations (100 kHz and 180 kHz) were analysed for the PZT. The results obtained for both excitation methods were compared. Full wavefield signals of elastic wave propagation were registered with a scanning laser Doppler vibrometer. The S0/A0 mode conversion observed on the specimens stiffeners led to the development of a new algorithm based on time–space guided wave signal filtering, which enables the imaging of the internal structure of the stiffened panel. The efficacy of the developed algorithm was proved to be higher than conventional weighted RMS (WRMS) and wave irregularity mapping (WIM) algorithms. The proposed method allows for the generation of easily interpretable maps illustrating discontinuities in the examined structure. The contrast indicator is two times higher for the proposed MCWA than for WRMS and WIM for wave frequency 100 kHz and three times higher for frequency 180 kHz.

Wave climate projections off coastal French Guiana based on high-resolution modelling over the Atlantic Ocean

Global warming is altering the atmosphere and ocean dynamics worldwide, including patterns in the generation and propagation of ocean waves, which are important drivers of coastal evolution, flood risk, and renewable energy. In French Guiana (northern South America), where most of the population is concentrated in coastal areas, understanding future wave climate change is critical for regional development, planning and adaptation purposes. The most energetic waves typically occur in boreal winter, in the form of long-distance swell originating from the mid-latitude North Atlantic Ocean. However, existing high-resolution wave climate projections that cover the French Guiana region focus on the hurricane season only (summer-fall). In this study, we used a state-of-the-art basin-scale spectral wave model and wind fields from a high-resolution atmospheric global climate model to simulate present and future winter (November to April) wave climate offshore of French Guiana. The model performance was evaluated against wave data from ERA5 reanalysis, satellite altimetry and coastal buoys between 1984 and 2013. For the future greenhouse gas emission scenario (Representative Concentration Pathway) RCP-8.5, we found a statistically significant overall projected decrease (∼5 %) in wintertime average significant wave height and mean wave period, with a ∼1° clockwise rotation of mean wave direction. The results suggest that these decreasing trends are primarily driven by changes in large-scale patterns across the Atlantic that counteract an expected increase in local wind speed. We discuss the implications of such projections for mud-bank dynamics along coastal French Guiana, although further local studies are required to address future coastal evolution and hazards. Finally, we identify a need for more in situ wave data near French Guiana to improve quantitative assessments of model performance and allow a correction of possible model biases.

CONSTRUCTION OF EARTH CRUST SECTIONS DOWN TO THE MOHO BOUNDARY BASED ON LOW AMPLITUDE REFLECTED WAVES OF RIVER SEISMIC SURVEY USING CPD-2D METHOD (Vitim River, junction zone of the Angara-Lena monocline of the Siberian platform and the Bodaibo-Patom folded system)

In 2019, employees of the Research and Production Enterprise Luch jointly with specialists of the Seismological Branch of the Geophysical Survey of the Russian Academy of Sciences (GS RAS) carried out river seismic exploration works using the common depth point method (CDP-2D) along a 170 km long profile in the lower reaches of the Vitim River. The research was carried out according to the original methodology developed in the Siberian branches of the GS RAS, using the “Baikal” equipment recording seismic signals continuously (in contrast to traditional cable bottom or ground-based systems with time-limited recording). In this case, patented air guns “Malysh” were used in the water for the excitation of elastic waves, which have been recorded by ground registration method on the riverbank. To this day, the archives store primary materials from each receiving point (about 7000, with a distance of 25 m between them) in the form of a continuous hours-long digital recording of seismic signals and noise. These materials make it possible to generate seismograms of significant duration – up to 23 s, equal to the time interval between wave generations, in contrast to 6–10 second seismograms traditionally used to construct sections of the upper part of the Earth’s crust. In addition, the 24-bit Baikal recorder makes it possible to record signals with an amplitude two orders of magnitude lower than the amplitude of seismic noise. On the seismic sections constructed by the processor at arrival times of up to 13–14 sec, due to an increase in the stack fold of signals up to 1000–2000, we can select low-amplitude waves, reflected from boundaries in the middle and lower parts of the Earth’s crust to the Moho boundary. High fold is achieved by increasing the size of the stacking site (bin) by several times. By processing seismograms, generated from archival materials, for the first time, we have a complete vertical section of the Earth’s crust along a 170 km long profile, using low-amplitude signals. The profile passes through the junction zone of the Angara–Lena monocline and the Bodaibo-Patom folded system. The proposed approach can be used to obtain preliminary (and relatively cheap) information about the deep structure of the Earth’s crust along profiles performed using the CDP-2D river seismic exploration method.

Surface Acoustic Waves-Enabled Shielding Fluid Layers Inhibit Bacterial Adhesion.

The generation of surface acoustic waves (SAW) through electrically driven piezoelectric devices has attracted considerable attention in both fundamental research and practical applications, particularly for suppressing bacterial adhesion on surfaces. However, the precise mechanism by which SAW prevents bacterial attachment remains incompletely understood. This study explores the impact of SAW-induced boundary-driven streaming on the surface adhesion of Escherichia coli and Staphylococcus aureus in a liquid environment, focusing on the prevention of bacterial adhesion through the formation of micrometer-scale shielding fluid layers. We primarily examine the distance and acoustic streaming effects that influence bacterial behavior in the flow field. Our in vitro experiments, supported by numerical simulations, demonstrate that the viscous boundary layer and vortices generated by SAW can inhibit bacterial colonization and biofilm formation when Stokes drag forces predominate. This work provides new insights into the inhibitory mechanism of SAW on bacterial adhesion, offering valuable guidance for the development of advanced antibacterial strategies.

Ground motion characteristics of subshear and supershear ruptures in the presence of sediment layers

SUMMARY We investigate the impact of sediment layers on ground motion characteristics during subshear and supershear rupture growth. Our findings suggest that sediment layers may lead to local supershear propagation, affecting ground motion, especially in the fault parallel (FP) direction. In contrast to homogeneous material models, we find that in the presence of sediment layers, a larger fault normal (FN) compared to FP particle velocity jump, reflects shear propagation at depth but does not rule out shallow supershear propagation. Conversely, a large FP compared to FN particle velocity jump indicates supershear propagation at depth. In the presence of a shallow layer, we also uncover a non-monotonic behaviour in the sediment’s influence on supershear transition and ground motion characteristics. During supershear propagation at depth we observe that sediment layers contribute to enhancing FP velocity pulses while minimally affecting the FN component. Furthermore, in the limit of global supershear propagation we identify local supersonic propagation within the sediment layers that significantly alters the velocity field around the rupture tip as observed on the free surface, creating both dilatational and shear Mach cones. In all our models with sediments we also find a significant enhancement in the fault vertical component of ground velocity. This could have particular implications for hazard assessments, such as in applications related to linear infrastructure, or a higher propensity to tsunami wave generation. Our research unravels the importance of considering heterogeneous subsurface material distribution in our physical models as they can have drastic implications on earthquake source physics.

Numerical Analysis of the Possibility of High-Speed Screw Feeding of Charges for Solid-Fuel Shock Wave Generators

Numerical Analysis of the Possibility of High-Speed Screw Feeding of Charges for Solid-Fuel Shock Wave Generators

Array Optimization for a Wave Energy Converter with Adaptive Resonance Using Dual Bayesian Optimization

A novel Dual Bayesian optimization strategy is formed for an array of wave energy converters with adaptive resonance to maximize the annual performance through the energy conversion processes from irregular waves to electricity. A wave energy converter with adaptive resonance changes the natural frequency of power take-off dynamics for varying irregular waves, resulting in the maximum annual energy production. The first step of the two-step Dual Bayesian optimization determines the geometric layout of the array, which maximizes the first energy conversion to the total array excitation for irregular waves occurring annually. The second step optimizes the operational parameters of individual wave energy converters in the optimized array to maximize the power generation in varying sea states through simultaneous conversion to mechanical and electrical energy. The coupled hydrodynamics are solved in the frequency domain, and the power performance is evaluated by solving the Cummins’ equation in the time domain extended for multiple floating bodies, each strongly coupled with nonlinear power take-off dynamics. The proposed method is applied to a surface-riding wave energy converter, already optimized for single unit operation at individual sea states. Investigating two array layouts, linear and random, the optimized arrays after Step 1 increase the excitation spectral area by up to 40% relative to the single unit operation, indicating the synergy enhancing the first energy conversion. Subsequently, the dual-optimized linear layout attained a q-factor up to 1.13 in commonly occurring sea states, achieving improved average power generation in 60% of the evaluated sea states. The performance of the random layout exhibited the average power fluctuating along the wave spectra with a peak q-factor of 1.07. The individual adaptive resonance is confirmed in the optimized arrays, such that each surface-riding wave energy converter of both layouts adaptively resonates with the peak of the wave excitation spectra, maximizing the power generation for the different irregular waves.

Isotropization by shock waves generation in anisotropic hydrodynamics

Anisotropic hydrodynamics (aHydro) has proven successful in modeling the evolution of quark-gluon matter created in heavy-ion collisions. The hydrodynamic description of quark-gluon plasma has also been widely used to study sound phenomena, such as shock waves. It has recently been shown that initial fluctuations in energy density and supersonic partons can generate fairly strong shock waves. However, significant anisotropic properties of the system due to the rapid longitudinal expansion of matter have not been taken into account in such studies. Moreover, the process of isotropization and its characteristic time-scales were not considered along with the question of the shock waves formation. Previous studies on shock discontinuous solutions in anisotropic hydrodynamics assumed constant anisotropy, leading to flow refraction towards the anisotropy axis and flow acceleration, characteristics of rarefaction waves, indicating limitations in this approach. This paper investigates discontinuous solutions for normal shock waves without flow refraction, introducing two compression parameters for longitudinal and transverse pressures. The resulting analytical solutions, as well as numerical computations, provide an isotropization mechanism of the system.

Генерация незатухающих тепловых волн и их влияние на удаленные и экранированные мишени дейтерированного титана

The paper experimentally studies and theoretically substantiates the conditions and features of generation of undamped thermal waves during water cavitation, which are associated with the features of the relaxation processes of such waves in the air. The minimum frequency of such waves at normal pressure and air temperature corresponds to 70-80 MHz. It is shown that the interaction of a traveling thermal wave in the air with the front surface of a metal screen leads to the formation of strong acoustic waves in its volume. In the experiments, samples of deuterated titanium removed and shielded by a metal plate, in which the concentration of deuterium was 1.5 times higher than the concentration of basic titanium nuclei, were exposed to high-frequency thermal waves. The states of deuterium nuclei located in a potential well in the titanium lattice as a result of this impact were studied.

Survey of Whistler‐Mode Wave Amplitudes and Frequency Spectra in Jupiter's Magnetosphere

AbstractWe present statistical distributions of whistler‐mode chorus and hiss waves at frequencies ranging from the local proton gyrofrequency to the equatorial electron gyrofrequency (fce,eq) in Jupiter's magnetosphere based on Juno measurements. The chorus wave power spectral densities usually follow the fce,eq variation with major wave power concentrated in the 0.05fce,eq–fce,eq frequency range. The hiss wave frequencies are less dependent on fce,eq variation than chorus with major power concentrated below 0.05fce,eq, showing a separation from chorus at M < 10. Our survey indicates that chorus waves are mainly observed at 5.5 < M < 13 from the magnetic equator to 20° latitude, consistent with local wave generation near the equator and damping effects. The hiss wave powers extend to 50° latitude, suggesting longer wave propagation paths without attenuation. Our survey also includes the whistler‐mode waves at high latitudes which may originate from the Io footprint, auroral hiss, or propagating hiss waves reflected to high M shells.