Wave Surface Research Articles

Анализ интерферометра с микрозеркалом на светоделительном кубике

The control of the shape of the optical part surface by the interference method has become an integral part of the process of their shaping. With a precisely focused interferometer interferometry allows obtaining an interference pattern similar to a topographic map of the error profile of the wave surface under investigation. The interferometer must form a map of the optical surface with high accuracy --- the permissible distortion of the interference fringe caused by an interferometer error should not exceed 0.1 of the distortion value caused by an error on the examined surface. The dependence of the interference pattern formation on the errors in the arrangement of the interferometer components, i.e., defocusing, was theoretically analyzed using Fourier transforms. The analysis was performed for an interferometer containing a laser illuminator, a concave spherical mirror with a central hole, coaxial to the illuminator, and a beamsplitting element in the form of a cube-prism with a semitransparent hypotenuse face. On the first flat face of the cube-prism, a microspherical concave mirror is made with the center located on the optical axis of the interferometer. A method for calculating the defocusing of a controlled spherical mirror and the corresponding wave aberration of the working wavefront is presented. An example of calculating the design parameters of the interferometer and the permissible defocusing of the controlled spherical mirror is given

Near-field relaxation subsequent to the onset of oblique detonations with a two-step kinetic model

Initiation of an oblique detonation wave (ODW) results in a near-field region of curved detonation wave surface, which cannot be predicted by the detonation polar theory and lacks in-depth work on its features. In this study, Euler equations coupled with a two-step kinetic model are used to simulate ODW dynamics, and then the flow structures are analyzed by examining the asymptotic decay of local surface angle. The flow/reaction coupling is quantified by a non-dimensional Damköhler number Das that is defined as the ratio of the characteristic flow and chemical reaction length along streamlines. The results demonstrate a spectrum of local strong solutions forms, which always happens when the ODW transition pattern is abrupt, but the strong solutions deviate from the isolated strong solution predicted by the polar theory. Furthermore, the abrupt transition leads to a strong peak of Das, while the smooth one leads to a bump. Various simulated cases indicate that the transition pattern becomes abrupt and the local strong solution arises when the maximum Das reaches a critical range.

Active Shape Control of Membrane Structures Using Spin-Synchronous Vibrations

A novel approach for shape control of membrane structures is presented to realize their use in three-dimensional and variable configurations. The shape control is accomplished by exciting a spinning membrane. The membrane forms a shape consisting of several vibration modes, depending on the input frequency, and the wave surface stands still when its frequency is synchronized with the spin rate; that is, the wave propagation and the spin cancel each other, resulting in a static wave surface in the inertial frame. This idea enables control of continuous membrane structures with large deformation using fewer actuators than conventional methods. This paper describes the general theory of the static wave-based shape control. The mathematical model of membrane vibration, the classification of control input, and the control system for exciting a static wave are summarized. The proposed method is demonstrated through a ground experiment. A 1 m large polyimide film is rotated and vibrated in a vacuum chamber, and the output shape is measured using a real-time depth sensor. It is shown that the observed shapes agree with numerical simulation results. An additional simulation that models the Japanese solar sail Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS) demonstrates that the proposed method also works with a practically large-scale membrane in the space environment.

Seismological observations on the 2019 March 21 accidental explosion at Xiangshui chemical plant in Jiangsu, China

SUMMARY On 2019 March 21, an explosion accidentally occurred at a chemical plant in Xiangshui, Yancheng City, Jiangsu Province, China. Using broad-band digital seismic data from East China, South Korea and Japan, we investigate properties of the Xiangshui explosion as well as two nearby chemical explosions and four nearby natural earthquakes in Jiangsu Province, East China. From Lg and Rayleigh waves recorded by regional networks, both body wave magnitude mb (Lg) and surface wave magnitude Ms (Rayleigh) are calculated for these events. The magnitudes of the Xiangshui explosion are mb (Lg) = 3.39 ± 0.24 and Ms = 1.95 ± 0.27, respectively. Both the empirical magnitude–yield relation for buried explosion and empirical yield–crater dimension relation for open-pit explosion are adopted for investigating the explosive yield. The result from the yield–crater dimension relation is approximately 492 ton, which is consistent with the ground truth and considerably larger than that from the buried source model. This also reveals that, for Xiangshui explosion, the explosion to seismic energy conversion rate is approximately one-third compared to a similar sized fully confined explosion. By comparing the body wave and surface wave magnitudes from explosions and nearby earthquakes, we find that the mb:Ms discriminant calculated at regional distances cannot properly distinguish explosions from natural earthquakes. However, the P/S spectral ratios Pg/Lg, Pn/Lg and Pn/Sn from the same data set can be good discriminants for identifying explosions from earthquakes.

Numerical Modeling of the Wave Soldering Process and Experimental Validation

Abstract One of the most important procedures in the electronics industry is the assembly of electronic components onto printed circuit boards (PCBs) through the soldering process. Among the various soldering methods available, wave soldering is a very effective technique. In this process, the components are placed onto the PCB, which, subsequently, is coated with a flux and then passed across a preheat zone. In the end, the assembly is moved by the conveyor and passed over the surface of the molten solder wave in order to create a reliable connection both mechanically and electrically. Although this process has been frequently used, there are soldering defects that remain unsolved and continue to emerge, such as the missing of surface-mount components in the PCB after the soldering process. Aiming to understand if such defects are related to the force exerted by the solder wave in the PCB, a numerical and experimental study was performed in this article. For this purpose, a computational fluid dynamic model was developed by using the fluent software to describe the interaction between the solder jet and the PCB with the integrated circuits, and the multiphase method, volume of fluid, was also applied to track the solder–air interface boundary. The results obtained were numerically validated by using an experimental setup designed and built to this end. In general, the data obtained showed to be in good agreement and it was concluded that the force exerted by the solder wave is approximately 0.02 N.

Propagation of waves in an incompressible rotating transversely isotropic nonlocal elastic solid

In this paper, the nonlocal elasticity theory is applied to study the propagation of plane wave and Rayleigh-type surface wave in an incompressible, rotating and transversely isotropic material. The governing equations of motion for an incompressible, rotating, transversely isotropic and nonlocal elastic medium are specialized for a plane. The medium is assumed rotating about an axis perpendicular to the plane. The transverse isotropy axis is taken perpendicular to the surface. The specialized governing equations are first applied to derive a velocity equation for homogeneous plane wave. The specialized governing equations along with traction free boundary conditions are also applied to derive the secular equation governing the wave speed of Rayleigh wave. The speeds of plane wave and Rayleigh wave are computed and illustrated graphically to observe the effects of nonlocality, rotation, anisotropy, frequency and propagation direction. It is noticed from the theory and numerical results that the speeds of both plane wave and Rayleigh wave decrease sharply with an increase in nonlocal parameter or rotation parameter. The speeds of plane wave and Rayleigh wave increase logarithmically with anisotropy material parameter. The feasible ranges of nonlocality, rotation or anisotropy parameters for the existence of plane wave or Rayleigh surface wave are determined for a given wave speed when the values of other parameters are fixed.

Ultra‐Broadband Tunable Bragg–Berry Optical Vortex Generators of a Circularly Symmetric Chiroptic Structure

AbstractNew optical–photonic devices with the capability to manipulate, modify, and even tailor the light characteristics dynamically, such as wave surface, play an increasingly important role in the development of modern and future optics. Optical vortex with spiral wave surfaces is a special type of light with intrinsic orbital angular momentum (OAM). Thus, this vortex can be applied to the development of advanced optics, such as optical tweezers, ultra‐resolution microscope, optical communication, and quantum technology. This study demonstrates an optical device known as Bragg–Berry optical vortex generator (BBOVG) with a circularly symmetric chiral photonic structure using an easy‐to‐implement method by filling a ferroelectric liquid crystal‐doped cholesteric liquid crystal (FLC‐CLC) material into an indium‐tin‐oxide‐coated cell pre‐treated with photoalignment along the azimuthal direction. The BBOVG devices can be operated by dynamically tuning the photonic bandgaps of the opposite‐handed FLC‐CLCs throughout the full‐visible region (400–700 nm) in a low voltage range (≤ 3.0 V) to obtain reflective optical vortices with opposite OAM signs in a full‐visible range near room temperature. The present devices, which can transform geometric phase and have ultra‐wideband manipulability and high operability at room temperature, provide a good example in demonstrating key devices that fit the use in future optical/photonic applications.

SPiRaL: a multiresolution global tomography model of seismic wave speeds and radial anisotropy variations in the crust and mantle

SUMMARYSPiRaL is a joint global-scale model of wave speeds (P and S) and anisotropy (vertical transverse isotropy, VTI) variations in the crust and mantle. The model is comprised of >2.1 million nodes with five parameters at each node that capture velocity variations for P- and S-waves travelling at arbitrary directions in transversely isotropic media with a vertical symmetry axis (VTI). The crust (including ice, water, sediments and crystalline layers) is directly incorporated into the model. The default node spacing is approximately 2° in the lower mantle and 1° in the crust and upper mantle. The grid is refined with ∼0.25° minimum node spacing in highly sampled regions of the crust and upper mantle throughout North America and Eurasia. The data considered in the construction of SPiRaL includes millions of body wave traveltimes (crustal, regional and teleseismic phases with multiples) and surface wave (Rayleigh and Love) dispersion. A multiresolution inversion approach is employed to capture long-wavelength heterogeneities commonly depicted in global-scale tomography images as well as more localized details that are typically resolved in more focused regional-scale studies. Our previous work has demonstrated that such global-scale models with regional-scale detail can accurately predict both teleseismic and regional body wave traveltimes, which is necessary for more accurate location of small seismic events that may have limited signal at teleseismic distances. SPiRaL was constructed to predict traveltimes for event location and long-period waveform dispersion for seismic source inversion applications in regions without sufficiently tuned models. SPiRaL may also serve as a starting model for full-waveform inversion (FWI) with the goal of fitting waves with periods 10–50 s over multiple broad regions (thousands of kilometres) and potentially the globe. To gain insight to this possibility, we simulated waveforms for a small set of events using SPiRaL and independent waveform-based models for comparison. For the events tested, the performance of the traveltime-based SPiRaL model is shown to be generally on par with regional 3-D waveform-based models in three regions (western United States, Middle East, Korean Peninsula) suggesting SPiRaL may serve as a starting model for FWI over broad regions.

Solitary wave diffraction around a concentric porous cylindrical structure in front of a vertical wall

This paper investigates solitary wave diffraction around concentric porous cylindrical structure in front of a vertical wall, where the exterior cylinder is permeable and the interior cylinder is impermeable. This problem is transformed into an issue of bi-directional incident waves diffraction around two concentric cylindrical systems based on the image theory. An analytical solution of the problem is obtained by applying the eigenfunction expansion approach and Graf's addition theorem. Unlike previous studies using Airy wave, this paper uses solitary wave as incident wave. The hydrodynamic loads and wave elevations on the concentric cylindrical system are calculated and compared with existing work. An excellent agreement is obtained between the model and data. Parametric studies on porosity, annular spacing, incident wave angle, distance between the concentric structure and wall were also explored. The results indicated that wave loads on the exterior cylinder near a vertical wall could reach twice as large as the force on it in open water, while the magnitudes of wave loads on the interior cylinder are similar for the two cases. In addition, we compared the modelling results of wave surface elevations using solitary wave and Airy waves. It shows that the amplitude of the wave surface elevations caused by the solitary wave is significantly higher than that of the Airy wave, which means the wave effects on offshore structures will be underestimated when using the Airy wave model in the same shallow water conditions.

Surface Acoustic Wave Biosensor with Laser-Deposited Gold Layer Having Controlled Porosity

Laser-deposited gold immobilization layers having different porosities were incorporated into love wave surface acoustic wave sensors (LW-SAWs). Variation of pulsed laser deposition parameters allows good control of the gold film morphology. Biosensors with various gold film porosities were tested using the biotin–avidin reaction. Control of the Au layer morphology is important since the biotin and avidin layer morphologies closely follow that of the gold. The response of the sensors to biotin/avidin, which is a good indicator of biosensor performance, is improved when the gold layer has increased porosity. Given the sizes of the proteins, the laser-deposited porous gold interfaces have optimal pore dimensions to ensure protein stability.

Numerical Simulation of Solitary Wave Forces on A Vertical Cylinder on A Slope Beach

Wave forces acting on a vertical cylinder at different locations on a slope beach in the near-shore region are investigated considering solitary waves as incoming waves. Based on the Reynolds-averaged Navier-Stokes equations and the k-ε turbulence model, wave forces due to the interaction between the solitary wave and cylinder are simulated and analyzed with different incident wave heights and cylinder locations. The numerical results are first compared with previous theoretical and experimental results to validate the model accuracy. Then, the wave forces and characteristics around the cylinder are studied, including the velocity field, wave surface elevation and pressure. The effects of relative wave height, Keulegan-Carpenter (KC) number and cylinder locations on the wave forces are also discussed. The results show that the wave forces exerted on a cylinder exponentially increase with the increasing incident wave height and KC number. Before the wave force peaks, the growth rate of the wave force shows an increasing trend as the cylinder moves onshore. The cylinder location has a notable effect on the wave force on the cylinder in the near-shore region. As the cylinder moves onshore, the wave force on the cylinder initially increases and then decreases. For the cases considered here, the maximum wave force appears when the cylinder is located one cylinder diameter below the still-water shoreline. Furthermore, the fluid velocity peaks when the maximum wave force appears at the same location.

Pierson-Moscowitz spectrum simulation based on the rough sea surface

By analyzing a variety of traditional wave spectrum models, combining the actual wavelength and wave surface displacement to compare the electromagnetic field propagation process, the P-M (Pierson-Moscowitz) spectrum is used to theoretically derive the electrical characteristics of the rough sea surface and its influence on the propagation process of high-frequency electromagnetic waves. Based on the bilinear superposition algorithm and Matlab numerical calculation software, the electrical characteristics of rough seas and the theoretical results of electromagnetic wave propagation in rough seas are simulated and verified. The results show that the modeling of rough sea surface based on P-M spectrum has the advantages of high reducibility and stable frequency spectrum.

Towards a more “scale‐aware” orographic gravity wave drag parametrization: Description and initial testing

AbstractMany current orographic gravity wave drag parametrizations employed in numerical weather prediction and climate models assume idealised elliptical subgrid orography. As a result, they do not fully capture the spectrum of subgrid orographic scales and do not exhibit the desired behaviour when the model grid length is varied. This article describes the motivation, formulation, and testing of a new orographic gravity wave drag parametrization in the Met Office Unified Model that is more “scale‐aware”. The scheme circumvents the need to make assumptions about the shape and distribution of the subgrid orography, moving away from elliptical mountains, through the use of Fourier transforms. The reduction in gravity wave surface stress when orographic flow blocking is present is also accounted for. The result is a new scheme that represents subgrid mountain scales more faithfully and consistently, rather than assuming a single mountain scale for each grid box. Tests using both regional and global simulations, ranging in grid spacing from 2–130 km, demonstrate that the scale‐aware scheme provides a more constant total, resolved plus parametrized, orographic gravity wave momentum flux, when the grid length is varied over most regions of the globe. Global five‐day forecasts also show a significant reduction in the too‐strong zonal wind bias within the Northern and Southern Hemisphere upper troposphere to lower stratosphere at grid spacings of 130 and 40 km when the scale‐aware scheme is employed. Some discussion on future developments for the scheme is also presented, noting that improvements to the orographic flow‐blocking drag component are required before the scheme can be implemented operationally.

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ НЕУСТОЙЧИВЫХ РЕЖИМОВ ТЕЧЕНИЯ НЕИЗОТЕРМИЧЕСКОЙ ЖИДКОЙ ПЛЕНКИ

The paper presents the results of numerical simulation of the flow of a thin liquid layer with a free surface. The simulation was performed at moderate Reynolds numbers within the framework of the partial differential equation for the state of the free surface of the film. Equation coefficients include various physicochemical factors, namely surface tension, and temperature gradients. Computational experiments are carried out for a thin layer of a viscous liquid. The modes of free runoff, evaporation and counter flow are investigated. The values of the wave characteristics are found. The flows of a liquid film with the maximum value of the growth rate are identified. Such modes have been recorded in experimental studies by other scientists. The results of modeling the wave surface of a liquid film in Python are presented. The results can be used in the design or modernization of existing equipment, as well as in the development of technological processes in liquid films.

Wave dispersion and quantitative accuracy analysis of bond-based peridynamic models with different attenuation functions

Peridynamics (PD) reformulates classical continuum mechanics in terms of spatial integral equations rather than partial differential equations. PD has successfully matched fracture patterns observed in experiments. However, issues remain, such as its dispersion characteristics, constant micromodules, and behavior at material boundaries. The introduction of attenuation functions can effectively address these three problems. In this study, we attempted to conduct a systematic investigation of bond-based peridynamics (BPD) with different attenuation functions. This mainly involved an analysis of the wave dispersion, surface effect, and quantitative accuracy of BPD models with different attenuation functions. Initially, a novel quartic polynomial attenuation function was proposed, and various types of functions were investigated. The corresponding expressions for non-constant micromodulus functions were determined, and attenuation bond-based peridynamic (ABPD) models that considered the effect of attenuation were established. Furthermore, the dispersion relationship of ABPD for the one-dimensional case was derived, and the effects of the horizon size, material point size, and attenuation functions on the dispersion properties were investigated. Finally, the surface effect and the effectiveness of different attenuation functions were examined by considering the attenuation functions and energy correction method in ABPD models under plane stress and plane strain conditions. Thus, the accuracy of ABPD was evaluated. The influence function proposed in this work and other several attenuation functions can be used to minimize wave dispersion for a fixed material point size or horizon size and to reduce the surface effect. The energy correction method had a remarkable influence on the computational accuracies of the classical BPD model and ABPD models. Practical recommendations for selecting the attenuation functions for coupling PD with other methods and for enhancing the accuracy of the BPD model were provided.

Engineering the penetration depth of nearly guided wave surface plasmon resonance towards application in bacterial cells monitoring

Photonic techniques based on evanescent waves sensing (such as the surface plasmon resonance (SPR) method) using plasmonic and nanostructured metallic/semiconductor materials hold huge potential in biosensing and associated analysis of biomolecular interactions. However, conventional SPR suffers from low penetration depths (<300 nm), limiting the applications for the surface interactions and analysis of larger biomolecules, such as for bacteria cells with a typical size of ∼1 μm. These cases result in the measured signal being non-monotonic with concentration, making the technique unreliable for high concentrations. Infrared wavelengths can be used, but then signal contrast suffers, and the instruments required for mid-infrared or longer wavelengths are prohibitively expensive. With this in mind, we developed a “nearly” guided SPR (NGWSPR) structure to enhance the performance of these sensors by increasing penetration depth and figure of merit using wavelengths in the optical telecommunication window where off-the-shelf instruments are available at low cost. The use of this technique for monotonic detection of cultured live Escherichia coli bacterial cells is demonstrated, thus opening a pathway to utilize and promote the approach for biosensing, biomedical research and industrial applications.

Abundant Traveling Wave and Numerical Solutions of Weakly Dispersive Long Waves Model

In this article, plenty of wave solutions of the (2 + 1)-dimensional Kadomtsev–Petviashvili–Benjamin–Bona–Mahony ((2 + 1)-D KP-BBM) model are constructed by employing two recent analytical schemes (a modified direct algebraic (MDA) method and modified Kudryashov (MK) method). From the point of view of group theory, the proposed analytical methods in our article are based on symmetry, and effectively solve those problems which actually possess explicit or implicit symmetry. This model is a vital model in shallow water phenomena where it demonstrates the wave surface propagating in both directions. The obtained analytical solutions are explained by plotting them through 3D, 2D, and contour sketches. These solutions’ accuracy is also tested by calculating the absolute error between them and evaluated numerical results by the Adomian decomposition (AD) method and variational iteration (VI) method. The considered numerical schemes were applied based on constructed initial and boundary conditions through the obtained analytical solutions via the MDA, and MK methods which show the synchronization between computational and numerical obtained solutions. This coincidence between the obtained solutions is explained through two-dimensional and distribution plots. The applied methods’ symmetry is shown through comparing their obtained results and showing the matching between both obtained solutions (analytical and numerical).

Numerical investigation of local scour around submerged pipeline in shoaling conditions

A two-dimensional numerical model is employed to predict local scour around submarine pipelines under water waves in shoaling condition. The motion of water under waves is simulated by solving the Reynolds Averaged Navier-Stokes (RANS) equations. The wave surface is traced by the Arbitrary Lagrangian-Eulerian (ALE) method. The evolution of the seabed surface near the pipeline is predicted by solving the conservation of the sediment mass, which transport in the water in the forms of bed load and suspended load. The main aim of this study is to investigate the effect of the seabed slope on the scour profiles and scour depth. To achieve this aim, numerical simulations of scour around a pipeline on a flat seabed and on a slope seabed with a slope angle of 5°, 10° and 15° are conducted for various wave conditions. The numerical results show that present numerical results of equilibrium scour depth below pipeline agree the values calculated by the suggested formula quite well for β = 0° where β is the slope angle. As β≠0°, the equilibrium scour depth agrees with the empirical formula as KC < 8 and is greater than the latter for KC > 8.

Predicting Lake Erie wave heights and periods using XGBoost and LSTM

Waves in large lakes put coastal communities and vessels under threat, and accurate wave predictions are needed for early warnings. While physics-based numerical wave models such as WAVEWATCH III (WW3) are useful to provide spatial information to supplement in situ observations, they require intensive computational resources. An attractive alternative is machine learning (ML) methods, which can potentially improve the performance of numerical wave models, while only requiring a small fraction of the computational cost. In this study, we applied novel ML methods based on XGBoost and a Long Short-Term Memory (LSTM) recurrent neural network for predicting wave height and period under the near-idealized wave growth conditions of Lake Erie. Data sets of significant wave height (H), peak wave period (Tp) and surface wind from two offshore buoys from 1994 to 2017 were processed for model training and testing. We trained and validated the ML models with the data sets from 1994 to 2015, and then used the trained models to predict significant wave height and peak period for 2016 and 2017. The XGBoost model yielded the best overall performance, with Mean Absolute Percentage Error (MAPE) values of 15.6%–22.9% in H and 8.3%–13.4% in Tp. The LSTM model yielded MAPE values of 23.4%–30.8% in H and 9.1%–13.6% in Tp. An unstructured grid WW3 applied to Lake Erie yielded MAPE values of 15.3%–21.0% in H and 12.5%–19.3% in Tp. However, WW3 underestimated H and Tp during strong wind events, with relative biases of -11.76% to -14.15% in H and -15.59% to -19.68% in Tp. XGBoost and LSTM improve on these predictions with relative biases of -2.56% to -10.61% in H and -8.08% to -10.13% in Tp. An ensemble mean of these three models yielded lower scatter scores than the members, with MAPE values of 13.3%–17.3% in H and 8.0%–13.0% in Tp, although it did not improve the bias. The ML models ran significantly faster than WW3: For this 2-year run on the same computing environment, WW3 needed 24 h with 60 CPUs, whereas the trained LSTM needed 0.24 s on 1 CPU, and the trained XGBoost needed only 0.03 s on 1 CPU.

A numerical and theoretical study of wind over fast-propagating water waves

Effects of fast-propagating water waves on the overlying wind are investigated using simulation and theoretical analysis. By performing a large eddy simulation (LES) of turbulent wind over water waves with high wave age, we observe that the perturbation to wind velocity and pressure by the waves, or the wave-induced airflow, is mainly induced by the vertical movement of the wave surface. We perform scaling analysis to show that the turbulent stress effects on fast wave-induced airflow are negligible. Moreover, we find that the curvilinear model developed for opposing wave effects on wind by Caoet al.(J. Fluid Mech., vol. 901, 2020, p. A27) provides predictions that agree well with the present LES results of wind following fast waves. Our analyses of the results indicate that the fast wave-induced airflow is a quasilinear process. To elucidate the mechanisms for fast wave effects, we split the curvilinear model into two equations corresponding to wave kinematics and forcing by wave elevation, respectively. Using these equations, we illustrate that the vertical component of wave orbital velocity induces a strong airflow perturbation, which produces the dominant components of fast wave-induced airflow and determines its overall spatial structure. Furthermore, we discover that the weak components of fast wave-induced airflow are forced by the dominant components via viscous stress and by the forcing induced by wave elevation, and generate the form drag on the wave surface.