Wave Surface Research Articles

A Computation Method for the Typhoon Waves Using the Field Wave Spectrum

Wave features and propagation characteristics during typhoons are the key factors to study the dynamic response of ocean engineering and coastal disaster prevention and mitigation under extreme climate. Based on the Longuet-Higgins theory, the method of the field spectrum during the typhoon was used to compute the typhoon waves. And the directional spectrum, the formulas of wave surface, the velocity of water particles, and the acceleration of water particles were investigated. The results showed that the interpolated field wave spectrum combined with the SWOP direction spectrum could accurately simulate the three-dimensional typhoon waves. The significant wave height and the average period of the simulated wave surface at fixed point were statistically evaluated by the upward zero-crossing method, and the relative errors were ± 5% and ± 15%, respectively. The typhoon wave surface computed by a dual peak spectrum had small periodic waves, and the velocity and acceleration of water particles differed considerably from the JONSWAP spectrum. Finally, a fastened slender cylinder was simulated under action of the typhoon waves, which proved the applicability of the computation method. This study aims at providing a basis for the simulation of the dynamic response of marine structures under the typhoon waves action.

Highly porous Fe2O3-SiO2 layer for acoustic wave based H2S sensing: mass loading or elastic loading effects?

A highly porous Fe2O3-SiO2 layer prepared using sol-gel and spin-coating methods was applied on the surface of a surface acoustic wave (SAW) device for H2S sensing. SiO2 in this sensing layer serves as a porous support for dispersing Fe2O3 nanoparticles, and Fe2O3 nanoparticles can effectively adsorb and react with H2S molecules. By changing the Fe/Si molar ratio in this Fe2O3-SiO2 layer, its pore volume, pore distribution and H2S adsorption capacity can be adjusted, the contribution of mass loading effect and the elastic loading effect toward the frequency response of the sensor can be controlled, and the sensing performance of the sensor can be optimized. The optimized sensing response is − 4.4 kHz toward 100 ppm H2S, with a good selectivity and reproducibility operated at room temperature (25 ℃).

Numerical investigation on movement of triple points on oblique detonation surfaces

A normal detonation wave in a gaseous mixture is a transient, multidimensional structure containing triple points (TPs) that collide in pairs and then propagate oppositely. However, the TPs on an oblique detonation wave (ODW) almost propagate along the same direction in most studies. In this study, the reactive Euler equations coupled with a two-step induction–reaction kinetic model are used to solve a two-dimensional wedge-induced ODW. Two novel movement patterns are observed in most cases. Results show that the TPs of the ODW can propagate upstream and even stand on the wave surface. The movement patterns of TPs include downstream, upstream, and steady according to their propagation direction relative to the wedge. We find that the ratio of the post-ODW flow speed Uτ to the transverse wave speed UT dominates the TP movement types. When the speed ratio Uτ/UT is approximately equal to 1, the TPs can stand on the wave surface. Above unity, downstream TPs form, and upstream TPs correspond to a value smaller than 1. Furthermore, the inflow Mach number has little influence on UT, while Uτ changes significantly. This is largely due to the high sensitivity of the ODW angle to the inflow. The high heat release rate benefits upstream TPs, and steady TPs form under a large wedge angle. The results are confirmed by varying the inflow Mach number, wedge angle, and chemical parameters.

ANALYSIS OF THE ERRORS OF DETERMINING THE EQUIVALENT SIZE AND ORIENTATION OF A PLANE DEFECT UNDER MANUAL ULTRASONIC CONTROL

The article reviews and analyzes the method of defect identification for determining the angle of inclination of a planar point defect to the input surface of an ultrasonic wave and its equivalent size during manual ultrasonic testing by the echo-pulse method. The method is most widely used in ultrasonic control of parts obtained by plastic deformation (forging, hot and cold stamping, rolling). This is due to the fact that defects in such parts are predominantly planar in nature. The method of ultrasonic defect identification is based on the use of a combined transducer P131-2.5-0i18-VO-04 containing two piezoelectric transducers in one housing with a normal input of a longitudinal ultrasonic wave and an input angle of 18º. The article presents a mathematical apparatus for the implementation of this method. Also presented is a software product that allows you to automate calculations when using this method of defect identification. The article carried out experimental studies of this method of ultrasonic defect identification, which showed its low error and high efficiency. The average value of the relative error in determining the angle of inclination of a planar point defect to the input surface of an ultrasonic wave was 1.525 %. The average value of the relative error in determining the equivalent size of a planar point defect located at an angle to the ultrasonic wave input surface was 1.192 %.

Multiple rogue wave solutions of a generalized (3+1)-dimensional variable-coefficient Kadomtsev--Petviashvili equation

Abstract Kadomtsev–Petviashvili equation is used for describing the long water wave and small amplitude surface wave with weak nonlinearity, weak dispersion, and weak perturbation in fluid mechanics. Based on the modified symbolic computation approach, the multiple rogue wave solutions of a generalized (3+1)-dimensional variable-coefficient Kadomtsev–Petviashvili equation are investigated. When the variable coefficient selects different functions, the dynamic properties of the derived solutions are displayed and analyzed by different three-dimensional graphics and contour graphics.

Thermal Modeling of Ultrasound Diathermy in Tissues with a Circular Inclusion near a Curved Interface

The influences of implants on the temperature field in tissues during ultrasound diathermy is controversial. In addition, most previous studies have focused on plate implants, and the effects of irregular implants and bones are seldom discussed. In this study, a hybrid computational framework per se is proposed to investigate the effects of double circular inclusions on the temperature distribution during ultrasound diathermy. The tissue–inclusion–bone structure is simplified as a two-dimensional bilayer composite model consisting of soft tissue and bone with a circular inclusion imbedded in the soft tissue. The interface between the bone layer and the soft-tissue layer is assumed as a convex surface for the incident ultrasonic waves. Multiply scattered waves originate between the two acoustic scatterers, i.e., the circular inclusion and the convex bone. The proposed computational framework consists of two kernels tackling ultrasound propagation and heat conduction problems, respectively. Making use of theoretical solutions of pressure fields, the transformed heat sources are efficiently obtained in the first kernel without sacrificing much computational burden. Temperature distributions in the composite media under ultrasound diathermy are evaluated via finite element numerical simulations in the second kernel. Numerical results indicate that the temperature distributions in the composite system obviously change when the bone layer changes from flat to convex. In addition, the inclusion size, location, material, and ultrasound operation frequency will also affect the temperature distribution and peak temperature during ultrasound diathermy. Pertinent findings could serve as a guide for clinical innovations in therapeutic ultrasounds.

Experimental investigations of secondary load cycle formation in wave force on a circular cylinder under steep regular waves

When a large wave interacts with a marine structure, it would lead to a high-frequency structure response, and impose great threats to marine structures. In this paper, wave forces on a vertical cylinder in regular waves with moderate to extreme steepness were measured experimentally. The secondary load cycle phenomenon in wave force time history was observed and its generation mechanism was analyzed. It is found that secondary load cycle strongly depends on wave steepness. When the wave steepness exceeds critical values, the secondary load cycle phenomenon appears in the time history of wave force, and a high frequency response accompanied this phenomenon. Further, a new critical wave steepness kA = 0.3tanh(kh) (A is wave crest height, k is wavenumber and h is water depth) is found to distinguish the secondary load cycle occurrence. Here the wave steepness threshold value is no more a constant value that was proposed before, it varies with water depth and becomes smaller with the decrease of water depth. Moreover, the secondary load cycle and the subsequent high-frequency response are divided from the wave force signal based on the empirical mode decomposition (EMD) method. The results show that the high-frequency response locates in the natural frequency region of cylinders, which is much higher than the high-order wave components. Finally, the generation mechanism of this phenomenon is explained. As a steep wave passes a cylinder, a large wave run-up would be generated on the front side of the cylinder. One part of water body of the run-up swashes down and impacts the wave surface heavily. The other part of wave run-up fills into the cavity on the lee side of the cylinder, and generates violent turbulence. Both processes are found to lead to an instant impact on the structure, and then excite structural high-frequency vibration. This instant impact expresses as secondary load cycle in wave force history. These new findings from experimental studies have provided new insights into the generation mechanism and the associated changes in wave properties during the formation of secondary load cycle.

Numerical simulation of interaction between wave-driven currents and revetment on coral reefs

The stability of a revetment breakwater is vital for the safety of islands and reefs formed with reclaimed sand under the action of a complex marine environment. The interactions in wave-reef-revetment systems are complex and difficult to accurately simulate; in addition, it is difficult to describe the dynamic wave pressures distribution by empirical formula, although these parameters are important for the safety of reefs and revetments; hence, more studies are required. In this study, an investigation of the interaction between the wave-driven current on the reef flat and rear revetment breakwater is performed, and the hydrodynamic pressure on the revetment is discussed. A two-dimensional numerical model is established using the Navier–Stokes equation to explore the interaction and calculate the pressure distribution on the revetment, which is verified by an experiment designed and implemented in a wave flume. The simulation illustrates that the wave-driven current is stratified in the vertical direction, and the velocity at the surface is approximately 2–3 times that of the average value, and the maximum flow velocity can reach 13 m/s. By varying the parameters of the geomorphology of the coral reef, the results suggest that for steeper fore-reef slopes, longer reef flats, and larger relative distances, the peak value of the pressure increases consistently. The detailed and sophisticated hydrodynamic pressure distribution on the revetment is obtained, and the numerical results indicate that the fifth-order polynomial can match the regulation of pulsating pressure at the wave surface with the relative submerged water depth.

Two-Phase Smoothed Particle Hydrodynamics Modelling of Hydrodynamic-Aerodynamic and Wave-Structure Interaction

A two-phase (air and water) smoothed particle hydrodynamics (SPH) method is employed to study the hydrodynamic-aerodynamic and wave interaction with fixed and floating structures in a wave basin. The method is first verified for a classical two-phase dam-breaking. A mirror-open boundary is implemented at the top and left sides of a two-phase wave basin with a piston to generate a second-order regular wave. It is observed that, compared to the single-phase simulation, the two-phase one obtains a smoother water surface and prevents the non-physical water splash when interacting with the sloped dissipative beach. This wave basin is also used to investigate wave-structure problems such as wave interaction with a rigid cantilever beam fixed to the basin bottom and downstream of the wave-maker mechanism and the dynamics of a single floating box and two floating boxes in the waves. A typical wave-structure interaction period is captured and described using pressure contours and velocity vectors at three selected instants for the wave-rigid cantilever beam case. With the increase of the structure’s height, the wave height after the structure decreases, but no evident variation is found when changing its thickness. Besides the hydrodynamics interaction, a periodical collision is observed between the two floating boxes on the wave surface.

Diversity of wave structures to the conformable fractional dynamical model

This manuscript examines the recently developed conformable three-dimensional Wazwaz–Benjamin–Bona–Mahony (3D-WBBM) equation’s dynamical behavior in terms of its spatial and temporal variables. The governing equation is stretch for the Korteweg-de-Vries equation that represents the unidirectional propagation of small amplitude long waves on the surface of hydro magnetic and acoustic waves in a channel, especially for shallow water. Solitary wave solutions of various types, such as kink and shock, as well as singleton, combined solitons, and complex solitons, are all retrieved. Additionally, solutions to hyperbolic, exponential, and trigonometric functions are obtained through the use of recently developed methods, namely the Kudryashov method (KM), the modified Kudryashov method (MKM), and the new extended direct algebraic method (NEDAM). The study conducts a comparison of our findings to well-known findings, and concludes that the solutions reached here are novel. Additionally, the earned results are sketched in different shapes to demonstrate their dynamics as a function of parameter selection. We can assert from the obtained results that the applied techniques are simple, vibrant, and quite well, and will be helpful tool for addressing more highly nonlinear issues in various of fields, especially in ocean and coastal engineering. Furthermore, our findings are first step toward understanding the structure and physical behavior of complicated structures. We anticipate that our results will be highly valuable in better understanding the waves that occur in the ocean. We feel that this work is timely and will be of interest to a wide spectrum of experts working on ocean engineering models.

A rapid imaging method of the seismic back‐scattered wavefield for urban road near‐surface anomalous structures

ABSTRACTUrban road near‐surface anomalous structures are buried at shallow depths (≦20 m) and small scale. Current geophysical methods, such as the transient electromagnetic, ground‐penetrating radar and shallow seismic methods with reflection wave, refraction wave and Rayleigh surface wave, do not provide sufficient detection accuracy for near‐surface anomalous structures. Although the back‐scattered method is promising in this task, it still needs improvement. This paper proposes an efficient near‐surface seismic back‐scattered method to realize the rapid lateral imaging of urban road anomalous structures. The proposed method uses a principal component analysis algorithm to directly extract the anomalous structure information. It does not require the knowledge of parameters such as velocity or the seismic wavelet so that the solutions are not affected by these parameters. Moreover, the proposed method retains the high transverse resolution of the back‐scattered wavefield and does not lose the wavefield information. Simulation and experimental operation show that the proposed method is very efficient. Combined with the hardware equipment provided by the towed seismograph, the proposed method can realize rapid detection and data imaging, which has a high engineering application value.

Different approaches to numerical modeling of sea waves

The main approaches in direct modeling of surface waves based on complete equations of dynamics of the inviscid liquid with a free surface are briefly considered. Most of the models are intended for study of the applied and engineering problems. It is assumed that the main model is written in the curvilinear coordinate system where the height is counted off from wave surface. In the two-dimensional periodic formulation, when using a conformal system, the problem is reduced to the system of one-dimensional equations that can be easily solved using Fourier-transform method. For three-dimensional waves such simplifications do not exist, thus, the vertical velocity on the surface is calculated by solving a three-dimensional Poisson equation or using a surface integral method. An approximate scheme based on the two-dimensional equations is considered. The scheme allows reproducing the statistical mode of waves with high accuracy consistent with the similar results obtained from the accurate three-dimensional model.

Coupling characteristics of bubbles with a free surface initially disturbed by water waves

The interactions between bubbles and water waves have important applications in ocean engineering, and their coupling characteristics are strongly associated with the wave phase angle, wavelength, and wave amplitude. Based on the assumption that the liquid is inviscid and incompressible, the coupling characteristics between bubbles and water waves are solved by the Euler equations with the finite volume method, and the bubble surface and water wave surface are tracked by the front tracking method. The accuracy of the numerical method is verified by comparison with a spark-generated bubble experiment. Compared with the bubble near the initially plane free surface, the rising height of the water spike is reduced by water waves in the crest state, where a concave shape forms on the falling water wave during bubble contraction when the wavelength λ≤ 4.00 and the wave amplitude h≥ 0.364. The rising height of the water spike is significantly strengthened by water waves in the trough state with smaller wavelengths and larger wave amplitudes, which produce a thinner and higher water spike. The bubble cycle is shortened by water waves in the crest state with smaller wavelengths and prolonged by water waves in the trough state with smaller wavelengths and larger wave amplitudes. The results presented in this paper provide guidance for the study of underwater explosions in complex water wave environments.

Numerical Simulation of Micro-Bubbles Dispersion by Surface Waves

This paper presents an algorithm for numerical modeling of bubble dispersion occurring in the near-surface layer of the upper ocean under the action of non-breaking two-dimensional (2D) surface waves. The algorithm is based on a Eulerian-Lagrangian approach where full, 3D Navier-Stokes equations for the carrier flow induced by a waved water surface are solved in a Eulerian frame, and the trajectories of individual bubbles are simultaneously tracked in a Lagrangian frame, taking into account the impact of the bubbles on the carrier flow. The bubbles diameters are considered in the range from 200 to 400 microns (thus, micro-bubbles), and the effects related to the bubbles deformation and dissolution in water are neglected. The algorithm allows evaluation of the instantaneous as well as statistically stationary, phase-averaged profiles of the carrier-flow turbulence, bubble concentration (void fraction) and void-fraction fluxes for different flow regimes, both with and without wind-induced surface drift. The simulations results show that bubbles are capable of enhancing the carrier-flow turbulence, as compared to the bubble-free flow, and that the vertical water velocity fluctuations are mostly augmented, and increasingly so by larger bubbles. The results also show that the bubbles dynamics are governed by buoyancy, the surrounding fluid acceleration force and the drag force whereas the impact of the lift force remains negligible.

Numerical study of wave effect on water entry of a three-dimensional symmetric wedge

Marine and aerospace structures are frequently subject to impact loads on wave surface. The primary aim of this paper is to obtain a fundamental understanding of wave effect on wedge entry problem. A three-dimensional (3D) full-scale symmetric wedge with three degrees of freedom (3DOF) is numerically modeled in the incompressible air–water two phase flows. The numerical implementation and regular wave surface are realized in Reynolds-averaged Navier–Stokes equations (RANS) framework (STAR-CCM+ 2020.1) by combining with volume of fluid (VOF) and velocity-inlet wavemaking methods. The accuracy of the present numerical model is validated by the experimental tests. Various case studies are then carried out to investigate the difference between calm water and wave crest entries, and to analyze the mechanisms of the wave position and wave height effects through several physical results, including acceleration, velocity, pressure, displacement, rotation and free surface. Results indicate that the process of water entry can be divided into early, vertical-down and bounce-up stages. Further, the wave effect on the water entry problem can be explained as that the incident wave particle velocities and the surface slope result in the variations of effective impacting velocity and entry type of the wedge, and thus remarkably influence the hydrodynamic loads and rotating motion of the wedge. The parametric study reveals that the wave height has no significant effect on the vertical force but positively affects the horizontal impact force and rotating motion of the wedge.

Computational Study on Rogue Wave and Its Application to a Floating Body

A rogue wave is a huge wave that is generated by wave energy focusing. Rogue waves can cause critical damage to ships and offshore platforms due to their great wave energy and unpredictability. In this paper, to generate a rogue wave, a bull’s-eye wave, which is a focusing of multi-directional waves, was simulated in a numerical wave tank. A multi-directional wave generating boundary was developed using OpenFOAM, which is an open-source computational fluid dynamics (CFD) library. The wave height and profile of the generated rogue wave were compared to those of the regular wave. In addition, the pressure and velocity contours of water particles and velocity vectors at the free surface of the rogue wave were studied, along with the kinematic and dynamic effects of the rogue wave on a floating body.

Nonlinear characterization of stress wave factor for plastic damage of A7N01P-T4 aluminum alloys

This paper studies the relationship between plastic damage and the ultrasonic nonlinear coefficient by changing the interior plastic strain of A7N01P-T4 aluminum alloys. An effective evaluation of the plastic damage of tensile test specimens was made by comparing with two different nonlinear ultrasonic detection methods, namely, nonlinear longitudinal wave method and surface wave method. The nonlinear coefficient of the stress wave factor was introduced to characterize the plastic damage for metallic materials. The results showed that with the increasing plastic damage degree, the nonlinear coefficient increased slowly at the early stage of yield hardening (3%) and then increased rapidly at the middle stage (3–5%). It is concluded that the nonlinear longitudinal wave is more suitable for point measurement and its sensitivity is lower than that of the longitudinal wave.

Numerical Study of Wave Effect on Aircraft Water-Landing Performance

Aircraft, such as amphibious planes, airliners, helicopters and re-entry capsules, are frequently subject to impacting loads from water-landing/ditching on various free surfaces, especially under wave conditions. Understanding and quantifying the water-landing/ditching performance on wave surfaces are of fundamental important for the design and certification of crashworthiness in the field of aerospace engineering. This study aims to numerically assess the effect of wave surface on water-landing process of an amphibious aircraft. The numerical implementation is realized in Reynolds-averaged Navier–Stokes (RANS) framework by combining finite volume method (FVM), volume of fluid (VOF) approach and velocity-inlet wavemaker. The temporal-spatial characteristic of numerical wave and the accuracy of presented model are, respectively, validated by analytical wave and convergence studies. The aircraft landing simulations with different free surface conditions, i.e., calm water, regular wave with different wave heights are then performed and quantitatively compared through several physical parameters, including acceleration, velocity, pressure, pitch angle and free surface deformation. It was found that the aircraft regular wave-landing process experiences several unique stages comparing with the calm-water-landing case. The results clearly confirm that wave surface can influence the aircraft landing performance to a great extent. The fundamental mechanism is found to be that the wave surface slope and wave particle velocity remarkably change the impacting position and effective impacting velocity of the aircraft.

Effect of directional spreading angles on the wave hydrodynamic coefficients for vertical cylinder

In the prediction of accurate wave force, the consideration of short-crested wave is important in representing the actual ocean condition. Owing that, nonlinear wave characteristics are expected to change the flow properties when the wave passes the structures, which showing these characteristics are crucial to be accounted. However, literature reported that the overestimation on the design of marine structures has shown a lower reliability in the wave force prediction considering long-crested wave. Further in detail, the effect of wave directionality and directional spreading angle from the actual sea conditions, i.e. the short-crested waves, have been neglected in a way. To prove the validity of this statement, an experimental investigation was conducted to quantify the effects of wave directionality on the wave forces and to propose the hydrodynamic coefficients incorporated the effect of directional spreading angles. The wave directionality in term of directional spreading angles were considered, ranging from 5 to 45°. Then, the measured wave surface elevation and wave forces were processed using least square method to compute the hydrodynamic coefficients and to evaluate the wave forces. To quantify the effect, force ratio factor was adopted. Based on the finding, short-crested waves led to 20 % force reduction as compared to the long-crested. On top of that, a reduction of 1.12 % of wave force has also been observed for every one-degree incremental of the directional spreading angle. As conclusion, the wave directionality was found contributing to the reduction of wave force which may provide new improvement on the accuracy of wave force formulation for the design of lean marine structures.

Distinct Wing-in-Ground Effect of Airfoil in Proximity to Water Waves

The present study numerically explores the distinct aerodynamic characteristics of an airfoil flying in proximity to water waves. The water wave is treated by both two-phase-flow wavy water and rigid moving wavy ground, with a specific goal to clarify whether the water wave can be substituted by rigid wavy ground. Results show that for large ground clearance (), the aerodynamic forces and flow structures of the near-field airfoil are basically dominated by the passage shape between airfoil and wave surface where the wavy water can be replaced by means of using wavy ground. However, it is different for small ground clearance that the airfoil-induced airflow has a strong relative speed to the water flow and subsequently creates a strong shear force on the forthcoming wave to eject water spray from wave crest. The spray has a sufficient influence on the flow topology and consequently leads to a distinct aerodynamic behavior. Particularly, the strong upstream shear on the wave resulted from the stagnation region at a positive angle of attack induces upwind spray, which can be elevated to hit onto the airfoil with larger density and momentum than airflow causing extraordinarily high pressure on the lower surface as well as unstable aerodynamic forces.