Water Wave Impact Research Articles

Water wave diodes

Seaports are crucial components of maritime transportation systems. However, the presence of water waves significantly affects the speed and stability of vessels passing through ports, reducing the port efficiency. Traditional methods of blocking waves are not feasible since they also impede vessel passage. Therefore, finding a solution that effectively mitigates water wave impact while allowing unhindered vessel passage is of paramount importance in maritime transportation. In this article, we introduce a gradient refractive index profile into water wave manipulation and design a novel waveguide isolator device. It functions similarly to an electrical diode, allowing water waves to pass in one direction while blocking them in the opposite direction. Moreover, its waveguide-like hollow structure enables it to block water waves without hindering the passage of vessels. We elucidate the wave-blocking mechanism through mode analysis and numerical simulations, and experimentally validated the device, observing a significant “water wave diode effect.” This effect effectively blocks water waves in one direction while allowing passage in the other. This is the first time that blocking water waves without hindering vessel passage has been realized in the experiment, showing great potential for applications in maritime ports and ocean freight transport.

A direct multimode method for the reduction of vibration induced oscillations on force signals during “pseudo-rigid” water impact experiments

A new experimental method is proposed to improve the force measurements during water impact experiments (e.g. water entry or wave impact tests) carried out with “pseudo-rigid” mock-ups. Despite the efforts of making the mock-up as stiff as possible, the impulsive nature of water impact loads may induce a transient response of the mock-up with a broad frequency content and a perturbation of the force measurements. Using the principles of momentum conservation, it can be shown that the load cell signal is the sum of the hydrodynamic forcing term and of an additional inertial term directly related to the vibrations of the structure. In the present paper, we suggest to estimate the inertial term using several accelerometers which record the response of the structure at different locations. Assuming that the structure response can be approximated by a set of natural modes, we show that it is possible to estimate the inertial term by a linear combination of the acceleration signals. The coefficients of the linear combination may be identified a priori by performing hammer tests, but in certain cases they can also be identified a posteriori using a segment of the signal time series. The performance of the method is demonstrated by considering two experimental test cases of increasing complexity. The first test case is a hydrofoil of constant section impacting water at constant speed which exhibits two-dimensional beam-like vibrations. The second test case is a segmented model of a vertical cylinder impacted by a breaking wave whose segments exhibit three-dimensional vibrations. The proposed method is efficient, conceptually simple and very simple to implement from a signal processing point of view, which makes it promising not only for water impact problems but also for other unstationary fluid–structure interaction problems.

Investigation of water wave characteristics and impact behavior on the side wall

Investigation of water wave characteristics and impact behavior on the side wall

A Moving-Wave Implementation in WRF to Study the Impact of Surface Water Waves on the Atmospheric Boundary Layer

Abstract While numerous modeling studies have focused on the interaction of ocean surface waves with the atmospheric boundary layer, most employ idealized waves that are either monochromatic or synthetically generated from a theoretical wave spectrum, and the atmospheric solvers are typically incompressible. To study wind–wave coupling in real-world scenarios, a model that can simulate both realistic meteorological and wave conditions is necessary. In this paper we describe the implementation of a moving bottom boundary condition into the Weather Research and Forecasting Model for large-eddy simulation applications. We first describe the moving bottom boundary conditions within WRF’s pressure-based vertical coordinate system. We then validate our code with idealized test cases that have analytical solutions, including flow over a monochromatic wave with and without viscosity. Finally, we present results from turbulent flows over a moving monochromatic wave with different wave ages, and demonstrate satisfactory agreement of the wave growth rate with results from the literature. We also compare atmospheric stress and wind parameters from two physically equivalent cases. The first specifies a wind moving in the same direction as a propagating wave, while the second involves a stationary wave with the wind adjusted such that the wind relative to the wave is the same as in the first case. Results indicate that the velocity and Reynolds stress profiles for the two cases match, further validating the moving bottom implementation.

Required test durations for converged short-term wave and impact extreme value statistics — Part 1: Ferry dataset

For the design of maritime structures in waves, the extreme values of responses such as motions and wave impact loads are required. Waves and wave-induced responses are stochastic, so such responses should always be related to a probability. This information is not easy to obtain for strongly non-linear responses such as wave impact forces. Usually class rules or direct assessment via experiments or numerical simulations are applied to obtain extreme values for design. This brings up questions related to the convergence of extreme values: how long do we need to test in order to obtain converged statistics for the target duration? Or, vice versa: given testing data, what is the uncertainty of the associated statistics? Often the test or simulation duration is cut up in ‘seeds’ or ‘realisations’, with an exposure duration of one or three hours based on the typical duration of a steady environmental condition at sea, or the time that a ship sails a single course. The required number of seeds for converged results depends on the type of structure and response, the exposure duration, and the desired probability level. The present study provides guidelines for the convergence of most probable maximum (MPM) wave crest heights and MPM green water wave impact forces on a ferry. Long duration experiments were done to gain insight into the required number of seeds, and the effect of fitting. The present paper presents part 1 of this study; part 2 [1] presents similar results for wave-in-deck loads on a stationary deck box.

Deep learning of inverse water waves problems using multi-fidelity data: Application to Serre–Green–Naghdi equations

We consider strongly-nonlinear and weakly-dispersive surface water waves governed by equations of Boussinesq type, known as the Serre–Green–Naghdi system; it describes future states of the free water surface and depth averaged horizontal velocity, given their initial state. The lack of knowledge of the velocity field as well as the initial states provided by measurements lead to an ill-posed problem that cannot be solved by traditional techniques. To this end, we employ physics-informed neural networks (PINNs) to generate solutions to such ill-posed problems using only data of the free surface elevation and depth of the water. PINNs can readily incorporate the physical laws and the observational data, thereby enabling inference of the physical quantities of interest. In the present study, both experimental and synthetic (generated by numerical methods) training data are used to train PINNs. Furthermore, multi-fidelity data are used to solve the inverse water wave problem by leveraging both high- and low-fidelity data sets. The applicability of the PINN methodology for the estimation of the impact of water waves onto solid obstacles is demonstrated after deriving the corresponding equations. The present methodology can be employed to efficiently design offshore structures such as oil platforms, wind turbines, etc. by solving the corresponding ill-posed inverse water waves problem.

Real-Time Detection Algorithm of Marine Organisms Based on Improved YOLOv4-Tiny

Marine organisms detection based on machine vision requires high real-time performance and accuracy. Network feature extraction is frequently made more difficult when underwater robots collect information on the seafloor because of the uneven distribution of light on the seafloor, the significant impact of water waves, and the complexity of the seafloor environment. How to detect marine organisms quickly and accurately is a great difficulty and challenge. To address the above problems, we propose a MODA (Marine Organism Detection Algorithm) based on an improved YOLOv4-tiny marine organism detection algorithm. Firstly, the Coordinate Attention module, an ultra-lightweight attention mechanism, is constructed and embedded into the backbone network to retain more information about the target of interest and enhance the feature extraction capability of the network. Secondly, the Hybrid Dilated Convolution (HDC) structure is constructed and added to the improved network to expand the feature map perception field and obtain richer semantic information to improve the network detection accuracy. Finally, a better MODA model is proposed based on the two methods mentioned above. The experimental results show that the improved model MODA improves the mAP metric from 74% to 76.62% on the URPC dataset and only increases the computational effort by 0.06 GM compared with the original YOLOv4-tiny model; the mAP metric improves from 92.37% to 98.41% on the Aquarium dataset. This improvement indicates that the MODA model is more suitable for marine organisms detection tasks.

Image Sensors for Wave Monitoring in Shore Protection: Characterization through a Machine Learning Algorithm.

Waves propagating on the water surface can be considered as propagating in a dispersive medium, where gravity and surface tension at the air–water interface act as restoring forces. The velocity at which energy is transported in water waves is defined by the group velocity. The paper reports the use of video-camera observations to study the impact of water waves on an urban shore. The video-monitoring system consists of two separate cameras equipped with progressive RGB CMOS sensors that allow 1080p HDTV video recording. The sensing system delivers video signals that are processed by a machine learning technique. The scope of the research is to identify features of water waves that cannot be normally observed. First, a conventional modelling was performed using data delivered by image sensors together with additional data such as temperature, and wind speed, measured with dedicated sensors. Stealth waves are detected, as are the inverting phenomena encompassed in waves. This latter phenomenon can be detected only through machine learning. This double approach allows us to prevent extreme events that can take place in offshore and onshore areas.

Three Dimensional Cellular Automata Sand Castle construction Model Based on Step Factor

It seems that everyone has the experience of making sandcastles on the leisure beach. In order to know how to build a beautiful and sturdy beach castle, this article simulates and analyzes the process of sand castles being eroded by water, and obtains some factors that extend the life of sand castles. First, we model the waves. Simplify the waves into a sine wave. Using calculus and fluid mechanics, the water wave impact force on a particle on the sand castle was calculated. Second, we model the sandcastle. Discretizing time, space, and state, we innovatively introduce the concepts of friction and impact into the model, and propose a new Three-dimensional Cellular Automaton model combined with step factors. We consider each gravel or water molecule as a cell, and simultaneously introduce the moving probability and collision probability to describe the moving trend and collision between the gravel cells, respectively. In order to effectively describe the loss of sand castles in the waves, the gravel cells that are in direct contact with the water cells will receive an impact force calculated by the first model. According to the law of large numbers, we use enough cells to simulate the erosion of sandcastles by the waves. It was found that within a certain range, the farther from the ocean and the more the total gravel, the stronger the anti-erosion ability of the sand castle.

A Sustainable Blue Energy Scavenging Smart Buoy toward Self-Powered Smart Fishing Net Tracker

Water is abundantly present on Earth. Water waves have the unique feature of being random and irregular. The impact of water waves can be utilized to derive power by employing a triboelectric nanog...

A Comprehensive Study of the Wave Impact Loads on an Inclined Plate

Water wave impact on a wet deck is an important issue in ocean engineering, and the plate-shaped structure in the splash zone tends to suffer tremendous impact loads. This work presents a method for predicting the wave slamming uplift force on a fixed plate with different inclined angles. Both numerical simulation and the scale model test of the wave impact loads on an inclined plate were performed, and a good agreement was obtained. In addition, the influence of three important wave parameters on the slamming uplift force was systematically investigated: relative deck width B/LS, relative wave height Δh/H1/3, and the plate’s inclined angle α. The results indicate that the three parameters can significantly influence the wave slamming uplift force. Finally, a developed empirical equation is proposed for estimating the wave slamming uplift force on the inclined plate.

Characterization of strain relaxation behavior in Si1−xGex epitaxial layers by dry oxidation

We report an arch-shaped triboelectric nanogenerator (A-TENG) as for a simple and effective water-wave energy harvesting device. The A-TENG consists of arch-shaped polyethylene terephthalate (PET) polymer film and flat Al metal electrode. Especially, the arch-shape of PET provides an inherent restoring force after the contact with Al; which significantly reduces the weight and volume of the TENG. For a mild mechanical impact of water waves with an amplitude of 5 cm and frequency of 1 Hz, the single A-TENG unit generates an open-circuit voltage of 8 V and closedcircuit current of 200 nA. In addition, two A-TENG units connected in parallel generate almost double the voltage and current. These results imply that the scaled-up A-TENG units could be used at water-breakers in coastal areas for effective harvesting of ocean wave mechanical energy.

Feasibility analysis of marine ecological on-line integrated monitoring system

The in-situ water quality sensors were susceptible to biological attachment. Moreover, sea water corrosion and wave impact damage, and many sensors scattered distribution would cause maintenance inconvenience. The paper proposed a highly integrated marine ecological on-line integrated monitoring system, which can be used inside monitoring station. All sensors were reasonably classified, the similar in series, the overall in parallel. The system composition and workflow were described. In addition, the paper proposed attention issues of the system design and corresponding solutions. Water quality multi-parameters and 5 nutrient salts as the verification index, in-situ and systematic data comparison experiment were carried out. The results showed that the data consistency of nutrient salt, PH and salinity was better. Temperature and dissolved oxygen data trend was consistent, but the data had deviation. Turbidity fluctuated greatly; the chlorophyll trend was similar with it. Aiming at the above phenomena, three points system optimization direction were proposed.

Statistical process control analysis for patient quality assurance of intensity modulated radiation therapy

We report an arch-shaped triboelectric nanogenerator (A-TENG) as for a simple and effective water-wave energy harvesting device. The A-TENG consists of arch-shaped polyethylene terephthalate (PET) polymer film and flat Al metal electrode. Especially, the arch-shape of PET provides an inherent restoring force after the contact with Al; which significantly reduces the weight and volume of the TENG. For a mild mechanical impact of water waves with an amplitude of 5 cm and frequency of 1 Hz, the single A-TENG unit generates an open-circuit voltage of 8 V and closedcircuit current of 200 nA. In addition, two A-TENG units connected in parallel generate almost double the voltage and current. These results imply that the scaled-up A-TENG units could be used at water-breakers in coastal areas for effective harvesting of ocean wave mechanical energy.

Modelling of Violent Water Wave Propagation and Impact by Incompressible SPH with First-Order Consistent Kernel Interpolation Scheme

The Smoothed Particle Hydrodynamics (SPH) method has proven to have great potential in dealing with the wave–structure interactions since it can deal with the large amplitude and breaking waves and easily captures the free surface. The paper will adopt an incompressible SPH (ISPH) approach to simulate the wave propagation and impact, in which the fluid pressure is solved using a pressure Poisson equation and thus more stable and accurate pressure fields can be obtained. The focus of the study is on comparing three different pressure gradient calculation models in SPH and proposing the most efficient first-order consistent kernel interpolation (C1_KI) numerical scheme for modelling violent wave impact. The improvement of the model is validated by the benchmark dam break flows and laboratory wave propagation and impact experiments.

Charging System Optimization of Triboelectric Nanogenerator for Water Wave Energy Harvesting and Storage.

Ocean waves are one of the most promising renewable energy sources for large-scope applications due to the abundant water resources on the earth. Triboelectric nanogenerator (TENG) technology could provide a new strategy for water wave energy harvesting. In this work, we investigated the charging characteristics of utilizing a wavy-structured TENG to charge a capacitor under direct water wave impact and under enclosed ball collision, by combination of theoretical calculations and experimental studies. The analytical equations of the charging characteristics were theoretically derived for the two cases, and they were calculated for various load capacitances, cycle numbers, and structural parameters such as compression deformation depth and ball size or mass. Under the direct water wave impact, the stored energy and maximum energy storage efficiency were found to be controlled by deformation depth, while the stored energy and maximum efficiency can be optimized by the ball size under the enclosed ball collision. Finally, the theoretical results were well verified by the experimental tests. The present work could provide strategies for improving the charging performance of TENGs toward effective water wave energy harvesting and storage.

DYNAMIC ANALYSIS OF JACKET TYPE OFFSHORE STRUCTURE UNDER IMPACT OF WAVE AND WIND USING STOKE’S SECOND ORDER WAVE THEORY

This paper presents finite element algorithms and dynamic analysis of the jacket type offshore structure under water wave and wind impact by using stoke’s second order wave theory. The result of the paper is the scientific basis for the calculation, design and selection of the appropriate parameters, the study contributes to the optimization of fixed offshore structures such as buildings DKI, serving defense, security and contributing to improving the capacity to defend Vietnam’s sovereignty over seas and islands.

A multi-layered interdigitative-electrodes-based triboelectric nanogenerator for harvesting hydropower

Hydropower is the most important and wildly-used renewable energy source in the environment. In this paper, we demonstrate a multi-layered triboelectric nanogenerator (TENG) to effectively harvest the water wave energy. For a single-layered TENG, interdigitive electrodes are incorporated in order to generate multiple electric outputs under water wave or water drop impact. For the collection of water wave energy, a polyurethane (PU) coated copper rod is used to roll back and forth and contact with the polytetrafluoroethylene (PTFE) film covered interdigitative electrodes. The surfaces of the PU and PTFE films are fabricated as porous structures and nanowire arrays, which provide an advantages of large contact area and efficient separation. Under one wave impact, the single-layered TENG composed of nine pairs of interdigitative electrodes can provide nine pulses of electric outputs (each pulsed output voltage is 52V and output current density is 13.8mAm−2). The instantaneous output power density of a five-layered TENG is 1.1Wm−2. In addition, the PTFE film covered interdigitative electrodes has been successfully used to harvest water drop energy, whcih can also generate 9 pulses of electric outputs upon one water drop falling. All these results show the developed TENG has a potential to harvest the hydropower of ocean wave and raindrop in the near future.

Incompressible SPH Based on Rankine Source Solution for Water Wave Impact Simulation

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian meshless particle method. It was originally developed to simulate astrodynamics but has been extended to model dynamics problems with violent motions in many areas. This paper is based on ISPH and its pressure time history is transformed into another equation based on a Rankine source solution. In the new formulation of ISPH, the governing equation for pressure does not include any derivatives of unknown functions and so overcomes the problems associated with direct numerical approximation to second derivatives in existing ISPH formulation, and some important numerical handling techniques will also be included, like free surface particle identification method and solid boundary discrete scheme. The newly improved method will be applied to model various wave and wave impact interaction with different angle slopes, and the results of comparison with experimental data are also given. According to the comparison of pressure time history, this new method can get a good agreement with experimental results.

Comparative study of different SPH schemes on simulating violent water wave impact flows

Free surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH (WCSPH) uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH (ISPH) technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.