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1
Mori, Nobuhito, Hajime Mase und Tomohiro Yasuda. „FREAK WAVE AND WEATHER CONDITION“. Coastal Engineering Proceedings 1, Nr. 32 (01.02.2011): 70. http://dx.doi.org/10.9753/icce.v32.waves.70.
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The kurtosis of the surface elevation, Benjamin-Feir Index (BFI) and directional spread are measures of nonlinear four-wave interactions and freak waves. The dependence of kurtosis, BFI and directional spread under typhoon conditions are examined by numerical simulations. The BFI is significantly large in the fourth quadrant of the typhoon while the directional spread is small in the fourth quadrant. It was found that the potentially possible area of freak wave occurrence is the fourth quadrant of the typhoon rather than the other quadrants.
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Yu, Wen, Fenggang Wang, Jianguo Lin und Dong Li. „Numerical Simulation of the Force Acting on the Riser by Two Internal Solitary Waves“. Applied Sciences 12, Nr. 10 (11.05.2022): 4873. http://dx.doi.org/10.3390/app12104873.
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An internal wave is a typical dynamic process. As an internal wave, an internal solitary wave usually occurs between two layers of fluids with different densities. Compared with general internal waves, internal solitary waves have large amplitudes, fast propagation speeds, short-wave periods, and often have tremendous energy. The propagation causes strong convergence and divergence of seawater and generates a sudden strong current. Due to its various characteristics, the propagation of internal solitary waves can cause serious harm to offshore engineering structures. Therefore, studying the effects of internal solitary waves on risers is vital in preventing environmental pollution caused by riser damage. Although the research on internal solitary waves has achieved very fruitful results, the research on structures is mostly focused on a single condition, and the occurrence of internal solitary wave, as a complex ocean phenomenon, is often accompanied by many situations. Therefore, this paper constructs a numerical simulation of the interaction between two columns of internal solitary waves and risers. This study explores the force and flow field changes of the riser under the condition of multiple internal solitary waves using the Star-CCM+ software in the simulation. The improved K-epsilon turbulence model was adopted to close the three-dimensional incompressible Navier–Stokes equation, and the solitary wave solution of the eKdV equation was used as the initial and boundary conditions. The interaction between single and double internal solitary waves and a riser was calculated, compared, and analyzed using numerical analysis. The experiment results indicate that the conditions of two internal solitary waves differ from those of a single internal solitary wave. After colliding at the riser, the waves gradually merge into a single wave, and the flow field reaches its minimum velocity. Under the two-wave condition, the horizontal force on the riser as a whole is less than the single-wave condition. As the amplitude difference between the two internal solitary waves gradually decreases, the horizontal opposing force received by the riser first increases and then decreases, while the horizontal positive force gradually decreases.
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Tang, Haoyun, Huilong Ren, Hui Li und Qi Zhong. „Experimental Investigation of Wave-Induced Hydroelastic Vibrations of Trimaran in Oblique Irregular Waves“. Shock and Vibration 2016 (2016): 1–17. http://dx.doi.org/10.1155/2016/8794560.
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The irregular wave condition, especially the oblique irregular wave condition, is the actual circumstances when trimaran is sailing in sea. In order to identify the characteristic of the wave-induced hydroelastic vibration in irregular waves, as well as investigate the change of vibration in different oblique irregular wave conditions, trimaran model tests were conducted to measure vibrations, wave impact, and motion under different azimuth and wave height. The vibration on main hull, side hull, and cross-desk is measured and analyzed separately to observe the influence of irregular wave in different structural parts. The longitudinal vibration, transverse vibration, and torsion are also included in the model tests measurement to investigate the relationship between these vibration deformation components and parameters of the irregular waves. The wave-induced hydroelastic vibrations and whipping effect is extracted and analyzed to find influence of whipping and springing on the total vibration. Based on the analysis, the dangerous positions and the critical waves condition is introduced to ensure that the subsequent structural strength assessment is more reliable.
4
Stresswave Technology Ltd. „Stress wave condition monitoring“. NDT & E International 23, Nr. 4 (August 1990): 240. http://dx.doi.org/10.1016/0963-8695(90)90978-r.
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Stresswave Technology Ltd. „Stress wave condition monitoring“. NDT International 23, Nr. 4 (August 1990): 240. http://dx.doi.org/10.1016/0308-9126(90)91714-5.
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6
Ismail, Mohd Arif, Nik Mohd Ridzuan Shaharuddin, Omar Yaakob, Mohamad Hidayat Jamal, Faizul Amri Adnan, Ahmad Hadi Mohamed Rashidi, Wan Ahmad Hafiz Wan Mohd Azhary et al. „WAKE WASH OF A FAST SMALL BOAT IN RESTRICTED WATERS: MODEL TESTS AND FULL-SCALE MEASUREMENTS“. Brodogradnja 73, Nr. 2 (01.03.2022): 93–119. http://dx.doi.org/10.21278/brod73206.
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This paper presents the model testing of an 8.23m boat with hard chine planning hull generated waves at the Kilim recreational park. Wake is considered one of the main causes of riverbank erosion due to the energy carried by waves hitting the riverbank. Initially, ship particulars were measured from actual boats to generate a hull form using MAXSURF software. A lines plan was then generated to fabricate the model using fibreglass. Experiments were conducted in the National Hydraulic Research Institute of Malaysia (NAHRIM) at various speeds at a constant operating draft. The wave patterns generated by the modelled boats at different speeds were recorded for analysis. Wave attenuation for deep water conditions was studied and it was found that the wave exponent, n ranged from -0.36 to -0.75 for all depth Froude number (Fnh) condition. Wave decay analysis was used to estimate wave height for defined water depth. For 11 people with an average mass of 65 kg on board, the produced wave height was greater than the permissible wave wake height of 75 mm. The generated energy exceeded 60 Joules/m for nearly all measured speeds. A boat speed of less than 5 knots was suggested for boats loaded with the maximum passenger limit of 11 people. Other recommendations were made to minimize the wave wake height produced by the modelled boat.
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Lamacz, A., und B. Schweizer. „Outgoing wave conditions in photonic crystals and transmission properties at interfaces“. ESAIM: Mathematical Modelling and Numerical Analysis 52, Nr. 5 (September 2018): 1913–45. http://dx.doi.org/10.1051/m2an/2018026.
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We analyze the propagation of waves in unbounded photonic crystals. Waves are described by a Helmholtz equation with x-dependent coefficients, the scattering problem must be completed with a radiation condition at infinity. We develop an outgoing wave condition with the help of a Bloch wave expansion. Our radiation condition admits a uniqueness result, formulated in terms of the Bloch measure of solutions. We use the new radiation condition to analyze the transmission problem where, at fixed frequency, a wave hits the interface between free space and a photonic crystal. We show that the vertical wave number of the incident wave is a conserved quantity. Together with the frequency condition for the transmitted wave, this condition leads (for appropriate photonic crystals) to the effect of negative refraction at the interface.
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Randall, C. J. „Absorbing boundary condition for the elastic wave equation“. GEOPHYSICS 53, Nr. 5 (Mai 1988): 611–24. http://dx.doi.org/10.1190/1.1442496.
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Extant absorbing boundary conditions for the elastic wave equation are generally effective only for waves nearly normally incident upon the boundary. High reflectivity is exhibited for waves traveling obliquely to the boundary. In this paper, a new and efficient absorbing boundary condition for two‐dimensional and three‐dimensional finite‐difference calculations of elastic wave propagation is presented. Compressional and shear components of the incident vector displacement fields are separated by calculating intermediary scalar potentials, allowing the use of Lindman’s boundary condition for scalar fields, which is highly absorbing for waves incident at any angle. The elastic medium is assumed to be homogeneous in the region immediately adjacent to the boundary. The reflectivity matrix of the resulting absorbing boundary for elastic waves is calculated, including the effects of finite‐difference truncation error. For effectively all angles of incidence, reflectivities are much smaller than those of the commonly employed paraxial absorbing boundaries, and the boundary condition is stable for any physical Poisson’s ratio. The nearly complete absorption predicted by the reflectivity matrix calculations, even at near grazing incidence, is demonstrated in a finite‐difference application.
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Taniguchi, Kenji. „Variations in Winter Ocean Wave Climate in the Japan Sea under the Global Warming Condition“. Journal of Marine Science and Engineering 7, Nr. 5 (15.05.2019): 150. http://dx.doi.org/10.3390/jmse7050150.
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Future variations in the ocean wave climate caused by global warming could affect various coastal issues. Using a third-generation wave model, this study produced projections of the ocean wave climate for winter around Japan, focusing on the Japan Sea side. Wave simulation forcing (sea surface wind) was generated through five different global warming experiments. More than half the future wave projections showed an increasing tendency of the climatological mean significant wave height during winter. However, the maximum significant wave height did not show any clear tendency in future variation. The top 1% of significant wave heights and mean wave periods showed apparent increases in frequencies of higher/longer waves in three out of the five future projections. Frequency distributions of significant wave height, mean wave period, mean wavelength and wave direction showed various future variations (reduction of small ocean waves, increasing frequency of waves from the west). There are large uncertainties in future variations of wave climate in the Japan Sea, but the high probability of variations in daily wave climate is recognized, based on the future wave projections. Variations in daily wave climate are important because they could affect the topography and environment of the coast through long-term repetitive actions.
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Shin, Changsoo. „Sponge boundary condition for frequency‐domain modeling“. GEOPHYSICS 60, Nr. 6 (November 1995): 1870–74. http://dx.doi.org/10.1190/1.1443918.
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Several techniques have been developed to get rid of edge reflections from artificial boundaries. One of them is to use paraxial approximations of the scalar and elastic wave equations. The other is to attenuate the seismic waves inside the artificial boundary by a gradual reduction of amplitudes. These techniques have been successfully applied to minimize unwanted seismic waves for time‐domain seismic modeling. Unlike time‐domain seismic modeling, suppression of edge reflections from artificial boundaries has not been successful in frequency‐domain seismic modeling. Rayleigh waves caused by coupled motions of P‐ and S‐waves near the surface have been a particularly difficult problem to overcome in seismic modeling. In this paper, I design a damping matrix for frequency‐ domain modeling that damps out seismic waves by adding a diffusion term to the wave equation. This technique can suppress unwanted seismic waves, including Rayleigh waves and P‐ and S‐waves from an artificial boundary.
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Li, Lei, P. W. Chan, Lijie Zhang und Fei Hu. „Numerical Simulation of a Lee Wave Case over Three-Dimensional Mountainous Terrain under Strong Wind Condition“. Advances in Meteorology 2013 (2013): 1–13. http://dx.doi.org/10.1155/2013/304321.
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This study of a lee wave event over three-dimensional (3D) mountainous terrain in Lantau Island, Hong Kong, using a simulation combining mesoscale model and computational fluid dynamics (CFD) model has shown that (1) 3D steep mountainous terrain can trigger small scale lee waves under strong wind condition, and the horizontal extent of the wave structure is in a dimension of few kilometers and corresponds to the dimension of the horizontal cross-section of the mountain; (2) the life cycle of the lee wave is short, and the wave structures will continuously form roughly in the same location, then gradually move downstream, and dissipate over time; (3) the lee wave triggered by the mountainous terrain in this case can be categorized into “nonsymmetric vortex shedding” or “turbulent wake,” as defined before based on water tank experiments; (4) the magnitude of the wave is related to strength of wind shear. This study also shows that a simulation combining mesoscale model and CFD can capture complex wave structure in the boundary layer over realistic 3D steep terrain, and have a potential value for operational jobs on air traffic warning, wind energy utilization, and atmospheric environmental assessment.
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Xu, Shanshan, und Frédéric Dias. „Long Wave Run-Up Resonance in a Multi-Reflection System“. Applied Sciences 10, Nr. 18 (04.09.2020): 6172. http://dx.doi.org/10.3390/app10186172.
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Wave reflection and wave trapping can lead to long wave run-up resonance. After reviewing the theory of run-up resonance in the framework of the linear shallow water equations, we perform numerical simulations of periodic waves incident on a linearly sloping beach in the framework of the nonlinear shallow water equations. Three different types of boundary conditions are tested: fully reflective boundary, relaxation zone, and influx transparent boundary. The effect of the boundary condition on wave run-up is investigated. For the fully reflective boundary condition, it is found that resonant regimes do exist for certain values of the frequency of the incoming wave, which is consistent with theoretical results. The influx transparent boundary condition does not lead to run-up resonance. Finally, by decomposing the left- and right-going waves into a multi-reflection system, we find that the relaxation zone can lead to run-up resonance depending on the length of the relaxation zone.
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Vay, J. L. „'Transmitted-wave' boundary condition for the wave equation multiscale computation of electromagnetic waves“. IEEE Transactions on Magnetics 34, Nr. 5 (1998): 2688–91. http://dx.doi.org/10.1109/20.717623.
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Wu, Ping-Chen, Md Alfaz Hossain, Naoki Kawakami, Kento Tamaki, Htike Aung Kyaw, Ayaka Matsumoto und Yasuyuki Toda. „EFD and CFD Study of Forces, Ship Motions, and Flow Field for KRISO Container Ship Model in Waves“. Journal of Ship Research 64, Nr. 01 (01.03.2020): 61–80. http://dx.doi.org/10.5957/jsr.2020.64.1.61.
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Ship motion responses and added resistance in waves have been predicted by a wide variety of computational tools. However, validation of the computational flow field still remains a challenge. In the previous study, the flow field around the Korea Research Institute for Ships and Ocean Engineering (KRISO) Very Large Crude-oil Carrier 2 tanker model with and without propeller condition and without rudder condition was measured by the authors, as well as the resistance and self-propulsion tests in waves. In this study, the KRISO container ship model appended with a rudder was used for the higher Froude number .26 and smaller block coefficient .65. The experiments were conducted in the Osaka University towing tank using a 3.2-m-long ship model for resistance and self-propulsion tests in waves. Viscous flow simulation was performed by using CFDShip-Iowa. The wave conditions proposed in Computational Fluid Dynamics (CFD) Workshop 2015 were considered, i.e., the wave-ship length ratio λ/L = .65, .85, 1.15, 1.37, 1.95, and calm water. The objective of this study was to validate CFD results by Experimental Fluid Dynamics (EFD) data for ship vertical motions, added resistance, and wake flow field. The detailed flow field for nominal wake and self-propulsion condition will be analyzed for λ/L = .65, 1.15, 1.37, and calm water. Furthermore, bilge vortex movement and boundary layer development on propeller plane, propeller thrust, and wake factor oscillation in waves will be studied.
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Conceição, Ana, António J. Silva, José Boaventura, Daniel A. Marinho und Hugo Louro. „Wave Characteristics in Breaststroke Technique with and Without Snorkel Use“. Journal of Human Kinetics 39, Nr. 1 (01.12.2013): 185–94. http://dx.doi.org/10.2478/hukin-2013-0081.
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Abstract The purpose of this paper was to examine the characteristics of waves generated when swimming with and without the use of Aquatrainer® snorkels. Eight male swimmers performed two maximal bouts of 25 m breaststroke, first without the use of a snorkel (normal condition) and then using a snorkel (snorkel condition). The body landmarks, centre of the mass velocity, stroke rate, stroke length, stroke index, and Strouhal number (St) were quantified. Fourier analysis was conducted to determine the frequency, amplitude, and phase characteristics of the vertical undulations. We also determined the undulation period, the first and second harmonic wave percentage, and the contribution of these components to the power of each of the wave signals. The first wave harmonics had a frequency of 0.76 Hz (normal condition) and 0.78 Hz (snorkel condition), and the second wave harmonics had a frequency of 1.52 Hz (normal condition) and 1.56 Hz (snorkel condition). Under the normal conditions, the wave amplitude was higher on the vertex (0.72 m) and cervical (0.32 m) than that produced under snorkel conditions (0.71 m and 0.28 m, respectively). The lowest values were found in the hip (0.03 m in normal conditions, and 0.02 m in snorkel conditions) and in the trunk (0.06 m in normal conditions, and 0.04 m in snorkel conditions). It can be concluded that snorkel use seems to lead to slight changes in the biomechanical pattern in swimming velocity, as well as several stroke mechanical variables.
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Stern, F., J. E. Choi und W. S. Hwang. „Effects of Waves on the Wake of a Surface-Piercing Flat Plate: Experiment and Theory“. Journal of Ship Research 37, Nr. 02 (01.06.1993): 102–18. http://dx.doi.org/10.5957/jsr.1993.37.2.102.
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Results are presented from a towing-tank experiment conducted in order to document the effects of waves on the wake of a surface-piercing body. A unique, simple model geometry is utilized which makes it possible to isolate and identify the most important features of the wave-induced effects. Measurements were made for three wave-steepness conditions: zero, medium, and large. The effects of the waves for the latter two conditions are shown to be significant. In particular, the variations of the external-flow pressure gradients cause acceleration and deceleration phases of the streamwise velocity component and alternating direction of the crossflow, which results in large oscillations of the displacement thickness and wake centerplane velocities as compared to the zero-steepness condition. Remarkably, the wake displays a greater response, that is, a bias with regard to favorable as compared to adverse pressure gradients. The measurements are compared and close agreement is demonstrated with results from Reynolds-averaged Navier-Stokes calculations. Additional calculations are presented, including laminar-flow results, which aid in explicating the characteristics of the near and intermediate wake, the periodic nature of the far wake, and wave-induced separation. Previously, experimental and computational results were presented for the boundary-layer region.
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Islam, Muhammad Rabiul, Mahmudul Hasan Akib, Fariha Tabassum und Khandakar Akhter Hossain. „ON THE INVESTIGATION OF WIND GENERATED WAVES IN BANGLADESH RIVERS FOR THE ASSESSMENT OF STABILITY REQUIREMENTS IN INLAND VESSEL DESIGN“. Brodogradnja 72, Nr. 3 (01.07.2021): 45–59. http://dx.doi.org/10.21278/brod72304.
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Standard environmental condition is one of the main inputs in designing a vessel especially in assessment of stability condition. The performance based minimum stability requirements are determined by assessing vessels' dynamic failure modes. Winds as well as wind generated waves are the main factors that affect a specific vessel’s dynamics. Wind generated waves in rivers though are usually small in comparison with ocean waves may play a crucial role behind inland vessels accidents. The river condition of a crucial location in Bangladesh inland river routes is assessed where wind velocities have been taken for a specific duration from a reliable secondary source. A narrow fetch model that considers the wave generation in off-wind direction for estimating wind wave parameters has been used to consider the spiral shape of Bangladesh inland routes. The Bretschneider energy spectrum model for short term wave state is compared with the fetch limited model JONSWAP for the estimated wave condition. This study indicates the rationality of conforming the safety level of Bangladesh inland vessels equivalent to river-sea vessels as defined by other nationals and the classification societies. The wave parameters that are estimated in this study can be used to form a limited wave scatter table for predicting short term environmental conditions to assess the dynamic stability failure modes of the vessels.
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Keys, R. G. „Absorbing boundary conditions for acoustic media“. GEOPHYSICS 50, Nr. 6 (Juni 1985): 892–902. http://dx.doi.org/10.1190/1.1441969.
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By decomposing the acoustic wave equation into incoming and outgoing components, an absorbing boundary condition can be derived to eliminate reflections from plane waves according to their direction of propagation. This boundary condition is characterized by a first‐order differential operator. The differential operator, or absorbing boundary operator, is the basic element from which more complicated boundary conditions can be constructed. The absorbing boundary operator can be designed to absorb perfectly plane waves traveling in any two directions. By combining two or more absorption operators, boundary conditions can be created which absorb plane waves propagating in any number of directions. Absorbing boundary operators simplify the task of designing boundary conditions to reduce the detrimental effects of outgoing waves in many wave propagation problems.
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Shi, He, Jinzhe Gong, Aaron C. Zecchin, Martin F. Lambert und Angus R. Simpson. „Hydraulic transient wave separation algorithm using a dual-sensor with applications to pipeline condition assessment“. Journal of Hydroinformatics 19, Nr. 5 (18.07.2017): 752–65. http://dx.doi.org/10.2166/hydro.2017.146.
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Over the past two decades, techniques have been developed for pipeline leak detection and condition assessment using hydraulic transient waves (i.e. water hammer waves). A common measurement strategy for applications involves analysis of signals from a single pressure sensor located at each measurement site. The measured pressure trace from a single sensor is a superposition of reflections coming from upstream, and downstream, of the sensor. This superposition brings complexities for signal processing applications for fault detection analysis. This paper presents a wave separation algorithm, accounting for transmission dynamics, which enables the extraction of directional travelling waves by using two closely placed pressure sensors at one measurement site (referred to as a dual-sensor). Two typical transient incident pressure waves, a pulse wave and a step wave, are investigated in numerical simulations and laboratory experiments. Comparison of the wave separation results with their predicted counterparts shows the wave separation algorithm is successful. The results also show that the proposed wave separation technique facilitates transient-based pipeline condition assessment.
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Miura, Naoto, und Takashi Watanabe. „Potential of M-Wave Elicited by Double Pulse for Muscle Fatigue Evaluation in Intermittent Muscle Activation by Functional Electrical Stimulation for Motor Rehabilitation“. Journal of Medical Engineering 2016 (27.03.2016): 1–12. http://dx.doi.org/10.1155/2016/6957287.
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Clinical studies on application of functional electrical stimulation (FES) to motor rehabilitation have been increasing. However, muscle fatigue appears early in the course of repetitive movement production training by FES. Although M-wave variables were suggested to be reliable indices of muscle fatigue in long lasting constant electrical stimulation under the isometric condition, the ability of M-wave needs more studies under intermittent stimulation condition, because the intervals between electrical stimulations help recovery of muscle activation level. In this paper, M-waves elicited by double pulses were examined in muscle fatigue evaluation during repetitive movements considering rehabilitation training with surface electrical stimulation. M-waves were measured under the two conditions of repetitive stimulation: knee extension force production under the isometric condition and the dynamic movement condition by knee joint angle control. Amplitude of M-wave elicited by the 2nd pulse of a double pulse decreased during muscle fatigue in both measurement conditions, while the change in M-waves elicited by single pulses in a stimulation burst was not relevant to muscle fatigue in repeated activation with stimulation interval of 1 s. Fatigue index obtained from M-waves elicited by 2nd pulses was suggested to provide good estimation of muscle fatigue during repetitive movements with FES.
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Stern, F., W. S. Hwang und S. Y. Jaw. „Effects of Waves on the Boundary Layer of a Surface-Piercing Flat Plate: Experiment and Theory“. Journal of Ship Research 33, Nr. 01 (01.03.1989): 63–80. http://dx.doi.org/10.5957/jsr.1989.33.1.63.
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Results are presented from a towing-tank experiment conducted in order to document the effects of waves on the boundary layer of a surface-piercing body. A unique, simple model geometry is utilized which makes it possible to identify and isolate the most important features of the wave-induced effects. Measurements were made of wave profiles as well as detailed boundary-layer velocity profiles for three wave-steepness conditions: zero, medium, and large. The effects of the waves for both the medium-and large-steepness conditions are shown to be significant. In particular, the variations of the external-flow piezometric-pressure gradients cause acceleration and deceleration phases of the streamwise velocity component and alternating direction of the crossflow, which result in large oscillations of the displacement thickness and wall-shear stress as compared to the zero-steepness condition. The magnitude of these trends increases with increasing wave steepness. Wave-induced separation, which is present under certain conditions in the experiments, and other relevant phenomena are discussed. The measurements are compared and close agreement is demonstrated with results from first-order boundary-layer calculations with a symmetry-condition approximation for the free-surface boundary conditions.
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Cao, Hong Sheng, Xi Shan Pan, Chun Hui Li, Cong Ying Kong und Wei Yi Zhang. „Nonlinear Wave Mathematical Model and its Application in Permeable Breakwater Harbor“. Applied Mechanics and Materials 303-306 (Februar 2013): 2731–35. http://dx.doi.org/10.4028/www.scientific.net/amm.303-306.2731.
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Non-linear wave influence is considered in the elliptic mild-slope equation including higher-order terms of water depth, and a non-linear wave mathematical model is derived in which reflection and transmission boundary conditions are involved based on Behrent radiation boundary condition. The model was verified with data obtained from experiment of elliptic shoal topography, and numerical simulation result accord with experiment value well. The model is applied to simulate waves in a permeable breakwater harbor and a sound wave height distribution in the harbor is obtained, can reflect reflection and transmission of the boundary impact on wave condition in the harbor well.
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Sung, Mi-Kyung, Seon-Hwa Kim, Baek-Min Kim und Yong-Sang Choi. „Interdecadal Variability of the Warm Arctic and Cold Eurasia Pattern and Its North Atlantic Origin“. Journal of Climate 31, Nr. 15 (August 2018): 5793–810. http://dx.doi.org/10.1175/jcli-d-17-0562.1.
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This study investigates the origin of the interdecadal variability in the warm Arctic and cold Eurasia (WACE) pattern, which is defined as the second empirical orthogonal function of surface air temperature (SAT) variability over the Eurasian continent in Northern Hemisphere winter, by analyzing the Twentieth Century Reanalysis dataset. While previous studies highlight recent enhancement of the WACE pattern, ascribing it to anthropogenic warming, the authors found that the WACE pattern has experienced a seemingly periodic interdecadal variation over the twentieth century. This long-term variation in the Eurasian SAT is attributable to the altered coupling between the Siberian high (SH) and intraseasonal Rossby wave emanating from the North Atlantic, as the local wave branch interacts with the SH and consequentially enhances the continental temperature perturbation. It is further identified that these atmospheric circulation changes in Eurasia are largely controlled by the decadal amplitude modulation of the climatological stationary waves over the North Atlantic region. The altered decadal mean condition of stationary wave components brings changes in local baroclinicity and storm track activity over the North Atlantic, which jointly change the intraseasonal Rossby wave generation and propagation characteristics as well. With simple stationary wave model experiments, the authors confirm how the altered mean flow condition in the North Atlantic acts as a source for the growth of the Rossby wave that leads to the change in the downstream WACE pattern.
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Ranjbar, Monireh, und Ali Bahari. „Phase-matching condition of four-wave mixing in cylindrical nonlinear optical media“. International Journal of Modern Physics B 30, Nr. 25 (28.09.2016): 1650182. http://dx.doi.org/10.1142/s0217979216501824.
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Propagation of cylindrical waves in homogeneous and inhomogeneous nonlinear optical media has been investigated theoretically. The coupled-wave equations for a homogeneous and inhomogeneous nonlinear media have been investigated numerically. For homogeneous media, calculations show that phase-matching condition is not fulfilled and efficiency of output wave is very low, but for inhomogeneous media, phase-matching condition is nearly fulfilled and the generated wave amplitude of the four-wave mixing (FWM) is much larger than the homogeneous media. The effect of effective nonlinear optical coefficient [Formula: see text] on the generated wave amplitude for inhomogeneous media has been investigated.
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Qin, Shufang, Jun Fan, Haiming Zhang, Junwei Su und Yi Wang. „Flume Experiments on Energy Conversion Behavior for Oscillating Buoy Devices Interacting with Different Wave Types“. Journal of Marine Science and Engineering 9, Nr. 8 (08.08.2021): 852. http://dx.doi.org/10.3390/jmse9080852.
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Oscillating buoy device, also known as point absorber, is an important wave energy converter (WEC) for wave energy development and utilization. The previous work primarily focused on the optimization of mechanical design, buoy’s array configuration and the site selection with larger wave energy density in order to improve the wave energy generation performance. In this work, enlightened by the potential availability of Bragg reflection induced by multiple submerged breakwaters in nearshore areas, we investigate the energy conversion behavior of oscillating buoy devices under different wave types (traveling waves, partial and fully standing waves) by flume experiments. The localized partial standing wave field is generated by the Bragg resonance at the incident side of rippled bottoms. Furthermore, the fully standing wave field is generated by the wave reflection of vertical baffle installed in flume. Then the wave power generation performance is discussed under the conditions with the same wave height but different wave types. The experimental measurements show that the energy conversion performance of the oscillating buoy WEC could be improved under the condition of standing waves when compared with traveling waves. This work provides the experimental comparison evidence of wave energy conversion response of oscillating buoy devices between travelling waves and standing (fully or partial) wave conditions.
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Husain, Nyla T., Tetsu Hara, Marc P. Buckley, Kianoosh Yousefi, Fabrice Veron und Peter P. Sullivan. „Boundary Layer Turbulence over Surface Waves in a Strongly Forced Condition: LES and Observation“. Journal of Physical Oceanography 49, Nr. 8 (August 2019): 1997–2015. http://dx.doi.org/10.1175/jpo-d-19-0070.1.
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AbstractThe impact of sea state on air–sea momentum flux (or wind stress) is a poorly understood component of wind–wave interactions, particularly in high wind conditions. The wind stress and mean wind profile over the ocean are influenced by the characteristics of boundary layer turbulence over surface waves, which are strongly modulated by transient airflow separation events; however, the features controlling their occurrence and intensity are not well known. A large-eddy simulation (LES) for wind over a sinusoidal wave train is employed to reproduce laboratory observations of phase-averaged airflow over waves in strongly forced conditions. The LES and observation both use a wave-following coordinate system with a decomposition of wind velocity into mean, wave-coherent, and turbulent fluctuation components. The LES results of the mean wind profile and structure of wave-induced and turbulent stress components agree reasonably well with observations. Both LES and observation show enhanced turbulent stress and mean wind shear at the height of the wave crest, signifying the impact of intermittent airflow separation events. Disparities exist particularly near the crest, suggesting that airflow separation and sheltering are affected by the nonlinearity and unsteadiness of laboratory waves. Our results also suggest that the intensity of airflow separation is most sensitive to wave steepness and the surface roughness parameterization near the crest. These results clarify how the characteristics of finite-amplitude waves can control the airflow dynamics, which may substantially influence the mean wind profile, equivalent surface roughness, and drag coefficient.
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Schlutow, Mark, und Erik Wahlén. „Generalized modulation theory for strongly nonlinear gravity waves in a compressible atmosphere“. Mathematics of Climate and Weather Forecasting 6, Nr. 1 (01.01.2020): 97–112. http://dx.doi.org/10.1515/mcwf-2020-0105.
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Abstract This study investigates strongly nonlinear gravity waves in the compressible atmosphere from the Earth’s surface to the deep atmosphere. These waves are effectively described by Grimshaw’s dissipative modulation equations which provide the basis for finding stationary solutions such as mountain lee waves and testing their stability in an analytic fashion. Assuming energetically consistent boundary and far-field conditions, that is no energy flux through the surface, free-slip boundary, and finite total energy, general wave solutions are derived and illustrated in terms of realistic background fields. These assumptions also imply that the wave-Reynolds number must become less than unity above a certain height. The modulational stability of admissible, both non-hydrostatic and hydrostatic, waves is examined. It turns out that, when accounting for the self-induced mean flow, the wave-Froude number has a resonance condition. If it becomes 1/ 1 / 2 1/\sqrt 2 , then the wave destabilizes due to perturbations from the essential spectrum of the linearized modulation equations. However, if the horizontal wavelength is large enough, waves overturn before they can reach the modulational stability condition.
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Wang, Zhuo, Michael T. Montgomery und Cody Fritz. „A First Look at the Structure of the Wave Pouch during the 2009 PREDICT–GRIP Dry Runs over the Atlantic“. Monthly Weather Review 140, Nr. 4 (April 2012): 1144–63. http://dx.doi.org/10.1175/mwr-d-10-05063.1.
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In support of the National Science Foundation Pre-Depression Investigation of Cloud-systems in the tropics (NSF PREDICT) and National Aeronautics and Space Administration Genesis and Rapid Intensification Processes (NASA GRIP) dry run exercises and National Oceanic and Atmospheric Administration Hurricane Intensity Forecast Experiment (NOAA IFEX) during the 2009 hurricane season, a real-time wave-tracking algorithm and corresponding diagnostic analyses based on a recently proposed tropical cyclogenesis model were applied to tropical easterly waves over the Atlantic. The model emphasizes the importance of a Lagrangian recirculation region within a tropical-wave critical layer (the so-called pouch), where persistent deep convection and vorticity aggregation as well as column moistening are favored for tropical cyclogenesis. Distinct scenarios of hybrid wave–vortex evolution are highlighted. It was found that easterly waves without a pouch or with a shallow pouch did not develop. Although not all waves with a deep pouch developed into a tropical storm, a deep wave pouch had formed prior to genesis for all 16 named storms originating from monochromatic easterly waves during the 2008 and 2009 seasons. On the other hand, the diagnosis of two nondeveloping waves with a deep pouch suggests that strong vertical shear or dry air intrusion at the middle–upper levels (where a wave pouch was absent) can disrupt deep convection and suppress storm development. To sum up, this study suggests that a deep wave pouch extending from the midtroposphere (~600–700 hPa) down to the boundary layer is a necessary condition for tropical cyclone formation within an easterly wave. It is hypothesized also that a deep wave pouch together with other large-scale favorable conditions provides a sufficient condition for sustained convection and tropical cyclone formation. This hypothesized sufficient condition requires further testing and will be pursued in future work.
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Jung, Jae-Sang, und Changhoon Lee. „An Analytical Study of Regular Waves Generated by Bottom Wave Makers in a 3-Dimensional Wave Basin“. Journal of Korean Society of Coastal and Ocean Engineers 34, Nr. 4 (31.08.2022): 93–99. http://dx.doi.org/10.9765/kscoe.2022.34.4.93.
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Analytical solutions for regular waves generated by bottom wave makers in a 3-dimensional wave basin were derived in this study. Bottom wave makers which have triangular, rectangular and combination of two shapes were adopted. The 3-dimensional velocity potential was derived based on the linear wave theory with the bottom moving boundary condition, kinematic and dynamic free surface boundary conditions in a wave basin. Then, analytical solutions of 3-dimensional particle velocities and free surface displacement were derived from the velocity potential. The solutions showed physically valid results for regular waves generated by bottom wave makers in a wave basin. The analytical solution for obliquely propagating wave generation from bottom wave maker which works like a snake was also derived. Numerical results of the solution agree well with theoretically predicted results.
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Hara, Tetsu, und Peter P. Sullivan. „Wave Boundary Layer Turbulence over Surface Waves in a Strongly Forced Condition“. Journal of Physical Oceanography 45, Nr. 3 (März 2015): 868–83. http://dx.doi.org/10.1175/jpo-d-14-0116.1.
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AbstractAccurate predictions of the sea state–dependent air–sea momentum flux require a thorough understanding of the wave boundary layer turbulence over surface waves. A set of momentum and energy equations is derived to formulate and analyze wave boundary layer turbulence. The equations are written in wave-following coordinates, and all variables are decomposed into horizontal mean, wave fluctuation, and turbulent fluctuation. The formulation defines the wave-induced stress as a sum of the wave fluctuation stress (because of the fluctuating velocity components) and a pressure stress (pressure acting on a tilted surface). The formulations can be constructed with different choices of mapping. Next, a large-eddy simulation result for wind over a sinusoidal wave train under a strongly forced condition is analyzed using the proposed formulation. The result clarifies how surface waves increase the effective roughness length and the drag coefficient. Specifically, the enhanced wave-induced stress close to the water surface reduces the turbulent stress (satisfying the momentum budget). The reduced turbulent stress is correlated with the reduced viscous dissipation rate of the turbulent kinetic energy. The latter is balanced by the reduced mean wind shear (satisfying the energy budget), which causes the equivalent surface roughness to increase. Interestingly, there is a small region farther above where the turbulent stress, dissipation rate, and mean wind shear are all enhanced. The observed strong correlation between the turbulent stress and the dissipation rate suggests that existing turbulence closure models that parameterize the latter based on the former are reasonably accurate.
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Dalrymple, Robert A., und James T. Kirby. „Models for very wide-angle water waves and wave diffraction“. Journal of Fluid Mechanics 192 (Juli 1988): 33–50. http://dx.doi.org/10.1017/s0022112088001776.
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For a bathymetry consisting of parallel bottom contours, wide-angle parabolic models are developed to describe the diffraction of linear water waves. The first model, developed by operator correspondence, extends the validity of conventional forms of the parabolic model for wave angles up to 70° from the assumed wave direction. Through the use of Fourier decomposition, wave models valid to 90° are developed for three different lateral boundary conditions. By application, it is shown that the diffraction of waves through gaps or around structures is governed by the initial wave condition at the structure, which can be expanded into progressive and evanescent wave modes. Away from the structure, the wave field consists of only the progressive wave modes, which disperse according to their direction of propagation, the water depth and Snell's Law. Examples are shown for oblique waves through a gap, directional seas past a breakwater, a plane wave with varying crest amplitude, and finally for the diffraction of waves into a channel.
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Zhao, Xiangfeng, und Hui Huang. „Theoretical Analysis of a Simple Hyperbolic Metamaterial Wave Splitter“. Journal of Physics: Conference Series 2666, Nr. 1 (01.12.2023): 012024. http://dx.doi.org/10.1088/1742-6596/2666/1/012024.
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Abstract Wave splitter for TE and TM wave is critical components in the integrated optics. Current technologies mainly rely on two types of designs to separate TE and TM waves: directional coupler type and branch type, but these designs are generally complex. By exploring the transmission behavior of the waves in the hyperbolic metamaterial and the distinct dispersion relationships of TE and TM waves in these materials, we have designed a wave splitter with a simple structure. Under different parameter conditions, we can get the pure TE wave or pure TM wave in the transmission region. Furthermore, if the specific condition is satisfied, we can even get the pure TE wave in the reflection or transmission region and the pure TM wave in the other region at the same time. All theoretical analysis results have been verified by using COMSOL Multiphysics simulation software.
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Long, L. T., und J. S. Liow. „A transparent boundary for finite‐difference wave simulation“. GEOPHYSICS 55, Nr. 2 (Februar 1990): 201–8. http://dx.doi.org/10.1190/1.1442827.
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Transparent (or absorbing) boundaries can be used in finite‐difference wave simulation to reduce the size of the computational grid and to eliminate reflections from the edges. An efficient and accurate transparent boundary can be formulated by decomposing the elastic waves into dilatational and rotational strains. The wave motions for the strains at the boundary can then be approximated by a one‐way wave equation. The direction of propagation is determined at each grid point by the gradient. This transparent boundary condition eliminates artificial reflections for a wave arriving at any angle of incidence and reduces the error to the level of precision of the finite‐difference approximation. Application of this transparent boundary condition is restricted to a medium that is homogeneous at the boundary to assure full separation of P waves from S waves. Also, interfering waves that generate phase velocities significantly greater than the assumed group velocity introduce errors. An example of the transparent boundary condition shows that it is a significant improvement over the A1 boundary condition of Clayton and Engquist.
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Sim, Woo Jeong, Hyun-Doug Yoon, Weon Mu Jeong und Kyong-ho Ryu. „OBSERVATION OF WAVE SPECTRUM UNDER TYPHOON CONDITION“. Coastal Engineering Proceedings, Nr. 35 (23.06.2017): 10. http://dx.doi.org/10.9753/icce.v35.waves.10.
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The spatial and temporal variation of wave spectrum under typhoon SANBA, which was the 16th typhoon originating in the northwestern Pacific Ocean in 2012, was examined. The typhoon SANBA passed through the middle of Korean peninsula whereas most of typhoons passed the Straits of Korea (eastern side of Korean peninsula). This unique path of typhoon SANBA provided interesting features of wave conditions. It was believed that wave heights were larger in the right side of the typhoon path because typhoons translation speed and rotational wind field were in the same direction (i.e., dangerous semicircle). However, observational evidence of wave spectrum under typhoon was still rare because of the difficulty in measurement. In this study, wave spectrum analysis under extreme storm condition of typhoon SANBA is given for the left and right sides of the path, including the information of significant wave height, peak period, and dominant wave direction. Wave measurements were obtained by directional wave rider buoys installed at Yeosu and Namhyeongjedo in Korea. Yeosu and Namhyeongjedo are located in each of the left and right of the path of the typhoon SANBA. The measurements provided distinguished wave conditions in each side of navigable semicircle and dangerous semicircle of the typhoon. Therefore it is possible to observe the spatial differences of the wave spectrum across the path of the typhoon, as well as temporal changes of wave spectrum as the typhoon evolves.
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Cha, Louis Dongbing, und Arick Shao. „Global stability of traveling waves for (1 + 1)-dimensional systems of quasilinear wave equations“. Journal of Hyperbolic Differential Equations 19, Nr. 04 (Dezember 2022): 549–86. http://dx.doi.org/10.1142/s0219891622500163.
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A key feature of [Formula: see text]-dimensional nonlinear wave equations is that they admit left or right traveling waves, under appropriate algebraic conditions on the nonlinearities. In this paper, we prove global stability of such traveling wave solutions for [Formula: see text]-dimensional systems of nonlinear wave equations, given a certain asymptotic null condition and sufficient decay for the traveling wave. We first consider semilinear systems as a simpler model problem; we then proceed to treat more general quasilinear systems.
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Mundhra, Raksha, und P. N. Deka. „Instability of Ion Cyclotron Waves (ICWS) at the Expense of Lower Hybrid Drift Waves (LHDWS) Turbulence Energy“. East European Journal of Physics, Nr. 4 (02.12.2023): 54–65. http://dx.doi.org/10.26565/2312-4334-2023-4-06.
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Instability of ion cyclotron waves(ICWs) is investigated in presence of lower hybrid drift waves(LHDWs) turbulence. Plasma inhomogeneity in the Earth’s magnetopause region supports a range of low frequency drift wave turbulent fields due to gradients in density in different regions of the media. One of these drift phenomena is identified as lower hybrid drift waves (LHDWs) which satisfies resonant conditions ω − k · v = 0. We have considered a nonlinear wave-particle interaction model where the resonant wave that accelerates the particle in magnetopause may transfer its energy to ion cyclotron waves through a modulated field. In spite of the frequency gaps between the two waves, energy can be transferred nonlinearly to generate unstable ion cyclotron waves which always do not satisfy the resonant condition Ω−K · v ≠ 0 and the nonlinear scattering condition Ω − ω − (K − k) · v ̸= 0. Here, ω and Ω are frequencies of the resonant and the nonresonant waves respectively and k and K are the corresponding wave numbers. We have obtained a nonlinear dispersion relation for ion cyclotron waves(ICWs) in presence of lower hybrid drift waves(LHDWs)turbulence. The growth rate of the ion cyclotron waves using space observational data in the magnetopause region has been estimated.
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ZHU, QIANG, YUMING LIU und DICK K. P. YUE. „Resonant interactions between Kelvin ship waves and ambient waves“. Journal of Fluid Mechanics 597 (01.02.2008): 171–97. http://dx.doi.org/10.1017/s002211200700969x.
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We consider the nonlinear interactions between the steady Kelvin waves behind an advancing ship and an (unsteady) ambient wave. It is shown that, for moderately steep ship waves and/or ambient waves, third-order (quartet) resonant interaction among the two wave systems could occur, leading to the generation of a new propagating wave along a specific ray in the Kelvin wake. The wave vector of the generated wave as well as the angle of the resonance ray are determined by the resonance condition and are functions of the ship forward speed and the wave vector of the ambient wave. To understand the resonance mechanism and the characteristics of the generated wave, we perform theoretical analyses of this problem using two related approaches. To obtain a relatively simple model in the form of a nonlinear Schrödinger (NLS) equation for the evolution of the resonant wave, we first consider a multiple-scale approach assuming locally discrete Kelvin wave components, with constant wave vectors but varying amplitudes along the resonance ray. This NLS model captures the key resonance mechanism but does not account for the detuning effect associated with the wave vector variation of Kevin waves in the neighbourhood of the resonance ray. To obtain the full quantitative features and evolution characteristics, we also consider a more complete model based on Zakharov's integral equation applied in the context of a continuous wave vector spectrum. The resulting evolution equation can be reduced to an NLS form with, however, cross-ray variable coefficients, on imposing a narrow-band assumption valid in the neighbourhood of the resonance ray. As expected, the two models compare well when wave vector detuning is small, in the near wake close to the ray. To verify the analyses, direct high-resolution simulations of the nonlinear wave interaction problem are obtained using a high-order spectral method. The simulations capture the salient features of the resonance in the near wake of the ship, with good agreements with theory for the location of the resonance and the growth rate of the generated wave.
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Lee, Young Hak, und Taekeun Oh. „The Measurement of P-, S-, and R-Wave Velocities to Evaluate the Condition of Reinforced and Prestressed Concrete Slabs“. Advances in Materials Science and Engineering 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/1548215.
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The traditional P-wave ultrasonic measurement has been used for the condition assessment of general reinforced concrete structures for a long time, but the effects of prestressing applied to concrete structures such as long-span buildings and bridges on ultrasonic pulse velocity have not been studied clearly. Therefore, this study analyzed the statistical distribution of P-wave ultrasonic pulse velocities in reinforced and prestressed concrete slabs of 3000 × 3000 mm with a thickness of 250 mm. In addition, we measured S- and R-waves to identify experimental consistency by statistical analysis using the Kolmogorov-Smirnov goodness-of-fit test. The experimental results show that the P-, S-, and R-wave velocities increased slightly (2-3%) when prestressing was applied. As expected, the S- and R-wave measurements show better statistical reliability and potential for in situ evaluation than the P-wave because they are less sensitive to confinement and boundary conditions. The experimental results in this study can be used when assessing the condition of prestressed concrete structures through the velocities of elastic waves.
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Jung, Jae-Sang, und Changhoon Lee. „Development of Analytical Solutions on Velocities of Regular Waves Generated by Bottom Wave Makers in a Flume“. Journal of Korean Society of Coastal and Ocean Engineers 34, Nr. 3 (30.06.2022): 58–71. http://dx.doi.org/10.9765/kscoe.2022.34.3.58.
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Analytical solutions for two-dimensional velocities of regular waves generated by bottom wave makers in a flume were derived in this study. Triangular and rectangular bottom wave makers were adopted. The velocity potential was derived based on the linear wave theory with the bottom moving boundary condition, kinematic and dynamic free surface boundary conditions. Then, analytical solutions of two-dimensional particle velocities were derived from the velocity potential. The velocity potential and two-dimensional particle velocities which were derived as complex integral equations were numerically calculated. The solutions showed physically valid results as velocities of regular waves generated by bottom wave makers in a flume.
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Yang, C., und R. C. Ertekin. „Numerical Simulation of Nonlinear Wave Diffraction by a Vertical Cylinder“. Journal of Offshore Mechanics and Arctic Engineering 114, Nr. 1 (01.02.1992): 36–44. http://dx.doi.org/10.1115/1.2919950.
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A three-dimensional time domain approach is used to study nonlinear wave diffraction by a fixed, vertical circular-cylinder that extends to the sea floor. In this approach, the development of the flow can be obtained by a time-stepping procedure, in which the velocity potential of the flow at any instant of time is obtained by the boundary-element method. In the numerical calculations, the exact body-boundary condition is satisfied on the instantaneous wetted surface of the cylinder, and an extended Sommerfeld condition is developed and used as the numerical radiation condition. The fourth-order Adams-Bashford method is employed in the time stepping scheme. Calculations are done to obtain the nonlinear diffraction of solitary waves and Stokes second-order waves by a vertical circular-cylinder. Numerical results are compared with the available linear and second-order wave-force predictions for some given wave height and wavelength conditions, and also with experimental data. Present horizontal force results agree better with the experimental data than the previous predictions.
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Jiang, Ting, Fan Wang, Xin-ying Li und Xiao-long Zheng. „Research on Wind Wave Simulation Technology based on Potential Flow Theory“. Journal of Physics: Conference Series 2381, Nr. 1 (01.12.2022): 012003. http://dx.doi.org/10.1088/1742-6596/2381/1/012003.
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Abstract The wave environment is the main service environment of surface aircraft in the process of surface duty. In order to comprehensively study the operating characteristics of aircraft under this condition, it is necessary to conduct research on wave parameter modeling methods and simulation technology based on different wave conditions. This paper adopts the three-dimensional potential theory and ball model to calculate the different wave cases. A high-precision numerical simulation method of complex sea conditions is formed by mastering the numerical wave-making technology of typical regular and irregular waves. The result shows that the regular simulation in this paper has a high precision that the wave height and period is in 1% error compared with theory. The calculation error of spectral peak and peak frequency of sea states at all levels are within ± 8%, and the simulation quality of irregular waves meets the calculation requirements.
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Dudko, Olga V., und Alexandr A. Mantsybora. „Shock Loading of Heteromodular Elastic Materials under Plane-Strain Condition“. Key Engineering Materials 887 (Mai 2021): 634–39. http://dx.doi.org/10.4028/www.scientific.net/kem.887.634.
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The paper discusses the results of mathematical modeling the two-dimensional nonlinear dynamics of heteromodular elastic materials. The resistance of these materials under tension and compression is various. The deformation properties of the heteromodular medium are described within the framework of the isotropic elasticity theory with stress-dependent elastic moduli. In the plane strain case, it is shown that only two types of the nonlinear deformation waves can appear in the heteromodular elastic materials: a plane-polarized quasi-longitudinal wave and a plane-polarized quasi-transverse wave. Basing on obtained properties of the plane shock waves, two plane self-similar boundary value problems are formulated and solved.
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Wang, Shu-qi, Ying Zhang, Yang-yang Xie, Gang Xu, Kun Liu und Yuan Zheng. „Hydrodynamic Analysis of Horizontal Axis Tidal Current Turbine under the Wave-Current Condition“. Journal of Marine Science and Engineering 8, Nr. 8 (26.07.2020): 562. http://dx.doi.org/10.3390/jmse8080562.
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To take advantage of the high tidal current velocity near the free surface, the horizontal axis turbine is installed, which inevitably causes hydrodynamic characteristics to effect the turbine by the waves. In this article, we established a numerical calculation method for the hydrodynamic load of a horizontal axis turbine under wave-current conditions. Based on the numerical calculation results, the hydrodynamic loads were decomposed and the influence rules of wave parameters and blade tip immersion depth on the hydrodynamic load were obtained. The study found the following: (1) the multi-frequency fluctuations based on the rotation frequency and incident wave frequency occurred in instantaneous values of the axial load coefficients and energy utilization ratios, and the fluctuation amplitude decreased with the increase of the blade tip immersion depth; (2) the fluctuation amplitude, according to rotation frequency, changed less with the increase of wave period and wave height, and was smaller according to wave frequency; (3) the fluctuation amplitude based on wave frequency increased linearly with the increase of wave height and wave period. The research results can provide the basis and reference for the design and engineering application of tidal current power station.
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Zhi-Fu, Li, Shi YuYun, Ren HuiLonga, Li Hui und Muhammad Aqeel Ashraf. „Simulation of Irregular Waves in a Numerical Wave Tank“. Polish Maritime Research 22, s1 (01.09.2015): 21–25. http://dx.doi.org/10.1515/pomr-2015-0027.
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Abstract The time domain boundary element method was utilized to simulate the propagation of the irregular waves in a numerical wave tank. The problem was solved in a time-marching scheme, upon the irregular waves being fed through the inflow boundary, in which the theoretical solution was obtained from the wave energy spectrum. The open boundary condition was modeled by the multi transmitting formula (MTF), in which the phase velocity was calculated according to the Sommerfeld’s condition. The velocity potential and wave elevation were directly obtained by integrating the free surface condition twice, with respect to time. The accuracy of the developed numerical scheme was verified by simulating the propagation of irregular waves. The numerical results show good agreements with the analytical solutions, which prove that the proposed scheme is a promising way to the simulation of wave-body interactions.
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Hamada, Tokuichi. „THE SURFACE WAVE IN A TWO-DIMENSIONAL VORTEX LAYER“. Coastal Engineering Proceedings 1, Nr. 8 (29.01.2011): 3. http://dx.doi.org/10.9753/icce.v8.3.
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Progressive surface wave in a two-dimensional vortex layer is theoretically treated. Dynamical equations and free surface conditions are shown by using the two-dimensional stream functions of wave and vortex.
Then the perturbation equations are given by assuming that the ratio of length scale of vortices and wave is fairly small. The first approximate solution of wave has a usual form of an irrotational progressive wave. Vortices are assumed to be steady and to have simplified Fourier-
Stleltjes form. Then the interaction of this primary wave and the vortices are examined. To satisfy the free surface condition of the second order, existent waves are formed.
In the second order term of the free surface elevation, these secondary waves offset the effect of the above mentioned interaction, and so the surface profile of the primary wave is not altered by the existence of inner vortices of high frequency. Some pictures of Irregular surface waves in a turbulent flow are shown to verify this property.
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Wiciak, Piotr, Giovanni Cascante und Maria Anna Polak. „Laser vibrometer condition assessment of cemented materials using wavelet synchro-squeezed transform“. MATEC Web of Conferences 323 (2020): 01003. http://dx.doi.org/10.1051/matecconf/202032301003.
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Current non-destructive ultrasonic techniques (NDT) are based mostly on wave velocity analysis. While current techniques can identify severe damage, they fail to detect early deterioration. Therefore, the proposed method, based on the propagation of surface waves, takes into account not only changes in wave velocity but also changes in wave attenuation. In practical/field applications, access to a structure is often limited to one side only (i.e. concrete slabs, vacuum building walls). Thus, surface wave analysis is a natural solution. To improve the reliability of wave attenuation measurements, responses of ultrasonic transducers are measured using a high-frequency Doppler laser vibrometer. Firstly, the ultrasonic transducer is characterized using the laser vibrometer. Then, based on the sensitive frequency ranges, response signals measured for the cemented sand specimen are analyzed, and the relative attenuation index based on spectral energy is proposed. The method is further improved using the wavelet synchro-squeezed transform.
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Hwang, Paul A., Derek M. Burrage, David W. Wang und Joel C. Wesson. „Ocean Surface Roughness Spectrum in High Wind Condition for Microwave Backscatter and Emission Computations*“. Journal of Atmospheric and Oceanic Technology 30, Nr. 9 (01.09.2013): 2168–88. http://dx.doi.org/10.1175/jtech-d-12-00239.1.
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Abstract Ocean surface roughness plays an important role in air–sea interaction and ocean remote sensing. Its primary contribution is from surface waves much shorter than the energetic wave components near the peak of the wave energy spectrum. Field measurements of short-scale waves are scarce. In contrast, microwave remote sensing has produced a large volume of data useful for short-wave investigation. Particularly, Bragg resonance is the primary mechanism of radar backscatter from the ocean surface and the radar serves as a spectrometer of short surface waves. The roughness spectra inverted from radar backscatter measurements expand the short-wave database to high wind conditions in which in situ sensors do not function well. Using scatterometer geophysical model functions for L-, C-, and Ku-band microwave frequencies, the inverted roughness spectra, covering Bragg resonance wavelengths from 0.012 to 0.20 m, show a convergent trend in high winds. This convergent trend is incorporated in the surface roughness spectrum model to improve the applicable wind speed range for microwave scattering and emission computations.
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Li, J., und H. Huang. „Second-Order Radiation Condition of Scattering Wave and Its Application“. Journal of Offshore Mechanics and Arctic Engineering 112, Nr. 3 (01.08.1990): 177–80. http://dx.doi.org/10.1115/1.2919853.
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The first and second-order radiation conditions for scattering waves in two and three-dimensional problems have been derived by virtue of a sequence of linear differential operators. The wave forces on a large circular cylinder are computed by using finite element methods with first and second-order radiation conditions and the Sommerfeld condition, respectively. The results show that an improvement in accuracy is achieved by employing the second-order radiation condition. The interior region in which finite elements are employed can be restricted to a much smaller one, compared with that using the Sommerfeld condition and the computing efforts and required storage in the computer are reduced.
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Dally, William R., und Robert G. Dean. „CLOSED-FORM SOLUTIONS FOR THE PROBABILITY DENSITY OF WAVE HEIGHT IN THE SURF ZONE“. Coastal Engineering Proceedings 1, Nr. 21 (29.01.1988): 60. http://dx.doi.org/10.9753/icce.v21.60.
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By invoking the assumption that in the surf zone, random waves behave as a collection of individual regular waves, two closed-form solutions for the probability density function of wave height on planar beaches are derived. The first uses shallow water linear theory for wave shoaling, assumes a uniform incipient condition, and prescribes breaking with a regular wave model that includes both bottom slope and wave steepness effects on the rate of decay. In the second model, the shallow water assumption is removed, and a distribution in wave period (incipient condition) is included. Preliminary results indicate that the models exhibit much of the behavior noted for random wave transformation reported in the literature, including bottom slope and wave steepness effects on the shape of the probability density function.
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Hu, Xuan, Azhar Halik und Ahmadjan Muhammadhaji. „SPH Simulation of the Interaction between Freak Waves and Bottom-Fixed Structures“. Mathematics 11, Nr. 23 (30.11.2023): 4838. http://dx.doi.org/10.3390/math11234838.
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In this paper, the Smoothed Particle Hydrodynamics (SPH) method is used in a C# environment to simulate the interaction between freak waves and bottom-fixed structures by establishing a fluid dynamics model. Paraview software 5.10.1 was used to analyze and visualize the simulation results. In order to simulate wave propagation accurately, the reliability of the model was verified by comparing experimental and simulated data. A two-dimensional numerical wave flume was established based on the SPH method, a conservative Riemann solver was introduced, a repulsive boundary condition was adopted, and a slope was used to eliminate wave reflection. Bottom-fixed structures of different heights and lengths, as well as different wave conditions, were selected to numerically simulate the interaction between freak waves and bottom-fixed structures. The results show that the height of bottom-fixed structures and wave conditions have a significant effect on hindering the propagation of rogue waves, while the length has little effect on the propagation of deformed waves. When the amplitude of the wave remains constant, both the period andthe duration of the deformed wave are longer. This research is of certain significance for the prediction of freak waves in marine engineering and the application and promotion of SPH methods.