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Pan, Wenbo, Meng He i Cheng Cui. "Experimental Study on Hydrodynamic Characteristics of a Submerged Floating Tunnel under Freak Waves (I: Time-Domain Study)". Journal of Marine Science and Engineering 11, nr 5 (4.05.2023): 977. http://dx.doi.org/10.3390/jmse11050977.
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The dynamic response characteristics of a two-dimensional submerged floating tunnel (SFT) under random and freak waves were investigated in the present study. The results demonstrate that (1) the dynamic responses of the SFT under the freak wave are significantly larger than those under the largest wave in the wave train excluding the freak wave, particularly for the motion response. The maximum values of the motion responses induced by the freak wave were several times larger than those induced by the largest wave in the wave train excluding the freak wave, far exceeding the proportion of the corresponding wave height. (2) The freak wave parameter α1 has a significant effect on the amplification coefficients of surge, heave and pitch; all increase nonlinearly as α1 increases. Within α1 = 1.90~2.59, the amplification coefficients of the surge, heave and pitch vary in the ranges of 1.91~6.46, 1.53~3.87 and 1.73~5.32, respectively. (3) Amplification coefficients of tension increase almost linearly as α1 increases. Additionally, the amplification effect of the freak wave on the mooring tension is much smaller than that on motion responses. Within α1 = 1.90~2.59, the amplification coefficients of tension vary from 1.15 to 1.35. (4) Generalised amplification coefficients of motion responses increase as α1 increases and are all greater than 1.0, indicating that growth rates for motion responses under the freak wave exceed the growth rates for maximum wave height. Moreover, motion responses show a significantly nonlinear growth as maximum wave height increases. The generalised amplification coefficients of the mooring tension decrease as α1 increases, and are all less than 1.0, indicating that the dynamic amplification effect of the freak wave on the mooring tension is much smaller than that on motions. On the other hand, growth rates of the mooring tension under freak waves are smaller than the linear growth rate of the height of freak waves.
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Sanders, Ross H., Jane M. Cappaert i David L. Pease. "Wave Characteristics of Olympic Breaststroke Swimmers". Journal of Applied Biomechanics 14, nr 1 (luty 1998): 40–51. http://dx.doi.org/10.1123/jab.14.1.40.
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The purpose of this study was to investigate the wave characteristics of breaststroke swimming. Particular emphasis was accorded the question of whether modern breast-stroke is "flylike" (referring to the butterfly stroke) and whether "waves" travel along the body during the breaststroke cycle. Selected body landmarks and the center of mass (CM) of 8 Olympic breaststroke swimmers were quantified. Fourier analysis was conducted to determine the amplitude, frequency composition, and phase characteristics of the vertical undulations of the vertex of the head, shoulders, hips, knees, and ankles. The differences in phase between these landmarks for the first (HI) and second (H2) Fourier frequencies were investigated to establish whether body waves traveled in a caudal direction. While the motion of the upper body was somewhat flylike, the velocity of the HI wave from the hips to ankles was variable among subjects and, for all subjects, was too slow to be propulsive. Contrary to what one would expect, the range of vertical motion of the CM was inversely related to the range of hip vertical motion. The two highest placing subjects, based on preliminary heat times (SI and S4), were distinguished by a large range of hip vertical motion and a small range of CM vertical motion.
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Chen, Long Wei, Wei Ming Wang i Rui Sun. "Correlation of Site Characteristic Period with Predominant Period of Ground Acceleration by a Simplified Model". Applied Mechanics and Materials 238 (listopad 2012): 864–67. http://dx.doi.org/10.4028/www.scientific.net/amm.238.864.
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Site characteristic period is an important index in seismic zonantion and seismic resistance design. The characteristics of the ground motions are conceptually related with site characteristics. A simplified single-layer model is used for simulating horizontal strata under seismic loading to calibrate the correlation of site characteristic period with the predominant period of ground motion. The analytical results show that the inputted motions were amplified considerably by the site typically for the period components which were close to the site characteristic periods; with the shear wave velocity of the soil layer decreases with respect to the initial shear wave velocity, the predominant period of ground motion increases; the site characteristic periods are consistent with the predominant periods of the ground motion.
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Li, Chun Liu, i Yun Peng Zhao. "Motion Characteristics of Composite-Type Sea Cage under Pure Wave". Advanced Materials Research 490-495 (marzec 2012): 3405–9. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.3405.
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To study motion range changes with wave condition and motion relationship between cages, physical model experiments were carried out. The authors designed 2 models of composite-type sea cages. Experimental data obtained by the CCD data acquisition system. The experiment results showed that 1.in the same period, horizontal motion range,vertical motion range and inclination changes of float collar increase with wave height; 2.In the same wave height, horizontal motion range of the float collar increases with period; 3.The laws between vertical motion and period are not obvious 4.The laws between inclination changes and period are not obvious 5.Motion range of the first cage along the direction of waves is less than other cages.
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Lian, Jijian, Junni Jiang, Xiaofeng Dong, Haijun Wang, Huan Zhou i Pengwen Wang. "Coupled Motion Characteristics of Offshore Wind Turbines during the Integrated Transportation Process". Energies 12, nr 10 (27.05.2019): 2023. http://dx.doi.org/10.3390/en12102023.
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The offshore wind turbine (OWT) supported by bucket foundations can be installed in the integrated transportation process by a dedicated vessel. During the integrated transportation process, the wind turbine is considered as a coupling system with the transport ship, which is easily influenced by waves and storms. In view of the motion response and influential factors, the heave and rock stiffness of the entire floating system was proposed, and then the analytical dynamic motion model of the coupling system was established based on the movement mechanism of the traditional floating body in the wave in this paper. Subsequently, the rationality of the proposed motion model was verified based on the field observation data, with the maximum deviation of the motion responses less than 14%. Further, the influence on the heave and pitch motion of the coupling system considering different factors (vessel speed, wave height, wind speed and wave angle) and the factor sensitivity were discussed by the novel analytical model. It is explained that the heave and pitch motion responses rise with the increase of the wave height and wave angle. Simultaneously, the responses decrease as the vessel speed increases considering sailing along the waves. On the contrary, the responses show an obvious increasing trend with the increase of vessel speed in the case of the top wave sailing. In addition, it is also illustrated that the wave height has the greatest influence on the heave and pitch motion responses, followed by the vessel speed. The wave angle has the lowest sensitivity when the heave and pitch motion are far away from its harmonic resonance region.
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Chen, Gong Lian, Wen Zheng Lu, Lei Wang i Qi Wu. "Study on Far-Field Ground Motion Characteristics". Applied Mechanics and Materials 438-439 (październik 2013): 1471–73. http://dx.doi.org/10.4028/www.scientific.net/amm.438-439.1471.
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In order to study the far-field ground motion characteristics and the attenuation of seismic waves, the peak ground acceleration (velocity, displacement), time of duration and response spectrum of the seismic waves were analyzed in this paper. Through the investigation of earthquake wave propagation process, the seismic attenuation low was analyzed. This study can provide technical support for the seismic design of long period structures and related engineering application.
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Huang, Zhi-Xun. "Negative Velocity Characteristics in Electromagnetism". Physical Science International Journal 27, nr 1 (13.05.2023): 25–53. http://dx.doi.org/10.9734/psij/2023/v27i1776.
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Newton mechanics is great, Newton's contribution is indelible. But from Newton's classical mechanics, the definition of velocity (=) must mean that this physical parameter is a vector, so "negative velocity" only means the opposite direction of motion, no other meaning. It is difficult to understand negative velocity within the framework of classical mechanics. However, wave is a special form of material motion, wave mechanics has a unique method and meaning, and its concept and connotation are significantly different from classical mechanics. For example, wave velocity (whether phase velocity or group velocity) is a scalar quantity. "Negative wave velocity" does not mean that the direction of motion is reversed, but a special phenomenon that does not accord with causality from the surface view. In any case, research in recent decades has shown that negative wave velocity is not only theoretically possible, it has also been repeatedly shown to exist experimentally. Moreover, negative wave velocity is a special form of superluminal speed; The wave with negative velocity is the advanced wave. It corresponds to the leading solution of the basic equation of electromagnetic field and electromagnetic wave. The past practice (discarding the advanced solution) is wrong! As for causality, scientists have provided a new definition and interpretation. In short, both wave mechanics and quantum optics take a different approach from classical mechanics.
This paper points out that it is unusual for the 2022 Nobel Prize in Physics to be awarded to Alain Aspect and two others, since Aspect's experiments on the Bell inequality were completed in 1982, Which still stands today as a crucial experiment that proved Einstein's EPR paper wrong and quantum mechanics (QM) correct. Aspect's award in 2022 showed that mainstream physical community had been forced to accept that quantum entanglement existed and that the "light-speed limit" theory of SR was a mistake.
This paper discusses the proposition "negative characteristic motion of electromagnetic wave" put forward by the author in 2013, pointing out that it is an inherent physical phenomenon reflecting symmetry in nature. In this paper, the faster-than-light motion of waves found in the near-field of antennas is discussed. In addition, the realizability of "time travel" is also discussed.
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N.M., Khairuddin,, Jaswar Koto, Nur Ain, A.R., Mohd Azhari , J. i Najmie, A. "Experimental Study on Translation Motion Characteristics of Moored Symmetrical Semi-submersible in Regular Waves". Journal of Mechanical Engineering 17, nr 1 (1.04.2020): 77–89. http://dx.doi.org/10.24191/jmeche.v17i1.15220.
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This paper proposes to carry out experiment procedures to investigate the translation motion characteristics of symmetrical semi-submersibles in long crest regular waves. The hydrodynamic response of floating structures in waves is required to be modelled correctly to ensure stability and safety. The symmetrical semi-submersible model was constructed based on a scale ratio of 1:81 in this experiment and was installed with horizontal mooring lines in a wave dynamic basin. This paper also discusses the model preparation procedures, including the mooring lines setup, instrument setup and experiment setup, before conducting the experiment. According to the experiment data, the symmetrical moored semi-submersible experienced wave frequency motion and slow varying motion due to drift force and mooring lines for sway motion; while the heave and surge motion only experienced wave frequency motion.
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Wang, Y. Z. "Motion and stability of caisson breakwaters under breaking wave impact". Canadian Journal of Civil Engineering 28, nr 6 (1.12.2001): 960–68. http://dx.doi.org/10.1139/l01-040.
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The possible motions of caisson breakwaters under dynamic load excitation include vibrating motion, vibratingsliding motion, and vibratingrocking motion. Three models are presented in this paper and are used to simulate the histories of vibratingslidingrocking motions of caissons under breaking wave impact. The effect of the dynamic characteristics of the caissonfoundation system and the motions on the displacement, rotation, sliding force, and overturning moment of caissons are investigated. It is shown that the sliding force of the caisson is different from the breaking wave force directly acting on the caisson due to the motion of the caisson and the sliding motion or rocking motion of the caisson can limit the sliding force or overturning moment of the caisson to a certain value. The sliding force never exceeds the friction force between the caisson and the foundation, and the overturning moment never exceeds the stability moment of the caisson. It is concluded that the wave conditions, the dynamic characteristics, and the motions of the caissonfoundation system should be considered in design.Key words: caisson breakwater, breaking wave, vibrating, sliding, rocking.
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Katafuchi, Masaki, Hideyuki Suzuki, Yuya Higuchi, Hidetaka Houtani, Edgard B. Malta i Rodolfo T. Gonçalves. "Wave Response of a Monocolumn Platform with a Skirt Using CFD and Experimental Approaches". Journal of Marine Science and Engineering 10, nr 9 (9.09.2022): 1276. http://dx.doi.org/10.3390/jmse10091276.
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This paper aims to investigate the nonlinear motion characteristics of a monocolumn type floater with skirts numerically and experimentally. Wave calibration, free decay, and regular wave tests were simulated using a computational fluid dynamics (CFD) code OpenFOAM. The experiments were carried out in a wave tank to validate the CFD results. First, wave calibration tests were performed to investigate wave generation, development, propagation, and absorption in the numerical wave tank. Second, the simulation input parameters were calibrated to reproduce the waves generated in the tank experiment. Third, free decay tests of heave and pitch were conducted to examine the natural period and the linear and quadratic damping of the floater. A verification and validation study was performed using experimental data for free decay tests. Finally, regular wave tests were performed to investigate the motion characteristics of the floater. The results were processed to obtain the response amplitude operator (RAO) for the heave and pitch motions. The RAOs of the floater was compared with the experimental data and numerical simulations based on the linear potential theory code WAMIT to investigate the performance of the CFD simulations. The comparisons made in this work showed the potential of the CFD method to reproduce the motion characteristics of a shallow-draft floating object with a skirt in waves and to visualize the nonlinear phenomena behind the oscillation of the floating object.
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Song, Xuemin, Jianxi Yao, Weiqin Liu, Yaqing Shu i Feng Xu. "Numerical Generation of Solitary Wave and Its Propagation Characteristics in a Step-Type Flume". Journal of Marine Science and Engineering 11, nr 1 (27.12.2022): 35. http://dx.doi.org/10.3390/jmse11010035.
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This work concerns the numerical generation of stable solitary waves by using a piston-type wave maker and the propagation characteristics of a solitary wave in a step-type flume. The numerical generation of solitary waves was performed by solving N-S (Navier–Stokes) equations on the open source CFD (computational fluid dynamics) platform OpenFOAM. To this end, a new module of dynamic boundary conditions was programmed and can be applied to prescribe the horizontal linear motion of a paddle. Two kinds of paddle motions, based on both the first-order and ninth-order solutions of solitary waves, were first determined. The time history of paddle motion was restored in a file, which was then used as an input for the virtual wave maker. The solitary wave in water with a constant depth was generated by both numerical simulation and experiment in the wave flume installed with a piston wave maker. The results show that the amplitudes of trailing waves based on the first-order solution are larger than those based on the ninth-order solution and that wave height based on the first-order solution decays more quickly. The numerical wave profiles are in good agreement with the experimental ones. The propagation characteristics of a solitary wave in a step-type flume was numerically investigated as well. It was found that a part of the solitary wave is reflected when the solitary wave passes the step due to blockage effects, and the forward main wave collapses quickly when it enters shallow water. This work presents a very successful numerical study of stable solitary wave generation and reveals the phenomena when a solitary wave propagates in a step-type flume.
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Suneela, Jangam, i Prasanta Sahoo. "NUMERICAL INVESTIGATION OF INTERCEPTOR EFFECT ON SEA KEEPING BEHAVIOUR OF PLANING HULL ADVANCING IN REGULAR HEAD WAVES". Brodogradnja 72, nr 2 (1.04.2021): 73–92. http://dx.doi.org/10.21278/brod72205.
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In this paper an attempt has been made to assess the capability of numerical algorithm based on Reynolds Averaged Navier Stokes (RANS) for predicting the motion characteristics of the planing hull in calm water and regular waves. The focus of the present study is the impact of interceptors on the sea keeping quality of a planing vessel investigated through the application of numerical methods. The wave properties such as wavelength and wave height are taken into consideration to investigate the effect of wave steepness on vessel response. It is found that numerical data can efficiently simulate the motion attitude and the hydrodynamic characteristics of planing craft in regular head waves. The planing hull with and without interceptor fitted at the transom is simulated in numerical wave tank. The results show reduction in heave and pitch motions which gave favorable sea keeping behavior for the hull fitted with interceptor. The numerical solution is useful for the preliminary prediction of navigation safety during sailing.
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Raghukumar, Kaustubha, Grace Chang, Frank Spada, Craig Jones, Tim Janssen i Andrew Gans. "Performance Characteristics of “Spotter,” a Newly Developed Real-Time Wave Measurement Buoy". Journal of Atmospheric and Oceanic Technology 36, nr 6 (czerwiec 2019): 1127–41. http://dx.doi.org/10.1175/jtech-d-18-0151.1.
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AbstractThe Spotter is a low-cost, real-time, solar-powered wave measurement buoy that was recently developed by Spoondrift Technologies, Inc. (Spoondrift). To evaluate the data quality of the Spotter device, we performed a series of validation experiments that included comparisons between Spotter-derived motions and prescribed wave motions (monochromatic and random waves) on a custom-built, motion-controlled validation stand and simultaneous in-water measurements using a conventional wave measurement buoy, the Datawell DWR-G4 (Datawell). Spotter evaluations included time-domain validation (i.e., wave by wave) and comparisons of wave spectra, directional moments, and bulk statistical parameters such as significant wave height, peak period, mean wave direction, and directional spread. Spotter wave measurements show excellent fidelity and lend a high degree of confidence in data quality. Overall, Spotter-derived bulk statistical parameters were within 10% of respective Datawell-derived quantities. The Spotter’s low cost and compact form factor enabled unique field deployments of multiple wave measurement buoys for direct measurements of wave characteristics such as ocean wave decorrelation length scales, wave speed, and directional spread. Wave decorrelation lengths were found to be inversely proportional to the width of the spectrum, and wave speeds compared well against linear wave theory.
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Wang, Long, Zheng-quan Yang, Jian-ming Zhao, Xiao-sheng Liu i Yan-feng Wen. "Transmitting Characteristics of Seismic Motion in Super-Deep Overburden Layer Ground". Shock and Vibration 2021 (27.02.2021): 1–23. http://dx.doi.org/10.1155/2021/8898012.
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Dynamic response characteristics and antiseismic performance of the structures which were constructed on the super-deep overburden layer are affected obviously by the seismic motion characteristics of the super-deep overburden layer foundation. In this paper, the seismic motion characteristics of horizontally stratified super-deep overburdenIn this paper, the seismic motion characteristics of horizontally stratified super-deep overburden based on the research results of on-site in situ tests and indoor material property tests, the horizontal shear layer method that can consider the nonlinear characteristics of dynamic soil deformation and the characteristics of seismic wave propagation in the soil is used to study the characteristics of ground motions of super-deep and thick overburden level of an earth-rock dam in China. The influence law of input ground motion characteristics and input ground motion position on seismic response analysis results of overburden ground is studied. Taking the uniform overburden layer model as an example, the coupling influence analysis of soil layer thickness and shear velocity on ground motion response are carried out, and the coupling influence law is proposed. The study shows that the seismic motion propagating characteristics of the earthquake in super-deep overburden layer is involved, inputting location of the seismic motion affects the results of ground seismic response greatly; super-deep overburden layer thickness and the soil shear wave velocity on influence law of ground motion characteristics have coupling. When the shear wave velocity of the soil layer is constant, the surface acceleration response has an inflection point with the change of the soil layer thickness; when the thickness of overburden is constant, the surface acceleration response also has an inflection point with the change of shear wave velocity of the soil layer; these inflexion values are influenced by both soil thickness and shear wave velocity.
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Wang, Hsin-Erh, i I.-Chi Chan. "Numerical Investigation of Wave Generation Characteristics of Bottom-Tilting Flume Wavemaker". Journal of Marine Science and Engineering 8, nr 10 (30.09.2020): 769. http://dx.doi.org/10.3390/jmse8100769.
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Motivated by the recently developed bottom-tilting wavemaker specially designed for tsunami research, we propose to investigate numerically the wave generation mechanism of this new wave generator. A series of numerical experiments is carried out using a RANS-based computer model to evaluate the effects of wavemaker length, bottom displacement, motion duration, and water depth on the wavelength, wave amplitude, phase speed, and waveform of the leading waves produced by the bottom-motion wave generator. Numerical results fit well with the existing laboratory data. Explicit equations for the wavelength and wave amplitude are developed and can serve as the guideline for wave generation. Encouraging results suggest that bottom-tilting wavemaker is a good alternative to the traditional piston-type wavemaker for tsunami research.
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Yang, Zhiwen, Jinzhao Li, Huaqing Zhang, Chunguang Yuan i Hua Yang. "Experimental Study on 2D Motion Characteristics of Submerged Floating Tunnel in Waves". Journal of Marine Science and Engineering 8, nr 2 (15.02.2020): 123. http://dx.doi.org/10.3390/jmse8020123.
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Submerged floating tunnel (SFT) is a new type of transportation infrastructure for crossing sea straits in relatively deeper water. Compared with the fixed tunnel, the main challenge in designing a SFT is the stability maintaining in a complex hydrodynamic environment, especially for the wave-induced dynamic load. In this study, a series of systematic experiments were conducted to investigate the 2D motion characteristics (i.e., heave, sway and roll) of the SFT exposed to regular waves. The movement of the SFT model is measured by the image processing method which is a noncontact measurement. The experimental observation of SFT motion during the process of wave and SFT interaction is described in detail, and the influence of several governing parameters is thoroughly analyzed, including the wave height and period, submergence depth, buoyancy to weight ratio (BWR), and the mooring line angle. The results show that the motion amplitudes of SFT increase with the wave height increasing. The effect of wave period is related to the natural period of the structure. The sway, heave and roll of the SFT submerged beneath the water surface are much smaller than that of the SFT on the water surface. With the increase of BWR, the motion of SFT decreases. The motion amplitude increases with mooring line angle increasing. Finally, empirical equations are proposed to estimate the motion characteristics of the SFT.
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Zhuang, Yuan, i Decheng Wan. "Numerical Study on Ship Motion Fully Coupled with LNG Tank Sloshing in CFD Method". International Journal of Computational Methods 16, nr 06 (27.05.2019): 1840022. http://dx.doi.org/10.1142/s0219876218400224.
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In this paper, numerical simulations of ship motion coupled with LNG tank sloshing in waves are considered. The fully coupled problems are performed by our in-house RANS/DES solver, naoe-FOAM-SJTU. The internal tank sloshing and external wave flow are solved simultaneously. The considered model is a three-dimensional simplified LNG FPSO with two prismatic tanks. The ship motion responses are carried out in beam waves to compare with existing experimental data to validate this solver. The coupling effects between ship motion and sloshing tanks are observed. The anti-rolling characteristics are found, and this kind of characteristic is obvious in low-filling conditions. Different incident wave amplitudes and frequencies are considered. When the incident wave frequency is close to ship motion natural frequency, the ship motion response is strong and an overturning behavior in sloshing tanks is observed. Meanwhile, impact pressures on bulkhead are also discussed. The pressure signal explains the phenomenon in tanks we discussed before.
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Xu, Xiaoqiu, Zhongwen Wang, Junwei Han i Dacheng Cong. "Shock Wave Characteristics of Hydraulic Shock Wave Simulator with Variable Damping". Mathematical Problems in Engineering 2018 (30.12.2018): 1–12. http://dx.doi.org/10.1155/2018/8359145.
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For simulating the shock wave with high peak force in a short duration, a novel variable damping hydraulic shock wave simulator was developed, and it was used for simulating the cannon recoil motion. The working principle of this simulator was explained with the assistance of established mathematical model and the flow behavior in damping channel was analyzed. The shock wave characteristics curves were obtained by using the numerical computation method. The results showed that the shock wave characteristics were directly related to the sectional area of the damping channel and the damping fluid medium characteristic; the shock wave curve can be simulated by adjusting the variable damping parameters. The computational results agreed well with the theory analysis, which meant that the proposed mathematical model can be used for supplying theoretical references for the cannon recoil motion in artillery fire shock simulation test.
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Yang, Xin Dong, Zuo Chao Wang, Ai Guo Shi, Bo Liu i Li Li. "Research on Ship Swaying Motion Prediction Based on Multi-Variable Chaotic Time Series Analysis". Advanced Materials Research 712-715 (czerwiec 2013): 1550–54. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.1550.
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Wind and waves have particularly significant influence upon exertion of naval vessels battle effectiveness. It is urgently necessary to improve the ability of the Navy to carry out combat service in severe sea state normally. This paper aims to obtain the accurate prediction of ship motions with second level predictable time in real waves. According to the characteristics of the ship motion, the research on extremely short-time prediction of ship motion has been carried out based on multi-variable chaotic time series analysis, and the effectiveness of the prediction of ship motion in real wave is highly improved.
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Suzuki, Hideyuki, Yuta Sakai, Yasuo Yoshimura, Hidetaka Houtani, Lucas H. S. Carmo, Haruki Yoshimoto, Ken Kamizawa i Rodolfo T. Gonçalves. "Non-Linear Motion Characteristics of a Shallow Draft Cylindrical Barge Type Floater for a FOWT in Waves". Journal of Marine Science and Engineering 9, nr 1 (6.01.2021): 56. http://dx.doi.org/10.3390/jmse9010056.
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A shallow draft cylindrical barge type floater with footing close to the water surface was experimentally evaluated in waves to investigate non-linear motion characteristics. The floater was designed to be used as an option for FOWT—floating offshore wind turbines. The non-linear mechanism can be promoted due to the viscous force that acts on the footing edges and the footing interaction with the free surface. In general, the observed non-linear viscous damping is modeled as a force proportional to the square of the relative velocity between the floater and the water. Therefore, the viscous damping levels is expected to increase, and the response in waves, to decrease. However, an increase in motion responses was observed for a broad range of wave periods. An attempt was made to clarify the hydrodynamic mechanism by comparing wave tank experiments, numerical calculations by CFD—computational fluid dynamics codes, and linear potential theory codes. Regular wave tests for three different wave height conditions were carried out, including free decay tests in still waters. For CFD simulations, the OpenFOAM code was selected. For potential theory simulations, the WAMIT code was chosen. As a result of the research, three points could be highlighted and discussed: first, the hydrodynamic phenomenon that contributed to the non-linear motion of the floater was identified; second, the increase and coupling of the motions response of heave and pitch motions; and finally, the phenomenon that the footing held water mass and lifted it to the water surface. The CFD calculations were able to get good qualitative results compared with the experiments and confirmed the use of CFD as a useful tool to capture the non-linear hydrodynamic phenomenon. The linear potential theory was not able to capture the phenomenon discussed herein.
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Shih, Ruey Syan. "Numerical Study of the Characteristics of Wave-Wave Interactions in Multiphase Wave Field Near Coastal Area". Advanced Materials Research 255-260 (maj 2011): 2313–17. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.2313.
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Numerical investigations of multiphase irregular wave field are presented by using the BEM, which incorporates the interaction between incoming wave and reflected wave in the coastal area. This study discusses the case of multi-component wave generation using the 2D-NWT, which incorporates the wave-wave interactions between various conditions of incoming waves and high frequency reflected waves, including the variation of wave field and particle trajectory. The surf beats in the surf zone is mainly the cause of the cross-shore motion, and the generations of high frequency harmonics waves, these phenomena will be study accordingly in this preliminary study for the modeling of oscillations cause by surf beat and back swash, the generation of high frequency multi-phase reflected wave are carried out to investigate the deformation of wave profile, wave field and particle path-line.
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Das, S. N., i S. K. Das. "Determination of coupled sway, roll, and yaw motions of a floating body in regular waves". International Journal of Mathematics and Mathematical Sciences 2004, nr 41 (2004): 2181–97. http://dx.doi.org/10.1155/s0161171204305363.
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This paper investigates the motion response of a floating body in time domain under the influence of small amplitude regular waves. The governing equations of motion describing the balance of wave-exciting force with the inertial, damping, and restoring forces are transformed into frequency domain by applying Laplace transform technique. Assuming the floating body is initially at rest and the waves act perpendicular to the vessel of lateral symmetry, hydrodynamic coefficients were obtained in terms of integrated sectional added-mass, damping, and restoring coefficients, derived from Frank's close-fit curve. A numerical experiment on a vessel of19190ton displaced mass was carried out for three different wave frequencies, namely,0.56rad/s,0.74rad/s, and1.24rad/s. The damping parameters (ςi) reveal the system stability criteria, derived from the quartic analysis, corresponding to the undamped frequencies (βi). It is observed that the sway and yaw motions become maximum for frequency0.56rad/s, whereas roll motion is maximum for frequency0.74rad/s. All three motions show harmonic behavior and attain dynamic equilibrium for timet>100seconds. The mathematical approach presented here will be useful to determine seaworthiness characteristics of any vessel when wave amplitudes are small and also to validate complex numerical models.
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Cui, Jian, Ralf Bachmayer, Brad deYoung i Weimin Huang. "Ocean Wave Measurement Using Short-Range K-Band Narrow Beam Continuous Wave Radar". Remote Sensing 10, nr 8 (7.08.2018): 1242. http://dx.doi.org/10.3390/rs10081242.
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We describe a technique to measure ocean wave period, height and direction. The technique is based on the characteristics of transmission and backscattering of short-range K-band narrow beam continuous wave radar at the sea surface. The short-range K-band radar transmits and receives continuous signals close to the sea surface at a low-grazing angle. By sensing the motions of a dominant facet at the sea surface that strongly scatters signals back and is located directly in front of the radar, the wave orbital velocity can be measured from the Doppler shift of the received radar signal. The period, height and direction of ocean wave are determined from the relationships among wave orbital velocity, ocean wave characteristics and the Doppler shift. Numerical simulations were performed to validate that the dominant facet exists and ocean waves are measured by sensing its motion. Validation experiments were conducted in a wave tank to verify the feasibility of the proposed ocean wave measurement method. The results of simulations and experiments demonstrate the effectiveness of the short-range K-band narrow beam continuous wave radar for the measurement of ocean waves.
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Shi, Chang, Xide Cheng, Zuyuan Liu, Kunyu Han, Penghui Liu i Long Jiang. "Numerical Simulation of the Maneuvering Motion Wake of an Underwater Vehicle in Stratified Fluid". Journal of Marine Science and Engineering 10, nr 11 (6.11.2022): 1672. http://dx.doi.org/10.3390/jmse10111672.
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When a vehicle moves underwater, disturbance is generated and a wake remains that destroys the original free surface and produces a new wake. In order to study the mechanism and characteristics of the wave-making wake generated by the maneuvering motion of an underwater vehicle in density-stratified fluid, the k-ε model and the VOF method that is based on the RANS equation were used in this paper to analyze the SUBOFF model in stratified fluid at different drift angles. Numerical simulation of the maneuvering motion was carried out under these angles, and the corresponding changes in flow field caused by this motion were analyzed. The results from the comparison and analysis of the surface wave wakes under different drift angles in stratified fluid show that with the increasing drift angle, the motion wake of the vehicle still exhibits obvious Kelvin wave system characteristics. However, there are significant changes in hydrodynamic performance. The asymmetry of the surrounding flow field will increase with the increase in the drift angle. The pressure of the underwater vehicle is inversely proportional to the velocity of the surrounding flow field, and the amplitude of the peak and trough of the free surface wave is linearly related to the change in the drift angle. The numerical simulation can serve as a reference for the non-acoustic detection of the motion heading of an underwater vehicle and the motion trajectory of anti-reconnaissance underwater vehicles under actual sea conditions.
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Kim, Jun-Beom, Eun-Hong Min i Weoncheol Koo. "Experimental and Numerical Study on the Characteristics of Free Surface Waves by the Movement of a Circular Cylinder-Shaped Submerged Body in a Single Fluid Layer". Journal of Ocean Engineering and Technology 37, nr 3 (30.06.2023): 89–98. http://dx.doi.org/10.26748/ksoe.2023.006.
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Analyzing the interactions of free surface waves caused by a submerged-body movement is important as a fundamental study of submerged-body motion. In this study, a two-dimensional mini-towing tank was used to tow an underwater body for analyzing the generation and propagation characteristics of free surface waves. The magnitude of the maximum wave height generated by the underwater body motion increased with the body velocity at shallow submerged depths but did not increase further when the generated wave steepness corresponded to a breaking wave condition. Long-period waves were generated in the forward direction as the body moved initially, and then short-period waves were measured when the body moved at a constant velocity. In numerical simulations based on potential flow, the fluid pressure changes caused by the submerged-body motion were implemented, and the maximum wave height was accurately predicted; however, the complex physical phenomena caused by fluid viscosity and wave breaking in the downstream direction were difficult to implement. This research provides a fundamental understanding of the changes in the free surface caused by a moving underwater body.
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Almar, Rafael, Rodrigo Cienfuegos, Eduardo Gonzalez, Patricio Catalán, Hervé Michallet, Philippe Bonneton, Bruno Castelle i Leandro Suarez. "BARRED-BEACH MORPHOLOGICAL CONTROL ON INFRAGRAVITY MOTION". Coastal Engineering Proceedings 1, nr 33 (25.10.2012): 24. http://dx.doi.org/10.9753/icce.v33.currents.24.
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A conceptual analysis of the coupling between bars and infragravity waves is performed combining laboratory experiments and numerical modeling. Experiments are carried out in a wave flume with a barred profile. The Boussinesq fully-nonlinear model SERR1D is validated with the laboratory data and a sensitivity analysis is performed next to study the influence on the infragravity wave dynamics of bar amplitude and location, and swash zone slope. A novel technique of incident and reflected motions separation that conserves temporal characteristics is applied. We observe that changing bar characteristics induces substantial variations in trapped energy. Interestingly, a modification of swash zone slope has a large influence on the reflected component, controlling amplitude and phase time-lag, and consequently on the resonant pattern. Variations of trapped infragravity energy induced by changes of swash zone slope reach 25 %. These changes in infragravity pattern consequently affect short-wave dynamics by modifying the breakpoint location and the breaking intensity. Our conceptual investigation suggests the existence of a morphological feedback through the action of evolving morphology on infragravity structures which modulates the action of short-waves on the morphology itself.
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Kotani, Akira, Toshiharu Tanaka i Akira Hirano. "Development of Shock-Wave-Powered Actuators for High Speed Positioning (Second Report: Characteristics of Diaphragmless Shock Tube and Responsiveness of Actuator)". International Journal of Automation Technology 7, nr 5 (5.09.2013): 558–63. http://dx.doi.org/10.20965/ijat.2013.p0558.
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Shock tubes experiments are conducted on applications of shock waves to the actuator. The high-pressure and low-pressure sections of a general shock tube are separated by a diaphragm. In this study, a shock wave is generated by “diaphragmless shock tube” which is divided into two sections by a driver piston instead of the diaphragm. We have previously reported on the motion of a driven piston powered by a shock wave. However, not only piston speed but also high responsiveness is required for practical actuators used on manufacturing lines, in industrial robots, etc., The diaphragmless shock tube constructed in this paper is structured to be able to examine not only the motion of the driven piston but also the motion of the driver piston. In addition, the responsiveness of the piston motion of the actuator powered by shock waves is examined. It follows from what has been said thus far that a shock wave can be applied to an actuator with high responsiveness.
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Kashiwagi, Masashi. "Hydrodynamic Study on Added Resistance Using Unsteady Wave Analysis". Journal of Ship Research 57, nr 04 (1.12.2013): 220–40. http://dx.doi.org/10.5957/jsr.2013.57.4.220.
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It is known that the added resistance in waves can be computed from ship-generated unsteady waves through the unsteady wave analysis method. To investigate the effects of nonlinear ship-generated unsteady waves and bluntness of the ship geometry on the added resistance, measurements of unsteady waves, wave-induced ship motions, and added resistance were carried out using two different (blunt and slender) modified Wigley models. The ship-generated unsteady waves are also produced by the linear superposition using the waves measured for the diffraction and radiation problems and the complex amplitudes of ship motions measured for the motion-free problem in waves. Then a comparison is made among the values of the added resistance by the direct measurement using a dynamometer and by the wave analysis method using the Fourier transform of measured and superposed waves. It is found that near the peak of the added resistance where ship motions become large, the degree of nonlinearity in the unsteady wave becomes prominent, especially at the forefront part of the wave. Thus, the added resistance evaluated with measured waves at larger amplitudes of incident wave becomes much smaller than the values by the direct measurement and by the wave analysis with superposed waves or measured waves at smaller amplitude of incident wave. Discussion is also made on the characteristics of the added resistance in the range of short incident waves.
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Fitriadhy, Ahmad, Nurul Aqilah Mansor i Nur Adlina Aldin. "Heave and Pitch Motions of a Towed Ship in Waves Incorporated with an Asymmetrical Bridle Towline Model". EPI International Journal of Engineering 2, nr 1 (27.06.2019): 34–40. http://dx.doi.org/10.25042/epi-ije.022019.07.
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Investigation of a ship towing system performance in waves incorporated with an asymmetrical towline configuration is necessarily to be studied to ensure a towing safety of navigation. To achieve the objective, this paper presents the ship towing motion performance in waves using Computational Fluid Dynamic (CFD) approach. Here, the heave and pitch motions of the towed ship so-called barge has been analysed, where several effects of the towing angle and towing speeds have been taken into account. In the calm water condition, the results revealed that the increase of tow angle was proportional with the sufficient reduction of the sway amplitude motion and inversely proportional to her yaw motion. The increase of the asymmetrical tow angle, however, has led to increase her sway motion amplitude in wave condition and conversely reduced the tow speed increased. In addition to the pitch motion characteristic, it subsequently increased by 12.1% as the tow angle raised from 25° to 35°; meanwhile the pitch motion of barge has by 10.2% as the tow speed increased from 0.655 m/s to 0.728 m/s. This CFD simulation is very useful as the preliminary prediction on the heave and pitch motion characteristics ensure a safety navigation of a towed ship in waves.
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Cen, W. J., X. H. Du, D. J. Li i L. N. Yuan. "Oblique Incidence of Seismic Wave Reflecting Two Components of Design Ground Motion". Shock and Vibration 2018 (13.06.2018): 1–16. http://dx.doi.org/10.1155/2018/4127031.
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The wave field on the artificial boundary was separated into the free field without local topography effect and scattering field induced by local topography effect. The simulation of the free field under obliquely incident waves was conducted. Based on the assumption that the components of design ground motion were treated as the coincidence of oblique P wave and oblique SV wave, the relationship between the oblique input waves and the design ground motion was established in the free field. Further, the contributions to the two components of design ground motion of obliquely incident waves were discussed. The calculation model in time domain was achieved by the combination of the propagation characteristics of obliquely incident waves and the artificial boundary in the free field. The seismic response to the design ground motion was produced on the free surface. The verification of the 2D half-space model under oblique input waves indicated that the wave input method can accurately reflect the design ground motion on the free surface. Application of an earth-rock dam showed that oblique incidence of seismic waves results in significantly different dynamic response compared with the normal incidence. The proposed method can also be employed in the seismic analysis of large span structures with nonuniform ground motion input.
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Borcherdt, Roger D., i Leif Wennerberg. "General P, type-I S, and type-II S waves in anelastic solids; inhomogeneous wave fields in low-loss solids". Bulletin of the Seismological Society of America 75, nr 6 (1.12.1985): 1729–63. http://dx.doi.org/10.1785/bssa0750061729.
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Abstract The physical characteristics for general plane-wave radiation fields in an arbitrary linear viscoelastic solid are derived. Expressions for the characteristics of inhomogeneous wave fields, derived in terms of those for homogeneous fields, are utilized to specify the characteristics and a set of reference curves for general P and S wave fields in arbitrary viscoelastic solids as a function of wave inhomogeneity and intrinsic material absorption. The expressions show that an increase in inhomogeneity of the wave fields causes the velocity to decrease, the fractional-energy loss (Q−1) to increase, the deviation of maximum energy flow with respect to phase propagation to increase, and the elliptical particle motions for P and type-I S waves to approach circularity. Q−1 for inhomogeneous type-I S waves is shown to be greater than that for type-II S waves, with the deviation first increasing then decreasing with inhomogeneity. The mean energy densities (kinetic, potential, and total), the mean rate of energy dissipation, the mean energy flux, and Q−1 for inhomogeneous waves are shown to be greater than corresponding characteristics for homogeneous waves, with the deviations increasing as the inhomogeneity is increased for waves of fixed maximum displacement amplitude. For inhomogeneous wave fields in low-loss solids, only the tilt of the particle motion ellipse for P and type-I S waves is independent to first order of the degree of inhomogeneity. Quantitative estimates for the characteristics of inhomogeneous plane body waves in layered low-loss solids are derived and guidelines established for estimating the effect of inhomogeneity on seismic body waves and a Rayleigh-type surface wave in low-loss media.
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Jiang, T., T. E. Schellin i S. D. Sharma. "Horizontal Motions of an SPM Tanker Under Alternative Mooring Configurations". Journal of Offshore Mechanics and Arctic Engineering 117, nr 4 (1.11.1995): 223–31. http://dx.doi.org/10.1115/1.2827227.
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Horizontal motions of a tanker single point moored in current, wind, and waves were numerically investigated under four alternative configurations, namely, buoy mooring (SBM), articulated tower mooring (ATM), bow turret mooring (BTM), and internal turret mooring (ITM). The analysis was based on a previously validated, comprehensive mathematical model of the equations of motion in three degrees of freedom (surge, sway, and yaw) that considers five sets of forces: 1) nonlinear quasi-steady hydrodynamic response and control forces; 2) linear memory effects due to radiated waves; 3) nonlinear mooring restoring force characteristics; 4) empirical wind actions; and 5) first-order wave forces and wave drift forces. Locally linearized stability analyses showed that restoring characteristics have no influence on static bifurcations (typical for BTM and ITM) and only minor influence on dynamic bifurcations (typical for SBM and ATM). However, nonlinear time domain simulations revealed that they do affect the form of asymptotic motion trajectories as well as line tension amplitudes. It was found that turret position is a significant parameter and motion behavior is sensitive to the direction of wind and waves relative to current. Comparison of simulated time histories between autonomous and nonautonomous modes indicated that the traditional spectral analysis treating high-frequency and low-frequency responses separately may not be valid for locally unstable cases.
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D'Arrigo, Agatino. "HYDROGEOLOGICAL BREAKING CHARACTERISTICS OF WAVES ABOVE FRESH WATER SUBAQUEOUS SOURCES". Coastal Engineering Proceedings 1, nr 5 (29.01.2011): 11. http://dx.doi.org/10.9753/icce.v5.11.
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After a short review of the usefulness of maritime structures, particularly vertical wall breakwaters, long term observations of hydrogeological breaking on the bottom of Italy's Seas, as caused by the subaqueous source of fresh water, are discussed. The correlation between hydrogeological breaking and wave motion perturbation produced by compressed air or by oil is presented. These considerations are related to the observations of Admiral Alessandro Cialdi on the morphological breaking of waves above sand banks, thus producing calmness in the upper water.
Therefore, it appears possible to establish a very suggestive analogy between the atomic disintegration of the transformation of potential energy of the oscillatory tide wave into kinematic energy of its components (because of breaking), in accordance with the disintegration of the circular motion.
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Kawano, Masahiro, Satoshi Matsuda, Kozo Toyoda i Jun Yamada. "Seismic response of three-dimensional alluvial deposit with irregularities for incident wave motion from a point source". Bulletin of the Seismological Society of America 84, nr 6 (1.12.1994): 1801–14. http://dx.doi.org/10.1785/bssa0840061801.
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Abstract The purpose of this article is to further investigate the influence of local site conditions of surface soil layers on seismic ground motion by studying the response of a semi-spherical alluvial deposit model under the more realistic type incident wave field. The incident wave field is a spherical wave radiated from a point source that is situated at the near focal distance and the far focal distance. A plane SH wavelet is also considered for comparison. A least-squares technique is applied to solve the boundary problem. The surface displacements on the alluvial deposit and in the elastic half-space are evaluated for various focal distances and source incidence angles. The numerical results indicate that there are significant differences concerning scattering and diffraction of wave motions between the two horizontal components when the semi-spherical alluvial deposit is subjected to incident wave motions from a point source. In the near field and for the component involving predominantly P and SV waves, the coupling of these waves induces a great variation in the spatial distributions, the amplitudes, and the time histories of the surface displacements compared to the tangential component, which involves mostly SH waves. The wave propagation characteristics of this component are very similar to those for a plane SH wavelet. In the far field and for the tangential component, there is not such strong coupling among waves. It is also shown that the first reflected waves at the curved boundary are deeply related to scattering and to diffraction of wave motion in a surface soil layer with irregularities and play an important role in the development of later arrivals.
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Huang, Yang, i Decheng Wan. "Investigation of Interference Effects Between Wind Turbine and Spar-Type Floating Platform Under Combined Wind-Wave Excitation". Sustainability 12, nr 1 (27.12.2019): 246. http://dx.doi.org/10.3390/su12010246.
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In order to further understand the coupled aero-hydrodynamic performance of the floating offshore wind turbine (FOWT) in realistic ocean environment, it is necessary to investigate the interference effects between the unsteady aerodynamics of the wind turbine and different degree-of-freedom (DOF) platform motions under combined wind-wave excitation. In this paper, a validated CFD analysis tool FOWT-UALM-SJTU with modified actuator line model is applied for the coupled aero-hydrodynamic simulations of a spar-type FOWT system. The aero-hydrodynamic characteristics of the FOWT with various platform motion modes and different wind turbine states are compared and analyzed to explore the influence of the interference effects between the wind turbine and the floating platform on the performance of the FOWT. The dynamic responses of local relative wind speed and local attack angle at the blade section and wind-wave forces acting on the floating platform are discussed in detail to reveal the interaction mechanism between the aerodynamic loads and different DOF platform motions. It is shown that the surge motion and the pitch motion of the floating platform both significantly alter the local attack angle, while only the platform pitch motion have significant impacts on the local relative wind speed experienced by the rotating blades. Besides, the shaft tilt and the pro-cone angle of the wind turbine and the height-dependent wind speed all contribute to the variation of the local attack angle. The coupling between the platform motions along different DOFs is obviously amplified by the aerodynamic forces derived from the wind turbine. In addition, the wake deflection phenomenon is clearly observed in the near wake region when platform pitch motion is considered. The dynamic pitch motion of the floating platform also contributes to the severe wake velocity deficit and the increased wake width.
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Yuan, Peiyin, Pingyi Wang i Yu Zhao. "Innovative Method for Ship Navigation Safety Risk Response in Landslide-Induced Wave". Advances in Civil Engineering 2021 (27.05.2021): 1–10. http://dx.doi.org/10.1155/2021/6640548.
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When the bank of a reservoir slope slides along a weak structural plane at a high speed, “landslide slamming” will occur in the nearby water. The formation of landslide-induced waves is a serious threat to the safety of wharfs, shore marks, buildings in the water, and vessels navigating in reservoir areas. To ensure the safety of navigating ships, this study proposes a landslide-induced wave water ship navigation safety risk response technology. The propagation characteristics of landslide-induced waves are analysed based on a physical model experiment, and the characteristics of a ship's motion response and mooring cable tensions are studied under conditions of bow and stern mooring and multipoint mooring. The influences of the landslide-induced wave direction and ship navigation position on the ship rolling motion characteristics are discussed. The results of this study can further improve the navigation safety of ships in landslide-induced wave waters.
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Agalarov, Jafar H., Guldasta Akif Mammadova i Mexseti Akif Rustamova. "Investigation of waves in the strengthened net". Structural Mechanics of Engineering Constructions and Buildings 18, nr 3 (28.09.2022): 269–79. http://dx.doi.org/10.22363/1815-5235-2022-18-3-269-279.
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The movements of a reinforced net are considered. Mesh systems are used in various areas of modern technology, aviation, fishing, and construction. In recent years, much attention has been drawn to the complete equations that describe the motion of a deformable thread. In accordance with the studied task, the reinforcement of the net is carried out by adding terms in the equations of motion. In the planar case, the static behavior of the structure is investigated, and equations of motion are derived that allow the study of motion. The problem of wave propagation in deformable filament systems, taking into account a significant deviation of the filament shape from the original rectilinear one, is mathematically very difficult, since the equations of motion are a system of nonlinear differential equations in partial derivatives. To solve the problem, the method of characteristics is used. As well the method of characteristics solves the problem of the propagation of unloading waves (in the case of a load, shock waves arise). Depending on the velocity distribution at the boundary, the distribution of the strain constant on the characteristics is determined. The results are constructed by numerical integration of the integrals of the characteristics found by the method. The solution using the characteristic equations shows the occurrence of traveling waves.
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Gao, Xianjiao, Chenghua Li, Tao Liu, Bin Wu i Mingzhen Wang. "Research on wave motion response characteristics of a seaplane". Journal of Physics: Conference Series 1985, nr 1 (1.07.2021): 012031. http://dx.doi.org/10.1088/1742-6596/1985/1/012031.
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Shen, Chao, Bin Zhang, Shenglin Yan i Xiaoli Fu. "Cloud‐based virtual simulation system of wave motion characteristics". Computer Applications in Engineering Education 30, nr 2 (17.12.2021): 609–27. http://dx.doi.org/10.1002/cae.22476.
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Hernández, Lorenzo, i Jose Alzola. "HYDRODYNAMIC ASSESMENT ON MOTION PERFORMANCE CHARACTERISTICS OF GENERIC WAVE ENERGY POINT ABSORBERS". International Journal of Engineering Technologies and Management Research 4, nr 4 (31.01.2020): 1–26. http://dx.doi.org/10.29121/ijetmr.v4.i4.2017.72.
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This work condenses various modeling techniques for different Point Absorber configurations. An alternating frequency - time domain model is implemented in MatlabFORTRAN in order to compute the displacement, velocities and the power absorbed in the heave mode for both single and multiple body configurations. Coupling of different degrees of freedom are merely contemplated with regard to a single buoy motion. NEMOH and BEMIO solvers are applied in the solution of Newtons second law according to the Boundary Element Methodology. Initially, this Wave-to-Wire model is validated through comparison with previous experimental results for a floating cone cylinder shape (Buldra-FO3). A single, generic, vertical floating cylinder is contemplated then, that responds to the action of the passing regular waves excitation. Later, two equally sized vertical floating cylinders aligned with the incident wave direction are modeled for a variable distance between the bodies. In deep water, we approximate the convolutive radiation force function term through the Prony method. Using for instance triangular or diamond shaped arrays of three and four bodies respectively, the study delves into the interaction effects for regular waves. The results highlight the most efficient layout for maximizing the energy production whilst providing important insights into their performance, revealing displacement amplification-, capture width-ratios and the commonly known park effect.
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Chen, Ji-Kang, Guo-Dong Zhang i Wen-Yang Duan. "Numerical Study of Wave Drift Load and Turning Characteristics of KVLCC2 Ship in Regular Waves Based on TEBEM". Journal of Marine Science and Engineering 10, nr 7 (20.07.2022): 993. http://dx.doi.org/10.3390/jmse10070993.
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Maritime traffic has increased considerably in recent years, making energy efficiency and navigation safety of ships more crucial than ever. Hence, a two-time scale model based on the Taylor expansion boundary element method (TEBEM) is proposed to predict ship turning trajectories in regular waves. The maneuvering motion is calculated using a three degrees of freedom MMG model that considers the wave drift loads. TEBEM overcomes the shortcomings of the constant panel method in solving tangential induced velocity at a non-smooth boundary and that of the high-order boundary element method in dealing with a high-order derivative of the velocity potential at the corner. This significantly improves the calculation accuracy of the induced velocity and high-order derivative of velocity potential. Firstly, based on the TEBEM, the surge and sway wave drift forces and yaw moment of the KVLCC2 model with drift angle under full wave headings are calculated and compared with computational fluid dynamics results, using which the calculation accuracy of TEBEM is verified. Subsequently, the two-time scale model is used to calculate the turning trajectories of the KVLCC2 model in regular waves with different wave headings, wave frequencies, and wave steepness. The numerical results show that the drift angle has a certain effect on the wave drift loads of the ship, and the proposed model can effectively predict the ship’s turning motion in regular waves.
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Han, Duanfeng, Ting Cui, Lihao Yuan, Yingfei Zan i Zhaohui Wu. "Monitoring and Analysis of Wave Characteristics during Pipeline End Termination Installation". Processes 7, nr 9 (28.08.2019): 569. http://dx.doi.org/10.3390/pr7090569.
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Pipeline end termination (PLET) installation is an essential part of offshore pipe-laying operation. Pipe-laying operations are sensitive to pipe-laying barge motion and marine environmental conditions. Monitoring the field environment can provide a reasonable basis for planning pipe-laying. Therefore, the measurement and analysis of sea wave motion is helpful for the control and operational safety of the pipeline and vessels. In this study, an environmental monitoring system was established to measure wave motion during PLET operation. Fourier transforms were used to process images that were acquired by ultra-high-frequency X-band marine radar to extract wave parameters. The resulting wave spectra, as measured each minute, were used to simulate real-time wave data and calculate wave characteristics and regressed wave frequency and direction spectrum throughout the PLET operation. The regressed frequency, spectral density, and direction spectra were compared with the theoretical spectra to evaluate their similarity and find the most similar spreading function in the operational area (the South China Sea). Gaussian fitting of real-time wave data was tested while using a classical method. The marginal distribution and joint density of the wave characteristics were estimated and then compared with theoretical distributions to find the most suitable model for improving marine environmental forecasting.
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Ding, Hongyan, Xing Zhao, Conghuan Le, Puyang Zhang i Qiaoling Min. "Towing Motion Characteristics of Composite Bucket Foundation for Offshore Wind Turbines". Energies 12, nr 19 (2.10.2019): 3767. http://dx.doi.org/10.3390/en12193767.
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Composite bucket foundation (CBF) is an environmentally friendly form of offshore wind power foundation. By virtue of the air-floating subdivision structure in the bucket, the foundation has a self-floating characteristic and can allow for long-distance air-floating towing and transport. In this study, first, a numerical analysis was performed on the towing motion characteristics of CBF, and the formula for foundation stability was deduced; then, we probed into the variation rules of the natural period of the foundation with draft and analyzed the response amplitude operator (RAO) responses, added mass coefficients, radiation damping coefficients, and exciting forces (moments) of the composite bucket foundation under different drafts and different wave directions. Finally, we clarified the basic hydrodynamic characteristics of the composite bucket foundation in the frequency domain and adopted multiple random wave models to investigate the effects of different wave heights, periods, and spectral peak factors on the towing motion characteristics of composite bucket foundation.
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Wang, Zhihao, Yijun Chen, Hang Yuan, Ying Luo i Qun Zhang. "Real Micro-Doppler Parameters Extraction of Spinning Targets Based on Rotating Interference Antenna". Remote Sensing 14, nr 21 (23.10.2022): 5300. http://dx.doi.org/10.3390/rs14215300.
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Micro-Doppler is a unique characteristic of targets with micro-motions, which can provide significant information for target classification and recognition. However, the monostatic radar has the shortcoming of only obtaining the radial micro-motion characteristics. Although the vortex-electromagnetic-wave-based radar has the potential to obtain real micro-motion parameters, it has a high dependence on the mode number and purity of the orbital angular momentum, which greatly restricts its application in the micro-motion parameter extraction. To overcome the above problems, a new radar configuration based on the rotating interference antenna is proposed in this paper. Through the interference processing of the micro-Doppler curves of the rotating and fixed antenna, the curves containing the real micro-motion information of the target can be obtained. Then the real micro-motion characteristics of the spinning target can be reconstructed by the orthogonal matching pursuit algorithm. The effectiveness and robustness of the proposed method are validated by simulations.
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Shi, Hong Da, Shui Yu Li i Dong Wang. "Study on the Motions and Stress of Immersing Tunnel Element under Wave Actions". Applied Mechanics and Materials 328 (czerwiec 2013): 614–22. http://dx.doi.org/10.4028/www.scientific.net/amm.328.614.
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The dynamic characteristics of large-scale tunnel element are very important for the process of immersion. In the paper, the motions and stress of the element under wave actions were studied. The linear wave diffraction theory and the three-dimensional source distribution method were applied to calculate the wave loads and motion responses of the tunnel element under different incident wave conditions. In the study, there have no cable on the element. On the basis of the above theories, the stress and the motions of the element were studied. The first order wave forces and the second order wave force were deduced, and the motions equation was made.
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Ying, Zu-Guang, i Yi-Qing Ni. "Dynamic characteristics of infinite-length and finite-length rods with high-wave-number periodic parameters". Journal of Vibration and Control 24, nr 11 (10.01.2017): 2344–58. http://dx.doi.org/10.1177/1077546316687676.
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The dynamic characteristics of the infinite-length and finite-length rods with periodic distribution parameters are studied. The differential equation of longitudinal motion of the period-parametric rod is given. The algebraic matrix equation for the wave motion characteristics of the infinite-length periodic rod is derived based on the Bloch theorem and Fourier series. The characteristic frequencies are determined by the matrix eigenvalues which depend on the characteristic wave number and parametric wave number. Then the algebraic matrix equation for the dynamic characteristics of the finite-length periodic rod is derived based on the Galerkin method. The natural frequencies are determined by the matrix eigenvalues which depend on only the parametric wave number. An improving approach algorithm for solving the eigenvalue problem of high degree-of-freedom systems is developed based on the Rayleigh quotient. Finally, the circular cross-section rod with period-varying diameter is considered and numerical results on the dynamic characteristics are given. Large characteristic wave number and parametric wave number are considered for the infinite-length and finite-length periodic rods. The characteristic frequencies varying with the characteristic wave number and parametric wave number are shown, and the band gaps vanishing are revealed for increasing characteristic wave number. The finite-length periodic rod has the dynamic characteristics different from the infinite-length periodic rod. The effect of the term number of the displacement expansion on the natural frequencies and the natural frequencies varying with the parametric wave number and wave amplitude are shown for the finite-length periodic rod. The local resonance and periodical short descent of the natural frequencies with the increase of the parametric wave number and the different changes of the natural frequencies with the parametric wave amplitude are revealed. The above new dynamic characteristics of the infinite-length and finite-length rods with periodic distribution parameters have a potential application to period-structural design and optimization.
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Li, Ang, i Yunbo Li. "Numerical and Experimental Study on Seakeeping Performance of a High-Speed Trimaran with T-foil in Head Waves". Polish Maritime Research 26, nr 3 (1.09.2019): 65–77. http://dx.doi.org/10.2478/pomr-2019-0047.
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Abstract The longitudinal motion characteristics of a slender trimaran equipped with and without a T-foil near the bow are investigated by experimental and numerical methods. Computational fluid dynamics ( CFD) method is used in this study. The seakeeping characteristics such as heave, pitch and vertical acceleration in head regular waves are analyzed in various wave conditions. Numerical simulations have been validated by comparisons with experimental tests. The influence of large wave amplitudes and size of T-foil on the longitudinal motion of trimaran are analyzed. The present systematic study demonstrates that the numerical results are in a reasonable agreement with the experimental data. The research implied that the longitudinal motion response values are greatly reduced with the use of T-foil.
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Zhou, Xiaoguo, Qingdian Jiang, Yan Wang, Linfeng Chen, Shuqi Wang i Kunpeng Wang. "Numerical Simulation of Wave–Current Force Characteristics of Horizontal Floating Cylinder in Heave Motion". Journal of Marine Science and Engineering 10, nr 12 (4.12.2022): 1884. http://dx.doi.org/10.3390/jmse10121884.
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This paper presents the characteristics of the heave motion responses and hydrodynamic forces of a horizontal floating circular cylinder during a wave–current interaction. A two-dimensional numerical model based on the CFD (Computational Fluid Dynamics) method for modeling wave flow is validated and verified. The hydrodynamic characteristics of the horizontal floating cylinder during heave motion were calculated and analyzed under the conditions of different k values (stiffness of spring), wave amplitudes, submerged depths, and flow rates. The results show that, with the increase in the k value, the vibration amplitude of the cylinder first increases and then decreases. The vibration amplitude peak is achieved, the vibration frequency is consistent with the wave frequency, and a resonant motion takes place. When the wave amplitude and flow rate are fixed, the maximum vibration amplitude decreases as the wave period increases. When the cylinder is half-submerged, the effect of the current on motion is significant; the vibration amplitude is less than the wave amplitude. When a quarter is submerged, the vibration amplitude is larger than that of the half-submerged cylinder at each k. The maximum amplitude is greater than the wave amplitude, and the vibration amplitude reaches the minimum at the moderate flow rate for each k.
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Gong, Houjun, Xiaoxi Zhang, Nan Gui, Yanping Huang, Xingtuan Yang i Shengyao Jiang. "Study on the Density Wave Instability in Natural Circulation System under Rolling Conditions". International Journal of Energy Research 2023 (3.02.2023): 1–16. http://dx.doi.org/10.1155/2023/3249806.
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In the ocean environment, the thermal fluid system installed on the ship moves with the waves. This unsteady transient motion imposes additional body forces on the liquid. Thereby, the thermohydraulic properties of the thermal fluid system are changed, especially for natural circulation systems with a low driving force. Flow instability related to system security is a common two-phase flow system phenomenon. It is an essential subject in the study of thermal-hydraulic characteristics. In this paper, the density wave instability in a low-pressure natural circulation system with several parallel heating channels in the circumstances of rolling motion is studied by PNCMC (Program for Natural Circulation under Motion Condition). PNCMC is a newly developed program by adding extra body force induced by ship motions in two-phase’s momentum equations. The mechanism of rolling motion and its impact on flow oscillation and unstable boundary power are investigated. The supercooled boiling caused by the higher surface heat flux firstly promotes the occurrence of density wave oscillations between parallel heating channels. When enough steam enters the riser, the system density wave oscillation occurs under the gravity pressure drop-flow rate-vapor fraction feedback. A more complicated compound oscillation is created by superimposing the interchannel oscillation and the system density wave oscillation. If the rolling motion has little change to the natural circulation flow, when density wave instability arises, the flux oscillation rule and the instability boundary power are basically consistent with the vertical conditions. When the rolling angle is large, the fairly large amplitude flow oscillation generated by rolling will prevent density wave instability from occurring and force the flow oscillation to obey the law of rolling effects.
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Jiang, T., i T. E. Schellin. "Motion Prediction of a Single-Point Moored Tanker Subjected to Current, Wind and Waves". Journal of Offshore Mechanics and Arctic Engineering 112, nr 1 (1.02.1990): 83–90. http://dx.doi.org/10.1115/1.2919840.
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Horizontal motions of a tanker attached to a single-point mooring (SPM) terminal were predicted using digital simulation in the time domain. Excitations from steady current, gusting wind, and irregular seaway were included. Hydrodynamic forces generated by the ship’s motion and the action of its propeller and rudder were calculated in accordance with a previously validated, nonlinear quasi-steady four-quadrant maneuvering model, extended to include linear memory effects due to waves generated by the moving ship. Memory effects were approximated by a vectorial recursive state space model corresponding to a set of higher order differential equations. A nonlinear relationship of the force in the mooring hawser was assumed to represent restoring force characteristics of the SPM system. Wave excitation forces comprised first-order forces at wave frequencies and second-order drift forces at low frequencies. First-order wave forces were obtained by superposition of force components corresponding to regular wave components comprising the wave spectrum. Based on the low-frequency wave envelope, drift forces were calculated using mean drift force coefficients in regular waves. Selected sample simulations are presented to illustrate the use of this digital simulation method.