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Статті в журналах з теми "Wave motion characteristics"
1
Pan, Wenbo, Meng He, and 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, no. 5 (May 4, 2023): 977. http://dx.doi.org/10.3390/jmse11050977.
Повний текст джерелаАнотація:
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.
2
Sanders, Ross H., Jane M. Cappaert, and David L. Pease. "Wave Characteristics of Olympic Breaststroke Swimmers." Journal of Applied Biomechanics 14, no. 1 (February 1998): 40–51. http://dx.doi.org/10.1123/jab.14.1.40.
Повний текст джерелаАнотація:
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.
3
Chen, Long Wei, Wei Ming Wang, and Rui Sun. "Correlation of Site Characteristic Period with Predominant Period of Ground Acceleration by a Simplified Model." Applied Mechanics and Materials 238 (November 2012): 864–67. http://dx.doi.org/10.4028/www.scientific.net/amm.238.864.
Повний текст джерелаАнотація:
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.
4
Li, Chun Liu, and Yun Peng Zhao. "Motion Characteristics of Composite-Type Sea Cage under Pure Wave." Advanced Materials Research 490-495 (March 2012): 3405–9. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.3405.
Повний текст джерелаАнотація:
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.
5
Lian, Jijian, Junni Jiang, Xiaofeng Dong, Haijun Wang, Huan Zhou, and Pengwen Wang. "Coupled Motion Characteristics of Offshore Wind Turbines during the Integrated Transportation Process." Energies 12, no. 10 (May 27, 2019): 2023. http://dx.doi.org/10.3390/en12102023.
Повний текст джерелаАнотація:
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.
6
Chen, Gong Lian, Wen Zheng Lu, Lei Wang, and Qi Wu. "Study on Far-Field Ground Motion Characteristics." Applied Mechanics and Materials 438-439 (October 2013): 1471–73. http://dx.doi.org/10.4028/www.scientific.net/amm.438-439.1471.
Повний текст джерелаАнотація:
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.
7
Huang, Zhi-Xun. "Negative Velocity Characteristics in Electromagnetism." Physical Science International Journal 27, no. 1 (May 13, 2023): 25–53. http://dx.doi.org/10.9734/psij/2023/v27i1776.
Повний текст джерелаАнотація:
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.
8
N.M., Khairuddin,, Jaswar Koto, Nur Ain, A.R., Mohd Azhari , J., and Najmie, A. "Experimental Study on Translation Motion Characteristics of Moored Symmetrical Semi-submersible in Regular Waves." Journal of Mechanical Engineering 17, no. 1 (April 1, 2020): 77–89. http://dx.doi.org/10.24191/jmeche.v17i1.15220.
Повний текст джерелаАнотація:
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.
9
Wang, Y. Z. "Motion and stability of caisson breakwaters under breaking wave impact." Canadian Journal of Civil Engineering 28, no. 6 (December 1, 2001): 960–68. http://dx.doi.org/10.1139/l01-040.
Повний текст джерелаАнотація:
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.
10
Katafuchi, Masaki, Hideyuki Suzuki, Yuya Higuchi, Hidetaka Houtani, Edgard B. Malta, and Rodolfo T. Gonçalves. "Wave Response of a Monocolumn Platform with a Skirt Using CFD and Experimental Approaches." Journal of Marine Science and Engineering 10, no. 9 (September 9, 2022): 1276. http://dx.doi.org/10.3390/jmse10091276.
Повний текст джерелаАнотація:
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.
Дисертації з теми "Wave motion characteristics"
1
Suoja, Nicole Marie. "Directional wavenumber characteristics of short sea waves." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88473.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 2000.Includes bibliographical references (leaves 134-141).
by Nicole Marie Suoja.
Ph.D.
2
Komarov, Alexander. "New methods for detecting dynamic and thermodynamic characteristics of sea ice from radar remote sensing." Institute of Electrical and Electronics Engineers, 2014. http://hdl.handle.net/1993/30225.
Повний текст джерелаАнотація:
This dissertation presents new methods for detecting dynamic and thermodynamic characteristics of Arctic sea ice using radar remote sensing.
A new technique for sea ice motion detection from sequential satellite synthetic aperture radar (SAR) images was developed and thoroughly validated. The accuracy of the system is 0.43 km obtained from a comparison between SAR-derived ice motion vectors and in-situ sea ice beacon trajectories. For the first time, we evaluated ice motion tracking results derived from co-polarization (HH) and cross-polarization (HV) channels of RADARSAT-2 ScanSAR imagery and formulated a condition where the HV channel is more reliable than the HH channel for ice motion tracking. Sea ice motion is substantially controlled by surface winds. Two new models for ocean surface wind speed retrieval from C-band SAR data have been developed and validated based on a large body of statistics on buoy observations collocated and coincided with RADARSAT-1 and -2 ScanSAR images. The proposed models without wind direction input demonstrated a better accuracy than conventionally used algorithms. As a combination of the developed methods we designed a wind speed-ice motion product which can be a useful tool for studying sea ice dynamics processes in the marginal ice zone.
To effectively asses the thermodynamic properties of sea ice advanced tools for modeling electromagnetic (EM) wave scattering from rough natural surfaces are required. In this dissertation we present a new analytical formulation for EM wave scattering from rough boundaries interfacing inhomogeneous media based on the first-order approximation of the small perturbation method. Available solutions in the literature represent special cases of our general solution. The developed scattering theory was applied to experimental data collected at three stations (with different snow thicknesses) in the Beaufort Sea from the research icebreaker Amundsen during the Circumpolar Flaw Lead system study. Good agreement between the model and experimental data were observed for all three case studies. Both model and experimental radar backscatter coefficients were considerably higher for thin snow cover (4 cm) compared to the thick snow cover case (16 cm). Our findings suggest that, winter snow thickness retrieval may be possible from radar observations under particular scattering conditions.
3
Lee, Cheng-Ta, and 李政達. "Experimental study of the particle’s motion characteristics for wave-current interactions." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/r29r29.
Повний текст джерелаАнотація:
碩士國立中山大學
海洋環境及工程學系研究所
96
There is a long terms of developement for academics theoretical analyzing and experimental researching by using the Lagrangian method. But for such trajectory experimentalists still have interference with reflected waves because of the length of the water tank is too short or the diameter and the density of the simulate particle , in spite of measuring the trajectory of the fluid particle have done. For there is no quite completed quantification data for the trajectory of fluid particle, this study is aiming at researching the truly movement of the flow field under wave-current interaction by trajectory measuring. This research choosing the simulate particle’s diameter for 1 mm , collocating with a high-speed vedio camera to record the particle’s moving characteristics while the wave-current interaction occured, to proceed a series of qualitative and quantitative testing. And to comple with all these data and improve the modification by using Image Processing to derive and orientate the coordinates . According to the experimental results of the flow field,it has proved that mass transport occured at the same-depth and no-flow condition through the wave progressing direction.The trajectory of the fluid particle of wave-current interaction in co-flow , its curve presenting the cross-convolution increasing and even presenting the cuspidal locus. And the trajectory of the fluid particle of wave-current interaction in inverse –flow is opposite to the trajectory of the no-flow movement. The results of the experiment is quite accord with to the 3rd order the theoretical analyzing of Chen （1994）and Shu、Chen（2006）。The fluid particle reproducting the moving period of the high-elevation is greater than the wave’s and increasing by the sharpness of the wave. The mass transport velocity is the same theory results ,and decreased deviation of artificiality in estimating particle position. According to the ratio of the experimental results, root mean square of error Ex and total mass transport displacement. The experimental results compared to the theoretical results obtained by Chen (1994)and Hsu、Chen(2006) has the similar results as well.
4
Lin, Zen-Huang, and 林志煌. "A Study on the Motion and Wave Damping Characteristics of Floating Structure." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/57865304701154102185.
Повний текст джерелаАнотація:
碩士國立中山大學
海洋環境及工程學系研究所
91
Abstract A boundary element method numerical scheme is developed to study the dynamic response and the wave damping characteristics of a floating structure under an incident wave approaching. The coupled surge, heave and pitch motion of a floating structure are included in the model. The equation of motion of the numerical model has been set up; meanwhile the solution of equations has been solved through the Runge-Kutta fifth order method. The hydrodynamic physical model tests have been carried out to verify the goodness of the numerical model. The numerical solutions and the experimental results have good agreements. It means that the BEM developed by this paper has its own accuracy. The study results show that the wave with shorter period has better effect on wave damping. In general, a floating breakwater, which is deeper under the water and wider in width, has smaller transmission coefficients. Practically when designing a floating structure, it suggests that the designer should increase the width rather than deepen the depth of structure. It is because the effects of dissipating wave energy are more obvious when increasing the width than the depth.
5
Wu, Yan-Chyuan, and 吳炎全. "Dynamic Characteristics of Recoil Motion and Shock Wave Caused by Reducing Force Mechanism." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/7ks8jh.
Повний текст джерелаАнотація:
博士國立臺北科技大學
機電科技研究所
99
HEAT and APFSDS projectiles are fired at muzzle velocities of Mach 3.4 and 4.4 respectively, from the cannon either equipped with a multi-perforated muzzle brake (MPMB) or with bare muzzle. HE projectile is fired at the muzzle velocity of Mach 2 by the howitzer installed a double baffled muzzle brake. In the recoil system, the muzzle brake moderates the recoil velocity and prolongs the time of resistance to the propellant gases force, thereby reducing the inner pressure of the recoil cylinder and attenuating the recoil force on trunnions. In the near field, dynamic muzzle features such as the precursor wave, overpressures and negative pressures are formed at different portions of the muzzle brake. In the middle field, the projectile N-wave and acoustic images of Mach cone are acquired by a 32-microphone ring array. Acoustic images of supersonic projectile shock wave caught by microphone array integrated a camera is an original contribution to field of armament engineering. No precedent is known, and no experimental results of such a method have been published until now. All measurements in this study can be a significant reference for developing guns, tanks or the chassis of fighting vehicles.
6
Mutnuri, Venkata Satyanand. "Spectral Analysis of Wave Motion in Nonlocal Continuum Theories of Elasticity." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5437.
Повний текст джерелаАнотація:
Traditionally, in solid mechanics, classical continuum theories of elasticity have been an important
tool in the examinations of behaviour of solids under external loads. However, due to
absence of length scale information in the theory, classical continuum theories have been found
to be inadequate in examining phenomena such as shear band formations, damage evolution,
etc., in solids. Further, with advent of novel solid materials, such as, composites and metamaterials,
which necessarily involve microscale structure, a need has arisen to generate knowledge
for behaviour of solids with microstructure. To address these aspects, generalization or reformulation
of continuum elasticity theories has been proposed in the solid mechanics literature.
Concepts put forth included: augmenting material particles with additional internal degrees of
freedom, augmenting constitutive equation with higher gradients of strain or with atomic potential
type interactions. The former type of generalization involves Mindlin-type solid, and the
later type involves, what now known in the literature as, nonlocal continuum solid. In practice,
given a new theory, it is customary to apply the theory to various initial-boundary value problems
(IVBPs) for examination of its predictability of experimentally observable characteristics
of solids. The IVBPs typically include static, buckling, bending, vibration and wave propagation
analyses. Although there exists abundant literature on most of the IVBPs, however, wave
motion analyses are few and requires further investigations. In this thesis, nonlocal continuum
theories of elasticity are critically examined with respect to wave motion characteristics.
By formulation, nonlocal continuum theories are valid in between any two consecutive length
scales in a solid. As a theoretical framework, nonlocal theories have shared their success in
mitigating the limitations of classical continuum framework, however, there still exist certain
problematic features. Nonlocal continuum theories could predict experimentally observed wave
dispersion behaviour. However, there exist unrealistic features in the wave dispersion as well as
wave dissipation characteristics in certain nonlocal models. It is known in the literature that, a
class of gradient models show violation of the relativistic causality or the Einstein causality in
the wave motion responses. In the case of integral nonlocal models, instantaneous interaction of
material particles via kernel functions is observed to be unphysical, except at the atomic scale
[32]. There is ongoing research in implementing the boundary conditions within the nonlocal
continuum theories. In a classical continuum, Dirichlet and Neumann boundary conditions
are applied on the boundary. Dirichlet boundary condition restricts the degrees of freedom of
material particles at the boundary in the directions of Euclidean space. Neumann boundary
condition relates the applied surface tractions to the gradients of the degrees of freedom at
the boundary. In gradient elasticity models, nonlocal formulation introduces classical as well
as non-classical boundary conditions corresponding to internal stress/deformation and higher
order internal stress/deformation terms, respectively. It is not clear whether there exists any
practical implication of the higher order degrees of freedom or the internal stresses. This issue
is further ampli fied in the integral nonlocal models as there exist in finite number of higher order
degrees of freedom and internal stresses. In order to understand the above problematic aspects,
a wave motion study has been carried out in this thesis and it is divided into four parts.
In the first part of the thesis, a Fourier frequency domain-based wave motion parameters
in a class of gradient and integral nonlocal continuum models are critically examined, within
the setting of a 1D rod. The wave motion parameters include wave modes, group speeds
and frequency response function. It is observed that certain nonphysical aspects exist in the
considered nonlocal models. These aspects include existence of infi nitely large or infi nitesimally
small group speeds, negative group speeds, instantaneous propagation of energy via evanescent
modes and absence of wave attenuation. Upon considering the physically realizable wave modes,
it is shown that classical continuum type boundary conditions are sufficient in order to study a
wave propagation boundary value problem in certain nonlocal continuum models. In order to
aid the above observations, a wave motion responses utilizing spectral finite element method,
has been presented. In literature, there exist a mathematical framework examining the subject
of agreement or disagreement of the principle of primitive causality in any linear media. This
framework is known in the literature as Kramers-Kronig (K-K) relations. Utilizing the wave
modes of the nonlocal continuum models, an examination of agreement or disagreement of
wave motion responses to the principle of primitive causality is presented in the second part of
the thesis. It is observed that, the classical form of K-K relations is not sufficient to perform
the examination. Therefore, an extended form has been derived and utilized to understand
the various wave motion characteristics. It is shown that existence of negative speeds and
in nitesimally small speeds violate the primitive causality. Further, certain nonphysical wave
motion characteristics have been demonstrated to be mitigated upon considering K-K relations
corrected wave modes in the Fourier domain wave motion analysis.
There is an ongoing research in identifying and quantifying the nonlocal material parameters
for the nonlocal continuum theories. In the third part of the thesis, a framework is proposed for
derivation of the nonlocal kernel functions from the experimental wave dispersion data. This
framework conducts a Fourier frequency domain analysis and exploits the frequency spectrum
relations of lattice dynamics and nonlocal elasticity models in conjunction with the experimental
data, within 1D setting. As an outcome, nonlocal material moduli with finite support for
integral type nonlocal models are obtained that can represent the complex wave dispersion
data accurately over entire first Brillouin zone.
In the last part of the thesis, examination of wave motion characteristics and application of
the K-K analysis framework has been presented within the setting of 1D beams. It is shown
that, the above spectral analysis framework can be extended towards various structures, such
as, Euler-Bernoulli and Timoshenko beams. Observations similar to integral type nonlocal rods
has been noted in the Integral beam model. However, in the case of gradient theories, agreement
or disagreement to the principle of primitive causality has been observed to depend on not only
on the constitutive model but also on the kinematics of the structure.
7
Wong, Wei-Ying, and 黃薇穎. "Acceleration and Velocity Characteristics of Retreated Flow during Run-down Motion of Solitary Wave over Sloping Beach." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/18753255183088872276.
Повний текст джерелаАнотація:
碩士國立中興大學
土木工程學系所
105
The evolution and detailed characteristics of the retreated flow during the run-down phase of a solitary wave propagating over 1:3 sloping bottom were investigated experimentally, using particle trajectory method of flow visualization technique and high-speed particle image velocimetry (HSPIV). A series of experiments were performed with several different fields of view, and with several incident solitary waves having wave height (H0) to water depth (h0) ratio of 0.171, 0.263 and 0.363. The velocity fields were obtained by ensemble averaging the repeated measurements. Several preliminary tests were carried out to validate and ensure the quality of the measured data. In addition, the vorticity, acceleration, and pressure gradient were obtained by the velocity profiles. The sensitivity tests for acceleration calculation were performed in order to reduce the bias of the results. Furthermore, an interesting phenomenon of the vortex structure generated from a separated boundary layer in the retreated flow during run-down motion is explored. According to the results obtained qualitatively and quantitatively by utilizing flow visualization technique and HSPIV measurements, related features of flow field and vortex structure, which were hardly discovered and depicted in the past due to the rudimentary equipment, are presented and discussed. Firstly, a striking phenomenon of flow bifurcation during run-up phase is investigated. Second, the characteristics of flow deceleration or acceleration, including the local and convective accelerations, being accompanied by the adverse or favorable pressure gradient in the retreated flow are illustrated. Furthermore, the spatial variation of the critical section where the critical flow with Froude number being equal to unity takes place is investigated. Moreover, the mechanism for the incipient flow separation, accompanied by the formation of the separated shear layer from the sloping bottom during early and first-half middle stages of run-down motion, and the variation of the pressure gradient before, during and after the incipient flow separation are explored. Besides, the evolution of the vortex structure beneath the separated shear layer, including the position and vorticity of the primary vortex core moving offshore under the high-speed meandering stream during second-half middle and late stages of run-down motion are discussed.
8
Hwung, Yi-Ping, and 黃一平. "The numerical study of characteristics of wave attenuation and motion amplitude for mooring plate under water surface." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/03238347806192278987.
Повний текст джерела
9
Chen, Chun-Te, and 陳俊德. "The characteristic of ground motion and seismic wave simulation of the Taipei basin and the ChiaNan plain." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/56863427889952041251.
Повний текст джерелаАнотація:
博士國立中央大學
地球科學學系
101
The earthquakes were well recorded by very dense strong-motion network Taiwan Strong Motion Instrumentation Program (TSMIP). The sufficient records provide an opportunity to analyze the earthquake position how influence the basin response. We apply single spectral ratio method (H/V ratio) to analyze the records at 43 stations of the Taipei TSMIP network. The result of H/V ratios comparison of depth indicated the H/V ratios obtained using deep events for the most part larger than shallow events at low frequency (0.2~3.0Hz). The analysis result of H/V ratios comparison of azimuth indicate that the H/V ratios obtained using southwest earthquakes generally larger than southeast when the stations located in the northern part of the basin, but show unapparent when the stations near the central and southern part of the basin. The result of H/V ratios comparison of epicenter distance indicated the H/V ratios show unapparent spectra ratios difference between far and near epicenter. We apply 2D and 3D numerical modeling to Taipei basin. The simulations show that for the Taipei basin, generation of large H/V spectral amplifications occur for large degree planar S-wave front. The simulations also show that the H/V spectral amplifications display strong planar S-wave front azimuthal dependence. The modeling obtained similar conclusion with the observed analysis. In this study we use 2D and 3D finite-difference method to simulating the wave propagation of the JiaSian earthquake. The results of the simulation demonstrate that the long duration surface wave of the west ChiaNan plain resulting from the multi-pathing waves trapped in the top Pleistocene formation. The snapshots of the wave propagation display that the seismic wave bending on the Shanhua and Shinshi area along Zengwun River. The larger PGV and PGD maybe the reason explains that the TN110 train de-railed but TN105 not cause by the seismic wave bending and local site effect.
Книги з теми "Wave motion characteristics"
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Suoja, Nicole Marie. Directional wavenumber characteristics of short sea waves. Cambridge, Mass: Massachusetts Institute of Technology, 2000.
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L, Clawson K., and Air Resources Laboratory (U.S.), eds. Vortex wake characteristics of B757-200 and B767-200 aircraft using the tower fly-by technique. Silver Spring, Md: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Air Resources Laboratory, 1993.
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D, Montgomery Matthew, Chuang H. Andrew, NASA Glenn Research Center, and United States. National Aeronautics and Space Administration., eds. Development of a linearized unsteady Euler analysis with application to wake/blade-row interactions. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.
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Zeitlin, Vladimir. Wave Motions in Rotating Shallow Water with Boundaries, Topography, at the Equator, and in Laboratory. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198804338.003.0004.
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The chapter illustrates the influence of lateral boundaries, bottom topography, outcroppings, equatorial tangent plane approximation, and cylindrical channel geometry in laboratory experiments on the wave spectrum, and characteristics of waves in rotating shallow-water model. It is shown that all these effects lead to appearance of wave-guide modes, localised in one spatial direction, and freely propagating in another one. These modes are coastal and equatorial Kelvin waves, topographic and equatorial Rossby waves, shelf and edge waves, equatorial Yanai and inertia–gravity waves, and frontal waves. Their dispersion and polarisation relations are established, and their properties explained. Mountain (lee) waves are also treated.
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Professor, Baby. Waves in Action: Characteristics of Waves Energy, Force and Motion Grade 3 Children's Physics Books. Speedy Publishing LLC, 2021.
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Professor, Baby. Waves in Action: Characteristics of Waves Energy, Force and Motion Grade 3 Children's Physics Books. Speedy Publishing LLC, 2021.
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Vortex wake characteristics of B757-200 and B767-200 aircraft using the tower fly-by technique. Silver Spring, Md: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Air Resources Laboratory, 1993.
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Development of a linearized unsteady Euler analysis with application to wake/blade-row interactions. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.
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Escudier, Marcel. Turbulent flow. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0018.
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In this chapter the principal characteristics of a turbulent flow are outlined and the way that Reynolds’ time-averaging procedure, applied to the Navier-Stokes equations, leads to a set of equations (RANS) similar to those governing laminar flow but including additional terms which arise from correlations between fluctuating velocity components and velocity-pressure correlations. The complex nature of turbulent motion has led to an empirical methodology based upon the RANS and turbulence-transport equations in which the correlations are modelled. An important aspect of turbulent flows is the wide range of scales involved. It is also shown that treating near-wall turbulent shear flow as a Couette flow leads to the Law of the Wall and the log law. The effect of surface roughness on both the velocity distribution and surface shear stress is discussed. It is shown that the distribution of mean velocity within a turbulent boundary layer can be represented by a linear combination of the near-wall log law and an outer-layer Law of the Wake.
Частини книг з теми "Wave motion characteristics"
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Espinoza, Fernando. "General Characteristics of Waves." In Wave Motion as Inquiry, 25–57. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-45758-1_2.
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Eibl, Regine, Sören Werner, and Dieter Eibl. "Bag Bioreactor Based on Wave-Induced Motion: Characteristics and Applications." In Disposable Bioreactors, 55–87. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/10_2008_15.
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Hao, H. "Characteristics of dynamic response and damage of RC structures to blast ground motion." In Wave propagation Moving load – Vibration Reduction, 11–23. London: CRC Press, 2021. http://dx.doi.org/10.1201/9781003211372-3.
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Liu, Zhigang. "Wave Motion Characteristic of Contact Line Considering Wind." In Detection and Estimation Research of High-speed Railway Catenary, 55–75. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-2753-6_3.
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Loosen, Simon, Matthias Meinke, and Wolfgang Schröder. "Numerical Analysis of the Turbulent Wake for a Generic Space Launcher with a Dual-Bell Nozzle." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 163–77. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_10.
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Abstract The turbulent wake of an axisymmetric generic space launcher equipped with a dual-bell nozzle is simulated at transonic ($$Ma_\infty = 0.8$$ and $$Re_D = 4.3\cdot 10^5$$) and supersonic ($$Ma_\infty = 3$$ and $$Re_D = 1.2\cdot 10^6$$) freestream conditions, to investigate the influence of the dual-bell nozzle jet onto the wake flow and vice versa. In addition, flow control by means of four in circumferential direction equally distributed jets injecting air encountering the backflow in the recirculation region is utilized to determine if the coherence of the wake and consequently, the buffet loads can be reduced by flow control. The simulations are performed using a zonal RANS/LES approach. The time-resolved flow field data are analyzed by classical spectral analysis, two-point correlation analysis, and dynamic mode decomposition (DMD). At supersonic freestream conditions, the nozzle counter pressure is reduced by the expansion of the outer flow around the nozzle lip leading to a decreased transition nozzle pressure ratio. In the transonic configuration a spatio-temporal mode with an eigenvalue matching the characteristic buffet frequency of $$Sr_D=0.2$$ is extracted by the spectral and DMD analysis. The spatial shape of the detected mode describes an antisymmetric wave-like undulating motion of the shear layer inducing the low frequency dynamic buffet loads. By flow control this antisymmetric coherent motion is weakened leading to a reduction of the buffet loads on the nozzle fairing.
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Duz, Bulent, Bart Mak, Remco Hageman, and Nicola Grasso. "Real Time Estimation of Local Wave Characteristics from Ship Motions Using Artificial Neural Networks." In Lecture Notes in Civil Engineering, 657–78. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-4680-8_45.
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Garrett, Steven L. "Elasticity of Solids." In Understanding Acoustics, 179–233. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_4.
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Abstract If a solid is initially at rest and equal and opposing forces are applied to that object, Newton’s Second Law guarantees that the object will remain at rest because the net force on the sample is zero. If that object is an elastic solid, then those forces will cause the solid to deform by an amount that is directly proportional to those applied forces. When the forces are removed, the sample will return to its original shape and size. That reversibility is the characteristic that is required if we say the behavior of the solid is “elastic.” This chapter will quantify the elastic behavior of solids by introducing the concepts of stress and strain and expressing their linear relationship through the definition of elastic moduli that depend only upon the material and the nature of the deformation and not upon the shape of the object. Those concepts allow us to generalize Hooke’s law. As before, the combination of a linear equation of state with Newton’s Second Law will now describe wave motion in solids. The introduction of a relaxation time, through the Maxwell model, will let these results be generalized to viscoelastic materials and then be applied to rubber vibration isolators.
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Wu, S., and Y. J. Liu. "Experimental Study on Operation Performance of Two-Body Wave Energy Generator." In Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210282.
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The two-body oscillating type wave energy converter (WEC) is a hot research topic at present. A two-body device with damping disc was taken as the test model in this paper. The two bodies were connected by a hydraulic piston cylinder to realize the relative motion energy conversion. Physical experiments were carried out in a wave-making flume to study the operation performance. The effects of wave elements and load on the hydrodynamic characteristics and capture width ratio (CWR) of the model were analysed respectively. The results showed that wave frequency and external load were the main factors affecting the motion response and energy conversion of the device. With the increase of wave frequency and external load, the response amplitude operator (RAO) and the capture width ratio both increase first and then decrease. Wave height has little effect on system characteristics. There exists a best-matching wave period condition, and the optimal motion response and energy conversion are obtained.
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Chimenti, Dale, Stanislav Rokhlin, and Peter Nagy. "Guided Waves in Plates and Rods." In Physical Ultrasonics of Composites. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780195079609.003.0009.
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In this chapter we consider elastic wave modes which propagate in composites with finite boundaries. There are those waves that exist between the two plane parallel boundaries of a homogeneous anisotropic solid. We consider that well-known problem, as well as waves in an elastic anisotropic rod, specifically an individual graphite fiber. Composite laminates seen in applications are essentially all multilayered structures, and in many cases can be considered periodically layered. So, we also take up the subject of guided waves in layered plates in later chapters. In a plate geometry, as illustrated in Fig. 5.1, we choose the propagation direction to be parallel to the x1 axis and the x3 axis to be normal to the plate surfaces. This geometry is particularly significant for composite materials since, by design, laminates are often locally planar in nature. While the solutions we find are appropriate for flat plates, with some modifications they describe wave motion in gently curved structures as well. Clear and mathematically straightforward descriptions of the characteristics of plate waves exist for isotropic media. The results obtained for isotropic media are not, however, directly applicable to most composites. We begin by considering the behavior of waves in a uniaxial composite laminate. In later chapters we generalize the calculation to layered orthotropic media, concentrating on the results and physical interpretation rather than the algebraic details. To begin a description of waves in plates, let us consider the possible polarizations of particle motion. Let the plate surfaces lie in the (x1, x2) plane of mirror symmetry with the origin dividing the plate thickness in half, as shown in Fig. 5.1. Then, we will at first assume the wave to be uniform in the x2 direction and propagating in the x1 direction, and (x1, x3) is the plane of symmetry. Particle motion can occur along any axis. Note that in this restricted symmetry, shear partial waves polarized along the x2 axis will have no component of particle motion normal to the plate surfaces. Partial waves are a concept introduced by Rayleigh to acknowledge that a superposition of both shear and longitudinal particle motion is generally needed to produce plate waves polarized in the vertical plane.
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Adam, John A. "Morphology-Dependent Resonances: The Effective Potential." In Rays, Waves, and Scattering. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691148373.003.0027.
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This chapter examines the effective potential for morphology-dependent resonances (MDRs). In the cross-section for scattering of electromagnetic energy by a dielectric sphere, a series of sharp peaks that occur as a function of the size parameter can be observed. These peaks are a manifestation of scattering resonances in which electromagnetic energy is temporally trapped inside the particle. These resonances are the MDRs. The chapter first considers the case of a scalar plane wave impinging in the direction θ = 0 on a sphere of radius a before finding the solution of the Schrödinger equation that describes the motion of a particle in the effective potential in the presence of a centrifugal barrier. It also discusses the characteristics that are necessary to define a resonance appropriately.
Тези доповідей конференцій з теми "Wave motion characteristics"
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Deng, Yanfei, Jianmin Yang, and Longfei Xiao. "Influence of Wave Group Characteristics on the Motion of a Semisubmersible in Freak Waves." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23589.
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In the last few decades, the hydrodynamic performance of offshore structures has been widely studied to ensure their safety as well as to achieve an economical design. However, an increasing number of reported accidents due to rough ocean waves call for in-depth investigations on the loads and motions of offshore structures, particularly the effect of freak waves. The aim of this paper is to determine the sea conditions that may cause the maximum motion responses of offshore structures, which have a significant effect on the loads of mooring systems because of their tight relationship. As a preliminary step, the response amplitude operators (RAOs) of a semisubmersible platform of 500 meters operating depth are obtained with the frequency-domain analysis method. Subsequently, a series of predetermined extreme wave sequences with different wave group characteristics, such as the maximum crest amplitude and the time lag between successive high waves, are adopted to calculate the hydrodynamic performance of the semisubmersible with mooring systems in time-domain. The paper shows that the maximum motion responses not only depend on the largest wave crest amplitude but also the time lags between successive giant waves. This paper will provide an important reference for future designs which could consider the most dangerous wave environment.
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Qiu, Zhao-kun, Dong-ze Li, and Wei-dong Jiang. "Study of continuous wave radar for human motion characteristics measurement." In 2010 10th International Conference on Signal Processing (ICSP 2010). IEEE, 2010. http://dx.doi.org/10.1109/icosp.2010.5655886.
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Dhanak, Manhar R., P. Ananthakrishnan, John Frankenfield, and Karl von Ellenrieder. "Seakeeping Characteristics of a Wave-Adaptive Modular Unmanned Surface Vehicle." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-11410.
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Sea-keeping characteristics of a wave-adaptive modular catamaran, developed by Marine Advanced Research Inc., is studied using at-sea experiments and dynamic modeling. The vehicle is based on the Proteus design and is supported by two inflatable pontoons with each pontoon attached to a center payload tray using an independent suspension system connected in such a way that the demi-hulls perform somewhat independent motions through a wave field. The suspension system is designed to isolate the center payload tray from the motions induced by waves incident on the demi-hulls. The vehicle is propelled by two water jets and is capable of achieving speeds of 8–15 knots. Accelerometers have been mounted on the pontoons and the center payload tray of the vehicle and field tests in the open ocean have been carried out to study sea-keeping properties of the vehicle. Heave and surge motions for the cases of following seas, beam seas and head seas have been recorded. In each case the center payload tray is found to experience attenuated heave accelerations compared with the two pontoon hulls. The reductions in surge and sway motion are, however, not evident. The associated spectra suggest that heaving motion of the center payload tray over a range of frequencies is attenuated by the suspension system. No attenuation is apparent in the surge and sway motions. The WAM-V dynamics is modeled as a three-body problem with the pontoons corresponding to bodies 1 and 2, and the central tray to body 3. Results of the analysis are compared with the sea trials.
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Ikoma, Tomoki, Katsuhide Fujishima, Yasuhiro Aida, Tan Lei, and Koichi Masuda. "Motion Characteristics of a Floating Model With Moonpools for VAWTs." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79153.
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Abstract This paper describes motion behaviors of a floating body and water regions of moonpools. The floating model to be focused in this study has moonpools and is for offshore wind turbine system with two vertical axis wind turbines. Motion behaviors of water region in moonpools strongly affect on motion characteristics of a floating body itself. Often the effects lead to non-linear motion of the floating body. Besides, when the floating body is a system of vertical axis offshore wind turbines, the system becomes more complicated. This study conducted theoretical calculations and model experiments in a wave tank. Behaviors of moonpools were measured in regular waves and we measured wave exciting forces, radiation forces on heave and motion responses of the floating model. Also, the study considered effects of Vertical Axis Wind Turbine (VAWT) model’s rotation on the motion. From the results behaviors of moonpools were often nonlinear to incident waves and the behaviors affected on motion responses of the floating model. The experimental results were compared with the calculation results. When non-linearity due to overtopping of water from moonpools was found, the calculations could not reproduce hydro forces but they are able to estimate motion responses. The study confirmed reduction effects due to the moonpools on motion responses comparing with a conventional pontoon with identical displacement.
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Shakeri, Mostafa, Mohammadreza Tavakolinejad, Matthias Mayer, and James H. Duncan. "Characteristics of Breaking Bow Waves Generated by a 2D+T Wave Maker." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98534.
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Ship bow waves simulated experimentally with a 2D+T wave maker were investigated experimentally. Wave profile measurements are presented for a range of equivalent full-scale ship speeds ranging from 16.5 to 27 knots. At the beginning of the wave maker motion, the water surface rises rapidly up the surface of the wave board which represents the hull of the equivalent ship model. The maximum rise height and the rate of rise increase with increasing equivalent ship speed. Later in the wave maker motion, this point of maximum water height moves away from the wave board and forms the primary crest in the wave pattern. This crest moves at a speed that is about 1.8 times the maximum speed of the wave board. At the higher speeds, this wave crest evolves into a strong plunging breaker with a jet that hits the water surface ahead of the breaker, creating a large splash and entraining large amounts of air. The temporal histories of various geometrical characteristics of the breaker are presented.
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Katayama, Toru, Yusuke Yamamoto, Taishi Morimoto, and Masahiro Goto. "Motion Characteristics of a Spar-Buoy With Ring-Fin Motion Stabilizer in Deep Sea." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18595.
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Abstract The main topics of this paper is the investigation of motion characteristics of the spar-buoy with ring fin motion stabilizer, which is developed to use as a platform for wind observation with a doppler lidar in shallow sea, some mooring conditions to apply it for deep sea. Four different mooring conditions are applied the spar-buoy and it motion in a designed sever wave condition are measured in the towing tank of Osaka Prefecture University. The results show that the amplitude of pitching in deep sea is smaller than the results in shallow sea, even if the wave condition in deep sea are severer than that in shallow sea. From further investigation about the effects of four different mooring conditions on motion characteristics, it has that the center of pitching at four mooring conditions are almost same but the amplitude of pitching is smaller by changing the mooring point and the intermediate sinker position.
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Huang, Weigang, Tao He, Jiawei Yu, Qing Wang, and Xianzhou Wang. "Direct CFD Simulation and Experimental Study on Coupled Motion Characteristics of Ship and Tank Sloshing in Waves." In ASME 2021 40th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/omae2021-63775.
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Abstract It is of great significance to study the tank sloshing, especially the coupling motion between tank sloshing and ship in waves with strong non-linearity and randomness. In this study, the response of the ship with/without tank in regular wave is studied by EFD method and CFD method. All the simulations are carried out by in-house CFD code HUST-Ship (hydrodynamic unsteady simulation technology of ship) to solve RANS equations coupled with six degrees of freedom solid body motion equations. RANS equations are solved by finite difference method and PISO algorithm. A two-equation Shear Stress Transport (SST) k-w turbulence model is used. The simulation results are in good agreement with the experimental results, which also indicates that the result of the tank sloshing simulated by in-house CFD code is reliable. The influence of sloshing on ship motions is estimated by comparing the experimental results between the ship with/without tank in different wave conditions. The coupling motion characteristics between the liquid in the tank and the ship is further studied by the CFD method. The study shows that the influence of tank sloshing on ship motion is different under the action of different regular waves.
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Taguchi, Masakazu, and Masashi Kashiwagi. "Experimental Study on a Relation Between Nonlinear Hydrodynamic Forces and Wave-Induced Ship Motions." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95555.
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Abstract Nowadays, in maritime industries, container ships increase in size and they have large flares, which may induce nonlinear wave loads in large-amplitude waves. It is also well known that hydrodynamic forces acting on a ship and resulting ship motions show nonlinearities at some range of wave frequencies. Therefore, we should investigate not only correct estimation of wave loads and ship motions, but also nonlinear ship-motion characteristics in large-amplitude waves. However, it is not that clear which nonlinear hydrodynamic force terms are dominating for the nonlinearity in the ship motions. Although the linear equations of motion have been used, they should be modified to incorporate at least the most important nonlinear hydrodynamic forces and to establish a practical calculation method taking account of only the indispensable nonlinear terms. In this research, we did extensive experimental measurement of hydrodynamic forces and wave-induced ship motions, with which we aim to understand what are practically important nonlinear terms, and to derive practical nonlinear ship motion equations through numerical computation and comparison with experimental data.
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van Dijk, Radboud R. T., Vale´rie Quiniou-Ramus, and Guillaume Le-Marechal. "Comparison of Full-Scale Measurements With Calculated Motion Characteristics of a West of Africa FPSO." In ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2003. http://dx.doi.org/10.1115/omae2003-37182.
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Full-scale measurements of the motions of the Girassol FPSO are available over a one-year period. During this same period also vessel draft, wave height and wave direction have been recorded. This allows the calculation of motion transfer functions as function of the FPSO loading condition. A comparison has been made between the measured motion transfer functions and the calculated motion transfer functions based on diffraction theory, taking into account the measured wave spreading. Viscous roll damping has been added in the calculation to obtain maximum agreement between measured and calculated RAO’s. The results show that wave spreading is a very important factor on how the vessel behaves and should be taken into account when evaluating measured full-scale motion RAO’s. This paper addresses the full-scale monitoring campaign in some detail and the related issues. Furthermore it describes the technique how measured wave spreading is taken into account in the calculation of theoretical motion RAO’s. It is shown that the agreement between calculated and measured RAO’s is greatly improved by the use of measured wave spreading in the calculation. The levels of viscous roll damping found in this tuning process can be described as function of loading condition and sea state. The viscous roll damping found in this process also shows good agreement to model test results performed earlier on this same FPSO.
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Bassler, Christopher C., Vadim Belenky, and Martin J. Dipper. "Characteristics of Wave Groups for the Evaluation of Ship Response in Irregular Seas." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20241.
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A method to evaluate ship response in heavy seas is presented. A ship maneuvering in a stochastic environment is difficult to model because of the rarity and significant nonlinearity of the large motion responses. In the proposed method, critical wave groups are defined and used to separate the complexity of the nonlinear dynamics of ship response from the complexities of a probabilistic description for the response. In this formulation, wave groups may be considered as a possible method to solve the problem of rarity. With the characteristic information about the wave groups, the problem of rarity can be solved in a deterministic manner. Characteristics, including the distributions for the number of waves in a group and wave amplitude, period, and steepness for the waves in a group are presented.