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1
Grue, John. "Ship generated mini-tsunamis." Journal of Fluid Mechanics 816 (March 3, 2017): 142–66. http://dx.doi.org/10.1017/jfm.2017.67.
Повний текст джерелаАнотація:
Very long waves are generated when a ship moves across an appreciable depth change $\unicode[STIX]{x0394}h$ comparable to the average and relatively shallow water depth $h$ at the location, with $\unicode[STIX]{x0394}h/h\simeq 1$. The phenomenon is new and the waves were recently observed in the Oslofjord in Norway. The 0.5–1 km long waves, extending across the 2–3 km wide fjord, are observed as run-ups and run-downs along the shore, with periods of 30–60 s, where a wave height up to 1.4 m has been measured. The waves travelling with the shallow water speed, found ahead of the ships moving at subcritical depth Froude number, behave like a mini-tsunami. A qualitative explanation of the linear generation mechanism is provided by an asymptotic analysis, valid for $\unicode[STIX]{x0394}h/h\ll 1$ and long waves, expressing the generation in terms of a pressure impulse at the depth change. Complementary fully dispersive calculations for $\unicode[STIX]{x0394}h/h\simeq 1$ document symmetries of the waves at positive or negative $\unicode[STIX]{x0394}h$. The wave height grows with the ship speed $U$ according to $U^{n}$ with $n$ in the range 3–4, for $\unicode[STIX]{x0394}h/h\simeq 1$, while the growth in $U$ is only very weak for $\unicode[STIX]{x0394}h/h\ll 1$ (the asymptotics). Calculations show good agreement with observations.
2
Almström, Björn, Magnus Larson, Lars Granath, and Hans Hanson. "SHIP-GENERATED WAVES OVER A COMPLEX BATHYMETRY." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 35. http://dx.doi.org/10.9753/icce.v36.waves.35.
Повний текст джерелаАнотація:
Problems related to shipping have increased worldwide during the last decades as a result of more traffic travel-ling at higher speeds and using larger vessels. When ships move in a restricted fairway they generate primary (drawdown) and secondary (transverse and divergent) waves (Bertram 2000) that often cause adverse impact to adjacent shores. An example of this is the Furusund fairway in Sweden, which since the 1980’s has experienced increased traffic and larger ships. This has resulted in a loss of natural fine sediment habitats along the shores as well as structural damages to piers and jetties (Granath 2015). Furusund is an important fairway into Stockholm, the capital of Sweden, and is located about 25 km north of the city within the Stockholm archipelago. It is mainly trafficked by large ferries (length/width/draft: 200x30x7m). The wind-wave regime in the fairway can be described as a low-energy environment, due to the short fetches and no swell. Hence, ship waves have a significant impact on the shores in terms of bed and bank erosion. This study aims at determining the primary ship wave characteristics and their relationship to ship properties and bathymetric conditions in the Furusund fairway. Measured water levels were collected for this purpose during three months at three locations. Existing empirical formulas for drawdown are evaluated based on the measurements and compared with a new formula derived for the specific fairway. The results are used for designing nature-based protection against ship-generated waves along the shores and to validate analytical and numerical models that can be employed for ship wave generation and propagation.
3
Dong, G. H., L. Sun, Z. Zong, H. W. An, and Y. X. Wang. "Numerical Analysis of Ship-Generated Waves Action on a Vertical Cylinder." Journal of Ship Research 53, no. 02 (June 1, 2009): 93–105. http://dx.doi.org/10.5957/jsr.2009.53.2.93.
Повний текст джерелаАнотація:
In this paper, the action of ship-generated waves on a nearby vertical cylinder is considered in pure theory. Intensive demands of modern sea transportation result in larger and larger ships. These ships generate high waves as they move in calm water. The ship-generated waves can travel long distances without much attenuation. They are so strong that they might cause damage to nearby marine structures (e.g., platforms, river banks, breakwaters, etc.). Therefore, it is necessary to evaluate the forces of ship-generated waves acting on nearby marine structures. The problem turns out to be composed of two problems: evaluation of waves generated by a moving ship (ship-wave problem) and evaluation of the action of ship waves on a cylinder (wave-action problem). Here the wave-action problem is computed in detail with a boundary element method in time domain. And the ship-wave problem is evaluated in the well-known Michell thin-ship theory. Thus, the problem posed in this paper is finally solved using numerical methods by combining the ship-wave and wave-action problems. The numerical analyses of the result are: The resultant forces and moments acting on the cylinder are surprisingly large, characterized by being highly oscillatory. The periods of the oscillations are proportional to ship speed. The actions of ship-generated waves on nearby structures are not negligible. This is a new factor necessary to be considered for design of both marine structures and ships. Meanwhile, the potential fatigue damage resulting from oscillations of the forces and moments should be considered, too.
4
Kashiwagi, Masashi. "Hydrodynamic Study on Added Resistance Using Unsteady Wave Analysis." Journal of Ship Research 57, no. 04 (December 1, 2013): 220–40. http://dx.doi.org/10.5957/jsr.2013.57.4.220.
Повний текст джерелаАнотація:
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.
5
KIMURA, Akihiko, Kei YAMASHITA, and Taro KAKINUMA. "Surf Points Using Ship Generated Waves." Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 69, no. 2 (2013): I_1326—I_1330. http://dx.doi.org/10.2208/kaigan.69.i_1326.
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6
ZHU, QIANG, YUMING LIU, and DICK K. P. YUE. "Resonant interactions between Kelvin ship waves and ambient waves." Journal of Fluid Mechanics 597 (February 1, 2008): 171–97. http://dx.doi.org/10.1017/s002211200700969x.
Повний текст джерелаАнотація:
We consider the nonlinear interactions between the steady Kelvin waves behind an advancing ship and an (unsteady) ambient wave. It is shown that, for moderately steep ship waves and/or ambient waves, third-order (quartet) resonant interaction among the two wave systems could occur, leading to the generation of a new propagating wave along a specific ray in the Kelvin wake. The wave vector of the generated wave as well as the angle of the resonance ray are determined by the resonance condition and are functions of the ship forward speed and the wave vector of the ambient wave. To understand the resonance mechanism and the characteristics of the generated wave, we perform theoretical analyses of this problem using two related approaches. To obtain a relatively simple model in the form of a nonlinear Schrödinger (NLS) equation for the evolution of the resonant wave, we first consider a multiple-scale approach assuming locally discrete Kelvin wave components, with constant wave vectors but varying amplitudes along the resonance ray. This NLS model captures the key resonance mechanism but does not account for the detuning effect associated with the wave vector variation of Kevin waves in the neighbourhood of the resonance ray. To obtain the full quantitative features and evolution characteristics, we also consider a more complete model based on Zakharov's integral equation applied in the context of a continuous wave vector spectrum. The resulting evolution equation can be reduced to an NLS form with, however, cross-ray variable coefficients, on imposing a narrow-band assumption valid in the neighbourhood of the resonance ray. As expected, the two models compare well when wave vector detuning is small, in the near wake close to the ray. To verify the analyses, direct high-resolution simulations of the nonlinear wave interaction problem are obtained using a high-order spectral method. The simulations capture the salient features of the resonance in the near wake of the ship, with good agreements with theory for the location of the resonance and the growth rate of the generated wave.
7
Nascimento, Maria Francisca, Claudio Freitas Neves, and Geraldo De Freitas Maciel. "WAVES GENERATED BY TWO OR MORE SHIPS IN A CHANNEL." Coastal Engineering Proceedings 1, no. 32 (February 2, 2011): 60. http://dx.doi.org/10.9753/icce.v32.waves.60.
Повний текст джерелаАнотація:
The numerical model FUNWAVE+Ship simulates the generation and propagation of ship waves to shore, including phenomena such as refraction, diffraction, currents and breaking of waves. The interaction of two wave trains, generated by ships moving either in the same direction at different speeds or in opposite directions, is studied. Focus is given to the wave orbital velocities and to the free surface pattern.
8
Soomere, Tarmo. "Nonlinear Components of Ship Wake Waves." Applied Mechanics Reviews 60, no. 3 (May 1, 2007): 120–38. http://dx.doi.org/10.1115/1.2730847.
Повний текст джерелаАнотація:
Nonlinear components of wakes from large high-speed ships at times carry a substantial part of the wake energy and behave completely differently compared to the classical Kelvin wave system. This overview makes an attempt to summarize the descriptions of nonlinear parts of a ship’s wake. For completeness, also the basic properties of the Kelvin wake are sketched. The central topic is the generation of solitons by ship motion both in channels and in unbounded sea areas. The discussion is mostly limited to disturbances on the surface of nonstratified water. The optional nonlinear components of the ship wake such as the very narrow V-like wake components, packets of monochromatic waves, ship-generated depression areas, and supercritical bores are also discussed. Specific features of solitonic ship waves and their interactions have numerous applications in naval and coastal engineering, and in adjacent areas of applied mechanics. An overview of the practical use of certain properties of phase shifts, and particularly high wave humps occurring during Mach reflection and nonlinear interaction of solitons in decreasing the wave resistance at supercritical speeds and in the freak wave theory, is also presented. The final part of the paper describes the results of studies of far-field properties of nonlinear wakes and possible consequences of the increase of local hydrodynamic activity. There are 263 references cited in this review article.
9
Zhu, Xing Le, Chang Han Xiao, and Zhen Ning Yao. "Effect of Ship's Motion on Wave-Generated Magnetic Field in Marine Magnetic Survey." Applied Mechanics and Materials 380-384 (August 2013): 228–31. http://dx.doi.org/10.4028/www.scientific.net/amm.380-384.228.
Повний текст джерелаАнотація:
The survey ship would be interfered by wave-generated magnetic field in marine survey. The waves magnetic field is difficult to eliminate because it is the signal in low frequency like ships magnetization field. When survey ship sails, the frequency of waves magnetic field would change. It was found that the frequency has a linear relationship with ships speed and varies in sine or cosine with the angle between ships and waves directions. Ocean waves PSD would be compressed and strong noise of low frequency in narrowband turns up when ship sails in the same direction of waves. The frequency band of PSD would be broadened and small interference occurs while ships direction is opposite. A conclusion can be drawn that survey ship should sail reversely with ocean waves in marine magnetic survey, so the magnetic field induced by ocean waves would extend to high frequency and it is better for noise elimination.
10
Wang, Ping, and Jun Cheng. "Mega-Ship-Generated Tsunami: A Field Observation in Tampa Bay, Florida." Journal of Marine Science and Engineering 9, no. 4 (April 18, 2021): 437. http://dx.doi.org/10.3390/jmse9040437.
Повний текст джерелаАнотація:
The displacement of a large amount of water in a moderate-sized estuary by a fast-moving mega-ship can generate tsunami-like waves. Such waves, generated by cruise ships, were observed in Tampa Bay, Florida, USA. Two distinct, long tsunami-like waves were measured, which were associated with the passage of a large cruise ship. The first wave had a period of 5.4 min and a height of 0.40 m near the shoreline. The second wave had a period of 2.5 min and was 0.23 m high. The peak velocity of the onshore flow during the second wave reached 0.65 m/s. The shorter, second wave propagated considerably faster than the first wave in the breaking zone. The measured wave celerity was less than 50% of the calculated values, using the shallow water approximation of the dispersion equation, suggesting that nonlinear effects play an important role. A fundamental similarity among the generation of tsunamis, as induced by mega-ships, landslides or earthquakes, is a process that causes a vertical velocity at the sea surface, where a freely propagating wave is produced. This mega-ship-generated tsunami provides a prototype field laboratory for systematically studying tsunami dynamics, particularly the strong turbulent flows associated with the breaking of a tsunami wave in the nearshore, and tsunami–land interactions. It also provides a realistic demonstration for public education, which is essential for the preparation and management of this unpreventable hazard.
11
Scragg, Carl A. "Spectral Representation of Ship-Generated Waves in Finite-Depth Water." Journal of Offshore Mechanics and Arctic Engineering 125, no. 1 (February 1, 2003): 65–71. http://dx.doi.org/10.1115/1.1537728.
Повний текст джерелаАнотація:
Recent efforts to compare the waves generated by different vessels traveling in finite-depth water have struggled with difficulties presented by various data sets of wave elevations (either measurements or predictions) corresponding to different lateral distances from the ship. Some of the attempts to shift the data to a common reference location have relied upon crude and potentially misleading approximations. The use of free-wave spectral-methods not only overcomes such difficulties, but is also provides us the means to accurately extend CFD results into the far field. As in the deep-water case, one can define a free-wave spectrum that is valid for all lateral positions and distances astern of the vessel. The free-wave spectrum contains a complete description of the Kelvin wake, and wave elevations at any far-field position can be readily calculated once the spectrum is known. For the case of infinitely deep water, Eggers, Sharma, and Ward [1] presented a method by which free-wave spectra can be determined from appropriate measurements of the far-field wave elevations. The current paper discusses the use of free-wave spectra for finite-depth problems and presents a method for the determination of free-wave spectra based upon fitting predicted wave elevations to a corresponding data set. The predicted wave elevations can be calculated from an unknown distribution of finite-depth Havelock singularities. The unknown singularities are determined by minimizing the mean-square-difference between predicted and measured wave fields. The method appears to be quite general and can be used to calculate either finite or infinite-depth free-wave spectra from experimental data or from local CFD predictions.
12
Fang, M. C., R. Y. Yang, and I. V. Shugan. "Kelvin Ship Wake in the Wind Waves Field and on the Finite Sea Depth." Journal of Mechanics 27, no. 1 (March 2011): 71–77. http://dx.doi.org/10.1017/jmech.2011.9.
Повний текст джерелаАнотація:
ABSTRACTA kinematics model of the ship wake in the presence of surface waves, generated by wind is presented. It was found that the stationary wave structure behind the ship covered a wedge region with the 16.9° half an angle at the top of the wake and only divergent waves are present in a ship wake for co propagating wind waves. Wind waves field directed at some nonzero angle to the ship motion can cause essential asymmetry of the wake and compressing of its windward half. The extension of Whitham-Lighthill kinematics theory of ship wake for the intermediate sea depth is also presented. The ship wake structure essentially depends from the Froude (Fr) number based on the value of the sea depth and ship velocity. For Froude number less than unit both longitudinal and cross waves are presented in the wake region and Kelvin wake angle increased with Fr. For Fr > 1 wake angle decreased with Froude number and finally only divergent waves are presented in the very narrow ship wake.
13
Kimura, Akihiko, Kei Yamashita, and Taro Kakinuma. "SURF POINTS USING A SET OF STRUCTURES TO AMPLIFY SHIP GENERATED WAVES." Coastal Engineering Proceedings 1, no. 34 (October 30, 2014): 51. http://dx.doi.org/10.9753/icce.v34.waves.51.
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14
Yuan, Peiyin, and Yu Zhao. "Analysis and Modelling of Ship Manoeuvring Simulation in Landslide-Generated Waves." Journal of Advanced Transportation 2021 (December 18, 2021): 1–12. http://dx.doi.org/10.1155/2021/5069859.
Повний текст джерелаАнотація:
The geological conditions of the Three Gorges Reservoir Region are complex and changing, and large- and medium-sized landslides are widely distributed. When a high-speed moving landslide enters the water, the water is significantly disturbed, and a landslide-generated wave will be formed, which will spread along the upstream and downstream of the river, causing significant threats and destruction to the hydraulic structures and the navigation of ships. Based on the typical rock landslide parameters and fracture development, we establish a three-dimensional physics experimental model of the bending section of the landslide-generated wave in the Three Gorges Reservoir Region. This paper primarily studies the variation law of the first wave height of landslide-generated waves with the width, height, and water entry velocity of the landslide body and then provides an empirical formula for the first wave height of landslide-generated waves in the curved section of the Three Gorges Reservoir Region. The ship rolling motion equation in the landslide-generated water area is analysed and established systematically. Additionally, the ship manoeuvring motion model in the landslide-generated water area is built. This paper explains the variation characteristics of ship turning tracks at different sailing speeds and sailing positions and proposes a basis to determine the navigation safety of ships in this area, thus providing new theoretical and technical support for the risk assessment of navigation of ships in the reservoir area.
15
Yuan, Pei-yin, Ping-yi Wang, and Yu Zhao. "Physical Modelling of Roll and Pitch Motions of Travelling or Stationary Ship in Large-Scale Landslide-Generated Waves." Advances in Civil Engineering 2020 (July 21, 2020): 1–11. http://dx.doi.org/10.1155/2020/8857604.
Повний текст джерелаАнотація:
Large-scale landslides often occur in river-type reservoirs, and landslide-generated waves affect navigation channels and the navigation of ships. Thus, such waves cause widespread regional disasters. This study establishes a mechanical model of landslide-generated waves via field investigations and data collection, reveals the mechanism and process of landslide-generated waves, and investigates the propagation characteristics of landslide-generated waves along a sloping wave. The feasibility of the model is verified via (i) regularity analysis, (ii) comparative analysis of the effect of landslide-generated waves of mountain river channel reservoirs on the movement characteristics of navigation vessels and stationary vessels, (iii) deviation from the equilibrium position, and (iv) an in-depth study of the influence of large-scale landslide-generated waves on ships in different navigation positions in a river channel. Countermeasures are proposed for a sailing ship to tackle a sudden landslide-generated wave; these measures can provide a theoretical basis for ships to sail safely through large-scale landslide-generated waves.
16
Ouchi, K., N. R. Stapleton, and B. C. Barber. "Multi-frequency SAR images of ship-generated internal waves." International Journal of Remote Sensing 18, no. 18 (December 1997): 3709–18. http://dx.doi.org/10.1080/014311697216568.
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17
Morita, S., T. Sawaragi, I. Deguchi, and S. Okuda. "Symple Neumerical Method of Ship Generated Waves in Marina." PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 11 (1995): 13–18. http://dx.doi.org/10.2208/prooe.11.13.
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18
KUBO, Masayoshi, Katsuhiko SAITO, Shinji MIZUI, Junzou SETO, and Kouji SEIDA. "An Experrimental Study on Simulation of Irregular Waves Using Ship-Generated Waves." Journal of Japan Institute of Navigation 95 (1996): 351–59. http://dx.doi.org/10.9749/jin.95.351.
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19
Sun, L., G. H. Dong, Y. P. Zhao, and C. F. Liu. "Numerical analysis of the effects on a floating structure induced by ship waves." Journal of Ship Research 55, no. 02 (June 1, 2011): 124–34. http://dx.doi.org/10.5957/jsr.2011.55.2.124.
Повний текст джерелаАнотація:
Ship-generated waves can make bad effects on offshore structures. A numerical model is presented for evaluating the forces exerted on a nearby floating structure by ship generated waves. The ship waves were modeled using Michell thin-ship theory (Wigley waves), the forces were computed using a boundary element method in the time domain, and the motions of the offshore structures were evaluated using the equation of motion of the floating body, and predicted using the fourth-order Runge-Kutta method. The numerical method was validated by comparing its results to those of frequency-domain methods reported in the literature. It was then applied to calculate the force of ship waves on a floating box. The ship's speed, dimensions, and distance were varied. The numerical results indicate some useful rules for varying these factors.
20
Chen, X.-B. "Highly oscillatory properties of unsteady ship waves." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 6 (June 1, 2000): 813–23. http://dx.doi.org/10.1243/0954406001523803.
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The singular and highly oscillatory properties of unsteady ship waves are studied by considering potential flows generated by a point source pulsating and advancing at a uniform forward speed located close to or at the free surface. The wave component of the free-surface potential defined by Noblesse and Chen by a single integral along the dispersion curves defined by the dispersion relation is analysed by developing asymptotic expansions of the open dispersion curves at large wave numbers. The asymptotic analysis of the wave component contributed by the leading asymptotic term of a parabolic form shows that unsteady ship waves are highly oscillatory with infinitely increasing amplitude and infinitely decreasing wavelength, when a field point approaches the track of the source point at the free surface. The highly oscillatory property and complex singular behaviour of unsteady ship waves are further expressed in an original and analytically closed form.
21
Zilman, Gregory, and Touvia Miloh. "Kelvin and V-like Ship Wakes Affected by Surfactants." Journal of Ship Research 45, no. 02 (June 1, 2001): 150–63. http://dx.doi.org/10.5957/jsr.2001.45.2.150.
Повний текст джерелаАнотація:
Synthetic aperture radar (SAR) ship wake images in light wind and calm sea conditions frequently appear in the form of a bright V with a half-angle of 2 to 3 deg. Sophisticated and conflicting explanations of this phenomenon, based on the Bragg scattering mechanism, have been proposed. There is a belief that the narrow V-wake is not a part of the Kelvin wake. An alternative approach, which is not generally accepted, suggests that short divergent Kelvin waves may contribute to the V-wake imaging although these waves are mixed with unsteady surface waves generated by the ship-induced turbulence. Ship-generated divergent waves contaminated by surfactants and their radar backscattering cross section are studied. The hull of the ship is represented by a single layer of hydrodynamic singularities. The Green function of a point source moving below a free surface covered by surfactants is derived. A closed-form asymptotic solution for the far ship wave wake is obtained. It is used to calculate analytically the corresponding radar backscattering cross section. The radiative, viscous, and surfactant-induced decay of the V-wake brightness along the V-arms is discussed. The theoretical results are compared against available experimental data.
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Ma, H., and M. P. Tulin. "Experimental Study of Ship Internal Waves—The Supersonic Case." Journal of Offshore Mechanics and Arctic Engineering 115, no. 1 (February 1, 1993): 16–22. http://dx.doi.org/10.1115/1.2920081.
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Internal waves produced by a ship traveling faster than the fastest internal waves (supersonic case) were investigated experimentally in our laboratory in a wide tank using averaging conductivity wave gages developed for this investigation. The wave gage is similar to the conductivity probe, but has space-averaging electrodes. An array of seven such gages was used in a wave tank with dimensions 12 ft length, 8 ft width, 2 ft depth. The water in the tank was stratified with salt to obtain desired density distributions. A spheroid, split vertically, was towed against and along a sidewall to simulate a moving ship. Simultaneous wave profiles at various distances normal to the track of the ship were obtained for different Froude numbers and density distributions. The internal wave patterns were calculated from the measured data and compared with theoretical results. The amplitude on the first crest of the internal wave field is also plotted against the distance from the ship, and a limited comparison with theory is made. The experimental method developed for this study is sensitive, simple and reliable. It may serve to obtain a data base for ship-generated internal waves under a variety of conditions.
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Wu, Ming, Ai Guo Shi, Zuo Chao Wang, Xiao Wang, and Rong Rong Ying. "Numerical Research on Ship Motions in Oblique Irregular Waves." Advanced Materials Research 712-715 (June 2013): 1531–34. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.1531.
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A 3D viscous numerical wave tank (NWT) was established based on computational fluid dynamics simulation method, and oblique irregular waves were generated by defining inflow boundary conditions. The motions of free surface ship in oblique waves were predicted by solving the Reynolds Averaged NavierStokes (RANS) equations describing the flow around ship. The kinematics equations of rigid body were solved according to the calculation results (forces and moments) in each time step. The heave, roll and pitch transfer functions for container ship model S175 in oblique waves were obtained. The comparisons between simulation results and linear strip theoretical results were carried out, showing good agreement, which demonstrate the present research can provide an effective way to predict seakeeping characteristics.
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Bu, Minsheng, Yiping Li, Jin Wei, and Chunyan Tang. "The Influence of Ship Waves on Sediment Resuspension in the Large Shallow Lake Taihu, China." International Journal of Environmental Research and Public Health 17, no. 19 (September 27, 2020): 7055. http://dx.doi.org/10.3390/ijerph17197055.
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Sediment resuspension induces endogenous nutrient release in shallow lakes, which has been demonstrated to be associated with eutrophication. In addition to natural wind-driven resuspension, navigable shallow lakes (such as Lake Taihu, China) also experience resuspension from human activities, such as ship waves. Both processes determine the intensity, frequency, and duration of sediment resuspension, and may consequently affect the pattern of cyanobacteria blooms in the lake. In this study, acoustic Doppler Velocimeter (ADV), Optical Backscatter Sensor (OBS), and temperature wave tide gauge (instrument model :RBR duo TD|wave) were placed in an observation platform in the lake to obtain high-frequency flow velocities, suspended sediment concentration (SSC), and wave parameters before, during, and after a cargo ship passed by. We found that the ship wave disturbance intensity is greatly influenced by the draft depth. The movement generated by ship disturbance is primarily horizontal rather than vertical. Compared with the wind-induced wave, the disturbance caused by the ship waves has a high intensity, short duration, and narrow range of influence. The maximum total shear stress under ship disturbance can reach 9~90 times the critical shear stress under a natural state. Therefore, the effect of ship waves on sediment resuspension near the channel of Lake Taihu is much greater than that of wind-induced waves. These findings represent an important step towards understanding the quantitative relationship between ship wave disturbance and sediment resuspension, and lay the foundation for future research in order to understand and control the eutrophication of shallow lakes.
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Griffin, Owen M. "Ship Wave Modification by a Surface Current Field." Journal of Ship Research 32, no. 03 (September 1, 1988): 186–93. http://dx.doi.org/10.5957/jsr.1988.32.3.186.
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One potential contribution to the formation of the narrow-V patterns observed remotely in the wakes of surface ships is discussed. This is the interaction between the ship-generated waves and a surface current pattern in the ship's wake. This surface current field in turn is primarily a manifestation of the turbulent wake caused by the passage of the ship itself. It can be shown by means of relatively simple theoretical arguments that such an interaction can lead directly to a V-wake pattern which is included within a smaller angular region than that of the classical Kelvin waves produced by the steady motion of a surface ship in still water. Predictions of V-wake patterns are obtained which are in qualitative agreement with some of the recently observed ship wakes.
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SADAKANE, Hiroyuki, Shinnzou NISHINDAI, and Norio YUDA. "An Experimental Study on Oscillations of a Small-Ship Due to Ship-Generated Waves." Journal of Japan Institute of Navigation 91 (1994): 79–88. http://dx.doi.org/10.9749/jin.91.79.
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NOBLESSE, FRANCIS, GÉRARD DELHOMMEAU, MICHEL GUILBAUD, DANE HENDRIX, and CHI YANG. "Simple analytical relations for ship bow waves." Journal of Fluid Mechanics 600 (March 26, 2008): 105–32. http://dx.doi.org/10.1017/s0022112008000220.
Повний текст джерелаАнотація:
Simple analytical relations for the bow wave generated by a ship in steady motion are given. Specifically, simple expressions that define the height of a ship bow wave, the distance between the ship stem and the crest of the bow wave, the rise of water at the stem, and the bow wave profile, explicitly and without calculations, in terms of the ship speed, draught, and waterline entrance angle, are given. Another result is a simple criterion that predicts, also directly and without calculations, when a ship in steady motion cannot generate a steady bow wave. This unsteady-flow criterion predicts that a ship with a sufficiently fine waterline, specifically with waterline entrance angle 2αE smaller than approximately 25°, may generate a steady bow wave at any speed. However, a ship with a fuller waterline (25°<2αE) can only generate a steady bow wave if the ship speed is higher than a critical speed, defined in terms of αE by a simple relation. No alternative criterion for predicting when a ship in steady motion does not generate a steady bow wave appears to exist. A simple expression for the height of an unsteady ship bow wave is also given. In spite of their remarkable simplicity, the relations for ship bow waves obtained in the study (using only rudimentary physical and mathematical considerations) are consistent with experimental measurements for a number of hull forms having non-bulbous wedge-shaped bows with small flare angle, and with the authors' measurements and observations for a rectangular flat plate towed at a yaw angle.
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Shi, Fengyan, Young-Kwang Choi, Matt Malej, Jane M. Smith, and James T. Kirby. "BOUSSINESQ MODELING OF SHIP-WAKES AND THEIR CONTRIBUTION TO COASTAL EROSION IN AN ADAPTIVE MESH REFINEMENT SYSTEM." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 25. http://dx.doi.org/10.9753/icce.v36.waves.25.
Повний текст джерелаАнотація:
Heavy ship traffic causes a growing concern with respect to public safety, potential damage of coastal structures, and corresponding environmental impacts. High-speed ship-generated wakes such as solitons, undular bores, and breaking bores behave differently compared to wind waves and have a great potential for damage in vulnerable areas such as low-energy coasts and wetlands. In this study, we are developing a multi-grid model framework for the Fully Nonlinear Boussinesq Wave Model, FUNWAVE-TVD (Shi et al., 2012), for simulating ship-wakes in both the operational scale and refined process scales using full two-way coupling. Physical processes in areas of interest requiring higher model resolution, such as the ship-wake generation region, wave breaking in the near-field, and wave evolution with wave-structure interaction in the nearshore field, will be modeled in refined grids embedded in the operational-scale domain. A dynamically adaptive grid algorithm is implemented in order to track a vessel and calculate the physical processes precisely in the wave generation and breaking region in the vicinity of the vessel. Both pressure source and panel source methods for ship wave generation will be tested in the model framework. A concept of nesting layers based on the hierarchical basis, and an efficient parallelization method in the context of the full domain partition are utilized to allow the model to deal with a large-scale computation efficiently in a High Performance Computing (HPC) system.
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HONDA, Keinosuke, and Hiroyuki SADAKANE. "Model Experiments on Rolling of Boat in Ship-generated Waves." Journal of Japan Institute of Navigation 83 (1990): 169–76. http://dx.doi.org/10.9749/jin.83.169.
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Pinheiro, Liliana, Joana Simão, João Alfredo Santos, and Conceição Juana Fortes. "Ship Movements’ Analysis in a Physical Scale Model." Defect and Diffusion Forum 372 (March 2017): 132–41. http://dx.doi.org/10.4028/www.scientific.net/ddf.372.132.
Повний текст джерелаАнотація:
A set of physical model tests was run in to characterize the ship’s response to different wave conditions going from frequently-occurring conditions up to extreme ones. Several wave heights, periods and directions were generated. The waves around the ship were measured with probes and the movements of the ship were measured with a fiber-optic gyrocompass. Transfer functions are established and compared with numerical ones obtained with the WAMIT model.
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Tings, Björn. "Non-Linear Modeling of Detectability of Ship Wake Components in Dependency to Influencing Parameters Using Spaceborne X-Band SAR." Remote Sensing 13, no. 2 (January 6, 2021): 165. http://dx.doi.org/10.3390/rs13020165.
Повний текст джерелаАнотація:
The detection of the wakes of moving ships in Synthetic Aperture Radar (SAR) imagery requires the presence of wake signatures, which are sufficiently distinctive from the ocean background. Various wake components exist, which constitute the SAR signatures of ship wakes. For successful wake detection, the contrast between the detectable wake components and the background is crucial. The detectability of those wake components is affected by a number of parameters, which represent the image acquisition settings, environmental conditions or ship properties including voyage information. In this study the dependency of the detectability of individual wake components to these parameters is characterized. For each wake component a detectability model is built, which takes the influence of incidence angle, polarization, wind speed, wind direction, sea state (significant wave height, wavelength, wave direction), vessel’s velocity, vessel’s course over ground and vessel’s length into account. The presented detectability models are based on regression or classification using Support Vector Machines and a dataset of manually labelled TerraSAR‑X wake samples. The considered wake components are: near‑hull turbulences, turbulent wakes, Kelvin wake arms, Kelvin wake’s transverse waves, Kelvin wake’s divergent waves, V‑narrow wakes and ship‑generated internal waves. The statements derived about wake component detectability are mainly in good agreement with statements from previous research, but also some new assumptions are provided. The most expressive influencing parameter is the movement velocity of the vessels, as all wake components are more detectable the faster vessels move.
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Du, Peng, Abdellatif Ouahsine, Philippe Sergent, Yannick Hoarau, and Haibao Hu. "Investigation on Resistance, Squat and Ship-Generated Waves of Inland Convoy Passing Bridge Piers in a Confined Waterway." Journal of Marine Science and Engineering 9, no. 10 (October 14, 2021): 1125. http://dx.doi.org/10.3390/jmse9101125.
Повний текст джерелаАнотація:
The average and unsteady hydrodynamics of an inland convoy passing bridge piers in a confined waterway were investigated using both numerical and experimental approaches. The numerical simulations are realized by solving the RANS (Reynolds-averaged Navier–Stokes) equations accounting for the solid body motion using the sliding mesh technique, while the experiments were carried out in the towing tank. The advancing resistance, trim, sinkage and ship-generated waves were analyzed as functions of the water depth, distance between bridge piers, draught and velocity. The existence of the piers is found to only influence the transient hydrodynamics of the convoy, but not the averaged properties. The ship-generated waves, especially the wave profiles at a specific lateral position, were characterized. Two wave crests exist at the pier position because of the additional reflections, creating a very complex wave pattern in the confined waterway.
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Armudi, A., W. C. Marques, and P. H. Oleinik. "ANALYSIS OF SHIP BEHAVIOR UNDER INFLUENCE OF WAVES AND CURRENTS." Revista de Engenharia Térmica 16, no. 2 (December 31, 2017): 18. http://dx.doi.org/10.5380/reterm.v16i2.62206.
Повний текст джерелаАнотація:
The most important environmental factors related to safety of ship and performance on high sea are surface winds and waves. In order to obtain an optimal trajectory of a ship route, it is a prerequisite to know the sea state condition, as well as, the behavior of the ship in waves and currents. The purpose of this study is to analyze the ship behavior under the influence of 3 different sea state conditions over the Southern Brazilian inner shelf near the Rio Grande coastal region. SHIPMOVE and TOMAWAC + TELEMAC3D system were simulated under three different wave scenarios. Day 4 showed the shortest traveled distance and lowest velocity. The sea state of Day 33 deflected the initial vessel path northeasterly and generated high rotational motions. Day 100 depicted the longest final displacement and highest average velocity, where this event showed the most smooth sea state condition. Lastly, the ship behavior seems to be strongly influenced by the sea state condition for the three events.
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Kilner, F. A. "MODEL TESTS ON THE MOTION OF MOORED SHIPS PLACED ON LONG WAVES." Coastal Engineering Proceedings 1, no. 7 (January 29, 2011): 40. http://dx.doi.org/10.9753/icce.v7.40.
Повний текст джерелаАнотація:
The equation of motion for a moored ship, subject to stationary wave action, is presented and discussed. The moorings are longitudinal, the ship is considered to be aligned to the direction of wave motion and positioned at a node, and the wave length is assumed long compared with the ship length. If the motion of the ship is assumed to be simple harmonic, and frictional forces between the ship and the water are neglected, an elementary analysis gives the required relation between the amplitudes of the ship's movement and of the water particle motion associated with the wave, A description is given of some tests carried out on model ships moored in a flume where stationary waves can be generated, and the amplitude and period can be varied independently. In these experiments, the amplitude of ship movement could be measured visually, or inferred from strain gauge readings, and the water motion was also observed. The results of these tests are compared with the simple theory. A table tilting harmonically is shown to be a mechanical analogy to stationary wave action on ships. The hydrodynamic mass for a ship moving in surge or sway motion is measured and is found to depend on the depth of water in which the ship is moored.
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Agarwal, Arpit, Scott Fenical, Kirsten McElhinney, Paul Carangelo, and David Krams. "ANALYSIS OF HIGH FREQUENCY BREAKING WAVES AND LOW FREQUENCY SURGES GENERATED IN HARBORS DUE TO PASSAGE OF DEEP-DRAFT TANKERS." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 27. http://dx.doi.org/10.9753/icce.v36.waves.27.
Повний текст джерелаАнотація:
Cline’s Point Marina, located in Port Aransas, TX, has been experiencing detrimental conditions near the marina’s entrance and within the marina itself during the passage of deep-draft ship traffic. The wave activity is primarily generated by pressure field effects from large, laden outbound vessels in Corpus Christi Ship Channel (CCSC). The basin was originally protected by an approximately 180 ft. long breakwater constructed in 1976 on the west side of the entrance which by 1980 has deteriorated and partially failed to 120 ft. long breakwater and continued deteriorating over time, reaching its approximate 60 ft. long current condition by 2003. The deterioration of this breakwater has reportedly resulted in enhanced penetration of deep-draft vessel wave activity into the marina (Figure 1). Mott MacDonald (MM) evaluated the mechanisms by which waves are generated in the navigation channel, transform, and enter the harbor, quantified the level of protection afforded by past and present entrance breakwater configuration(s), and developed conceptual alternatives for improving conditions inside the marina.
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Yuan, Peiyin, Pingyi Wang, and Yu Zhao. "A Novel Experiment to Study the Roll Motion Characteristics of a Sailing Ship in a Landslide-Generated Wave in the Three Gorges Reservoir." Advances in Civil Engineering 2019 (July 2, 2019): 1–10. http://dx.doi.org/10.1155/2019/3240812.
Повний текст джерелаАнотація:
Strong earthquakes, heavy rains, changes in reservoir water levels, and other external factors destabilize large rock masses causing them to fall into the water at high speed, thereby destroying the original ecological balance in the region. These occurrences cause fluctuations in water levels and form landslide-induced waves, which behave similar to tsunamis upon reaching the shore, a dam structure, or ships. The impact invariably threatens residents’ lives and properties in the upper and lower reaches of the reservoir area. In the current study, we conducted orthogonal experiments of landslide-induced impulse waves to assess their related hazards. To explore the effects of a landslide-generated wave on the roll characteristics of a ship, experimental model tests were performed using different speed vessels, landslide bodies, and navigation positions. Accordingly, a reasonable optimization strategy was proposed to provide technical support for ship navigation safety in regions of landslide-generated waves.
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Jensen, Peter Schjeldahl. "On the Numerical Radiation Condition in the Steady-State Ship Wave Problem." Journal of Ship Research 31, no. 01 (March 1, 1987): 14–22. http://dx.doi.org/10.5957/jsr.1987.31.1.14.
Повний текст джерелаАнотація:
The waves created by a thin ship sailing in calm water are examined. The velocity potential of the ship in the zero Froude number case is known and the additional potential due to the waves is calculated by the Green function technique. The simple Green function corresponding to the Rankine source potential is used here. Two major problems exist with this method. In the Neumann-Poisson boundary-value problem- probably the first iteration toward a full nonlinear solution to the ship wave problem _it is necessary to impose a radiation condition in order to get uniqueness. This problem is related to the second one, which arises due to the existence of eigensolutions. The two-dimensional situation is here analyzed first, thereby easing the three-dimensional analysis. A numerical scheme is constructed and results for the twodimensional waves generated by a submerged vortex and for the three-dimensional waves due to the Wigley hull are presented.
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Muscari, Roberto, and Andrea Di Mascio. "Numerical modeling of breaking waves generated by a ship?s hull." Journal of Marine Science and Technology 9, no. 4 (December 2004): 158–70. http://dx.doi.org/10.1007/s00773-004-0182-x.
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Grelowska, Grażyna, Eugeniusz Kozaczka, Sławomir Kozaczka, and Wojciech Szymczak. "Underwater Noise Generated by a Small Ship in the Shallow Sea." Archives of Acoustics 38, no. 3 (September 1, 2013): 351–56. http://dx.doi.org/10.2478/aoa-2013-0041.
Повний текст джерелаАнотація:
Abstract Study of the sea noise has been a subject of interest for many years. The first works in this scope were published at the turn of the twentieth century by Knudsen (Knudsen et al., 1948) and G. Wenz (Wenz, 1962). Disturbances called “shipping noise” are one of the important components of the sea noise. In this work the results of an experimental research of underwater noise produced by a small ship of a classic propulsion are presented. A linear receiving antenna composed of two orthogonal components was used in the investigation. Identification of the main sources of acoustic waves related with the ship was achieved. In addition, the intensity of the wave was measured. The research was performed in conditions of the shallow sea.
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Manea, Grei. "The influence of the cruise speed on the amplitude of the oscillatory movements of the ship - OCTOPUS software-assisted study." Scientific Bulletin of Naval Academy XXIII, no. 1 (July 15, 2020): 76–81. http://dx.doi.org/10.21279/1454-864x-20-i1-010.
Повний текст джерелаАнотація:
In their current activity, the officers on board of the ships are interested in the practical ways by which, the complications generated by the sea waves can be overcome and the ship can be safely operated. The paper present a computer-assisted study of the characteristics that define the behaviour of the ship under real navigation conditions (amplitudes of the oscillatory movements, energy spectrum of the ship response to the action of the sea waves) depending on the cruise speed of the ship. OCTOPUS was used as a working tool.
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Noblesse, Francis, Gérard Delhommeau, Patrick Queutey, Chi Yang, and Hyun Yul Kim. "Analytical bow waves for fine ship bows with rake and flare." Journal of Ship Research 55, no. 01 (March 1, 2011): 1–18. http://dx.doi.org/10.5957/jsr.2011.55.1.1.
Повний текст джерелаАнотація:
The bow wave generated by a steadily advancing ship is considered for a family of fine ruled ship bows with rake and flare. This family of ship bows is defined in terms of four parameters: the ship draft D, the entrance angles a and a' at the top and bottom waterlines, and the rake angle 8. The corresponding bow wave similarly depends on four parameters: the draft-based Froude number F and the three angles a, a', and 8. An extensive parametric study, based on thin-ship theory, is performed to explore the variations of the water height Z0 at the ship stem X = 0, the location X0 (measured from the ship stem) of the intersection of the bow-wave profile with the mean free-surface plane Z = 0, and the bow-wave profile, with respect to the four parameters F, a, a', and 8. This parametric study extends the previously reported similar study of the height Zb of the bow wave and the location Xb of the bow-wave crest. These two complementary parametric studies yield simple analytical relations, which extend relations given previously for wedge-shaped ship bows without rake or flare. In spite of their remarkable simplicity, the analytical relations given here yield bow waves that are comparable to computational fluid dynamics (CFD) waves given by Euler-flow calculations. The analytical relations, which explicitly account for the influence of the four primary parameters F, a, a', and 8, can be used immediately—without hydrodynamic calculations—for ship design, notably at early design stages when the precise hull geometry is not yet known. The study also provides insight for ship bow design. Specifically, it suggests that a bow with positive rake and negative flare may be beneficial, and that a bulb located aft of the stem and integrated with the hull may be an advantageous alternative to a traditional bulb protruding ahead of the bow, in agreement with the results of a hull-form optimization analysis.
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Бимбереков, Павел, and Pavel Bimberekov. "GRAPHICAL ANALYSIS OF FREE-SURFACE WAVE FIELDS FROM MOVING SHIPS AND A PAIR OF CONSECUTIVE POSTS." Vestnik of Astrakhan State Technical University. Series: Marine engineering and technologies 2019, no. 4 (November 15, 2019): 7–22. http://dx.doi.org/10.24143/2073-1574-2019-4-7-22.
Повний текст джерелаАнотація:
The paper presents a comparison of the photographic material of the wave patterns resulted from the movement of a ship in situ and a model ship, as well as from two consecutive posts, their regularities being found through graphical processing. The possibility to find the fore imaginary source of Kelvin wave pattern forming the ship's wave system is given at a distance
of one wavelength before the top of the bow retaining wave. The equality of the length of trans-verse waves and divergent waves along the outer boundaries of the latter zone is fixed. It has been assumed that the intermediate waves generated between the main waves in the model ship and the posts are regular, imposition of wave patterns in a pair of consistently moving racks depending on the hit of the rear rack in the wave field of the first rack has been stated. Regularly occurring flows around moving posts are discussed. The bow and stern system of Kelvin waves in a ship wave sys-tem has been illustrated (the angle of the midpoint of diverging wave crests with the ship’s diamet-rical plane and the angle of diverging wave crests with the ship’s diametrical plane). The photo-graphs presented were taken in the experimental tank of Siberian State University of Water Transport (Novosibirsk State Academy of Water Transport) in 2006. A thin film naturally generat-ed on the water surface of the experimental tank and given a structure directed along the tank due to previous runs helped to visualize the distortion of the free water surface in better quality and to obtain clearly outlined contours in lighting.
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Tulin, Marshall P., Yitao Yao, and Pei Wang. "The Generation and Propagation of Ship Internal Waves in a Generally Stratified Ocean at High Densimetric Froude Numbers, Including Nonlinear Effects." Journal of Ship Research 44, no. 03 (September 1, 2000): 197–227. http://dx.doi.org/10.5957/jsr.2000.44.3.197.
Повний текст джерелаАнотація:
A nonlinear theory for internal wave generation and propagation is derived here for slender ships traveling at high densimetric Froude number (Fh >> 1) in water of small density variation. It is based on an asymptotic equation for the evolution of the internal wave vorticity generated under the ship by a known inviscid ship flow and then self-propagating in the wake. In its numerical implementation, arbitrary pycnoclines and slender ship hulls may be used, and boundary conditions on the ship hull are satisfied; the free surface is treated here as rigid, although this may be relaxed. The theory has been implemented by a suitable numerical method and numerous simulations have been carried out. The results have been compared with earlier OEL experiments. In the near field, emphasis is given to a triple-lobe pattern in the pycnocline, an upwelling along the centerline of motion with a trough on either side, forming close behind the ship. Two distinct types of triple lobes are identified:dominant central lobe and very weak troughs, and;weak central lobe and dominant troughs. The former (a) is shown to result in linear propagation into the far field. The latter (b) results in far-field patterns preceded by a deep trough whose propagation is nonlinear. The comparisons of both simulated trends and actual amplitudes with measurements are good, surprisingly so considering the small scale of the experiment and the asymptotic nature of the theory. The effect of the turbulent wake on the internal waves in the experiments is restricted to a very narrow region behind the ship; the bulk of the wave pattern including the leading waves seem unaffected. Simulations show that under certain conditions of stratification, triple-lobe patterns with abnormally large troughs are generated and lead to strong nonlinear effects; these deep troughs propagate sidewards to large distances aft (over 40 ship lengths) with slow decay, and result in much larger surface currents and strain rates than in the normal case. Correspondingly, fast waves of depression, which decay slowly, were discovered through the simulation of two-dimensional initial value problems, where the initial area of depression was significantly less than required of a true soliton; these "quasi-solitons" are briefly studied here.
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Cheng, Yong, Chunyan Ji, Gangjun Zhai, and Gaidai Oleg. "Nonlinear analysis for ship-generated waves interaction with mooring line/riser systems." Marine Structures 59 (May 2018): 1–24. http://dx.doi.org/10.1016/j.marstruc.2017.12.011.
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Aoki, Shin-ichi, and Tom Sawaragi. "Resonant Oscillation of a Moored Floating Body due to Ship-Generated Waves." PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 10 (1994): 295–300. http://dx.doi.org/10.2208/prooe.10.295.
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Milgram, Jerome H. "Theory of Radar Backscatter from Short Waves Generated by Ships, with Application to Radar (SAR) Imagery." Journal of Ship Research 32, no. 01 (March 1, 1988): 54–69. http://dx.doi.org/10.5957/jsr.1988.32.1.54.
Повний текст джерелаАнотація:
In calm conditions, synthetic aperture radar (SAR) ship wake images have the form of a bright "V," typically with a half-angle between 2 and 5 deg. The images sometimes persist for many miles behind the ship and are more likely to be obtained if the ship is traveling close to the azimuth direction of the radar than if it is traveling close to the range direction. Here it is shown that Bragg scattering from ship-generated diverging waves is consistent with observed images. Methods of calculating radar scattering cross sections for "idealized" conditions are developed and examples from their use are presented.
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Liu, Zhiquan. "Adaptive Sliding Mode Control for Ship Autopilot with Speed Keeping." Polish Maritime Research 25, no. 4 (December 1, 2018): 21–29. http://dx.doi.org/10.2478/pomr-2018-0128.
Повний текст джерелаАнотація:
Abstract The paper addresses an important issue in surface vessel motion control practice that the ship dynamics and sailing performance can be affected by speed loss. The vessel speed is significantly decreased by the added resistance generated by waves. An adaptive sliding mode course keeping control design is proposed which takes into account uncertain ship dynamics caused by forward speed variations, while avoiding performance compromises under changing operating and environmental conditions. The sliding mode control provides robust performance for time-varying wave disturbances and time-varying changes in ship parameters and actuator dynamics. After combining the unknown but bounded system uncertainties, the design of the adaptation law is obtained which is based on the Lyapunov’s direct method. Simulations on a ship with two rudders illustrate the effectiveness of the proposed solution.
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Hermans, A. J., and F. J. Brandsma. "Nonlinear Ship Waves at Low Froude Number." Journal of Ship Research 33, no. 03 (September 1, 1989): 176–93. http://dx.doi.org/10.5957/jsr.1989.33.3.176.
Повний текст джерелаАнотація:
The wave pattern of a thick ship-like object with finite bow and stern angles 0 <β<π/2 is studied. The completely blunt form p = π/2 is excluded. It turns out that the wave pattern is strongly influenced by the nonlinear terms at the free surface. The wave pattern is determined by means of the ray method. The rays are generated mainly at the bow and the stern. A crucial step is the determination of the so-called excitation coefficients. They are constructed by means of an asymptotic evaluation of a distribution of "local"sources at the free surface. It is shown that for small angles β<< 1 the excitation coefficients are the same as the ones obtained by means of an asymptotic expansion for small values of the Froude number of the results of Michell's thin-ship theory. For increasing values of β, the excitation coefficients change asymptotically. The theory herein shows a continuous dependence, nevertheless. Similar changes are observed in the far-field wave pattern.
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Liu, Yingfei, and Ruru Deng. "Ship Wakes in Optical Images." Journal of Atmospheric and Oceanic Technology 35, no. 8 (August 2018): 1633–48. http://dx.doi.org/10.1175/jtech-d-18-0021.1.
Повний текст джерелаАнотація:
AbstractShip wakes are more distinct than the hulls and can be visually observed in optical images. In this paper the wakes of 2836 ships in 32 optical images with different resolutions are observed and summarized. The ships are divided into four types according to the hull and wake features: fishing vessels, motorboats, cargo ships, and warships. The results show that each ship type has characteristic wakes, and there are significant differences among the categories. The probabilities of occurrence of different types of wakes and their components are shown. Turbulent wakes are inevitable. The probability of occurrence of Kelvin wakes is small and less than 40%. The visibilities of internal waves that are generated by only cargo ships are very low as a result of the harsh formation conditions. Turbulent wakes should be preferentially detected. Low-resolution images are more suitable for the detection and positioning of hulls and wakes, while high-resolution images with more details are convenient for further analysis of the size, velocity, and draft of ships. The study on the cause of the formation of the features of ship wakes in optical images proves that the classification of the wakes is reasonable and that the features of wakes can be used to initially identify the type of ship.
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Nece, Ronald E., Michael R. McCaslin, Derald R. Christensen, and Harry H. Yeh. "FERRY WAVE MEASUREMENTS IN DEEP WATER." Coastal Engineering Proceedings 1, no. 20 (January 29, 1986): 46. http://dx.doi.org/10.9753/icce.v20.46.
Повний текст джерелаАнотація:
Data are presented for ship waves generated and measured in deep water. Results show the variation of maximum vessel waves with both vessel speed and distance from the vessel sailing line. Three automobile ferries of different configurations were tested. Field test procedures, limitations, and problems are described.