Academic literature on the topic 'Ship-generated waves'
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Journal articles on the topic "Ship-generated waves"
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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It is known that the added resistance in waves can be computed from ship-generated unsteady waves through the unsteady wave analysis method. To investigate the effects of nonlinear ship-generated unsteady waves and bluntness of the ship geometry on the added resistance, measurements of unsteady waves, wave-induced ship motions, and added resistance were carried out using two different (blunt and slender) modified Wigley models. The ship-generated unsteady waves are also produced by the linear superposition using the waves measured for the diffraction and radiation problems and the complex amplitudes of ship motions measured for the motion-free problem in waves. Then a comparison is made among the values of the added resistance by the direct measurement using a dynamometer and by the wave analysis method using the Fourier transform of measured and superposed waves. It is found that near the peak of the added resistance where ship motions become large, the degree of nonlinearity in the unsteady wave becomes prominent, especially at the forefront part of the wave. Thus, the added resistance evaluated with measured waves at larger amplitudes of incident wave becomes much smaller than the values by the direct measurement and by the wave analysis with superposed waves or measured waves at smaller amplitude of incident wave. Discussion is also made on the characteristics of the added resistance in the range of short incident waves.
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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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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.
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We consider the nonlinear interactions between the steady Kelvin waves behind an advancing ship and an (unsteady) ambient wave. It is shown that, for moderately steep ship waves and/or ambient waves, third-order (quartet) resonant interaction among the two wave systems could occur, leading to the generation of a new propagating wave along a specific ray in the Kelvin wake. The wave vector of the generated wave as well as the angle of the resonance ray are determined by the resonance condition and are functions of the ship forward speed and the wave vector of the ambient wave. To understand the resonance mechanism and the characteristics of the generated wave, we perform theoretical analyses of this problem using two related approaches. To obtain a relatively simple model in the form of a nonlinear Schrödinger (NLS) equation for the evolution of the resonant wave, we first consider a multiple-scale approach assuming locally discrete Kelvin wave components, with constant wave vectors but varying amplitudes along the resonance ray. This NLS model captures the key resonance mechanism but does not account for the detuning effect associated with the wave vector variation of Kevin waves in the neighbourhood of the resonance ray. To obtain the full quantitative features and evolution characteristics, we also consider a more complete model based on Zakharov's integral equation applied in the context of a continuous wave vector spectrum. The resulting evolution equation can be reduced to an NLS form with, however, cross-ray variable coefficients, on imposing a narrow-band assumption valid in the neighbourhood of the resonance ray. As expected, the two models compare well when wave vector detuning is small, in the near wake close to the ray. To verify the analyses, direct high-resolution simulations of the nonlinear wave interaction problem are obtained using a high-order spectral method. The simulations capture the salient features of the resonance in the near wake of the ship, with good agreements with theory for the location of the resonance and the growth rate of the generated wave.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
Dissertations / Theses on the topic "Ship-generated waves"
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鄭耀煥 and Yiu-woon Cheng. "Boundary effect on ship-generated waves." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31215063.
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Cheng, Yiu-woon. "Boundary effect on ship-generated waves /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19669215.
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Armesto, Alvarez Jose Antonio. "Towards the numerical simulation of ship-generated waves using a Cartesian cut cell-based free surface solver." Thesis, Manchester Metropolitan University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502440.
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The Cartesian Cut Cell method has been applied to different flow configurations by researchers at the Centre of Mathematical Modelling and Flow Analysis. This method has been implementer to define flow domains around obstacles using a Godunov-type high order upwind scheme to solve Shallow Water Equations and Navier-Stokes (Euler) equations in two phase flows. A new idea to study Navier-Stoke (Euler) equations in just one phase flows where the domain is accurate described using the Cartesian Cut Cell Method around the moving free surface is presented. The solution technique involves three stages for every time step: the definition of the domain, the solution of the flow equations and the movement of the free surface. The Cartesian Cut Cell Method only requires to recompute cells affected by the movement of the free surface obtaining providing quickly the new domain. The flow equations are solved using the Artificial Compressibility Method and a Godunov-type high order upwind scheme involving the solution of Riemann problems. The Heigh Function method is applied to study the evolution on time of the free surface. This method involves the solution of the kinematic equations, where a fourth order Runge-Kutta method is employed. Boundary conditions at the free surface are discussed. The technique proposed is very quick and allows the use of big time steps. In comparison with the two phase version, the proposed techniques used one thousand times bigger time steps and require around 25 times less computational effort. On the other hand, the results shows dependency on the artificial compressibility parameter introduced as part of the solution of the flow equations. Extensions to the presented study are proposed including the use of different flow solvers.
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Stapleton, Neil Robert. "Analysis of synthetic-aperture radar imagery containing ship-generated internal-wave wakes." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300503.
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Du, Peng. "Numerical modeling and prediction of ship maneuvering and hydrodynamics during inland waterway transport." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2459.
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Dans cette thèse, l'hydrodynamique des navires lors du transport par voies navigables et des manœuvres sont étudiées à l'aide de la CFD (Computational Fluid Dynamics) basée sur OpenFoam. Des études de validation et de vérification sont réalisées pour la convergence de maillage, la convergence de pas de temps, la sensibilité aux modèles de turbulence et les techniques de maillage dynamique. Un solveur de mouvement 6DoF basé sur quaternion est mis en œuvre pour les prédictions d'assiette et d'enfoncement. Les effets environnementaux sur plusieurs bateaux de navigation intérieure (convoi 1, convoi 2, automoteur) sont étudiés à l'aide de modèles numériques validés. Trois aspects importants sont simulés: l'effet de confinement de la voie navigable, le croissement et l'interaction bateau-pile de pont. Les conditions d’essai couvrent un large éventail, y compris les différentes dimensions du canal, la profondeur de l’eau, le tirant d'eau et la vitesse. La résistance du navire, le type de vague, l’angle de Kelvin et l’élévation de la vague à des positions spécifiques sont étudiés en fonction de ces paramètres. La manœuvre des navires est étudiée à l’aide de tests de modèles captifs virtuels basés sur le modèle MMG (Mathematical Maneuvering Group). Un disque d'actionneur est implémenté pour remplacer l'hélice réelle. Les tests d'un modèle KVLCC2 sont effectués pour obtenir les coefficients hydrodynamiques de l'hélice, du gouvernail et de la coque du navire. En utilisant les coefficients obtenus, des simulations de manœuvre sont effectuées et validées. Ces études reproduisent des tests de navires réels et prouvent ainsi la validité de nos modèles numériques. En conséquence, le solveur numérique est prometteur dans les simulations d'hydrodynamique des navires et d'ingénierie marineIn this thesis, the ship hydrodynamics during inland waterway transport and ship maneuvering are investigated using CFD (Computational Fluid Dynamics) based onOpenFoam. Validation and verification studies are carried out for the mesh convergence, time step convergence, sensitivity to turbulence models and dynamic mesh techniques. A quaternion-based 6DoF motion solver is implemented for the trim and sinkage predictions. Environmental effects on several inland vessels (convoy 1, convoy 2, tanker) are studied using the validated numerical models. Three important aspects, the confinement effect of the waterway, head-on encounter and ship-bridge pile interaction are simulated. The testing conditions cover a wide range, including various channel dimensions, water depths, ship draughts and speeds. The ship resistance, wave pattern, Kelvin angle and wave elevation at specific positions are investigated as functions of these parameters. Ship maneuvering is investigated using virtual captive model tests based on the MMG (Mathematical Maneuvering Group) model. An actuator disk is implemented to replace the real propeller. Open water test, rudder force test, OTT (Oblique Towing Tank test) and CMT (Circular Motion Test) of a KVLCC2 model are carried out to obtain the hydrodynamic coefficients of the propeller, rudder and ship hull. Using the obtained coefficients, system-based maneuvering simulations are carried out and validated using the free running test data. These studies reproduce real ship tests and thus prove the validity of our numerical models. As a result, the numerical solver is promising in ship hydrodynamics and marine engineering simulations
Book chapters on the topic "Ship-generated waves"
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Nguyen, Son Huu, Tin Trung Huynh, Vinh Trong Bui, and Ngo Van Dau. "The Mechanism of Riverbank Erosion Caused by Ship-Generated Waves Along Hau River’s Entrance Navigation Channel, Southern Vietnam." In Lecture Notes in Civil Engineering, 897–904. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0077-7_73.
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Adam, John A. "Surface Gravity Waves." In Rays, Waves, and Scattering. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691148373.003.0011.
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This chapter deals with the underlying mathematics of surface gravity waves, defined as gravity waves observed on an air–sea interface of the ocean. Surface gravity waves, or surface waves, differ from internal waves, gravity waves that occur within the body of the water (such as between parts of different densities). Examples of gravity waves are wind-generated waves on the water surface, as well tsunamis and ocean tides. Wind-generated gravity waves on the free surface of the Earth's seas, oceans, ponds, and lakes have a period of between 0.3 and 30 seconds. The chapter first describes the basic fluid equations before discussing the dispersion relations, with a particular focus on deep water waves, shallow water waves, and wavepackets. It also considers ship waves and how dispersion affects the wave pattern produced by a moving object, along with long and short waves.
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Inoue, Yoshiyuki, and Md Kamruzzaman. "A numerical calculation of wave pattern generated by a seagoing ship." In Hydrodynamics VI: Theory and Applications, 67–76. Taylor & Francis, 2004. http://dx.doi.org/10.1201/b16815-12.
Full textConference papers on the topic "Ship-generated waves"
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Scragg, Carl A. "Spectral Analysis of Ship-Generated Waves in Finite-Depth Water." In ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28510.
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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 it 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 [1967] 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.
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Molland, A. F., P. A. Wilson, and S. Chandraprabha. "The Prediction of Ship Generated Near-field Wash Waves using Thin Ship Theory." In Hydrodynamics of High Speed Craft. RINA, 2000. http://dx.doi.org/10.3940/rina.hs.2000.12.
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Luo, Wei, Yuqi Yang, and Bo Yin. "Doppler spectrum for composite scattering of time-evolved ship-generated waves." In 2017 Progress in Electromagnetics Research Symposium - Fall (PIERS - FALL). IEEE, 2017. http://dx.doi.org/10.1109/piers-fall.2017.8293209.
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Shiotani, S. "Measurement and estimation of waves generated by a small ship in port." In OCEANS 2010 IEEE - Sydney. IEEE, 2010. http://dx.doi.org/10.1109/oceanssyd.2010.5603962.
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Molland, A. F., P. A. Wilson, S. R. Turnock, D. J. Taunton, and S. Chandraprabha. "The Prediction of the Characteristics of Ship Generated Near-Field Wash Waves." In FAST 2001. RINA, 2001. http://dx.doi.org/10.3940/rina.ft.2001.87.
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Soda, Taisuke, Shigeaki Shiotani, Hidenari Makino, and Yoichi Shimada. "Simulation of Weather and Ocean for Numerical Ship Navigation." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49240.
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For safe navigation, high-resolution information on wind and waves is very important. In coastal areas in particular, the weather and ocean situation changes dramatically in time and place according to the effects of geography and water depth. In this paper, high resolution wave data are generated using SWAN [1][2] as a numerical wave model. To estimate waves, wind data is necessary. By using the mesoscale meteorological model of WRF-ARW, detailed wind data was generated. We simulated wind and ocean waves for the duration of a typhoon passing over Japan in September of 2004. Secondly, we simulated ship maneuvering using simulated wind and wave data. For the ship maneuvering model, the MMG (Mathematic Modeling Group) was used. Combining high-resolution wind and wave data with the numerical navigation model, we studied the effects of wind and waves on a ship’s maneuvering. Comparing the simulated rhumb lines of a ship with the dead reckoning tracks, it was recognized that the effects of the wind and waves on a moving ship were significant.
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Wu, Yuanhao, Liwei Liu, Luqun Wang, Yongyan Ma, and Zhiguo Zhang. "Analysis of Square Wave Characteristic Based on Viscous Flow CFD." In ASME 2021 40th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/omae2021-63754.
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Abstract When two waves in different directions meet due to different weather patterns, a cross wave pattern will be generated, which will finally result in the spread of square waves on the sea surface. The emergence of square waves will threaten the navigation performance of a ship and may lead to capsizing of a ship in severe cases. In this paper, the numerical square wave tank is developed by using the in-house CFD software HUST-Ship. In the process of simulation, by means of solving the unsteady RANS equation of incompressible fluid, the analytical solution of the corresponding regular wave is generated at the inlet boundary, and the free surface is captured by level-set method. Square wave is generated by superimposing two vertical regular waves with the same wave length, wave height and phase. Through analyzing the CFD model of square wave, the uncertainty analysis of wave height and length are performed. The verification and validation procedures of grid and time-step are performed to ensure the credibility of simulation results. Moreover, a detecting point is set at the origin to get the time history curve of the wave height. The linear solution and second-order Stokes solution of waves are used to fit the wave height time-history curve respectively.
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Yang, Ray-Yeng, Ming-Chung Fang, and Igor V. Shugan. "Ship Wake Structure on the Finite Sea Depth in the Presence of Wind Waves." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49872.
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A kinematics model of the ship wake in the presence of surface waves, generated by wind is presented. It is 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 directed almost normally to the ship track are presented in the very narrow ship wake.
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Shiotani, Shigeaki. "On High-Resolutive Analysis of Direction of Waves Generated by a Small High-Speed Boat." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20598.
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A simplified estimation of the height and period of waves generated by a small boat was proposed in previous papers. The estimated height and period of waves were in good agreement with field results using a small boat. In addition, a new method called MUSIC (Multiple Signal Classification) was proposed to analyze the direction of ship waves. The distribution of the directional spectrum of ship waves as estimated by MUSIC presented a sharp monotone peak, and the estimated results were supported by field results using a small boat. The proposed estimation of ship waves by MUSIC was confirmed to be very effective. In present study, the direction of waves generated by a small boat was determined using MUSIC. In the previous study, the triangular array was fixed to a stand on the quay, and the measurement of the ship waves was limited to the sea area near the pier. In the current study, a triangular array was made by three buoys in order to analyze the waves created by a ship offshore. The analytical results derived by MUSIC were analyzed and were confirmed to be highly effective.
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Yasuda, Eiji, Hidetsugu Iwashita, and Masashi Kashiwagi. "Improvement of Rankine Panel Method for Seakeeping Prediction of a Ship in Low Frequency Region." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54163.
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Rankine panel methods have been studied for solving 3D seakeeping problems of a ship with forward speed and oscillatory motions. Nevertheless, there is a drawback in the numerical method for satisfying the radiation condition of outgoing waves at low frequencies, because the waves generated ahead of a ship reflect from the outward computational boundary and smear the flow around the ship. The so-called panel shift technique has been adopted in the frequency-domain Rankine panel method, which is effective when the generated waves propagate downstream of a ship. In this paper, in addition to this conventional panel shift method, Rayleigh’s artificial friction is introduced in the free-surface boundary condition to suppress longer wave components in a computational region apart from the ship. With this practical new method, it is shown that there is no prominent wave reflection from the side and/or upstream computational boundaries even in the range of low frequencies. As a consequence, the unsteady pressure, hydrodynamic forces, wave-induced ship motions, added resistance are computed with reasonable accuracy even in following waves and in good agreement with measured results in the experiment using a bulk carrier model which is also conducted for the present study.
Reports on the topic "Ship-generated waves"
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Malej, Matt, and Fengyan Shi. Suppressing the pressure-source instability in modeling deep-draft vessels with low under-keel clearance in FUNWAVE-TVD. Engineer Research and Development Center (U.S.), May 2021. http://dx.doi.org/10.21079/11681/40639.
Full textAbstract:
This Coastal and Hydraulics Engineering Technical Note (CHETN) documents the development through verification and validation of three instability-suppressing mechanisms in FUNWAVE-TVD, a Boussinesq-type numerical wave model, when modeling deep-draft vessels with a low under-keel clearance (UKC). Many large commercial ports and channels (e.g., Houston Ship Channel, Galveston, US Army Corps of Engineers [USACE]) are traveled and affected by tens of thousands of commercial vessel passages per year. In a series of recent projects undertaken for the Galveston District (USACE), it was discovered that when deep-draft vessels are modeled using pressure-source mechanisms, they can suffer from model instabilities when low UKC is employed (e.g., vessel draft of 12 m¹ in a channel of 15 m or less of depth), rendering a simulation unstable and obsolete. As an increasingly large number of deep-draft vessels are put into service, this problem is becoming more severe. This presents an operational challenge when modeling large container-type vessels in busy shipping channels, as these often will come as close as 1 m to the bottom of the channel, or even touch the bottom. This behavior would subsequently exhibit a numerical discontinuity in a given model and could severely limit the sample size of modeled vessels. This CHETN outlines a robust approach to suppressing such instability without compromising the integrity of the far-field vessel wave/wake solution. The three methods developed in this study aim to suppress high-frequency spikes generated nearfield of a vessel. They are a shock-capturing method, a friction method, and a viscosity method, respectively. The tests show that the combined shock-capturing and friction method is the most effective method to suppress the local high-frequency noises, while not affecting the far-field solution. A strong test, in which the target draft is larger than the channel depth, shows that there are no high-frequency noises generated in the case of ship squat as long as the shock-capturing method is used.