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1
Dewar, W. K., J. Schoonover, T. J. McDougall, and W. R. Young. "Semicompressible Ocean Dynamics." Journal of Physical Oceanography 45, no. 1 (January 2015): 149–56. http://dx.doi.org/10.1175/jpo-d-13-0268.1.
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AbstractThe equations of motion are reexamined with the objective of improving upon the Boussinesq approximation. The authors derive new equations that conserve energy, filter out sound waves, are more accurate than the Boussinesq set, and are computationally competitive with them. The new equations are partly enabled by exploiting a reversible exchange between internal and gravitational potential fluid energy. To improve upon these equations appears to require the inclusion of acoustics, at which point one should use full Navier–Stokes. This study recommends the new sets for testing in general circulation modeling.
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W.F.A. "Ocean waves mechanics, computational fluid dynamics, and mathematical modelling." Mathematics and Computers in Simulation 33, no. 2 (August 1991): 179. http://dx.doi.org/10.1016/0378-4754(91)90173-z.
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Mellor, George. "On Surf Zone Fluid Dynamics." Journal of Physical Oceanography 51, no. 1 (January 2021): 37–46. http://dx.doi.org/10.1175/jpo-d-19-0318.1.
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AbstractThere have been several numerical models developed to represent the phase-averaged flow in the surf zone, which is characterized by kD less than unity, where k is wavenumber and D is the water column depth. The classic scenario is that of surface gravity waves progressing onto a shore that create an offshore undertow current. In fact, in some models, flow velocities are parameterized assuming the existence of an undertow. The present approach uses the full vertically dependent continuity and momentum equations and the vertically dependent wave radiation stress in addition to turbulence equations. The model is applied to data that feature measurements of wave properties and also cross-shore velocities. In this paper, both the data and the model application are unidirectional and the surface stress is nil, representing the simplest surf zone application. Breaking waves are described empirically. Special to the surf zone, it is found that a simple empirical adjustment of the radiation stress enables a favorable comparison with data. Otherwise, the model applies to the open ocean with no further empiricism. A new bottom friction algorithm had been derived and is introduced in this paper. In the context of the turbulence transport model, the algorithm is relatively simple.
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Matt, S., A. Fujimura, A. Soloviev, S. H. Rhee, and R. Romeiser. "Fine-scale features on the sea surface in SAR satellite imagery – Part 2: Numerical modeling." Ocean Science 10, no. 3 (June 2, 2014): 427–38. http://dx.doi.org/10.5194/os-10-427-2014.
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Abstract. With the advent of the new generation of synthetic aperture radar (SAR) satellites, it has become possible to resolve fine-scale features on the sea surface on the scale of meters. The proper identification of sea surface signatures in SAR imagery can be challenging, since some features may be due to atmospheric distortions (gravity waves, squall lines) or anthropogenic influences (slicks), and may not be related to dynamic processes in the upper ocean. In order to improve our understanding of the nature of fine-scale features on the sea surface and their signature in SAR, we have conducted high-resolution numerical simulations combining a three-dimensional non-hydrostatic computational fluid dynamics model with a radar imaging model. The surface velocity field from the hydrodynamic model is used as input to the radar imaging model. The combined approach reproduces the sea surface signatures in SAR of ship wakes, low-density plumes, and internal waves in a stratified environment. The numerical results are consistent with observations reported in a companion paper on in situ measurements during SAR satellite overpasses. Ocean surface and internal waves are also known to produce a measurable signal in the ocean magnetic field. This paper explores the use of computational fluid dynamics to investigate the magnetic signatures of oceanic processes. This potentially provides a link between SAR signatures of transient ocean dynamics and magnetic field fluctuations in the ocean. We suggest that combining SAR imagery with data from ocean magnetometers may be useful as an additional maritime sensing method. The new approach presented in this work can be extended to other dynamic processes in the upper ocean, including fronts and eddies, and can be a valuable tool for the interpretation of SAR images of the ocean surface.
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Matt, S., A. Fujimura, A. Soloviev, S. H. Rhee, and R. Romeiser. "Fine-scale features on the sea surface in SAR satellite imagery – Part 2: Numerical modeling." Ocean Science Discussions 9, no. 5 (September 17, 2012): 2915–50. http://dx.doi.org/10.5194/osd-9-2915-2012.
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Abstract. With the advent of the new generation of SAR satellites, it has become possible to resolve fine-scale features on the sea surface on the scale of meters. The proper identification of sea surface signatures in SAR imagery can be challenging, since some features may be due to atmospheric distortions (gravity waves, squall lines) or anthropogenic influences (slicks), and may not be related to dynamic processes in the upper ocean. In order to improve our understanding of the nature of fine-scale features on the sea surface and their signature in SAR, we have conducted high-resolution numerical simulations combining a three-dimensional non-hydrostatic computational fluid dynamics model with a radar imaging model. The surface velocity field from the hydrodynamic model is used as input to the radar imaging model. The combined approach reproduces the sea surface signatures in SAR of ship wakes, low density plumes, and internal waves in a stratified environment. The numerical results are consistent with observations reported in a companion paper of in-situ measurements during SAR satellite overpasses. Ocean surface and internal waves are also known to produce a measurable signal in the ocean magnetic field. This paper explores the use of computational fluid dynamics to investigate the magnetic signatures of oceanic processes. This potentially provides a link between SAR signatures of transient ocean dynamics and magnetic field fluctuations in the ocean. We suggest that combining SAR imagery with data from ocean magnetometers may be useful as an additional maritime sensing method. The new approach presented in this work can be extended to other dynamic processes in the upper ocean, including fronts and eddies, and can be a valuable tool for the interpretation of SAR images of the ocean surface.
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Segur, Harvey, and Soroush Khadem. "Wind-Driven Waves on the Air-Water Interface." Fluids 6, no. 3 (March 16, 2021): 122. http://dx.doi.org/10.3390/fluids6030122.
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An ocean swell refers to a train of periodic or nearly periodic waves. The wave train can propagate on the free surface of a body of water over very long distances. A great deal of the current study in the dynamics of water waves is focused on ocean swells. These swells are typically created initially in the neighborhood of an ocean storm, and then the swell propagates away from the storm in all directions. We consider a different kind of wave, called seas, which are created by and driven entirely by wind. These waves typically have no periodicity, and can rise and fall with changes in the wind. Specifically, this is a two-fluid problem, with air above a moveable interface, and water below it. We focus on the local dynamics at the air-water interface. Various properties at this locality have implications on the waves as a whole, such as pressure differentials and velocity profiles. The following analysis provides insight into the dynamics of seas, and some of the features of these intriguing waves, including a process known as white-capping.
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Mousaviraad, Maysam, Michael Conger, Shanti Bhushan, Frederick Stern, Andrew Peterson, and Mehdi Ahmadian. "Coupled computational fluid and multi-body dynamics suspension boat modeling." Journal of Vibration and Control 24, no. 18 (August 9, 2017): 4260–81. http://dx.doi.org/10.1177/1077546317722897.
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Multiphysics modeling, code development, and validation by full-scale experiments is presented for hydrodynamic/suspension-dynamic interactions of a novel ocean vehicle, the Wave Adaptive Modular Vessel (WAM-V). The boat is a pontoon catamaran with hinged engine pods and elevated payload supported by suspension and articulation systems. Computational fluid dynamics models specific to WAM-V are developed which include hinged pod dynamics, water-jet propulsion modeling, and immersed boundary method for flow in the gap between pontoon and pod. Multi-body dynamics modeling for the suspension and upper-structure dynamic is developed in MATLAB Simulink. Coupled equations of motion are developed and solved iteratively through either one-way or two-way coupling methods to converge on flow-field, pontoon motions, pod motions, waterjet forces, and suspension motions. Validation experiments include cylinder drop with suspended mass and 33-feet WAM-V sea-trials in calm water and waves. Computational results show that two-way coupling is necessary to capture the physics of the interactions. The experimental trends are predicted well and errors are mostly comparable to those for rigid boats, however, in some cases the errors are larger, which is expected due to the complexity of the current studies. Ride quality analyses show that WAM-V suspension is effective in reducing payload vertical accelerations in waves by 73% compared to the same boat with rigid upper-structure.
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Renzi, Emiliano, and F. Dias. "Hydro-acoustic precursors of gravity waves generated by surface pressure disturbances localised in space and time." Journal of Fluid Mechanics 754 (July 31, 2014): 250–62. http://dx.doi.org/10.1017/jfm.2014.398.
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AbstractWe consider the mechanics of coupled underwater-acoustic and surface-gravity waves generated by surface pressure disturbances in a slightly compressible fluid. We show that pressure changes on the ocean surface, localised in space and time, can induce appreciable underwater compression waves which are precursors of the surface gravity waves. Although the physical properties of acoustic-gravity waves have already been discussed in the literature, such dynamics was not investigated in previous studies. We derive new results for the underwater compression wave field and discuss the dynamics of its generation and propagation. This work could lead to the design of innovative alert systems for coastal flooding management.
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Marquart, Rutger, Alfred Bogaers, Sebastian Skatulla, Alberto Alberello, Alessandro Toffoli, Carina Schwarz, and Marcello Vichi. "A Computational Fluid Dynamics Model for the Small-Scale Dynamics of Wave, Ice Floe and Interstitial Grease Ice Interaction." Fluids 6, no. 5 (April 29, 2021): 176. http://dx.doi.org/10.3390/fluids6050176.
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The marginal ice zone is a highly dynamical region where sea ice and ocean waves interact. Large-scale sea ice models only compute domain-averaged responses. As the majority of the marginal ice zone consists of mobile ice floes surrounded by grease ice, finer-scale modelling is needed to resolve variations of its mechanical properties, wave-induced pressure gradients and drag forces acting on the ice floes. A novel computational fluid dynamics approach is presented that considers the heterogeneous sea ice material composition and accounts for the wave-ice interaction dynamics. Results show, after comparing three realistic sea ice layouts with similar concentration and floe diameter, that the discrepancy between the domain-averaged temporal stress and strain rate evolutions increases for decreasing wave period. Furthermore, strain rate and viscosity are mostly affected by the variability of ice floe shape and diameter.
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Saito, Tatsuhiko, and Tatsuya Kubota. "Tsunami Modeling for the Deep Sea and Inside Focal Areas." Annual Review of Earth and Planetary Sciences 48, no. 1 (May 30, 2020): 121–45. http://dx.doi.org/10.1146/annurev-earth-071719-054845.
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This article reviews tsunami modeling and its relation to recent developments of deep-ocean observations. Unlike near-coast observations, deep-ocean observations have enabled the capture of short-wavelength dispersive tsunamis and reflected waves from the coast. By analyzing these waves, researchers can estimate tsunami sources and earthquake slip distributions more reliably with higher spatial resolution. In addition, fractional tsunami speed reduction due to the elasticity of the Earth medium is now clearly detected. Densely and widely distributed tsunami sensors make it possible to observe tsunamis inside the earthquake focal area, and understanding tsunami generation mechanisms is increasingly important. In order to describe the generation field, we should consider seismic waves overlapping tsunami signals in addition to vertical and horizontal displacements at the sea bottom. The importance of elastic dynamics, in addition to fluid dynamics, is increasing in order for researchers to fully understand tsunami phenomena using the new offshore and inside focal area observations. ▪ Deep-ocean observations have advanced tsunami propagation modeling. ▪ New deep-ocean observations in earthquake focal areas are expected to detect in situ tsunami generation caused by megathrust earthquakes. ▪ The importance of elastic dynamics, in addition to fluid dynamics, is increasing to help researchers fully understand mechanics in tsunami generation and propagation. ▪ Tsunami modeling including earthquake rupture and seismic waves contributes to mega-thrust earthquake investigation and disaster mitigation.
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Manolidis, Michail, Mark Orzech, and Julian Simeonov. "Rogue Wave Formation in Adverse Ocean Current Gradients." Journal of Marine Science and Engineering 7, no. 2 (January 24, 2019): 26. http://dx.doi.org/10.3390/jmse7020026.
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Studies of the nonlinear Schrödinger (NLS) equation indicate that surface gravity waves traveling against currents of increasing strength gain energy and steepness in the process, and this can be a mechanism for rogue wave formation. Likewise, experimental studies have shown that stable wavetrains traveling against adverse currents can give rise to extreme waves. We studied this phenomenon by using computational fluid dynamics (CFD) tools, whereby the non-hydrostatic Euler equations were solved utilizing the finite volume method. Waveforms based on a JONSWAP spectrum were generated in a numerical wave tank and were made to travel against current gradients of known strength, and wave characteristics were monitored in the process. We verified that waves gain energy from the underlying flow field as they travel against current gradients, and the simulated level of energy increase was comparable to that predicted by earlier studies of the NLS equation. The computed significant wave height, H s , increased substantially, and there were strong indications that the current gradients induced nonlinear wave instabilities. The simulations were used to determine a new empirical relationship that correlates changes in the current velocity to changes in the Benjamin–Feir Index (BFI). The empirical relationship allows for seafaring entities to predict increased risk of rogue waves ahead, based on wave and current conditions.
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OWEN, G. W., I. D. ABRAHAMS, A. J. WILLMOTT, and C. W. HUGHES. "On the scattering of baroclinic Rossby waves by a ridge in a continuously stratified ocean." Journal of Fluid Mechanics 465 (August 25, 2002): 131–55. http://dx.doi.org/10.1017/s0022112002001027.
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In global ocean dynamics Rossby waves play a vital rôle in the long-term distribution of vorticity; knowledge of the interaction between these waves and topography is crucial to a full understanding of this process, and hence to the transportation of energy, mixing and ocean circulation. The interaction of baroclinic Rossby waves with abrupt topography is the focus of this study. In this paper we model the ocean as a continuously stratified fluid for which the linear theory predicts a qualitatively different structure for the wave modes than that predicted by barotropic or simple layered models, even if most of the density variation is confined to the thermocline. We consider the scattering of a westward-propagating baroclinic Rossby wave by a narrow ridge on the ocean floor, modelled by a line barrier of infinite extent, orientated at an arbitrary angle to the incident wave. Transmission and reflection coefficients for the propagating modes are found using both an algebraic method and, in the case where this breaks down, matched asymptotic expansions. The results are compared with recent analyses of satellite altimetry data.
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Pomeau, Y., T. Jamin, M. Le Bars, P. Le Gal, and B. Audoly. "Law of spreading of the crest of a breaking wave." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 464, no. 2095 (April 2008): 1851–66. http://dx.doi.org/10.1098/rspa.2008.0024.
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In a wide range of conditions, ocean waves break. This can be seen as the manifestation of a singularity in the dynamics of the fluid surface, moving under the effect of the fluid motion underneath. We show that, at the onset of breaking, the wave crest expands in the spanwise direction as the square root of time. This is first derived from a theoretical analysis and then compared with experimental findings. The agreement is excellent.
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Sajjadi, Shahrdad G., and Julian C. R. Hunt. "Michael Selwyn Longuet-Higgins. 8 December 1925—26 February 2016." Biographical Memoirs of Fellows of the Royal Society 65 (August 2018): 249–65. http://dx.doi.org/10.1098/rsbm.2017.0031.
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Michael Longuet-Higgins was a geometer and applied mathematician who made notable contributions to geophysics and physical oceanography, particularly to the theory of oceanic microseism and to the dynamics of finite amplitude, sharp-crested wind-generated surface waves. The latter led to his pioneering studies on breaking waves. On a much larger scale, he showed how ocean waves produce currents around islands in the ocean. He considered wider aspects of the physics of waves, including wave-driven transport of sand along beaches, and the electrical effects of tidal streams. He also contributed to subjects of a geometrical character such as the growth of quasi-crystals, the assembly of protein sheaths in viruses, to chains of circle themes and to a wide variety of other topics. He was an extraordinary applied mathematician, using the simplest forms of mathematics to demonstrate and discover highly complex nonlinear phenomena. In particular, he often thought of problems involving water waves using his unique knowledge of geometry and then tested his theories by experiment. Along with Brooke Benjamin FRS, Sir James Lighthill FRS, Walter Munk FRS, John Miles and Andrei Monin, Michael Longuet-Higgins stands out as one of the towering figures of theoretical fluid dynamics in the twentieth century. His contributions will have a continuing influence on our attempts to understand better the processes that influence the oceans.
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Dostal, Leo. "The Effect of Random Wind Forcing in the Nonlinear Schrödinger Equation." Fluids 4, no. 3 (July 2, 2019): 121. http://dx.doi.org/10.3390/fluids4030121.
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The influence of a strong and gusty wind field on ocean waves is investigated. How the random wind affects solitary waves is analyzed in order to obtain insights about wave generation by randomly time varying wind forcing. Using the Euler equations of fluid dynamics and the method of multiple scales, a random nonlinear Schrödinger equation and a random modified nonlinear Schrödinger equation are obtained for randomly wind forced nonlinear deep water waves. Miles theory is used for modeling the pressure variation at the wave surface resulting from the wind velocity field. The nonlinear Schrödinger equation and the modified nonlinear Schrödinger equation are computed using a relaxation pseudo spectral scheme. The results show that the influence of gusty wind on solitary waves leads to a randomly increasing ocean wave envelope. However, in a laboratory setup with much smaller wave amplitudes and higher wave frequencies, the influence of water viscosity is much higher. This leads to fluctuating solutions, which are sensitive to wind forcing.
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Choi, Wooyoung, and Roberto Camassa. "Weakly nonlinear internal waves in a two-fluid system." Journal of Fluid Mechanics 313 (April 25, 1996): 83–103. http://dx.doi.org/10.1017/s0022112096002133.
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We derive general evolution equations for two-dimensional weakly nonlinear waves at the free surface in a system of two fluids of different densities. The thickness of the upper fluid layer is assumed to be small compared with the characteristic wavelength, but no restrictions are imposed on the thickness of the lower layer. We consider the case of a free upper boundary for its relevance in applications to ocean dynamics problems and the case of a non-uniform rigid upper boundary for applications to atmospheric problems. For the special case of shallow water, the new set of equations reduces to the Boussinesq equations for two-dimensional internal waves, whilst, for great and infinite lower-layer depth, we can recover the well-known Intermediate Long Wave and Benjamin–Ono models, respectively, for one-dimensional uni-directional wave propagation. Some numerical solutions of the model for one-dimensional waves in deep water are presented and compared with the known solutions of the uni-directional model. Finally, the effects of finite-amplitude slowly varying bottom topography are included in a model appropriate to the situation when the dependence on one of the horizontal coordinates is weak.
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Melet, Angélique, Robert Hallberg, Sonya Legg, and Maxim Nikurashin. "Sensitivity of the Ocean State to Lee Wave–Driven Mixing." Journal of Physical Oceanography 44, no. 3 (March 1, 2014): 900–921. http://dx.doi.org/10.1175/jpo-d-13-072.1.
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Abstract Diapycnal mixing plays a key role in maintaining the ocean stratification and the meridional overturning circulation (MOC). In the ocean interior, it is mainly sustained by breaking internal waves. Two important classes of internal waves are internal tides and lee waves, generated by barotropic tides and geostrophic flows interacting with rough topography, respectively. Currently, regarding internal wave–driven mixing, most climate models only explicitly parameterize the local dissipation of internal tides. In this study, the authors explore the combined effects of internal tide– and lee wave–driven mixing on the ocean state. A series of sensitivity experiments using the Geophysical Fluid Dynamics Laboratory CM2G ocean–ice–atmosphere coupled model are performed, including a parameterization of lee wave–driven mixing using a recent estimate for the global map of energy conversion into lee waves, in addition to the tidal mixing parameterization. It is shown that, although the global energy input in the deep ocean into lee waves (0.2 TW; where 1 TW = 1012 W) is small compared to that into internal tides (1.4 TW), lee wave–driven mixing makes a significant impact on the ocean state, notably on the ocean thermal structure and stratification, as well as on the MOC. The vertically integrated circulation is also impacted in the Southern Ocean, which accounts for half of the lee wave energy flux. Finally, it is shown that the different spatial distribution of the internal tide and lee wave energy input impacts the sensitivity described in this study. These results suggest that lee wave–driven mixing should be parameterized in climate models, preferably using more physically based parameterizations that allow the internal lee wave–driven mixing to evolve in a changing ocean.
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Karpatovich, I. I., and G. K. Korotaev. "Dynamics of Rossby waves in an ocean with inhomogeneous currents." Physical Oceanography 9, no. 3 (May 1998): 179–90. http://dx.doi.org/10.1007/bf02523228.
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Zhang, Bao-Ji, Jie Liu, Ning Xu, Lei Niu, and Wen-Xuan She. "Numerical Simulation of Ship Motions in Regular and Irregular Waves." Marine Technology Society Journal 53, no. 1 (January 1, 2019): 97–106. http://dx.doi.org/10.4031/mtsj.53.1.10.
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AbstractA numerical simulation method is presented in this study to predict ship resistance and motion responses in regular and irregular waves. The unsteady RANS (Reynolds Average Navier-Stokes) method is selected as the governing equation, and a volume of fluid (VoF) model is used to capture the free surface, combining the k-ε equations. A finite volume method (FVM) is utilized to discretize both the RANS equations and VoF transport equation. The pressure implicit split operator (PISO) method is set as the velocity-pressure coupling equation. The overset mesh technique is utilized to simulate ship motions in waves. A DTMB5415 ship is selected as a case study to predict its pitch and heave responses in regular and irregular waves at different wave length and wave steepness. The ship is free to move in the pitch and heave directions. The CFD (Computational Fluid Dynamics) results are found to be in good agreement with the strip theory and experimental data. It can be found that the CFD method presented in this study can provide a theoretical basis and technical support for green design and manufacture of ships.
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Melville, W. Kendall, and Alexey V. Fedorov. "The equilibrium dynamics and statistics of gravity–capillary waves." Journal of Fluid Mechanics 767 (February 18, 2015): 449–66. http://dx.doi.org/10.1017/jfm.2014.740.
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AbstractRecent field observations and modelling of breaking surface gravity waves suggest that air-entraining breaking is not sufficiently dissipative of surface gravity waves to balance the dynamics of wind-wave growth and nonlinear interactions with dissipation for the shorter gravity waves of $O(10)$ cm wavelength. Theories of parasitic capillary waves that form at the crest and forward face of shorter steep gravity waves have shown that the dissipative effects of these waves may be one to two orders of magnitude greater than the viscous dissipation of the underlying gravity waves. Thus the parasitic capillaries may provide the required dissipation of the short wind-generated gravity waves. This has been the subject of speculation and conjecture in the literature. Using the nonlinear theory of Fedorov & Melville (J. Fluid Mech., vol. 354, 1998, pp. 1–42), we show that the dissipation due to the parasitic capillaries is sufficient to balance the wind input to the short gravity waves over some range of wave ages and wave slopes. The range of gravity wave lengths on which these parasitic capillary waves are dynamically significant approximately corresponds to the range of short gravity waves that Cox & Munk (J. Mar. Res., vol. 13, 1954, pp. 198–227) found contributed significantly to the mean square slope of the ocean surface, which they measured to be proportional to the wind speed. Here we show that the mean square slope predicted by the theory is proportional to the square of the friction velocity of the wind, ${u_{\ast }}^{2}$, for small wave slopes, and approximately $u_{\ast }$ for larger slopes.
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Tian, Hao, Zijian Zhou, and Yu Sui. "Modeling and Validation of an Electrohydraulic Power Take-Off System for a Portable Wave Energy Convertor with Compressed Energy Storage." Energies 12, no. 17 (September 2, 2019): 3378. http://dx.doi.org/10.3390/en12173378.
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Small-scale, portable generation of electricity from ocean waves provides a versatile solution to power the ocean sensors network, in addition to the traditional large-scale wave energy conversion facilities. However, one issue of small-scale wave energy convertor (WEC) is the low capturable power density, challenging the design of the efficient power take-off (PTO) system. To tackle this challenge, in this paper, an electrohydraulic PTO system with compressed energy storage was proposed to boost output power of a portable WEC. Lumped-parameter kinematics and dynamics of the four-bar mechanism, the fluid dynamics of the digital fluid power circuit, and the mechanical and volumetric power losses were modeled and experimentally validated. Initial test results of the 0.64 m2 footprint prototype showed that the inclusion of storage improved the averaged electric power output over 40 times compared to the traditional architecture, and the proposed device can deliver up to 122 W at peaks.
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Valizadeh, Alireza, Jason P. Antenucci, and Grant Griffith. "REGULAR WAVE EFFECTS ON NEGATIVELY BUOYANT JETS." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 13. http://dx.doi.org/10.9753/icce.v36v.waves.13.
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Seawater desalination is an increasingly important technology in the supply of potable water to municipal communities. Brine created by this process is typically released back to the ocean via a nearshore diffuser into a wave-exposed climate. Despite this, little work has been published on the effect of waves on negatively buoyant jets. In this paper we outline the literature on this topic and the results of a series of computational fluid dynamics (CFD) simulations that address the role of regular waves on negatively buoyant jets.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/0085wAVVybc
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Zanowski, Hannah, and Robert Hallberg. "Weddell Polynya Transport Mechanisms in the Abyssal Ocean." Journal of Physical Oceanography 47, no. 12 (December 2017): 2907–25. http://dx.doi.org/10.1175/jpo-d-17-0091.1.
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AbstractWeddell Polynya transport mechanisms in the deep and abyssal oceans are examined in the NOAA Geophysical Fluid Dynamics Laboratory’s (GFDL) coupled climate model CM2G. During an 1820-yr-long integration of the model, polynyas are forced every 29 years in the Weddell Sea via an increase in the diapycnal diffusivity. Composites of the events are used to examine the mechanisms responsible for transporting polynya signals away from the Weddell Sea. Polynya signal transport is governed by two dynamical mechanisms that act on different time scales and spread at different rates. Large-scale waves, such as Kelvin and planetary and topographic Rossby waves, propagate the polynya signal rapidly, on interannual-to-decadal time scales, while advection transports the signal more slowly, on decadal-to-centennial time scales. Despite their different spreading rates, these mechanisms can act contemporaneously, and it is often their combined effect that governs the property changes in the global deep and abyssal oceans. Both waves and advection cause temperature changes on isobaths. In the deep Atlantic, advection accounts for <15% of the total temperature change in the model, indicating that waves are strongly dominant there. Elsewhere, waves are still the stronger contributor, but advection accounts for 20%–40% of the total temperature change.
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Acanfora, Maria, and Antonio Cirillo. "On the development of a fast modeling of floodwater effects on ship motions in waves." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 231, no. 4 (February 14, 2017): 877–87. http://dx.doi.org/10.1177/1475090216687438.
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The motions of a flooded ship in waves are difficult to evaluate. They are affected by complex phenomena involving ship and floodwater dynamic interactions. Several numerical methods have been proposed to estimate the dynamic behavior of a damaged ship in waves. In this article, a fast simulation tool is developed to tackle the problem, aiming at a simplified method with an acceptable accuracy of the results. A novel approach in simulating floodwater effects on ship motions is presented. The method allows modeling the floodwater motions (seen as lumped mass) out of phase from ship motions. This technique is based on the basic fluid mechanics knowledge for a liquid in a uniformly accelerated tank. The study intends to analyze the behavior of a flooded ship in regular beam waves, for compartment fillings that involve shallow and intermediate fluid depths. The nonlinear model for the roll damping moment of a ship is implemented. An attempt to model viscous effects in the floodwater dynamics is proposed and applied. Two sets of applications are carried out on two different hull models. The comparisons of the intact and of the flooded ship responses in waves are conducted and discussed.
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Dai, Chao-Qing, Yue-Yue Wang, and Anjan Biswas. "Dynamics of dispersive long waves in fluids." Ocean Engineering 81 (May 2014): 77–88. http://dx.doi.org/10.1016/j.oceaneng.2014.02.007.
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Song, Qiu Hong, Xin Tang, Ya Mei Lan, and Yong Cheng Liang. "Design of Ocean Data Buoys Based on CFD." Advanced Materials Research 163-167 (December 2010): 2441–44. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.2441.
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Ocean Data Buoy with fixed-point, real-time, long-term, continuous and accurate data collection capabilities is a modern ocean observing tools and instruments. Therefore, the reliability of information is essential, which depends on the stability of the working buoy. While the waves are acting, the buoys are difficult to maintain their stability. Based on Computational Fluid Dynamics, the force situations of buoy at wave conditions are simulated by using Variable Operating Frequency method and Fluent software. The variation of lift and drag forces and the changing trend of movement of buoy are obtained. And then the numerical value of force is adjusted by changing the height of waterline. At last, the digital design of shell structure is carried out with SolidWorks to improve the stability of buoys in surface wave.
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Duran, Serbay, Asıf Yokuş, Hülya Durur, and Doğan Kaya. "Refraction simulation of internal solitary waves for the fractional Benjamin–Ono equation in fluid dynamics." Modern Physics Letters B 35, no. 26 (August 13, 2021): 2150363. http://dx.doi.org/10.1142/s0217984921503632.
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In this study, the modified [Formula: see text]-expansion method and modified sub-equation method have been successfully applied to the fractional Benjamin–Ono equation that models the internal solitary wave event in the ocean or atmosphere. With both analytical methods, dark soliton, singular soliton, mixed dark-singular soliton, trigonometric, rational, hyperbolic, complex hyperbolic, complex type traveling wave solutions have been produced. In these applications, we consider the conformable operator to which the chain rule is applied. Special values were given to the constants in the solution while drawing graphs representing the stationary wave. By making changes of these constants at certain intervals, the refraction dynamics and physical interpretations of the obtained internal solitary waves were included. These physical comments were supported by simulation with 3D, 2D and contour graphics. These two analytical methods used to obtain analytical solutions of the fractional Benjamin–Ono equation have been analyzed in detail by comparing their respective states. By using symbolic calculation, these methods have been shown to be the powerful and reliable mathematical tools for the solution of fractional nonlinear partial differential equations.
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Maciel, Rafael P., Cristiano Fragassa, Bianca N. Machado, Luiz A. O. Rocha, Elizaldo D. dos Santos, Mateus N. Gomes, and Liércio A. Isoldi. "Verification and Validation of a Methodology to Numerically Generate Waves Using Transient Discrete Data as Prescribed Velocity Boundary Condition." Journal of Marine Science and Engineering 9, no. 8 (August 19, 2021): 896. http://dx.doi.org/10.3390/jmse9080896.
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This work presents a two-dimensional numerical analysis of a wave channel and a oscillating water column (OWC) device. The main goal is to validate a methodology which uses transient velocity data as a means to impose velocity boundary condition for the generation of numerical waves. To achieve this, a numerical wave channel was simulated using regular waves with the same parameters as those used in a laboratory experiment. First, these waves were imposed as prescribed velocity boundary condition and compared with the analytical solution; then, the OWC device was inserted into the computational domain, aiming to validate this methodology. For the numerical analysis, computational fluid dynamics ANSYS Fluent software was employed, and to tackle with water–air interaction, the nonlinear multiphase model volume of fluid (VOF) was applied. Although the results obtained through the use of discrete data as velocity boundary condition presented a little disparity; in general, they showed a good agreement with laboratory experiment results. Since many studies use regular waves, there is a lack of analysis with ocean waves realistic data; thus, the proposed methodology stands out for its capacity of using realistic sea state data in numerical simulations regarding wave energy converters (WECs).
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Gomes, Mateus das Neves, Eduardo Alves Amado, Elizaldo Domingues dos Santos, Liércio André Isoldi, and Luiz Alberto Oliveira Rocha. "Numerical Analysis of the Oscillating Water Column (OWC) Wave Energy Converter (WEC) Considering Different Incident Wave Height." Defect and Diffusion Forum 370 (January 2017): 120–29. http://dx.doi.org/10.4028/www.scientific.net/ddf.370.120.
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The ocean wave energy conversion into electricity has been increasingly researched in the last years. There are several proposed converters, among them the Oscillating Water Column (OWC) device has been widely studied. The present paper presents a two-dimensional numerical investigation about the fluid dynamics behavior of an OWC Wave Energy Converter (WEC) into electrical energy. The main goal of this work was to numerically analyze the optimized geometric shape obtained in previous work under incident waves with different heights. To do so, the OWC geometric shape was kept constant while the incident wave height was varied. For the numerical solution it was used the Computational Fluid Dynamic (CFD) commercial code FLUENT®, based on the Finite Volume Method (FVM). The multiphasic Volume of Fluid (VOF) model was applied to tackle with the water-air interaction. The computational domain is represented by the OWC device coupled with the wave tank. This work allowed to check the influence of the incident wave height on the hydropneumatic power and the amplification factor of the OWC converter. It was possible to identify that the amplification factor increases as the wave period increases, thereby improving the OWC performance. It is worth to highlight that in the real phenomenon the incident waves on the OWC device have periods, lengths and height variables.
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Wunsch, Carl, and Raffaele Ferrari. "100 Years of the Ocean General Circulation." Meteorological Monographs 59 (January 1, 2018): 7.1–7.32. http://dx.doi.org/10.1175/amsmonographs-d-18-0002.1.
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Abstract The central change in understanding of the ocean circulation during the past 100 years has been its emergence as an intensely time-dependent, effectively turbulent and wave-dominated, flow. Early technologies for making the difficult observations were adequate only to depict large-scale, quasi-steady flows. With the electronic revolution of the past 50+ years, the emergence of geophysical fluid dynamics, the strongly inhomogeneous time-dependent nature of oceanic circulation physics finally emerged. Mesoscale (balanced), submesoscale oceanic eddies at 100-km horizontal scales and shorter, and internal waves are now known to be central to much of the behavior of the system. Ocean circulation is now recognized to involve both eddies and larger-scale flows with dominant elements and their interactions varying among the classical gyres, the boundary current regions, the Southern Ocean, and the tropics.
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Rabitti, Anna, and Leo R. M. Maas. "Meridional trapping and zonal propagation of inertial waves in a rotating fluid shell." Journal of Fluid Mechanics 729 (July 24, 2013): 445–70. http://dx.doi.org/10.1017/jfm.2013.310.
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AbstractInertial waves propagate in homogeneous rotating fluids, and constitute a challenging and simplified case study for the broader class of inertio-gravity waves, present in all geophysical and astrophysical media, and responsible for energetically costly processes such as diapycnal and angular momentum mixing. However, a complete analytical description and understanding of internal waves in arbitrarily shaped enclosed domains, such as the ocean or a planet liquid core, is still missing. In this work, the inviscid, linear inertial wave field is investigated by means of three-dimensional ray tracing in spherical shell domains, having in mind possible oceanographic applications. Rays are here classically interpreted as representative of energy paths, but in contrast to previous studies, they are now launched with a non-zero initial zonal component allowing for a more realistic, localized forcing and the development of azimuthal inhomogeneities. We find that meridional planes generally act in the shell geometry as attractors for ray trajectories. In addition, the existence of trajectories that are not subject to meridional trapping is here observed for the first time. Their dynamics was not captured by the previous purely meridional studies and unveils a new class of possible solutions for inertial motion in the spherical shell. Both observed behaviours shed some new light on possible mechanisms of energy localization, a key process that still deserves further investigation in our ocean, as well as in other stratified, rotating media.
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Zhang, Bao-Ji, Gao Yu, and Wen-Xuan She. "Offshore Wind Turbine Coupled Motion in Regular Waves." Marine Technology Society Journal 54, no. 2 (March 1, 2020): 5–16. http://dx.doi.org/10.4031/mtsj.54.2.2.
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AbstractThis study aims to accurately predict the hydrodynamic performance and motion responses of offshore wind turbines on the basis of computational fluid dynamics (CFD) theory. Continuous and Navier-Stokes (N-S) equations are employed as control equations, and the k-ε model is used as a turbulence model. The finite difference method is utilized to discretize the equation. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm is applied to solve the control equation, and the volume-of-fluid (VOF) method is used to capture the free surface. The numerical wave tank of irregular wave is also established. The hydrodynamic performances and motion responses of the offshore wind turbines under regular waves are studied. First, we assume a floating foundation without the influence of a rotational fan and examine its motion responses and wave force in three typical sea conditions, namely, Levels 5, 6, and 7. Thereafter, we use a series of force and torque acting on the rotating center of the offshore to substitute for the influence of the rotational fan on the floating foundation. Then, we study the hydrodynamic performance influenced by blade rotation of the floating foundation in various sea conditions and three wind speeds, namely, 5, 8, and 11 m/s. Research results can provide usable theoretical principle and technical support for the investigation of the hydrodynamic performance and motion responses of similar offshore wind turbines.
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Jiao, Jialong, and Songxing Huang. "CFD Simulation of Ship Seakeeping Performance and Slamming Loads in Bi-Directional Cross Wave." Journal of Marine Science and Engineering 8, no. 5 (April 29, 2020): 312. http://dx.doi.org/10.3390/jmse8050312.
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Accurate prediction of ship seakeeping performance in complex ocean environment is a fundamental requirement for ship design and actual operation in seaways. In this paper, an unsteady Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) solver with overset grid technique was applied to estimate the seakeeping performance of an S175 containership operating in bi-directional cross waves. The cross wave is reproduced by linear superposition of two orthogonal regular waves in a rectangle numerical wave tank. The ship nonlinear motion responses, bow slamming loads, and green water on deck induced by cross wave with different control parameters such as wave length and wave heading angle are systemically analyzed. The results demonstrate that both vertical and transverse motion responses, as well as slamming pressure of ship induced by cross wave, can be quite large, and they are quite different from those in regular wave. Therefore, ship navigational safety when suffering cross waves should be further concerned.
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Zou, Shangyan, and Ossama Abdelkhalik. "A Numerical Simulation of a Variable-Shape Buoy Wave Energy Converter." Journal of Marine Science and Engineering 9, no. 6 (June 4, 2021): 625. http://dx.doi.org/10.3390/jmse9060625.
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Wave energy converters (WECs) usually require reactive power for increased levels of energy conversion, resulting in the need for more complex power take-off (PTO) units, compared to WECs that do not require reactive power. A WEC without reactive power produces much less energy, though. The concept of Variable Shape Buoy Wave Energy Converters (VSB WECs) is proposed to allow continuous shape-change aiming at eliminating the need for reactive power, while converting power at a high level. The proposed concept involves complex and nonlinear interactions between the device and the waves. This paper presents a Computational Fluid Dynamics (CFD) tool that is set up to simulate VSB WECs, using the ANSYS 2-way fluid–structure interaction (FSI) tool. The dynamic behavior of a VSB WEC is simulated in this CFD-based Numerical Wave Tank (CNWT), in open sea conditions. The simulation results show that the tested device undergoes a significant deformation in response to the incoming waves, before it reaches a steady-state behavior. This is in agreement with a low-fidelity dynamic model developed in earlier work. The resulting motion is significantly different from the motion of a rigid body WEC. The difference in the motion can be leveraged for better energy capture without the need for reactive power.
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Fedorov, Alexey V., and W. Kendall Melville. "A Model of Strongly Forced Wind Waves." Journal of Physical Oceanography 39, no. 10 (October 1, 2009): 2502–22. http://dx.doi.org/10.1175/2009jpo4155.1.
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Abstract A model of surface waves generated on deep water by strong winds is proposed. A two-layer approximation is adopted, in which a shallow turbulent layer overlies the lower, infinitely deep layer. The dynamics of the upper layer, which is directly exposed to the wind, are nonlinear and coupled to the linear dynamics in the deep fluid. The authors demonstrate that in such a system there exist steady wave solutions characterized by confined regions of wave breaking alternating with relatively long intervals where the wave profiles change monotonically. In the former regions the flow is decelerated; in the latter it is accelerated. The regions of breaking are akin to hydraulic jumps of finite width necessary to join the smooth “interior” flows and have periodic waves. In contrast to classical hydraulic jumps, the strongly forced waves lose both energy and momentum across the jumps. The flow in the upper layer is driven by the balance between the wind stress at the surface, the turbulent drag applied at the layer interface, and the wave drag induced at the layer interface by quasi-steady breaking waves. Propagating in the downwind direction, the strongly forced waves significantly modify the flow in both layers, lead to enhanced turbulence, and reduce the speed of the near-surface flow. According to this model, a large fraction of the work done by the surface wind stress on the ocean in high winds may go directly into wave breaking and surface turbulence.
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Restrepo, Juan M. "Wave Breaking Dissipation in the Wave-Driven Ocean Circulation." Journal of Physical Oceanography 37, no. 7 (July 1, 2007): 1749–63. http://dx.doi.org/10.1175/jpo3099.1.
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Abstract If wave breaking modifies the Lagrangian fluid paths by inducing an uncertainty in the orbit itself and this uncertainty on wave motion time scales is observable as additive noise, it is shown that within the context of a wave–current interaction model for basin- and shelf-scale motions it persists on long time scales. The model of McWilliams et al. provides the general framework for the dynamics of wave–current interactions. In addition to the deterministic part, the vortex force, which couples the total flow vorticity to the residual flow due to the waves, will have a part that is associated with the dissipative mechanism. At the same time the wave field will experience dissipation, and tracer advection is affected by the appearance of a dissipative term in the Stokes drift velocity. Consistency leads to other dynamic consequences: the boundary conditions are modified to take into account the diffusive process and proper mass/momentum balances at the surface of the ocean. In addition to formulating how a wave–current interaction model is modified by the presence of short-time events that induce dissipation, this study proposes a stochastic parameterization of dissipation. Its relation to other alternative parameterizations is given. Two focal reasons make stochastic parameterizations attractive: one can draw from extensive practical modeling experience in other fields, and it ties in a very natural way to a wealth of observational data via statistics.
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Bonnet, P., V. A. Yastrebov, P. Queutey, A. Leroyer, A. Mangeney, O. Castelnau, A. Sergeant, E. Stutzmann, and J.-P. Montagner. "Modelling capsizing icebergs in the open ocean." Geophysical Journal International 223, no. 2 (July 25, 2020): 1265–87. http://dx.doi.org/10.1093/gji/ggaa353.
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Summary At near-grounded glacier termini, calving can lead to the capsize of kilometre-scale (i.e. gigatons) unstable icebergs. The transient contact force applied by the capsizing iceberg on the glacier front generates seismic waves that propagate over teleseismic distances. The inversion of this seismic signal is of great interest to get insight into actual and past capsize dynamics. However, the iceberg size, which is of interest for geophysical and climatic studies, cannot be recovered from the seismic amplitude alone. This is because the capsize is a complex process involving interactions between the iceberg, the glacier and the surrounding water. This paper presents a first step towards the construction of a complete model, and is focused on the capsize in the open ocean without glacier front nor ice-mélange. The capsize dynamics of an iceberg in the open ocean is captured by computational fluid dynamics (CFD) simulations, which allows assessing the complexity of the fluid motion around a capsizing iceberg and how far the ocean is affected by iceberg rotation. Expressing the results in terms of appropriate dimensionless variables, we show that laboratory scale and field scale capsizes can be directly compared. The capsize dynamics is found to be highly sensitive to the iceberg aspect ratio and to the water and ice densities. However, dealing at the same time with the fluid dynamics and the contact between the iceberg and the deformable glacier front requires highly complex coupling that often goes beyond actual capabilities of fluid-structure interaction softwares. Therefore, we developed a semi-analytical simplified fluid-structure model (SAFIM) that can be implemented in solid mechanics computations dealing with contact dynamics of deformable solids. This model accounts for hydrodynamic forces through calibrated drag and added-mass effects, and is calibrated against the reference CFD simulations. We show that SAFIM significantly improves the accuracy of the iceberg motion compared with existing simplified models. Various types of drag forces are discussed. The one that provides the best results is an integrated pressure-drag proportional to the square of the normal local velocity at the iceberg’s surface, with the drag coefficient depending linearly on the iceberg’s aspect ratio. A new formulation based on simplified added-masses or computed added-mass proposed in the literature, is also discussed. We study in particular the change of hydrodynamic-induced forces and moments acting on the capsizing iceberg. The error of the simulated horizontal force ranges between 5 and 25 per cent for different aspect ratios. The added-masses affect the initiation period of the capsize, the duration of the whole capsize being better simulated when added-masses are accounted for. The drag force mainly affects the amplitude of the fluid forces and this amplitude is best predicted without added-masses.
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Melet, Angélique, Robert Hallberg, Alistair Adcroft, Maxim Nikurashin, and Sonya Legg. "Energy Flux into Internal Lee Waves: Sensitivity to Future Climate Changes Using Linear Theory and a Climate Model." Journal of Climate 28, no. 6 (March 13, 2015): 2365–84. http://dx.doi.org/10.1175/jcli-d-14-00432.1.
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Abstract Internal lee waves generated by geostrophic flows over rough topography are thought to be a significant energy sink for eddies and energy source for deep ocean mixing. The sensitivity of the energy flux into lee waves from preindustrial, present, and possible future climate conditions is explored in this study using linear theory. The bottom stratification and geostrophic velocity fields needed for the calculation of the energy flux into lee waves are provided by Geophysical Fluid Dynamics Laboratory’s global coupled ocean–ice–atmosphere model, CM2G. The unresolved mesoscale eddy energy is parameterized as a function of the large-scale available potential energy. Simulations using historical and representative concentration pathway (RCP) scenarios were performed over the 1861–2200 period. The diagnostics herein suggest a decrease of the global energy flux into lee waves on the order of 20% from preindustrial to future climate conditions under the RCP8.5 scenario. In the Southern Ocean, the energy flux into lee waves exhibits a clear annual cycle with maximum values in austral winter. The long-term decrease of the global energy flux into lee waves and the annual cycle of the energy flux in the Southern Ocean are mostly due to changes in bottom velocity.
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Wu, Ping-Chen, Md Alfaz Hossain, Naoki Kawakami, Kento Tamaki, Htike Aung Kyaw, Ayaka Matsumoto, and Yasuyuki Toda. "EFD and CFD Study of Forces, Ship Motions, and Flow Field for KRISO Container Ship Model in Waves." Journal of Ship Research 64, no. 01 (March 1, 2020): 61–80. http://dx.doi.org/10.5957/jsr.2020.64.1.61.
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Ship motion responses and added resistance in waves have been predicted by a wide variety of computational tools. However, validation of the computational flow field still remains a challenge. In the previous study, the flow field around the Korea Research Institute for Ships and Ocean Engineering (KRISO) Very Large Crude-oil Carrier 2 tanker model with and without propeller condition and without rudder condition was measured by the authors, as well as the resistance and self-propulsion tests in waves. In this study, the KRISO container ship model appended with a rudder was used for the higher Froude number .26 and smaller block coefficient .65. The experiments were conducted in the Osaka University towing tank using a 3.2-m-long ship model for resistance and self-propulsion tests in waves. Viscous flow simulation was performed by using CFDShip-Iowa. The wave conditions proposed in Computational Fluid Dynamics (CFD) Workshop 2015 were considered, i.e., the wave-ship length ratio λ/L = .65, .85, 1.15, 1.37, 1.95, and calm water. The objective of this study was to validate CFD results by Experimental Fluid Dynamics (EFD) data for ship vertical motions, added resistance, and wake flow field. The detailed flow field for nominal wake and self-propulsion condition will be analyzed for λ/L = .65, 1.15, 1.37, and calm water. Furthermore, bilge vortex movement and boundary layer development on propeller plane, propeller thrust, and wake factor oscillation in waves will be studied.
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Foyhirun, Chutipat, Duangrudee Kositgittiwong, and Chaiwat Ekkawatpanit. "Wave Energy Potential and Simulation on the Andaman Sea Coast of Thailand." Sustainability 12, no. 9 (May 1, 2020): 3657. http://dx.doi.org/10.3390/su12093657.
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Ocean wave energy is an interesting renewable energy because it will never run out and can be available all the time. If the wave energy is to be used, then the feasibility study of localized wave potential has to be studied. This goal is to study the potential of waves in the Andaman Sea. The Simulating WAves Nearshore (SWAN) model was used to calculate the significant wave heights, which were validated with the measurement data of the Jason-2 satellite. The coastal area of Phuket and Phang Nga provinces are suitable locations for studying wave energy converters because they have high significant wave height. Moreover, this study used computational fluid dynamics (CFD) for the simulation of wave behavior in accordance with wave parameters from the SWAN model. The wave height simulated from CFD was validated with linear wave theory. The results found that it was in good agreement with linear wave theory. It can be applied for a simulation of the wave energy converter.
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Choi, Young-Myung, Young Jun Kim, Benjamin Bouscasse, Sopheak Seng, Lionel Gentaz, and Pierre Ferrant. "Performance of different techniques of generation and absorption of free-surface waves in Computational Fluid Dynamics." Ocean Engineering 214 (October 2020): 107575. http://dx.doi.org/10.1016/j.oceaneng.2020.107575.
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Li, Ang, and Yunbo Li. "Numerical and Experimental Study on Seakeeping Performance of a High-Speed Trimaran with T-foil in Head Waves." Polish Maritime Research 26, no. 3 (September 1, 2019): 65–77. http://dx.doi.org/10.2478/pomr-2019-0047.
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Abstract The longitudinal motion characteristics of a slender trimaran equipped with and without a T-foil near the bow are investigated by experimental and numerical methods. Computational fluid dynamics ( CFD) method is used in this study. The seakeeping characteristics such as heave, pitch and vertical acceleration in head regular waves are analyzed in various wave conditions. Numerical simulations have been validated by comparisons with experimental tests. The influence of large wave amplitudes and size of T-foil on the longitudinal motion of trimaran are analyzed. The present systematic study demonstrates that the numerical results are in a reasonable agreement with the experimental data. The research implied that the longitudinal motion response values are greatly reduced with the use of T-foil.
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Orzech, Mark D., Fengyan Shi, Jayaram Veeramony, Samuel Bateman, Joseph Calantoni, and James T. Kirby. "A Coupled System for Investigating the Physics of Wave–Ice Interactions." Journal of Atmospheric and Oceanic Technology 35, no. 7 (July 2018): 1471–85. http://dx.doi.org/10.1175/jtech-d-17-0189.1.
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AbstractA coupled model system has been developed to investigate the physics of wave attenuation and ice edge retreat in the marginal ice zone (MIZ) at small scales [O(m)]. A phase-dependent finite-volume/finite-difference fluid dynamics model is used to simulate waves and currents, and a discrete element software package is employed to represent ice floes as bonded collections of individually tracked smaller particles. We first review the development of the coupled system, with an emphasis on the coupling software and the representation of wave–ice shear stress. Then we describe a series of simulations that were conducted to evaluate and qualitatively validate the performance of the coupled models. The system produced reasonable results for cases of a vertically oscillating ice block and a free-floating ice floe in monochromatic waves. In larger-scale simulations involving multiple ice floes and pancake ice, estimated transmission and reflection coefficients were similar to those obtained from alternate models and/or data, although numerical dissipation may have reduced estimates of transmitted wave energy in longer wave flumes. Challenges and limitations involving relative length scales in the coupled wave and ice domains are explained and discussed.
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Restrepo, Juan M., Jorge M. Ramírez, James C. McWilliams, and Michael Banner. "Multiscale Momentum Flux and Diffusion due to Whitecapping in Wave–Current Interactions." Journal of Physical Oceanography 41, no. 5 (May 1, 2011): 837–56. http://dx.doi.org/10.1175/2010jpo4298.1.
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Abstract Whitecapping affects the Reynolds stresses near the ocean surface. A model for the conservative dynamics of waves and currents is modified to include the averaged effect of multiple, short-lived, and random wave-breaking events on large spatiotemporal scales. In this study’s treatment, whitecapping is parameterized stochastically as an additive uncertainty in the fluid velocity. It is coupled to the Stokes drift as well as to the current velocity in the form of nonlinear momentum terms in the vortex force and the Bernoulli head. The effects of whitecapping on tracer dynamics, mass balances, and boundary conditions are also derived here. Whitecapping also modifies the dynamics and the size of the sea surface boundary layer. This study does not resolve the boundary layer, however, the authors appeal to traditional viscosity parameterizations to include these diffusive effects, modified for the context of wave–current interactions. The parameterized breaking velocity field is endowed with empirical rules that link their generation in space and time to properties and dynamics of wave groups. The energy convergence rate of wave groups is used as an indicator for the onset of wave breaking. A methodology is proposed for evaluating this criterion over an evolving random Gaussian model for the ocean surface. The expected spatiotemporal statistics of the breaking events are not imposed, but rather computed, and are found to agree with the general expectation of its Poisson character. The authors also compute, rather than impose, the shear stress associated with the breaking events and find it to agree with theoretical expectations. When the relative role played by waves and breaking events on currents is compared, this study finds that waves, via the vortex force, purely advect the vorticity of currents that are essentially only dependent on transverse coordinates. The authors show that currents will tend to get rougher in the direction of steady wind, when whitecapping is present. Breaking events can alter and even suppress the rate of advection in the vortex force. When comparing the rates of transport, the waves will tend to dominate the short term and the whitecapping of the long-term rate.
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Zhang, Lei, Ling Ling Wang, Zhen Zhen Yu, Yuan Bao Leng, Wan Zeng Song, and Bin Zhang. "Characteristics of Non-Linear Internal Waves in a Three-Dimensional Numerical Wave Tank." Applied Mechanics and Materials 212-213 (October 2012): 1123–30. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.1123.
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Internal waves have a significant impact on the hydrodynamic and stratification characteristics in the density stratified lakes and oceans. In order to reveal the features of internal waves, a three-dimensional numerical wave tank in regular terrain based on the computational fluid dynamics (CFD) model was established to simulate the processes of non-linear internal solitary waves propagation and evolution. The concept of a fraction volume of fluid (VOF) was employed to track the interface of the two-layer fluid. Comparisons were made between CFD model and weakly non-linear KdV theory, it was shown that the wave amplitude predictions by the CFD model agreed well with the KdV equation. On the other hand, the convergence flow and divergence flow at the water surface were captured successfully by the simulated spatial and temporal distributions of velocity. Some peculiar hydrodynamic characteristics, e. g. turbulence kinetic energy and its dissipation rate in the numerical wave tank were also identified and examined. Consequently, this paper provides a reliable method for understanding the phenomenon of internal waves in stratified water bodies.
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Akselsen, Andreas H., and Simen Å. Ellingsen. "Weakly nonlinear transient waves on a shear current: ring waves and skewed Langmuir rolls." Journal of Fluid Mechanics 863 (January 29, 2019): 114–49. http://dx.doi.org/10.1017/jfm.2018.960.
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We investigate the weakly nonlinear dynamics of transient gravity waves at infinite depth under the influence of a shear current varying linearly with depth. The shear field makes this problem three-dimensional and rotational in nature, but an analytical solution is permitted via integration of the Euler equations. Although similar problems were investigated in the 1960s and 70s for special cases of resonance, this is to our knowledge the first general wave interaction (mode coupling) solution derived to second order with a shear current present. Wave interactions are integrable in a spectral convolution to yield the second-order dynamics of initial value problems. To second order, irrotational wave dynamics interacts with the background vorticity field in a way that creates new vortex structures. A notable example is the large parallel vortices which drive Langmuir circulation as oblique plane waves interact with an ocean current. We also investigate the effect on wave pairs which are misaligned with the shear current to find that similar, but skewed, vortex structures are generated in every case except when the mean wave direction is precisely perpendicular to the direction of the current. This is in contrast to a conjecture by Leibovich (Annu. Rev. Fluid Mech., vol. 15, 1983, pp. 391–427). Similar nonlinear wave–shear interactions are found to also generate near-field vortex structures in the Cauchy–Poisson problem with an initial surface elevation. These interactions create further groups of dispersive ring waves in addition to those present in linear theory. The second-order solution is derived in a general manner which accommodates any initial condition through mode coupling over a continuous wave spectrum. It is therefore applicable to a range of problems including special cases of resonance. As a by-product of the general theory, a simple expression for the Stokes drift due to a monochromatic wave propagating at oblique angle with a current of uniform vorticity is derived, for the first time to our knowledge.
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Larsson, Lars, Frederick Stern, and Volker Bertram. "Benchmarking of Computational Fluid Dynamics for Ship Flows: The Gothenburg 2000 Workshop." Journal of Ship Research 47, no. 01 (March 1, 2003): 63–81. http://dx.doi.org/10.5957/jsr.2003.47.1.63.
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The Gothenburg 2000 was an international benchmark workshop for computational fluid dynamics applied to ship flows. Test cases were three modern hull forms. One case without a free surface focused on turbulence modeling, whereas wave prediction was of interest for the other two. Of the free-surface cases, one had an operating propeller. For the first time, verification and validation procedures were an integral part of such benchmark efforts in ship flows. The workshop showed that free-surface waves may now be well predicted also away from the hull. There is a general improvement in the computation of the stern flow thanks to better turbulence modeling, but there is still room for improvement. Full-scale viscous flows may be computed without numerical difficulties. Verification and validation procedures should be applied for uncertainty analysis, and there is a discussion of the uncertainty in the predicted integral quantities in the paper. Further detailed conclusions and recommendations are also given based on the comparison of extensive standardized plots of the comparative computations and evaluation of the integral quantities.
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Kearins, Aoife. "Sir George Gabriel Stokes in Skreen: how a childhood by the sea influenced a giant in fluid dynamics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2174 (June 8, 2020): 20190516. http://dx.doi.org/10.1098/rsta.2019.0516.
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George Gabriel Stokes spent most of his life at the University of Cambridge, where he undertook his undergraduate degree and later became Lucasian Professor of Mathematics and Master of Pembroke College. However, he spent the first 13 years of his life in Skreen, County Sligo, Ireland, a rural area right by the coastline, overlooking the Atlantic Ocean. As this paper will discuss, the time he spent there was short but its influence on him and his research was long reaching, with his childhood activities of walking by and bathing in the sea being credited for first piquing Stokes' interest in ocean waves, which he would go on to write papers about. More generally, it marked the beginning of an interest in fluid dynamics and a curious nature regarding natural phenomena in his surroundings. Stokes held a special affinity for the ocean for the rest of his life, constantly drawing inspiration for it in his mathematical and physical studies and referencing it in his correspondences. This commentary was written to celebrate Stokes' 200th birthday as part of the theme issue of Philosophical Transactions A . This article is part of the theme issue ‘Stokes at 200 (Part 1)’.
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Chow, Kwok Wing, Hiu Ning Chan, and Roger H. J. Grimshaw. "Brief communication: Modulation instability of internal waves in a smoothly stratified shallow fluid with a constant buoyancy frequency." Natural Hazards and Earth System Sciences 19, no. 3 (March 19, 2019): 583–87. http://dx.doi.org/10.5194/nhess-19-583-2019.
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Abstract. Unexpectedly large displacements in the interior of the oceans are studied through the dynamics of packets of internal waves, where the evolution of these displacements is governed by the nonlinear Schrödinger equation. In cases with a constant buoyancy frequency, analytical treatment can be performed. While modulation instability in surface wave packets only arises for sufficiently deep water, “rogue” internal waves may occur in shallow water and intermediate depth regimes. A dependence on the stratification parameter and the choice of internal modes can be demonstrated explicitly. The spontaneous generation of rogue waves is tested here via numerical simulation.
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Pan, Qing, Hui-Min Yin, and Kwok W. Chow. "Triads and Rogue Events for Internal Waves in Stratified Fluids with a Constant Buoyancy Frequency." Journal of Marine Science and Engineering 9, no. 6 (May 26, 2021): 577. http://dx.doi.org/10.3390/jmse9060577.
Full textAbstract:
Internal waves in a stratified fluid with a constant buoyancy frequency were studied, with special attention given to rogue modes, extreme waves, dynamical evolution, and Fermi–Pasta–Ulam–Tsingou type recurrence phenomena. Rogue waves for triads in a general physical setting have recently been derived analytically, but the implications in a fluid mechanics context have not yet been fully assessed. Numerical simulations were conducted for cases of coupled triads where the common member is a daughter wave mode. In sharp contrast with previous studies, rogue modes instead of plane waves were used as the initial condition. Furthermore, spatial dependence was incorporated. Rogue or extreme waves in one set of triads provided a possible mechanism for significant energy transfer among modes of the internal wave spectrum, in addition to the other known theories, e.g., weak turbulence. Remarkably, Fermi–Pasta–Ulam–Tsingou recurrence types of growth and decay cycles arose, similar to those observed for surface gravity wave groups governed by the cubic nonlinear Schrödinger equation. These mechanisms will enhance our understanding of transport processes in oceans.