Shallow Water Waves and Solitary Waves
Hereman, Willy
2013-01-01
Encyclopedic article covering shallow water wave models used in oceanography and atmospheric science. Sections: Definition of the Subject; Introduction and Historical Perspective; Completely Integrable Shallow Water Wave Equations; Shallow Water Wave Equations of Geophysical Fluid Dynamics; Computation of Solitary Wave Solutions; Numerical Methods; Water Wave Experiments and Observations; Future Directions, and Bibliography.
Mandal, Birendra Nath
2015-01-01
The theory of water waves is most varied and is a fascinating topic. It includes a wide range of natural phenomena in oceans, rivers, and lakes. It is mostly concerned with elucidation of some general aspects of wave motion including the prediction of behaviour of waves in the presence of obstacles of some special configurations that are of interest to ocean engineers. Unfortunately, even the apparently simple problems appear to be difficult to tackle mathematically unless some simplified assumptions are made. Fortunately, one can assume water to be an incompressible, in viscid and homogeneous
2016-01-01
This volume brings together four lecture courses on modern aspects of water waves. The intention, through the lectures, is to present quite a range of mathematical ideas, primarily to show what is possible and what, currently, is of particular interest. Water waves of large amplitude can only be fully understood in terms of nonlinear effects, linear theory being not adequate for their description. Taking advantage of insights from physical observation, experimental evidence and numerical simulations, classical and modern mathematical approaches can be used to gain insight into their dynamics. The book presents several avenues and offers a wide range of material of current interest. Due to the interdisciplinary nature of the subject, the book should be of interest to mathematicians (pure and applied), physicists and engineers. The lectures provide a useful source for those who want to begin to investigate how mathematics can be used to improve our understanding of water wave phenomena. In addition, some of the...
Coriolis effect on water waves
Benjamin, Melinand
2015-01-01
This paper is devoted to the study of water waves under the influence of the gravity and the Coriolis force. It is quite common in the physical literature that the rotating shallow water equations are used to study such water waves. We prove a local wellposedness theorem for the water waves equations with vorticity and Coriolis force, taking into account the dependence on various physical parameters and we justify rigorously the shallow water model. We also consider a possible non constant pr...
Precession resonance in water waves
Lucas, Dan; Perlin, Marc
2016-01-01
We describe the theory and present numerical evidence for a new type of nonlinear resonant interaction between gravity waves on the surface of deep water. The resonance constitutes a generalisation of the usual 'exact' resonance as we show that exchanges of energy between the waves can be enhanced when the interaction is three-wave rather than four and the linear frequency mismatch, or detuning, is non-zero i.e. $\\omega_1\\pm\\omega_2\\pm\\omega_3 \
Shallow water cnoidal wave interactions
Directory of Open Access Journals (Sweden)
A. R. Osborne
1994-01-01
Full Text Available The nonlinear dynamics of cnoidal waves, within the context of the general N-cnoidal wave solutions of the periodic Korteweg-de Vries (KdV and Kadomtsev-Petvishvilli (KP equations, are considered. These equations are important for describing the propagation of small-but-finite amplitude waves in shallow water; the solutions to KdV are unidirectional while those of KP are directionally spread. Herein solutions are constructed from the 0-function representation of their appropriate inverse scattering transform formulations. To this end a general theorem is employed in the construction process: All solutions to the KdV and KP equations can be written as the linear superposition of cnoidal waves plus their nonlinear interactions. The approach presented here is viewed as significant because it allows the exact construction of N degree-of-freedom cnoidal wave trains under rather general conditions.
Modeling water waves beyond perturbations
Clamond, Didier
2015-01-01
In this chapter, we illustrate the advantage of variational principles for modeling water waves from an elementary practical viewpoint. The method is based on a `relaxed' variational principle, i.e., on a Lagrangian involving as many variables as possible, and imposing some suitable subordinate constraints. This approach allows the construction of approximations without necessarily relying on a small parameter. This is illustrated via simple examples, namely the Serre equations in shallow water, a generalization of the Klein-Gordon equation in deep water and how to unify these equations in arbitrary depth. The chapter ends with a discussion and caution on how this approach should be used in practice.
Real time wave measurements and wave hindcasting in deep waters
Digital Repository Service at National Institute of Oceanography (India)
Anand, N.M.; Mandal, S.; SanilKumar, V.; Nayak, B.U.
Deep water waves off Karwar (lat. 14~'45.1'N, long. 73~'34.8'E) at 75 m water depth pertaining to peak monsoon period have been measured using a Datawell waverider buoy. Measured wave data show that the significant wave height (Hs) predominantly...
Steady water waves with multiple critical layers
Ehrnström, Mats; Wahlén, Erik
2010-01-01
We construct small-amplitude periodic water waves with multiple critical layers. In addition to waves with arbitrarily many critical layers and a single crest in each period, two-dimensional sets of waves with several crests and troughs in each period are found. The setting is that of steady two-dimensional finite-depth gravity water waves with vorticity.
Regularity of rotational travelling water waves.
Escher, Joachim
2012-04-13
Several recent results on the regularity of streamlines beneath a rotational travelling wave, along with the wave profile itself, will be discussed. The survey includes the classical water wave problem in both finite and infinite depth, capillary waves and solitary waves as well. A common assumption in all models to be discussed is the absence of stagnation points.
Turbulent wind waves on a water current
Directory of Open Access Journals (Sweden)
M. V. Zavolgensky
2008-05-01
Full Text Available An analytical model of water waves generated by the wind over the water surface is presented. A simple modeling method of wind waves is described based on waves lengths diagram, azimuthal hodograph of waves velocities and others. Properties of the generated waves are described. The wave length and wave velocity are obtained as functions on azimuth of wave propagation and growth rate. Motionless waves dynamically trapped into the general picture of three dimensional waves are described. The gravitation force does not enter the three dimensional of turbulent wind waves. That is why these waves have turbulent and not gravitational nature. The Langmuir stripes are naturally modeled and existence of the rogue waves is theoretically proved.
Gravity Capillary Standing Water Waves
Alazard, Thomas; Baldi, Pietro
2015-09-01
The paper deals with the 2D gravity-capillary water waves equations in their Hamiltonian formulation, addressing the question of the nonlinear interaction of a plane wave with its reflection off a vertical wall. The main result is the construction of small amplitude, standing (namely periodic in time and space, and not travelling) solutions of Sobolev regularity, for almost all values of the surface tension coefficient, and for a large set of time-frequencies. This is an existence result for a quasi-linear, Hamiltonian, reversible system of two autonomous pseudo-PDEs with small divisors. The proof is a combination of different techniques, such as a Nash-Moser scheme, microlocal analysis and bifurcation analysis.
Geyer, Anna
2016-01-01
Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.
Geyer, Anna
2016-01-01
Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.
Wave Numerical Model for Shallow Water
Institute of Scientific and Technical Information of China (English)
徐福敏; 严以新; 张长宽; 宋志尧; 茅丽华
2000-01-01
The history of forecasting wind waves by wave energy conservation equation is briefly described. Several currently used wave numerical models for shallow water based on different wave theories are discussed. Wave energy conservation models for the simulation of shallow water waves are introduced,with emphasis placed on the SWAN model, which takes use of the most advanced wave research achievements and has been applied to several theoretical and field conditions. The characteristics and applicability of the model, the finite difference numerical scheme of the action balance equation and its source terms computing methods are described in detail. The model has been verified with the propagation refraction numerical experiments for waves propagating in following and opposing currents; finally, the model is applied to the Haian Gulf area to simulate the wave height and wave period field there, and the results are compared with observed data.
Parabolic Wave Equation for Surface Water Waves.
1986-11-01
extended to wave propagation problems in other fields of physical sciences, such as nonlinear optics ( Svelto , 1974), plasma physics (Karpman, 1975...34 Journal of Fluid Mechanics, Vol. 72, pp. 373-384. Svelto , 0., 1974, Progress in Optics, North-Holland Pub., Chapter 1, pp. 1-51. Tappert, F.D., 1977, "The
Metamaterials, from electromagnetic waves to water waves, bending waves and beyond
Dupont, G.
2015-08-04
We will review our recent work on metamaterials for different types of waves. Transposition of transform optics to water waves and bending waves on plates will be considered with potential applications of cloaking to water waves protection and anti-vibrating systems.
Water waves generated by underwater explosion
Mehaute, Bernard Le
1996-01-01
This is the first book on explosion-generated water waves. It presents the theoretical foundations and experimental results of the generation and propagation of impulsively generated waves resulting from underwater explosions. Many of the theories and concepts presented herein are applicable to other types of water waves, in particular, tsunamis and waves generated by the fall of a meteorite. Linear and nonlinear theories, as well as experimental calibrations, are presented for cases of deep and shallow water explosions. Propagation of transient waves on dissipative, nonuniform bathymetries to
A simple introduction to water waves
Mitsotakis, Dimitrios
2013-01-01
The theory of the water waves is the main subject in coastal hydrodynamics and plays a significant role in applied mathematics and in physics. In these notes we present the basics of the water wave theory. Specifically, after introducing briefly the basic concepts of continuum mechanics, we derive the physical laws describing the physics of an inviscid, incompressible fluid, namely the Euler equations. Euler equations are the governing equations of water waves, but because of the great diffic...
A NUMERICAL METHOD FOR NONLINEAR WATER WAVES
Institute of Scientific and Technical Information of China (English)
ZHAO Xi-zeng; SUN Zhao-chen; LIANG Shu-xiu; HU Chang-hong
2009-01-01
This article presents a numerical method for modeling nonlinear water waves based on the High Order Spectral (HOS) method proposed by Dommermuth and Yue and West et al., involving Taylor expansion of the Dirichlet problem and the Fast Fourier Transform (FFT) algorithm. The validation and efficiency of the numerical scheme is illustrated by a number of case studies on wave and wave train configuration including the evolution of fifth-order Stokes waves, wave dispersive focusing and the instability of Stokes wave with finite slope. The results agree well with those obtained by other studies.
Water Waves The Mathematical Theory with Applications
Stoker, J J
2011-01-01
Offers an integrated account of the mathematical hypothesis of wave motion in liquids with a free surface, subjected to gravitational and other forces. Uses both potential and linear wave equation theories, together with applications such as the Laplace and Fourier transform methods, conformal mapping and complex variable techniques in general or integral equations, methods employing a Green's function. Coverage includes fundamental hydrodynamics, waves on sloping beaches, problems involving waves in shallow water, the motion of ships and much more.
A relationship between wave steepness and wave age for wind waves in deep water
Institute of Scientific and Technical Information of China (English)
LIU Bin; DING Yun; GUAN Changlong
2007-01-01
Studying the relationship between wave steepness and wave age is import ant for describing wind wave growth with energy balance equation of significant waves. After invoking the dispersion relation of surface gravity wave in deep water, a new relationship between wave steepness and wave age is revealed based on the "3/2-power law" (Toba, 1972), in which wave steepness is a function of wave age with a drag coefficient as a parameter. With a given wave age, a larger drag coefficient would lead to larger wave steepness. This could be interpreted as the result of interaction between wind and waves.Comparing with previous relationships, the newly proposed one is more consistent with observational data in field and laboratory.
Extreme waves and wave loading in shallow water
Klopman, G.; Stive, M.J.F.
1989-01-01
As an alternative to a more or less standard derivation procedure for design wave heights in relatively shallow water, two improvements of the procedure are suggested which lead to less conservative results. These improvements are based on observations of shallow water effects on both the decay of t
Nonlinear water waves with soluble surfactant
Lapham, Gary; Dowling, David; Schultz, William
1998-11-01
The hydrodynamic effects of surfactants have fascinated scientists for generations. This presentation describes an experimental investigation into the influence of a soluble surfactant on nonlinear capillary-gravity waves in the frequency range from 12 to 20 Hz. Waves were generated in a plexiglass wave tank (254 cm long, 30.5 cm wide, and 18 cm deep) with a triangular plunger wave maker. The tank was filled with carbon- and particulate-filtered water into which the soluble surfactant Triton-X-100® was added in known amounts. Wave slope was measured nonintrusively with a digital camera running at 225 fps by monitoring the position of light beams which passed up through the bottom of the tank, out through the wavy surface, and onto a white screen. Wave slope data were reduced to determine wave damping and the frequency content of the wave train. Both were influenced by the presence of the surfactant. Interestingly, a subharmonic wave occurring at one-sixth the paddle-driving frequency was found only when surfactant was present and the paddle was driven at amplitudes high enough to produce nonlinear waves in clean water. Although the origins of this subharmonic wave remain unclear, it appears to be a genuine manifestation of the combined effects of the surfactant and nonlinearity.
Numerical modeling of water waves
Lin, Pengzhi
2008-01-01
Modelling large-scale wave fields and their interaction with coastal and offshore structures has become much more feasible over the last two decades with increases in computer speeds. Wave modelling can be viewed as an extension of wave theory, a mature and widely published field, applied to practical engineering through the use of computer tools. Information about the various wave models which have been developed is often widely scattered in the literature, and consequently this is one of the first books devoted to wave models and their applications. At the core of the book is an introduction to various types of wave models. For each model, the theoretical assumptions, the application range, and the advantages and limitations are elaborated. The combined use of different wave models from large-scale to local-scale is highlighted with a detailed discussion of the application and matching of boundary conditions. At the same time the book provides a grounding in hydrodynamics, wave theory, and numerical methods...
Turbulence beneath finite amplitude water waves
Energy Technology Data Exchange (ETDEWEB)
Beya, J.F. [Universidad de Valparaiso, Escuela de Ingenieria Civil Oceanica, Facultad de Ingenieria, Valparaiso (Chile); The University of New South Wales, Water Research Laboratory, School of Civil and Environmental Engineering, Sydney, NSW (Australia); Peirson, W.L. [The University of New South Wales, Water Research Laboratory, School of Civil and Environmental Engineering, Sydney, NSW (Australia); Banner, M.L. [The University of New South Wales, School of Mathematics and Statistics, Sydney, NSW (Australia)
2012-05-15
Babanin and Haus (J Phys Oceanogr 39:2675-2679, 2009) recently presented evidence of near-surface turbulence generated below steep non-breaking deep-water waves. They proposed a threshold wave parameter a {sup 2}{omega}/{nu} = 3,000 for the spontaneous occurrence of turbulence beneath surface waves. This is in contrast to conventional understanding that irrotational wave theories provide a good approximation of non-wind-forced wave behaviour as validated by classical experiments. Many laboratory wave experiments were carried out in the early 1960s (e.g. Wiegel 1964). In those experiments, no evidence of turbulence was reported, and steep waves behaved as predicted by the high-order irrotational wave theories within the accuracy of the theories and experimental techniques at the time. This contribution describes flow visualisation experiments for steep non-breaking waves using conventional dye techniques in the wave boundary layer extending above the wave trough level. The measurements showed no evidence of turbulent mixing up to a value of a {sup 2}{omega}/{nu} = 7,000 at which breaking commenced in these experiments. These present findings are in accord with the conventional understandings of wave behaviour. (orig.)
Variational modelling of nonlinear water waves
Kalogirou, Anna; Bokhove, Onno
2015-11-01
Mathematical modelling of water waves is demonstrated by investigating variational methods. A potential flow water wave model is derived using variational techniques and extented to include explicit time-dependence, leading to non-autonomous dynamics. As a first example, we consider the problem of a soliton splash in a long wave channel with a contraction at its end, resulting after a sluice gate is removed at a finite time. The removal of the sluice gate is included in the variational principle through a time-dependent gravitational potential. A second example involving non-autonomous dynamics concerns the motion of a free surface in a vertical Hele-Shaw cell. Explicit time-dependence now enters the model through a linear damping term due to the effect of wall friction and a term representing the motion of an artificially driven wave pump. In both cases, the model is solved numerically using a Galerkin FEM and the numerical results are compared to wave structures observed in experiments. The water wave model is also adapted to accommodate nonlinear ship dynamics. The novelty is this case is the coupling between the water wave dynamics, the ship dynamics and water line dynamics on the ship. For simplicity, we consider a simple ship structure consisting of V-shaped cross-sections.
WAVE-E: The WAter Vapour European-Explorer Mission
Jimenez-LLuva, David; Deiml, Michael; Pavesi, Sara
2017-04-01
In the last decade, stratosphere-troposphere coupling processes in the Upper Troposphere Lower Stratosphere (UTLS) have been increasingly recognized to severely impact surface climate and high-impact weather phenomena. Weakened stratospheric circumpolar jets have been linked to worldwide extreme temperature and high-precipitation events, while anomalously strong stratospheric jets can lead to an increase in surface winds and tropical cyclone intensity. Moreover, stratospheric water vapor has been identified as an important forcing for global decadal surface climate change. In the past years, operational weather forecast and climate models have adapted a high vertical resolution in the UTLS region in order to capture the dynamical processes occurring in this highly stratified region. However, there is an evident lack of available measurements in the UTLS region to consistently support these models and further improve process understanding. Consequently, both the IPCC fifth assessment report and the ESA-GEWEX report 'Earth Observation and Water Cycle Science Priorities' have identified an urgent need for long-term observations and improved process understanding in the UTLS region. To close this gap, the authors propose the 'WAter Vapour European - Explorer' (WAVE-E) space mission, whose primary goal is to monitor water vapor in the UTLS at 1 km vertical, 25 km horizontal and sub-daily temporal resolution. WAVE-E consists of three quasi-identical small ( 500 kg) satellites (WAVE-E 1-3) in a constellation of Sun-Synchronous Low Earth Orbits, each carrying a limb sounding and cross-track scanning mid-infrared passive spectrometer (824 cm-1 to 829 cm-1). The core of the instruments builds a monolithic, field-widened type of Michelson interferometer without any moving parts, rendering it rigid and fault tolerant. Synergistic use of WAVE-E and MetOp-NG operational satellites is identified, such that a data fusion algorithm could provide water vapour profiles from the
Asymptotic Linear Stability of Solitary Water Waves
Pego, Robert L.; Sun, Shu-Ming
2016-12-01
We prove an asymptotic stability result for the water wave equations linearized around small solitary waves. The equations we consider govern irrotational flow of a fluid with constant density bounded below by a rigid horizontal bottom and above by a free surface under the influence of gravity neglecting surface tension. For sufficiently small amplitude waves, with waveform well-approximated by the well-known sech-squared shape of the KdV soliton, solutions of the linearized equations decay at an exponential rate in an energy norm with exponential weight translated with the wave profile. This holds for all solutions with no component in (that is, symplectically orthogonal to) the two-dimensional neutral-mode space arising from infinitesimal translational and wave-speed variation of solitary waves. We also obtain spectral stability in an unweighted energy norm.
Wave power potential in Malaysian territorial waters
Asmida Mohd Nasir, Nor; Maulud, Khairul Nizam Abdul
2016-06-01
Up until today, Malaysia has used renewable energy technology such as biomass, solar and hydro energy for power generation and co-generation in palm oil industries and also for the generation of electricity, yet, we are still far behind other countries which have started to optimize waves for similar production. Wave power is a renewable energy (RE) transported by ocean waves. It is very eco-friendly and is easily reachable. This paper presents an assessment of wave power potential in Malaysian territorial waters including waters of Sabah and Sarawak. In this research, data from Malaysia Meteorology Department (MetMalaysia) is used and is supported by a satellite imaginary obtained from National Aeronautics and Space Administration (NASA) and Malaysia Remote Sensing Agency (ARSM) within the time range of the year 1992 until 2007. There were two types of analyses conducted which were mask analysis and comparative analysis. Mask analysis of a research area is the analysis conducted to filter restricted and sensitive areas. Meanwhile, comparative analysis is an analysis conducted to determine the most potential area for wave power generation. Four comparative analyses which have been carried out were wave power analysis, comparative analysis of wave energy power with the sea topography, hot-spot area analysis and comparative analysis of wave energy with the wind speed. These four analyses underwent clipping processes using Geographic Information System (GIS) to obtain the final result. At the end of this research, the most suitable area to develop a wave energy converter was found, which is in the waters of Terengganu and Sarawak. Besides that, it was concluded that the average potential energy that can be generated in Malaysian territorial waters is between 2.8kW/m to 8.6kW/m.
Oblique Water Wave Diffraction by a Step
Directory of Open Access Journals (Sweden)
Dolai P.
2017-02-01
Full Text Available This paper is concerned with the problem of diffraction of an obliquely incident surface water wave train on an obstacle in the form of a finite step. Havelock expansions of water wave potentials are used in the mathematical analysis to obtain the physical parameters reflection and transmission coefficients in terms of integrals. Appropriate multi-term Galerkin approximations involving ultraspherical Gegenbauer polynomials are utilized to obtain a very accurate numerical estimate for reflection and transmission coefficients which are depicted graphically. From these figures various interesting results are discussed.
Oblique Water Wave Diffraction by a Step
Dolai, P.
2017-02-01
This paper is concerned with the problem of diffraction of an obliquely incident surface water wave train on an obstacle in the form of a finite step. Havelock expansions of water wave potentials are used in the mathematical analysis to obtain the physical parameters reflection and transmission coefficients in terms of integrals. Appropriate multi-term Galerkin approximations involving ultraspherical Gegenbauer polynomials are utilized to obtain a very accurate numerical estimate for reflection and transmission coefficients which are depicted graphically. From these figures various interesting results are discussed.
Fabry-Perot resonance of water waves.
Couston, Louis-Alexandre; Guo, Qiuchen; Chamanzar, Maysamreza; Alam, Mohammad-Reza
2015-10-01
We show that significant water wave amplification is obtained in a water resonator consisting of two spatially separated patches of small-amplitude sinusoidal corrugations on an otherwise flat seabed. The corrugations reflect the incident waves according to the so-called Bragg reflection mechanism, and the distance between the two sets controls whether the trapped reflected waves experience constructive or destructive interference within the resonator. The resulting amplification or suppression is enhanced with increasing number of ripples and is most effective for specific resonator lengths and at the Bragg frequency, which is determined by the corrugation period. Our analysis draws on the analogous mechanism that occurs between two partially reflecting mirrors in optics, a phenomenon named after its discoverers Charles Fabry and Alfred Perot.
Variational approaches to water wave simulations
Gagarina, Elena Vitalyevna
2014-01-01
This thesis starts with the study the theoretical aspects of water wave modelling using a variational framework, which is directly associated with phase space and energy conservation laws. In particular, we focus on a new variational model based on the work of Cotter and Bokhove. The new model inclu
Statistical distribution of nonlinear random wave height in shallow water
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Here we present a statistical model of random wave,using Stokes wave theory of water wave dynamics,as well as a new nonlinear probability distribution function of wave height in shallow water.It is more physically logical to use the wave steepness of shallow water and the factor of shallow water as the parameters in the wave height distribution.The results indicate that the two parameters not only could be parameters of the distribution function of wave height but also could reflect the degree of wave height distribution deviation from the Rayleigh distribution.The new wave height distribution overcomes the problem of Rayleigh distribution that the prediction of big wave is overestimated and the general wave is underestimated.The prediction of small probability wave height value of new distribution is also smaller than that of Rayleigh distribution.The effect of wave steepness in shallow water is similar to that in deep water;but the factor of shallow water lowers the wave height distribution of the general wave with the reduced factor of wave steepness.It also makes the wave height distribution of shallow water more centralized.The results indicate that the new distribution fits the in situ measurements much better than other distributions.
On the Wind Generation of Water Waves
Bühler, Oliver; Shatah, Jalal; Walsh, Samuel; Zeng, Chongchun
2016-11-01
In this work, we consider the mathematical theory of wind generated water waves. This entails determining the stability properties of the family of laminar flow solutions to the two-phase interface Euler equation. We present a rigorous derivation of the linearized evolution equations about an arbitrary steady solution, and, using this, we give a complete proof of the instability criterion of M iles [16]. Our analysis is valid even in the presence of surface tension and a vortex sheet (discontinuity in the tangential velocity across the air-sea interface). We are thus able to give a unified equation connecting the Kelvin-Helmholtz and quasi-laminar models of wave generation.
Numerical study on water waves and wave-induced longshore currents in Obaköy coastal water
Institute of Scientific and Technical Information of China (English)
TANG Jun; LYU Yigang; SHEN Yongming
2014-01-01
In this paper, the water waves and wave-induced longshore currents in Obaköy coastal water which is lo-cated at the Mediterranean coast of Turkey were numerically studied. The numerical model is based on the parabolic mild-slope equation for coastal water waves and the nonlinear shallow water equation for the wave-induced currents. The wave transformation under the effects of shoaling, refraction, diffraction and breaking is considered, and the wave provides radiation stresses for driving currents in the model. The numerical results for the water wave-induced longshore currents were validated by the measured data to demonstrate the efficiency of the numerical model. Then the water waves and longshore currents induced by the waves from main directions were numerically simulated and analyzed based on the numerical re-sults. The numerical results show that the movement of the longshore currents was different while the wave propagated to a coastal zone from different directions.
Conditional Second Order Short-crested Water Waves Applied to Extreme Wave Episodes
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher
2005-01-01
A derivation of the mean second order short-crested wave pattern and associated wave kinematics, conditional on a given magnitude of the wave crest, is presented. The analysis is based on the second order Sharma and Dean finite water wave theory. A comparison with a measured extreme wave profile......, the Draupner New Year Wave, shows a good agreement in the mean, indicating that this second order wave can be a good identifier of the shape and occurrence of extreme wave events. A discussion on its use as an initial condition for a fully non-linear three-dimensional surface wave analysis is given....
Three-Dimensional Simulations of Deep-Water Breaking Waves
Brucker, Kyle A; Dommermuth, Douglas G; Adams, Paul
2014-01-01
The formulation of a canonical deep-water breaking wave problem is introduced, and the results of a set of three-dimensional numerical simulations for deep-water breaking waves are presented. In this paper fully nonlinear progressive waves are generated by applying a normal stress to the free surface. Precise control of the forcing allows for a systematic study of four types of deep-water breaking waves, characterized herein as weak plunging, plunging, strong plunging, and very strong plunging.
MHD Shallow Water Waves: Linear Analysis
Heng, Kevin
2009-01-01
We present a linear analysis of inviscid, incompressible, magnetohydrodynamic (MHD) shallow water systems. In spherical geometry, a generic property of such systems is the existence of five wave modes. Three of them (two magneto-Poincare modes and one magneto-Rossby mode) are previously known. The other two wave modes are strongly influenced by the magnetic field and rotation, and have substantially lower angular frequencies; as such, we term them "magnetostrophic modes". We obtain analytical functions for the velocity, height and magnetic field perturbations in the limit that the magnitude of the MHD analogue of Lamb's parameter is large. On a sphere, the magnetostrophic modes reside near the poles, while the other modes are equatorially confined. Magnetostrophic modes may be an ingredient in explaining the frequency drifts observed in Type I X-ray bursts from neutron stars.
Deep water periodic waves as Hamiltonian relative equilibria
van Groesen, Embrecht W.C.; Lie She Liam, L.S.L.; Lakhturov, I.; Andonowati, A.; Biggs, N.
2007-01-01
We use a recently derived KdV-type of equation for waves on deep water to study Stokes waves as relative equilibria. Special attention is given to investigate the cornered Stokes-120 degree wave as a singular solution in the class of smooth steady wave profiles.
Topological water wave states in a one-dimensional structure
Yang, Zhaoju; Gao, Fei; Zhang, Baile
2016-01-01
Topological concepts have been introduced into electronic, photonic, and phononic systems, but have not been studied in surface-water-wave systems. Here we study a one-dimensional periodic resonant surface-water-wave system and demonstrate its topological transition. By selecting three different water depths, we can construct different types of water waves - shallow, intermediate and deep water waves. The periodic surface-water-wave system consists of an array of cylindrical water tanks connected with narrow water channels. As the width of connecting channel varies, the band diagram undergoes a topological transition which can be further characterized by Zak phase. This topological transition holds true for shallow, intermediate and deep water waves. However, the interface state at the boundary separating two topologically distinct arrays of water tanks can exhibit different bands for shallow, intermediate and deep water waves. Our work studies for the first time topological properties of water wave systems, and paves the way to potential management of water waves. PMID:27373982
Reduced-order prediction of rogue waves in two-dimensional deep-water waves
Farazmand, Mohammad
2016-01-01
We consider the problem of large wave prediction in two-dimensional water waves. Such waves form due to the synergistic effect of dispersive mixing of smaller wave groups and the action of localized nonlinear wave interactions that leads to focusing. Instead of a direct simulation approach, we rely on the decomposition of the wave field into a discrete set of localized wave groups with optimal length scales and amplitudes. Due to the short-term character of the prediction, these wave groups do not interact and therefore their dynamics can be characterized individually. Using direct numerical simulations of the governing envelope equations we precompute the expected maximum elevation for each of those wave groups. The combination of the wave field decomposition algorithm, which provides information about the statistics of the system, and the precomputed map for the expected wave group elevation, which encodes dynamical information, allows (i) for understanding of how the probability of occurrence of rogue wave...
A WEAKLY NONLINEAR WATER WAVE MODEL TAKING INTO ACCOUNT DISPERSION OF WAVE PHASE VELOCITY
Institute of Scientific and Technical Information of China (English)
李瑞杰; 李东永
2002-01-01
This paper presents a weakly nonlinear water wave model using a mild slope equation and a new explicit formulation which takes into account dispersion of wave phase velocity, approximates Hedges' (1987) nonlinear dispersion relationship, and accords well with the original empirical formula. Comparison of the calculating results with those obtained from the experimental data and those obtained from linear wave theory showed that the present water wave model considering the dispersion of phase velocity is rational and in good agreement with experiment data.
Multipeakedness and groupiness of shallow water waves along Indian coast
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Anand, N.M.; AshokKumar, K.; Mandal, S.
that would be expected from an estimate based on a completely random successive of the wave heights. Grouping ofhigh waves (H s = 2 m) in a long travelled swell recorded at a shallow water location ofwest coast of India was examined by THOMAS et al. (1986... to be succeeded by large waves, while small waves tend to be succeeded by other small waves. For the long travelled swell, GODA (1983) found a mean correlation of 0.65 between successive waves and 0.35, 0.18 and 0.07 for the following waves. THOMAS et at. (1986...
Periodic folded waves for a (2+1)-dimensional modified dispersive water wave equation
Institute of Scientific and Technical Information of China (English)
Huang Wen-Hua
2009-01-01
A general solution,including three arbitrary functions,is obtained for a (2+1)-dimensional modified dispersive water-wave (MDWW) equation by means of the WTC truncation method.Introducing proper multiple valued functions and Jacobi elliptic functions in the seed solution,special types of periodic folded waves are derived.In the long wave limit these periodic folded wave patterns may degenerate into single localized folded solitary wave excitations.The interactions of the periodic folded waves and the degenerated single folded solitary waves axe investigated graphically and found to be completely elastic.
Oblique wave-free potentials for water waves in constant finite depth
Maiti, Rajdeep; Basu, Uma; Mandal, B. N.
2015-06-01
In this paper, a method to construct oblique wave-free potentials in the linearised theory of water waves for water with uniform finite depth is presented in a systematic manner. The water has either a free surface or an ice-cover modelled as a thin elastic plate. For the case of free surface, the effect of surface tension may be neglected or taken into account. Here, the wave-free potentials are singular solutions of the modified Helmholtz equation, having singularity at a point in the fluid region and they satisfy the conditions at the upper surface and the bottom of water region and decay rapidly away from the point of singularity. These are useful in obtaining solutions to oblique water wave problems involving bodies with circular cross-sections such as long horizontal cylinders submerged or half-immersed in water of uniform finite depth with a free surface or an ice-cover modelled as a floating elastic plate. Finally, the forms of the upper surface related to the wave-free potentials constructed here are depicted graphically in a number of figures to visualize the wave motion. The results for non-oblique wave-free potentials and the upper surface wave-free potentials are obtained. The wave-free potentials constructed here will be useful in the mathematical study of water wave problems involving infinitely long horizontal cylinders, either half-immersed or completely immersed in water.
HYDRODYNAMICS THEORY AND CALCULATION IN WATER WAVE PUMP DESIGN
Institute of Scientific and Technical Information of China (English)
LIU Ying-xue; TAO Yi; LIU Gao-lian
2005-01-01
This paper introduces the hydrodynamics theory related to water wave pump.Water wave pump is a new type pump, which uses the particular quality of water wave and re-divides the inflow energy to increase the pressure of one part of the inflow water with the rest water flowing away freely.The research and development of such a pump is of importance and significant value and profitable social interest in that it can fully utilize the residual energy of natural source in industrial and civil water circle systems.Through hydrodynamics research and calculation, a series of valid design parameters were obtained and the predicted results achieved.
Wave transformation and shoreline water level on Funafuti Atoll, Tuvalu
Beetham, Edward; Kench, Paul S.; O'Callaghan, Joanne; Popinet, Stéphane
2016-01-01
The influence of sea swell (SS) waves, infragravity (IG) waves, and wave setup on maximum runup (Rmax) is investigated across different tidal stages on Fatato Island, Funafuti Atoll, Tuvalu. Field results illustrate that SS waves are tidally modulated at the shoreline, with comparatively greater wave attenuation and setup occurring at low tide versus high tide. A shoreward increase in IG wave height is observed across the 100 m wide reef flat at all tidal elevations, with no tidal modulation of IG wave height at the reef flat or island shoreline. A 1-D shock-capturing Green-Naghdi solver is used to replicate the field deployment and analyze Rmax. Model outputs for SS wave height, IG wave height and setup at the shoreline match field results with model skill >0.96. Model outputs for Rmax are used to identify the temporal window when geomorphic activity can occur on the beach face. During periods of moderate swell energy, waves can impact the beach face at spring low tide, due to a combination of wave setup and strong IG wave activity. Under mean wave conditions, the combined influence of setup, IG waves and SS waves results in interaction with island sediment at midtide. At high tide, SS and IG waves directly impact the beach face. Overall, wave activity is present on the beach face for 71% of the study period, a significantly longer duration than is calculated using mean water level and topographic data.
On periodic water waves with Coriolis effects and isobaric streamlines
Matioc, Anca-Voichita
2012-01-01
In this paper we prove that solutions of the f-plane approximation for equatorial geophysical deep water waves, which have the property that the pressure is constant along the streamlines and do not possess stagnation points,are Gerstner-type waves. Furthermore, for waves traveling over a flat bed, we prove that there are only laminar flow solutions with these properties.
On cusped solitary waves in finite water depth
Liao, Shijun
2013-01-01
It is well-known that the Camassa-Holm (CH) equation admits both of the peaked and cusped solitary waves in shallow water. However, it was an open question whether or not the exact wave equations can admit them in finite water depth. Besides, it was traditionally believed that cusped solitary waves, whose 1st-derivative tends to infinity at crest, are essentially different from peaked solitary ones with finite 1st-derivative. Currently, based on the symmetry and the exact water wave equations, Liao [1] proposed a unified wave model (UWM) for progressive gravity waves in finite water depth. The UWM admits not only all traditional smooth progressive waves but also the peaked solitary waves in finite water depth: in other words, the peaked solitary progressive waves are consistent with the traditional smooth ones. In this paper, in the frame of the linearized UWM, we further give, for the first time, the cusped solitary waves in finite water depth, and besides reveal a close relationship between the cusped and p...
An Internal Wave as a Frequency Filter for Surface Gravity Waves on Water
Lossow, K
2010-01-01
We consider one-dimensional model of the interaction between surface and the internal gravity water waves. The internal wave is modeled by its basic form: a non-dispersive field with a horizontal current that is uniform over all depth, insignificantly affected by the surface waves, while ignoring surface tension and wind growth/decay effects. The depth is infinite. Approximation for the height of the surface wave on the flow by the "elementary quasi stationary" solutions was found. It was shown that the flow acts as a frequency filter for gravitational waves on water.
Reduced-order prediction of rogue waves in two-dimensional deep-water waves
Farazmand, Mohammad; Sapsis, Themistoklis P.
2017-07-01
We consider the problem of large wave prediction in two-dimensional water waves. Such waves form due to the synergistic effect of dispersive mixing of smaller wave groups and the action of localized nonlinear wave interactions that leads to focusing. Instead of a direct simulation approach, we rely on the decomposition of the wave field into a discrete set of localized wave groups with optimal length scales and amplitudes. Due to the short-term character of the prediction, these wave groups do not interact and therefore their dynamics can be characterized individually. Using direct numerical simulations of the governing envelope equations we precompute the expected maximum elevation for each of those wave groups. The combination of the wave field decomposition algorithm, which provides information about the statistics of the system, and the precomputed map for the expected wave group elevation, which encodes dynamical information, allows (i) for understanding of how the probability of occurrence of rogue waves changes as the spectrum parameters vary, (ii) the computation of a critical length scale characterizing wave groups with high probability of evolving to rogue waves, and (iii) the formulation of a robust and parsimonious reduced-order prediction scheme for large waves. We assess the validity of this scheme in several cases of ocean wave spectra.
Rogue waves in a water tank: Experiments and modeling
Lechuga, Antonio
2013-04-01
Recently many rogue waves have been reported as the main cause of ship incidents on the sea. One of the main characteristics of rogue waves is its elusiveness: they present unexpectedly and disappear in the same wave. Some authors (Zakharov and al.2010) are attempting to find the probability of their appearances apart from studyingthe mechanism of the formation. As an effort on this topic we tried the generation of rogue waves in a water wave tank using a symmetric spectrum(Akhmediev et al. 2011) as input on the wave maker. The produced waves were clearly rogue waves with a rate (maximum wave height/ Significant wave height) of 2.33 and a kurtosis of 4.77 (Janssen 2003, Onorato 2006). These results were already presented (Lechuga 2012). Similar waves (in pattern aspect, but without being extreme waves) were described as crossing waves in a water tank(Shemer and Lichter1988). To go on further the next step has been to apply a theoretical model to the envelope of these waves. After some considerations the best model has been an analogue of the Ginzburg-Landau equation. This apparently amazing result is easily explained: We know that the Ginzburg-Landau model is related to some regular structures on the surface of a liquid and also in plasmas, electric and magnetic fields and other media. Another important characteristic of the model is that their solutions are invariants with respectto the translation group. The main aim of this presentation is to extract conclusions of the model and the comparison with the measured waves in the water tank.The nonlinear structure of waves and their regularity make suitable the use of the Ginzburg-Landau model to the envelope of generated waves in the tank,so giving us a powerful tool to cope with the results of our experiment.
Modeling Water Waves with Smoothed Particle Hydrodynamics
2013-09-30
flows, such as undertow, longshore currents, and rip currents. APPROACH The approach is based on improving various aspects of the SPH code ...Smoothed Particle Hydrodynamics ( SPH ) is a meshless numerical method that is being developed for the study of nearshore waves and other Navy needs. The...Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes
Spectral characteristics of high shallow water waves
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; AshokKumar, K.
.0081 and 3.3, respectively. By carrying out a multi-regression analysis, an empirical equation is arrived relating the JONSWAP parameters with significant wave height, peak wave period and mean wave period. It was found that the Scott spectra underestimate...
Planar shock wave sliding over a water layer
Rodriguez, V.; Jourdan, G.; Marty, A.; Allou, A.; Parisse, J.-D.
2016-08-01
In this work, we conduct experiments to study the interaction between a horizontal free water layer and a planar shock wave that is sliding over it. Experiments are performed at atmospheric pressure in a shock tube with a square cross section (200× 200 mm^2) for depths of 10, 20, and 30 mm; a 1500-mm-long water layer; and two incident planar shock waves having Mach numbers of 1.11 and 1.43. We record the pressure histories and high-speed visualizations to study the flow patterns, surface waves, and spray layers behind the shock wave. We observe two different flow patterns with ripples formed at the air-water interface for the weaker shock wave and the dispersion of a droplet mist for the stronger shock wave. From the pressure signals, we extract the delay time between the arrival of the compression wave into water and the shock wave in air at the same location. We show that the delay time evolves with the distance traveled over the water layer, the depth of the water layer, and the Mach number of the shock wave.
High order Hamiltonian water wave models with wave-breaking mechanism
Kurnia, R.; Groesen, van E.
2014-01-01
Based on the Hamiltonian formulation of water waves, using Hamiltonian consistent modelling methods, we derive higher order Hamiltonian equations by Taylor expansions of the potential and the vertical velocity around the still water level. The polynomial expansion in wave height is mixed with pseudo
A metasurface carpet cloak for electromagnetic, acoustic and water waves.
Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng
2016-01-29
We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak.
Nonlinear Low Frequency Water Waves in a Cylindrical Shell
Peng, H. W.; Wang, D. J.; Lee, C. B.
The experiment was carried out to study the low frequency surface waves due to the horizontal high frequency excitation. The feature of the phenomenon was that the big amplitude axisymmetric surface wave frequency was typically about 1/50 of the excitation frequency. The viscous effect of water was neglected as a first approximation in the earlier papers on this subject. In contrast, we found the viscosity was important to achieve the low frequency water wave with the cooperation of hundreds of "finger" waves. Photographs were taken with stroboscopic lighting and thereafter relevant quantitative results were obtained based on the measurements with Polytec Scanning Vibrometer PSV 400.
Interaction of modulated gravity water waves of finite depth
Giannoulis, Ioannis
2016-10-01
We consider the capillary-gravity water wave problem of finite depth with a flat bottom of one or two horizontal dimensions. We derive the modulation equations of leading and next-to-leading order in the hyperbolic scaling for three weakly amplitude-modulated plane wave solutions of the linearized problem in the absence of quadratic and cubic resonances. We justify the derived system of macroscopic equations in the case of gravity waves using the stability of the finite depth water wave problem on the time scale O (1 / ɛ).
A General Linear Wave Theory for Water Waves Propagating over Uneven Porous Bottoms
Institute of Scientific and Technical Information of China (English)
锁要红; 黄虎
2004-01-01
Starting from the widespread phenomena of porous bottoms in the near shore region, considering fully the diversity of bottom topography and wave number variation, and including the effect of evanescent modes, a general linear wave theory for water waves propagating over uneven porous bottoms in the near shore region is established by use of Green's second identity. This theory can be reduced to a number of the most typical mild-slope equations currently in use and provide a reliable research basis for follow-up development of nonlinear water wave theory involving porous bottoms.
Linear and nonlinear propagation of water wave groups
Pierson, W. J., Jr.; Donelan, M. A.; Hui, W. H.
1992-01-01
Results are presented from a study of the evolution of waveforms with known analytical group shapes, in the form of both transient wave groups and the cloidal (cn) and dnoidal (dn) wave trains as derived from the nonlinear Schroedinger equation. The waveforms were generated in a long wind-wave tank of the Canada Centre for Inland Waters. It was found that the low-amplitude transients behaved as predicted by the linear theory and that the cn and dn wave trains of moderate steepness behaved almost as predicted by the nonlinear Schroedinger equation. Some of the results did not fit into any of the available theories for waves on water, but they provide important insight on how actual groups of waves propagate and on higher-order effects for a transient waveform.
Nonlinear diffraction of water waves by offshore stuctures
Directory of Open Access Journals (Sweden)
Matiur Rahman
1986-01-01
Full Text Available This paper is concerned with a variational formulation of a nonaxisymmetric water wave problem. The full set of equations of motion for the problem in cylindrical polar coordinates is derived. This is followed by a review of the current knowledge on analytical theories and numerical treatments of nonlinear diffraction of water waves by offshore cylindrical structures. A brief discussion is made on water waves incident on a circular harbor with a narrow gap. Special emphasis is given to the resonance phenomenon associated with this problem. A new theoretical analysis is also presented to estimate the wave forces on large conical structures. Second-order (nonlinear effects are included in the calculation of the wave forces on the conical structures. A list of important references is also given.
Shallow water wave spectral characteristics along the eastern Arabian Sea
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Shanas, P.R.; Dubhashi, K.K.
The spectral characteristics of shallow water waves were studied at two locations along the eastern Arabian Sea during 2011. Wave spectra were single-peaked from June to October and predominantly double-peaked during the rest of the year. Even...
Steady water waves with multiple critical layers: interior dynamics
Ehrnström, Mats; Villari, Gabriele
2010-01-01
We study small-amplitude steady water waves with multiple critical layers. Those are rotational two-dimensional gravity-waves propagating over a perfect fluid of finite depth. It is found that arbitrarily many critical layers with cat's-eye vortices are possible, with different structure at different levels within the fluid. The corresponding vorticity depends linearly on the stream function.
Traveling Wave Solutions of the Benjamin-Bona-Mahony Water Wave Equations
Directory of Open Access Journals (Sweden)
A. R. Seadawy
2014-01-01
Full Text Available The modeling of unidirectional propagation of long water waves in dispersive media is presented. The Korteweg-de Vries (KdV and Benjamin-Bona-Mahony (BBM equations are derived from water waves models. New traveling solutions of the KdV and BBM equations are obtained by implementing the extended direct algebraic and extended sech-tanh methods. The stability of the obtained traveling solutions is analyzed and discussed.
Effects on PP waves and Rayleigh waves of water column approximation
Zhou, Y.; Ni, S.
2015-12-01
Spectral-element method (SEM) combines the flexibility of the finite-element method and the accuracy of the pseudo-spectral method. It can handle the complexity of the 3-D earth model, such as heterogeneity of velocity and density, anisotropy, anelasticity, sharp velocity and density contrasts, topography. And with water column approximation, it can also deal with oceans. Because of its powerful ability, there are a wide range of application of SEM in studies of PP waves and Rayleigh waves. PP wave and its precursors have been used in measuring topography of 410 km or 660 km. Rayleigh waves are the most recognizable part of the seismograms and have been broadly applied in crustal and uppermost mantle tomography. In global SEM simulation, oceans are usually assumed to be incompressible, which means that the entire water column moves as a whole as a result of the normal displacement of the seafloor. It is necessary to investigate the accuracy of water column approximation when thickness of ocean approaches wavelength of the wave in the ocean water. In this paper, based on plane wave assumption, we study both the accurate form and water column approximate form of effective boundary condition. The reflection coefficient equation of PP waves with effective boundary of water was derived. Accurate and approximate PP reflection coefficient with oceans in different depth is demonstrated. The formula of Rayleigh wave phase velocity dispersion with effective water boundary is also investigated. It is shown that water column approximation in global SEM simulation is not sufficient for some parts of the ocean.
Horizon effects with surface waves on moving water
Rousseaux, Germain; Mathis, Christian; Coullet, Pierre; Philbin, Thomas G; Leonhardt, Ulf
2010-01-01
Surface waves on a stationary flow of water are considered, in a linear model that includes the surface tension of the fluid. The resulting gravity-capillary waves experience a rich array of horizon effects when propagating against the flow. In some cases three horizons (points where the group velocity of the wave reverses) exist for waves with a single laboratory frequency. Some of these effects are familiar in fluid mechanics under the name of wave blocking, but other aspects, in particular waves with negative co-moving frequency and the Hawking effect, were overlooked until surface waves were investigated as examples of analogue gravity [R. Schuetzhold and W. G. Unruh W G, Phys. Rev. D 66 (2002) 044019]. A comprehensive presentation of the various horizon effects for gravity-capillary waves is given, with emphasis on the deep water/long wavelength case kh>>1 where many analytical results can be derived. A similarity of the state space of the waves to that of a thermodynamic system is pointed out.
Characterization of the Shock Wave Structure in Water
Teitz, Emilie Maria
The scientific community is interested in furthering the understanding of shock wave structures in water, given its implications in a wide range of applications; from researching how shock waves penetrate unwanted body tissues to studying how humans respond to blast waves. Shock wave research on water has existed for over five decades. Previous studies have investigated the shock response of water at pressures ranging from 1 to 70 GPa using flyer plate experiments. This report differs from previously published experiments in that the water was loaded to shock pressures ranging from 0.36 to 0.70 GPa. The experiment also utilized tap water rather than distilled water as the test sample. Flyer plate experiments were conducted in the Shock Physics Laboratory at Marquette University to determine the structure of shock waves within water. A 12.7 mm bore gas gun fired a projectile made of copper, PMMA, or aluminum at a stationary target filled with tap water. Graphite break pins in a circuit determined the initial projectile velocity prior to coming into contact with the target. A Piezoelectric timing pin (PZT pin) at the front surface of the water sample determined the arrival of the leading wave and a Photon Doppler Velocimeter (PDV) measured particle velocity from the rear surface of the water sample. The experimental results were compared to simulated data from a Eulerian Hydrocode called CTH [1]. The experimental results differed from the simulated results with deviations believed to be from experimental equipment malfunctions. The main hypothesis being that the PZT pin false triggered, resulting in measured lower than expected shock velocities. The simulated results were compared to published data from various authors and was within range.
Theoretical Study of Wave Breaking for Nonlinear Water Waves Propagating on a Sloping Bottom
Chen, Y. Y.; Hsu, H. C.; Li, M. S.
2012-04-01
In this paper, a third-order asymptotic solution in a Lagrangian framework describing nonlinear water wave propagation on the surface of a uniform sloping bottom is presented. A two-parameter perturbation method is used to develop a new mathematical derivation. The particle trajectories, wave pressure and Lagrangian velocity potential are obtained as a function of the nonlinear wave steepness and the bottom slope perturbed to third order. This theoretical solution in Lagrangian form satisfies state of the normal pressure at the free surface. The condition of the conservation of mass flux is examined in detail for the first time. The two important properties in Lagrangian coordinates, Lagrangian wave frequency and Lagrangian mean level, are included in the third-order solution. The solution can also be used to estimate the mean return current for waves progressing over the sloping bottom. The Lagrangian solution untangle the description of the features of wave shoaling in the direction of wave propagation from deep to shallow water, as well as the process of successive deformation of a wave profile and water particle trajectories leading to wave breaking. A series of experiment was conducted to validate the obtained theoretical solution. The proposed solution will be used to determine the wave shoaling and breaking process and the comparisons between the experimental and theoretical results are excellent. For example, the variations of phase velocity on sloping bottom are obtained by 7 set of two close wave gauges and the theoretical result could accurately predict the measured phase velocity. The theoretical wave breaking index can be derived by use of the kinematic stability parameter (K.P.S). The comparisons between the theory, experiment (present study, Iwagali et al.(1974), Deo et al.(2003) and Tsai et al.(2005)) and empirical formula of Goda (2004) for the breaking index(u/C) versus the relative water depth(d/L) under two different bottom slopes shows that the
Effects of water wave motion on pollutant transport in shallow coastal water
Institute of Scientific and Technical Information of China (English)
陶建华; 韩光
2002-01-01
Based on the study of the wave propagation, breaking, longshore current and the effect of wave on current structure in the near shore area with a mild bottom slope, the wave is considered to be an important dynamic factor for pollutant transportation in the coastal water. Numerical simulation shows that the pollutant will transfer along shore when the incident wave is at an angle to the shoreline. This phenomenon is very significant if the outfall is located in the surfzone. Therefore, in the design of sea outfall, to improve near shore environment, the water wave should be considered as an important hydrodynamic factor.
Standing Waves and Inquiry Using Water Droplets
Sinclair, Dina; Vondracek, Mark
2015-01-01
Most high school and introductory college physics classes study simple harmonic motion and various wave phenomena. With the majority of states adopting the Next Generation Science Standards and pushing students to explore the scientific process for themselves, there is a growing demand for hands-on inquiry activities that involve and develop more…
Standing Waves and Inquiry Using Water Droplets
Sinclair, Dina; Vondracek, Mark
2015-01-01
Most high school and introductory college physics classes study simple harmonic motion and various wave phenomena. With the majority of states adopting the Next Generation Science Standards and pushing students to explore the scientific process for themselves, there is a growing demand for hands-on inquiry activities that involve and develop more…
Explicit wave action conservation for water waves on vertically sheared flows
Quinn, B. E.; Toledo, Y.; Shrira, V. I.
2017-04-01
This paper addresses a major shortcoming of the current generation of wave models, namely their inability to describe wave propagation upon ambient currents with vertical shear. The wave action conservation equation (WAE) for linear waves propagating in horizontally inhomogeneous vertically-sheared currents is derived following Voronovich (1976). The resulting WAE specifies conservation of a certain depth-averaged quantity, the wave action, a product of the wave amplitude squared, eigenfunctions and functions of the eigenvalues of the boundary value problem for water waves upon a vertically sheared current. The formulation of the WAE is made explicit using known asymptotic solutions of the boundary value problem which exploit the smallness of the current magnitude compared to the wave phase velocity and/or its vertical shear and curvature; the adopted approximations are shown to be sufficient for most of the conceivable applications. In the limit of vanishing current shear, the new formulation reduces to that of Bretherton and Garrett (1968) without shear and the invariant is calculated with the current magnitude taken at the free surface. It is shown that in realistic oceanic conditions, the neglect of the vertical structure of the currents in wave modelling which is currently universal might lead to significant errors in wave amplitude. The new WAE which takes into account the vertical shear can be better coupled to modern circulation models which resolve the three-dimensional structure of the uppermost layer of the ocean.
Identification of resonance waves in open water channels
This article presents a procedure to determine the characteristics of open water channels required for controller and filter design, with special focus on the resonance waves. Also, a new simplified model structure for open water channels is proposed. The procedure applies System Identification tool...
Water wave transmission by an array of floating disks
Bennetts, Luke
2014-01-01
An experimental validation of theoretical models of transmission of regular water waves by large arrays of floating disks is presented. The experiments are conducted in a wave basin. The models are based on combined potential-flow and thin-plate theories, and the assumption of linear motions. A low-concentration array, in which disks are separated by approximately a disk diameter in equilibrium, and a high-concentration array, in which adjacent disks are almost touching in equilibrium, are used for the experiments. The proportion of incident wave energy transmitted by the disks is presented as a function of wave period, and for different wave amplitudes. Results indicate that the models predict wave energy transmission accurately for small-amplitude waves and low-concentration arrays. Discrepancies for large-amplitude waves and high-concentration arrays are attributed to wave overwash of the disks and collisions between disks. Validation of model predictions of rigid-body motions of a solitary disk are also p...
Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets
Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, Youngpak
2015-09-01
Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet-height and diameter- and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.
Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets.
Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, YoungPak
2015-09-10
Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet-height and diameter- and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.
Compressive spectral method for the simulation of the water waves
Bayindir, Cihan
2015-01-01
In this paper an approach for decreasing the computational effort required for the spectral simulations of the water waves is introduced. Signals with majority of the components zero, are known as the sparse signals. Like majority of the signals in the nature it can be realized that water waves are sparse either in time or in the frequency domain. Using the sparsity property of the water waves in the time or in the frequency domain, the compressive sampling algorithm can be used as a tool for improving the performance of the spectral simulation of the water waves. The methodology offered in this paper depends on the idea of using a smaller number of spectral components compared to the classical spectral method with a high number of components. After performing the time integration with a smaller number of spectral components and using the compressive sampling technique, it is shown that the water wave field can be reconstructed with a significantly better efficiency compared to the classical spectral method w...
Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets
Yoo, Young Joon; Ju, Sanghyun; Park, Sang Yoon; Ju Kim, Young; Bong, Jihye; Lim, Taekyung; Kim, Ki Won; Rhee, Joo Yull; Lee, YoungPak
2015-01-01
Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet–height and diameter– and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials. PMID:26354891
System for harvesting water wave energy
Energy Technology Data Exchange (ETDEWEB)
Wang, Zhong Lin; Su, Yanjie; Zhu, Guang; Chen, Jun
2016-07-19
A generator for harvesting energy from water in motion includes a sheet of a hydrophobic material, having a first side and an opposite second side, that is triboelectrically more negative than water. A first electrode sheet is disposed on the second side of the sheet of a hydrophobic material. A second electrode sheet is disposed on the second side of the sheet of a hydrophobic material and is spaced apart from the first electrode sheet. Movement of the water across the first side induces an electrical potential imbalance between the first electrode sheet and the second electrode sheet.
Calming the Waters or Riding the Waves?
DEFF Research Database (Denmark)
Rydén, Pernille; Kottika, Efthymia; Hossain, Muhammad Ismail;
Traditional consumer anger management tends to be compromising rather than empowering the brand. This paper conceptualizes and provides a case example on how consumer empowerment and negative emotions can in fact create opportunities for companies to ride the waves of consumer anger in a way...... that strengthens their brand. The consumers are empowered by ‘letting this anger out’, from which firms can gain huge attention. Companies can utilize such situations to inform people on their brands’ core values, and initiate discussions of larger societal relevance, which improves the brand awareness and value...
Wave breaking and shock waves for a periodic shallow water equation.
Escher, Joachim
2007-09-15
This paper is devoted to the study of a recently derived periodic shallow water equation. We discuss in detail the blow-up scenario of strong solutions and present several conditions on the initial profile, which ensure the occurrence of wave breaking. We also present a family of global weak solutions, which may be viewed as global periodic shock waves to the equation under discussion.
Influences on water-hammer wave shape: an experimental study
Traudt, T.; Bombardieri, C.; Manfletti, C.
2016-09-01
Water-hammer phenomena are of strong interest in a number of different industrial fields, amongst which the space industry. Here the priming of feedlines during start-up of an engine as well as the rapid closing of valves upon shutdown may lead to pressure peaks symptomatic of a water-hammer wave. Test benches used to conduct tests on future as well as current engines are also sensitive to water-hammer waves traveling along their feedlines. To enhance the understanding of water-hammer, we investigated different configurations and their influence on the wave shape in the frequency domain. The configurations feature a coiled pipe setup with a support structure and without a support structure. Two other phenomena will be presented. We found a beat phenomenon which is likely to be the so called Poisson-coupling beat. Finally we will show that the second water-hammer peak can reach pressures a lot higher than the first peak by additive interference of the primary and secondary water-hammer wave.
Practical use of variational principles for modeling water waves
Clamond, Didier
2010-01-01
This paper describes a method for deriving approximate equations for water waves. The method is based on a `relaxed' variational principle, i.e., on a Lagrangian involving as many variables as possible. This formulation is particularly suitable for the construction of approximate water wave models, since it allows more freedom while preserving the variational structure. The advantages of this relaxed formulation are illustrated with various examples in shallow and deep waters, as well as arbitrary depths. Using subordinate constraints (e.g., irrotationality and free surface impermeability) in various combinations, several model equations are derived, some being well-known, other being new. The models obtained are studied analytically and exact travelling wave solutions are constructed when possible.
Experimental evidence of wave chaos from a double slit experiment with water surface waves.
Tang, Yunfei; Shen, Yifeng; Yang, Jiong; Liu, Xiaohan; Zi, Jian; Li, Baowen
2008-10-01
In this paper, we report experimental evidence of wave chaos using the double slit water surface wave experiment. We demonstrate that classical dynamics of a domain manifests itself in the interference patterns after the diffraction behind the double slit. For a domain whose classical dynamics is integrable clear interference fringes can be observed behind the double slits; for a domain whose classical dynamics is chaotic, however, interference fringes can totally disappear. Our experimental results clearly demonstrate that the centuries-old double slit experiment can render an excellent tool to observe the manifestations of wave chaos.
Non-classical dispersive shock waves in shallow water
Sprenger, Patrick; Hoefer, Mark
2016-11-01
A classical model for shallow water waves with strong surface tension is the Kawahara equation, which is the Korteweg-de Vries (KdV) including a fifth order derivative term. A particular problem of interest to these types of equations is step initial data, known as the Riemann problem, which results in a shock in finite time. Unlike classical shock waves, where a discontinuity is resolved by dissipation, the dispersive regularization results in the discontinuity resolved as a dispersive shock wave (DSW). When parameter choices result in non-convex dispersion, three distinct dynamic regimes are observed that can be characterized solely by the amplitude of the initial step. For small jumps, a perturbed KdV DSW with positive polarity and orientation is generated, accompanied by small amplitude radiation from an embedded solitary wave leading edge, termed a radiating DSW. For moderate jumps, a crossover regime is observed with waves propagating forward and backward from the sharp transition region. For sufficiently large jumps, a new type of DSW is observed we term a translating DSW were a partial, non-monotonic, negative solitary wave at the trailing edge is connected to an interior nonlinear periodic wave and exhibits features common to both dissipative and dispersive shock waves.
Deep-water bedforms induced by refracting Internal Solitary Waves
Falcini, Federico; Droghei, Riccardo; Casalbore, Daniele; Martorelli, Eleonora; Mosetti, Renzo; Sannino, Gianmaria; Santoleri, Rosalia; Latino Chiocci, Francesco
2017-04-01
Subaqueous bedforms (or sand waves) are typically observed in those environments that are exposed to strong currents, characterized by a dominant unidirectional flow. However, sand-wave fields may be also observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs), induced by tides, can produce an effective, unidirectional boundary flow filed that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.
Wave Loads on Ships Sailing in Restricted Water Depth
DEFF Research Database (Denmark)
Vidic-Perunovic, Jelena; Jensen, Jørgen Juncher
2003-01-01
be specified anyhow. Usually, two-dimensional strip theories, either linear or non-linear, are applied for actual design cases and these theories are normally based on incident deep-water waves and furthermore apply added mass and damping calculations based on infinite water depth. Only a few papers have...... in the past addressed the influence of water depth on the ship response. In an early work Kim (1968) presented results for the variation of the added mass and hydrodynamic damping and for the heave and pitch motion for a Series 60 model using a relative motion strip theory formulation. A significant reduction...... in ship motion with decreasing keel clearance was observed. In the present paper a rigorous implementation of finite water depth in the consistent linear strip theory by Salvesen et al. (1970) is presented together with results for the variation of the motion and wave-induced bending moment with water...
Water vapor estimation using digital terrestrial broadcasting waves
Kawamura, S.; Ohta, H.; Hanado, H.; Yamamoto, M. K.; Shiga, N.; Kido, K.; Yasuda, S.; Goto, T.; Ichikawa, R.; Amagai, J.; Imamura, K.; Fujieda, M.; Iwai, H.; Sugitani, S.; Iguchi, T.
2017-03-01
A method of estimating water vapor (propagation delay due to water vapor) using digital terrestrial broadcasting waves is proposed. Our target is to improve the accuracy of numerical weather forecast for severe weather phenomena such as localized heavy rainstorms in urban areas through data assimilation. In this method, we estimate water vapor near a ground surface from the propagation delay of digital terrestrial broadcasting waves. A real-time delay measurement system with a software-defined radio technique is developed and tested. The data obtained using digital terrestrial broadcasting waves show good agreement with those obtained by ground-based meteorological observation. The main features of this observation are, no need for transmitters (receiving only), applicable wherever digital terrestrial broadcasting is available and its high time resolution. This study shows a possibility to estimate water vapor using digital terrestrial broadcasting waves. In the future, we will investigate the impact of these data toward numerical weather forecast through data assimilation. Developing a system that monitors water vapor near the ground surface with time and space resolutions of 30 s and several kilometers would improve the accuracy of the numerical weather forecast of localized severe weather phenomena.
Generation of Focused Shock Waves in Water for Biomedical Applications
Lukeš, Petr; Šunka, Pavel; Hoffer, Petr; Stelmashuk, Vitaliy; Beneš, Jiří; Poučková, Pavla; Zadinová, Marie; Zeman, Jan
The physical characteristics of focused two-successive (tandem) shock waves (FTSW) in water and their biological effects are presented. FTSW were generated by underwater multichannel electrical discharges in a highly conductive saline solution using two porous ceramic-coated cylindrical electrodes of different diameter and surface area. The primary cylindrical pressure wave generated at each composite electrode was focused by a metallic parabolic reflector to a common focal point to form two strong shock waves with a variable time delay between the waves. The pressure field and interaction between the first and the second shock waves at the focus were investigated using schlieren photography and polyvinylidene fluoride (PVDF) shock gauge sensors. The largest interaction was obtained for a time delay of 8-15 μs between the waves, producing an amplitude of the negative pressure phase of the second shock wave down to -80 MPa and a large number of cavitations at the focus. The biological effects of FTSW were demonstrated in vitro on damage to B16 melanoma cells, in vivo on targeted lesions in the thigh muscles of rabbits and on the growth delay of sarcoma tumors in Lewis rats treated in vivo by FTSW, compared to untreated controls.
An inexpensive instrument for measuring wave exposure and water velocity
Figurski, J.D.; Malone, D.; Lacy, J.R.; Denny, M.
2011-01-01
Ocean waves drive a wide variety of nearshore physical processes, structuring entire ecosystems through their direct and indirect effects on the settlement, behavior, and survivorship of marine organisms. However, wave exposure remains difficult and expensive to measure. Here, we report on an inexpensive and easily constructed instrument for measuring wave-induced water velocities. The underwater relative swell kinetics instrument (URSKI) is a subsurface float tethered by a short (<1 m) line to the seafloor. Contained within the float is an accelerometer that records the tilt of the float in response to passing waves. During two field trials totaling 358 h, we confirmed the accuracy and precision of URSKI measurements through comparison to velocities measured by an in situ acoustic Doppler velocimeter and those predicted by a standard swell model, and we evaluated how the dimensions of the devices, its buoyancy, and sampling frequency can be modified for use in a variety of environments.
Similarity solution of the shock wave propagation in water
Directory of Open Access Journals (Sweden)
Muller M.
2007-11-01
Full Text Available This paper presents the possibility of calculation of propagation of a shock wave generated during the bubble collapse in water including the dissipation effect. The used semi-empirical model is based on an assumption of similarity between the shock pressure time profiles in different shock wave positions. This assumption leads to a system of two ordinary differential equations for pressure jump and energy at the shock front. The NIST data are used for the compilation of the equation of state, which is applied to the calculation of the shock wave energy dissipation. The initial conditions for the system of equations are obtained from the modified method of characteristics in the combination with the differential equations of cavitation bubble dynamics, which considers viscous compressible liquid with the influence of surface tension. The initial energy of the shock wave is estimated from the energy between the energies of the bubble growth to the first and second maximum bubble radii.
A Stochastic Nonlinear Water Wave Model for Efficient Uncertainty Quantification
Bigoni, Daniele; Eskilsson, Claes
2014-01-01
A major challenge in next-generation industrial applications is to improve numerical analysis by quantifying uncertainties in predictions. In this work we present a stochastic formulation of a fully nonlinear and dispersive potential flow water wave model for the probabilistic description of the evolution waves. This model is discretized using the Stochastic Collocation Method (SCM), which provides an approximate surrogate of the model. This can be used to accurately and efficiently estimate the probability distribution of the unknown time dependent stochastic solution after the forward propagation of uncertainties. We revisit experimental benchmarks often used for validation of deterministic water wave models. We do this using a fully nonlinear and dispersive model and show how uncertainty in the model input can influence the model output. Based on numerical experiments and assumed uncertainties in boundary data, our analysis reveals that some of the known discrepancies from deterministic simulation in compa...
On the kurtosis of ocean waves in deep water
Fedele, Francesco
2014-01-01
In this paper, we revisit Janssen's (2003) formulation for the dynamic excess kurtosis of weakly nonlinear gravity waves in deep water. For narrowband directional spectra, the formulation is expressed as a sixfold integral that depends upon the Benjamin-Feir index and the parameter $R=\
Reflection in variational models for linear water waves
Klopman, Gert; Dingemans, Maarten W.
2010-01-01
The reflection characteristics are analysed for a series of Hamiltonian water-wave models. These variational models have been derived by applying a Boussinesq-like approach to the vertical flow-structure. Both parabolic and hyperbolic-cosine approximations to the vertical structure are considered. M
On a shallow water wave equation
Clarkson, P A; Peter A Clarkson; Elizabeth L Mansfield
1994-01-01
In this paper we study a shallow water equation derivable using the Boussinesq approximation, which includes as two special cases, one equation discussed by Ablowitz et. al. [Stud. Appl. Math., 53 (1974) 249--315] and one by Hirota and Satsuma [J. Phys. Soc. Japan}, 40 (1976) 611--612]. A catalogue of classical and nonclassical symmetry reductions, and a Painleve analysis, are given. Of particular interest are families of solutions found containing a rich variety of qualitative behaviours. Indeed we exhibit and plot a wide variety of solutions all of which look like a two-soliton for t>0 but differ radically for t<0. These families arise as nonclassical symmetry reduction solutions and solutions found using the singular manifold method. This example shows that nonclassical symmetries and the singular manifold method do not, in general, yield the same solution set. We also obtain symmetry reductions of the shallow water equation solvable in terms of solutions of the first, third and fifth Painleve equations...
Explicit wave action conservation for water waves on vertically sheared flows
Quinn, Brenda; Toledo, Yaron; Shrira, Victor
2016-04-01
Water waves almost always propagate on currents with a vertical structure such as currents directed towards the beach accompanied by an under-current directed back toward the deep sea or wind-induced currents which change magnitude with depth due to viscosity effects. On larger scales they also change their direction due to the Coriolis force as described by the Ekman spiral. This implies that the existing wave models, which assume vertically-averaged currents, is an approximation which is far from realistic. In recent years, ocean circulation models have significantly improved with the capability to model vertically-sheared current profiles in contrast with the earlier vertically-averaged current profiles. Further advancements have coupled wave action models to circulation models to relate the mutual effects between the two types of motion. Restricting wave models to vertically-averaged non-turbulent current profiles is obviously problematic in these cases and the primary goal of this work is to derive and examine a general wave action equation which accounts for these shortcoming. The formulation of the wave action conservation equation is made explicit by following the work of Voronovich (1976) and using known asymptotic solutions of the boundary value problem which exploit the smallness of the current magnitude compared to the wave phase velocity and/or its vertical shear and curvature. The adopted approximations are shown to be sufficient for most of the conceivable applications. This provides correction terms to the group velocity and wave action definition accounting for the shear effects, which are fitting for application to operational wave models. In the limit of vanishing current shear, the new formulation reduces to the commonly used Bretherton & Garrett (1968) no-shear wave action equation where the invariant is calculated with the current magnitude taken at the free surface. It is shown that in realistic oceanic conditions, the neglect of the vertical
The Whitham Equation as a Model for Surface Water Waves
Moldabayev, Daulet; Dutykh, Denys
2014-01-01
The Whitham equation was proposed as an alternate model equation for the simplified description of uni-directional wave motion at the surface of an inviscid fluid. As the Whitham equation incorporates the full linear dispersion relation of the water wave problem, it is thought to provide a more faithful description of shorter waves of small amplitude than traditional long wave models such as the KdV equation. In this work, we identify a scaling regime in which the Whitham equation can be derived from the Hamiltonian theory of surface water waves. The Whitham equation is integrated numerically, and it is shown that the equation gives a close approximation of inviscid free surface dynamics as described by the Euler equations. The performance of the Whitham equation as a model for free surface dynamics is also compared to two standard free surface models: the KdV and the BBM equation. It is found that in a wide parameter range of amplitudes and wavelengths, the Whitham equation performs on par with or better tha...
Molding acoustic, electromagnetic and water waves with a single cloak
Xu, Jun
2015-06-09
We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves. © 2015, Nature Publishing Group. All rights reserved.
Molding acoustic, electromagnetic and water waves with a single cloak.
Xu, Jun; Jiang, Xu; Fang, Nicholas; Georget, Elodie; Abdeddaim, Redha; Geffrin, Jean-Michel; Farhat, Mohamed; Sabouroux, Pierre; Enoch, Stefan; Guenneau, Sébastien
2015-06-09
We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves.
Permeability recovery of damaged water sensitive core using ultrasonic waves.
Khan, Nasir; Pu, Chunsheng; Li, Xu; He, Yanlong; Zhang, Lei; Jing, Cheng
2017-09-01
It is imperative to recover the well productivity lose due to formation damage nearby wellbore during variant well operations. Some indispensable issues in conventional techniques make ultrasonic technology more attractive due to simple, reliable, favorable, cost-effective, and environment friendly nature. This study proposes the independent and combined use of ultrasonic waves and chemical agents for the treatment of already damaged core samples caused by exposure to distilled water. Results elucidate that ultrasonic waves with optimum (20kHz, 1000W) instead of maximum frequency and power worked well in the recovery owing to peristaltic transport caused by matching of natural frequency with acoustic waves frequency. In addition, hundred minutes was investigated as optimum irradiation time which provided ample time span to detach fine loosely suspended particles. However, further irradiation adversely affected the damaged permeability recovery. Moreover, permeability improvement attributes to cavitation due to ultrasonic waves propagation through fluid contained in porous medium and thermal energy generated by three different ways. Eventually, experimental outcomes indicated that maximum (25.3%) damaged permeability recovery was witnessed by applying ultrasonic waves with transducer #2 (20kHz and 1000W) and optimum irradiation timeframe (100min). This recovery was further increased to 45.8% by applying chemical agent and optimum ultrasonic waves simultaneously. Copyright © 2017 Elsevier B.V. All rights reserved.
Continuous Dependence on the Density for Stratified Steady Water Waves
Chen, Robin Ming; Walsh, Samuel
2016-02-01
There are two distinct regimes commonly used to model traveling waves in stratified water: continuous stratification, where the density is smooth throughout the fluid, and layer-wise continuous stratification, where the fluid consists of multiple immiscible strata. The former is the more physically accurate description, but the latter is frequently more amenable to analysis and computation. By the conservation of mass, the density is constant along the streamlines of the flow; the stratification can therefore be specified by prescribing the value of the density on each streamline. We call this the streamline density function. Our main result states that, for every smoothly stratified periodic traveling wave in a certain small-amplitude regime, there is an L ∞ neighborhood of its streamline density function such that, for any piecewise smooth streamline density function in that neighborhood, there is a corresponding traveling wave solution. Moreover, the mapping from streamline density function to wave is Lipschitz continuous in a certain function space framework. As this neighborhood includes piecewise smooth densities with arbitrarily many jump discontinues, this theorem provides a rigorous justification for the ubiquitous practice of approximating a smoothly stratified wave by a layered one. We also discuss some applications of this result to the study of the qualitative features of such waves.
Wavefront modulation of water surface wave by a metasurface
Institute of Scientific and Technical Information of China (English)
孙海涛; 程营; 王敬时; 刘晓峻
2015-01-01
We design a planar metasurface to modulate the wavefront of a water surface wave (WSW) on a deep sub-wavelength scale. The metasurface is composed of an array of coiling-up-space units with specially designed parameters, and can take on the work of steering the wavefront when it is pierced into water. Like their acoustic counterparts, the modulation of WSW is ascribed to the gradient phase shift of the coiling-up-space units, which can be perfectly tuned by changing the coiling plate length and channel number inside the units. According to the generalized Snell’s law, negative refraction and‘driven’ surface mode of WSW are also demonstrated at certain incidences. Specially, the transmitted WSW could be efficiently guided out by linking a symmetrically-corrugated channel in‘driven’ surface mode. This work may have potential applications in water wave energy extraction and coastal protection.
On the Turbulence Beneath Finite Amplitude Water Waves
Babanin, Alexander V
2015-01-01
The paper by Beya et al. (2012, hereinafter BPB) has a general title of Turbulence Beneath Finite Amplitude Water Waves, but is solely dedicated to discussing the experiment by Babanin and Haus (2009, hereinafter BH) who conducted measurements of wave-induced non-breaking turbulence by particle image velocimetry (PIV). The authors of BPB conclude that their observations contradict those of BH. Here we argue that the outcomes of BPB do not contradict BH. In addition, although the main conclusion of BPB is that there is no turbulence observed in their experiment, it actually is observed.
Lecture Notes for the Course in Water Wave Mechanics
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Frigaard, Peter; Burcharth, Hans F.
The present notes are written for the course in water wave mechanics given on the 7th semester of the education in civil engineering at Aalborg University. The prerequisites for the course are the course in fluid dynamics also given on the 7th semester and some basic mathematical and physical...... knowledge. The course is at the same time an introduction to the course in coastal hydraulics on the 8th semester. The notes cover the first four lectures of the course: • Definitions. Governing equations and boundary conditions. • Derivation of velocity potential for linear waves. Dispersion relationship...
Lecture Notes for the Course in Water Wave Mechanics
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Frigaard, Peter
The present notes are written for the course in water wave mechanics given on the 7th semester of the education in civil engineering at Aalborg University. The prerequisites for the course are the course in fluid dynamics also given on the 7th semester and some basic mathematical and physical...... knowledge. The course is at the same time an introduction to the course in coastal hydraulics on the 8th semester. The notes cover the following five lectures: 1. Definitions. Governing equations and boundary conditions. Derivation of velocity potential for linear waves. Dispersion relationship. 2. Particle...
Guided Waves in Wind Turbine Monopiles Immersed in Water
Zernov, V.; Pradkin, L.; Mudge, P.
2010-02-01
We study the guided waves in a structure which consists of two overlapping steel plates, with the overlapping section grouted. This geometry is often encountered in support structures of large industrial off-shore constructions, such as wind turbine monopiles. It has been recognized for some time that the guided wave technology offers distinctive advantages for the ultrasonic inspections and health monitoring of structures of this extent. It is demonstrated that there exist advantageous operational regimes of relevant ultrasonic transducers which result in significant improvement of the inspection range, even when the structures are totally submerged in water.
Investigation of water wave breaking phenomena: experiment and theory
Chybicki, W.; Staroszczyk, R.
2009-09-01
The phenomenon of water wave breaking and the link between the wave breaking and the velocities of water particles on the free surface are investigated. Results of experiments carried out in a laboratory flume are presented, and then compared with predictions of a theoretical model that has also been outlined in the paper. The experiments have been conducted in a 64 m long water channel at the Institute of Hydro-Engineering of the Polish Academy of Sciences in Gdansk, Poland. The experiments have been focused on measurements of Lagrangian velocities of fluid particles on the free surface of water. The motion of the fluid was induced by a piston-type wave maker that generated short trains of mono- and bi-chromatic waves propagating in water of a mean-level depth of 40 cm, in which an underwater inclined ramp, of a slope of 10 per cent and a height of 30 cm, was mounted. The height of a generated wave was adjusted in such a way that the wave breaking occurred in a chosen location over the ramp. The wave breaking was of a spilling type. The fluid particle velocities were measured by putting floating markers (small plastic beads of densities very close to that of water) on the free surface of water, and then by recording their movements by means of a camera during the process of wave breaking. The displacements of the markers in time were determined from the analysis of their positions in successive frames of the film. In the paper also a theoretical model describing the propagation of waves over an uneven bottom is presented. The model is formulated in the Lagrangian variables. A key simplification on which the proposed theory is based is that the vertical displacements of fluid particles are related to an assumed variation of the horizontal displacements, the continuity equation, and the boundary condition at the bottom. The momentum equation, derived by applying a variational principle and making use of the latter assumptions, is equivalent to the Boussinesq
Empirical formula for wave length of ocean wave in finite depth water
Institute of Scientific and Technical Information of China (English)
GUAN Changlong; JU Hongmei
2005-01-01
In this paper, function characteristics of dispersion of ocean wave in finite depth water were analyzed systematically. The functional form of the fitting function is reasonably proposed, in which the parameters are optimally determined by the least square method (LSM). For infinitely deep and extremely shallow water,the fitting function fits strictly the dispersion to be fitted. A new technique is presented in application of LSM.An empirical formula with maximum error of less than 0.5% for computing wavelength in finite depth water is presented for practical applications.
Water vapor: An extraordinary terahertz wave source under optical excitation
Energy Technology Data Exchange (ETDEWEB)
Johnson, Keith [Massachusetts Institute of Technology, PO Box 380792, Cambridge, MA 02238-0792 (United States); HydroElectron Ventures Inc., 1303 Greene Avenue Suite 102, Westmount, QC, H3Z 2A7 (Canada)], E-mail: kjohnson@mit.edu; Price-Gallagher, Matthew [HydroElectron Ventures Inc., 1303 Greene Avenue Suite 102, Westmount, QC, H3Z 2A7 (Canada); Mamer, Orval; Lesimple, Alain [Mass Spectroscopy Unit, 740 Dr. Penfield, Suite 5300, McGill University, Montreal, QC, H3A 1A4 (Canada); Fletcher, Clark [HydroElectron Ventures Inc., 1303 Greene Avenue Suite 102, Westmount, QC, H3Z 2A7 (Canada); Chen Yunqing; Lu Xiaofei; Yamaguchi, Masashi; Zhang, X.-C. [W.M. Keck Laboratory for Terahertz Science, Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)
2008-09-15
In modern terahertz (THz) sensing and imaging spectroscopy, water is considered a nemesis to be avoided due to strong absorption in the THz frequency range. Here we report the first experimental demonstration and theoretical implications of using femtosecond laser pulses to generate intense broadband THz emission from water vapor. When we focused an intense laser pulse in water vapor contained in a gas cell or injected from a gas jet nozzle, an extraordinarily strong THz field from optically excited water vapor is observed. Water vapor has more than 50% greater THz generation efficiency than dry nitrogen. It had previously been assumed that the nonlinear generation of THz waves in this manner primarily involves a free-electron plasma, but we show that the molecular structure plays an essential role in the process. In particular, we found that THz wave generation from H{sub 2}O vapor is significantly stronger than that from D{sub 2}O vapor. Vibronic activities of water cluster ions, occurring naturally in water vapor, may possibly contribute to the observed isotope effect along with rovibrational contributions from the predominant monomers.
Reflective measurement of water concentration using millimeter wave illumination
Sung, Shijun; Bennett, David; Taylor, Zachary; Bajwa, Neha; Tewari, Priyamvada; Maccabi, Ashkan; Culjat, Martin; Singh, Rahul; Grundfest, Warren
2011-04-01
THz and millimeter wave technology have shown the potential to become a valuable medical imaging tool because of its sensitivity to water and safe, non-ionizing photon energy. Using the high dielectric constant of water in these frequency bands, reflectionmode THz sensing systems can be employed to measure water content in a target with high sensitivity. This phenomenology may lead to the development of clinical systems to measure the hydration state of biological targets. Such measurements may be useful in fast and convenient diagnosis of conditions whose symptoms can be characterized by changes in water concentration such as skin burns, dehydration, or chemical exposure. To explore millimeter wave sensitivity to hydration, a reflectometry system is constructed to make water concentration measurements at 100 GHz, and the minimum detectable water concentration difference is measured. This system employs a 100 GHz Gunn diode source and Golay cell detector to perform point reflectivity measurements of a wetted polypropylene towel as it dries on a mass balance. A noise limited, minimum detectable concentration difference of less than 0.5% by mass can be detected in water concentrations ranging from 70% to 80%. This sensitivity is sufficient to detect hydration changes caused by many diseases and pathologies and may be useful in the future as a diagnostic tool for the assessment of burns and other surface pathologies.
Variational space–time (dis)continuous Galerkin method for nonlinear free surface water waves
Gagarina, E.; Ambati, V.R.; Vegt, van der J.J.W.; Bokhove, O.
2014-01-01
A new variational finite element method is developed for nonlinear free surface gravity water waves using the potential flow approximation. This method also handles waves generated by a wave maker. Its formulation stems from Miles’ variational principle for water waves together with a finite element
Wang, Ying; Guo, Yunxi
2017-09-01
In this paper, we developed, for the first time, the exact expressions of several periodic travelling wave solutions and a solitary wave solution for a shallow water wave model of moderate amplitude. Then, we present the existence theorem of the global weak solutions. Finally, we prove the stability of solution in L1(R) space for the Cauchy problem of the equation.
Wang, Ying; Guo, Yunxi
2016-07-01
In this paper, we developed, for the first time, the exact expressions of several periodic travelling wave solutions and a solitary wave solution for a shallow water wave model of moderate amplitude. Then, we present the existence theorem of the global weak solutions. Finally, we prove the stability of solution in L1(R) space for the Cauchy problem of the equation.
Numerical study of surface water waves generated by mass movement
Energy Technology Data Exchange (ETDEWEB)
Ghozlani, Belgacem; Hafsia, Zouhaier; Maalel, Khlifa, E-mail: ghozlanib@yahoo.fr [Ecole Nationale d' Ingenieurs de Tunis, Laboratoire de Modelisation en ' Hydraulique et Environnement, BP 37, Le Belvedere, 1002 Tunis (Tunisia)
2013-10-01
In this paper waves generated by two-dimensional mass movement are simulated using a numerical model based on the full hydrodynamic coupling between rigid-body motion and ambient fluid flow. This approach has the capability to represent the dynamics of the moving rigid body, which avoids the need to prescribe the body velocity based on the data measurements. This model is implemented in the CFX code and uses the Reynolds average Navier-Stokes equations solver coupled to the recently developed immersed solid technique. The latter technique allows us to follow implicitly the motion of the solid block based on the rigid body solver. The volume-of-fluid method is used to track the free surface locations. The accuracy of the present model is firstly examined against the simple physical case of a freely falling rigid body into water reproducing Scott Russell's solitary waves. More complex and realistic simulations of aerial and submarine mass-movement, simulated by a rigid wedge sliding into water along a 45 Degree-Sign slope, are then performed. Simulated results of the aerial mass movement show the complex flow patterns in terms of the velocity fields and free surface profiles. Results are in good agreement with the available experimental data. In addition, the physical processes associated with the generation of water wave by two-dimensional submarine mass-movement are explored. The effects of the initial submergence and specific gravity on the slide mass kinematics and maximum wave amplitude are investigated. The terminal velocity and initial acceleration of the slide mass are well predicted when compared to experimental results. It is found that the initial submergence did not have a significant effect on the initial acceleration of the slide block centre of mass. However, it depends nonlinearly on the specific gravity. The maximum wave amplitude and the time at which it occurred are also presented as a function of the initial submergence and specific gravity
Inclined boom system with hydrofoil for waters with waves
Energy Technology Data Exchange (ETDEWEB)
Wong, K.V.; Miller, M.K.; Boccabella, A. [Miami Univ., Coral Gables, FL (United States)
2005-07-01
It is inevitable that spills and accidental discharges of oil will occur while transporting oil in tanker ships. Although marine oil spills have been reduced due to doubled hulled tankers and environmental regulations, oil spills still present a threat to bays, shorelines and marine life. Therefore, oil response must be rapid, effective and thorough. An innovative oil containment boom that can collect oil in waters with waves was designed and constructed. Booms contain the spread of oil after a spill and also concentrate oil into thicker layers, making recovery more effective. They can be used to direct and channel oil slicks along desired paths into skimming equipment. This newly designed boom includes a ramp placed at an angle of 12 degrees from the horizontal. Three collection zones are used in which oil is pumped out to an oil storage tank. The design incorporates a hydrofoil for stability. The hydrofoil counteracts the lift created by the ramp. Results show that the hydrofoils were effective at high flow rates and waves. At low flow rates, the boom units relied mostly on the Styrofoam flotation devices for stability. For experiments without waves, the collection efficiency ranged from 95.9 per cent to 99.6 per cent. At least 3 forward waves were created for the high and intermediate velocities. Five forward waves were created at the low velocity. The collection efficiency ranged from 51.7 per cent to 69.3 per cent. 14 refs., 2 tabs., 10 figs.
Surface water waves interaction in a circular vessel with oscillating walls.
Denissenko, Petr; Hsieh, Din-Yu
1998-11-01
Surface water waves appeared in a circular elastic vessel (modelled after the Chinese antique "Dragon Wash") are studied experimentally. Interaction of different wave modes are investigated. For small amplitude of wall oscillations, only the axisymmetric capillary wave mode, which is hardly visible to naked eyes, exists. When the amplitude is increased, half-frequency circumferential wave appears. Further increase of amplitude leads to chaotic behavior of surface waves. For large amplitudes, water drops jumping from edge regions are observed. Then, excitation of different modes of low frequency axisymmetric gravity waves may be obtained. Conditions for appearance of these gravity waves are investigated. Optical methods were applied for water surface diagnostics.
A boundary element model for diffraction of water waves on varying water depth
Energy Technology Data Exchange (ETDEWEB)
Poulin, Sanne
1997-12-31
In this thesis a boundary element model for calculating diffraction of water waves on varying water depth is presented. The varying water depth is approximated with a perturbed constant depth in the mild-slope wave equation. By doing this, the domain integral which is a result of the varying depth is no longer a function of the unknown wave potential but only a function of position and the constant depth wave potential. The number of unknowns is the resulting system of equations is thus reduced significantly. The integration procedures in the model are tested very thoroughly and it is found that a combination of analytical integration in the singular region and standard numerical integration outside works very well. The gradient of the wave potential is evaluated successfully using a hypersingular integral equation. Deviations from the analytical solution are only found on the boundary or very close to, but these deviations have no significant influence on the accuracy of the solution. The domain integral is evaluated using the dual reciprocity method. The results are compared with a direct integration of the integral, and the accuracy is quite satisfactory. The problem with irregular frequencies is taken care of by the CBIEM (or CHIEF-method) together with a singular value decomposition technique. This method is simple to implement and works very well. The model is verified using Homma`s island as a test case. The test cases are limited to shallow water since the analytical solution is only valid in this region. Several depth ratios are examined, and it is found that the accuracy of the model increases with increasing wave period and decreasing depth ratio. Short waves, e.g. wind generated waves, can allow depth variations up to approximately 2 before the error exceeds 10%, while long waves can allow larger depth ratios. It is concluded that the perturbation idea is highly usable. A study of (partially) absorbing boundary conditions is also conducted. (EG)
Theoretical Model of Acoustic Wave Propagation in Shallow Water
Directory of Open Access Journals (Sweden)
Kozaczka Eugeniusz
2017-06-01
Full Text Available The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “deformed” by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom.
Experimental investigation of wave-driven pore-water pressure and wave attenuation in a sandy seabed
Directory of Open Access Journals (Sweden)
Jisheng Zhang
2016-06-01
Full Text Available Wave–seabed interaction has become a big concern of coastal researchers and engineers in the past decades as it may largely contribute to the seabed instability and failure of marine foundations. A series of laboratory experiments are carried out in a wave flume to study the wave-driven pore-water pressure in a sandy seabed and the attenuation of wave height. Waves propagating over a sandy seabed lead to oscillatory excess pore-water pressures within the porous seabed. Amplitude of pore-water pressure within the seabed decreases toward the bottom. A phase lag of pore-water pressure is clearly observed, and it contributes to net upward pressure related to seabed instability. Height of the incident wave is reduced as part of wave energy is dissipated by bottom friction, and a maximum attenuation of the incident wave height is up to 7.23% in the experiments. The influences of wave period and height of the incident wave on pore-water pressure and wave attenuation are also analyzed and discussed.
Numerical study of surface water waves generated by mass movement
Ghozlani, Belgacem; Hafsia, Zouhaier; Maalel, Khlifa
2013-10-01
In this paper waves generated by two-dimensional mass movement are simulated using a numerical model based on the full hydrodynamic coupling between rigid-body motion and ambient fluid flow. This approach has the capability to represent the dynamics of the moving rigid body, which avoids the need to prescribe the body velocity based on the data measurements. This model is implemented in the CFX code and uses the Reynolds average Navier-Stokes equations solver coupled to the recently developed immersed solid technique. The latter technique allows us to follow implicitly the motion of the solid block based on the rigid body solver. The volume-of-fluid method is used to track the free surface locations. The accuracy of the present model is firstly examined against the simple physical case of a freely falling rigid body into water reproducing Scott Russell's solitary waves. More complex and realistic simulations of aerial and submarine mass-movement, simulated by a rigid wedge sliding into water along a 45° slope, are then performed. Simulated results of the aerial mass movement show the complex flow patterns in terms of the velocity fields and free surface profiles. Results are in good agreement with the available experimental data. In addition, the physical processes associated with the generation of water wave by two-dimensional submarine mass-movement are explored. The effects of the initial submergence and specific gravity on the slide mass kinematics and maximum wave amplitude are investigated. The terminal velocity and initial acceleration of the slide mass are well predicted when compared to experimental results. It is found that the initial submergence did not have a significant effect on the initial acceleration of the slide block centre of mass. However, it depends nonlinearly\\vadjust{\
Structural Optimization of Triboelectric Nanogenerator for Harvesting Water Wave Energy.
Jiang, Tao; Zhang, Li Min; Chen, Xiangyu; Han, Chang Bao; Tang, Wei; Zhang, Chi; Xu, Liang; Wang, Zhong Lin
2015-12-22
Ocean waves are one of the most abundant energy sources on earth, but harvesting such energy is rather challenging due to various limitations of current technologies. Recently, networks formed by triboelectric nanogenerator (TENG) have been proposed as a promising technology for harvesting water wave energy. In this work, a basic unit for the TENG network was studied and optimized, which has a box structure composed of walls made of TENG composed of a wavy-structured Cu-Kapton-Cu film and two FEP thin films, with a metal ball enclosed inside. By combination of the theoretical calculations and experimental studies, the output performances of the TENG unit were investigated for various structural parameters, such as the size, mass, or number of the metal balls. From the viewpoint of theory, the output characteristics of TENG during its collision with the ball were numerically calculated by the finite element method and interpolation method, and there exists an optimum ball size or mass to reach maximized output power and electric energy. Moreover, the theoretical results were well verified by the experimental tests. The present work could provide guidance for structural optimization of wavy-structured TENGs for effectively harvesting water wave energy toward the dream of large-scale blue energy.
The fourth-generation Water Vapor Millimeter-Wave Spectrometer
Gomez, R. Michael; Nedoluha, Gerald E.; Neal, Helen L.; McDermid, I. Stuart
2012-02-01
For 20 years the Naval Research Laboratory has been making continuous water vapor profile measurements at 22.235 GHz with the Water Vapor Millimeter-Wave Spectrometer (WVMS) instruments, with the program expanding from one to three instruments in the first 6 years. Since the initial deployments there have been gradual improvements in the instrument design which have improved data quality and reduced maintenance requirements. Recent technological developments have made it possible to entirely redesign the instrument and improve not only the quality of the measurements but also the capability of the instrument. We present the fourth-generation instrument now operating at Table Mountain, California, which incorporates the most recent advances in microwave radiometry. This instrument represents the most significant extension of our measurement capability to date, enabling us to measure middle atmospheric water vapor from ˜26-80 km.
A nonlinear RDF model for waves propagating in shallow water
Institute of Scientific and Technical Information of China (English)
王厚杰; 杨作升; 李瑞杰; 张军
2001-01-01
In this paper, a composite explicit nonlinear dispersion relation is presented with reference to Stokes 2nd order dispersion relation and the empirical relation of Hedges. The explicit dispersion relation has such advantages that it can smoothly match the Stokes relation in deep and intermediate water and Hedgs’s relation in shallow water. As an explicit formula, it separates the nonlinear term from the linear dispersion relation. Therefore it is convenient to obtain the numerical solution of nonlinear dispersion relation. The present formula is combined with the modified mild-slope equation including nonlinear effect to make a Refraction-Diffraction (RDF) model for wave propagating in shallow water. This nonlinear model is verified over a complicated topography with two submerged elliptical shoals resting on a slope beach. The computation results compared with those obtained from linear model show that at present the nonlinear RDF model can predict the nonlinear characteristics and the combined refracti
Analysis of silt behavior induced by water waves
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Based on the weak non-elastic porous model, the expressions of pore pressure, effective stress and displacements of soil skeletal frame and pore water have been deduced for a finite depth seabed. The distributions of several physical parameters have been analyzed for three kinds of marine sediment, including pore pressure, effective stress, stress angle, displacement of skeletal frame and pore fluid, and the variations of elastic waves with wave period. According to the experimental results, the resonant phenomena in the silt bed and the mechanism underlying such events have been discussed. It is proposed that the existence of a stiff soil layer inside the silt bed is a necessary condition for resonance to occur, and the possible location of resonance can be forecasted.
Water wave communication in the genus Bombina (amphibia)
Seidel, B.; Yamashita, M.; Choi, I.-H.; Dittami, J.
2001-01-01
Amphibians were phylogenetically the first vertebrates to leave the aquatic environment and cope with terrestrial conditions including effects of gravity and substrate on movement and communication. Studies of extant primitive amphibians, which have conserved ancestral morphology and behavior, may help us to understand how gravitational adaptation from aquatic to terrestrial environments occurred. The anuran genus Bombina is a candidate for this type of investigation. In particular, a member of this genus, B. orientalis, is known for its low reaction threshold to minor changes of angular acceleration. We hypothesize that a heightened sensitivity to angular and mechanical accelerations evolved with wave communication. Comparisons of such behavior among B. variegata, B. bombina and B. orientalis may shed light on the evolution of reproductive systems based on water wave communication and relevant vestibular sensitivity. This may represent a transition to derived vocalization modes, which is seen in B. bombina to a certain degree.
The "shallow-waterness" of the wave climate in European coastal regions
Christensen, Kai Håkon; Carrasco, Ana; Bidlot, Jean-Raymond; Breivik, Øyvind
2016-01-01
In contrast to deep water waves, shallow water waves are influenced by bottom topography, which has consequences for the propagation of wave energy as well as for the energy and momentum exchange between the waves and the mean flow. The ERA-Interim reanalysis is used to assess the fraction of wave energy associated with shallow water waves in coastal regions in Europe. We show maps of the distribution of this fraction as well as time series statistics from 8 selected stations. There is a s...
Initial phenomenon of roll wave of shallow water on inclined channel
Arai, M.
2015-12-01
1. INTRODUCTION Intermittent surges of debris flows are observed in mountain regions. This type of flow is considered to be characterized by developing roll waves (surges) due to flow instabilities and by a weak sediment concentrations. For a understanding of initial phenomenon and fluctuation of the flow depth, wave equations and understanding characteristics of the solutions are needed. It is presented a wave equation and some solutions of roll waves based on shallow water momentum equation. These results show an improved understanding of the phenomena and wave equation of developing roll wave. 2. WAVE EQUATION AND SOME SOLUTIONS Considering momentam equation of shallow water on inclined channel and using reductive perturbation method, a wave equation which is a kind of KdV-Burgers equation was obtained. For on long wave velocity, some analitical solutions and numerical solutions ware obtained. Relationships of wave equation, it's solutions and phenomenon are discussed. 3. CONCLUSION A wave of minute disturbance on long wave velocity is governed by Burgers equation. For not fixed boundary condition and initial wave condition of not multiple wave number, an initial wave is deformed to a wave which wave number is one. The wave is caused a phase and the phenomena is shifted from Burgers equation to KdV-Burgers equation which has the characteristic of the solitary wave.
Performance of ERA-Interim wave data in the nearshore waters around India
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Naseef, T.M.
Bulk wave parameters, such as wave height and wave period, are required for engineering and environmental applications. In this study, measured wave data from six shallow-water locations in the data-sparse north Indian Ocean are used to assess...
Computation of nonlinear water waves with a high-order Boussinesq model
DEFF Research Database (Denmark)
Fuhrman, David R.; Madsen, Per A.; Bingham, Harry
2005-01-01
-crested waves in shallow/deep water, resulting in hexagonal/rectangular surface patterns; crescent waves, resulting from unstable perturbations of plane progressive waves; and highly-nonlinear wave-structure interactions. The emphasis is on physically demanding problems, and in eachcase qualitative and (when...
Wavefront modulation of water surface wave by a metasurface
Sun, Hai-Tao; Cheng, Ying; Wang, Jing-Shi; Liu, Xiao-Jun
2015-10-01
We design a planar metasurface to modulate the wavefront of a water surface wave (WSW) on a deep sub-wavelength scale. The metasurface is composed of an array of coiling-up-space units with specially designed parameters, and can take on the work of steering the wavefront when it is pierced into water. Like their acoustic counterparts, the modulation of WSW is ascribed to the gradient phase shift of the coiling-up-space units, which can be perfectly tuned by changing the coiling plate length and channel number inside the units. According to the generalized Snell’s law, negative refraction and ‘driven’ surface mode of WSW are also demonstrated at certain incidences. Specially, the transmitted WSW could be efficiently guided out by linking a symmetrically-corrugated channel in ‘driven’ surface mode. This work may have potential applications in water wave energy extraction and coastal protection. Project supported by the National Basic Research Program of China (Grant No. 2012CB921504), the National Natural Science Foundation of China (Grant Nos. 11474162, 11274171, 11274099, and 11204145), and the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant Nos. 20110091120040 and 20120091110001).
Diffusive Wave Approximation to the Shallow Water Equations: Computational Approach
Collier, Nathan
2011-05-14
We discuss the use of time adaptivity applied to the one dimensional diffusive wave approximation to the shallow water equations. A simple and computationally economical error estimator is discussed which enables time-step size adaptivity. This robust adaptive time discretization corrects the initial time step size to achieve a user specified bound on the discretization error and allows time step size variations of several orders of magnitude. In particular, in the one dimensional results presented in this work feature a change of four orders of magnitudes for the time step over the entire simulation.
Seismic Interface Waves in Coastal Waters: A Review
1980-11-15
water. In 1976 McLeroy and his co-workers [1861 again performed a very extensive real-world experiment in the Gulf of Mexico . Using a receiving array of...York, Academic Press, 1967. 4. SOMMERFELD, A. Uber die Ausbreitung der Wellen in der drahtlosen Telegraphie. Annalen der Physik, 28, 1909. 665-736. 5...Rayleigh waves on the confines of two solid elastic media. Doklady Akademii Nauk, SSSR, 33, 1947: 15-17. 30. KOPPE, H. Uber Rayleigh-Wellen an der
Frequency shift of the Bragg and Non-Bragg backscattering from periodic water wave
Wen, Biyang; Li, Ke
2016-08-01
Doppler effect is used to measure the relative speed of a moving target with respect to the radar, and is also used to interpret the frequency shift of the backscattering from the ocean wave according to the water-wave phase velocity. The widely known relationship between the Doppler shift and the water-wave phase velocity was deduced from the scattering measurements data collected from actual sea surface, and has not been verified under man-made conditions. Here we show that this ob- served frequency shift of the scattering data from the Bragg and Non-Bragg water wave is not the Doppler shift corresponding to the water-wave phase velocity as commonly believed, but is the water-wave frequency and its integral multiple frequency. The power spectrum of the backscatter from the periodic water wave consists of serials discrete peaks, which is equally spaced by water wave frequency. Only when the water-wave length is the integer multiples of the Bragg wave, and the radar range resolution is infinite, does the frequency shift of the backscattering mathematically equal the Doppler shift according to the water-wave phase velocity.
Conditional short-crested waves in shallow water and with superimposed current
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher
2002-01-01
For bottom-supported offshore structures like oil drilling rigs and oil production platforms, a deterministic design wave approach is often applied using a regular non-linear Stokes´ wave. Thereby, the procedure accounts for non-linear effects in the wave loading but the randomness of the ocean...... wave, given the value of the wave crest at a specific point in time or space. In the present paper a derivation of the expected linear short-crested wave riding on a uniform current is given. The analysis is based on the conventional shallow water Airy wave theory and the direction of the main wind...... direction can make any direction with the current. A consistent derivation of the wave spectrum taking into account current and finite water depth is used. The numerical results show a significant effect of the water depth, the directional spreading and the current on the conditional mean wave profile...
Conditional Short-crested second order waves in shallow water and with superimposed current
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher
2004-01-01
For bottom-supported offshore structures like oil drilling rigs and oil production platforms, a deterministic design wave approach is often applied using a regular non-linear Stokes' wave. Thereby, the procedure accounts for non-linear effects in the wave loading but the randomness of the ocean...... wave, given the value of the wave crest at a specific point in time or space. In the present paper a derivation of the expected second order short-crested wave riding on a uniform current is given. The analysis is based on the second order Sharma and Dean shallow water wave theory and the direction...... of the main wind direction can make any direction with the current. Numerical results showing the importance of the water depth, the directional spreading and the current on the conditional mean wave profile and the associated wave kinematics are presented. A discussion of the use of the conditional wave...
Hollow vortices, capillary water waves and double quadrature domains
Energy Technology Data Exchange (ETDEWEB)
Crowdy, Darren G [Department of Mathematics, Imperial College London, 180 Queen' s Gate, London SW7 2AZ (United Kingdom); Roenby, Johan, E-mail: d.crowdy@imperial.ac.uk, E-mail: johan.roenby@gmail.com [DHI, Agern Allé 5, 2970 Hørsholm (Denmark)
2014-06-01
Two new classes of analytical solutions for hollow vortex equilibria are presented. One class involves a central hollow vortex, comprising a constant pressure region having non-zero circulation, surrounded by an n-polygonal array of point vortices with n⩾2. The solutions generalize the non-rotating polygonal point vortex configurations of Morikawa and Swenson (1971 Phys. Fluids 14 1058–73) to the case where the point vortex at the centre of the polygon is replaced by a hollow vortex. The results of Morikawa and Swenson would suggest that all equilibria for n≠3 will be linearly unstable to point vortex mode instabilities. However even the n = 3 case turns out to be unstable to a recently discovered displacement instability deriving from a resonance between the natural modes of an isolated circular hollow vortex. A second class of analytical solutions for periodic water waves co-travelling with a submerged point vortex row is also described. The analysis gives rise to new theoretical connections with free surface Euler flows with surface tension and, in particular, with Crapper's classical solutions for capillary water waves. It is pointed out that the equilibrium fluid regions found here have a mathematical interpretation as an abstract class of planar domains known as double quadrature domains. (ss 1)
Conditional Short-crested second order waves in shallow water and with superimposed current
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher
2004-01-01
wave, given the value of the wave crest at a specific point in time or space. In the present paper a derivation of the expected second order short-crested wave riding on a uniform current is given. The analysis is based on the second order Sharma and Dean shallow water wave theory and the direction......For bottom-supported offshore structures like oil drilling rigs and oil production platforms, a deterministic design wave approach is often applied using a regular non-linear Stokes' wave. Thereby, the procedure accounts for non-linear effects in the wave loading but the randomness of the ocean...... waves is poorly represented, as the shape of the wave spectrum does not enter the wave kinematics. To overcome this problem and still keep the simplicity of a deterministic approach, Tromans, Anaturk and Hagemeijer (1991) suggested the use of a deterministic wave, defined as the expected linear Airy...
Conditional short-crested waves in shallow water and with superimposed current
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher
2002-01-01
For bottom-supported offshore structures like oil drilling rigs and oil production platforms, a deterministic design wave approach is often applied using a regular non-linear Stokes´ wave. Thereby, the procedure accounts for non-linear effects in the wave loading but the randomness of the ocean...... wave, given the value of the wave crest at a specific point in time or space. In the present paper a derivation of the expected linear short-crested wave riding on a uniform current is given. The analysis is based on the conventional shallow water Airy wave theory and the direction of the main wind...
Nonlinear unified equations for water waves propagating over uneven bottoms in the nearshore region
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Considering the continuous characteristics for water waves propagating over complex topography in the nearshore region, the unified nonlinear equations, based on the hypothesis for a typical uneven bottom, are presented by employing the Hamiltonian variational principle for water waves. It is verified that the equations include the following special cases: the extension of Airy's nonlinear shallow-water equations, the generalized mild-slope equation, the dispersion relation for the second-order Stokes waves and the higher order Boussinesq-type equations.
Zhou, Yong; Ni, Sidao; Chu, Risheng; Yao, Huajian
2016-08-01
Numerical solvers of wave equations have been widely used to simulate global seismic waves including PP waves for modelling 410/660 km discontinuity and Rayleigh waves for imaging crustal structure. In order to avoid extra computation cost due to ocean water effects, these numerical solvers usually adopt water column approximation, whose accuracy depends on frequency and needs to be investigated quantitatively. In this paper, we describe a unified representation of accurate and approximate forms of the equivalent water column boundary condition as well as the free boundary condition. Then we derive an analytical form of the PP-wave reflection coefficient with the unified boundary condition, and quantify the effects of water column approximation on amplitude and phase shift of the PP waves. We also study the effects of water column approximation on phase velocity dispersion of the fundamental mode Rayleigh wave with a propagation matrix method. We find that with the water column approximation: (1) The error of PP amplitude and phase shift is less than 5 per cent and 9° at periods greater than 25 s for most oceanic regions. But at periods of 15 s or less, PP is inaccurate up to 10 per cent in amplitude and a few seconds in time shift for deep oceans. (2) The error in Rayleigh wave phase velocity is less than 1 per cent at periods greater than 30 s in most oceanic regions, but the error is up to 2 per cent for deep oceans at periods of 20 s or less. This study confirms that the water column approximation is only accurate at long periods and it needs to be improved at shorter periods.
Parameterization of ocean wave-induced mixing processes for finite water depth
Institute of Scientific and Technical Information of China (English)
YANG Yongzeng; ZHAN Run; TENG Yong
2009-01-01
Three dimensional wave-induced mixing plays an important role in shallow water area. A quite direct approach through the Reynolds average upon characteristic length scale is proposed to parameterize the horizontal and vertical shallow water mixing. Comparison of finite depth case with infinite depth results indicates that the difference of the wave-induced mixing strength is evident. In the shallow water condition, the infinite water depth approximation overestimates the mixing strength in the lower layers. The nonzero horizontal wave-induced mixing presents anisotropic property near the shore. The Prandtl's mixing length theory underestimated the wave-induced mixing in the previous studies.
Millimeter Wave Scattering from Neutral and Charged Water Droplets
Heifetz, Alexander; Liao, Shaolin; Gopalsami, N Sami; Raptis, A C Paul
2010-01-01
We investigated 94GHz millimeter wave (MMW) scattering from neutral and charged water mist produced in the laboratory with an ultrasonic atomizer. Diffusion charging of the mist was accomplished with a negative ion generator (NIG). We observed increased forward and backscattering of MMW from charged mist, as compared to MMW scattering from an uncharged mist. In order to interpret the experimental results, we developed a model based on classical electrodynamics theory of scattering from a dielectric sphere with diffusion-deposited mobile surface charge. In this approach, scattering and extinction cross-sections are calculated for a charged Rayleigh particle with effective dielectric constant consisting of the volume dielectric function of the neutral sphere and surface dielectric function due to the oscillation of the surface charge in the presence of applied electric field. For small droplets with (radius smaller than 100nm), this model predicts increased MMW scattering from charged mist, which is qualitative...
Optical technique for measurement of random water wave surfaces
Sorrell, F. Y.; Withers, A. L.
1976-01-01
An optical system using the refraction of a vertical light ray has been developed for measuring the slope of random wind-generated water waves. The basic elements of the system are photovoltaic cells which are connected to individual amplifiers so that when the refracted light beam is incident on a cell, the output of the cell is amplified and then supplied as input to a comparator. The comparator then provides a specified voltage output, independent of the incident light intensity, as long as it is above a designated background value. The comparators are designed to give output voltages comparable with standard TTL. This arrangement provides a high signal from the cell when it experiences incident light, and a low signal when there is only background light, with the high and low signals at TTL voltage levels.
Non-perturbative String Theory from Water Waves
Energy Technology Data Exchange (ETDEWEB)
Iyer, Ramakrishnan; Johnson, Clifford V.; /Southern California U.; Pennington, Jeffrey S.; /SLAC
2012-06-14
We use a combination of a 't Hooft limit and numerical methods to find non-perturbative solutions of exactly solvable string theories, showing that perturbative solutions in different asymptotic regimes are connected by smooth interpolating functions. Our earlier perturbative work showed that a large class of minimal string theories arise as special limits of a Painleve IV hierarchy of string equations that can be derived by a similarity reduction of the dispersive water wave hierarchy of differential equations. The hierarchy of string equations contains new perturbative solutions, some of which were conjectured to be the type IIA and IIB string theories coupled to (4, 4k ? 2) superconformal minimal models of type (A, D). Our present paper shows that these new theories have smooth non-perturbative extensions. We also find evidence for putative new string theories that were not apparent in the perturbative analysis.
Ocean swell within the kinetic equation for water waves
Badulin, Sergei I
2016-01-01
Effects of wave-wave interactions on ocean swell are studied. Results of extensive simulations of swell evolution within the duration-limited setup for the kinetic Hasselmann equation at long times up to $10^6$ seconds are presented. Basic solutions of the theory of weak turbulence, the so-called Kolmogorov-Zakharov solutions, are shown to be relevant to the results of the simulations. Features of self-similarity of wave spectra are detailed and their impact on methods of ocean swell monitoring are discussed. Essential drop of wave energy (wave height) due to wave-wave interactions is found to be pronounced at initial stages of swell evolution (of order of 1000 km for typical parameters of the ocean swell). At longer times wave-wave interactions are responsible for a universal angular distribution of wave spectra in a wide range of initial conditions.
Directory of Open Access Journals (Sweden)
Pedro Beirão
2015-09-01
Full Text Available The energy that can be captured from the sea waves and converted into electricity should be seen as a contribution to decrease the excessive dependency and growing demand of fossil fuels. Devices suitable to harness this kind of renewable energy source and convert it into electricity—wave energy converters (WECs—are not yet commercially competitive. There are several types of WECs, with different designs and working principles. One possible classification is their distance to the shoreline and thus their depth. Near-shore devices are one of them since they are typically deployed at intermediate water depth (IWD. The selection of the WEC deployment site should be a balance between several parameters; water depth is one of them. Another way of classifying WECs is grouping them by their geometry, size and orientation. Considering a near-shore WEC belonging to the floating point category, this paper is focused on the numerical study about the differences arising in the power captured from the sea waves when the typical deep water (DW assumption is compared with the more realistic IWD consideration. Actually, the production of electricity will depend, among other issues, on the depth of the deployment site. The development of a dynamic model including specific equations for the usual DW assumption as well as for IWD is also described. Derived equations were used to build a time domain simulator (TDS. Numerical results were obtained by means of simulations performed using the TDS. The objective is to simulate the dynamic behavior of the WEC due to the action of sea waves and to characterize the wave power variations according with the depth of the deployment site.
Water wave scattering by an elastic thin vertical plate submerged in finite depth water
Chakraborty, Rumpa; Mandal, B. N.
2013-12-01
The problem of water wave scattering by a thin vertical elastic plate submerged in uniform finite depth water is investigated here. The boundary condition on the elastic plate is derived from the Bernoulli-Euler equation of motion satisfied by the plate. Using the Green's function technique, from this boundary condition, the normal velocity of the plate is expressed in terms of the difference between the velocity potentials (unknown) across the plate. The two ends of the plate are either clamped or free. The reflection and transmission coefficients are obtained in terms of the integrals' involving combinations of the unknown velocity potential on the two sides of the plate, which satisfy three simultaneous integral equations and are solved numerically. These coefficients are computed numerically for various values of different parameters and depicted graphically against the wave number in a number of figures.
Waves in the nearshore waters of northern Arabian Sea during the summer monsoon
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Singh, J.; Pednekar, P.S.; Gowthaman, R.
% of the wave height at the measurement location is due to the swells arriving from the south-west and the remaining is due to the seas from south-west to north-west. Wave age of the measured data indicates that the waves in the nearshore waters of northern...
A Three Dimensional Sea Facility for Deep and Shallow Water Waves
DEFF Research Database (Denmark)
Burcharth, Hans F.; Nielsen, Søren R.K.; Schaarup-Jensen, Kjeld
1986-01-01
The paper describes a low-cost wave tank for the testing of structures in short crested seas and current. The paddle system is of the snake type and used for the generation of both deep and shallow water waves. The quality of the waves and scale problems related to small scale tests are discussed...
Generation and Active Absorption of 2- and 3-Dimensional Linear Water Waves in Physical Models
DEFF Research Database (Denmark)
Christensen, Morten
Methods for mechanical generation of 2-dimensional (2-D) and 3-dimensional (3-D) linear water waves in physical models are presented. The results of a series of laboratory 3-D wave generation tests are presented and discussed. The tests preformed involve reproduction of wave fields characterised...
Water Surface Wave in a Trough with Periodical Topographical Bottom under Vertical Vibration
Institute of Scientific and Technical Information of China (English)
HU Yi; MIAO Guo-Qing; WEI Rong-Jue
2009-01-01
We investigate the water surface waves in a vertically vibrated long rectangular trough with several identical Plexiglas rectangles lined periodically on the bottom. The band structure is computed theoretically by the method of transfer matrix. Some interesting phenomena, such as the localized wave, especially the solitary-like wave inside the band gap, are observed in the experiments.
Solitary and cnoidal wave scattering by a submerged horizontal plate in shallow water
Hayatdavoodi, Masoud; Ertekin, R. Cengiz; Valentine, Benjamin D.
2017-06-01
Solitary and cnoidal wave transformation over a submerged, fixed, horizontal rigid plate is studied by use of the nonlinear, shallow-water Level I Green-Naghdi (GN) equations. Reflection and transmission coefficients are defined for cnoidal and solitary waves to quantify the nonlinear wave scattering. Results of the GN equations are compared with the laboratory experiments and other theoretical solutions for linear and nonlinear waves in intermediate and deep waters. The GN equations are then used to study the nonlinear wave scattering by a plate in shallow water. It is shown that in deep and intermediate depths, the wave-scattering varies nonlinearly by both the wavelength over the plate length ratio, and the submergence depth. In shallow water, however, and for long-waves, only the submergence depth appear to play a significant role on wave scattering. It is possible to define the plate submergence depth and length such that certain wave conditions are optimized above, below, or downwave of the plate for different applications. A submerged plate in shallow water can be used as a means to attenuate energy, such as in wave breakers, or used for energy focusing, and in wave energy devices.
Spatial and temporal compact equations for water waves
Dyachenko, Alexander; Kachulin, Dmitriy; Zakharov, Vladimir
2016-04-01
A one-dimensional potential flow of an ideal incompressible fluid with a free surface in a gravity field is the Hamiltonian system with the Hamiltonian: H = 1/2intdxint-∞^η |nablaφ|^2dz + g/2ont η^2dxŗφ(x,z,t) - is the potential of the fluid, g - gravity acceleration, η(x,t) - surface profile Hamiltonian can be expanded as infinite series of steepness: {Ham4} H &=& H2 + H3 + H4 + dotsŗH2 &=& 1/2int (gη2 + ψ hat kψ) dx, ŗH3 &=& -1/2int \\{(hat kψ)2 -(ψ_x)^2}η dx,ŗH4 &=&1/2int {ψxx η2 hat kψ + ψ hat k(η hat k(η hat kψ))} dx. where hat k corresponds to the multiplication by |k| in Fourier space, ψ(x,t)= φ(x,η(x,t),t). This truncated Hamiltonian is enough for gravity waves of moderate amplitudes and can not be reduced. We have derived self-consistent compact equations, both spatial and temporal, for unidirectional water waves. Equations are written for normal complex variable c(x,t), not for ψ(x,t) and η(x,t). Hamiltonian for temporal compact equation can be written in x-space as following: {SPACE_C} H = intc^*hat V c dx + 1/2int [ i/4(c2 partial/partial x {c^*}2 - {c^*}2 partial/partial x c2)- |c|2 hat K(|c|^2) ]dx Here operator hat V in K-space is so that Vk = ω_k/k. If along with this to introduce Gardner-Zakharov-Faddeev bracket (for the analytic in the upper half-plane function) {GZF} partial^+x Leftrightarrow ikθk Hamiltonian for spatial compact equation is the following: {H24} &&H=1/gint1/ω|cω|2 dω +ŗ&+&1/2g^3int|c|^2(ddot c^*c + ddot c c^*)dt + i/g^2int |c|^2hatω(dot c c* - cdot c^*)dt. equation of motion is: {t-space} &&partial /partial xc +i/g partial^2/partial t^2c =ŗ&=& 1/2g^3partial^3/partial t3 [ partial^2/partial t^2(|c|^2c) +2 |c|^2ddot c +ddot c^*c2 ]+ŗ&+&i/g3 partial^3/partial t3 [ partial /partial t( chatω |c|^2) + dot c hatω |c|2 + c hatω(dot c c* - cdot c^*) ]. It solves the spatial Cauchy problem for surface gravity wave on the deep water. Main features of the equations are: Equations are written for
Evolution of wave and tide over vegetation region in nearshore waters
Zhang, Mingliang; Zhang, Hongxing; Zhao, Kaibin; Tang, Jun; Qin, Huifa
2017-08-01
Coastal wetlands are an important ecosystem in nearshore regions, where complex flow characteristics occur because of the interactions among tides, waves, and plants, especially in the discontinuous flow of the intertidal zone. In order to simulate the wave and wave-induced current in coastal waters, in this study, an explicit depth-averaged hydrodynamic (HD) model has been dynamically coupled with a wave spectral model (CMS-Wave) by sharing the tide and wave data. The hydrodynamic model is based on the finite volume method; the intercell flux is computed using the Harten-Lax-van Leer (HLL) approximate Riemann solver for computing the dry-to-wet interface; the drag force of vegetation is modeled as the sink terms in the momentum equations. An empirical wave energy dissipation term with plant effect has been derived from the wave action balance equation to account for the resistance induced by aquatic vegetation in the CMS-Wave model. The results of the coupling model have been verified using the measured data for the case with wave-tide-vegetation interactions. The results show that the wave height decreases significantly along the wave propagation direction in the presence of vegetation. In the rip channel system, the oblique waves drive a meandering longshore current; it moves from left to right past the cusps with oscillations. In the vegetated region, the wave height is greatly attenuated due to the presence of vegetation, and the radiation stresses are noticeably changed as compared to the region without vegetation. Further, vegetation can affect the spatial distribution of mean velocity in a rip channel system. In the co-exiting environment of tides, waves, and vegetation, the locations of wave breaking and wave-induced radiation stress also vary with the water level of flooding or ebb tide in wetland water, which can also affect the development and evolution of wave-induced current.
Kim, Byoung-Nam; Lee, Kang Il; Yoon, Suk Wang
2007-04-01
Experimental observations of the subharmonic and ultraharmonic acoustic waves in water-saturated sandy sediment are reported in this paper. Acoustic pressures of both nonlinear acoustic waves strongly depend on the driving acoustic pressure at a transducer. The first ultraharmonic wave reaches a saturation value as the driving acoustic pressure increases. The acoustic pressure levels of both nonlinear acoustic waves exhibit some fluctuations in comparison with that of the primary acoustic wave as the receiving distance of hydrophone increases in sediment. The subharmonic and the ultraharmonic phenomena in this study show close resemblance to those produced in bubbly water.
On the feasibility of the use of wind SAR to downscale waves on shallow water
Gutiérrez, O. Q.; Filipponi, F.; Taramelli, A.; Valentini, E.; Camus, P.; Méndez, F. J.
2016-01-01
In recent years, wave reanalyses have become popular as a powerful source of information for wave climate research and engineering applications. These wave reanalyses provide continuous time series of offshore wave parameters; nevertheless, in coastal areas or shallow water, waves are poorly described because spatial resolution is not detailed. By means of wave downscaling, it is possible to increase spatial resolution in high temporal coverage simulations, using forcing from wind and offshore wave databases. Meanwhile, the reanalysis wave databases are enough to describe the wave climate at the limit of simulations; wind reanalyses at an adequate spatial resolution to describe the wind structure near the coast are not frequently available. Remote sensing synthetic aperture radar (SAR) has the ability to detect sea surface signatures and estimate wind fields at high resolution (up to 300 m) and high frequency. In this work a wave downscaling is done on the northern Adriatic Sea, using a hybrid methodology and global wave and wind reanalysis as forcing. The wave fields produced were compared to wave fields produced with SAR winds that represent the two dominant wind regimes in the area: the bora (ENE direction) and sirocco (SE direction). Results show a good correlation between the waves forced with reanalysis wind and SAR wind. In addition, a validation of reanalysis is shown. This research demonstrates how Earth observation products, such as SAR wind fields, can be successfully up-taken into oceanographic modeling, producing similar downscaled wave fields when compared to waves forced with reanalysis wind.
Design guidelines of triboelectric nanogenerator for water wave energy harvesters
Ahmed, Abdelsalam; Hassan, Islam; Jiang, Tao; Youssef, Khalid; Liu, Lian; Hedaya, Mohammad; Abu Yazid, Taher; Zu, Jean; Wang, Zhong Lin
2017-05-01
Ocean waves are one of the cleanest and most abundant energy sources on earth, and wave energy has the potential for future power generation. Triboelectric nanogenerator (TENG) technology has recently been proposed as a promising technology to harvest wave energy. In this paper, a theoretical study is performed on a duck-shaped TENG wave harvester recently introduced in our work. To enhance the design of the duck-shaped TENG wave harvester, the mechanical and electrical characteristics of the harvester’s overall structure, as well as its inner configuration, are analyzed, respectively, under different wave conditions, to optimize parameters such as duck radius and mass. Furthermore, a comprehensive hybrid 3D model is introduced to quantify the performance of the TENG wave harvester. Finally, the influence of different TENG parameters is validated by comparing the performance of several existing TENG wave harvesters. This study can be applied as a guideline for enhancing the performance of TENG wave energy harvesters.
Design guidelines of triboelectric nanogenerator for water wave energy harvesters
Ahmed, Abdelsalam
2017-04-11
Ocean waves are one of the cleanest and most abundant energy sources on earth, and wave energy has the potential for future power generation. Triboelectric nanogenerator (TENG) technology has recently been proposed as a promising technology to harvest wave energy. In this paper, a theoretical study is performed on a duck-shaped TENG wave harvester recently introduced in our work. To enhance the design of the duck-shaped TENG wave harvester, the mechanical and electrical characteristics of the harvester\\'s overall structure, as well as its inner configuration, are analyzed, respectively, under different wave conditions, to optimize parameters such as duck radius and mass. Furthermore, a comprehensive hybrid 3D model is introduced to quantify the performance of the TENG wave harvester. Finally, the influence of different TENG parameters is validated by comparing the performance of several existing TENG wave harvesters. This study can be applied as a guideline for enhancing the performance of TENG wave energy harvesters.
Wave Damping over a Perforated Plate with Water Chambers
Institute of Scientific and Technical Information of China (English)
ZHU Shutang
2006-01-01
The movement of waves propagating over a horizontally submerged perforated plate with waterfilled chambers bellow the plate was investigated by using linear potential theory. The analytical solution was compared with laboratory experiments on wave blocking. The analysis of the wave energy dissipation on the perforated bottom surface shows that the effects of the perforated plate on thewave motion depend mainly on the plate porosity, the wave height, and the wave period. The wave number is a complex number when the wave energy dissipation on the perforated plate is considered. The real part of the wave number refers to the spatial periodicity while the imaginary part represents the damping modulus. The characteristics of the wave motion were explored for several possible conditions.
2004-01-01
A new strategy for active control in heavy-lift offshore crane operations is suggested, by introducing a new concept referred to as wave synchronization. Wave synchronization reduces the hydrodynamic forces by minimization of variations in the relative vertical velocity between payload and water using a wave amplitude measurement. Wave synchronization is combined with conventional active heave compensation to obtain accurate control. Experimental results using a scale model of a semi-submerge...
The Fractional Power Law of Wind Wave Growth in Deep Water for Short Fetch
Institute of Scientific and Technical Information of China (English)
GUAN Changlong; SUN Qun; Philippe Fraunie
2002-01-01
Combining the 3/2 power law proposed by Toba with the significant wave energy balance equation for windwaves, wave growth in deep water for short fetch is investigated. It is found that the variations of wave height and periodwith fetch have the form of power function with fractional exponents 3/8 and 1/4 respectively. Using these exponents in thepower functions and through data fitting, the concise wind wave growth relations for short fetch are obtained.
Simulation Analysis of Wave Effect on Exceeding Water Gesture and Load of Submarine Launched Missile
Directory of Open Access Journals (Sweden)
Ke Zhao
2014-02-01
Full Text Available In this study, we have a research on wave action on the submarine launched missile water trajectory and gesture angles during the process between launch and exit from water. Infinite water depth plane wave was used as the wave model, mathematics models of missile exceeding water under different wave conditions were established based on ideal potential flow theory. The flow field velocity potential was obtained by solving the Laplace equation, thus can obtain missile surface pressure. Considering free surface effects, simple Green’s function was introduced to solve boundary value problems. Three-dimensional Fortran program and finite software ABAQUS were combined to complete the fluid-structure interaction simulation. The rules that wave level and phases effects on submarine-launched missile were finally obtained, which shows wave affect cannot be neglected. Simulation methods and results of this study have a certain reference value for the submarine-launched missile launching.
Exact Periodic Solitary Solutions to the Shallow Water Wave Equation
Institute of Scientific and Technical Information of China (English)
LI Dong-Long; ZHAO Jun-Xiao
2009-01-01
Exact solutions to the shallow wave equation are studied based on the idea of the extended homoclinic test and bilinear method. Some explicit solutions, such as the one soliton solution, the doubly-periodic wave solution and the periodic solitary wave solutions, are obtained. In addition, the properties of the solutions are investigated.
Numerical Simulation of Water Mitigation Effects on Shock Wave with SPH Method
Institute of Scientific and Technical Information of China (English)
MAO Yiming; FANG Qin; ZHANG Yadong; GAO Zhenru
2008-01-01
The water mitigation effect on the propagation of shock wave was investigated numerically.The traditionaf smoothed particle hydrodynamics(SPH)method was modified based on Riemann solution.The comparison of numerical results with the analytical solution indicated that the modified SPH method has more advantages than the traditional SPH method.Using the modified SPH algorithm.a series of one-dimensional planar wave propagation problems were investigated,focusing on the influence of the air-gap between the high-pressure air and water and the thickness of water.The humerical results showed that water mitigation effect is significant.Up to 60%shock wave pressure reduction could be achieved with the existence of water.and the shape of shock wave was also changed greatly.It is seemly that fhe small air-gap between the high-pressure air and water has more influence on water mitigation effect.
Intertidal water column meiofauna in relation to wave intensity on an exposed beach
Directory of Open Access Journals (Sweden)
J. Germán Rodríguez
2004-04-01
Full Text Available Since the 1970s, various studies have shown that some meiofaunal taxa frequently occur in the water column. Water currents or any process that disturbs the sediments are possible factors that can facilitate the passive entry of meiofauna in the water column. Wave action has been predicted as one of these factors (Armonies, 1994, suggesting a correlation between the number of eroded specimens and wave intensity should exist. As a test of this prediction, replicated samples were taken in the water column, swash sediment and back-swash water in an exposed beach (Island of Sylt, northern Wadden Sea. Wave height and period were measured to characterise the energy regime. Samplings were carried out over a nine day period in August 2000, at diurnal mid-tide time. Wave height and period varied significantly among collections. Densities of nematodes, harpacticoids, nauplii, platyhelminthes, ostracods and bivalve larvae in the water column, swash sediment and back-swash water varied significantly among collections. Nevertheless, no significant correlation was found between water column density and wave characteristics. Density of meiofauna in the water column was not correlated with density in the sediment or in back-swash water. Therefore wave intensity did not explain the variability of meiofaunal densities present in the water column.
Ocean swell within the kinetic equation for water waves
Badulin, Sergei I.; Zakharov, Vladimir E.
2017-06-01
Results of extensive simulations of swell evolution within the duration-limited setup for the kinetic Hasselmann equation for long durations of up to 2 × 106 s are presented. Basic solutions of the theory of weak turbulence, the so-called Kolmogorov-Zakharov solutions, are shown to be relevant to the results of the simulations. Features of self-similarity of wave spectra are detailed and their impact on methods of ocean swell monitoring is discussed. Essential drop in wave energy (wave height) due to wave-wave interactions is found at the initial stages of swell evolution (on the order of 1000 km for typical parameters of the ocean swell). At longer times, wave-wave interactions are responsible for a universal angular distribution of wave spectra in a wide range of initial conditions. Weak power-law attenuation of swell within the Hasselmann equation is not consistent with results of ocean swell tracking from satellite altimetry and SAR (synthetic aperture radar) data. At the same time, the relatively fast weakening of wave-wave interactions makes the swell evolution sensitive to other effects. In particular, as shown, coupling with locally generated wind waves can force the swell to grow in relatively light winds.
A theoretical remark about waves on a static water surface beneath a layer of moving air
Kida, T.; Hayashi, R.; Yasutomi, Z.
1990-12-01
Grundy and Tuck (1987) treat the problem of large-amplitude waves on an air-water interface where the air is a steady nonuniform flow and the water is stationary. Both periodic nonlinear Stokes-like waves far downstream and a configuration of the water surface from the edge region of a hovercraft were computed. However, there is no work that treats the existence of such Stokes-like waves theoretically. The present work aims to prove the existence of such solutions in the case where the cushion pressure is low, that is, the depression at the upstream stagnation point from the mean water level is small.
AN INTEGRAL EQUATION DESCRIBING RIDING WAVES IN SHALLOW WATER OF FINITE DEPTH
Institute of Scientific and Technical Information of China (English)
An Shu-ping; Le Jia-chun; Dai Shi-qiang
2003-01-01
An integral equation describing riding waves, i.e., small-scale perturbation waves superposed on unperturbed surface waves, in shallow water of finite depth was studied via explicit Hamiltonian formulation, and the water was regarded as ideal incompressible fluid of uniform density. The kinetic energy, density of the perturbed fluid motion was formulated with Hamiltonian canonical variables[1], elevation of the free surface and the velocity potential at the free surface. Then the variables were expanded to the first order at the free surface of unperturbed waves. An integal equation for velocity potential of perturbed waves on the unperturbed free surface was derived by conformal mapping and the Fourier transformation. The integral equation could replace the Hamiltonian canonical equations which are difficult to solve. An explicit expression of Lagrangian density function could be obtained by solving the integral equation. The method used in this paper provides a new path to study the Hamiltonian formulation of riding waves and wave interaction problems.
Reduced order prediction of rare events in unidirectional nonlinear water waves
Cousins, Will
2015-01-01
We consider the problem of short-term prediction of rare, extreme water waves in unidirectional fields, a critical topic for ocean structures and naval operations. One possible mechanism for the occurrence of such rare, unusually-intense waves is nonlinear wave focusing. Recent results have demonstrated that random localizations of energy, induced by the dispersive mixing of different harmonics, can grow significantly due to localized nonlinear focusing. Here we show how the interplay between i) statistical properties captured through linear information such as the waves power spectrum and ii) nonlinear dynamical properties of focusing localized wave groups defines a critical length scale associated with the formation of extreme events. The energy that is locally concentrated over this length scale acts as the "trigger" of nonlinear focusing for wave groups and the formation of subsequent rare events. We use this property to develop inexpensive, short-term predictors of large water waves. Specifically, we sho...
High-order Boussinesq-type modelling of nonlinear wave phenomena in deep and shallow water
DEFF Research Database (Denmark)
Madsen, Per A.; Fuhrman, David R.
2010-01-01
In this work, we start with a review of the development of Boussinesq theory for water waves covering the period from 1872 to date. Previous reviews have been given by Dingemans,1 Kirby,2,3 and Madsen & Schäffer.4 Next, we present our most recent high-order Boussinesq-type formulation valid...... for fully nonlinear and highly dispersive waves traveling over a rapidly varying bathymetry. Finally, we cover applications of this Boussinesq model, and we study a number of nonlinear wave phenomena in deep and shallow water. These include (1) Kinematics in highly nonlinear progressive deep-water waves; (2......) Kinematics in progressive solitary waves; (3) Reflection of solitary waves from a vertical wall; (4) Reflection and diffraction around a vertical plate; (5) Quartet and quintet interactions and class I and II instabilities; (6) Extreme events from focused directionally spread waveelds; (7) Bragg scattering...
A composite numerical model for wave diffraction in a harbor with varying water depth
Institute of Scientific and Technical Information of China (English)
ZHAO Ming; TENG Bin
2004-01-01
A composite numerical model is presented for computing the wave field in a harbor. The mild slope equation is discretized by a finite element method in the domain concerned. Out of the computational domain, the water depth is assumed to be constant. The boundary element method is applied to the outer boundary for dealing with the infinite boundary condition. Because the model satisfies strictly the infinite boundary condition, more accurate results can be obtained. The model is firstly applied to compute the wave diffraction in a narrow rectangular bay and the wave diffraction from a porous cylinder. The numerical results are compared with the analytical solution, experimental data and other numerical results. Good agreements are obtained. Then the model is applied to computing the wave diffraction in a square harbor with varying water depth. The effects of the water depth in the harbor and the incoming wave direction on the wave height distribution are discussed.
High-order Boussinesq-type modelling of nonlinear wave phenomena in deep and shallow water
DEFF Research Database (Denmark)
Madsen, Per A.; Fuhrman, David R.
2010-01-01
In this work, we start with a review of the development of Boussinesq theory for water waves covering the period from 1872 to date. Previous reviews have been given by Dingemans,1 Kirby,2,3 and Madsen & Schäffer.4 Next, we present our most recent high-order Boussinesq-type formulation valid...... for fully nonlinear and highly dispersive waves traveling over a rapidly varying bathymetry. Finally, we cover applications of this Boussinesq model, and we study a number of nonlinear wave phenomena in deep and shallow water. These include (1) Kinematics in highly nonlinear progressive deep-water waves; (2......) Kinematics in progressive solitary waves; (3) Reflection of solitary waves from a vertical wall; (4) Reflection and diffraction around a vertical plate; (5) Quartet and quintet interactions and class I and II instabilities; (6) Extreme events from focused directionally spread waveelds; (7) Bragg scattering...
Modeling wind waves from deep to shallow waters in Lake Michigan using unstructured SWAN
Mao, Miaohua; van der Westhuysen, André J.; Xia, Meng; Schwab, David J.; Chawla, Arun
2016-06-01
Accurate wind-wave simulations are vital for evaluating the impact of waves on coastal dynamics, especially when wave observations are sparse. It has been demonstrated that structured-grid models have the ability to capture the wave dynamics of large-scale offshore domains, and the recent emergence of unstructured meshes provides an opportunity to better simulate shallow-water waves by resolving the complex geometry along islands and coastlines. For this study, wind waves in Lake Michigan were simulated using the unstructured-grid version of Simulating Waves Nearshore (un-SWAN) model with various types of wind forcing, and the model was calibrated using in situ wave observations. Sensitivity experiments were conducted to investigate the key factors that impact wave growth and dissipation processes. In particular, we considered (1) three wind field sources, (2) three formulations for wind input and whitecapping, (3) alternative formulations and coefficients for depth-induced breaking, and (4) various mesh types. We find that un-SWAN driven by Global Environmental Multiscale (GEM) wind data reproduces significant wave heights reasonably well using previously proposed formulations for wind input, recalibrated whitecapping parameters, and alternative formulations for depth-induced breaking. The results indicate that using GEM wind field data as input captures large waves in the midlake most accurately, while using the Natural Neighbor Method wind field reproduces shallow-water waves more accurately. Wind input affects the simulated wave evolution across the whole lake, whereas whitecapping primarily affects wave dynamics in deep water. In shallow water, the process of depth-induced breaking is dominant and highly dependent upon breaker indices and mesh types.
Energy Technology Data Exchange (ETDEWEB)
Choi, W.; Camassa, R.
1998-12-31
The authors derive model equations that govern the evolution of internal gravity waves at the interface of two immiscible fluids. These models follow from the original Euler equations under the sole assumption that the waves are long compared to the undisturbed thickness of one of the fluid layers. No smallness assumption on the wave amplitude is made. Here the shallow water configuration is first considered, whereby the waves are taken to be long with respect to the total undisturbed thickness of the fluids. In part 2, the authors derive models for the configuration in which one of the two fluids has a thickness much larger than the wavelength. The fully nonlinear models contain the Korteweg-de Vries (KdV) equation and the intermediate-long-wave (ILW) equation, for shallow and deep water configurations respectively, as special cases in the limit of weak nonlinearity and unidirectional wave propagation. In particular, for a solitary wave of given amplitude, the characteristic wavelength is larger and the wave speed smaller than their counterparts for solitary wave solutions of the weakly nonlinear equations. These features are compared and found in overall good agreement with available experimental data for solitary waves of large amplitude in two-fluid systems.
Analysis of Mixing of Pollutants in Water Waves and Currents
Institute of Scientific and Technical Information of China (English)
YUAN Li-rong; SHEN Yong-ming; TANG Jun
2007-01-01
A vertical two-dimensional turbulence numerical model for the interaction of waves and currents is developed in the paper based on the nonlinear two-equation k-ε model with the VOF method.The one-dimensional equivalent advection velocity and equivalent mixing coefficient are defined and the solving process is introduced: The pollutant concentration field,generated by an instant source in waves and currents,is calculated with the model,and then the equivalent advection velocity and equivalent mixing coefficient are obtained by calculating the time derivative of the mean and variance of pollutant concentration probability distribution.The effects of wave period and wave height on the equivalent mixing coefficient for waves and wave-currents are also investigated.
THEORY?OF?WATER?WAVES?IN?AN?ELASTIC?VESSEL
Institute of Scientific and Technical Information of China (English)
D.Y.Hsieh
2000-01-01
Recent experiments related to the Dragon Wash phenomena showed that axisymmetric capillary waves appear first from excitation, and circumferential apillary waves appear after increase of the excitation strength. Based on this new finding, a theory of parametric resonance is developed in detail to explain the onset of the prominent circumferential capillary waves. Numerical computation is also carried out and the results agree generally with the experiments. Analysis and numerical computation are also presented to explain the generation of axisymmetric low-frequency gravity waves by the high-frequency external excitation.
Propagation Dynamics of Nonspreading Cosine-Gauss Water-Wave Pulses.
Fu, Shenhe; Tsur, Yuval; Zhou, Jianying; Shemer, Lev; Arie, Ady
2015-12-18
Linear gravity water waves are highly dispersive; therefore, the spreading of initially short wave trains characterizes water surface waves, and is a universal property of a dispersive medium. Only if there is sufficient nonlinearity does this envelope admit solitary solutions which do not spread and remain in fixed forms. Here, in contrast to the nonlinear localized wave packets, we present both theoretically and experimentally a new type of linearly nondispersive water wave, having a cosine-Gauss envelope, as well as its higher-order Hermite cosine-Gauss variations. We show that these waves preserve their width despite the inherent dispersion while propagating in an 18-m wave tank, accompanied by a slowly varying carrier-envelope phase. These wave packets exhibit self-healing; i.e., they are restored after bypassing an obstacle. We further demonstrate that these nondispersive waves are robust to weakly nonlinear perturbations. In the strong nonlinear regime, symmetry breaking of these waves is observed, but their cosine-Gauss shapes are still approximately preserved during propagation.
Note on wavefront dislocation in surface water waves
Karjanto, Natanael; Groesen, van E.
2007-01-01
At singular points of a wave field, where the amplitude vanishes, the phase may become singular and wavefront dislocation may occur. In this Letter we investigate for wave fields in one spatial dimension the appearance of these essentially linear phenomena. We introduce the Chu–Mei quotient as it is
Efficient computation of steady, 3D water-wave patterns
Lewis, M.R.; Koren, B.
2003-01-01
Numerical methods for the computation of stationary free surfaces is the subject of much current research in computational engineering. The present report is directed towards free surfaces in maritime engineering. Of interest here are the long steady waves generated by ships, the gravity waves. In t
Kinematics and Dynamics of a Tensegrity-Based Water Wave Energy Harvester
Directory of Open Access Journals (Sweden)
Min Lin
2016-01-01
Full Text Available A tensegrity-based water wave energy harvester is proposed. The direct and inverse kinematic problems are investigated by using a geometric method. Afterwards, the singularities and workspaces are discussed. Then, the Lagrangian method was used to develop the dynamic model considering the interaction between the harvester and water waves. The results indicate that the proposed harvester allows harvesting 13.59% more energy than a conventional heaving system. Therefore, tensegrity systems can be viewed as one alternative solution to conventional water wave energy harvesting systems.
Numerical Modeling of Water Wave Interaction with A Soft Mud Bed
Institute of Scientific and Technical Information of China (English)
齐鹏; 王石青; 侯一筠
2004-01-01
A vertical 2-D numerical model is presented for simulating the interaction between water waves and a soft mud bed.Taking into account nonlinear rheology, a semi-empirical rheological model is applied to this water-mud model, reflecting the combined viseo-elasto-plastic properties of soft mud under such oscillatory external forces as water waves. In order to increase the resolution of the flow in the neighborhood of both sides of the inter-surface, a logarithmic grid in the vertical direction is employed for numerical treatment. Model verifications are given through comparisons between the calculated and the measured mud mass transport velocities as well as wave height changes.
Investigation of Surface Waves in Deep and Shallow Water using Coherent Radars at Grazing Incidence
Buckley, M.; Horstmann, J.; Carrasco, R.; Seemann, J.; Stresser, M.
2016-02-01
Coherent microwave radars operating at X-band near grazing incidence are utilized to measure the backscatter intensity and Doppler velocity from the small-scale surface roughness of the ocean. The radar backscatter is dependent on the wind and strongly modulated by the surface waves and therefore enables to retrieve the surface wind as well as surface waves. The radar measured Doppler velocities are also modulated by contributions from the wind, current and waves and allow getting additional information on these parameters. In addition coherent marine radars allow to observe breaking waves, which lead to a increase in radar backscatter as well as a strong change of the Doppler speed.Within this presentation we will introduce and validate new methods to measure spectral wave properties such as wave directions, periods and significant wave height from coherent marine radars. The methods have been applied in deep and shallow water and validated to measurements of directional wave riders as well as an Acoustic Wave and Current Profiler. These comparisons show an overall excellent performance of coherent radars for the retrieval of spectral wave properties (e.g. Hs rms of 0.2 m). Furthermore, new methodologies will be presented that enable to observe and quantify wave breaking in deep water as well as in the littoral zone. The above mentioned methods have been applied to investigate the influence of Offshore Wind Farms (OWF) on the wave field with respect to the spectral properties as well as the amount of wave breaking. We will present the results obtained during a cruise in May 2015 within and around the OWF Dantysk in the German Bight of the North Sea, which consist of eighty 3.5 MW wind turbines. In addition we will present our initial results on the investigation of wave dissipation in the littoral zone at the coast of the island Sylt using marine radars, pressure gauges as well as directional wave riders.
FREQUENCY LOCK—IN PHENOMENON OF FLAPPING MOTION WITH SURFACE WATER WAVE
Institute of Scientific and Technical Information of China (English)
HsuChintsau; KuangJun; SunJianhong
2002-01-01
To study the effect of a progressive surface wave on the flapping motion of a vertical turbulent plane jet in shallow water,the laser visualizations and measurements were carried out in a water tank.The images of visualization by laser-induced fluorescence(LIF)technique show that the jet flapping motion occurs in the wave environ-ment.Using the wave height gauge and laser Doppler velocimetry(LDV) ,experimental results show that the jet flapping motions indeed lock-in to the wave oscillations if the wave frequency is close to but lower than the nature frequency of jet flapping motion.The phenomenon does not occur when the wave frequency is above the nature frequency of jet flapping motion.
Wave energy level and geographic setting correlate with Florida beach water quality.
Feng, Zhixuan; Reniers, Ad; Haus, Brian K; Solo-Gabriele, Helena M; Kelly, Elizabeth A
2016-03-15
Many recreational beaches suffer from elevated levels of microorganisms, resulting in beach advisories and closures due to lack of compliance with Environmental Protection Agency guidelines. We conducted the first statewide beach water quality assessment by analyzing decadal records of fecal indicator bacteria (enterococci and fecal coliform) levels at 262 Florida beaches. The objectives were to depict synoptic patterns of beach water quality exceedance along the entire Florida shoreline and to evaluate their relationships with wave condition and geographic location. Percent exceedances based on enterococci and fecal coliform were negatively correlated with both long-term mean wave energy and beach slope. Also, Gulf of Mexico beaches exceeded the thresholds significantly more than Atlantic Ocean ones, perhaps partially due to the lower wave energy. A possible linkage between wave energy level and water quality is beach sand, a pervasive nonpoint source that tends to harbor more bacteria in the low-wave-energy environment.
Analysis of efficient preconditioned defect correction methods for nonlinear water waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter
2014-01-01
prediction of free-surface wave transformation and accurate wave kinematics in both deep and shallow waters in large marine areas or for predicting the outcome of experiments in large numerical wave tanks. We revisit the classical governing equations are fully nonlinear and dispersive potential flow......Robust computational procedures for the solution of non-hydrostatic, free surface, irrotational and inviscid free-surface water waves in three space dimensions can be based on iterative preconditioned defect correction (PDC) methods. Such methods can be made efficient and scalable to enable...... models. Our study is particularly relevant for fast and efficient simulation of non-breaking fully nonlinear water waves over varying bottom topography that may be limited by computational resources or requirements. To gain insight into algorithmic properties and proper choices of discretization...
Determination of hydrocarbon levels in water via laser-induced acoustics wave
Bidin, Noriah; Hossenian, Raheleh; Duralim, Maisarah; Krishnan, Ganesan; Marsin, Faridah Mohd; Nughro, Waskito; Zainal, Jasman
2016-04-01
Hydrocarbon contamination in water is a major environmental concern in terms of foreseen collapse of the natural ecosystem. Hydrocarbon level in water was determined by generating acoustic wave via an innovative laser-induced breakdown in conjunction with high-speed photographic coupling with piezoelectric transducer to trace acoustic wave propagation. A Q-switched Nd:YAG (40 mJ) was focused in cuvette-filled hydrocarbon solution at various concentrations (0-2000 ppm) to induce optical breakdown, shock wave generation and later acoustic wave propagation. A nitro-dye (ND) laser (10 mJ) was used as a flash to illuminate and frozen the acoustic wave propagation. Lasers were synchronised using a digital delay generator. The image of acoustic waves was grabbed and recorded via charged couple device (CCD) video camera at the speed of 30 frames/second with the aid of Matrox software version 9. The optical delay (0.8-10.0 μs) between the acoustic wave formation and its frozen time is recorded through photodetectors. A piezo-electric transducer (PZT) was used to trace the acoustic wave (sound signal), which cascades to a digital oscilloscope. The acoustic speed is calculated from the ratio of acoustic wave radius (1-8 mm) and optical time delay. Acoustic wave speed is found to linearly increase with hydrocarbon concentrations. The acoustic signal generation at higher hydrocarbon levels in water is attributed to supplementary mass transfer and impact on the probe. Integrated high-speed photography with transducer detection system authenticated that the signals indeed emerged from the laser-induced acoustic wave instead of photothermal processes. It is established that the acoustic wave speed in water is used as a fingerprint to detect the hydrocarbon levels.
Energy Technology Data Exchange (ETDEWEB)
Ohta, N; Niki, T; Kirihara, S, E-mail: n-ohta@jwri.osaka-u.ac.jp [Smart Processing Research Center, Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka, 567-0047 (Japan)
2011-05-15
Terahertz wave resonators composed of alumina photonic crystals with diamond lattice structures were designed and fabricated by using micro stereolithography. These three dimensional periodic structures can reflect perfectly electromagnetic waves through Bragg diffraction. A micro glass cell including water solutions was put between the photonic crystals as a novel resonance sensor with terahertz frequency range. The localized and amplified waves in the resonators were measured by a spectroscopy, and visualized by theoretical simulations.
Diffraction of Water Waves by A Vertically Floating Cylinder in A Two-Layer Fluid
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
In this paper, the diffraction of water waves by a vertically floating cylinder in a two-layer luid of a finite depth is studied. Analytical expressions for the hydrodynamic loads on the vertically floating cylinder are obtained by use of the method of eigenfunction expansions. The hydrodynamic loads on the vertically floating cylinder in a two-layer fluid include not only the surge, heave and pitch exciting forces due to the incident wave of the surface-wave mode, but also those due to the incident wave of the internal-wave mode. This is different from the case of a homogenous fluid. Some given examples show that, for a two-layer fluid system with a small density difference, the hydrodynamic loads for the surface-wave mode do not differ significantly from those due to surface waves in a single-layer fluid, but the hydrodynamic loads for the internal-wave mode are important over a wide range of frequencies. Moreover, also considered are the free surface and interface elevations generated by the diffraction wave due to the incident wave of the surface-wave and internal-wave modes, and transfer of energy between modes.
Institute of Scientific and Technical Information of China (English)
李保忠; 蔡袁强
2003-01-01
Biot's two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasi-transverse wave (QSV) and the anti-plane transverse wave (SH). Numerical results are given to illustrate the influence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering.
Estimation of wave directional spreading in shallow water
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Deo, M.C.; Anand, N.M.; Chandramohan, P.
) G(2s +1) (5) and G is the gamma function, s is the spreading parameter and u m is the mean wave direction. Here the value of the parameter s controls directional spreading around the mean wave direction. Cartwright (1963) showed that s can be related... = a 2 2 + b 2 2 a 0 (7) For fairly steady wind condition and mild sea states parameter s can be expressed as a function of relative frequency (f/f m ) and wave age (c m /U) (Mitsuyasu et al., 1975), as under: s 3 = 11.5(c m /U) 2.5 (f/f m ) b (8) where...
Folded localized excitations in the (2+1)-dimensional modified dispersive water-wave system
Institute of Scientific and Technical Information of China (English)
Lei Yan; Ma Song-Hua; Fang Jian-Ping
2013-01-01
By using a mapping approach and a linear variable separation approach,a new family of solitary wave solutions with arbitrary functions for the (2+1)-dimensional modified dispersive water-wave system (MDWW) is derived.Based on the derived solutions and using some multi-valued functions,we obtain some novel folded localized excitations of the system.
Gravity waves on water with non-uniform depth and current
Booij, N.
1981-01-01
A mathematical model for the combined refraction-diffraction of linear periodic gravity waves on water is developed, in which the influence of inhomogeneities of depth and current is taken into account. The model is used to compute partial reflection of waves a gully or an undersea slope, with influ
Evolution of Weakly Nonlinear Water Waves in the Presence of Viscosity and Surfactant
1989-08-14
Pliny, 77 A.D. Naturalis Historia . Book ii, Chapter 107, section 234. Reynolds, 0. 1880 On the effect of oil on destroying waves on the surface of water...fluid. J. Appl . Mech. Tech. Phy., 9, 190-194. * 36 I 77 7 I LIST OF FIGURES Figure 1. Evolution of modulations for inviscid gravity waves (A = 0) when the
A numerical study of lowest-order short-crested water wave instabilities
DEFF Research Database (Denmark)
Fuhrman, David R.; Madsen, Per A.
2005-01-01
This work presents the first numerical simulations of the long-term evolution of doubly-periodic short-crested wave instabilities, which are the simplest cases involving the three-dimensional instability of genuinely three-dimensional progressive water waves. The simulated evolutions reveal...
Gravity waves on water with non-uniform depth and current
Booij, N.
1981-01-01
A mathematical model for the combined refraction-diffraction of linear periodic gravity waves on water is developed, in which the influence of inhomogeneities of depth and current is taken into account. The model is used to compute partial reflection of waves a gully or an undersea slope, with influ
A plethora of generalised solitary gravity-capillary water waves
Clamond, Didier; Duran, Angel
2014-01-01
The present study describes, first, an efficient algorithm for computing gravity-capillary solitary waves solutions of the irrotational Euler equations and, second, provides numerical evidences of the existence of (likely) an infinite number of generalised solitary waves (i.e. solitary waves with undamped oscillatory wings). Using conformal mapping, the unknown fluid domain (which is to be determined) is mapped into a uniform strip of the complex plane. A Babenko-like equation is then derived from a Lagrangian expressed in the transformed domain. The Babenko equation is then solved numerically using a Levenberg-Marquardt algorithm. Various interesting solutions are computed, some of them being known, some seem to be new. The emergence of generalised solitary waves is shown when the Bond number is increased.
A Spectral Element Method for Nonlinear and Dispersive Water Waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Bigoni, Daniele; Eskilsson, Claes
The use of flexible mesh discretisation methods are important for simulation of nonlinear wave-structure interactions in offshore and marine settings such as harbour and coastal areas. For real applications, development of efficient models for wave propagation based on unstructured discretisation...... methods is of key interest. We present a high-order general-purpose three-dimensional numerical model solving fully nonlinear and dispersive potential flow equations with a free surface.......The use of flexible mesh discretisation methods are important for simulation of nonlinear wave-structure interactions in offshore and marine settings such as harbour and coastal areas. For real applications, development of efficient models for wave propagation based on unstructured discretisation...
Shallow water modal evolution due to nonlinear internal waves
Badiey, Mohsen; Wan, Lin; Luo, Jing
2017-09-01
Acoustic modal behavior is reported for an L-shape hydrophone array during the passage of a strong nonlinear internal wave packet. Acoustic track is nearly parallel to the front of nonlinear internal waves. Through modal decomposition at the vertical array, acoustic modes are identified. Modal evolution along the horizontal array then is examined during a passing internal wave. Strong intensity fluctuations of individual modes are observed before and during the internal waves packet passes the fixed acoustic track showing a detailed evolution of the waveguide modal behavior. Acoustic refraction created either uneven distribution of modal energy over the horizontal array or additional returns observable at the entire L-shape array. Acoustic ray-mode simulations are used to phenomenologically explain the observed modal behavior.
A penalization method for calculating the flow beneath travelling water waves of large amplitude
Constantin, Adrian; Scherzer, Otmar
2014-01-01
A penalization method for a suitable reformulation of the governing equations as a constrained optimization problem provides accurate numerical simulations for large-amplitude travelling water waves in irrotational flows and in flows with constant vorticity.
A thermistor probe for measuring particle orbital speed in water waves
National Research Council Canada - National Science Library
Eagleson, P.S; van de Watering, W.P.M
1964-01-01
The development of a thermistor probe and the necessary additional electronic circuitry to measure temporal and spatial distribution of the magnitude of the orbital velocity in water waves is described...
Video measurements of fluid velocities and water levels in breaking waves
CSIR Research Space (South Africa)
Govender, K
2002-01-01
Full Text Available The cost-effective measurement of the velocity flow fields in breaking water waves, using particle and correlation image velocimetry, is described. The fluid velocities are estimated by tracking the motion of neutrally buoyant particles and aeration...
Modeling Wind Wave Evolution from Deep to Shallow Water
2014-09-30
laboratory video observations of waves breaking over an artificial reef is excellent (see Figure 3), suggesting that both nonlinearity and dissipation...1996) are ongoing. Figure 3 Smoothed-Particle Hydrodynamics (SPH) simulations of waves breaking over an artificial reef in the laboratory (see...correspondence in the tail . The non-linear interactions transfer energy from the primary peak(s) of the spectrum to the higher (and lower) frequencies. For
Nonlinear Wave-Currents interactions in shallow water
Lannes, David
2015-01-01
We study here the propagation of long waves in the presence of vorticity. In the irrotational framework, the Green-Naghdi equations (also called Serre or fully nonlinear Boussinesq equations) are the standard model for the propagation of such waves. These equations couple the surface elevation to the vertically averaged horizontal velocity and are therefore independent of the vertical variable. In the presence of vorticity, the dependence on the vertical variable cannot be removed from the vorticity equation but it was however shown in [?] that the motion of the waves could be described using an extended Green-Naghdi system. In this paper we propose an analysis of these equations, and show that they can be used to get some new insight into wave-current interactions. We show in particular that solitary waves may have a drastically different behavior in the presence of vorticity and show the existence of solitary waves of maximal amplitude with a peak at their crest, whose angle depends on the vorticity. We als...
Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon
Directory of Open Access Journals (Sweden)
A. Torres-Freyermuth
2012-12-01
Full Text Available Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon are investigated by means of a phase-resolving non-hydrostatic wave model (SWASH. This model solves the nonlinear shallow water equations including non-hydrostatic pressure. The one-dimensional version of the model is implemented in order to investigate wave transformation in fringing reefs. Firstly, the numerical model is validated with (i laboratory experiments conducted on a physical model (Demirbilek et al., 2007and (ii field observations (Coronado et al., 2007. Numerical results show good agreement with both experimental and field data. The comparison against the physical model results, for energetic wave conditions, indicates that high- and low-frequency wave transformation is well reproduced. Moreover, extreme water-level conditions measured during the passage of Hurricane Ivan in Puerto Morelos are also estimated by the numerical tool. Subsequently, the model is implemented at different along-reef locations in Puerto Morelos. Extreme water levels, wave-induced setup, and infragravity wave energy are estimated inside the reef lagoon for different storm wave conditions (H_{s} >2 m. The numerical results revealed a strong correlation between the offshore sea-swell wave energy and the setup. In contrast, infragravity waves are shown to be the result of a more complex pattern which heavily relies on the reef geometry. Indeed, the southern end of the reef lagoon provides evidence of resonance excitation, suggesting that the reef barrier may act as either a natural flood protection morphological feature, or as an inundation hazard enhancer depending on the incident wave conditions.
Study of Atomization of a Water Jet by High-Intensity Aerial Ultrasonic Waves
Ito, Youichi
2001-05-01
An experimental study has been carried out on the atomization of a water jet by aerially radiating it with high-intensity ultrasonic waves. A sound source that enables the linear generation of high-intensity aerial ultrasonic waves (frequency: approximately 20 kHz) is combined with a cylindrical reflection plate in order to create a standing-wave sound field. An attempt has been made to atomize a water jet of 1 mm diameter by passing it through the above sound field at a velocity of approximately 30 m/s. It has been clarified that nodes of sound pressure in the standing-wave sound field are effective for the atomization of a water jet. In addition, the atomizing phenomenon of a water jet has been observed precisely. The relation between the intensity of sound waves required for atomization and the radiation duration has also been clarified. Even the radiation of sound waves for only 2 ms atomizes water. This suggests that a very fast water jet at 300-500 m/s might be atomized.
Sediment waves with a biogenic twist in Pleistocene cool water carbonates, Great Australian Bight
DEFF Research Database (Denmark)
Anderskouv, Kresten; Surlyk, Finn; Huuse, Mads;
2010-01-01
on the Galathea 3 expedition in 2006, allowing description of the morphology and internal architecture of the sediment waves in unprecedented detail, leading to an alternative interpretation of their formation. Most sediment waves were initiated by preferential deposition on the landward side of irregular erosion...... surfaces. Sediment wave accretion took place under the influence of density driven currents, which decelerated up the landward-dipping flanks and accelerated down the seaward-dipping flanks of the sediment waves. The currents are interpreted as dense water cascades formed by summer evaporation and strong...
On shallow water waves in a medium with time-dependent
Directory of Open Access Journals (Sweden)
Hamdy I. Abdel-Gawad
2015-07-01
Full Text Available In this paper, we studied the progression of shallow water waves relevant to the variable coefficient Korteweg–de Vries (vcKdV equation. We investigated two kinds of cases: when the dispersion and nonlinearity coefficients are proportional, and when they are not linearly dependent. In the first case, it was shown that the progressive waves have some geometric structures as in the case of KdV equation with constant coefficients but the waves travel with time dependent speed. In the second case, the wave structure is maintained when the nonlinearity balances the dispersion. Otherwise, water waves collapse. The objectives of the study are to find a wide class of exact solutions by using the extended unified method and to present a new algorithm for treating the coupled nonlinear PDE’s.
Green-Naghdi Theory,Part A: Green-Naghdi (GN) Equations for Shallow Water Waves
Institute of Scientific and Technical Information of China (English)
William C. Webster; Wenyang Duan; Binbin Zhao
2011-01-01
In this work,Green-Naghdi (GN) equations with general weight functions were derived in a simple way.A wave-absorbing beach was also considered in the general GN equations.A numerical solution for a level higher than 4 was not feasible in the past with the original GN equations.The GN equations for shallow water waves were simplified here,which make the application of high level (higher than 4) equations feasible.The linear dispersion relationships of the first seven levels were presented.The accuracy of dispersion relationships increased as the level increased.Level 7 GN equations are capable of simulating waves out to wave number times depth kd ＜ 26.Numerical simulation of nonlinear water waves was performed by use of Level 5 and 7 GN equations,which will be presented in the next paper.
Exploiting the orbital motion of water particles for energy extraction from waves
Energy Technology Data Exchange (ETDEWEB)
Ahmed, M. Rafiuddin; Faizal, Mohammed; Prasad, Krishnil [University of the South Pacific, Suva (Fiji)
2010-04-15
In wave motion, the water particles are known to follow orbital paths. This orbital motion was used to drive five-bladed Savonius rotors. Experiments were performed on an array of four rotors placed in a two-dimensional (2-D) wave channel. The flow around the rotors was documented using particle image velocimetry measurements. The submergence of the rotors and the distance between them were varied, and the rotational speeds of the rotors (Nn) were recorded at different wave frequencies. It was found that rotational speeds increased with an increase in the wave frequency, as it amplified the wave height that increased the kinetic energy of the particles in their orbital motion. The rotational speeds decreased when the distance between the rotors increased. High rotational speeds are recorded when the array of the rotors is placed close to the water surface at the smallest centre-to-centre distance between the rotors
Dynamics simulation of bottom high-sediment sea water movement under waves
Institute of Scientific and Technical Information of China (English)
Xueyi YOU; Wei LIU; Houpeng XIAO
2009-01-01
The movement of bottom high-sediment sea water under water waves, especially that of the high-sediment water layer close to the sea bottom, is important to the resuspension and settlement of sediment. Supposing that the high-sediment sea water is a Newtonian fluid,based on Navier-Stokes (N-S) theory, the movement of the interfaces of air-water and water-sediment water was tracked by the volume of fluid (VOF) method. The velocity field of sediment water was simulated by considering the effect of water waves. The results show that the movement of sediment water is very different from that of sea water,which provides a solid basis for understanding the resuspension and settlement of sediment and the formation of bottom stripe, and the VOF method can trace the movement of the two interfaces simultaneously; the movement of the air-water interface has a strong effect on that of the water-sediment water interface, while the effect of the water-sediment water interface movement on the air-water interface is not obvious.
OBLIQUE WATER WAVES IMPACTING ON A THIN POROUS WALL WITH A PARTIAL-SLIPPING BOUNDARY CONDITION
Institute of Scientific and Technical Information of China (English)
HSU Hao-Jen; HUANG Liang-Hsiung
2011-01-01
When an incoming water wave is parallel to a porous breakwater, a paradoxical phenomenon exists in that by strictly following the potential flow boundary condition of normal flux continuity on the interfaces, the water wave permeates the wall completely, regardless of breakwater porosity. To account for this paradoxical phenomenon when solving the problem of water waves obliquely impacting on a thin porous wall, a new partial-slipping boundary condition on the thin porous wall for potential flow is proposed. Analytical results show that when the water wave is parallel to a thin porous wall (i.e., the incident angle equals to 90°),the transmitted wave side remains quiescent, i.e., the transmitted wave side does not capture any wave energy when no viscous effect exists. This reveals that the above-mentioned paradoxical phenomenon disappears. The viscous boundary layer effect is also investigated in this study, which provides proper boundary conditions on a thin porous wall for viscous flows and detailed flow information.
Self-similar propagation of Hermite-Gauss water-wave pulses.
Fu, Shenhe; Tsur, Yuval; Zhou, Jianying; Shemer, Lev; Arie, Ady
2016-01-01
We demonstrate both theoretically and experimentally propagation dynamics of surface gravity water-wave pulses, having Hermite-Gauss envelopes. We show that these waves propagate self-similarly along an 18-m wave tank, preserving their general Hermite-Gauss envelopes in both the linear and the nonlinear regimes. The measured surface elevation wave groups enable observing the envelope phase evolution of both nonchirped and linearly frequency chirped Hermite-Gauss pulses, hence allowing us to measure Gouy phase shifts of high-order Hermite-Gauss pulses for the first time. Finally, when increasing pulse amplitude, nonlinearity becomes essential and the second harmonic of Hermite-Gauss waves was observed. We further show that these generated second harmonic bound waves still exhibit self-similar Hermite-Gauss shapes along the tank.
Wave breaking onset of two-dimensional deep-water wave groups in the presence and absence of wind
Saket, Arvin; Banner, Michael L; Barthelemy, Xavier; Allis, Michael J
2015-01-01
The criterion for the initiation of breaking demonstrated numerically by Barthelemy et al. (2015) has been investigated in the laboratory for unidirectional wave groups in deep-water and extended to include conditions of moderate wind forcing. Thermal Image Velocimetry was used to compare measurements of the crest surface water particle velocity (Us) with the wave crest velocity (C), as determined by an array of closely-spaced wave gauges. The energy flux ratio Bx = Us/C that distinguishes maximum recurrence from marginal breaking was found to be 0.840 $\\pm$ 0.016 in good agreement with the numerically determined value of 0.855. Further, the threshold was found to be robust for different classes of wave groups of distinct characteristic steepness at the breaking threshold. Increasing wind forcing from zero to U{\\lambda}/4/C0=1.42 increased this threshold by 2%. Increasing the spectral bandwidth (decreasing the Benjamin-Feir index from 0.39 to 0.31) systematically reduced the threshold by 1.5%.
Numerical Study of Submerged Vertical Plane Jets Under Progressive Water Surface Waves
Institute of Scientific and Technical Information of China (English)
DAI Hui-chao; WANG Ling-ling
2005-01-01
When wastewater is discharged into a coastal area through an outfall system, it will always be subjected to the action of waves. It is important to study and quantify the mixing of the discharge with the ambient water so that accurate environmental impact assessment can be made for such discharge conditions. The present work aims to study the phenomenon of a plane jet discharged into water environment with regular waves. A 3D numerical model based on the full Navier-Stokes equations (NSE) in the σ-coordinate is developed to study the present problem. Turbulence effects are modeled by a subgrid-scale (SGS) model using the concept of large eddy simulation (LES). The operator splitting method is used to solve the modified NSE. The model has been applied to the simulation of three different cases of submerged plane jets with surface waves: jet with strong waves, jet with weak waves and jet without waves. Numerical results show that the waves enhance the mixing of the jet with the ambient fluid, and cause a periodic deflection of the jet. The size of the re-circulation is about 1.5～2.4 depth of water. The velocity profile of the jet is self-similar in the zone of established flow for both the pure jet and jet in wave circumstances. The spreading characteristic constant α is 0.100 and 0.105 for pure momentum jets with Re numbers 1025 and 2050. The value of α increases from 0.130 to 0.147 for a jet in weak and strong wave circumstances, showing that waves have an obvious effect on the mixing and dilution properties of jets. Numerical results are in good agreement with the experimental data for the cases of pure jets and jets with waves.
Ultrasonic Waves in Water Visualized With Schlieren Imaging
Juergens, Jeffrey R.
2000-01-01
The Acoustic Liquid Manipulation project at the NASA Glenn Research Center at Lewis Field is working with high-intensity ultrasound waves to produce acoustic radiation pressure and acoustic streaming. These effects can be used to propel liquid flows to manipulate floating objects and liquid surfaces. Interest in acoustic liquid manipulation has been shown in acoustically enhanced circuit board electroplating, microelectromechanical systems (MEMS), and microgravity space experiments. The current areas of work on this project include phased-array ultrasonic beam steering, acoustic intensity measurements, and schlieren imaging of the ultrasonic waves.
Matsushita, Satoki; Matsuo, Hiroshi
2003-02-01
Further analysis has been made on the millimeter- and submillimeter-wave (100-1600GHz or 3mm-188 μm) atmospheric opacity data taken with the Fourier Transform Spectrometer (FTS) at Pampa la Bola, 4800 m above the sea level in northern Chile, which is the site of the Atacama Large Millimeter/submillimeter Array (ALMA). Time-sequence plots of millimeter- and submillimeter-wave opacities show similar variations to each other, except for during the periods with liquid water (fog or clouds) in the atmosphere. Using millimeter- and submillimeter-wave opacity correlations under two conditions, which are affected and not affected by liquid water, we succeeded to separate the measured opacity into water vapor and liquid water opacity components. The water vapor opacity shows a good correlation with the 183GHz water vapor line opacity, which is also covered in the measured spectra. On the other hand, the liquid water opacity and the 183GHz line opacity show no correlation. S ince only the water vapor component is expected to affect the phase of interferometers significantly, and the submillimeter-wave opacity is less affected by the liquid water component, it may be possible to use the submillimeter-wave opacity for a phase correction of submillimeter interferometers.
An implicit discontinuous Galerkin finite element model for water waves
van der Vegt, Jacobus J.W.; Ambati, V.R.; Bokhove, Onno
2005-01-01
We discuss a new higher order accurate discontinuous Galerkin finite element method for non-linear free surface gravity waves. The algorithm is based on an arbitrary Lagrangian Eulerian description of the flow field using deforming elements and a moving mesh, which makes it possible to represent
Directory of Open Access Journals (Sweden)
Dhar A.K.
2015-05-01
Full Text Available Fourth order nonlinear evolution equations, which are a good starting point for the study of nonlinear water waves, are derived for deep water surface capillary gravity waves in the presence of second waves in which air is blowing over water. Here it is assumed that the space variation of the amplitude takes place only in a direction along which the group velocity projection of the two waves overlap. A stability analysis is made for a uniform wave train in the presence of a second wave train. Graphs are plotted for the maximum growth rate of instability wave number at marginal stability and wave number separation of fastest growing sideband component against wave steepness. Significant improvements are noticed from the results obtained from the two coupled third order nonlinear Schrödinger equations.
Overdetermined Shooting Methods for Computing Standing Water Waves with Spectral Accuracy
Wilkening, Jon
2012-01-01
A high-performance shooting algorithm is developed to compute time-periodic solutions of the free-surface Euler equations with spectral accuracy in double and quadruple precision. The method is used to study resonance and its effect on standing water waves. We identify new nucleation mechanisms in which isolated large-amplitude solutions, and closed loops of such solutions, suddenly exist for depths below a critical threshold. We also study degenerate and secondary bifurcations related to Wilton's ripples in the traveling case, and explore the breakdown of self-similarity at the crests of extreme standing waves. In shallow water, we find that standing waves take the form of counter-propagating solitary waves that repeatedly collide quasi-elastically. In deep water with surface tension, we find that standing waves resemble counter-propagating depression waves. We also discuss existence and non-uniqueness of solutions, and smooth versus erratic dependence of Fourier modes on wave amplitude and fluid depth. In t...
Wind wave analysis in depth limited water using OCEANLYZ, A MATLAB toolbox
Karimpour, Arash; Chen, Qin
2017-09-01
There are a number of well established methods in the literature describing how to assess and analyze measured wind wave data. However, obtaining reliable results from these methods requires adequate knowledge on their behavior, strengths and weaknesses. A proper implementation of these methods requires a series of procedures including a pretreatment of the raw measurements, and adjustment and refinement of the processed data to provide quality assurance of the outcomes, otherwise it can lead to untrustworthy results. This paper discusses potential issues in these procedures, explains what parameters are influential for the outcomes and suggests practical solutions to avoid and minimize the errors in the wave results. The procedure of converting the water pressure data into the water surface elevation data, treating the high frequency data with a low signal-to-noise ratio, partitioning swell energy from wind sea, and estimating the peak wave frequency from the weighted integral of the wave power spectrum are described. Conversion and recovery of the data acquired by a pressure transducer, particularly in depth-limited water like estuaries and lakes, are explained in detail. To provide researchers with tools for a reliable estimation of wind wave parameters, the Ocean Wave Analyzing toolbox, OCEANLYZ, is introduced. The toolbox contains a number of MATLAB functions for estimation of the wave properties in time and frequency domains. The toolbox has been developed and examined during a number of the field study projects in Louisiana's estuaries.
On the time varying horizontal water velocity of single, multiple, and random gravity wave trains
Wells, D.R.
1964-01-01
In this dissertation some characteristics of the horizontal water velocity for single, multiple, and random gravity wave trains are studied. This work consists of two parts, an analogue study and hydraulic measurements. An important aspect in this work is to suggest the horizontal water velocity asy
On the Effect of Green Water on Deck on the Wave Bending Moment
DEFF Research Database (Denmark)
Wang, Zhaohui; Jensen, Jørgen Juncher; Xia, Jinzhu
1998-01-01
The aim of the present work is to investigate whether green water on deck in severe sea states have a notable effect on the maximum wave bending moments. The analysis is carried out for an S175 container ship for which results from model experiments are available. The static water head and a mome...
Experimental study on the relation between the water content of surface soil and the acoustic wave
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
In order to investigate the relation between the water content changing of surface soil and micro-quake recorded before earthquakes, we carried out a simulation experiment in laboratory. Its purpose is to explore whether the acoustic wave generated by micro-fracturing before earthquake are able to change water content of surface soil, so as to understand the relation between thermal anomaly in the remote sensing image got from the seismogenic area and the coming earthquake. The result of the experiment shows that when the acoustic wave enters into the surface soil the water content here increases on the background of decreasing due to natural evaporation. In the meantime, temperature here decreases.
Oil slicks on water surface: Breakup, coalescence, and droplet formation under breaking waves.
Nissanka, Indrajith D; Yapa, Poojitha D
2017-01-15
The ability to calculate the oil droplet size distribution (DSD) and its dynamic behavior in the water column is important in oil spill modeling. Breaking waves disperse oil from a surface slick into the water column as droplets of varying sizes. Oil droplets undergo further breakup and coalescence in the water column due to the turbulence. Available models simulate oil DSD based on empirical/equilibrium equations. However, the oil DSD evolution due to subsequent droplet breakup and coalescence in the water column can be best represented by a dynamic population model. This paper develops a phenomenological model to calculate the oil DSD in wave breaking conditions and ocean turbulence and is based on droplet breakup and coalescence. Its results are compared with data from laboratory experiments that include different oil types, different weathering times, and different breaking wave heights. The model comparisons showed a good agreement with experimental data.
Bound on the Slope of Steady Water Waves with Favorable Vorticity
Strauss, Walter A.; Wheeler, Miles H.
2016-12-01
We consider the angle {θ} of inclination (with respect to the horizontal) of the profile of a steady two dimensional inviscid symmetric periodic or solitary water wave subject to gravity. Although {θ} may surpass 30° for some irrotational waves close to the extreme wave, Amick (Arch Ration Mech Anal 99(2):91-114, 1987) proved that for any irrotational wave the angle must be less than 31.15°. Is the situation similar for periodic or solitary waves that are not irrotational? The extreme Gerstner wave has infinite depth, adverse vorticity and vertical cusps ( θ = 90°). Moreover, numerical calculations show that even waves of finite depth can overturn if the vorticity is adverse. In this paper, on the other hand, we prove an upper bound of 45° on {θ} for a large class of waves with favorable vorticity and finite depth. In particular, the vorticity can be any constant with the favorable sign. We also prove a series of general inequalities on the pressure within the fluid, including the fact that any overturning wave must have a pressure sink.
Irregular Wave-Induced Velocities in Shallow Water
1992-09-01
and Acceleration of the Surface of Wind Waves," Rep. Res. Inst. Appl . Mech. (Kyushu Univ.), 24, No. 76, 31-48. 19, Hughes, S.A. (1991) "Estimating...8217 siilk 2 i- (D½ 0 0 411 0 Ursoll No. 0.1 10 100 1000 10000 Ursell No. W (.), z-mid-depth W (#), z-bottom W (-), z-mid-depth W (-), z-bottom (b) Figure 72
Lake Michigan Storm: Wave and Water Level Modeling
2012-11-01
intra-annual growth and decay of shore-fast ice . The resulting wave and surge estimates will be altered because of the spatial distribution of the... Arctic Sea ice . JGR. Vol. 78, pp. 7871- 7883. Barnes, S.L., (1964). “A technique for maximizing details in numerical weather map analysis,” J. Appl...developing necessary fields from point source meteorological stations on a fixed grid system (1960 though 1978). Archived ice concentration fields were
The Effect of Water on Seismic Wave Speeds of the Martian Mantle.
Martin, J. F.; Panero, W. R.
2016-12-01
We calculate the distribution of water between mineral phases of the Martian mantle, and the effects of water on the seismic wave speeds along realistic thermal profiles and compositions. We address a range of potential compositions and thermal profiles of the Martian mantle to reflect uncertainty in core heat-flux and mantle composition. We calculate the mantle mineralogy self-consistently along each potential profile and derive water partition coefficients for all phases from a suite of synthesis and mineralogical data to supplement ab initio calculations. Self-consistent water contents for each mineral phase are then calculated along a 1D profile using the derived coefficients and a range of bulk water contents. We present the change in seismic wave speeds due to water storage in the mantle for interpretation of seismic data returned by the NASA InSight Mission, set to land on Mars in November 2018.
Yao, Yanyan; Jiang, Tao; Zhang, Limin; Chen, Xiangyu; Gao, Zhenliang; Wang, Zhong Lin
2016-08-24
Ocean waves are one of the most promising renewable energy sources for large-scope applications due to the abundant water resources on the earth. Triboelectric nanogenerator (TENG) technology could provide a new strategy for water wave energy harvesting. In this work, we investigated the charging characteristics of utilizing a wavy-structured TENG to charge a capacitor under direct water wave impact and under enclosed ball collision, by combination of theoretical calculations and experimental studies. The analytical equations of the charging characteristics were theoretically derived for the two cases, and they were calculated for various load capacitances, cycle numbers, and structural parameters such as compression deformation depth and ball size or mass. Under the direct water wave impact, the stored energy and maximum energy storage efficiency were found to be controlled by deformation depth, while the stored energy and maximum efficiency can be optimized by the ball size under the enclosed ball collision. Finally, the theoretical results were well verified by the experimental tests. The present work could provide strategies for improving the charging performance of TENGs toward effective water wave energy harvesting and storage.
Observation of dispersive shock waves developing from initial depressions in shallow water
Trillo, S.; Klein, M.; Clauss, G. F.; Onorato, M.
2016-10-01
We investigate surface gravity waves in a shallow water tank, in the limit of long wavelengths. We report the observation of non-stationary dispersive shock waves rapidly expanding over a 90 m flume. They are excited by means of a wave maker that allows us to launch a controlled smooth (single well) depression with respect to the unperturbed surface of the still water, a case that contains no solitons. The dynamics of the shock waves are observed at different levels of nonlinearity equivalent to a different relative smallness of the dispersive effect. The observed undulatory behavior is found to be in good agreement with the dynamics described in terms of a Korteweg-de Vries equation with evolution in space, though in the most nonlinear cases the description turns out to be improved over the quasi linear trailing edge of the shock by modeling the evolution in terms of the integro-differential (nonlocal) Whitham equation.
Turbulent Supernova Shock Waves and the Sterile Neutrino Signature in Megaton Water Detectors
Choubey, S; Ross, Graham G; Choubey, Sandhya
2007-01-01
The signatures of sterile neutrinos in the supernova neutrino signal in megaton water Cerenkov detectors are studied. Time dependent modulation of the neutrino signal emerging from the sharp changes in the oscillation probability due to shock waves is shown to be a smoking gun for the existence of sterile neutrinos. These modulations and indeed the entire neutrino oscillation signal is found to be different for the case with just three active neutrinos and the cases where there are additional sterile species mixed with the active neutrinos. The effect of turbulence is taken into account and it is found that the effect of the shock waves, while modifed, remain significant and measurable. Supernova neutrino signals in water detectors can therefore give unambiguous proof for the existence of sterile neutrinos, the sensitivity extending beyond that for terrestial neutrino experiments. In addition the time dependent modulations in the signal due to shock waves can be used to trace the evolution of the shock wave i...
Reconstruction of stratified steady water waves from pressure readings on the ocean bed
Chen, Robin Ming
2015-01-01
Consider a two-dimensional stratified solitary wave propagating through a body of water that is bounded below by an impermeable ocean bed. In this work, we study how such a wave can be reconstructed from data consisting of the wave speed, upstream and downstream density profile, and the trace of the pressure on the bed. First, we prove that this data uniquely determines the wave, both in the (real) analytic and Sobolev regimes. Second, for waves that consist of multiple layers of constant density immiscible fluids, we provide an exact formula describing each of the interfaces in terms of the data. Finally, for continuously stratified fluids, we detail a reconstruction scheme based on approximation by layer-wise constant density flows.
Measurement of low-frequency ultrasonic wave in water using an acoustic fiber sensor.
Sakoda, Tatsuya; Sonoda, Yoshito
2006-04-01
An acoustic fiber sensor for measurement of ultrasonic waves, which used the approximate Raman-Nath diffraction effect where light diffraction waves were generated in an optical fiber by strain due to the ultrasonic waves, was proposed and examined. In order to characterize the acoustic fiber sensor as a basic study, measurements of low-frequency ultrasonic waves in water were examined using a step index fiber operating as a detection sensor. The results showed that characteristics of detected signals agreed with the theoretical prediction based on Fraunhofer diffraction. This indicates that our proposed fiber sensor can be used for the detection of low-frequency ultrasonic waves as well as the transmission of light diffraction signals.
Directory of Open Access Journals (Sweden)
Tor A. Johansen
2004-01-01
Full Text Available A new strategy for active control in heavy-lift offshore crane operations is suggested, by introducing a new concept referred to as wave synchronization. Wave synchronization reduces the hydrodynamic forces by minimization of variations in the relative vertical velocity between payload and water using a wave amplitude measurement. Wave synchronization is combined with conventional active heave compensation to obtain accurate control. Experimental results using a scale model of a semi-submerged vessel with a moonpool shows that wave synchronization leads to significant improvements in performance. Depending on the sea state and payload, the results indicate that the reduction in the standard deviation of the wire tension may be up to 50
Kinetic Flux Vector Splitting Method for the Shallow Water Wave Equations
Institute of Scientific and Technical Information of China (English)
施卫平; WeiShyy
2003-01-01
Based on the analogy to gas dynamics,the kinetic flux flux vector splitting (KFVS) method is used to stimulate the shallow water wave equations,The flus vectors of the equations are split on the basis of the local equilibrium Maxwell-Boltzmann distribution One dimensional examples including a dam breaking wave and flows over a ridge are calcualted.The solutions exhibit second-order accuracy with no spurious oscillation.
Testik, Firat Yener
An experimental and theoretical study has been conducted to obtain a fundamental understanding of the dynamics of the sand, water and a solid object interaction as progressive gravity waves impinge on a sloping beach. Aside from obvious scientific interest, this exceedingly complex physical problem is important for naval applications, related to the behavior of disk/cylindrical shaped objects (mines) in the coastal waters. To address this problem, it was divided into a set of simpler basic problems. To begin, nonlinear progressive waves were investigated experimentally in a wave tank for the case of a rigid (impermeable) sloping bottom. Parameterizations for wave characteristics were proposed and compared with the experiments. In parallel, a numerical wave tank model (NWT) was calibrated using experimental data from a single run, and wave field in the wave tank was simulated numerically for the selected experiments. Subsequently, a layer of sand was placed on the slope and bottom topography evolution processes (ripple and sandbar dynamics, bottom topography relaxation under variable wave forcing, etc.) were investigated experimentally. Models for those processes were developed and verified by experimental measurements. Flow over a circular cylinder placed horizontally on a plane wall was also studied. The far-flow field of the cylinder placed in the wave tank was investigated experimentally and numerical results from the NWT simulations were compared with the experimental data. In the mean time, the near-flow velocity/vorticity field around a short cylinder under steady and oscillatory flow was studied in a towing tank. Horseshoe vortex formation and periodic shedding were documented and explained. With the understanding gained through the aforementioned studies, dynamics and burial/scour around the bottom objects in the wave tank were studied. Possible scenarios on the behavior of the disk-shaped objects were identified and explained. Scour around 3D cylindrical
Optical tsunamis: shoaling of shallow water rogue waves in nonlinear fibers with normal dispersion
Wabnitz, Stefan
2013-01-01
In analogy with ocean waves running up towards the beach, shoaling of prechirped optical pulses may occur in the normal group-velocity dispersion regime of optical fibers. We present exact Riemann wave solutions of the optical shallow water equations and show that they agree remarkably well with the numerical solutions of the nonlinear Schr\\"odinger equation, at least up to the point where a vertical pulse front develops. We also reveal that extreme wave events or optical tsunamis may be generated in dispersion tapered fibers in the presence of higher-order dispersion.
On the integrability and quasi-periodic wave solutions of the Boussinesq equation in shallow water
Ma, Pan-Li; Tian, Shou-Fu; Tu, Jian-Min; Xu, Mei-Juan
2015-05-01
In this paper, the complete integrability of the Boussinesq equation in shallow water is systematically investigated. By using generalized Bell's polynomials, its bilinear formalism, bilinear Bäcklund transformations, Lax pairs of the Boussinesq equation are constructed, respectively. By virtue of its Lax equations, we find its infinite conservation laws. All conserved densities and fluxes are obtained by lucid recursion formulas. Furthermore, based on multidimensional Riemann theta functions, we construct periodic wave solutions of the Boussinesq equation. Finally, the relations between the periodic wave solutions and soliton solutions are strictly constructed. The asymptotic behaviors of the periodic waves are also analyzed by a limiting procedure.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Using the latest version of Mesoscale Modeling System (MM5v3), we assimilated wind data from the scatterometer and built a model to assimilate the wind field over eastern China seas and adjacent waters and applied the wave model WAVEWATCH-Ⅲ to test the sea area with assimilative wind and blended wind of QSCAT and NCEP as driving forces. High precision and resolution numerical wave results were obtained.Analysis indicated that ifwe replace the model wind result with the blended wind, better sea surface wind results and wave results could be obtained.
Linearized potential flow analysis of a 40 chamber, oscillating water column wave energy device
DEFF Research Database (Denmark)
Bingham, Harry B.; Read, Robert
coefficient to represent the air turbine Power Take Off (PTO) system is found for each condition by iterating to find the consistent response-damping pair for a given frequency and incident wave ampli- tude. The absorbed power is estimated based on the pressure in each chamber and the PTO damping coefficient......This abstract presents an analysis of an attenuator-type Wave Energy Converter (WEC) with 40 Os- cillating Water Column (OWC) chambers for the extraction of wave energy. Linearized potential flow calculations are made in the frequency-domain using WAMIT [8]. An equivalent linearized damping...
Travelling wave solutions for some two-component shallow water models
Dutykh, Denys; Ionescu-Kruse, Delia
2016-07-01
In the present study we perform a unified analysis of travelling wave solutions to three different two-component systems which appear in shallow water theory. Namely, we analyze the celebrated Green-Naghdi equations, the integrable two-component Camassa-Holm equations and a new two-component system of Green-Naghdi type. In particular, we are interested in solitary and cnoidal-type solutions, as two most important classes of travelling waves that we encounter in applications. We provide a complete phase-plane analysis of all possible travelling wave solutions which may arise in these models. In particular, we show the existence of new type of solutions.
Variational space-time (dis)continuous Galerkin method for nonlinear free surface water waves
Gagarina, E.; Ambati, V. R.; van der Vegt, J. J. W.; Bokhove, O.
2014-10-01
A new variational finite element method is developed for nonlinear free surface gravity water waves using the potential flow approximation. This method also handles waves generated by a wave maker. Its formulation stems from Miles' variational principle for water waves together with a finite element discretization that is continuous in space and discontinuous in time. One novel feature of this variational finite element approach is that the free surface evolution is variationally dependent on the mesh deformation vis-à-vis the mesh deformation being geometrically dependent on free surface evolution. Another key feature is the use of a variational (dis)continuous Galerkin finite element discretization in time. Moreover, in the absence of a wave maker, it is shown to be equivalent to the second order symplectic Störmer-Verlet time stepping scheme for the free-surface degrees of freedom. These key features add to the stability of the numerical method. Finally, the resulting numerical scheme is verified against nonlinear analytical solutions with long time simulations and validated against experimental measurements of driven wave solutions in a wave basin of the Maritime Research Institute Netherlands.
On utilizing the orbital motion in water waves to drive a Savonius rotor
Energy Technology Data Exchange (ETDEWEB)
Faizal, Mohammed; Rafiuddin Ahmed, M. [The University of the South Pacific, Laucala Campus, Suva (Fiji); Lee, Young-Ho [Korea Maritime University, 1 Dongsam-dong, Youngdo-Ku, Busan 606-791 (Korea)
2010-01-15
In wave motion, the water particles are known to follow orbital paths. This orbital motion was studied and a five bladed Savonius rotor was built to extract energy from the orbiting particles. Experiments were performed on a rotor placed parallel to the incoming waves in a two-dimensional wave channel by varying the frequency of the wave generator, which produced sinusoidal waves. The rotor submergence below the mean level was varied. The flow around the rotor was studied with particle image velocimetry (PIV) measurements. It was found that the rpm of the rotor (N{sub n}) increases with an increase in wave frequency. An increase in wave height also increases the N{sub n} values, as the kinetic energy of the particles' orbital motion increases. The optimum N{sub n} values are obtained when the rotor is placed close to the water surface at the minimum submergence of 1.06d where 'd' is the rotor diameter. (author)
Secondary current properties generated by wind-induced water waves in experimental conditions
Directory of Open Access Journals (Sweden)
Michio Sanjou
2014-06-01
Full Text Available Secondary currents such as the Langmuir circulation are of high interest in natural rivers and the ocean because they have striking impacts on scour, sedimentation, and mass transport. Basic characteristics have been well-studied in straight open-channel flows. However, little is known regarding secondary circulation induced by wind waves. The presented study describes the generation properties of wind waves observed in the laboratory tank. Wind-induced water waves are known to produce large scale circulations. The phenomenon is observed together with high-speed and low-speed streaks, convergence and divergence zones, respectively. Therefore, it is important to determine the hydrodynamic properties of secondary currents for wind-induced water waves within rivers and lakes. In this study, using two high-speed CMOS cameras, stereoscopic particle image velocimetry (PIV measurements were conducted in order to reveal the distribution of all three components of velocity vectors. The experiments allowed us to investigate the three-dimensional turbulent structure under water waves and the generation mechanism of large-scale circulations. Additionally, a third CMOS camera was used to measure the spanwise profile of thefree-surface elevation. The time-series of velocity components and the free-surface were obtained simultaneously. From our experiments, free-surface variations were found to influence the instantaneous velocity distributions of the cross-sectional plane. We also considered thegeneration process by the phase analysis related to gravity waves and compared the contribution of the apparent stress.
2015-08-01
ER D C/ CH L TR -1 5- 11 Development of an Extratropical Storm Wind , Wave, and Water Level Climatology for the Offshore Mid-Atlantic...Development of an Extratropical Storm Wind , Wave, and Water Level Climatology for the Offshore Mid-Atlantic Michael F. Forte Field Research Facility...of the extreme offshore wind , wave, and water level climate in the mid-Atlantic region has been conducted for the U.S. Bureau of Safety and
Effects of waves on water dispersion in a semi-enclosed estuarine bay
Delpey, M. T.; Ardhuin, F.; Otheguy, P.
2012-04-01
The bay of Saint Jean de Luz - Ciboure is a touristic destination located in the south west of France on the Basque coast. This small bay is 1.5km wide for 1km long. It is semi-enclosed by breakwaters, so that the area is mostly protected from waves except in its eastern part, where wave breaking is regularly observed over a shallow rock shelf. In the rest of the area the currents are generally weak. The bay receives fresh water inflows from two rivers. During intense raining events, the rivers can introduce pollutants in the bay. The input of pollutants combined with the low level dynamic of the area can affect the water quality for several days. To study such a phenomenon, mechanisms of water dispersion in the bay are investigated. The present paper focuses on the effects of waves on bay dynamics. Several field experiments were conducted in the area, combining wave and current measurements from a set of ADCP and ADV, lagrangian difter experiments in the surfzone, salinity and temperature profile measurements. An analysis of this set of various data is provided. It reveals that the bay combines remarkable density stratification due to fresh water inflows and occasionally intense wave-induced currents in the surfzone. These currents have a strong influence on river plume dynamics when the sea state is energetic. Moreover, modifications of hydrodynamics in the bay passes are found to be remarkably correlated with sea state evolutions. This result suggests a significant impact of waves on the bay flushing. To further analyse these phenomena, a three dimensional numerical model of bay hydrodynamics is developed. The model aims at reproducing fresh water inflows combined with wind-, tide- and wave-induced currents and mixing. The model of the bay is implemented using the code MOHID , which has been modified to allow the three dimensional representation of wave-current interactions proposed by Ardhuin et al. [2008b] . The circulation is forced by the wave field modelled
Analysis of Origin of Multi-Ring Basins by Theory of Deep Water Waves
Institute of Scientific and Technical Information of China (English)
SHI Jian-Chun; MA Yue-Hua; CHEN Dao-Han; BAO Gang
2008-01-01
The tsunami model of the origin of multi-ring basins is analysed with the theory of deep water waves generated by an initial surface deformation,which is set as a parabolic crater.We obtain an approximate formula for calculating the ring radius.The formula applied to some multi-ring basins on the Moon,Mercury and Mars gives almost equidistant spacing of the rings within the main ring (the IV ring); this agrees with the previous conclusion that the IV ring marks the end of the fluidized region.Besides this,the theory of deep water waves does not require similar crustal structure at each basin-impact site on all three planets which is required in the theory of shallow water waves.
Measuring Water Vapor and Ash in Volcanic Eruptions with a Millimeter-Wave Radar/Imager
Bryan, Sean; Vanderkluysen, Loÿc; Groppi, Christopher; Paine, Scott; Bliss, Daniel W; Aberle, James; Mauskopf, Philip
2016-01-01
Millimeter-wave remote sensing technology can significantly improve measurements of volcanic eruptions, yielding new insights into eruption processes and improving forecasts of drifting volcanic ash for aviation safety. Radiometers can measure water vapor density and temperature inside eruption clouds, improving on existing measurements with infrared cameras that are limited to measuring the outer cloud surface. Millimeter-wave radar can measure the 3D mass flow of volcanic ash inside eruption plumes and drifting fine ash clouds, offering better sensitivity than existing weather radar measurements and the unique ability to measure ash particle size in-situ. Here we present sensitivity calculations in the context of developing the WAMS (Water and Ash Millimeter-wave Spectrometer) instrument. WAMS, a radar/radiometer system constructed with off-the-shelf components, would be able to measure water vapor and ash throughout an entire eruption cloud, a unique capability.
Amrutha, M. M.; Sanil Kumar, V.
2016-12-01
Assessment of wave power potential at different water depths and time is required for identifying a wave power plant location. This study examines the variation in wave power off the central west coast of India at water depths of 30, 9 and 5 m based on waverider buoy measured wave data. The study shows a significant reduction ( ˜ 10 to 27 %) in wave power at 9 m water depth compared to 30 m and the wave power available at 5 m water depth is 20 to 23 % less than that at 9 m. At 9 m depth, the seasonal mean value of the wave power varied from 1.6 kW m-1 in the post-monsoon period (ONDJ) to 15.2 kW m-1 in the Indian summer monsoon (JJAS) period. During the Indian summer monsoon period, the variation of wave power in a day is up to 32 kW m-1. At 9 m water depth, the mean annual wave power is 6 kW m-1 and interannual variations up to 19.3 % are observed during 2009-2014. High wave energy ( > 20 kW m-1) at the study area is essentially from the directional sector 245-270° and also 75 % of the total annual wave energy is from this narrow directional sector, which is advantageous while aligning the wave energy converter.
Fan, Xiaofeng; Baek, Yonggeun; Ha, Kanglyeol; Kim, Moojoon; Kim, Jungsoon; Kim, Duckjong; Kang, Hyun Wook; Oh, Junghwan
2017-07-01
An optoacoustic transducer made of light-absorbing and elastomeric materials can generate high-pressure wide-band ultrasound waves in water when it is illuminated by a pulse laser. To generate such waves with high efficiency, carbon nanotubes (CNTs) and poly(dimethylsiloxane) (PDMS) are widely used as the light-absorbing and elastomeric materials, respectively. It was previously reported that an optoacoustic concave transducer made of these materials can produce strong shock waves, namely, blast waves, within its focal zone. In this study, we have shown that these waves can also be generated by a plane optoacoustic transducer fabricated by coating CNTs-PDMS on a poly(methyl methacrylate) (PMMA) plate. Some propagation characteristics of the blast wave generated were measured and compared with the calculated results. It was found that the propagation speed and attenuation of the wave are different from those of usual sounds. From the comparison of the measured and the calculated acoustic fields, it is assumed that every point on the transducer surface produces almost the same blast wave.
Experimental particle acceleration by water evaporation induced by shock waves
Scolamacchia, T.; Alatorre Ibarguengoitia, M.; Scheu, B.; Dingwell, D. B.; Cimarelli, C.
2010-12-01
Shock waves are commonly generated during volcanic eruptions. They induce sudden changes in pressure and temperature causing phase changes. Nevertheless, their effects on flowfield properties are not well understood. Here we investigate the role of gas expansion generated by shock wave propagation in the acceleration of ash particles. We used a shock tube facility consisting of a high-pressure (HP) steel autoclave (450 mm long, 28 mm in internal diameter), pressurized with Ar gas, and a low-pressure tank at atmospheric conditions (LP). A copper diaphragm separated the HP autoclave from a 180 mm tube (PVC or acrylic glass) at ambient P, with the same internal diameter of the HP reservoir. Around the tube, a 30 cm-high acrylic glass cylinder, with the same section of the LP tank (40 cm), allowed the observation of the processes occurring downstream from the nozzle throat, and was large enough to act as an unconfined volume in which the initial diffracting shock and gas jet expand. All experiments were performed at Pres/Pamb ratios of 150:1. Two ambient conditions were used: dry air and air saturated with steam. Carbon fibers and glass spheres in a size range between 150 and 210 μm, were placed on a metal wire at the exit of the PVC tube. The sudden decompression of the Ar gas, due to the failure of the diaphragm, generated an initial air shock wave. A high-speed camera recorded the processes between the first 100 μsec and several ms after the diaphragm failure at frame rates ranging between 30,000 and 50,000 fps. In the experiments with ambient air saturated with steam, the high-speed camera allowed to visualize the condensation front associated with the initial air shock; a maximum velocity of 788 m/s was recorded, which decreases to 524 m/s at distance of 0.5 ±0.2 cm, 1.1 ms after the diaphragm rupture. The condensation front preceded the Ar jet front exhausting from the reservoir, by 0.2-0.5 ms. In all experiments particles velocities following the initial
Distribution of water-group ion cyclotron waves in Saturn's magnetosphere
Chou, Marty; Cheng, Chio Zong
2017-09-01
The water-group ion cyclotron waves (ICWs) in Saturn's magnetosphere were studied using the magnetic field data provided by the MAG magnetometer on board the Cassini satellite. The period from January 2005 to December 2009, when the Cassini radial distance is smaller than 8 R S , was used. ICWs were identified by their left-hand circularly polarized magnetic perturbations and wave frequencies near the water-group ion gyrofrequencies. We obtained the spatial distribution of ICW amplitude and found that the source region of ICWs is mostly located in the low-latitude region, near the equator and inside the 6 R S radial distance. However, it can extend beyond 7 R S in the midnight region. In general, the wave amplitude is peaked slightly away from the equator, for all local time sectors in both the Northern and Southern Hemispheres. By assuming that the water-group ions are composed of pickup ions and background thermal ions, we obtained the local instability condition of the ICWs and estimated their growth rate along the field lines. If the wave amplitude is correlated with the growth rate, the observed latitudinal dependence of the wave amplitude can be well explained by the local stability analysis. Also, latitudinal location of the peak amplitude is found to depend on the local time. This implies a local time dependence for the water-group ion parallel temperature T|, as determined from the theoretical calculations. [Figure not available: see fulltext.
Explicit Kinetic Flux Vector Splitting Scheme for the 2-D Shallow Water Wave Equations
Institute of Scientific and Technical Information of China (English)
施卫平; 黄明游; 王婷; 张小江
2004-01-01
Originally, the kinetic flux vector splitting (KFVS) scheme was developed as a numerical method to solve gas dynamic problems. The main idea in the approach is to construct the flux based on the microscopical description of the gas. In this paper, based on the analogy between the shallow water wave equations and the gas dynamic equations, we develop an explicit KFVS method for simulating the shallow water wave equations. A 1D steady flow and a 2D unsteady flow are presented to show the robust and accuracy of the KFVS scheme.
Molecular Dynamics Simulation of Water Pore Formation in Lipid Bilayer Induced by Shock Waves
Koshiyama, Ken-ichiro; Kodama, Tetsuya; Yano, Takeru; Fujikawa, Shigeo
2006-05-01
Water molecule penetration into a bilayer hydrophobic region with a shock wave impulse has been investigated using molecular dynamics simulations [Koshiyama et al., AIP Conference Proceedings, 754, 104-106, (2005)]. Here we report results of simulation of spontaneous water pore formation in a bilayer that contains water molecules in the hydrophobic region in an initial state. The bilayers of 128 DPPC lipid and 3655 water molecules with insertion of 392, 784, and 1176 water molecules in the hydrophobic region are simulated. A water pore is spontaneously formed when 1176 water molecules exist in the hydrophobic region. The water pore diameter is estimated to be c.a. 1.9 nm, which is three times larger than that of 5-fluorouracil (5FU) used in cancer treatment.
Wave-induced mass transport affects daily Escherichia coli fluctuations in nearshore water
Ge, Zhongfu; Whitman, Richard L.; Nevers, Meredith B.; Phanikumar, Mantha S.
2012-01-01
Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s–1). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731–6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.
Experimental Study on Peak Pressure of Shock Waves in Quasi-Shallow Water
Directory of Open Access Journals (Sweden)
Zhenxiong Wang
2015-01-01
Full Text Available Based on the similarity laws of the explosion, this research develops similarity requirements of the small-scale experiments of underwater explosions and establishes a regression model for peak pressure of underwater shock waves under experimental condition. Small-scale experiments are carried out with two types of media at the bottom of the water and for different water depths. The peak pressure of underwater shock waves at different measuring points is acquired. A formula consistent with the similarity law of explosions is obtained and an analysis of the regression precision of the formula confirms its accuracy. Significance experiment indicates that the influence of distance between measuring points and charge on peak pressure of underwater shock wave is the greatest and that of water depth is the least within the range of geometric parameters. An analysis of data from experiments with different media at the bottom of the water reveals an influence on the peak pressure, as the peak pressure of a shock wave in a body of water with a bottom soft mud and rocks is about 1.33 times that of the case where the bottom material is only soft mud.
Lake St. Clair: Storm Wave and Water Level Modeling
2013-06-01
environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and...anemometer, barometer ) was changed. The station, if older than 1970, may have been referenced by WBAN number only, so a USAF number was added which would
Pathak, Ashish; Raessi, Mehdi
2016-11-01
Using an in-house computational framework, we have studied the interaction of water waves with pitching flap-type ocean wave energy converters (WECs). The computational framework solves the full 3D Navier-Stokes equations and captures important effects, including the fluid-solid interaction, the nonlinear and viscous effects. The results of the computational tool, is first compared against the experimental data on the response of a flap-type WEC in a wave tank, and excellent agreement is demonstrated. Further simulations at the model and prototype scales are presented to assess the validity of the Froude scaling. The simulations are used to address some important questions, such as the validity range of common WEC modeling approaches that rely heavily on the Froude scaling and the inviscid potential flow theory. Additionally, the simulations examine the role of the Keulegan-Carpenter (KC) number, which is often used as a measure of relative importance of viscous drag on bodies exposed to oscillating flows. The performance of the flap-type WECs is investigated at various KC numbers to establish the relationship between the viscous drag and KC number for such geometry. That is of significant importance because such relationship only exists for simple geometries, e.g., a cylinder. Support from the National Science Foundation is gratefully acknowledged.
Derakhti, Morteza; Kirby, James T.; Shi, Fengyan; Ma, Gangfeng
2016-11-01
We examine wave-breaking predictions ranging from shallow- to deep-water conditions using a non-hydrostatic σ-coordinate RANS model NHWAVE as described in Derakhti et al. (2016a), comparing results both with corresponding experiments and with the results of a volume-of-fluid (VOF)/Navier-Stokes solver (Ma et al., 2011; Derakhti and Kirby, 2014a,b). Our study includes regular and irregular depth-limited breaking waves on planar and barred beaches as well as steepness-limited unsteady breaking focused wave packets in intermediate and deep water. In Part 1 of this paper, it is shown that the model resolves organized wave motions in terms of free-surface evolution, spectral evolution, organized wave velocity evolution and wave statistics, using a few vertical σ-levels. In addition, the relative contribution of modeled physical dissipation and numerical dissipation to the integral breaking-induced wave energy loss is discussed. In steepness-limited unsteady breaking focused wave packets, the turbulence model has not been triggered, and all the dissipation is imposed indirectly by the numerical scheme. Although the total wave-breaking-induced energy dissipation is underestimated in the unsteady wave packets, the model is capable of predicting the dispersive and nonlinear properties of different wave packet components before and after the break point, as well as the overall wave height decay and the evolution of organized wave velocity field and power spectrum density over the breaking region. In Part 2 (Derakhti et al., 2016b), model reproduction of wave-breaking-induced turbulence and mean circulation is examined in detail. The same equations and numerical methods are used for the various depth regimes, and no ad-hoc treatment, such as imposing hydrostatic conditions, is involved in triggering breaking. Vertical grid resolution in all simulated cases is at least an order of magnitude coarser than that of typical VOF-based simulations.
Institute of Scientific and Technical Information of China (English)
MA Song-Hua; JIANG Yong-Qing; FANG Jian-Ping
2008-01-01
With the help of the conditional similarity reduction method, some new exact solutions of the (2+1)-dimensional modified dispersive water-wave system (MDWW) are obtained. Based on the derived solution, we investigate the evolution of solitons in the background waves.
Observation of Mountain Lee Waves with MODIS NIR Column Water Vapor
Lyapustin, A.; Alexander, M. J.; Ott, L.; Molod, A.; Holben, B.; Susskind, J.; Wang, Y.
2014-01-01
Mountain lee waves have been previously observed in data from the Moderate Resolution Imaging Spectroradiometer (MODIS) "water vapor" 6.7 micrometers channel which has a typical peak sensitivity at 550 hPa in the free troposphere. This paper reports the first observation of mountain waves generated by the Appalachian Mountains in the MODIS total column water vapor (CWV) product derived from near-infrared (NIR) (0.94 micrometers) measurements, which indicate perturbations very close to the surface. The CWV waves are usually observed during spring and late fall or some summer days with low to moderate CWV (below is approx. 2 cm). The observed lee waves display wavelengths from3-4 to 15kmwith an amplitude of variation often comparable to is approx. 50-70% of the total CWV. Since the bulk of atmospheric water vapor is confined to the boundary layer, this indicates that the impact of thesewaves extends deep into the boundary layer, and these may be the lowest level signatures of mountain lee waves presently detected by remote sensing over the land.
Contact-line dynamics for water waves and high-Re flows
Jiang, Lei; Liu, Ziyuan; Perlin, Marc; Schultz, William W.
1997-11-01
An appropriate contact-line model at the gas/liquid/solid trijunction is critical to the prediction of both low-Re flows and high-Re flows such as occur with water waves. Contact-line condition for water waves was proposed by Hocking (1987) and later by Miles (1991) based on Navier's slip relation. However, Cocciaro et al. (1993) and Ting & Perlin (1995) showed that strongly nonlinear contact-line dynamics are present experimentally, and that these dynamics are more complex than Hocking and Miles' models. We present results on the frequency and damping of Faraday water waves in various wave tanks and under different wetting conditions. The surface-elevation decay is analyzed with a complex demodulation technique. Frequency detuning and contact-line damping are found to obey power laws in the wave amplitude. The power-law exponent depends on the wetting condition and the material of which the tank is constructed. A preliminary analysis suggests that an averaged contact-line condition similar to the Tanner's law gives the correct amplitude dependence in frequency and damping. This condition also agrees qualitatively with contact-line data from Ting & Perlin. Preliminary analysis of the boundary layer structure near a moving contact line is carried out in the large-Re limit. Influence of corner flow and some implications from the self-similar Falkner-Skan equation are presented. This research is supported by ONR and NASA Microgravity Fluid Physics Program.
Effects of Topography and Current on Horizontal Irrotational Waves in Shallow Water
Institute of Scientific and Technical Information of China (English)
孙明光; 高虎山
2000-01-01
Based on the Boussinesq assumption, derived are couple equations of free surface elevation and horizontal velocities for horizontal irrotational flow, and analytical expressions of the corresponding pressure and vertical velocity. After the free surface elevation and horizontal velocity at a certain depth are obtained by numerical method, the pressure and vertical velocity distributions can be obtained by simple calculation. The dispersion at different depths is the same at the O (ε) approximation. The wave amplitude will decrease with increasing time due to viscosity, but it will increase due to the matching of viscosity and the bed slope, thus. flow is unstable. Numerical or analytical results show that the wave amplitude, velocity and length will increase as the current increases along the wave direction, but the amplitude will increase, and the wave velocity and length will decrease as the water depth decreases.
Non-linear water waves generated by impulsive motion of submerged obstacle
Directory of Open Access Journals (Sweden)
N. I. Makarenko
2013-12-01
Full Text Available Fully nonlinear problem on unsteady water waves generated by impulsively moving obstacle is studied analytically. Our method involves the reduction of Euler equations to the integral-differential system for the wave elevation together with normal and tangential fluid velocities at the free surface. Exact model equations are derived in explicit form in the case when the isolated obstacle is presented by totally submerged elliptic cylinder. Small-time asymptotic solution is constructed for the cylinder which starts with constant acceleration from rest. It is demonstrated that the leading-order solution terms describe several wave regimes such as the formation of non-stationary splash jets by vertical rising or vertical submersion of the obstacle, as well as the generation of diverging waves is observed.
BEM Analysis of Wave Propagation in a Water-Filled Borehole in an Anisotropic Solid
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
This paper describes a time-domain boundary element method developed to analyze the interactions of acoustic and elastic waves near the interfaces between water and an anisotropic elastic solid. Two models are analyzed with one being the interface between two half spaces of fluid and solid and the other being a fluid region sandwiched by half space domains of anisotropic elastic solids. Both monopole and dipole point sources are used to generate an initial pressure wave in the fluid. Some snapshots of the transient wave behavior near the fluid-solid interfaces are given. The effect of the anisotropy in the solid on the pressure waveforms in the fluid is discussed. The numerical results allow detailed arrival identification and interpretation of acoustic and elastic waves propagating along the fluid-solid interfaces.
Instability of water jet: Aerodynamically induced acoustic and capillary waves
Broman, Göran I.; Rudenko, Oleg V.
2012-09-01
High-speed water jet cutting has important industrial applications. To further improve the cutting performance it is critical to understand the theory behind the onset of instability of the jet. In this paper, instability of a water jet flowing out from a nozzle into ambient air is studied. Capillary forces and compressibility of the liquid caused by gas bubbles are taken into account, since these factors have shown to be important in previous experimental studies. A new dispersion equation, generalizing the analogous Rayleigh equation, is derived. It is shown how instability develops because of aerodynamic forces that appear at the streamlining of an initial irregularity of the equilibrium shape of the cross-section of the jet and how instability increases with increased concentration of gas bubbles. It is also shown how resonance phenomena are responsible for strong instability. On the basis of the theoretical explanations given, conditions for stable operation are indicated.
A Unified Model for the Evolution of Nonlinear Water Waves.
1982-12-30
surface relation. Th re second identity in (2.3) is a simple (if not transparent) identity. -- . . .--- ~. -.. 7 A) PLAN VIEW B) SIDE VIEW C...ouantity is the- total- tarea i7-c-,e still water level; t-his comes frnm !mlt-inlying (2.0 b-y b an,; intperati’nq over the computational box: a [m bh
Stokes drift for inertial particles transported by water waves
Boffetta, G; Mazzino, A; Onorato, M; Santamaria, F
2012-01-01
We study the effect of surface gravity waves on the motion of inertial particles in an incompressible fluid. Using the multiple-scale technique, we perform an analytical calculation which allows us to predict the dynamics of such particles; results are shown for both the infinite- and finite-depth regimes. Numerical simulations based on the velocity field resulting from the second-order Stokes theory for the surface elevation have been performed, and an excellent agreement with the analytical predictions is observed. Such an agreement seems to hold even beyond the formal applicability of the theory. We find that the presence of inertia leads to a non-negligible correction to the well-known horizontal Stokes drift; moreover, we find that the vertical velocity is also affected by a drift. The latter result may have some relevant consequences on the rate of sedimentation of particles of finite size. We underline that such a drift would also be observed in the (hypothetical) absence of the gravitational force.
Water wave scattering by a nearly circular cylinder submerged beneath an ice-cover
Chakraborty, Rumpa; Mandal, Birendra Nath
2015-03-01
Assuming linear theory, the two-dimensional problem of water wave scattering by a horizontal nearly circular cylinder submerged in infinitely deep water with an ice cover modeled as a thin-elastic plate floating on water, is investigated here. The cross-section of the nearly circular cylinder is taken as r= a( 1+δC( θ)), where a is the radius of the corresponding circular cross-section of the cylinder, δ is a measure of small departure of the cross-section of the cylinder from its circularity and C( θ) is the shape function. Using a simplified perturbation technique the problem is reduced to two independent boundary value problems up to first order in δ. The first one corresponds to water wave scattering by a circular cylinder submerged in water with an ice-cover, while the second problem describes wave radiation by a submerged circular cylinder and involves first order correction to the reflection and transmission coefficients. The corrections are obtained in terms of integrals involving the shape function. Assuming a general Fourier expansion of the shape function, these corrections are evaluated approximately. It is well known that normally incident wave trains experience no reflection by a circular cylinder submerged in infinitely deep water with an ice cover. It is shown here that the reflection coefficient also vanishes up to first order for some particular choice of the shape function representing a nearly circular cylinder. For these cases, full transmission occurs, only change is in its phase which is depicted graphically against the wave number in a number of figures and appropriate conclusions are drawn.
Water Wave Scattering by a Nearly Circular Cylinder Submerged Beneath an Ice-cover
Institute of Scientific and Technical Information of China (English)
Rumpa Chakraborty; Birendra Nath Mandal
2015-01-01
Assuming linear theory, the two-dimensional problem of water wave scattering by a horizontal nearly circular cylinder submerged in infinitely deep water with an ice cover modeled as a thin-elastic plate floating on water, is investigated here. The cross-section of the nearly circular cylinder is taken as r=a(1+δC(θ)), wherea is the radius of the corresponding circular cross-section of the cylinder,δ is a measure of small departure of the cross-section of the cylinder from its circularity andC(θ) is the shape function. Using a simplified perturbation technique the problem is reduced to two independent boundary value problems up to first order inδ. The first one corresponds to water wave scattering by a circular cylinder submerged in water with an ice-cover, while the second problem describes wave radiation by a submerged circular cylinder and involves first order correction to the reflection and transmission coefficients. The corrections are obtained in terms of integrals involving the shape function. Assuming a general Fourier expansion of the shape function, these corrections are evaluated approximately. It is well known that normally incident wave trains experience no reflection by a circular cylinder submerged in infinitely deep water with an ice cover. It is shown here that the reflection coefficient also vanishes up to first order for some particular choice of the shape function representing a nearly circular cylinder. For these cases, full transmission occurs, only change is in its phase which is depicted graphically against the wave number in a number of figures and appropriate conclusions are drawn.
Stability of steady rotational water-waves of finite amplitude on arbitrary shear currents
Seez, William; Abid, Malek; Kharif, Christian
2016-04-01
A versatile solver for the two-dimensional Euler equations with an unknown free-surface has been developed. This code offers the possibility to calculate two-dimensional, steady rotational water-waves of finite amplitude on an arbitrary shear current. Written in PYTHON the code incorporates both pseudo-spectral and finite-difference methods in the discretisation of the equations and thus allows the user to capture waves with large steepnesses. As such it has been possible to establish that, in a counter-flowing situation, the existence of wave solutions is not guaranteed and depends on a pair of parameters representing mass flux and vorticity. This result was predicted, for linear solutions, by Constantin. Furthermore, experimental comparisons, both with and without vorticity, have proven the precision of this code. Finally, waves propagating on top of highly realistic shear currents (exponential profiles under the surface) have been calculated following current profiles such as those used by Nwogu. In addition, a stability analysis routine has been developed to study the stability regimes of base waves calculated with the two-dimensional code. This linear stability analysis is based on three dimensional perturbations of the steady situation which lead to a generalised eigenvalue problem. Common instabilities of the first and second class have been detected, while a third class of wave-instability appears due to the presence of strong vorticity. {1} Adrian Constantin and Walter Strauss. {Exact steady periodic water waves with vorticity}. Communications on Pure and Applied Mathematics, 57(4):481-527, April 2004. Okey G. Nwogu. {Interaction of finite-amplitude waves with vertically sheared current fields}. Journal of Fluid Mechanics, 627:179, May 2009.
Institute of Scientific and Technical Information of China (English)
Hu Huang; Jia Fu
2006-01-01
A fully three-dimensional surface gravitycapillary short-crested wave system is studied as two progressive wave-trains of equal amplitude and frequency, which are collinear with uniform currents and doubly-periodic in the horizontal plane, are propagating at an angle to each other. The first-and second-order asymptotic analytical solutions of the short-crested wave system are obtained via a perturbation expansion in a small parameter associated with the wave steepness, therefore depicting a series of typical three-dimensional wave patterns involving currents, shallow and deep water, and surface capillary waves, and comparing them with each other.
Interfacial wave behavior in oil-water channel flows: Prospects for a general understanding
Energy Technology Data Exchange (ETDEWEB)
McCready, M.J.; Uphold, D.D.; Gifford, K.A. [Univ. of Notre Dame, IN (United States)
1997-12-31
Oil-water pressure driven channel flow is examined as a model for general two-layer flows where interfacial disturbances are important. The goal is to develop sufficient understanding of this system so that the utility and limitations of linear and nonlinear theories can be known a priori. Experiments show that sometimes linear stability is useful at predicting the steady or dominant evolving waves. However in other situations there is no agreement between the linearly fastest growing wave and the spectral peak. An interesting preliminary result is that the bifurcation to interfacial waves is supercritical for all conditions that were studied for an oil-water channel flow, gas-liquid channel flow and two-liquid Couette flow. However, three different mechanisms are dominant for each of these three situations.
Nonpropagating Solitons in (2+1)-Dimensional Dispersive Long-Water Wave System
Institute of Scientific and Technical Information of China (English)
FANG Jian-Ping; ZHENG Chun-Long; LIU Qing
2005-01-01
With the help of an extended mapping approach, a new type of variable separation excitation with three arbitrary functions of the (2+1)-dimensional dispersive long-water wave system (DLW) is derived. Based on the derived variable separation excitation, abundant non-propagating solitons such as dromion, ring, peakon, and compacton etc.are revealed by selecting appropriate functions in this paper.
An Improved Time Domain Procedure For Separating Incident And Reflected Water Waves
DEFF Research Database (Denmark)
Burcharth, Hans Falk; Matsumoto, A.; Tayasu, M.;
2002-01-01
Impulse responses of digital filters for use in separating incident and reflected water waves in a time domain are improved by using a nonlinear least square formulation. The applicability and limitations of the method are discussed. Trial computations using a set of analytical examples with know...
Generalized Variational Principle for Long Water-Wave Equation by He's Semi-Inverse Method
Directory of Open Access Journals (Sweden)
Weimin Zhang
2009-01-01
Full Text Available Variational principles for nonlinear partial differential equations have come to play an important role in mathematics and physics. However, it is well known that not every nonlinear partial differential equation admits a variational formula. In this paper, He's semi-inverse method is used to construct a family of variational principles for the long water-wave problem.
A variational approach to Boussinesq modelling of fully nonlinear water waves
Klopman, Gert; Groesen, van Brenny; Dingemans, Maarten W.
2010-01-01
In this paper we present a new method to derive Boussinesq-type equations from a variational principle. These equations are valid for nonlinear surface-water waves propagating over bathymetry. The vertical structure of the flow, required in the Hamiltonian, is approximated by a (series of) vertical
THE WAVE INTERACTION OF HEAVY BREAKS IN THE WATER WITH ELASTIC BARRIER
Directory of Open Access Journals (Sweden)
Ivanchenko G.M.
2014-06-01
Full Text Available Transformation of underwater shock wave spherical front geometry and chauge of impulse carried by it at interaction witu elastic shield is numerically investigated witu the use of zero approximation of ray technique. It is established, that in the vicinity of spots of total internal reflection in the plane interface between water and elastic body the additional internal stresses tend to infinity.
Air bubbles in water: a strongly multiple scattering medium for acoustic waves.
Kafesaki, M; Penciu, R S; Economou, E N
2000-06-26
Using a newly developed multiple scattering scheme, we calculate band structure and transmission properties for acoustic waves propagating in bubbly water. We prove that the multiple scattering effects are responsible for the creation of wide gaps in the transmission even in the presence of strong positional and size disorder.
Numerical Analysis of Effect of Water on Explosive Wave Propagation in Tunnels and Surrounding Rock
Institute of Scientific and Technical Information of China (English)
XIA Chang-jing; SONG Zhen-duo; TIAN Lu-lu; LIU Hong-bin; WANG Lu; WU Xiao-fang
2007-01-01
Based on the application of practical engineering, propagation processes of explosive waves in rock with water well and tunnel are simulated by ANSYS/LS-DYNA software. The evolution of damage in rock is presented. The effect of water on the damage of the concrete slab in a tunnel is compared with damage inflicted without water. The numerical simulation illustrates that water plays an important role in the evolution of damage of the concrete slab in a mine tunnel. In the presence of water in the rock the concrete slab is damaged more severely than without water in rock. The effect of water location in the rock is also considered. It is found that the concrete slab in the tunnel shows various degrees of damage as a function of the different locations of water. Attenuation laws of stress waves over time-space in rock with water are also obtained. Numerical results indicate that, under blast loading, there are three zones in the rock: a crushed zone nearby the explosive charge, a damaged zone and an elastic zone. The conclusions of numerical analysis may provide references for blasting designs and structure protection.
Institute of Scientific and Technical Information of China (English)
Deng Qilin; Zhang Lei; Zhou Jinjin
2004-01-01
Filth adhering to metal pipes can be cleaned by shock wave generated by electrical discharge under water. The mechanism of shock wave effect of electrical discharge under water on filth cleaning is analyzed by building a mechanical model. A metal pipe coated with cement to simulate real filth is cleaned by using electrical discharge under water. The experimental results confirm the mechanical analysis and also show the technology of electrical discharge under water is an very effective method for filth cleaning.
Atmospheric Water Vapor: A Nemesis for Millimeter Wave Propagation
1980-01-01
Sulphur dioxide, for example, nucleates with water vapor to form sulfuric acid primary particles in large numbers (as high as 1015 m- 3 ), which are...electro- polished stainless steel (SS 304) cavity (3440 cm3 and 1265 cm2 , S/V = 0.37 cm-1 ) evacuated for > 24 hours to 10-4 torr and subjected to... electropolished -1.50 30 150 400 HMDSa silanizing -1.35 27 190 750 Parylene C (Union Carbine) -1.60 32 140 580 Silicone SR240 (GE) -2.10 42 200 550 Teflon REPI20
Emergence of coherent wave groups in deep-water random sea.
Viotti, C; Dutykh, D; Dudley, J M; Dias, F
2013-06-01
Extreme surface waves in a deep-water long-crested sea are often interpreted as a manifestation in the real world of the so-called breathing solitons of the focusing nonlinear Schrödinger equation. While the spontaneous emergence of such coherent structures from nonlinear wave dynamics was demonstrated to take place in fiber-optics systems, the same point remains far more controversial in the hydrodynamic case. With the aim to shed further light on this matter, the emergence of breatherlike coherent wave groups in a long-crested random sea is investigated here by means of high-resolution spectral simulations of the fully nonlinear two-dimensional Euler equations. The primary focus of our study is to parametrize the structure of random wave fields with respect to the Benjamin-Feir index, which is a nondimensional measure of the energy localization in Fourier space. This choice is motivated by previous results, showing that extreme-wave activity in a long-crested sea is highly sensitive to such a parameter, which is varied here by changing both the characteristic spectral bandwidth and the average wave steepness. It is found that coherent wave groups, closely matching realizations of Kuznetsov-Ma breathers in Euler dynamics, develop within wave fields characterized by sufficiently narrow-banded spectra. The characteristic spatial and temporal scales of wave group dynamics, and the corresponding occurrence of extreme events, are quantified and discussed by means of space-time autocorrelations of the surface elevation envelope and extreme-event statistics.
Electromagnetic aquametry electromagnetic wave interaction with water and moist substances
Kupfer, Klaus
2006-01-01
This book covers all aspects of Electromagnetic Aquametry. It summarizes the wide area of metrology and its applications in electromagnetic sensing of moist materials. The physical properties of water in various degrees of binding interacting with electromagnetic fields is presented by model systems. The book describes measurement methods and sensors in the frequency domain, TDR-techniques for environmental problems, methods and sensors for quality assessment of biological substances, and nuclear magnetic resonance techniques. Environmental sciences, as well as civil and geoengineering, fossil fuels, food and pharmaceutical science are the main fields of application. A very wide frequency sprectrum is used for dielectric measurement methods, but the microwave range is clearly dominant. Multiparameter methods as well as methods of principal components and artificial neural networks for density independent measurements are described.
Cheriton, Olivia M.; Storlazzi, Curt D.; Rosenberger, Kurt J.
2016-05-01
Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04-0.004 Hz) and very low frequency (0.004-0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.
Cheriton, Olivia; Storlazzi, Curt; Rosenberger, Kurt
2016-01-01
Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04–0.004 Hz) and very low frequency (0.004–0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.
Wave-current interactions in deep water conditions: field measurements and analyses
Rougier, Gilles; Rey, Vincent; Molcard, Anne
2015-04-01
The study of wave - current interaction has drawn interest in oceanography, ocean engineering, maritime navigation and for tides or waves power device design. In the context of the hydrodynamics study along the French Mediterranean coast, a current profiler was deployed near Toulon at the south of the "Port Cros" island. This coastal zone is characterized by a steep slope, the water depth varying from tens meters to several thousand meters over few kilometers from the coast. An ambient current, the "Northern Current", coming from the Ligurian sea (area of Genoa, Italy) and following the coast up to Toulon, is present all over the year. Its mean surface velocity is of about 0.30 m/s, its flow rate of about 1.5 Sv. The region is exposed to two dominating winds: the Mistral, coming from North-West, and Eastern winds. Both generate swell and/or wind waves in either following or opposing current conditions with respect to the Northern Current. A current profiler equipped with a wave tracking system (ACPD workhorse from RDI) was deployed from July to October 2014 in deep water conditions (depth of about 500m). The mooring system allowed the ADCP to measure the current profile from the sea surface down to 25m depth, which corresponds more or less to the depth of influence of waves of periods up to 10s. The collected data include energetic wave conditions in either following or opposing current conditions. The current intensity and its vertical profiles have shown a significant temporal variability according to the meteorological conditions. Effects of the wave conditions on the current properties are discussed. ACKNOWLEDGEMENTS This work was supported by the program BOMBYX and the ANR grant No ANR-13-ASTR-0007.
Chen, Jun; Yang, Jin; Li, Zhaoling; Fan, Xing; Zi, Yunlong; Jing, Qingshen; Guo, Hengyu; Wen, Zhen; Pradel, Ken C; Niu, Simiao; Wang, Zhong Lin
2015-03-24
With 70% of the earth's surface covered with water, wave energy is abundant and has the potential to be one of the most environmentally benign forms of electric energy. However, owing to lack of effective technology, water wave energy harvesting is almost unexplored as an energy source. Here, we report a network design made of triboelectric nanogenerators (TENGs) for large-scale harvesting of kinetic water energy. Relying on surface charging effect between the conventional polymers and very thin layer of metal as electrodes for each TENG, the TENG networks (TENG-NW) that naturally float on the water surface convert the slow, random, and high-force oscillatory wave energy into electricity. On the basis of the measured output of a single TENG, the TENG-NW is expected to give an average power output of 1.15 MW from 1 km(2) surface area. Given the compelling features, such as being lightweight, extremely cost-effective, environmentally friendly, easily implemented, and capable of floating on the water surface, the TENG-NW renders an innovative and effective approach toward large-scale blue energy harvesting from the ocean.
Water-waves on linear shear currents. A comparison of experimental and numerical results.
Simon, Bruno; Seez, William; Touboul, Julien; Rey, Vincent; Abid, Malek; Kharif, Christian
2016-04-01
Propagation of water waves can be described for uniformly sheared current conditions. Indeed, some mathematical simplifications remain applicable in the study of waves whether there is no current or a linearly sheared current. However, the widespread use of mathematical wave theories including shear has rarely been backed by experimental studies of such flows. New experimental and numerical methods were both recently developed to study wave current interactions for constant vorticity. On one hand, the numerical code can simulate, in two dimensions, arbitrary non-linear waves. On the other hand, the experimental methods can be used to generate waves with various shear conditions. Taking advantage of the simplicity of the experimental protocol and versatility of the numerical code, comparisons between experimental and numerical data are discussed and compared with linear theory for validation of the methods. ACKNOWLEDGEMENTS The DGA (Direction Générale de l'Armement, France) is acknowledged for its financial support through the ANR grant N° ANR-13-ASTR-0007.
Evolution of stationary wave patterns in mesospheric water vapor due to climate change
Demirhan Barı, Deniz; Gabriel, Axel; Sezginer Ünal, Yurdanur
2016-07-01
The variability in the observed stationary wave patterns of the mesospheric water vapor (H2O) is investigated using CMIP5 RCP 4.5 and RCP 8.5 projections. The change in the vertical and meridional wave structure at northern mid- and polar latitudes associated to the zonal and meridional eddy heat fluxes is discussed by analyzing the advection of H2O due to residual wind components. The alteration in the characteristics of the stationary wave-1 pattern of the lower mesospheric H2O (up to about 75km) related to change in the projected radiative forcing is observed for the years from 2006 to 2100. Additionally the remarkable effect of the increase in global temperature on the zonal asymmetries in small-scale transient waves and parameterized gravity waves, which largely contribute to the observed stationary wave patterns of H2O in the upper mesosphere, is analyzed. For validation purposes, the derived stratospheric patterns are verified against the eddy heat fluxes and residual advection terms derived from Aura/MLS satellite data between 2004-2010 and the reference period of the CMIP5 MPI dataset (1976-2005) providing confidence in the applied method.
Flow, waves and water exchange in the Suur Strait, Gulf of Riga, in 2008:
Directory of Open Access Journals (Sweden)
Tarmo Kõuts
2011-03-01
Full Text Available Wind, flow and wave measurements were performed in November-December in 2008 in the relatively narrowand shallow Suur Strait connecting the waters of the Väinameri and the Gulf of Riga.During the measurement period wind conditions were extremely variable, including a severe storm on 23 November. The flow speedalong the strait varied between ±0.2 m s-1, except for the 0.4 m s-1 that occurred after the storm as a result of the sealevel gradient. The mean and maximum significant wave heights were 0.53 m and 1.6 m respectively. Because of their longer fetch, southerlywinds generated higher waves in the strait than winds from the north. All wave events caused by the stronger southerly windsinduced sediment resuspension, whereas the current-induced shear velocity slightly exceeded the critical value for resuspensiononly when the current speed was 0.4 m s-1. A triple-nested two-dimensional high resolution (100 m in the Suur Strait circulation model and the SWANwave model were used to simulate water exchange in 2008 and the wave-induced shear velocity field in the Suur Strait respectively. Circulation model simulations demonstrated that water exchange was highly variable, that cumulative transport followed an evident seasonal cycle, and that there was an grossannual outflow of 23 km3 from the Gulf of Riga. The horizontal distribution of wave-induced shear velocityduring the strong southerly wind event indicated large shear velocities and substantial horizontal variability. The shearvelocities were less than the critical value for resuspension in the deep area of the Suur Strait.
An efficient flexible-order model for coastal and ocean water waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Bingham, Harry B.; Lindberg, Ole
of structures. The mathemathical equations for potential waves in the physical domain is transformed through $\\sigma$-mapping(s) to a time-invariant boundary-fitted domain which then becomes a basis for an efficient solution strategy. The improved 3D numerical model is based on a finite difference method......Current work are directed toward the development of an improved numerical 3D model for fully nonlinear potential water waves over arbitrary depths. The model is high-order accurate, robust and efficient for large-scale problems, and support will be included for flexibility in the description...... properties of the numerical model together with the latests achievements....
A nanowire based triboelectric nanogenerator for harvesting water wave energy and its applications
Directory of Open Access Journals (Sweden)
Xiaoyi Li
2017-07-01
Full Text Available The ocean wave energy is one of the most promising renewable and clean energy sources for human life, which is the so-called “Blue energy.” In this work, a nanowire based triboelectric nanogenerator was designed for harvesting wave energy. The nanowires on the surface of FEP largely raise the contacting area with water and also make the polymer film hydrophobic. The output can reach 10 μ A and 200 V. When combined with a capacitor, an infrared emitter, and a receiver, a self-powered wireless infrared system is fabricated, which can be used in the fields of communication and detecting.
A nanowire based triboelectric nanogenerator for harvesting water wave energy and its applications
Li, Xiaoyi; Tao, Juan; Zhu, Jing; Pan, Caofeng
2017-07-01
The ocean wave energy is one of the most promising renewable and clean energy sources for human life, which is the so-called "Blue energy." In this work, a nanowire based triboelectric nanogenerator was designed for harvesting wave energy. The nanowires on the surface of FEP largely raise the contacting area with water and also make the polymer film hydrophobic. The output can reach 10 μ A and 200 V. When combined with a capacitor, an infrared emitter, and a receiver, a self-powered wireless infrared system is fabricated, which can be used in the fields of communication and detecting.
DEFF Research Database (Denmark)
Ibsen, Lars Bo
2008-01-01
Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many t...
Internal waves and surf zone water quality at Huntington Beach, California
Wong, H.; Santoro, A.; Nidzieko, N. J.; Hench, J. L.; Boehm, A. B.
2011-12-01
This study characterized diurnal, semi-diurnal, and high-frequency internal wave field at Huntington Beach, California, USA and the connection between internal waves and surf zone water quality. An array of oceanographic moorings was deployed in the summer of 2005 and 2006 at 10-20 meter depths offshore of the beach to observe internal waves and cross-shore exchange. Concurrently, surf zone water quality was assessed twice daily at an adjacent station (Huntington State Beach) with measurements of phosphate, dissolved inorganic nitrogen, silicate, chlorophyll a, fecal indicator bacteria, and the human-specific fecal DNA marker in Bacteroidales. Spectral analysis of water temperature shows well-defined spectral peaks at diurnal and semi-diurnal frequencies. Complex Empirical Orthogonal Function analysis of observed currents reveals that the baroclinic component (summation of second to fifth principal components) accounted for 30% of the total variance in the currents in both years, indicating the importance of density-driven flow during the summer when the water column was stratified. The major axis of the first principal component was oriented alongshore, whereas that of the second and third principal components made an angle of 25 to 55 degree with the cross-shore direction. Arrival of cold subthermocline water in the very near shore (within 1 km of the surf zone) was characterized by strong onshore flow near the bottom of the water column. The near bottom, baroclinic, cross-shore current was significantly lag-correlated with the near bottom temperature data along a cross-shore transect towards shore, indicative of shoreward transport of cold subthermocline water. Wavelet analysis of temperature data showed that non-stationary temperature fluctuations were correlated with buoyancy frequency and the near bottom cross-shore baroclinic current. During periods of large temperature fluctuations, the majority of the variance was within the semi-diurnal band; however, the
Common-optical axis Fourier transform profilometry for water surface waves
Ghadiri, Mahdi; Krechetnikov, Rouslan
2016-11-01
The Fourier transform profilometry - a single-shot optical profilometric measurement of surface deformation - has been widely used to visualize and measure water surface waves. This well-known method is based on an optical system composed of a video projector displaying a fringe pattern on the surface and a camera recording this pattern as the reference image. The deformed fringe pattern following deformation of the surface later is then recorded and compared to the reference image in order to produce a phase map, from which the height of the deformed surface is reconstructed through a phase-to-height relation. The biggest challenge encountered while applying this method for water surface is the light reflection which previously has been partially treated by enhancing the water light diffusivity with the addition of Titanium dioxide. As part of the effort to improve the accuracy and practical applicability of the method, in this talk we will present a new implementation of a common-optical axis geometry along with an appropriate phase-height relation. Furthermore, in the case of water surface waves, we introduce a proper light filtration, which removes all the reflections remaining after addition of Titanium dioxide. The proposed technique provides an order of magnitude improvement in the accuracy of detecting and reconstructing the surface deformation, which is crucial for studying small amplitude waves and bifurcation phenomena.
A Fast GPU-accelerated Mixed-precision Strategy for Fully NonlinearWater Wave Computations
DEFF Research Database (Denmark)
Glimberg, Stefan Lemvig; Engsig-Karup, Allan Peter; Madsen, Morten G.
2011-01-01
We present performance results of a mixed-precision strategy developed to improve a recently developed massively parallel GPU-accelerated tool for fast and scalable simulation of unsteady fully nonlinear free surface water waves over uneven depths (Engsig-Karup et.al. 2011). The underlying wave...... model is based on a potential flow formulation, which requires efficient solution of a Laplace problem at large-scales. We report recent results on a new mixed-precision strategy for efficient iterative high-order accurate and scalable solution of the Laplace problem using a multigrid......-preconditioned defect correction method. The improved strategy improves the performance by exploiting architectural features of modern GPUs for mixed precision computations and is tested in a recently developed generic library for fast prototyping of PDE solvers. The new wave tool is applicable to solve and analyze...
Short-crested waves in deep water: a numerical investigation of recent laboratory experiments
DEFF Research Database (Denmark)
Fuhrman, David R.; Madsen, Per A.
2006-01-01
A numerical study of quasi-steady, doubly-periodic monochromatic short-crested wave patterns in deep water is conducted using a high-order Boussinesq-type model. Simulations using linear wavemaker conditions in the nonlinear model are initially used to approximate conditions from recent laboratory...... experiments. The computed patterns share many features with those observed in wavetanks, including bending (both frontwards and backwards) of the wave crests, dipping at the crest centerlines, and a pronounced long modulation in the direction of propagation. A new and simple explanation for these features...... is provided, involving the release of spurious free first harmonics, due to the neglect of steady third-order components in the three-dimensional wave generation. A comparison with the experimentally observed beat length and amplitude matches the theoretical/numerical predictions well. Additionally, direct...
Submillimeter Wave Astronomy Satellite Observations of Extended Water Emission in Orion
Snell, R L; Ashby, M L N; Bergin, E A; Chin, G; Erickson, N R; Goldsmith, P F; Harwit, M; Kleiner, S C; Koch, D G; Neufeld, D A; Patten, B M; Plume, R; Schieder, R; Stauffer, J R; Tolls, V; Wang, Z; Winnewisser, G; Zhang, Y F; Melnick, G J
2000-01-01
We have used the Submillimeter Wave Astronomy Satellite to map the ground-state 1_{10}-1_{01} transition of ortho-water at 557 GHz in the Orion molecular cloud. Water emission was detected in Orion over an angular extent of about 20 arcmin, or nearly 3 pc. The water emission is relatively weak, with line widths (3-6 km s^{-1}) and V_{LSR} velocities (9-11 km s^{-1}) consistent with an origin in the cold gas of the molecular ridge. We find that the ortho-water abundance relative to H_2 in the extended gas in Orion varies between 1 and 8x10^{-8}, with an average of 3x10^{-8}. The absence of detectable narrow-line ortho-H_2^{18}O emission is used to set a 3-sigma upper limit on the relative ortho-water abundance of 7x10^{-8}.
The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor
Directory of Open Access Journals (Sweden)
S. Dhomse
2008-02-01
Full Text Available Using water vapor data from HALOE and SAGE II, an anti-correlation between planetary wave driving (here expressed by the mid-latitude eddy heat flux at 50 hPa added from both hemispheres and tropical lower stratospheric (TLS water vapor has been obtained. This appears to be a manifestation of the inter-annual variability of the Brewer-Dobson (BD circulation strength (the driving of which is generally measured in terms of the mid-latitude eddy heat flux, and hence amount of water vapor entering the stratosphere. Some years such as 1991 and 1997 show, however, a clear departure from the anti-correlation which suggests that the water vapor changes in TLS can not be attributed solely to changes in extratropical planetary wave activity (and its effect on the BD circulation. After 2000 a sudden decrease in lower stratospheric water vapor has been reported in earlier studies based upon satellite data from HALOE, SAGE II and POAM III indicating that the lower stratosphere has become drier since then. This is consistent with a sudden rise in the combined mid-latitude eddy heat flux with nearly equal contribution from both hemispheres as shown here and with the increase in tropical upwelling and decrease in cold point temperatures found by Randel et al. (2006. The low water vapor and enhanced planetary wave activity (in turn strength of the BD circulation has persisted until the end of the satellite data records. From a multi-variate regression analysis applied to 27 years of NCEP and HadAT2 (radiosonde temperatures (up to 2005 with contributions from solar cycle, stratospheric aerosols and QBO removed, the enhancement wave driving after 2000 is estimated to contribute up to 0.7 K cooling to the overall TLS temperature change during the period 2001–2005 when compared to the period 1996–2000. NCEP cold point temperature show an average decrease of nearly 0.4 K from changes in the wave driving, which is consistent with observed mean TLS water vapor
Internal wave generation by convection in water. Part 2. Numerical simulations
Lecoanet, Daniel; Burns, Keaton J; Vasil, Geoffrey M; Brown, Benjamin P; Quataert, Eliot; Oishi, Jeffrey S
2014-01-01
Water's density maximum at 4C makes it well suited to study internal gravity wave excitation by convection: an increasing temperature profile is unstable to convection below 4C, but stably stratified above 4C. We present numerical simulations of water near its density maximum in a two dimensional tank, similar to the experiment described in a companion paper (Le Bars et al. 2015). The simulations agree very well with the experiments, despite differences in lateral boundary conditions in the two systems. We successfully model the damping of waves in the simulations using linear theory, provided we do not take the weak damping limit typically used in the literature. In order to isolate the physical mechanism exciting internal waves, we use the novel spectral code Dedalus to run several simulations of the simulation. We use data from the full simulation as source terms in two simplified models of internal wave excitation by convection: bulk excitation by convective Reynolds stresses, and interface forcing via th...
Mathematical Modeling of Oscillating Water Columns Wave-Structure Interaction in Ocean Energy Plants
Directory of Open Access Journals (Sweden)
Aitor J. Garrido
2015-01-01
Full Text Available Oscillating Water Column (OWC-based power take-off systems are one of the potential solutions to the current energy problems arising from the use of nuclear fission and the consumption of fossil fuels. This kind of energy converter turns wave energy into electric power by means of three different stages: firstly wave energy is transformed into pneumatic energy in the OWC chamber, and then a turbine turns it into mechanical energy and finally the turbogenerator module attached to the turbine creates electric power from the rotational mechanical energy. To date, capture chambers have been the least studied part. In this context, this paper presents an analytical model describing the dynamic behavior of the capture chamber, encompassing the wave motion and its interaction with the OWC structure and turbogenerator module. The model is tested for the case of the Mutriku wave power plant by means of experimental results. For this purpose, representative case studies are selected from wave and pressure drop input-output data. The results show an excellent matching rate between the values predicted by the model and the experimental measured data with a small bounded error in all cases, so that the validity of the proposed model is proven.
Numerical analysis of regular waves over an onshore oscillating water column
Energy Technology Data Exchange (ETDEWEB)
Davyt, D.P.; Teixeira, P.R.F. [Universidade Federal do Rio Grande (FURG), RS (Brazil)], E-mail: pauloteixeira@furg.br; Ramalhais, R. [Universidade Nova de Lisboa, Caparica (Portugal). Fac. de Ciencias e Tecnologia; Didier, E. [Laboratorio Nacional de Engenharia Civil, Lisboa (Portugal)], E-mail: edidier@lnec.pt
2010-07-01
The potential of wave energy along coastal areas is a particularly attractive option in regions of high latitude, such as the coasts of northern Europe, North America, New Zealand, Chile and Argentina where high densities of annual average wave energy are found (typically between 40 and 100 kW/m of wave front). Power estimated in the south of Brazil is 30kW/m, creating a possible alternative of source energy in the region. There are many types and designs of equipment to capture energy from waves under analysis, such as the oscillating water column type (OWC) which has been one of the first to be developed and installed at sea. Despite being one of the most analyzed wave energy converter devices, there are few case studies using numerical simulation. In this context, the numerical analysis of regular waves over an onshore OWC is the main objective of this paper. The numerical models FLUINCO and FLUENT are used for achieving this goal. The FLUINCO model is based on RANS equations which are discretized using the two-step semi-implicit Taylor-Galerkin method. An arbitrary Lagrangian Eulerian formulation is used to enable the solution of problems involving free surface movements. The FLUENT code (version 6.3.26) is based on the finite volume method to solve RANS equations. Volume of Fluid method (VOF) is used for modeling free surface flows. Time integration is achieved by a second order implicit scheme, momentum equations are discretized using MUSCL scheme and HRIC (High Resolution Interface Capturing) scheme is used for convective term of VOF transport equation. The case study consists of a 10.m deep channel with a 10 m wide chamber at its end. One meter high waves with different periods are simulated. Comparisons between FLUINCO and FLUENT results are presented. Free surface elevation inside the chamber; velocity distribution and streamlines; amplification factor (relation between wave height inside the chamber and incident wave height); phase angle (angular
Effects of sonication radiation on oil recovery by ultrasonic waves stimulated water-flooding.
Mohammadian, Erfan; Junin, Radzuan; Rahmani, Omeid; Idris, Ahmad Kamal
2013-02-01
Due to partial understanding of mechanisms involved in application of ultrasonic waves as enhanced oil recovery method, series of straight (normal), and ultrasonic stimulated water-flooding experiments were conducted on a long unconsolidated sand pack using ultrasonic transducers. Kerosene, vaseline, and SAE-10 (engine oil) were used as non-wet phase in the system. In addition, a series of fluid flow and temperature rise experiments were conducted using ultrasonic bath in order to enhance the understanding about contributing mechanisms. 3-16% increase in the recovery of water-flooding was observed. Emulsification, viscosity reduction, and cavitation were identified as contributing mechanisms. The findings of this study are expected to increase the insight to involving mechanisms which lead to improving the recovery of oil as a result of application of ultrasound waves.
Scattering of oblique surface water waves by thin vertical barrier over undulating bed topography
Choudhary, A.; Martha, S. C.
2017-06-01
The present study deals with the scattering of oblique surface water waves by small undulation on the bottom in the presence of a thin vertical barrier. Here, three different configurations of vertical barriers are investigated. Perturbation analysis is employed to determine the physical quantities, namely, the reflection and transmission coefficients. In this analysis, many different Boundary Value Problems (BVPs) are obtained out of which the first two bvps are considered. The zeroth order bvp is solved with the aid of eigenfunction expansion method. The first order reflection and transmission coefficients are derived in terms of the integrals by the method of the Green's integral theorem. The variation of these coefficients is plotted and analyzed for different physical parameters. Furthermore, the energy balance relation, an important relation in the study of water wave scattering, is derived and checked for assuring the correctness of the numerical results for the present problem.
Mechanical balance laws for fully nonlinear and weakly dispersive water waves
Kalisch, Henrik; Khorsand, Zahra; Mitsotakis, Dimitrios
2016-10-01
The Serre-Green-Naghdi system is a coupled, fully nonlinear system of dispersive evolution equations which approximates the full water wave problem. The system is known to describe accurately the wave motion at the surface of an incompressible inviscid fluid in the case when the fluid flow is irrotational and two-dimensional. The system is an extension of the well known shallow-water system to the situation where the waves are long, but not so long that dispersive effects can be neglected. In the current work, the focus is on deriving mass, momentum and energy densities and fluxes associated with the Serre-Green-Naghdi system. These quantities arise from imposing balance equations of the same asymptotic order as the evolution equations. In the case of an even bed, the conservation equations are satisfied exactly by the solutions of the Serre-Green-Naghdi system. The case of variable bathymetry is more complicated, with mass and momentum conservation satisfied exactly, and energy conservation satisfied only in a global sense. In all cases, the quantities found here reduce correctly to the corresponding counterparts in both the Boussinesq and the shallow-water scaling. One consequence of the present analysis is that the energy loss appearing in the shallow-water theory of undular bores is fully compensated by the emergence of oscillations behind the bore front. The situation is analyzed numerically by approximating solutions of the Serre-Green-Naghdi equations using a finite-element discretization coupled with an adaptive Runge-Kutta time integration scheme, and it is found that the energy is indeed conserved nearly to machine precision. As a second application, the shoaling of solitary waves on a plane beach is analyzed. It appears that the Serre-Green-Naghdi equations are capable of predicting both the shape of the free surface and the evolution of kinetic and potential energy with good accuracy in the early stages of shoaling.
Impulse waves generated by snow avalanches: Momentum and energy transfer to a water body
Zitti, Gianluca; Ancey, Christophe; Postacchini, Matteo; Brocchini, Maurizio
2016-12-01
When a snow avalanche enters a body of water, it creates an impulse wave whose effects may be catastrophic. Assessing the risk posed by such events requires estimates of the wave's features. Empirical equations have been developed for this purpose in the context of landslides and rock avalanches. Despite the density difference between snow and rock, these equations are also used in avalanche protection engineering. We developed a theoretical model which describes the momentum transfers between the particle and water phases of such events. Scaling analysis showed that these momentum transfers were controlled by a number of dimensionless parameters. Approximate solutions could be worked out by aggregating the dimensionless numbers into a single dimensionless group, which then made it possible to reduce the system's degree of freedom. We carried out experiments that mimicked a snow avalanche striking a reservoir. A lightweight granular material was used as a substitute for snow. The setup was devised so as to satisfy the Froude similarity criterion between the real-world and laboratory scenarios. Our experiments in a water channel showed that the numerical solutions underestimated wave amplitude by a factor of 2 on average. We also compared our experimental data with those obtained by Heller and Hager (2010), who used the same relative particle density as in our runs, but at higher slide Froude numbers.
GRACE-derived terrestrial water storage depletion associated with the 2003 European heat wave
DEFF Research Database (Denmark)
Andersen, Ole Baltazar; Seneviratne, S.I.; Hinderer, J.
2005-01-01
datasets agree well with the GRACE measurements despite the disparity of the employed information; the difference between datasets tends to be within GRACE margin of error. The April-to-August terrestrial water storage depletion is found to be significantly larger in 2003 than in 2002 from both models......The GRACE twin satellites reveal large inter-annual terrestrial water-storage variations between 2002 and 2003 for central Europe. GRACE observes a negative trend in regional water storage from 2002 to 2003 peaking at -7.8 cm in central Europe with an accuracy of 1 cm. The 2003 excess terrestrial...... water storage depletion observed from GRACE can be related to the record-breaking heat wave that occurred in central Europe in 2003. We validate the measurements from GRACE using two independent hydrological estimates and direct gravity observations from superconducting gravimeters in Europe. All...
Droghei, R.; Falcini, F.; Casalbore, D.; Martorelli, E.; Mosetti, R.; Sannino, G.; Santoleri, R.; Chiocci, F. L.
2016-11-01
Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary “current” that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.
Droghei, R; Falcini, F; Casalbore, D; Martorelli, E; Mosetti, R; Sannino, G; Santoleri, R; Chiocci, F L
2016-11-03
Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary "current" that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.
Wind waves modelling on the water body with coupled WRF and WAVEWATCH III models
Kuznetsova, Alexandra; Troitskaya, Yuliya; Kandaurov, Alexander; Baydakov, Georgy; Vdovin, Maxim; Papko, Vladislav; Sergeev, Daniil
2015-04-01
Simulation of ocean and sea waves is an accepted instrument for the improvement of the weather forecasts. Wave modelling, coupled models modelling is applied to open seas [1] and is less developed for moderate and small inland water reservoirs and lakes, though being of considerable interest for inland navigation. Our goal is to tune the WAVEWATCH III model to the conditions of the inland reservoir and to carry out the simulations of surface wind waves with coupled WRF (Weather Research and Forecasting) and WAVEWATCH III models. Gorky Reservoir, an artificial lake in the central part of the Volga River formed by a hydroelectric dam, was considered as an example of inland reservoir. Comparing to [2] where moderate constant winds (u10 is up to 9 m/s) of different directions blowing steadily all over the surface of the reservoir were considered, here we apply atmospheric model WRF to get wind input to WAVEWATCH III. WRF computations were held on the Yellowstone supercomputer for 4 nested domains with minimum scale of 1 km. WAVEWATCH III model was tuned for the conditions of the Gorky Reservoir. Satellite topographic data on altitudes ranged from 56,6° N to 57,5° N and from 42.9° E to 43.5° E with increments 0,00833 ° in both directions was used. 31 frequencies ranged from 0,2 Hz to 4 Hz and 30 directions were considered. The minimal significant wave height was changed to the lower one. The waves in the model were developing from some initial seeding spectral distribution (Gaussian in frequency and space, cosine in direction). The range of the observed significant wave height in the numerical experiment was from less than 1 cm up to 30 cm. The field experiments were carried out in the south part of the Gorky reservoir from the boat [2, 3]. 1-D spectra of the field experiment were compared with those obtained in the numerical experiments with different parameterizations of flux provided in WAVEWATCH III both with constant wind input and WRF wind input. For all the
Charland, Jenna; Touboul, Julien; Rey, Vincent
2013-04-01
Wave propagation against current : a study of the effects of vertical shears of the mean current on the geometrical focusing of water waves J. Charland * **, J. Touboul **, V. Rey ** jenna.charland@univ-tln.fr * Direction Générale de l'Armement, CNRS Délégation Normandie ** Université de Toulon, 83957 La Garde, France Mediterranean Institute of Oceanography (MIO) Aix Marseille Université, 13288 Marseille, France CNRS/INSU, IRD, MIO, UM 110 In the nearshore area, both wave propagation and currents are influenced by the bathymetry. For a better understanding of wave - current interactions in the presence of a 3D bathymetry, a large scale experiment was carried out in the Ocean Basin FIRST, Toulon, France. The 3D bathymetry consisted of two symmetric underwater mounds on both sides in the mean wave direction. The water depth at the top the mounds was hm=1,5m, the slopes of the mounds were of about 1:3, the water depth was h=3 m elsewhere. For opposite current conditions (U of order 0.30m/s), a huge focusing of the wave up to twice its incident amplitude was observed in the central part of the basin for T=1.4s. Since deep water conditions are verified, the wave amplification is ascribed to the current field. The mean velocity fields at a water depth hC=0.25m was measured by the use of an electromagnetic current meter. The results have been published in Rey et al [4]. The elliptic form of the "mild slope" equation including a uniform current on the water column (Chen et al [1]) was then used for the calculations. The calculated wave amplification of factor 1.2 is significantly smaller than observed experimentally (factor 2). So, the purpose of this study is to understand the physical processes which explain this gap. As demonstrated by Kharif & Pelinovsky [2], geometrical focusing of waves is able to modify significantly the local wave amplitude. We consider this process here. Since vertical velocity profiles measured at some locations have shown significant
Explicit use of the Biot coefficient in predicting shear-wave velocity of water-saturated sediments
Lee, M.W.
2006-01-01
Predicting the shear-wave (S-wave) velocity is important in seismic modelling, amplitude analysis with offset, and other exploration and engineering applications. Under the low-frequency approximation, the classical Biot-Gassmann theory relates the Biot coefficient to the bulk modulus of water-saturated sediments. If the Biot coefficient under in situ conditions can be estimated, the shear modulus or the S-wave velocity can be calculated. The Biot coefficient derived from the compressional-wave (P-wave) velocity of water-saturated sediments often differs from and is less than that estimated from the S-wave velocity, owing to the interactions between the pore fluid and the grain contacts. By correcting the Biot coefficients derived from P-wave velocities of water-saturated sediments measured at various differential pressures, an accurate method of predicting S-wave velocities is proposed. Numerical results indicate that the predicted S-wave velocities for consolidated and unconsolidated sediments agreewell with measured velocities. ?? 2006 European Association of Geoscientists & Engineers.
Digital Repository Service at National Institute of Oceanography (India)
Nair, M.A.; SanilKumar, V.
An understanding of the wave spectral shapes is of primary importance for the design of marine facilities. In this paper, the wave spectra collected from January 2011 to December 2015 in the coastal waters of the eastern Arabian Sea using the moored...
Liu, Yu; Yu, Xiping
2016-09-01
A coupled phase-field and volume-of-fluid method is developed to study the sensitive behavior of water waves during breaking. The THINC model is employed to solve the volume-of-fluid function over the entire domain covered by a relatively coarse grid while the phase-field model based on Allen-Cahn equation is applied over the fine grid. A special algorithm that takes into account the sharpness of the diffuse-interface is introduced to correlate the order parameter obtained on the fine grid and the volume-of-fluid function obtained on the coarse grid. The coupled model is then applied to the study of water waves generated by moving pressures on the free surface. The deformation process of the wave crest during the initial stage of breaking is discussed in details. It is shown that there is a significant variation of the free nappe developed at the front side of the wave crest as the wave steepness differs. It is of a plunging type at large wave steepness while of a spilling type at small wave steepness. The numerical results also indicate that breaking occurs later and the duration of breaking is shorter for waves of smaller steepness and vice versa. Neglecting the capillary effect leads to wave breaking with a sharper nappe and a more dynamic plunging process. The surface tension also has an effect to prevent the formation of a free nappe at the front side of the wave crest in some cases.
Interaction of water waves with small undulations on a porous bed in a two-layer ice-covered fluid
Panda, Srikumar; Martha, S. C.
2013-12-01
The scattering problem involving water waves by small undulation on the porous ocean-bed in a two-layer fluid, is investigated within the framework of the two-dimensional linear water wave theory where the upper layer is covered by a thin uniform sheet of ice modeled as a thin elastic plate. In such a two-layer fluid there exist waves with two different modes, one with a lower wave number propagate along the ice-cover whilst those with a higher wave number propagate along the interface. An incident wave of a particular wave number gets reflected and transmitted over the bottom undulation into waves of both modes. Perturbation analysis in conjunction with the Fourier transform technique is used to derive the first-order corrections of reflection and transmission coefficients for both the modes due to incident waves of two different modes. One special type of bottom topography is considered as an example to evaluate the related coefficients in detail. These coefficients are depicted in graphical forms to demonstrate the transformation of wave energy between the two modes and also to illustrate the effects of the ice sheet and the porosity of the undulating bed.
A Nonlinear Coupled-Mode System for Water Waves over a General Bathymetry
Athanassoulis, G. A.; Belibassakis, K. A.
2003-04-01
In the present work we consider the problem of non-linear gravity waves propagating over a general bathymetry. The simpler two dimensional problem (one horizontal dimension) is first examined. An essential feature of this problem is that the wave field is not spatially periodic. Extra difficulties are introduced by the fact that we wish to drop the assumptions of smallness of the free-surface and bottom slope. The interaction of free-surface gravity waves with uneven bottom topography requires, in principle, the solution of a complicated nonlinear boundary value problem. Under the assumptions of incompressibility and irrotationality, the problem of evolution of water waves, over a variable bathymetry region, admits of at least two different varia-tional formulations: A Hamiltonian one, proposed by Petrov (1964) and exploited further by Zakharov (1968) and various other authors thenceforth, and an unconstrained one, proposed by Luke (1967). Our main concern herewith is to develop a non-linear theory for the case of a smooth, generally shaped bathymetry, without imposing any mild-slope type assumptions neither on the free-surface nor on the bottom boundary. The present development is based on Luke's variational principle, in which the admissible fields are free of essential conditions, except, of course, for the smoothness and completeness (compatibility) prerequisites. The vertical structure of the wave field is exactly represented by means of a modal-type series expansion of the wave potential (Athanassoulis and Belibassakis 2000). This series expansion contains the usual propagating and evanescent modes, plus two additional modes, called the free-surface mode and the sloping-bottom mode, introduced in order to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. A similar technique has been successfully applied to the solution of the linearised (Athanassoulis and Belibassakis 1999) and the second-order (Belibassakis and
Gravity-capillary waves in countercurrent air/water turbulent flow
Zonta, Francesco; Onorato, Miguel; Soldati, Alfredo
2016-11-01
Using the Direct Numerical Simulation (DNS) of the Navier-Stokes equations, we analyze the dynamics of the interface between air and water when both phases are driven by opposite pressure gradients (countercurrent configuration). The Reynolds number (Re), the Weber number (We) and the Froude number (Fr) fully describe the physical problem. We examine the problem of the transient growth of interface waves for different combinations of physical parameters. Keeping Re constant and varying We and Fr , we show that, in the initial stages of the wave generation process, the amplitude of the interface elevation grows in time as t2 / 5 . Wavenumber spectra, E (kx) , of the surface elevation in the capillary range are in good agreement with the prediction of the Wave Turbulence Theory. Finally, the wave-induced modification of the average wind and current velocity profiles is addressed. CINECA supercomputing centre (Bologna, Italy) and ISCRA Computing Initiative are gratefully acknowledged for generous allowance of computer resources. Support from PRIN (under Grant 2006098584 004) is gratefully acknowledged. Support from Regione Autonoma.
Vargas-Magaña, Rosa; Panayotaros, Panayotis
2015-11-01
We study the problem of wave propagation in a long-wave asymptotic regime over variable bottom of an ideal irrotational fluid in the framework of the Hamiltonian formulation in which the non-local Dirichlet-Neumann (DtN) operator appears explicitly in the Hamiltonian. We propose a non-local Hamiltonian model for bidirectional wave propagation in shallow water that involves pseudodifferential operators that approximate the DtN operator for variable depth. These models generalize the Boussinesq system as they include the exact dispersion relation in the case of constant depth. We present results for the normal modes and eigenfrequencies of the linearized problem. We see that variable topography introduces effects such as steepening of normal modes with increasing variation of depth, as well as amplitude modulation of the normal modes in certain wavelength ranges. Numerical integration shows that the constant depth nonlocal Boussinesq model with quadratic nonlinearity can capture the evolution obtained with higher order approximations of the DtN operator. In the case of variable depth we observe certain oscillations in width of the crest and also some interesting textures in the evolution of wave crests during the passage from obstacles.
Lipkens, B; Costolo, M; Stevens, A; Rietman, Edward
2010-01-01
The separation of micron-sized bacterial spores (Bacillus cereus) from a steady flow of water through the use of ultrasonic standing waves is demonstrated. An ultrasonic resonator with cross-section of 0.0254 m x 0.0254 m has been designed with a flow inlet and outlet for a water stream that ensures laminar flow conditions into and out of the resonator section of the flow tube. A 0.01905-m diameter PZT-4, nominal 2-MHz transducer is used to generate ultrasonic standing waves in the resonator. The acoustic resonator is 0.0356 m from transducer face to the opposite reflector wall with the acoustic field in a direction orthogonal to the water flow direction. At fixed frequency excitation, spores are concentrated at the stable locations of the acoustic radiation force and trapped in the resonator region. The effect of the transducer voltage and frequency on the efficiency of spore capture in the resonator has been investigated. Successful separation of B. cereus spores from water with typical volume flow rates of...
Analysis of nonlinear shallow water waves in a tank by concentrated mass model
Ishikawa, Satoshi; Kondou, Takahiro; Matsuzaki, Kenichiro; Yamamura, Satoshi
2016-06-01
The sloshing of liquid in a tank is an important engineering problem. For example, liquid storage tanks in industrial facilities can be damaged by earthquakes, and conversely liquid tanks, called tuned liquid damper, are often used as passive mechanical dampers. The water depth is less often than the horizontal length of the tank. In this case, shallow water wave theory can be applied, and the results indicate that the surface waveform in a shallow excited tank exhibits complex behavior caused by nonlinearity and dispersion of the liquid. This study aims to establish a practical analytical model for this phenomenon. A model is proposed that consists of masses, connecting nonlinear springs, connecting dampers, base support dampers, and base support springs. The characteristics of the connecting nonlinear springs are derived from the static and dynamic pressures. The advantages of the proposed model are that nonlinear dispersion is considered and that the problem of non-uniform water depth can be addressed. To confirm the validity of the model, numerical results obtained from the model are compared with theoretical values of the natural frequencies of rectangular and triangular tanks. Numerical results are also compared with experimental results for a rectangular tank. All computational results agree well with the theoretical and experimental results. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear shallow water wave problems.
Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter
2016-08-01
Coupled circulation (NEMO) and wave model (WAM) system was used to study the effects of surface ocean waves on water temperature distribution and heat exchange at regional scale (the Baltic Sea). Four scenarios—including Stokes-Coriolis force, sea-state dependent energy flux (additional turbulent kinetic energy due to breaking waves), sea-state dependent momentum flux and the combination these forcings—were simulated to test the impact of different terms on simulated temperature distribution. The scenario simulations were compared to a control simulation, which included a constant wave-breaking coefficient, but otherwise was without any wave effects. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwelling's. Overall, when all three wave effects were accounted for, did the estimates of temperature improve compared to control simulation. During the summer, the wave-induced water temperature changes were up to 1 °C. In northern parts of the Baltic Sea, a warming of the surface layer occurs in the wave included simulations in summer months. This in turn reduces the cold bias between simulated and measured data, e.g. the control simulation was too cold compared to measurements. The warming is related to sea-state dependent energy flux. This implies that a spatio-temporally varying wave-breaking coefficient is necessary, because it depends on actual sea state. Wave-induced cooling is mostly observed in near-coastal areas and is the result of intensified upwelling in the scenario, when Stokes-Coriolis forcing is accounted for. Accounting for sea-state dependent momentum flux results in modified heat exchange at the water-air boundary which consequently leads to warming of surface water compared to control simulation.
K2_SPH Method and its Application for 2-D Water Wave Simulation
Institute of Scientific and Technical Information of China (English)
Zhenhong Hu; Xing Zheng; Wenyang Duan; Qingwei Ma
2011-01-01
Smoothed Particle Hydrodynamics(SPH)is a Lagrangian meshless particle method.However,its low accuracy of kernel approximation when particles are distributed disorderly or located near the boundary is an obstacle standing in the way of its wide application.Adopting the Taylor series expansion method and solving the integral equation matrix,the second order kernel approximation method can be obtained,namely K2_SPH,which is discussed in this paper.This method is similar to the Finite Particle Method.With the improvement of kernel approximation,some numerical techniques should be adopted for different types of boundaries,such as a free surface boundary and solid boundary,which are two key numerical techniques of K2_SPH for water wave simulation.This paper gives some numerical results of two dimensional water wave simulations involving standing wave and sloshing tank problems by using K2_SPH.From the comparison of simulation results,the K2 SPH method is more reliable than standard SPH.
Time-domain simulation for water wave radiation by floating structures (Part A)
Institute of Scientific and Technical Information of China (English)
XU Gang; DUAN Wen-yang
2008-01-01
Direct time-domain simulation of floating structures has advantages: it can calculate wave pressure fields and forces directly;and it is useful for coupled analysis of floating structures with a mooring system. A time-domain boundary integral equation method is presented to simulate three-dimensional water wave radiation problems. A stable form of the integration free-surface boundary condition (IFBC) is used to update velocity potentials on the free surface. A multi-transmitting formula (MTF) method with an artificial speed is introduced to the artificial radiation boundary (ARB). The method was applied to simulate a semi-spherical liquefied natural gas (LNG) carrier and a semi-submersible undergoing specified harmonic motion. Numerical parameters such as the form of the ARB,and the time and space discretization related to this method are discussed. It was found that a good agreement can be obtained when artificial speed is between 0.6 and 1.6 times the phase velocity of water waves in the MTF method. A simulation can be done for a long period of time by this method without problems of instability,and the method is also accurate and computationally efficient.
Analysis on shock wave speed of water hammer of lifting pipes for deep-sea mining
Zhou, Zhi-jin; Yang, Ning; Wang, Zhao
2013-04-01
Water hammer occurs whenever the fluid velocity in vertical lifting pipe systems for deep-sea mining suddenly changes. In this work, the shock wave was proven to play an important role in changing pressures and periods, and mathematical and numerical modeling technology was presented for simulated transient pressure in the abnormal pump operation. As volume concentrations were taken into account of shock wave speed, the experiment results about the pressure-time history, discharge-time history and period for the lifting pipe system showed that: as its concentrations rose up, the maximum transient pressure went down, so did its discharges; when its volume concentrations increased gradually, the period numbers of pressure decay were getting less and less, and the corresponding shock wave speed decreased. These results have highly coincided with simulation results. The conclusions are important to design lifting transporting system to prevent water hammer in order to avoid potentially devastating consequences, such as damage to components and equipment and risks to personnel.
Analysis on Shock Wave Speed of Water Hammer of Lifting Pipes for Deep-Sea Mining
Institute of Scientific and Technical Information of China (English)
ZHOU Zhi-jin; YANG Ning; WANG Zhao
2013-01-01
Water hammer occurs whenever the fluid velocity in vertical lifting pipe systems for deep-sea mining suddenly changes.In this work,the shock wave was proven to play an important role in changing pressures and periods,and mathematical and numerical modeling technology was presented for simulated transient pressure in the abnormal pump operation.As volume concentrations were taken into account of shock wave speed,the experiment results about the pressure-time history,discharge-time history and period for the lifting pipe system showed that:as its concentrations rose up,the maximum transient pressure went down,so did its discharges; when its volume concentrations increased gradually,the period numbers of pressure decay were getting less and less,and the corresponding shock wave speed decreased.These results have highly coincided with simulation results.The conclusions are important to design lifting transporting system to prevent water hammer in order to avoid potentially devastating consequences,such as damage to components and equipment and risks to personnel.
Hydrodynamic coefﬁcients for water-wave diffraction by spherical structures
Indian Academy of Sciences (India)
Swaroop Nandan Bora
2004-12-01
Evaluation of hydrodynamic coefﬁcients and loads on submerged or ﬂoating bodies is of great signiﬁcance in designing these structures. Some special regular-shaped geometries such as those of cylindrical (circular, elliptic) and spherical (hemisphere, sphere, spheroid) structures are usually considered to obtain analytical solutions to wave diffraction and radiation problems. The work presented here is the result of water-wave interaction with submerged spheres. Analytical expressions for various hydrodynamic coefﬁcients and loads due to the diffraction of water waves by a submerged sphere are obtained. The exciting force components due to surge and heave motions are derived by solving the diffraction problem. Theory of multipole expansions is used to express the velocity potentials in terms of an inﬁnite series of associated Legendre polynomials with unknown coefﬁcients and the orthogonality of the polynomials is utilized to simplify the expressions. Since the inﬁnite series appearing in various expressions have excellent truncation properties, they are evaluated by considering only a ﬁnite number of terms. Gaussian quadrature is used to evaluate the integrals. Numerical estimates for the analytical expressions for the hydrodynamic coefﬁcients and loads are presented for various depth to radius ratios. Consideration of more values for depth makes it easy to compare the results with those available. The results obtained match closely with those obtained earlier by Wang and Wu and their coworkers.
Sound Wave Energy Resulting from the Impact of Water Drops on the Soil Surface.
Ryżak, Magdalena; Bieganowski, Andrzej; Korbiel, Tomasz
2016-01-01
The splashing of water drops on a soil surface is the first step of water erosion. There have been many investigations into splashing-most are based on recording and analysing images taken with high-speed cameras, or measuring the mass of the soil moved by splashing. Here, we present a new aspect of the splash phenomenon's characterization the measurement of the sound pressure level and the sound energy of the wave that propagates in the air. The measurements were carried out for 10 consecutive water drop impacts on the soil surface. Three soils were tested (Endogleyic Umbrisol, Fluvic Endogleyic Cambisol and Haplic Chernozem) with four initial moisture levels (pressure heads: 0.1 kPa, 1 kPa, 3.16 kPa and 16 kPa). We found that the values of the sound pressure and sound wave energy were dependent on the particle size distribution of the soil, less dependent on the initial pressure head, and practically the same for subsequent water drops (from the first to the tenth drop). The highest sound pressure level (and the greatest variability) was for Endogleyic Umbrisol, which had the highest sand fraction content. The sound pressure for this soil increased from 29 dB to 42 dB with the next incidence of drops falling on the sample The smallest (and the lowest variability) was for Fluvic Endogleyic Cambisol which had the highest clay fraction. For all experiments the sound pressure level ranged from ~27 to ~42 dB and the energy emitted in the form of sound waves was within the range of 0.14 μJ to 5.26 μJ. This was from 0.03 to 1.07% of the energy of the incident drops.
Sound Wave Energy Resulting from the Impact of Water Drops on the Soil Surface.
Directory of Open Access Journals (Sweden)
Magdalena Ryżak
Full Text Available The splashing of water drops on a soil surface is the first step of water erosion. There have been many investigations into splashing-most are based on recording and analysing images taken with high-speed cameras, or measuring the mass of the soil moved by splashing. Here, we present a new aspect of the splash phenomenon's characterization the measurement of the sound pressure level and the sound energy of the wave that propagates in the air. The measurements were carried out for 10 consecutive water drop impacts on the soil surface. Three soils were tested (Endogleyic Umbrisol, Fluvic Endogleyic Cambisol and Haplic Chernozem with four initial moisture levels (pressure heads: 0.1 kPa, 1 kPa, 3.16 kPa and 16 kPa. We found that the values of the sound pressure and sound wave energy were dependent on the particle size distribution of the soil, less dependent on the initial pressure head, and practically the same for subsequent water drops (from the first to the tenth drop. The highest sound pressure level (and the greatest variability was for Endogleyic Umbrisol, which had the highest sand fraction content. The sound pressure for this soil increased from 29 dB to 42 dB with the next incidence of drops falling on the sample The smallest (and the lowest variability was for Fluvic Endogleyic Cambisol which had the highest clay fraction. For all experiments the sound pressure level ranged from ~27 to ~42 dB and the energy emitted in the form of sound waves was within the range of 0.14 μJ to 5.26 μJ. This was from 0.03 to 1.07% of the energy of the incident drops.
Institute of Scientific and Technical Information of China (English)
张洪生; 洪广文; 丁平兴; 曹振轶
2001-01-01
In this paper, the characteristics of different forms of mild slope equations for non-linear wave are analyzed, and new non-linear theoretic models for wave propagation are presented, with non-linear terms added to the mild slope equations for non-stationary linear waves and dissipative effects considered. Numerical simulation models are developed of non-linear wave propagation for waters of mildly varying topography with complicated boundary, and the effects are studied of different non-linear corrections on calculation results of extended mild slope equations. Systematical numerical simulation tests show that the present models can effectively reflect non-linear effects.
Effects of ultrasonic waves on the interfacial forces between oil and water.
Hamida, Tarek; Babadagli, Tayfun
2008-04-01
The effect of ultrasound on flow through a capillary using the pendant drop method was investigated. Water was injected into a 0.1 mm Hastelloy C-276 capillary tube submersed into several mineral oils with different viscosity, and kerosene. The average drop rate per minute was measured at several ultrasonic intensities. We observed that there exists a peak drop rate at a characteristic intensity, which strongly depends on oil viscosity and the interfacial tension between water and the oil. The semi-quantitative results reveal that the remarkable change in the interfacial forces between oil and water could be the explanation to the enhancement of oil recovery when the ultrasonic waves are applied.
Nonlinear focusing of ultrasonic waves by an axisymmetric diffraction grating embedded in water
Energy Technology Data Exchange (ETDEWEB)
Jiménez, N.; Picó, R. [Instituto de Investigación para la Gestión Integrada de zonas Costeras, Universitat Politècnica de València, Paranimf 1, 46730 Grao de Gandia, València (Spain); Romero-García, V. [LUNAM Université, Université du Maine, LAUM UMR CNRS 6613, Av. O. Messiaen, 72085 Le Mans (France); Garcia-Raffi, L. M. [Instituto Universitario de Matemática Pura y Aplicada, Universitat Politècnica de València, Camino de Vera s/n, 46022 València (Spain); Staliunas, K. [ICREA, Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Colom, 11, E-08222 Terrassa, Barcelona (Spain)
2015-11-16
We report the nonlinear focusing of ultrasonic waves by an axisymmetric diffraction grating immersed in water. In the linear regime, the system presents high focal gain (32 dB), with a narrow beam-width and intense side lobes as it is common in focusing by Fresnel-like lenses. Activating the nonlinearity of the host medium by using high amplitude incident waves, the focusing properties of the lens dramatically change. Theoretical predictions show that the focal gain of the system extraordinary increases in the strongly nonlinear regime (Mach number of 6.1 × 10{sup −4}). Particularly, the harmonic generation is locally activated at the focal spot, and the second harmonic beam is characterized by strongly reduced side-lobes and an excellent beam profile as experiments show in agreement with theory. The results can motivate applications in medical therapy or second harmonic imaging.
Transient wave-blockage interaction and extended blockage detection in elastic water pipelines
Duan, H. F.; Lee, P. J.; Ghidaoui, M. S.; Tuck, J.
2014-04-01
Extended partial blockages are common in pressurized water pipelines and can result in the wastage of energy, the reduction in system carrying capacity and the increased potential for contamination. This paper investigates the transient wave-blockage interaction and its application to extended blockage detection in pipelines, where blockage-induced changes to the system resonant frequencies are observed. The frequency shifting is first inspected and explained in this study through wave perturbation analysis, providing a theoretical confirmation for the result that unlike discrete blockages, extended blockages cause resonant frequency shifts in the system. Furthermore, an analytical expression is derived for the relationship between the blockage properties and the resonant frequency shifts and is used to detect the blockages in this study. The obtained results are validated through both numerical applications and laboratory experiments, where the accuracy and efficiency of the developed method for extended blockage detection are tested.
Competing turbulent cascades and eddy-wave interactions in shallow water equilibria
Weichman, Peter B
2016-01-01
In recent work, Renaud, Venaille, and Bouchet (RVB) revisit the equilibrium statistical mechanics theory of the shallow water equations, within a microcanonical approach, focusing on a more careful treatment of the energy partition between inertial gravity wave and eddy motions in the equilibrium state, and deriving joint probability distributions for the corresponding dynamical degrees of freedom. The authors derive a Liouville theorem that determines the underlying phase space statistical measure, but then, through some physical arguments, actually compute the equilibrium statistics using a measure that \\emph{violates} this theorem. Here, using a more convenient, but essentially equivalent, grand canonical approach, the full statistical theory consistent with the Liouville theorem is derived. The results reveal several significant differences from the previous results: (1) The microscale wave motions lead to a strongly fluctuating thermodynamics, including long-ranged correlations, in contrast to the mean-f...
A Stabilised Nodal Spectral Element Method for Fully Nonlinear Water Waves
Engsig-Karup, Allan Peter; Bigoni, Daniele
2015-01-01
We present an arbitrary-order spectral element method for general-purpose simulation of non-overturning water waves, described by fully nonlinear potential theory. The method can be viewed as a high-order extension of the classical finite element method proposed by Cai et al (1998) \\cite{CaiEtAl1998}, although the numerical implementation differs greatly. Features of the proposed spectral element method include: nodal Lagrange basis functions, a general quadrature-free approach and gradient recovery using global $L^2$ projections. The quartic nonlinear terms present in the Zakharov form of the free surface conditions can cause severe aliasing problems and consequently numerical instability for marginally resolved or very steep waves. We show how the scheme can be stabilised through a combination of over-integration of the Galerkin projections and a mild spectral filtering on a per element basis. This effectively removes any aliasing driven instabilities while retaining the high-order accuracy of the numerical...
Duchene, Vincent
2011-01-01
This paper deals with the dead-water phenomenon, which occurs when a ship sails in a stratified fluid, and experiences an important drag due to waves below the surface. More generally, we study the generation of internal waves by a disturbance moving at constant speed on top of two layers of fluids of different densities. Starting from the full Euler equations, we present several nonlinear asymptotic models, in the long wave regime. These models are rigorously justified by consistency or convergence results. A careful theoretical and numerical analysis is then provided, in order to predict the behavior of the flow and in which situations the dead-water effect appears.
Potemkin, F V; Podshivalov, A A; Gordienko, V M
2014-01-01
Using shadow photography technique we have observed shock acoustic wave from optical breakdown, excited in water by tightly focused Cr:Forsterite femtosecond laser beam, and have found two different regimes of shock wave generation by varying only the energy of laser pulse. At low energies a single spherical shock wave is generated from laser beam waist, and its radius tends to saturation with energy increasing. At higher energies long laser filament in water is fired, that leads to the cylindrical shock wave generation, which longitude increases logarithmically with laser pulse energy. From shadow pictures we estimated maximal velocity in front or shock wave of 2300+/-150m/s and pressure of 1.0+/-0.1 GPa
A stabilised nodal spectral element method for fully nonlinear water waves
Engsig-Karup, A. P.; Eskilsson, C.; Bigoni, D.
2016-08-01
We present an arbitrary-order spectral element method for general-purpose simulation of non-overturning water waves, described by fully nonlinear potential theory. The method can be viewed as a high-order extension of the classical finite element method proposed by Cai et al. (1998) [5], although the numerical implementation differs greatly. Features of the proposed spectral element method include: nodal Lagrange basis functions, a general quadrature-free approach and gradient recovery using global L2 projections. The quartic nonlinear terms present in the Zakharov form of the free surface conditions can cause severe aliasing problems and consequently numerical instability for marginally resolved or very steep waves. We show how the scheme can be stabilised through a combination of over-integration of the Galerkin projections and a mild spectral filtering on a per element basis. This effectively removes any aliasing driven instabilities while retaining the high-order accuracy of the numerical scheme. The additional computational cost of the over-integration is found insignificant compared to the cost of solving the Laplace problem. The model is applied to several benchmark cases in two dimensions. The results confirm the high order accuracy of the model (exponential convergence), and demonstrate the potential for accuracy and speedup. The results of numerical experiments are in excellent agreement with both analytical and experimental results for strongly nonlinear and irregular dispersive wave propagation. The benefit of using a high-order - possibly adapted - spatial discretisation for accurate water wave propagation over long times and distances is particularly attractive for marine hydrodynamics applications.
Myrhaug, Dag; Wang, Hong; Holmedal, Lars Erik
2016-04-01
The Stokes drift represents an important transport component of ocean circulation models. Locally it is responsible for transport of e.g. contaminated ballast water from ships, oil spills, plankton and larvae. It also plays an important role in mixing processes across the interphase between the atmosphere and the ocean. The Stokes drift is the mean Lagrangian velocity obtained from the water particle trajectory in the wave propagation direction; it is maximum at the surface, decreasing rapidly with the depth below the surface. The total mean mass transport is obtained by integrating the Stokes drift over the water depth; this is also referred to as the volume Stokes transport. The paper provides a simple analytical method which can be used to give estimates of the Stokes drift in moderate intermediate water depth based on short-term variation of wave conditions. This is achieved by using a joint distribution of individual wave heights and wave periods together with an explicit solution of the wave dispersion equation. The mean values of the surface Stokes drift and the volume Stokes transport for individual random waves within a sea state are presented, and the effects of water depth and spectral bandwidth parameter are discussed. Furthermore, example of results corresponding to typical field conditions are presented to demonstrate the application of the method, including the Stokes drift profile in the water column beneath the surface. Thus, the present analytical method can be used to estimate the Stokes drift in moderate intermediate water depth for random waves within a sea state based on available wave statistics.
Energy Technology Data Exchange (ETDEWEB)
Nisina, K.
1982-07-13
Provides technique and equipment for producing a new fuel by transforming ionized water with the aid of ultra-short waves that are produced by a gravitation wave generator. The generator is a torroidal coil condensor with an Fe-core whose windings are connected to the oil condenser situated around it. Desalinated ocean water is placed into the water-ionizing unit, whose electrical contacts tie it to the poles of the generator's windings and the water is then ionized. The ionized water mixed with petroleum fuel is placed into the cylindrical cell of the generator in which ultrashort waves are generated, thus transforming the mixture into one that includes heavy hydrogen and intermediate hydrocarbons with C=C-bonds, from which the new fuel is finally derived with C=C-bonds. This new fuel has improved combustion properties and has a minimum of O- and S-compounds.
Finite water depth effect on wave-body problems solved by Rankine source method
Feng, Aichun; Tang, Peng; You, Yunxiang; Liu, Kaizhou
2017-04-01
Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non- desingularized technique. Free surface and seabed surface profiles are represented by continuous panels rather than a discretization by isolated points. These panels are positioned exactly on the fluid boundary surfaces and therefore no desingularization technique is required. Space increment method is applied for both free surface source and seabed source arrangements to reduce computational cost and improve numerical efficiency. Fourth order Runge-Kutta iteration scheme is adopted on the free surface updating at every time step. The finite water depth effect is studied quantitatively for a series of cylinders with different B/T ratios. The accuracy and efficiency of the proposed model are validated by comparison with published numerical results and experimental data. Numerical results show that hydrodynamic coefficients vary for cylinder bodies with different ratios of B/T. For certain set of B/T ratios the effect of finite water depth increases quickly with the increase of motion frequency and becomes stable when frequency is relatively large. It also shows that water depths have larger hydrodynamic effects on cylinder with larger breadth to draft ratios. Both the heave added mass and damping coefficients increase across the frequency range with the water depths decrease for forced heave motion. The water depths have smaller effects on sway motion response than on heave motion response.
The Influence of Water on Seismic Wave Attenuation in the Upper Mantle
David, E. C.; Jackson, I.; Faul, U.; Berry, A.
2014-12-01
Trace amounts of water, present as protons structurally bound in olivine crystal defects, are inferred to significantly enhance the low-strain solid-state viscoelastic relaxation responsible for attenuation and dispersion of seismic waves in the upper mantle. This inferrence is supported by recent observation of water weakening at moderate compressive strains in synthetic, water-undersaturated aggregates (Faul et al., in preparation). In these fine-grained olivine polycrystals of Fo90 composition, doped with 0.02wt% TiO2, "water" is incorporated in the remarkably stable Ti-clinohumite defect. Such synthetic olivine specimens reproduce the infrared spectra of natural mantle olivines (Berry et al., 2005), and present the advantage of being melt-free and of low dislocation density. The water contents in such synthetic polycrystalline olivine aggregates, which can be quantitatively measured by Fourier Transform Infrared Spectroscopy (FTIR), range up to 90 ppm, and are thus representative of water-undersaturated conditions in the upper mantle. We will report here the outcome of torsional-oscillation tests,in which attenuation and shear modulus were measured at seismic frequencies (mHz-Hz) and various temperatures up to 1300C on Pt-encapsulated, Ti-doped olivine specimens, enclosed within a mild-steel jacket.
Mechanical balance laws for fully nonlinear and weakly dispersive water waves
Kalisch, Henrik; Mitsotakis, Dimitrios
2015-01-01
The Serre-Green-Naghdi system is a coupled, fully nonlinear system of dispersive evolution equations which approximates the full water wave problem. The system is an extension of the well known shallow-water system to the situation where the waves are long, but not so long that dispersive effects can be neglected. In the current work, the focus is on deriving mass, momentum and energy densities and fluxes associated with the Serre-Green-Naghdi system. These quantities arise from imposing balance equations of the same asymptotic order as the evolution equations. In the case of an even bed, the conservation equations are satisfied exactly by the solutions of the Serre-Green-Naghdi system. The case of variable bathymetry is more complicated, with mass and momentum conservation satisfied exactly, and energy conservation satisfied only in a global sense. In all cases, the quantities found here reduce correctly to the corresponding counterparts in both the Boussinesq and the shallow-water scaling. One consequence o...
Institute of Scientific and Technical Information of China (English)
WEN Xiao-Yong; MENG Xiang-Hua
2013-01-01
In this paper,the (2+1)-dimensional generalization of shallow water wave equation,which may be used to describe the propagation of ocean waves,is analytically investigated.With the aid of symbolic computation,we prove that the (2+1)-dimensional generalization of shallow water wave equation possesses the Painlevé property under a certain condition,and its Lax pair is constructed by applying the singular manifold method.Based on the obtained Lax representation,the Darboux transformation (DT) is constructed.The first iterated solution,second iterated solution and a special N-soliton solution with an arbitrary function are derived with the resulting DT.Relevant properties are graphically illustrated,which might be helpful to understanding the propagation processes for ocean waves in shallow water.
Vogel, Laura J; O'Carroll, Denis M; Edge, Thomas A; Robinson, Clare E
2016-06-01
Foreshore beach sands and pore water may act as a reservoir and nonpoint source of fecal indicator bacteria (FIB) to surface waters. This paper presents data collected at a fine sand beach on Lake Huron, Canada over three field events. The data show that foreshore sand erosion as wave height increases results in elevated Escherichia coli concentrations in surface water, as well as depletion of E. coli from the foreshore sand and pore water. E. coli initially attached to foreshore sand rather than initially residing in the pore water was found to be the main contributor to elevated surface water concentrations. Surface water E. coli concentrations were a function of not only wave height (and associated sand erosion) but also the time elapsed since a preceding period of high wave intensity. This finding is important for statistical regression models used to predict beach advisories. While calculations suggest that foreshore sand erosion may be the dominant mechanism for releasing E. coli to surface water during intensified wave conditions at a fine sand beach, comparative characterization of the E. coli distribution at a coarse sand-cobble beach suggests that interstitial pore water flow and discharge may be more important for coarser sand beaches.
Surface water waves due to an oscillatory wavemaker in the presence of surface tension
Directory of Open Access Journals (Sweden)
B. N. Mandal
1992-01-01
Full Text Available The initial value problem of generation of surface water waves by a harmonically oscillating plane vertical wavemaker in an infinite incompressible fluid under the action of gravity and surface tension is investigated. In the asymptotic evaluation of the free surface depression for large time and distance, the contribution to the integral by stationary phase method gives rise to transient component of the free surface depression while the contribution from the poles give rise to steady state component. It is observed that the presence of surface tension sometimes changes the qualitative nature of the transient component of free surface depression.
Time adaptivity in the diffusive wave approximation to the shallow water equations
Collier, Nathaniel Oren
2013-05-01
We discuss the use of time adaptivity applied to the one dimensional diffusive wave approximation to the shallow water equations. A simple and computationally economical error estimator is discussed which enables time-step size adaptivity. This robust adaptive time discretization corrects the initial time step size to achieve a user specified bound on the discretization error and allows time step size variations of several orders of magnitude. In particular, the one dimensional results presented in this work feature a change of four orders of magnitudes for the time step over the entire simulation. © 2011 Elsevier B.V.
DEFF Research Database (Denmark)
Andersen, Morten Thøtt; Thomsen, Jonas Bjerg
This report describes the behavior and preliminary performance of a simplified standard oscillating water column (OWC) wave energy converter (WEC). The same tests will be conducted at different scales at 6 different test facilities and the results obtained will be used for comparison. This projec...... at Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg. For further information regarding the content of this report please contact Morten Thøtt Andersen (mta@civil.aau.dk) or Jonas Bjerg Thomsen (jbt@civil.aau.dk) from the Department of Civil Engineering....
A stabilised nodal spectral element method for fully nonlinear water waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Eskilsson, C.; Bigoni, Daniele
2016-01-01
We present an arbitrary-order spectral element method for general-purpose simulation of non-overturning water waves, described by fully nonlinear potential theory. The method can be viewed as a high-order extension of the classical finite element method proposed by Cai et al. (1998) [5], although...... the numerical implementation differs greatly. Features of the proposed spectral element method include: nodal Lagrange basis functions, a general quadrature-free approach and gradient recovery using global L2 projections. The quartic nonlinear terms present in the Zakharov form of the free surface conditions...
An efficient flexible-order model for 3D nonlinear water waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Bingham, Harry B.; Lindberg, Ole
2009-01-01
The flexible-order, finite difference based fully nonlinear potential flow model described in [H.B. Bingham, H. Zhang, On the accuracy of finite difference solutions for nonlinear water waves, J. Eng. Math. 58 (2007) 211-228] is extended to three dimensions (3D). In order to obtain an optimal...... scaling of the solution effort multigrid is employed to precondition a GMRES iterative solution of the discretized Laplace problem. A robust multigrid method based on Gauss-Seidel smoothing is found to require special treatment of the boundary conditions along solid boundaries, and in particular...
Multi-Order Exact Solutions for a generalized shallow water wave equation and other nonlinear PDEs
Bagchi, Bijan; Ganguly, Asish
2011-01-01
We seek multi-order exact solutions of a generalized shallow water wave equation along with those corresponding to a class of nonlinear systems described by the KdV, modified KdV, Boussinesq, Klein-Gordon and modified Benjamin-Bona-Mahony equation. We employ a modified version of a generalized Lame equation and subject it to a perturbative treatment identifying the solutions order by order in terms of Jacobi elliptic functions. Our solutions are new and hold the key feature that they are expressible in terms of an auxiliary function f in a generic way. For appropriate choices of f we recover the previous results reported in the literature.
Integrability of an extended (2+1)-dimensional shallow water wave equation with Bell polynomials
Institute of Scientific and Technical Information of China (English)
Wang Yun-Hu; Chen Yong
2013-01-01
We investigate the extended (2+1)-dimensional shallow water wave equation.The binary Bell polynomials are used to construct bilinear equation,bilinear B(a)cklund transformation,Lax pair,and Darboux covariant Lax pair for this equation.Moreover,the infinite conservation laws of this equation are found by using its Lax pair.All conserved densities and fluxes are given with explicit recursion formulas.The N-soliton solutions are also presented by means of the Hirota bilinear method.
On the spatial linear growth of gravity-capillary water waves sheared by a laminar air flow
Tsai, Y.S.; Grass, A.J.; Simons, R.R.
2005-01-01
The initial growth of mechanically generated small amplitude water waves below a laminar air stream was examined numerically and experimentally in order to explore the primary growth mechanism, that is, the interfacial instability of coupled laminar air and water flows. Measurements of the laminar v
Water-waves modes trapped in a canal by a body with the rough surface
Cardone, G; Nazarov, S A
2009-01-01
The problem about a body in a three dimensional infinite channel is considered in the framework of the theory of linear water-waves. The body has a rough surface characterized by a small parameter $\\epsilon>0$ while the distance of the body to the water surface is also of order $\\epsilon$. Under a certain symmetry assumption, the accumulation effect for trapped mode frequencies is established, namely, it is proved that, for any given $d>0$ and integer $N>0$, there exists $\\epsilon(d,N)>0$ such that the problem has at least $N$ eigenvalues in the interval $(0,d)$ of the continuous spectrum in the case $\\epsilon\\in(0,\\epsilon(d,N)) $. The corresponding eigenfunctions decay exponentially at infinity, have finite energy, and imply trapped modes.
Sound wave energy emitted by water drop during the splash on the soil surface
Bieganowski, Andrzej; Ryżak, Magdalena; Korbiel, Tomasz
2017-04-01
A drop of rain falling on the surface of bare soil not only moisturizes but also can cause splash or compaction, depending on the energy of incident drops and the condition of the surface on which it falls. The splash phenomenon can be characterized by the weight of detached soil material (using splash cups) as well as the number and trajectory of splashed particles (using high-speed cameras). The study presents a new aspect of the analysis of the splash phenomenon by measurement of the sound pressure level and the sound energy of the wave that propagates in the air. The measurements were carried out in an anechoic chamber. Three soils (Endogleyic Umbrisol, Fluvic Endogleyic Cambisol, and Haplic Chernozem) with four initial moisture levels (pressure heads: 0.1 kPa, 1 kPa, 3.16 kPa, and 16 kPa) were tested. Drops of 4.2 mm diameter were falling from a height of 1.5m. The sound pressure level was recorded after 10 consecutive water drop impacts using a special set of microphones. In all measuring conditions with 1m distance, the sound pressure level ranged from 27 to 42dB. The impact of water drops on the ground created sound pulses, which were recalculated to the energy emitted in the form of sound waves. For all soil samples, the sound wave energy was within the range of 0.14 μJ to 5.26 μJ, which corresponds to 0.03-1.07% of the energy of the incident drops (Ryżak et al., 2016). This work was partly financed from the National Science Centre, Poland; project no. 2014/14/E/ST10/00851. References Ryżak M., Bieganowski A., Korbiel T.: Sound wave Energy resulting from the impact of water drops on the soil surface. PLoS One 11(7):e0158472. doi:10.1371/journal.pone.0158472, 2016
Maraghechi, Borna; Hasani, Mojtaba H; Kolios, Michael C; Tavakkoli, Jahan
2016-05-01
Ultrasound-based thermometry requires a temperature-sensitive acoustic parameter that can be used to estimate the temperature by tracking changes in that parameter during heating. The objective of this study is to investigate the temperature dependence of acoustic harmonics generated by nonlinear ultrasound wave propagation in water at various pulse transmit frequencies from 1 to 20 MHz. Simulations were conducted using an expanded form of the Khokhlov-Zabolotskaya-Kuznetsov nonlinear acoustic wave propagation model in which temperature dependence of the medium parameters was included. Measurements were performed using single-element transducers at two different transmit frequencies of 3.3 and 13 MHz which are within the range of frequencies simulated. The acoustic pressure signals were measured by a calibrated needle hydrophone along the axes of the transducers. The water temperature was uniformly increased from 26 °C to 46 °C in increments of 5 °C. The results show that the temperature dependence of the harmonic generation is different at various frequencies which is due to the interplay between the mechanisms of absorption, nonlinearity, and focusing gain. At the transmit frequencies of 1 and 3.3 MHz, the harmonic amplitudes decrease with increasing the temperature, while the opposite temperature dependence is observed at 13 and 20 MHz.
Sajjadi, Shahrdad G; Drullion, Frederique
2014-01-01
A review of three-dimensional waves on deep-water is presented. Three forms of three dimensionality, namely oblique, forced and spontaneous type, are identified. An alternative formulation for these three-dimensional waves is given through cubic nonlinear Schr\\"odinger equation. The periodic solutions of the cubic nonlinear Schr\\"odinger equation are found using Weierstrass elliptic $\\wp$ functions. It is shown that the classification of solutions depends on the boundary conditions, wavenumber and frequency. For certain parameters, Weierstrass $\\wp$ functions are reduced to periodic, hyperbolic or Jacobi elliptic functions. It is demonstrated that some of these solutions do not have any physical significance. An analytical solution of cubic nonlinear Schr\\"odinger equation with wind forcing is also obtained which results in how groups of waves are generated on the surface of deep water in the ocean. In this case the dependency on the energy-transfer parameter, from wind to waves, make either the groups of wav...
Li, Yan
2015-01-01
We obtain a general solution for the water waves resulting from a general, time-dependent surface pressure distribution, in the presence of a shear current of uniform vorticity beneath the surface, in three dimensions. Linearized governing equations and boundary conditions including the effects of gravity, a distributed external pressure disturbance, and constant finite depth, are solved analytically, and particular attention is paid to classic initial value problems: an initial pressure impulse and a steady pressure distribution which appears suddenly. In the present paper, good agreement with previous results is demonstrated. We subsequently show both analytically and numerically how transient waves from a suddenly appearing steady pressure distribution vanis for large times, and steady ship waves remain. The transient contribution to wave resistance was derived. The results show that a shear current has significant impact on the transient wave motions, resulting in asymmetry between upstream and downstream...
Ouyang, Huei-Tau; Chen, Kue-Hong; Tsai, Chi-Ming
2015-11-01
The water wave characteristics of Bragg reflections from a train of fixed floating pontoon breakwaters was studied numerically. A numerical model of boundary discretization type was developed to calculate the wave field. The model was verified by comparing to analytical data in literature and good agreements were achieved. Series of parametric studies were conducted systematically to investigate the dependence of the reflected coefficients by the Bragg scattering on the design variables, including the spacing between the breakwaters, the total number of installed breakwaters, the draft and width do the breakwater, and wave length. Certain wave characteristics of the Bragg reflections were observed and discussed in details which might be of help for practical engineering applications in shoreline protection from incident waves.
Aubourg, Quentin; Mordant, Nicolas
2016-04-01
The theoretical framework of Weak Turbulence describes the statistical properties of a large collection of nonlinear waves. For a weakly nonlinear wave field, energy is assumed to be transferred only trough resonant interaction. This enables the computation of analytical solutions of the stationary statistical states (Zakhaorv spectrum). Some similarities with hydrodynamical turbulence appear : an energy cascade is present from the injection scale to the dissipation at small scales. The theory has been applied to numerous systems many of them being of geophysical or astrophysical nature (water surface waves, internal waves, inertial waves, solar winds) as well as superfluid turbulence, lasers, nonlinear optics in fibers or vibrated elastic plates. For water surface waves, experimental laboratory measurements often fail to reproduce quantitatively theoretical predictions. Gravity waves and capillary waves are often treated separately because of their different nature. For capillary waves, energy is supposed to be transferred trough 3-waves interactions, whereas for gravity waves the coupling involves 4 waves (because of the curvature of the dispersion relation which does not allow triadic solutions). In the laboratory, the range of exited wavelength are usually not strongly separated from the crossover between capillary and gravity waves (which occur near 13 Hz) due to size or measurement limitations. Near this crossover, the dispersion relation is significantly affected and this impacts most likely the theoretical predictions. To investigate how this special point may act on the phenomenology, we report laboratory experiments on gravity-capillary waves focused on the crossover (Aubourg,Mordant-PRL,2015). The setup consists in a 70 ∗ 40 cm2 vessel where waves are generated by horizontal vibration. A Fourier Transform Profilometry technique is used that is fully resolved in time and space and thus permits to compute the full space-time spectrum. The presence of an
Analysis and numerical simulation of the diffusive wave approximation of the shallow water equations
Santillana, Mauricio
In this dissertation, the quantitative and qualitative aspects of modeling shallow water flow driven mainly by gravitational forces and dominated by shear stress, using an effective equation often referred to in the literature as the diffusive wave approximation of the shallow water equations (DSW) are presented. These flow conditions arise for example in overland flow and water flow in vegetated areas such as wetlands. The DSW equation arises in shallow water flow models when special assumptions are used to simplify the shallow water equations and contains as particular cases: the Porous Medium equation and the time evolution of the p-Laplacian. It has been successfully applied as a suitable model to simulate overland flow and water flow in vegetated areas such as wetlands; yet, no formal mathematical analysis has been carried out addressing, for example, conditions for which weak solutions may exist, and conditions for which a numerical scheme can be successful in approximating them. This thesis represents a first step in that direction. The outline of the thesis is as follows. First, a survey of relevant results coming from the studies of doubly nonlinear diffusion equations that can be applied to the DSW equation when topographic effects are ignored, is presented. Furthermore, an original proof of existence of weak solutions using constructive techniques that directly lead to the implementation of numerical algorithms to obtain approximate solutions is shown. Some regularity results about weak solutions are presented as well. Second, a numerical approach is proposed as a means to understand some properties of solutions to the DSW equation, when topographic effects are considered, and conditions for which the continuous and discontinuous Galerkin methods will succeed in approximating these weak solutions are established.
Laboratory Studies of Steep and Breaking Deep Water Waves in a Convergent Channel
2015-05-28
the " young " wave regime. For wave steepnesses between 0.3 < ak < 0.38 the wave profiles became increasingly asymmetric with a steep forward face...Wave Characteristics " Young " waves-symmetric about the crest; Stokes’ fifth-order theory applies. 0.3<akɘ.38 "Pre-breaking" waves-asymmetric waves...careful dynamic calibrations of the offending device. The experiments were conducted at seven wave periods and at a variety of wavemaker strokes as
Cathignol, D; Mestas, J L; Gomez, F; Lenz, P
1991-01-01
In an electrohydraulic generator, two underwater metal electrodes are connected with a capacitor charged to a high voltage. When the circuit is switched on, a plasma is generated reaching temperatures of thousands of K, resulting in a compressive pressure pulse. The formation of the plasma is a nonreproducible phenomenon inducing great variations of the pressure pulse. When the electrodes are immersed in an electrolyte instead of degassed water, the conditions of electrical discharge are dramatically modified. The latency time and the amplitude of the oscillations of the discharge current decrease as the conductivity of the electrolyte increases. For a conductivity of 7 omega.cm, there is no latency, and the critically damped discharge is achieved. The expanding pressure wave is increased by 10%, and the mean peak pressure value over 120 shocks at the second focus after focalization is increased by 50%. The relative standard deviation of the pressure value at the second focus is only 5%, while it is about 30% in ordinary water. The fragmentation efficiency is considerably increased because total fragmentation is obtained in 220 shocks instead of 450 shocks in ordinary water when standard stones are used, and in 131 shocks instead of 304 shocks when gallstones are used. Last, we show that the wear of the electrodes is reduced by a factor 8 when electrolyte is used. The improvement is supposed to have two causes: First, the energy is delivered into the medium in a shorter time, and, second, the center of the shock wave is always located at the same place. The decreased wear should make it possible to treat a much greater number of patients without changing electrodes, and the enhancement of the pressure should increase the efficiency of the fragmentation of the gallstones without aggravating the patient's pain.
Spencer, J. W., Jr.; Nur, A. M.
1976-01-01
A description is presented of an experimental assembly which has been developed to conduct concurrent measurements of compressional and shear wave velocities in rocks at high temperatures and confining pressures and with independent control of the pore pressure. The apparatus was used in studies of the joint effects of temperature, external confining pressure, and internal pore water on sonic velocities in Westerly granite. It was found that at a given temperature, confining pressure has a larger accelerating effect on compressional waves in dry rock, whereas at a given confining pressure, temperature has a larger retarding effect on shear waves.
Institute of Scientific and Technical Information of China (English)
HE Hailun; SONG Jinbao; Patrick J. Lynett; LI Shuang
2009-01-01
Fractional energy losses of waves due to wave breaking when passing over a submerged bar are studied systematically using a modified numerical code that is based on the high-order Boussinesq-type equations. The model is first tested by the additional experimental data, and the model's capability of simulating the wave transformation over both gentle slope and steep slope is demonstrated. Then, the model's breaking index is replaced and tested. The new breaking index, which is optimized from the several breaking indices, is not sensitive to the spatial grid length and includes the bottom slopes. Numerical tests show that the modified model with the new breaking index is more stable and efficient for the shallow-water wave breaking. Finally, the modified model is used to study the fractional energy losses for the regular waves propagating and breaking over a submerged bar. Our results have revealed that how the nonlinearity and the dispersion of the incident waves as well as the dimensionless bar height (normalized by water depth) dominate the fractional energy losses. It is also found that the bar slope (limited to gentle slopes that less than 1:10) and the dimensionless bar length (normalized by incident wave length) have negligible effects on the fractional energy losses.
Institute of Scientific and Technical Information of China (English)
HE Guanghua
2013-01-01
A 3-D iterative Rankine Boundary Element Method (BEM) for seakeeping problem in time domain is developed in the framework of linear potential theory. Waves generated by both submerged and surface-piercing bodies moving at a constant forward speed in otherwise calm water, and the resultant steady wave pattern, wave profile and resistance are computed to validate this newly-developed code. A rectangular computational domain moving with the same forward speed as the body is introduced, in which an artificial damping beach is installed at an outer portion of the free surface except the downstream side for satisfying the radiation condition. The velocity potential on the ship hull and the normal velocity on the free surface are obtained directly by solving the boundary integral equation, with the Rankine source used as the kernel function. An iterative time-marching scheme is employed for updating both kinematic and dynamic free surface boundary conditions to stabilize the calculation. Extensive results including the wave patterns, wave profiles and wave resistances for a submerged spheroid and a Wigley hull with forward speed are presented to validate the efficiency of the proposed 3-D time-domain higher-order approach. Finally, the sensitivity of ship-generated waves to the water depth is investigated. Computed results show satisfactory agreement with the corresponding experimental data and other numerical solutions.
Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter
2016-04-01
The effects of wind waves on the Baltic Sea water temperature has been studied by coupling the hydrodynamical model NEMO with the wave model WAM. The wave forcing terms that have been taken into consideration are: Stokes-Coriolis force, seastate dependent energy flux and sea-state dependent momentum flux. The combined role of these processes as well as their individual contributions on simulated temperature is analysed. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwellinǵs. In northern parts of the Baltic Sea a warming of the surface layer occurs in the wave included simulations. This in turn reduces the cold bias between simulated and measured data. The warming is primarily caused by sea-state dependent energy flux. Wave induced cooling is mostly observed in near coastal areas and is mainly due to Stokes-Coriolis forcing. The latter triggers effect of intensifying upwellings near the coasts, depending on the direction of the wind. The effect of sea-state dependent momentum flux is predominantly to warm the surface layer. During the summer the wave induced water temperature changes were up to 1 °C.
ANALYSIS OF WATER-HAMMER WAVE SPEED IN WATER-IN-OIL EMULSION%油包水型乳化液水击波速的分析
Institute of Scientific and Technical Information of China (English)
张贤明; 吴峰平; 陈彬; 潘诗浪; 张渊博; 王立存
2011-01-01
水击驻波场处理油包水型乳化液是一门新兴工艺,稳定驻波场的存在是破乳的关键,而水击压力波波速在驻波场形成中起着重要的作用。因此,为了更精确的求解水击波速,从W/O型乳化液两相流产生水击现象的特点出发,根据流体力学的连续性原理,推导其水击波波速的表达式,并与经典单相流水击波波速公式进行对比,通过MATLAB仿真分析与对比验证,表明此水击波速公式既适用于单相流水击波速的计算,也适用于两相流水击波速的求解,且W/O型乳化液中含水量越大,其波速就越大。%The application of standing wave field occurred by water-hammer in water-in-oil emulsion is a new technology.And the existence of stable standing wave field is the key to demulsification.The velocity of water-hammer pressure wave plays an important role in the formation of standing wave field.Therefore,in order to solve the water-hammer wave speed more accurately,embarked from the characteristicses of water-hammer produced in W/O emulsion which is the two-phase flow,according to the principle of continuous fluid,the expression of water-hammer wave speed is inferred and is compared with that of classical water-hammer wave speed in single-phase flow.The simulations with MATLAB software and the verifications by contrast indicate that this formula is not only suitable for the water-hammer of single-phase flow,but also the two-phase flow.And the more water it contents in the W/O emulsion,the higher wave speed.
Sousa, Andrew J; Droppo, Ian G; Liss, Steven N; Warren, Lesley; Wolfaardt, Gideon
2015-08-01
The dynamic interaction of bacteria within bed sediment and suspended sediment (i.e., floc) in a wave-dominated beach environment was assessed using a laboratory wave flume. The influence of shear stress (wave energy) on bacterial concentrations and on the partitioning and transport of unattached and floc-associated bacteria was investigated. The study showed that increasing wave energy (0.60 and 5.35 N/s) resulted in a 0.5 to 1.5 log increase in unattached cells of the test bacterium Pseudomonas sp. strain CTO7::gfp-2 in the water column. There was a positive correlation between the bacterial concentrations in water and the total suspended solids, with the latter increasing from values of near 0 to up to 200 mg/L over the same wave energy increase. The median equivalent spherical diameter of flocs in suspension also increased by an order of magnitude in all experimental trials. Under both low (0.60 N/s) and high (5.35 N/s) energy regime, bacteria were shown to preferentially associate with flocs upon cessation of wave activity. The results suggest that collecting water samples during periods of low wave action for the purpose of monitoring the microbiological quality of water may underestimate bacterial concentrations partly because of an inability to account for the effect of shear stress on the erosion and mobilization of bacteria from bed sediment to the water column. This highlights the need to develop a more comprehensive beach analysis strategy that not only addresses presently uncharacterized shores and sediments but also recognizes the importance of eroded flocs as a vector for the transport of bacteria in aquatic environments.
Energy Technology Data Exchange (ETDEWEB)
Chabchoub, A., E-mail: achabchoub@swin.edu.au [Centre for Ocean Engineering Science and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Kibler, B.; Finot, C.; Millot, G. [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS, Université de Bourgogne, 21078 Dijon (France); Onorato, M. [Dipartimento di Fisica, Università degli Studi di Torino, Torino 10125 (Italy); Istituto Nazionale di Fisica Nucleare, INFN, Sezione di Torino, Torino 10125 (Italy); Dudley, J.M. [Institut FEMTO-ST, UMR 6174 CNRS- Université de Franche-Comté, 25030 Besançon (France); Babanin, A.V. [Centre for Ocean Engineering Science and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)
2015-10-15
The dynamics of waves in weakly nonlinear dispersive media can be described by the nonlinear Schrödinger equation (NLSE). An important feature of the equation is that it can be derived in a number of different physical contexts; therefore, analogies between different fields, such as for example fiber optics, water waves, plasma waves and Bose–Einstein condensates, can be established. Here, we investigate the similarities between wave propagation in optical Kerr media and water waves. In particular, we discuss the modulation instability (MI) in both media. In analogy to the water wave problem, we derive for Kerr-media the Benjamin–Feir index, i.e. a nondimensional parameter related to the probability of formation of rogue waves in incoherent wave trains.
Directory of Open Access Journals (Sweden)
Dengfeng Su
2016-01-01
Full Text Available As one of the most serious “side effects” of blast excavation, blast-induced vibration must be controlled for existing buildings and human beings. This paper proposes a method for blast-induced vibration reduction with water jet assistance according to the cutting characters of low-noised, environment-friendly water jet. The mechanism of vibration-isolation with water jet assistance was analyzed, and the stress wave energy attenuation models were established based on blasting theory and stress wave theory. Influence law on shock wave attenuation by vibration-isolation slot was studied by numerical simulation. Simulation results agree with the theoretical analysis roughly. The results of this study put forward a method for blast-induced vibration near blasting source and provide a certain theoretical basis.
Water-hammer pressure waves interaction at cross-section changes in series in viscoelastic pipes
Meniconi, S.; Brunone, B.; Ferrante, M.
2012-08-01
In view of scarcity of both experimental data and numerical models concerning transient behavior of cross-section area changes in pressurized liquid flow, the paper presents laboratory data and numerical simulation of the interaction of a surge wave with a partial blockage by a valve, a single pipe contraction or expansion and a series of pipe contraction/expansion in close proximity.With regard to a single change of cross-section area, laboratory data point out the completely different behavior with respect to one of the partially closed in-line valves with the same area ratio. In fact, for the former the pressure wave interaction is not regulated by the steady-state local head loss. With regard to partial blockages, transient tests have shown that the smaller the length, the more intense the overlapping of pressure waves due to the expansion and contraction in series.Numerically, the need for taking into account both the viscoelasticity and unsteady friction is demonstrated, since the classical water-hammer theory does not simulate the relevant damping of pressure peaks and gives rise to a time shifting between numerical and laboratory data. The transient behavior of a single local head loss has been checked by considering tests carried out in a system with a partially closed in-line valve. As a result, the reliability of the quasi steady-state approach for local head loss simulation has been demonstrated in viscoelastic pipes. The model parameters obtained on the basis of transients carried out in single pipe systems have then been used to simulate transients in the more complex pipe systems. These numerical experiments show the great importance of the length of the small-bore pipe with respect to one of the large-bore pipes. Precisely, until a gradually flow establishes in the small-bore pipe, the smaller such a length, the better the quality of the numerical simulation.
Chakraborty, Rumpa; Mondal, Arpita; Gayen, R.
2016-10-01
In this paper, we present an alternative method to investigate scattering of water waves by a submerged thin vertical elastic plate in the context of linear theory. The plate is submerged either in deep water or in the water of uniform finite depth. Using the condition on the plate, together with the end conditions, the derivative of the velocity potential in the direction of normal to the plate is expressed in terms of a Green's function. This expression is compared with that obtained by employing Green's integral theorem to the scattered velocity potential and the Green's function for the fluid region. This produces a hypersingular integral equation of the first kind in the difference in potential across the plate. The reflection coefficients are computed using the solution of the hypersingular integral equation. We find good agreement when the results for these quantities are compared with those for a vertical elastic plate and submerged and partially immersed rigid plates. New results for the hydrodynamic force on the plate, the shear stress and the shear strain of the vertical elastic plate are also evaluated and represented graphically.
Institute of Scientific and Technical Information of China (English)
YAN Rui; CHEN Yong; GAO Fu-wang; HUANG Fu-qiong
2008-01-01
Based on linear poroelastic theory of ideal poroelastic media, we apply the mathematic expression between pore pressure and volume strain for well-aquifer system to analyzing the observed data of water level and volume strain changes aroused by Sumatra Ms8.7 (determined by China Seismic Networks Center) seismic waves at Changping, Beijing, station on December 26, 2004 from both time and frequency domain. The response coefficients of water level fluctuation to volume strain are also calculated when seismic waves were passing through confined aquifer. A method for estimating Skempton constant B is put forward, which provide an approach for understanding of the characteristics of aquifer.
Comparative Study of Different SPH Schemes on Simulating Violent Water Wave Impact Flows
Institute of Scientific and Technical Information of China (English)
郑兴; 马庆位; 段文洋
2014-01-01
Free surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH (WCSPH) uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH (ISPH) technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.
Comparative study of different SPH schemes on simulating violent water wave impact flows
Zheng, Xing; Ma, Qing-wei; Duan, Wen-yang
2014-12-01
Free surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH (WCSPH) uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH (ISPH) technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.
ABRUPT DEFLECTED SUPERCRITICAL WATER FLOW-REVISED THEORY OF SHOCK WAVE
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The shock wave angle and depth ratio of the abrupt deflected supercritical water flow due to deflector was investigated experimentally and theoretically. A correction coefficient of the hydro-dynamic pressure ξ was introduced to generalize the momentum equation in the perpendicular direction to the shock front. An extensive series of tests were conducted in a 1 m wide flume with the Froude number ranging from 1.70 to 8.37, the deflection angle ranging from 5° to 40° and the length of deflector ranging from 0.28 m to 1 m. A dimensionless parameter K was defined to depict the ratio of the flow height to flow thickness. Test results show that the value of ξ, the correction coefficient of the non-hydrostatic pressure distribution, decreases with the increase of the value of K. An empirical relationship between the value of ξ and the value of K was proposed. It is indicated that the relative errors of the results calculated by the revised theory is much smaller than that obtained from the Ippen theory. Finally, a simple explicit expression was suggested to calculate the shock wave height ratio in consideration of the effect of the non-hydrostatic pressure distribution.
Froude, Melanie; Alexander, Jan; Cole, Paul; Barclay, Jenni
2014-05-01
On 13-14 October 2012, Tropical Storm Rafael triggered sediment-laden flash floods in the Belham Valley on Montserrat, West Indies. Rainfall was continuous for ~38 hours and intensity peaked at 48 mm/hr. Flow was strongly unsteady, turbulent with sediment concentrations varying up to hyperconcentrated. Time-lapse images captured at >1 frame per second by remote camera overlooking a surveyed valley section show the development of trains of water surface waves at multiple channel locations during different flow stages. Waves grew and diminished in height and remained stationary or migrated upstream. Trains of waves persisted for <5 minutes, until a single wave broke, sometimes initiating the breaking of adjacent waves within the train. Channel-wide surges (bores) propagating downstream with distinct turbulent flow fronts, were observed at irregular intervals during and up to 7 hours after peak stage. These bores are mechanically similar to breaking front tidal bores and arid flood bores, and resulted in a sudden increase in flow depth and velocity. When a bore front came into close proximity (within ~10 m) upstream of a train of water surface waves, the waves appeared to break simultaneously generating a localised surge of water upstream, that was covered by the bore travelling downstream. Those trains in which waves did not break during the passage of a bore temporarily reduced in height. In both cases, water surface waves reformed immediately after the surge in the same location. Deposits from the event, were examined in <4 m deep trenches ~0.5 km downstream of the remote camera. These contained laterally extensive lenticular and sheet-like units comprised of varying admixtures of sand and gravel that are attributed to antidunes, and associated transitions from upper-stage-plane-beds. Some of the structures are organised within concave upward sequences which contain downflow shifts between foreset and backset laminae; interpreted as trough fills from chute
Microwave and Millimeter-Wave Radiometric Studies of Temperature, Water Vapor and Clouds
Energy Technology Data Exchange (ETDEWEB)
Westwater, Edgeworth
2011-05-06
The importance of accurate measurements of column amounts of water vapor and cloud liquid has been well documented by scientists within the Atmospheric Radiation Measurement (ARM) Program. At the North Slope of Alaska (NSA), both microwave radiometers (MWR) and the MWRProfiler (MWRP), been used operationally by ARM for passive retrievals of the quantities: Precipitable Water Vapor (PWV) and Liquid Water Path (LWP). However, it has been convincingly shown that these instruments are inadequate to measure low amounts of PWV and LWP. In the case of water vapor, this is especially important during the Arctic winter, when PWV is frequently less than 2 mm. For low amounts of LWP (< 50 g/m{sup 2}), the MWR and MWRP retrievals have an accuracy that is also not acceptable. To address some of these needs, in March-April 2004, NOAA and ARM conducted the NSA Arctic Winter Radiometric Experiment - Water Vapor Intensive Operational Period at the ARM NSA/Adjacent Arctic Ocean (NSA/AAO) site. After this experiment, the radiometer group at NOAA moved to the Center for Environmental Technology (CET) of the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. During this 2004 experiment, a total of 220 radiosondes were launched, and radiometric data from 22.235 to 380 GHz were obtained. Primary instruments included the ARM MWR and MWRP, a Global Positioning System (GPS), as well as the CET Ground-based Scanning Radiometer (GSR). We have analyzed data from these instruments to answer several questions of importance to ARM, including: (a) techniques for improved water vapor measurements; (b) improved calibration techniques during cloudy conditions; (c) the spectral response of radiometers to a variety of conditions: clear, liquid, ice, and mixed phase clouds; and (d) forward modeling of microwave and millimeter wave brightness temperatures from 22 to 380 GHz. Many of these results have been published in the open literature. During the third year of
Forcing of a bottom-mounted circular cylinder by steep regular water waves at finite depth
DEFF Research Database (Denmark)
Paulsen, Bo Terp; Bredmose, Henrik; Bingham, Harry B.
2014-01-01
Forcing by steep regular water waves on a vertical circular cylinder at finite depth was investigated numerically by solving the two-phase incompressible Navier–Stokes equations. Consistently with potential flow theory, boundary layer effects were neglected at the sea bed and at the cylinder...... surface, but the strong nonlinear motion of the free surface was included. The numerical model was verified and validated by grid convergence and by comparison to relevant experimental measurements. First-order convergence towards an analytical solution was demonstrated and an excellent agreement...... of secondary load cycles. Special attention was paid to this secondary load cycle and the flow features that cause it. By visual observation and a simplified analytical model it was shown that the secondary load cycle was caused by the strong nonlinear motion of the free surface which drives a return flow...
Numerical Study of Viscous Wave-Making Resistance of Ship Navigation in Still Water
Institute of Scientific and Technical Information of China (English)
Decheng Wan
2014-01-01
The prediction of a ship’s resistance especially the viscous wave-making resistance is an important issue in CFD applications. In this paper, the resistances of six ships from hull 1 to hull 6 with different hull forms advancing in still water are numerically studied using the solver naoe-FOAM-SJTU, which was developed based on the open source code package OpenFOAM. Different components of the resistances are computed and compared while considering two speed conditions (12 kn and 16 kn). The resistance of hull 3 is the smallest while that of hull 5 is the largest at the same speed. The results show hull 3 is a good reference for the design of similar ships, which can provide some valuable guidelines for hull form optimization.
Stationary shapes for 2-d water-waves and hydraulic jumps
Fontelos, M. A.; Lecaros, R.; López-Ríos, J. C.; Ortega, J. H.
2016-08-01
A hydraulic jump is a physical phenomenon commonly observed in nature such as in open channel flows or spillways and is dependent upon the relation between the initial upstream fluid speed and a critical speed characterized by a dimensionless number F known as the Froude number. In this paper we prove the existence of hydraulic jumps for stationary water-waves as a consequence of the existence of bifurcation branches of non-flat liquid interfaces originated from each of a sequence of upstream velocities F1 > F2 > ⋯ > Fr > ⋯ (Fr → 0 as r → ∞). We further establish explicitly, for F > 0, F≠Fr, r ∈ ℕ, the existence and uniqueness of the solution of a perfect, incompressible, irrotational free surface flow over a flat bottom, under the influence of gravity; as well as the corresponding hydraulic jump.
Harvesting broadband kinetic impact energy from mechanical triggering/vibration and water waves.
Wen, Xiaonan; Yang, Weiqing; Jing, Qingshen; Wang, Zhong Lin
2014-07-22
We invented a triboelectric nanogenerator (TENG) that is based on a wavy-structured Cu-Kapton-Cu film sandwiched between two flat nanostructured PTFE films for harvesting energy due to mechanical vibration/impacting/compressing using the triboelectrification effect. This structure design allows the TENG to be self-restorable after impact without the use of extra springs and converts direct impact into lateral sliding, which is proved to be a much more efficient friction mode for energy harvesting. The working mechanism has been elaborated using the capacitor model and finite-element simulation. Vibrational energy from 5 to 500 Hz has been harvested, and the generator's resonance frequency was determined to be ∼100 Hz at a broad full width at half-maximum of over 100 Hz, producing an open-circuit voltage of up to 72 V, a short-circuit current of up to 32 μA, and a peak power density of 0.4 W/m(2). Most importantly, the wavy structure of the TENG can be easily packaged for harvesting the impact energy from water waves, clearly establishing the principle for ocean wave energy harvesting. Considering the advantages of TENGs, such as cost-effectiveness, light weight, and easy scalability, this approach might open the possibility for obtaining green and sustainable energy from the ocean using nanostructured materials. Lastly, different ways of agitating water were studied to trigger the packaged TENG. By analyzing the output signals and their corresponding fast Fourier transform spectra, three ways of agitation were evidently distinguished from each other, demonstrating the potential of the TENG for hydrological analysis.
Directory of Open Access Journals (Sweden)
N. Stashchuk
2005-01-01
Full Text Available We present the results of numerical experiments performed with the use of a fully non-linear non-hydrostatic numerical model to study the baroclinic response of a long narrow tank filled with stratified water to an initially tilted interface. Upon release, the system starts to oscillate with an eigen frequency corresponding to basin-scale baroclinic gravitational seiches. Field observations suggest that the disintegration of basin-scale internal waves into packets of solitary waves, shear instabilities, billows and spots of mixed water are important mechanisms for the transfer of energy within stratified lakes. Laboratory experiments performed by D. A. Horn, J. Imberger and G. N. Ivey (JFM, 2001 reproduced several regimes, which include damped linear waves and solitary waves. The generation of billows and shear instabilities induced by the basin-scale wave was, however, not sufficiently studied. The developed numerical model computes a variety of flows, which were not observed with the experimental set-up. In particular, the model results showed that under conditions of low dissipation, the regimes of billows and supercritical flows may transform into a solitary wave regime. The obtained results can help in the interpretation of numerous observations of mixing processes in real lakes.
Estrada, Héctor; Rebling, Johannes; Razansky, Daniel
2017-02-01
The skull bone, a curved solid multilayered plate protecting the brain, constitutes a big challenge for the use of ultrasound-mediated techniques in neuroscience. Ultrasound waves incident from water or soft biological tissue are mostly reflected when impinging on the skull. To this end, skull properties have been characterized for both high-intensity focused ultrasound (HIFU) operating in the narrowband far-field regime and optoacoustic imaging applications. Yet, no study has been conducted to characterize the near-field of water immersed skulls. We used the thermoelastic effect with a 532 nm pulsed laser to trigger a wide range of broad-band ultrasound modes in a mouse skull. In order to capture the waves propagating in the near-field, a thin hydrophone was scanned in close proximity to the skull's surface. While Leaky pseudo-Lamb waves and grazing-angle bulk water waves are clearly visible in the spatio-temporal data, we were only able to identify skull-guided acoustic waves after dispersion analysis in the wavenumber-frequency space. The experimental data was found to be in a reasonable agreement with a flat multilayered plate model.
Raghukumar, Kaustubha; Colosi, John A
2015-05-01
In an earlier article, the statistical properties of mode propagation were studied at a frequency of 1 kHz in a shallow water environment with random sound-speed perturbations from linear internal waves, using a hybrid transport theory and Monte Carlo numerical simulations. Here, the analysis is extended to include the effects of random linear surface waves, in isolation and in combination with internal waves. Mode coupling rates for both surface and internal waves are found to be significant, but strongly dependent on mode number. Mode phase randomization by surface waves is found to be dominated by coupling effects, and therefore a full transport theory treatment of the range evolution of the cross mode coherence matrix is needed. The second-moment of mode amplitudes is calculated using transport theory, thereby providing the mean intensity while the fourth-moment is calculated using Monte Carlo simulations, which provides the scintillation index. The transport theory results for second-moment statistics are shown to closely reproduce Monte Carlo simulations. Both surface waves and internal waves strongly influence the acoustic field fluctuations.
Shi, Chuanqi; An, Yi; Wu, Qiang; Liu, Qingquan; Cao, Zhixian
2016-06-01
We simulate the generation of a landslide-induced impulse wave with a newly-developed soil-water coupling model in the smoothed particle hydrodynamics (SPH) framework. The model includes an elasto-plastic constitutive model for soil, a Navier-Stokes equation based model for water, and a bilateral coupling model at the interface. The model is tested with simulated waves induced by a slow and a fast landslide. Good agreement is obtained between simulation results and experimental data. The generated wave and the deformation of the landslide body can both be resolved satisfactorily. All parameters in our model have their physical meaning in soil mechanics and can be obtained from conventional soil mechanics experiments directly. The influence of the dilatancy angle of soil shows that the non-associated flow rule must be selected, and the value of the dilatancy angle should not be chosen arbitrarily, if it is not determined with relative experiments.
A study of rain effects on radar scattering from water waves
Bliven, Larry F.; Giovanangeli, Jean-Paul; Norcross, George
1988-01-01
Results are presented from a laboratory investigation of microwave power return due to rain-generated short waves on a wind wave surface. The wind wave tank, sensor, and data processing methods used in the study are described. The study focuses on the response of a 36-GHz radar system, orientated 30 deg from nadir and pointing upwind, to surface waves generated by various combinations of rain and wind. The results show stronger radar signal levels due to short surface waves generated by rain impacting the wind wave surface, supporting the results of Moore et al. (1979) for a 14-GHz radar.
Fully Nonlinear Boussinesq-Type Equations with Optimized Parameters for Water Wave Propagation
Institute of Scientific and Technical Information of China (English)
荆海晓; 刘长根; 龙文; 陶建华
2015-01-01
For simulating water wave propagation in coastal areas, various Boussinesq-type equations with improved properties in intermediate or deep water have been presented in the past several decades. How to choose proper Boussinesq-type equations has been a practical problem for engineers. In this paper, approaches of improving the characteristics of the equations, i.e. linear dispersion, shoaling gradient and nonlinearity, are reviewed and the advantages and disadvantages of several different Boussinesq-type equations are compared for the applications of these Boussinesq-type equations in coastal engineering with relatively large sea areas. Then for improving the properties of Boussinesq-type equations, a new set of fully nonlinear Boussinseq-type equations with modified representative velocity are derived, which can be used for better linear dispersion and nonlinearity. Based on the method of minimizing the overall error in different ranges of applications, sets of parameters are determined with optimized linear dispersion, linear shoaling and nonlinearity, respectively. Finally, a test example is given for validating the results of this study. Both results show that the equations with optimized parameters display better characteristics than the ones obtained by matching with padé approximation.
Fully nonlinear Boussinesq-type equations with optimized parameters for water wave propagation
Jing, Hai-xiao; Liu, Chang-gen; Long, Wen; Tao, Jian-hua
2015-06-01
For simulating water wave propagation in coastal areas, various Boussinesq-type equations with improved properties in intermediate or deep water have been presented in the past several decades. How to choose proper Boussinesq-type equations has been a practical problem for engineers. In this paper, approaches of improving the characteristics of the equations, i.e. linear dispersion, shoaling gradient and nonlinearity, are reviewed and the advantages and disadvantages of several different Boussinesq-type equations are compared for the applications of these Boussinesq-type equations in coastal engineering with relatively large sea areas. Then for improving the properties of Boussinesq-type equations, a new set of fully nonlinear Boussinseq-type equations with modified representative velocity are derived, which can be used for better linear dispersion and nonlinearity. Based on the method of minimizing the overall error in different ranges of applications, sets of parameters are determined with optimized linear dispersion, linear shoaling and nonlinearity, respectively. Finally, a test example is given for validating the results of this study. Both results show that the equations with optimized parameters display better characteristics than the ones obtained by matching with padé approximation.
Approximate solutions of some problems of scattering of surface water waves by vertical barriers
Indian Academy of Sciences (India)
A CHOUDHARY; S C MARTHA
2017-05-01
A class of mixed boundary value problems (bvps), occurring in the study of scattering of surface water waves by thin vertical rigid barriers placed in water of finite depth, is examined for their approximate solutions. Two different placings of vertical barriers are analyzed, namely, (i) a partially immersed barrier and(ii) a bottom standing barrier. The solutions of the bvps are obtained by utilizing the eigenfunction expansion method, leading to a mathematical problem of solving over-determined systems of linear algebraic equations. The methods of analytical least-square approximation as well as algebraic least-square approximation are employed to solve the corresponding over-determined system of linear algebraic equations and thereby evaluate the physical quantities, namely, the reflection and transmission coefficients. Further, the absolute values of the reflection coefficients are compared to the known results obtained by utilizing a Galerkin type of approximate method after reducing the bvps to integral equations whose complete solutions are difficult to be determined.Various combinations of discretization of the resulting dual series relations obtained in the present analysis are employed to determine the least-square solution.
On freely floating bodies trapping time-harmonic waves in water covered by brash ice
Kuznetsov, Nikolay
2015-01-01
A mechanical system consisting of water covered by brash ice and a body freely floating near equilibrium is considered. The water occupies a half-space into which an infinitely long surface-piercing cylinder is immersed, thus allowing us to study two-dimensional modes of the coupled motion which is assumed to be of small amplitude. The corresponding linear setting for time-harmonic oscillations reduces to a spectral problem whose parameter is the frequency. A constant that characterises the brash ice divides the set of frequencies into two subsets and the results obtained for each of these subsets are essentially different. For frequencies belonging to a finite interval adjacent to zero, the total energy of motion is finite and the equipartition of energy holds for the whole system. For every frequency from this interval, a family of motionless bodies trapping waves is constructed by virtue of the semi-inverse procedure. For sufficiently large frequencies outside of this interval, all solutions of finite ener...
A Numerical Study on Water Waves Generated by A Submerged Moving Body in A Two-Layer Fluid System
Institute of Scientific and Technical Information of China (English)
YANG Jia-Zhen; NG Chiu-On; ZHANG Dao-Hua
2009-01-01
This is a numerical study on the time development of surface waves generated by a submerged body moving steadily in a two-layer fluid system, in which a layer of water is underlain by a layer of viscous mud. The fully nonlinear Navier-Stokes equations are solved on FLUENT with the Volume-of-Fluid (VOF) multiphase scheme in order to simulate the free surface waves as well as the water-mud interface waves as functions of time. The numerical model is validated by mimick-ing a reported experiment in a one-layer system before it is applied to a two-layer system, it is found that the presence of bottom mud in a water layer can lead to large viscous damping of the surface waves. For the investigation of the problem systematically, the effects of the Froude number and the mud layer thickness, density and viscosity relative to those of water are evaluated and discussed in detail.
Proceedings, Nonlinear Water Waves Workshop Held at the University of Bristol on October 22-25, 1991
1991-01-01
France/SCEM 75340 Paris France £hrdi sman uif I.M.S.T. 13288 Marseille France 1. Introduction Evolution of trains of surface gravity waves has been...finite amplitude in deep water. ISuper -harmonics; UiSub-hamonics. Proc. R. Soc. Lond. A360: 471-505. McLean. J.W. et al. 1981. Three dimensinal
Luo, Cong; Li, Xiangyang; Huang, Guangtan
2017-08-01
Oil-water discrimination is of great significance in the design and adjustment of development projects in oil fields. For fractured reservoirs, based on anisotropic S-wave splitting information, it becomes possible to effectively solve such problems which are difficult to deal with in traditional longitudinal wave exploration, due to the similar bulk modulus and density of these two fluids. In this paper, by analyzing the anisotropic character of the Chapman model (2009 Geophysics 74 97-103), the velocity and reflection coefficient differences between the fast and slow S-wave caused by fluid substitution have been verified. Then, through a wave field response analysis of the theoretical model, we found that water saturation causes a longer time delay, a larger time delay gradient and a lower amplitude difference between the fast and slow S-wave, while the oil case corresponds to a lower time delay, a lower gradient and a higher amplitude difference. Therefore, a new class attribute has been proposed regarding the amplitude energy of the fast and slow shear wave, used for oil-water distinction. This new attribute, as well as that of the time delay gradient, were both applied to the 3D3C seismic data of carbonate fractured reservoirs in the Luojia area of the Shengli oil field in China. The results show that the predictions of the energy attributes are more consistent with the well information than the time delay gradient attribute, hence demonstrating the great advantages and potential of this new attribute in oil-water recognition.
Xia, Ya-Rong; Xin, Xiang-Peng; Zhang, Shun-Li
2017-01-01
This paper mainly discusses the (2+1)-dimensional modified dispersive water-wave (MDWW) system which will be proved nonlinear self-adjointness. This property is applied to construct conservation laws corresponding to the symmetries of the system. Moreover, via the truncated Painlevé analysis and consistent tanh-function expansion (CTE) method, the soliton-cnoidal periodic wave interaction solutions and corresponding images will be eventually achieved. Supported by National Natural Science Foundation of China under Grant Nos. 11371293, 11505090, the Natural Science Foundation of Shaanxi Province under Grant No. 2014JM2-1009, Research Award Foundation for Outstanding Young Scientists of Shandong Province under Grant No. BS2015SF009 and the Science and Technology Innovation Foundation of Xi’an under Grant No. CYX1531WL41
Benetazzo, A.; Bergamasco, A.; Bonaldo, D.; Falcieri, F. M.; Sclavo, M.; Langone, L.; Carniel, S.
2014-11-01
The paper describes formation and spreading of dense shelf waters in the Adriatic Sea (North Adriatic Dense Water, NAdDW) during the winter of 2012 as a consequence of an intense and long cold air outbreak of northeasterly Bora winds. As a result, during February 2012 northern Adriatic Sea water temperature dropped to about 6 °C and density exceeded 1030 kg/m3, most likely the maximum value since 1929. NAdDW dynamics has been investigated by means of a 3-D ocean-wave coupled model running on a high resolution and eddy-permitting grid. The numerical experiments have relied on the Coupled-Ocean-Atmosphere-Wave-Sediment-Transport (COAWST) system forced one-way with atmospheric forcings provided by the model COSMO-I7. A suite of observational data has been used to characterize the Bora event and evaluate numerical model performance. At sub-basin scales, the newly formed waters flowing southerly have produced a water renewal of the northern Adriatic, as more than 50% of water volumes have left the basin. Dense waters volume transports, evaluated through different Adriatic cross-sections, have been modulated by tides (damped for the densest water masses) and reached about 1 Sv. The contribution of wave-induced forcings has been quantified and examined, indicating that these represent a major driving mechanism during NAdDW production and spreading phases. This work provides evidence that NAdDW is spread accordingly with two different mechanisms: at early stages of its formation, the wind-driven ocean circulation pushes newly formed waters to leave the northern basin with relatively high speeds (about 0.30 m/s). Later on, remaining NAdDW leaks slowly out (0.09 m/s as average) from the production site. Residence times of dense waters in the north, middle, and south Adriatic Sea are also documented.
Tang, Hao; Zhang, Hui; Xie, Fei; Xu, Chi; Wang, Lei; Liu, Mao-Song
2012-06-01
Riparian ecological restoration engineering with offshore wave-elimination weir is an engineering measure with piled wave-elimination weir some meters away from the shore. This measure can dissipate waves, promote sediment deposition, and create an artificial semi-closed bay to restore vegetation in a riparian area which has hard dam and destroyed vegetation. Three habitat gradient zones, i. e., emerged vegetation zone, submerged vegetation zone, and open water area, can be formed after this engineering. In June 2010-May 2011, a field investigation was conducted on the water quality in the three zones in an ecological restoration area of Gonghu Bay, Taihu Lake. The water body inside the weir generally had lower concentrations of nitrite and nitrate but higher concentrations of ammonium and total nitrogen than the water body outside the weir. The water phosphorus concentration inside the weir was lower than that outside the weir in autumn and winter, while an opposite trend was observed in spring and summer. The coefficients of variation of the water body' s nitrite and orthophosphate concentration inside the weir decreased, and the annual maximum values of the water nitrite, nitrate, and orthophosphate concentrations inside the weir were lower than those outside the weir. On the contrary, the coefficients of variation of the water body's ammonium and total nitrogen concentrations inside the weir increased, and the annual maximum values of the water ammonium and total nitrogen concentrations inside the weir were higher than those outside the weir. To some extent, the restoration engineering could exacerbate the deterioration of the water quality indices such as ammonium and total nitrogen in the restoration area by the end of growth season
Droghei, Riccardo; Falcini, Federico; Martorelli, Eleonora; Casalbore, Daniele; Mosetti, Renzo; Salusti, Ettore; Sannino, Gianmaria; Santoleri, Rosalia; Chiocci, Francesco
2016-04-01
Joint marine geology and physical oceanography studies seek to demonstrate the inherited connection between seafloor sedimentary processes and seawater dynamics in a fruitful exchange. While seafloor morphology highlights the long-term action of bottom currents, oceanographic models attempt to explain and predict morphogenetic processes and sedimentary pattern at the seafloor [Blodeaux, 2001; Martorelli et al., 2010; Belde et al., 2015]. A sand waves field we observed off the Messina Strait (Mediterranean Sea) give us the opportunity to demonstrate the value of such a multidisciplinary approach. We interpret these sand-waves as formed by tidal-induced internal solitary waves (ISWs) that generate within the Strait [Alpers and Salusti, 1983; Sapia and Salusti; 1987; Artale et al., 1990; Bradt et al., 1999]. We hypothesize that the deflected pattern (i.e., the depth-dependent orientation) of these sand waves is due to refraction of ISWs occurring at the interface between the Levantine Intermediate Water (LIW) and the Modified Atlantic Water (MAW), caused by interaction with a topographic mound; while the motion of sediment is caused by the bottom velocity field associated with the ISW trough. Both numerical and in situ data provide hints regarding the formation of the observed geometries and give useful information about their dynamics and migration rate. We believe that our work represents an innovative and promising link between the geological and oceanographic communities, adding some insights on the role of ISWs on sedimentary process and the structure of continental margins [Puig et al, 2004; Haren et al., 2013]. References: Blondeaux, P. (2001). Mechanics of coastal forms. Annual Review of Fluid Mechanics, 33(1), 339-370. Martorelli, E., Falcini, F., Salusti, E., & Chiocci, F. L. (2010). Analysis and modeling of contourite drifts and contour currents off promontories in the Italian Seas (Mediterranean Sea). Marine Geology, 278(1), 19-30. Belde, J., Back, S
Chekanov, V. V.; Kandaurova, N. V.; Chekanov, V. S.
2014-09-01
A variation in the reflection coefficient of an interface of two liquids (water and magnetic liquid) in the presence of an electric field is experimentally studied. An increase in the reflection coefficient of the interface is demonstrated. A surface instability of the water-magnetic liquid interface, the wave motion at the interface, and wave interference are observed.
Initial-Boundary Value Problem Solution of the Nonlinear Shallow-water Wave Equations
Kanoglu, U.; Aydin, B.
2014-12-01
The hodograph transformation solutions of the one-dimensional nonlinear shallow-water wave (NSW) equations are usually obtained through integral transform techniques such as Fourier-Bessel transforms. However, the original formulation of Carrier and Greenspan (1958 J Fluid Mech) and its variant Carrier et al. (2003 J Fluid Mech) involve evaluation integrals. Since elliptic integrals are highly singular as discussed in Carrier et al. (2003), this solution methodology requires either approximation of the associated integrands by smooth functions or selection of regular initial/boundary data. It should be noted that Kanoglu (2004 J Fluid Mech) partly resolves this issue by simplifying the resulting integrals in closed form. Here, the hodograph transform approach is coupled with the classical eigenfunction expansion method rather than integral transform techniques and a new analytical model for nonlinear long wave propagation over a plane beach is derived. This approach is based on the solution methodology used in Aydın & Kanoglu (2007 CMES-Comp Model Eng) for wind set-down relaxation problem. In contrast to classical initial- or boundary-value problem solutions, here, the NSW equations are formulated to yield an initial-boundary value problem (IBVP) solution. In general, initial wave profile with nonzero initial velocity distribution is assumed and the flow variables are given in the form of Fourier-Bessel series. The results reveal that the developed method allows accurate estimation of the spatial and temporal variation of the flow quantities, i.e., free-surface height and depth-averaged velocity, with much less computational effort compared to the integral transform techniques such as Carrier et al. (2003), Kanoglu (2004), Tinti & Tonini (2005 J Fluid Mech), and Kanoglu & Synolakis (2006 Phys Rev Lett). Acknowledgments: This work is funded by project ASTARTE- Assessment, STrategy And Risk Reduction for Tsunamis in Europe. Grant 603839, 7th FP (ENV.2013.6.4-3 ENV
Waves in shallow water off west coast of India during the onset of summer monsoon
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Philip, C.S.; Nair, T.N.B.
and south-west and the balance was due to the seas from south-west to north-west. Wave age of the measured data indicates that the measured waves are young sea with presence of swells. Even when the wind speed reduced to less than 3 m/s, significant wave...
de Bakker, A.T.M.
2016-01-01
Infragravity waves (20-200 s) receive their energy from sea-swell waves (2-20 s), and are thought to be important to beach erosion during storms, when they can reach up to several meters in height. Numerous studies have observed that on sandy beaches infragravity waves can lose a large part of their
Distribution of deep water wave power around the Indian coast based on ship observations
Digital Repository Service at National Institute of Oceanography (India)
Chandramohan, P.; Nayak, B.U.; RamaRaju, V.S.
distribution of wave power in different directions over a year for each grid is presented. The annual mean wave power along the Indian coast varies from 11.4 to 15.2 KW per metre length of wave crest with a maximum of 15.2 KW for the regions off south Kerala...
de Bakker, A.T.M.
2016-01-01
Infragravity waves (20-200 s) receive their energy from sea-swell waves (2-20 s), and are thought to be important to beach erosion during storms, when they can reach up to several meters in height. Numerous studies have observed that on sandy beaches infragravity waves can lose a large part of their
Selection and formulation of a numerical shallow water wave hindcast model
Holthuijsen, L.H.; Booij, N.
1983-01-01
Formulate a numerical wave hindcast model which can be used to obtain realistic estimates of wave conditions in the Oosterschelde as input to a numerical geomorphological model. A directionally decoupled, parametric wave hindeast model is recommended that includes parameterized versions of conventi
Diffraction of Oblique Water Waves by Small Uneven Channel-bed in a Two-layer Fluid
Institute of Scientific and Technical Information of China (English)
Smrutiranjan Mohapatra
2014-01-01
Obliquely incident water wave scattering by an uneven channel-bed in the form of a small bottom undulation in a two-layer fluid is investigated within the frame work of three-dimensional linear water wave theory. The upper fluid is assumed to be bounded above by a rigid lid, while the lower one is bounded below by a bottom surface having a small deformation and the channel is unbounded in the horizontal directions. Assuming irrotational motion, perturbation technique is employed to calculate the first-order corrections to the velocity potentials in the two fluids by using Fourier transform approximately, and also to calculate the reflection and transmission coefficients in terms of integrals involving the shape function representing the bottom deformation. Consideration of a patch of sinusoidal ripples shows that the reflection coefficient is an oscillatory function of the ratio of twice the component of the wave number along x-axis and the ripple wave number. When this ratio approaches one, the theory predicts a resonant interaction between the bed and interface, and the reflection coefficient becomes a multiple of the number of ripples. High reflection of incident wave energy occurs if this number is large.
Diffraction of oblique water waves by small uneven channel-bed in a two-layer fluid
Mohapatra, Smrutiranjan
2014-09-01
Obliquely incident water wave scattering by an uneven channel-bed in the form of a small bottom undulation in a two-layer fluid is investigated within the frame work of three-dimensional linear water wave theory. The upper fluid is assumed to be bounded above by a rigid lid, while the lower one is bounded below by a bottom surface having a small deformation and the channel is unbounded in the horizontal directions. Assuming irrotational motion, perturbation technique is employed to calculate the first-order corrections to the velocity potentials in the two fluids by using Fourier transform approximately, and also to calculate the reflection and transmission coefficients in terms of integrals involving the shape function representing the bottom deformation. Consideration of a patch of sinusoidal ripples shows that the reflection coefficient is an oscillatory function of the ratio of twice the component of the wave number along x-axis and the ripple wave number. When this ratio approaches one, the theory predicts a resonant interaction between the bed and interface, and the reflection coefficient becomes a multiple of the number of ripples. High reflection of incident wave energy occurs if this number is large.
Chatelain, Mathieu; Guizien, Katell
2010-03-01
A one-dimensional vertical unsteady numerical model for diffusion-consumption of dissolved oxygen (DO) above and below the sediment-water interface was developed to investigate DO profile dynamics under wind waves and sea swell (high-frequency oscillatory flows with periods ranging from 2 to 30s). We tested a new approach to modelling DO profiles that coupled an oscillatory turbulent bottom boundary layer model with a Michaelis-Menten based consumption model. The flow regime controls both the mean value and the fluctuations of the oxygen mass transfer efficiency during a wave cycle, as expressed by the non-dimensional Sherwood number defined with the maximum shear velocity (Sh). The Sherwood number was found to be non-dependent on the sediment biogeochemical activity (mu). In the laminar regime, both cycle-averaged and variance of the Sherwood number are very low (Sh wave cycle fluctuations that increase with the wave Reynolds number (VAR(Sh) up to 30%). Our computations show that DO mass transfer efficiency under high-frequency oscillatory flows in the turbulent regime are water-side controlled by: (a) the diffusion time across the diffusive boundary layer and (b) diffusive boundary layer dynamics during a wave cycle. As a result of these two processes, when the wave period decreases, the Sh minimum increases and the Sh maximum decreases. Sh values vary little, ranging from 0.17 to 0.23. For periods up to 30s, oxygen penetration depth into the sediment did not show any intra-wave fluctuations. Values for the laminar regime are small (
Liquid Water through Density-Functional Molecular Dynamics: Plane-Wave vs Atomic-Orbital Basis Sets
Miceli, Giacomo; Pasquarello, Alfredo
2016-01-01
We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that implementations with plane-wave or atomic-orbital basis sets yield equivalent results and can be used indiscriminately in study of liquid water or aqueous solutions.
Long, S. R.; Huang, N. E.
1976-01-01
Laboratory measurements utilizing a laser probe are made for the slopes of wind waves generated on both positive and negative currents at different values of fetch. The data are then processed electronically to yield an average wave-slope spectrum in frequency space with 128 degrees of freedom. These spectra are used to obtain the growth of the spectral components at various frequency bands for increasing wind and different values of fetch and current. The results indicate that the growth of these components is not monotonic with the frictional wind speed, but rather exhibits an 'overshoot' phenomena at lower values of frictional wind speed, and in addition, displays a significant effect due to current. The peak location and spectral intensity of the spectra also show strong influence by the current condition. This results in the rms surface slope value increasing with negative current and decreasing with positive current. The results agree qualitatively with some theoretical predictions. The potential use of the current-induced effects as a means for remote sensing of ocean current is also briefly discussed.
Zheng, Jun; Li, Ruijie; Yu, Yonghai; Suo, Anning
2014-01-01
In nearshore waters, spatial and temporal scales of waves, tidal currents, and circulation patterns vary greatly. It is, therefore, difficult to combine these factors' effects when trying to predict sediment transport processes. This paper proposes the concept of significant wave velocity, which combines the effects of waves, tides, and ocean currents using the horizontal kinetic energy superposition principle. Through a comparison of the relationship between shear stress at the water-sediment interface and sediment-carrying capacity, assuming equilibrium sediment flux, a new formula for sediment-carrying capacity, which incorporates the concept of significant wave velocities, is derived. Sediment-carrying capacity is a function of the critical velocity, which increases with water depth and decreases with increasing relative roughness of the sea bed. Finally, data from field observation stations and simulations are used to test the proposed formula. The results show that the new formula is in good agreement with both field and simulation data. This new formula for sediment-carrying capacity can be used to simulate nearshore sediment transport.
Directory of Open Access Journals (Sweden)
W. W. Verstraeten
2005-01-01
Full Text Available This paper focuses on the quantification of the green – vegetation related – water flux of forest stands in the temperate lowland of Flanders. The underlying reason of the research was to develop a methodology for assessing the impact of forests on the hydrologic cycle in comparison to agriculture. The tested approach for calculating the water use by forests was based on the application of the soil water balance model WAVE. The study involved the collection of data from 14 forest stands, the calibration and validation of the WAVE model, and the comparison of the water use (WU components – transpiration, soil and interception evaporation – between forest and cropland. For model calibration purposes simulated and measured time series of soil water content at different soil depths, period March 2000–August 2001, were compared. A multiple-site validation was conducted as well. Actual tree transpiration calculated with sap flow measurements in three forest stands gave similar results for two of the three stands of pine (Pinus sylvestris L., but WAVE overestimated the actual measured transpiration for a stand of poplar (Populus sp.. A useful approach to compare the WU components of forest versus cropland is scenario analysis based on the validated WAVE model. The statistical Profile Analysis method was implemented to explore and analyse the simulated WU time series. With an average annual rainfall of 819 mm, the results reveal that forests in Flanders consume more water than agricultural crops. A 30 years average of 491 mm for 10 forests stands versus 398 mm for 10 cropped agricultural fields was derived. The WU components, on yearly basis, also differ between the two land use types (transpiration: 315 mm for forest and 261 mm for agricultural land use; soil evaporation: 47 mm and 131 mm, for forest and cropland, respectively. Forest canopy interception evaporation was estimated at 126 mm, while it was negligible for cropland.
Oblique Water Wave Scattering by Bottom Undulation in a Two-layer Fluid Flowing Through a Channel
Institute of Scientific and Technical Information of China (English)
Smrutiranjan Mohapatra; Swaroop Nandan Bora
2012-01-01
The problem of oblique wave (internal wave) propagation over a small deformation in a channel flow consisting of two layers was considered.The upper fluid was assumed to be bounded above by a rigid lid,which is an approximation for the free surface,and the lower one was bounded below by an impermeable bottom surface having a small deformation; the channel was unbounded in the horizontal directions.Assuming irrotational motion,the perturbation technique was employed to calculate the first-order corrections of the velocity potential in the two fluids by using Green's integral theorem suitably with the introduction of appropriate Green's functions.Those functions help in calculating the reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom deformation.Three-dimensional linear water wave theory was utilized for formulating the relevant boundary value problem.Two special examples of bottom deformation were considered to validate the results.Consideration of a patch of sinusoidal ripples (having the same wave number) shows that the reflection coefficient is an oscillatory function of the ratio of twice the x-component of the wave number to the ripple wave number.When this ratio approaches one,the theory predicts a resonant interaction between the bed and the interface,and the reflection coefficient becomes a multiple of the number of tipples.High reflection of incident wave energy occurs if this number is large.Similar results were observed for a patch of sinusoidal tipples having different wave numbers.It was also observed that for small angles of incidence,the reflected energy is greater compared to other angles of incidence up to π / 4.These theoretical observations are supported by graphical results.
Carniel, Sandro; Benetazzo, Alvise; Bonaldo, Davide; Falcieri, Francesco M.; Miglietta, Mario Marcello; Ricchi, Antonio; Sclavo, Mauro
2016-05-01
Cold Air Outbreaks (CAOs) over shallow seas may lead to dense water formation episodes, enhancing water, heat, nutrient and sediment exchanges across the continental margin, with associated seabed reshaping. During winter 2012, a CAO episode characterised by exceptional intensity stroke the northern Adriatic Sea, one of the most effective cool engines driving the Mediterranean circulation, providing a paramount opportunity for an integrated investigation of dense shelf water dynamics. In the present study, we describe this event using a fully coupled modeling approach exploring the effects of mutual interactions among atmosphere, ocean currents and sea surface waves, usually not completely accounted for, in the resulting dense water formation. Whilst atmospheric fields appear to be marginally affected by coupled dynamics in the present case, implications for sea surface elevation and circulation are far from negligible. Measurements collected in the northern Adriatic Sea showed that a physically consistent description of energy exchanges between ocean and atmosphere provides an improved estimate of heat fluxes and of air and sea temperatures. In addition, the explicit inclusion of wave action within the modeling system further enhances the modulation of air-sea exchanges and the propagation of its effect along the water column, resulting in a different intensity of northern Adriatic gyres and in different water fluxes flowing through the formation basin. Through these main controls on the water volume involved in the densification process and on the intensity of momentum input and cooling, a coupled modeling strategy accounting for atmosphere-waves-currents interactions can turn out to be crucial for improving the quantification of thermohaline properties and energy content, newly formed dense water mass, and provide a better description of its migration pathways and rates of off-shelf descent.
Directory of Open Access Journals (Sweden)
Serge Suanez
2015-07-01
Full Text Available Monitoring of dune erosion and accretion on the high-energy macrotidal Vougot beach in North Brittany (France over the past decade (2004–2014 has revealed significant morphological changes. Dune toe erosion/accretion records have been compared with extreme water level measurements, defined as the sum of (i astronomic tide; (ii storm surge; and (iii vertical wave runup. Runup parameterization was conducted using swash limits, beach profiles, and hydrodynamic (Hm0, Tm0,–1, and high tide water level—HTWL data sets obtained from high frequency field surveys. The aim was to quantify in-situ environmental conditions and dimensional swash parameters for the best calibration of Battjes [1] runup formula. In addition, an empirical equation based on observed tidal water level and offshore wave height was produced to estimate extreme water levels over the whole period of dune morphological change monitoring. A good correlation between this empirical equation (1.01Hmoξo and field runup measurements (Rmax was obtained (R2 85%. The goodness of fit given by the RMSE was about 0.29 m. A good relationship was noticed between dune erosion and high water levels when the water levels exceeded the dune foot elevation. In contrast, when extreme water levels were below the height of the toe of the dune sediment budget increased, inducing foredune recovery. These erosion and accretion phases may be related to the North Atlantic Oscillation Index.
Continuity and asymptotic behaviors for a shallow water wave model with moderate amplitude
Zhou, Shouming; Qiao, Zhijun; Mu, Chunlai; Wei, Long
2017-07-01
In this paper, we study continuity and persistence for a nonlinear evolution equation describing the free surface of shallow water wave with a moderate amplitude, which was proposed by Constantin and Lannes [7]. By the approach for approximate solutions and well-posedness estimates, we obtain two sequences of solution for Constantin-Lannes equation, which are bounded in the Sobolev space Hs (R) with s > 3 / 2, and the distance between the two sequences is lower-bounded by a positive constant for any time t, but converges to zero at the initial time. This implies that the solution map is not uniformly continuous. Furthermore, the solution map for Constantin-Lannes equation is shown Hölder-continuous in Hr-topology for all 0 ≤ r < s with exponent α depending on s and r. In addition, we also investigate the asymptotic behaviors of the strong solutions to Constantin-Lannes equation at infinity within its lifespan provided the initial data in weighted Lϕp : =Lp (R ,ϕp dx) spaces.
Real-time Web GIS to monitor marine water quality using wave glider
Maneesa Amiruddin, Siti
2016-06-01
In the past decade, Malaysia has experienced unprecedented economic development and associated socioeconomic changes. As environmentalists anticipate these changes could have negative impacts on the marine and coastal environment, a comprehensive, continuous and long term marine water quality monitoring programme needs to be strengthened to reflect the government's aggressive mind-set of enhancing its authority in protection, preservation, management and enrichment of vast resources of the ocean. Wave Glider, an autonomous, unmanned marine vehicle provides continuous ocean monitoring at all times and is durable in any weather condition. Geographic Information System (GIS) technology is ideally suited as a tool for the presentation of data derived from continuous monitoring of locations, and used to support and deliver information to environmental managers and the public. Combined with GeoEvent Processor, an extension from ArcGIS for Server, it extends the Web GIS capabilities in providing real-time data from the monitoring activities. Therefore, there is a growing need of Web GIS for easy and fast dissemination, sharing, displaying and processing of spatial information which in turn helps in decision making for various natural resources based applications.
Directory of Open Access Journals (Sweden)
Yafeng Xiao
2012-01-01
Full Text Available With the aid of symbolic computation, a new extended Jacobi elliptic function expansion method is presented by means of a new ansatz, in which periodic solutions of nonlinear evolution equations, which can be expressed as a finite Laurent series of some 12 Jacobi elliptic functions, are very effective to uniformly construct more new exact periodic solutions in terms of Jacobi elliptic function solutions of nonlinear partial differential equations. As an application of the method, we choose the generalized shallow water wave (GSWW equation to illustrate the method. As a result, we can successfully obtain more new solutions. Of course, more shock wave solutions or solitary wave solutions can be gotten at their limit condition.
Distribution of Wave Loads for Design of Crown Walls in Deep and Shallow Water
DEFF Research Database (Denmark)
Nørgaard, Jørgen Quvang Harck; Andersen, Thomas Lykke
2014-01-01
This paper puts forward a new method to determine horizontal wave loads on rubble mound breakwater crown walls with specific exceedance probabilities based on the formulae by Nørgaard et al. (2013) as well as presents a new modified version of the wave run-up formula by Van der Meer & Stam (1992......). Predictions from the method are compared to measured horizontal wave loads from scaled model tests, and the new method provides results which are in agreement with measured values as long as the wave loads on the crown wall are relatively impulsive. Another aim of the paper has been to compare...... the displacements of a crown wall exposed to wave loads with different exceedance probabilities in an overload situation (in this case the loads exceeded by 0.1 % and 1/250 of the incident waves). The comparison is made using the assumption that the Eigenfrequency of the crown wall and breakwater is significantly...
Storm-wave trends in Mexican waters of the Gulf of Mexico and Caribbean Sea
Ojeda, Elena; Appendini, Christian M.; Tonatiuh Mendoza, E.
2017-08-01
Thirty-year time series of hindcast wave data were analysed for 10 coastal locations along the eastern Mexican coast to obtain information about storm events occurring in the region, with the goal of examining the possible presence of interannual trends in the number of storm-wave events and their main features (wave height, duration and energy content). The storms were defined according to their significant wave height and duration, and the events were classified as related to either tropical cyclones or Norte events. The occurrence and characteristics of both types of events were analysed independently. There is no statistically significant change in the number of storm-wave events related to Nortes or their characteristics during the study period. However, there is a subtle increase in the number of events related to tropical cyclones in the western Caribbean region and a more evident increase in wave height and energy content of these events.
Soliton solutions to a few fractional nonlinear evolution equations in shallow water wave dynamics
Mirzazadeh, Mohammad; Ekici, Mehmet; Sonmezoglu, Abdullah; Ortakaya, Sami; Eslami, Mostafa; Biswas, Anjan
2016-05-01
This paper studies a few nonlinear evolution equations that appear with fractional temporal evolution and fractional spatial derivatives. These are Benjamin-Bona-Mahoney equation, dispersive long wave equation and Nizhnik-Novikov-Veselov equation. The extended Jacobi's elliptic function expansion method is implemented to obtain soliton and other periodic singular solutions to these equations. In the limiting case, when the modulus of ellipticity approaches zero or unity, these doubly periodic functions approach solitary waves or shock waves or periodic singular solutions emerge.
A Study of Two-Dimensional Unsteady Breaking Waves in Finite-Depth Water
2010-01-01
1880). [8] J. H. Duncan, “An experimental investigation of breaking waves produced by a towed hydrofoil ,” Proc. R. Soc. London, Ser. A 377, 331(1981...measured the drag per unit length due to quasi-steady breaking waves generated with a submerged hydrofoil . His measurements illustrated that the... hydrofoil . Proc. R. Soc. London Ser. A 377, 331-348. DUNCAN, J. H. 1983 The breaking and non-breaking wave resistance of a two- dimensional hydrofoil . J
Effects of Internal Waves on Sound Propagation in the Shallow Waters of the Continental Shelves
2016-09-01
B.E.E., Nanyang Technological University, 2002 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN...Figure 1. The red dots indicate the locations where internal waves are recorded in “An Atlas of Oceanic Internal Solitary Waves.” The lack of...Temperature Plot—Week 8, First 3 Days. B. INTERNAL TIDES From these plots, it was observed that there was great variability in internal wave activity
Jazayeri Shoushtari, Seyed Mohammad Hossein; Cartwright, Nick
2016-11-01
This paper examines the influence of porous media deformation on water-table wave dispersion in an unconfined aquifer using a numerical model which couples Richards' equation to the poro-elastic model. The study was motivated by the findings of Shoushtari et al. (J Hydrol 533:412-440, 2016) who were unable to reproduce the observed wave dispersion in their sand flume data with either numerical Richards' equation models (assuming rigid porous media) or existing analytic solutions. The water-table wave dispersion is quantified via the complex wave number extracted from the predicted amplitude and phase profiles. A sensitivity analysis was performed to establish the influence of the main parameters in the poro-elastic model, namely Young's modulus (E) and Poisson's ratio (ν). For a short oscillation period (T = 16.4 s), the phase lag increase rate (k i) is sensitive to the chosen values of E and ν, demonstrating an inverse relationship with both parameters. Changes in the amplitude decay rate (k r), however, were negligible. For a longer oscillation period (T = 908.6 s), variations in the values of E and ν resulted in only small changes in both k r and k i. In both the short and long period cases, the poro-elastic model is unable to reproduce the observed wave dispersion in the existing laboratory data. Hence porous media deformation cannot explain the additional energy dissipation in the laboratory data. Shoushtari SMH, Cartwright N, Perrochet P, Nielsen P (2016) The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: sand flume experiments and modelling. J Hydrol 533:412-440.
Jazayeri Shoushtari, Seyed Mohammad Hossein; Cartwright, Nick
2017-03-01
This paper examines the influence of porous media deformation on water-table wave dispersion in an unconfined aquifer using a numerical model which couples Richards' equation to the poro-elastic model. The study was motivated by the findings of Shoushtari et al. (J Hydrol 533:412-440, 2016) who were unable to reproduce the observed wave dispersion in their sand flume data with either numerical Richards' equation models (assuming rigid porous media) or existing analytic solutions. The water-table wave dispersion is quantified via the complex wave number extracted from the predicted amplitude and phase profiles. A sensitivity analysis was performed to establish the influence of the main parameters in the poro-elastic model, namely Young's modulus ( E) and Poisson's ratio ( ν). For a short oscillation period ( T = 16.4 s), the phase lag increase rate ( k i) is sensitive to the chosen values of E and ν, demonstrating an inverse relationship with both parameters. Changes in the amplitude decay rate ( k r), however, were negligible. For a longer oscillation period ( T = 908.6 s), variations in the values of E and ν resulted in only small changes in both k r and k i. In both the short and long period cases, the poro-elastic model is unable to reproduce the observed wave dispersion in the existing laboratory data. Hence porous media deformation cannot explain the additional energy dissipation in the laboratory data. Shoushtari SMH, Cartwright N, Perrochet P, Nielsen P (2016) The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: sand flume experiments and modelling. J Hydrol 533:412-440.
Stability of Low-Crested Breakwaters in Shallow Water Short Crested Waves
DEFF Research Database (Denmark)
Kramer, Morten Mejlhede; Burcharth, Hans Falk
2003-01-01
The paper presents results of 3D laboratory experiments on low-crested breakwaters. Two typical structural layouts were tested at model scale in a wave basin at Aalborg University, Denmark, to identify and quantify the influence of various hydrodynamic conditions (obliquity of short crested waves......, wave hight and wave steepness) and structural geometries (crest width and freeboard) on the stability of low-crested breakwaters. Results are given in terms of recommendations for design guidelines for structure stability. Damage parameters for the trunk and the roundhead are proposed based on analysis...
Directionality and spread of shallow water waves along the eastern Arabian Sea
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Anoop, T.R.
height, (b) peak wave period, (c) mean wave direction, (d) wave age, (e) skewness of the surface elevation, and (f) mean spreading angle. The hourly average value of directional width during differ- ent months indicates that the variation is large (≈ 16... between θ and ϕ (Fig. 6c and d). The difference between θ and ϕ at spectral peak is large for Hm0 less than 1 m (Fig. 6e and f) and is neg- ligible (< 5◦) for Hm0 more than 1 m. The directional width is large (∼ 60◦) for the waves from θp < 240◦ with Hm0...
Green roof and storm water management policies: monitoring experiments on the ENPC Blue Green Wave
Versini, Pierre-Antoine; Gires, Auguste; Fitton, George; Tchiguirinskaia, Ioulia; Schertzer, Daniel
2015-04-01
Currently widespread in new urban projects, green roofs have shown a positive impact on urban runoff at the building/parcel scale. Nevertheless, there is no specific policy promoting their implementation neither in Europe nor in France. Moreover they are not taken into account (and usually considered as an impervious area) in the sizing of a retention basin for instance. An interesting example is located in the heart of the Paris-East Cluster for Science and Technology (Champs-sur-Marne, France). Since 2013 a large (1 ha) wavy-form vegetated roof (called bleu green wave) is implemented. Green roof area and impervious areas are connected to a large retention basin, which has been oversized. The blue green wave represents a pioneering site where an initially amenity (decorative) design project has been transformed into a research oriented one. Several measurement campaigns have been conducted to investigate and better understand the hydrological behaviour of such a structure. Rainfall, humidity, wind velocity, water content and temperature have been particularly studied. The data collected are used for several purposes: (i) characterize the spatio-temporal variability of the green roof response, (ii) calibrate and validate a specific model simulating its hydrological behavior. Based on monitoring and modeling results, green roof performances will be quantified. It will be possible to estimate how they can reduce stormwater runoff and how these performances can vary in space and in time depending on green roof configuration, rainfall event characteristics and antecedent conditions. These quantified impacts will be related to regulation rules established by stormwater managers in order to connect the parcel to the sewer network. In the particular case of the building of a retention basin, the integration of green roof in the sizing of the basin will be studied. This work is funded by the European Blue Green Dream project (http://bgd.org.uk/, funded by Climate
Rajapakse, G.; Jayasinghe, S. G.; Fleming, A.; Shahnia, F.
2017-07-01
Australia’s extended coastline asserts abundance of wave and tidal power. The predictability of these energy sources and their proximity to cities and towns make them more desirable. Several tidal current turbine and ocean wave energy conversion projects have already been planned in the coastline of southern Australia. Some of these projects use air turbine technology with air driven turbines to harvest the energy from an oscillating water column. This study focuses on the power take-off control of a single stage unidirectional oscillating water column air turbine generator system, and proposes a model predictive control-based speed controller for the generator-turbine assembly. The proposed method is verified with simulation results that show the efficacy of the controller in extracting power from the turbine while maintaining the speed at the desired level.
Vivanco, F
2002-01-01
We present a simple experiment to study the interaction of surface waves with a vertical vortex in the deep water regime. Similarly to what occurs in the Quantum Mechanics Aharonov-Bohm problem for electron interacting with a magnetic potential, the effect of the vortex circulation is to introduce dislocations in the wavefront. These defects are explained taken into account the effects of advection on the propagating wavefront, due to the fluid motion. (Author)
A variational model for fully non-linear water waves of Boussinesq type
Klopman, Gert; Dingemans, Maarten W.; Groesen, van Brenny; Grue, J.
2005-01-01
Using a variational principle and a parabolic approximation to the vertical structure of the velocity potential, the equations of motion for surface gravity waves over mildly sloping bathymetry are derived. No approximations are made concerning the non-linearity of the waves. The resulting model equ
The Application of a Numerical Model to Coastal Surface Water Waves
Institute of Scientific and Technical Information of China (English)
ZOU Huazhi; LI Huajun; LIU Xiaodong; LIU Aixia
2005-01-01
Based on the Navier-Stokes Equations (NSE), numerical simulation with fine grids is conducted to simulate the coastal surface wave changes, including wave generation, propagation, transformation and interactions between waves and structures. This numerical model has been tested for the generation of the desired incident waves, including both regular and random waves. Some numerical results of this model are compared with available experimental data. In order to apply this model to actual cases, boundary conditions are considered in detail for different shoreline types (beach or breakwater, slope or vertical wall, etc. ). Finally, the utility of the model to a real coastal area is shown by applying it to a fishing port located in Shidao, Rongcheng, Shandong Province, P.R. China.
Atomization off thin water films generated by high-frequency substrate wave vibrations.
Collins, David J; Manor, Ofer; Winkler, Andreas; Schmidt, Hagen; Friend, James R; Yeo, Leslie Y
2012-11-01
Generating aerosol droplets via the atomization of thin aqueous films with high frequency surface acoustic waves (SAWs) offers several advantages over existing nebulization methods, particularly for pulmonary drug delivery, offering droplet sizes in the 1-5-μm range ideal for effective pulmonary therapy. Nevertheless, the physics underlying SAW atomization is not well understood, especially in the context of thin liquid film formation and spreading and how this affects the aerosol production. Here, we demonstrate that the film geometry, governed primarily by the applied power and frequency of the SAW, indeed plays a crucial role in the atomization process and, in particular, the size of the atomized droplets. In contrast to the continuous spreading of low surface energy liquids atop similar platforms, high surface energy liquids such as water, in the present case, are found to undergo transient spreading due to the SAW to form a quasisteady film whose height is determined by self-selection of the energy minimum state associated with the acoustic resonance in the film and whose length arises from a competition between acoustic streaming and capillary effects. This is elucidated from a fundamental model for the thin film spreading behavior under SAW excitation, from which we show good agreement between the experimentally measured and theoretically predicted droplet dimension, both of which consistently indicate a linear relationship between the droplet diameter and the mechanical power coupled into the liquid by the SAW (the latter captured by an acoustic Weber number to the two thirds power, and the reciprocal of the SAW frequency).
Integral and integrable algorithms for a nonlinear shallow-water wave equation
Camassa, Roberto; Huang, Jingfang; Lee, Long
2006-08-01
An asymptotic higher-order model of wave dynamics in shallow water is examined in a combined analytical and numerical study, with the aim of establishing robust and efficient numerical solution methods. Based on the Hamiltonian structure of the nonlinear equation, an algorithm corresponding to a completely integrable particle lattice is implemented first. Each "particle" in the particle method travels along a characteristic curve. The resulting system of nonlinear ordinary differential equations can have solutions that blow-up in finite time. We isolate the conditions for global existence and prove l1-norm convergence of the method in the limit of zero spatial step size and infinite particles. The numerical results show that this method captures the essence of the solution without using an overly large number of particles. A fast summation algorithm is introduced to evaluate the integrals of the particle method so that the computational cost is reduced from O( N2) to O( N), where N is the number of particles. The method possesses some analogies with point vortex methods for 2D Euler equations. In particular, near singular solutions exist and singularities are prevented from occurring in finite time by mechanisms akin to those in the evolution of vortex patches. The second method is based on integro-differential formulations of the equation. Two different algorithms are proposed, based on different ways of extracting the time derivative of the dependent variable by an appropriately defined inverse operator. The integro-differential formulations reduce the order of spatial derivatives, thereby relaxing the stability constraint and allowing large time steps in an explicit numerical scheme. In addition to the Cauchy problem on the infinite line, we include results on the study of the nonlinear equation posed in the quarter (space-time) plane. We discuss the minimum number of boundary conditions required for solution uniqueness and illustrate this with numerical
Le Roux, Jacobus P.; Demirbilek, Zeki; Brodalka, Marysia; Flemming, Burghard W.
2010-10-01
The generation and growth of waves in deep water is controlled by winds blowing over the sea surface. In fully developed sea states, where winds and waves are in equilibrium, wave parameters may be calculated directly from the wind velocity. We provide an Excel spreadsheet to compute the wave period, length, height and celerity, as well as horizontal and vertical particle velocities for any water depth, bottom slope, and distance below the reference water level. The wave profile and propagation can also be visualized for any water depth, modeling the sea surface change from sinusoidal to trochoidal and finally cnoidal profiles into shallow water. Bedload entrainment is estimated under both the wave crest and the trough, using the horizontal water particle velocity at the top of the boundary layer. The calculations are programmed in an Excel file called WAVECALC, which is available online to authorized users. Although many of the recently published formulas are based on theoretical arguments, the values agree well with several existing theories and limited field and laboratory observations. WAVECALC is a user-friendly program intended for sedimentologists, coastal engineers and oceanographers, as well as marine ecologists and biologists. It provides a rapid means to calculate many wave characteristics required in coastal and shallow marine studies, and can also serve as an educational tool.
Comparison of magnetosonic wave and water group ion energy densities at Comet Giacobini-Zinner
Staines, K.; Balogh, A.; Cowley, S. W. H.; Forster, P. M. De F.; Hynds, R. J.; Yates, T. S.; Sanderson, T. R.; Wenzel, K.-P.; Tsurutani, B. T.
1991-01-01
Measurements of the Comet Giacobini-Zinner (GZ) are presented to determine to what extent wave-particle scattering redistributed the initial pick-up energy of the ion population. Also examined is the difference between the ion thermal energy and the energy in the magnetic fields of the waves. In spite of uncertainty of about a factor of 2 noted in the pick-up and mass-loaded regions, it is shown that less than approximately 50 percent of the pick-up energy is converted into wave magnetic energy in the inbound pick-up region.
A THIRD-ORDER BOUSSINESQ MODEL APPLIED TO NONLINEAR EVOLUTION OF SHALLOW-WATER WAVES
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The conventional Boussinesq model is extended to the third order in dispersion and nonlinearity. The new equations are shown to possess better linear dispersion characteristics. For the evolution of periodic waves over a constant depth, the computed wave envelops are spatially aperiodic and skew. The model is then applied to the study of wave focusing by a topographical lens and the results are compared with Whalin's (1971) experimental data as well as some previous results from the conventional Boussinesq model. Encouragingly, improved agreement with Whalin's experimental data is found.
Numerical simulation for treatment of dispersive shallow water waves with Rosenau-KdV equation
Ak, Turgut; Battal Gazi Karakoc, S.; Triki, Houria
2016-10-01
In this paper, numerical solutions for the Rosenau-Korteweg-de Vries equation are studied by using the subdomain method based on the sextic B-spline basis functions. Numerical results for five test problems including the motion of single solitary wave, interaction of two and three well-separated solitary waves of different amplitudes, evolution of solitons with Gaussian and undular bore initial conditions are obtained. Stability and a priori error estimate of the scheme are discussed. A comparison of the values of the obtained invariants and error norms for single solitary wave with earlier results is also made. The results show that the present method is efficient and reliable.
Bonne, Jean-Louis; Steen-Larsen, Hans Christian; Masson-Delmotte, Valérie; Sodemann, Harald; Lacour, Jean-Lionel; Risi, Camille; Werner, Martin; Clerbaux, Cathy; Fettweis, Xavier
2014-05-01
In July 2012, an extreme warm event occurred in Greenland, leading to surface melt over almost all the ice sheet. This event was recorded in the isotopic composition of water vapour measured by the IASI satellite along the transport pathway and at two sites where continuous in situ surface vapour isotopic measurements were conducted, situated at a coastal station of South Greenland (Ivittuut) and further North on top of the ice sheet (NEEM, NW Greenland). These observations allowed us to monitor the isotopic composition of the air mass at different stages of its advection towards Greenland, which can inform on processes along this trajectory, such as cloud properties and moisture sources. In addition, two simulations of this event, using the atmospheric general circulation models LMDZiso and ECHAM5wiso equipped with water stable isotopes and nudged towards large scale wind fields, are investigated. Furthermore, a regional high-resolution model was used to study the moisture transport to Greenland during this event using tagged water tracers of the North Atlantic ocean and coastal land evaporation. Using moisture source diagnostic based on the Lagrangian particle dispersion model Flexpart, we show that this 2012 heat wave event corresponds to moisture sources located over the subtropical Atlantic Ocean, where intense evaporation was caused by dry air masses associated with the US intense summer drought. This moisture was then advected northward along a narrow band, due to a very stationary surface cyclone southwest of Greenland, reached southern Greenland and Ivittuut coastal station on July 9th, travelled along the west coast of Greenland, continued eastwards above the ice sheet and arrived above the NEEM deep drilling camp on July 11th. Surface isotopic observations during the event show larger variations at NEEM than in Ivittuut, strongly reducing the isotopic and deuterium excess latitudinal gradient usually observed between South and North Greenland. This
Directional characteristics of shallow water waves along southwestern Bay of Bengal
Digital Repository Service at National Institute of Oceanography (India)
Johnson, G.; SanilKumar, V.; Anoop, T.R.; Joseph, J.
the coast during southwest monsoon season (June–September) and intrusion of moderate easterly winds propagating from Gulf of Thailand over the narrow land mass of Thailand and Myanmar. The reflected wave energy is maximum (14%) during the southwest monsoon...
2015-08-01
southern boundary around 36 deg N latitude. The maxi - mum Hmo estimate locations are based (as is the wind speed) on an abso- lute value. If there are...validation events.) After remaining a weak tropical cyclone for several days, Gloria intensified into a hurricane on 22 September 1985. Gloria...significantly impacting the maxi - mum wave height solution for a preliminary Sandy simulation (the abso- lute difference in maximum wave height within
Ahmed, Abdelsalam
2016-12-08
This paper presents a fully enclosed duck-shaped triboelectric nanogenerator (TENG) for effectively scavenging energy from random and low-frequency water waves. The design of the TENG incorporates the freestanding rolling mode and the pitch motion of a duck-shaped structure generated by incident waves. By investigating the material and structural features, a unit of the TENG device is successfully designed. Furthermore, a hybrid system is constructed using three units of the TENG device. The hybrid system achieves an instantaneous peak current of 65.5 µA with an instantaneous output power density of up to 1.366 W m−2. Following the design, a fluid–solid interaction analysis is carried out on one duck-shaped TENG to understand the dynamic behavior, mechanical efficiency, and stability of the device under various water wave conditions. In addition, the hybrid system is experimentally tested to enable a commercial wireless temperature sensor node. In summary, the unique duck-shaped TENG shows a simple, cost-effective, environmentally friendly, light-weight, and highly stable system. The newly designed TENG is promising for building a network of generators to harvest existing blue energy in oceans, lakes, and rivers.
Wave excited motion of a body floating on water confined between two semi-infinite ice sheets
Ren, K.; Wu, G. X.; Thomas, G. A.
2016-12-01
The wave excited motion of a body floating on water confined between two semi-infinite ice sheets is investigated. The ice sheet is treated as an elastic thin plate and water is treated as an ideal and incompressible fluid. The linearized velocity potential theory is adopted in the frequency domain and problems are solved by the method of matched eigenfunctions expansion. The fluid domain is divided into sub-regions and in each sub-region the velocity potential is expanded into a series of eigenfunctions satisfying the governing equation and the boundary conditions on horizontal planes including the free surface and ice sheets. Matching is conducted at the interfaces of two neighbouring regions to ensure the continuity of the pressure and velocity, and the unknown coefficients in the expressions are obtained as a result. The behaviour of the added mass and damping coefficients of the floating body with the effect of the ice sheets and the excitation force are analysed. They are found to vary oscillatorily with the wave number, which is different from that for a floating body in the open sea. The motion of the body confined between ice sheets is investigated, in particular its resonant behaviour with extremely large motion found to be possible under certain conditions. Standing waves within the polynya are also observed.
Mohapatra, S.; Sarangi, M. R.
2017-03-01
The solution of water wave scattering problem involving small deformation on a porous bed in a channel, where the upper surface is bounded above by an infinitely extent rigid horizontal surface, is studied here within the framework of linearized water wave theory. In such a situation, there exists only one mode of waves propagating on the porous surface. A simplified perturbation analysis, involving a small parameter ɛ ( ≪ 1), which measures the smallness of the deformation, is employed to reduce the governing Boundary Value Problem (BVP) to a simpler BVP for the first-order correction of the potential function. The first-order potential function and, hence, the first-order reflection and transmission coefficients are obtained by the method based on Fourier transform technique as well as Green's integral theorem with the introduction of appropriate Green's function. Two special examples of bottom deformation: the exponentially damped deformation and the sinusoidal ripple bed, are considered to validate the results. For the particular example of a patch of sinusoidal ripples, the resonant interaction between the bed and the upper surface of the fluid is attained in the neighborhood of a singularity, when the ripples wavenumbers of the bottom deformation become approximately twice the components of the incident field wavenumber along the positive x-direction. Also, the main advantage of the present study is that the results for the values of reflection and transmission coefficients are found to satisfy the energy-balance relation almost accurately.
Sato, Masanori; Matsuura, Kazuo; Fujii, Toshitaka
2001-02-01
We show the experimental data of selective ethanol separation from ethanol-water solution, using ultrasonic atomization. Pure ethanol could be obtained directly from a solution with several mol% ethanol-water solution at 10 °C. This result can be explained in terms of parametric decay instability of capillary wave, in which high localization and accumulation of acoustic energy occur, leading to ultrasonic atomization. That is, parametric decay instability condenses the energy of longitudinal waves in a highly localized surface area of the capillary wave, and causes ultrasonic atomization.
Addressing the problem of uniform converging spherical shock wave in water
Nitishinskiy, M.; Efimov, S.; Yanuka, D.; Gurovich, V. Tz.; Krasik, Ya. E.
2016-10-01
Time-resolved parameters of plasma compressed by a shock wave generated by the underwater electrical explosion of a spherical wire array are presented. The plasma was preliminarily formed inside a capillary placed at the equatorial plane along the axis of the array. Temporal evolution analysis of Hα and C II spectral lines showed that the plasma density increases from its initial value of ˜3 × 1017 cm-3 up to ˜5.5 × 1017 cm-3 within 300 ± 25 ns. These results were found to be in agreement with those of the model that considers the adiabatic compression of the plasma by the converging capillary walls caused by interaction with the incident shock wave with a pressure of ˜3 × 109 Pa at a radius of 1.5 mm. The latter results coincide well with those of the 1D hydrodynamic modeling, which assumes uniformity of the converging shock wave.
The effect of foam on waves and the aerodynamic roughness of the water surface at high winds
Troitskaya, Yuliya; Vdovin, Maxim; Sergeev, Daniil; Kandaurov, Alexander
2017-04-01
Air-sea coupling at extreme winds is of special interest now in connection with the problem of explanation of the sea surface drag saturation at the wind speed exceeding 30 m/s. The idea on saturation (and even reduction) of the coefficient of aerodynamic resistance of the sea surface at hurricane wind speed first suggested in [1] on the basis of theoretical analysis of sensitivity of maximum wind speed in a hurricane to the ratio of the enthalpy and momentum exchange coefficients was then confirmed by a number of field (e.g.[2]) and laboratory [3] experiments, which showed that the sea surface drag coefficient was significantly reduced in comparison with the parameterization obtained at moderate to strong wind conditions. The theoretical explanations of the effect of the sea surface drag reduction exploit either peculiarities of the air flow over breaking waves (e.g.[4,5]) or the effect of sea drops and spray on the wind-wave momentum exchange (e.g. [6,7]). Recently an alternative hypothesis was suggested in [8], where the surface drag reduction in hurricanes was explained by the influence of foam covering sea surface on its aerodynamic roughness. This paper describes a series of laboratory experiments in Thermostratified Wind-Wave Tank (TSWiWaT) of IAP directed to investigation of the foam impact on the short-wave part of the surface waves and the momentum exchange in the atmospheric boundary layer at high winds in the range of equivalent 10-m wind speed from 12 to 38 m/s. A special foam generator was designed for these experiments. The air flow parameters were retrieved from measurements of the velocity profiles. The frequency-wavenumber spectra of surface waves were retrieved from the measurements of water surface elevation by the array 3-channel wave gauge. Foam coverage of water surface was controlled by video filming of the water surface. The results of measurements were compared with predictions of the quasi-linear model of atmospheric boundary layer over
Field study and numerical modeling of wind and surface waves at the middle-sized water body
Baydakov, Georgy; Kuznetsova, Alexandra; Sergeev, Daniil; Papko, Vladislav; Kandaurov, Alexander; Vdovin, Maxim; Troitskaya, Yuliya
2015-04-01
This paper presents the results of field experiments on studying the wind and waves over inland waters, which were carried out at the Gorky Reservoir in 2011-2014. The sensors were positioned at the oceanographic Froude buoy including five two-component ultrasonic sensors WindSonic by Gill Instruments at different levels (0.1, 0.85, 1.3, 2.27, 5.26 meters above the mean water surface level), one water and three air temperature sensors, and three-channel wire wave gauge. From the measured profiles of wind speed, we calculated basic parameters of the atmospheric boundary layer: the friction velocity u*, the wind speed at the standard height of 10 m U10 and the drag coefficient CD. Parameters were obtained in the range of wind speeds of 1-10 m/s. For wind speeds stronger than 3 m/s CD values were lower than those obtained before (see eg. [1,2]) and those predicted by the bulk parameterization. In the range of wind speeds of 3-5 m/s CD values are even lower than the corresponding smooth flow. However, for weak winds (less than 2.5 m/s) CD values considerably higher than expected ones. The main peculiarity of our measurements is very low location of the lowest sensor: 0.1 m against 0.89 m in [1] and 0.5 m in [2]. Moreover, the lowest sensor was not fixed on the mast, but was located on the float and followed the water surface. Analysis shows that the obtained parameters of profile are almost independent on the number of approximated wind speed levels if they include the lowest sensor. But excluding the lowest sensor gave larger values of CD similar to [1] and [2]. These results demonstrate importance of wind speed measuring close to the water surface. The new parameterization of surface drag coefficient was proposed on the basis of the obtained data. The new surface drag parameterization was used in WAVEWATCH III model applied for modeling waves at the reservoir. 1-D spectra of the field experiment were compared with those obtained in the numerical experiments with
A 3-D Numerical Model for the Calculation of Water Wave Transformation in Large Area
Institute of Scientific and Technical Information of China (English)
孙大鹏; 李玉成; 葛岚
2001-01-01
Based on the integral equation transformed from three dimensional Laplace equation and by the adoption of the division manner of sub-region boundary element method, the numerical computations of the velocity potential of each sub-region are given considering the continuity conditions of potential and normal derivatives at the interface of sub-regions. Therefore, computation of wave deformation in offshore flow field is realized. The present numerical model provides a good solution for the application of boundary element method to the calculation of wave deformation in large areas.
Toward a scalable flexible-order model for 3D nonlinear water waves
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Ducrozet, Guillaume; Bingham, Harry B.
for flexibility in the description of structures by the use of curvilinear boundary-fitted meshes. The mathematical equations for potential waves in the physical domain is transformed through $\\sigma$-mapping(s) to a time-invariant boundary-fitted domain which then becomes a basis for an efficient solution...
A comparative study of two fast nonlinear free-surface water wave models
DEFF Research Database (Denmark)
Ducrozet, Guillaume; Bingham, Harry B.; Engsig-Karup, Allan Peter
2012-01-01
This paper presents a comparison in terms of accuracy and efficiency between two fully nonlinear potential flow solvers for the solution of gravity wave propagation. One model is based on the high-order spectral (HOS) method, whereas the second model is the high-order finite difference model Ocea...
Spatial and temporal variation of surface waves in shallow waters along the eastern Arabian Sea.
Digital Repository Service at National Institute of Oceanography (India)
Anoop, T.R.; SanilKumar, V.; Shanas, P.R.
locations were used for the study. The study region covers 270 km along the west coast of India and lies between Karwar and Ratnagiri. The temporal variations of wave parameters were less than 10% at both locations for temporal intervals up to 12 h except...
Computational study of shock waves propagating through air-plastic-water interfaces
Del Razo, Mauricio J
2015-01-01
The following study is motivated by experimental studies in traumatic brain injury (TBI). Recent research has demonstrated that low intensity non-impact blast wave exposure frequently leads to mild traumatic brain injury (mTBI); however, the mechanisms connecting the blast waves and the mTBI remain unclear. Collaborators at the Seattle VA Hospital are doing experiments to understand how blast waves can produce mTBI. In order to gain insight that is hard to obtain by experimental means, we have developed conservative finite volume methods for interface-shock wave interaction to simulate these experiments. A 1D model of their experimental setup has been implemented using Euler equations for compressible fluids. These equations are coupled with a Tammann equation of state (EOS) that allows us to model compressible gas along with almost incompressible fluids or elastic solids. A hybrid HLLC-exact Eulerian-Lagrangian Riemann solver for Tammann EOS with a jump in the parameters has been developed. The model has sho...
Implementation (II) of the numerical shallow water wave hindcast model HISWA
Herbers, T.H.C.; Booij, N.; Holthuijsen, L.H.
1984-01-01
Development of a two-dimensional model to hindcast spectral wave parameters in an estuary with tidal flats on the basis of bottomtopography, current and wind data. Diffraction-like propagation has been implemented and tested. Tests indicate that this type of propagation cannot.be used for most appli
Efficient computation of steady, 3D water-wave patterns, application to hovercraft-type flows
M.R. Lewis; B. Koren (Barry)
2002-01-01
textabstractNumerical methods for the computation of stationary free surfaces is the subject of much current research in computational engineering. The present report is directed towards free surfaces in maritime engineering. Of interest here are the long steady waves generated by hovercraft and
Efficient computation of steady, 3D water-wave patterns, application to hovercraft-type flows
Lewis, M.R.; Koren, B.
2002-01-01
Numerical methods for the computation of stationary free surfaces is the subject of much current research in computational engineering. The present report is directed towards free surfaces in maritime engineering. Of interest here are the long steady waves generated by hovercraft and ships, the grav
Wave spectral response to sudden changes in wind direction in finite-depth waters
Aijaz, Saima; Rogers, W. Erick; Babanin, Alexander V.
2016-07-01
The response of a wind-sea spectrum to sudden changes in wind directions of 180° and 90° is investigated. Numerical simulations using the third-generation wave spectral model SWAN have been undertaken at micro timescales of 30 s and fine spatial resolution of less than 10 m. The results have been validated against the wave data collected during the field campaign at Lake George, Australia. The newly implemented 'ST6' physics in the SWAN model has been evaluated using a selection of bottom-friction terms and the two available functions for the nonlinear energy transfer: (1) exact solution of the nonlinear term (XNL), and (2) discrete interactions approximation (DIA) that parameterizes the nonlinear term. Good agreement of the modelled data is demonstrated directly with the field data and through the known experimental growth curves obtained from the extensive Lake George data set. The modelling results show that of the various combinations of models tested, the ST6/XNL model provides the most reliable computations of integral and spectral wave parameters. When the winds and waves are opposing (180° wind turn), the XNL is nearly twice as fast in the aligning the young wind-sea with the new wind direction than the DIA. In this case, the young wind-sea gradually decouples from the old waves and forms a new secondary peak. Unlike the 180° wind turn, there is no decoupling in the 90° wind turn and the entire spectrum rotates smoothly in the new direction. In both cases, the young wind-sea starts developing in the new wind direction within 10 min of the wind turn for the ST6 while the directional response of the default physics lags behind with a response time that is nearly double of ST6. The modelling results highlight the differences in source term balance among the different models in SWAN. During high wind speeds, the default settings provide a larger contribution from the bottom-friction dissipation than the whitecapping. In contrast, the whitecapping
Derakhti, Morteza; Kirby, James T.; Shi, Fengyan; Ma, Gangfeng
2016-11-01
Field-scale modeling of wave-breaking-induced turbulence and mean circulation is still challenging. Although Boussinesq-type models have been successfully used to study field-scale wave transformation and wave-breaking-driven circulation, they cannot provide turbulence or the vertical structure of the velocity field. In addition, the applicability of such models is limited to shallow water. In Part 1 (Derakhti et al., 2016b) of this study, we showed that the non-hydrostatic σ-coordinate RANS model NHWAVE, as described by Derakhti et al. (2016a), accurately predicts organized wave motions and total wave-breaking-induced energy dissipation from deep-water up to the swash zone using a few vertical σ-layers. In this paper, our goal is to examine what level of detail of wave-breaking-induced turbulence and mean circulation, both in depth- and steepness-limited breaking waves, can be reproduced by NHWAVE. Further, effects of modeled turbulent eddy viscosity on the predicted time-averaged velocity distribution is discussed. We establish that NHWAVE is capable of predicting the structure of the mean velocity and vorticity fields including large-scale breaking-induced coherent vortices in deep-water breaking events; where the absence of turbulence-induced eddy viscosity results in the overprediction of the velocity and vorticity field in the breaking region. We show that NHWAVE reduces the required CPU time up to two orders of magnitude in comparison with a comparable VOF-based simulation.
This paper presents a depth-averaged two-dimensional shallow water model for simulating long waves in vegetated water bodies under breaking and non-breaking conditions. The effects of rigid vegetation are modelled in the form of drag and inertia forces as sink terms in the momentum equations. The dr...
Institute of Scientific and Technical Information of China (English)
LIU Liang; LIU Fukun; SHAN Jiafang; KUANG Guangli
2007-01-01
In order to test the klystrons operated at a frequency of 3.7 GHz in a continuous wave (CW) mode,a type of water load to absorb its power up to 750 kW is presented.The distilled water sealed with an RF ceramic window is used as the absorbent.At a frequency range of 70 MHz,the VSWR (Voltage Standing Wave Ratio) is below 1.2,and the rise in temperature of water is about 30℃ at the highest power level.
Energy Technology Data Exchange (ETDEWEB)
Copping, Andrea E.; Geerlofs, Simon H.; Hanna, Luke A.
2013-09-30
Responsible deployment of marine and hydrokinetic (MHK) devices in estuaries, coastal areas, and major rivers requires that biological resources and ecosystems be protected through siting and permitting (consenting) processes. Scoping appropriate deployment locations, collecting pre-installation (baseline) and post-installation data all add to the cost of developing MHK projects, and hence to the cost of energy. Under the direction of the U.S. Department of Energy, Pacific Northwest National Laboratory scientists have developed logic models that describe studies and processes for environmental siting and permitting. Each study and environmental permitting process has been assigned a cost derived from existing and proposed tidal, wave, and riverine MHK projects, as well as expert opinion of marine environmental research professionals. Cost estimates have been developed at the pilot and commercial scale. The reference model described in this document is an oscillating water column device deployed in Northern California at approximately 50 meters water depth.
Energy Technology Data Exchange (ETDEWEB)
Copping, Andrea E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Geerlofs, Simon H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hanna, Luke A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2013-09-01
Responsible deployment of marine and hydrokinetic (MHK) devices in estuaries, coastal areas, and major rivers requires that biological resources and ecosystems be protected through siting and permitting (consenting) processes. Scoping appropriate deployment locations, collecting pre-installation (baseline) and post-installation data all add to the cost of developing MHK projects, and hence to the cost of energy. Under the direction of the U.S. Department of Energy, Pacific Northwest National Laboratory scientists have developed logic models that describe studies and processes for environmental siting and permitting. Each study and environmental permitting process has been assigned a cost derived from existing and proposed tidal, wave, and riverine MHK projects, as well as expert opinion of marine environmental research professionals. Cost estimates have been developed at the pilot and commercial scale. The reference model described in this document is an oscillating water column device deployed in Northern California at approximately 50 meters water depth.
Zhu, Guang; Su, Yuanjie; Bai, Peng; Chen, Jun; Jing, Qingshen; Yang, Weiqing; Wang, Zhong Lin
2014-06-24
Energy harvesting from ambient water motions is a desirable but underexplored solution to on-site energy demand for self-powered electronics. Here we report a liquid-solid electrification-enabled generator based on a fluorinated ethylene propylene thin film, below which an array of electrodes are fabricated. The surface of the thin film is charged first due to the water-solid contact electrification. Aligned nanowires created on the thin film make it hydrophobic and also increase the surface area. Then the asymmetric screening to the surface charges by the waving water during emerging and submerging processes causes the free electrons on the electrodes to flow through an external load, resulting in power generation. The generator produces sufficient output power for driving an array of small electronics during direct interaction with water bodies, including surface waves and falling drops. Polymer-nanowire-based surface modification increases the contact area at the liquid-solid interface, leading to enhanced surface charging density and thus electric output at an efficiency of 7.7%. Our planar-structured generator features an all-in-one design without separate and movable components for capturing and transmitting mechanical energy. It has extremely lightweight and small volume, making it a portable, flexible, and convenient power solution that can be applied on the ocean/river surface, at coastal/offshore areas, and even in rainy places. Considering the demonstrated scalability, it can also be possibly used in large-scale energy generation if layers of planar sheets are connected into a network.
Zampieri, M.; Ceglar, A.; Dentener, F.; Toreti, A.
2017-06-01
Heat waves and drought are often considered the most damaging climatic stressors for wheat. In this study, we characterize and attribute the effects of these climate extremes on wheat yield anomalies (at global and national scales) from 1980 to 2010. Using a combination of up-to-date heat wave and drought indexes (the latter capturing both excessively dry and wet conditions), we have developed a composite indicator that is able to capture the spatio-temporal characteristics of the underlying physical processes in the different agro-climatic regions of the world. At the global level, our diagnostic explains a significant portion (more than 40%) of the inter-annual production variability. By quantifying the contribution of national yield anomalies to global fluctuations, we have found that just two concurrent yield anomalies affecting the larger producers of the world could be responsible for more than half of the global annual fluctuations. The relative importance of heat stress and drought in determining the yield anomalies depends on the region. Moreover, in contrast to common perception, water excess affects wheat production more than drought in several countries. We have also performed the same analysis at the subnational level for France, which is the largest wheat producer of the European Union, and home to a range of climatic zones. Large subnational variability of inter-annual wheat yield is mostly captured by the heat and water stress indicators, consistently with the country-level result.
Raghukumar, Kaustubha; Colosi, John A
2014-07-01
Using transport theory and Monte Carlo numerical simulation, the statistical properties of mode propagation at a frequency of 1 kHz are studied in a shallow water environment with random sound-speed perturbations from linear internal waves. The environment is typical of summer conditions in the mid-Atlantic bight during the Shallow Water 2006 experiment. Observables of interest include the second and fourth moments of the mode amplitudes, which are relevant to full-field mean intensity and scintillation index. It is found that mode phase randomization has a strong adiabatic component while at the same time mode coupling rates are significant. As a consequence, a computationally efficient transport theory is presented, which models cross-mode correlation adiabatically, but accounts for mode coupling using the mode energy equations of Creamer [(1996). J. Acoust. Soc. Am. 99, 2825-2838]. The theory also has closed-form expressions for the internal wave scattering matrix and a correction for an edge effect. The hybrid transport theory is shown to accurately reproduce many statistical quantities from the Monte Carlo simulations.
Generation of two-dimensional water waves by moving bottom disturbances
Nersisyan, Hayk; Zuazua, Enrique
2012-01-01
In this study we investigate the potential and limitations of the wave generation by disturbances moving at the bottom. More precisely, we assume that the wavemaker is composed of an underwater object of a given shape which can be displaced according to a given trajectory. The practical question we address in this study is how to compute the wavemaker shape and its trajectory in order to generate a wave with prescribed characteristics? For the sake of simplicity we model the hydrodynamics by a generalized forced BBM equation. This practical problem is reformulated as a constrained nonlinear optimization problem. Some constraints are imposed in order to make practically feasible the computed solution. Finally, we show some numerical results to support our theoretical and algorithmic developments.
Ordering of two small parameters in the shallow water wave problem
Burde, Georgy I
2013-01-01
The classical problem of irrotational long waves on the surface of a shallow layer of an ideal fluid moving under the influence of gravity as well as surface tension is considered. A systematic procedure for deriving an equation for surface elevation for a prescribed relation between the orders of the two expansion parameters, the amplitude parameter $\\alpha$ and the long wavelength (or shallowness) parameter $\\beta$, is developed. Unlike the heuristic approaches found in the literature, when modifications are made in the equation for surface elevation itself, the procedure starts from the consistently truncated asymptotic expansions for unidirectional waves, a counterpart of the Boussinesq system of equations for the surface elevation and the bottom velocity, from which the leading order and higher order equations for the surface elevation can be obtained by iterations. The relations between the orders of the two small parameters are taken in the form $\\beta=O(\\alpha^n)$ and $\\alpha=O(\\beta^m)$ with $n$ and ...
AERATION OF THE ICE-COVERED WATER POOLS USING THE WAVE FLOW AERATOR
Directory of Open Access Journals (Sweden)
Solomin E.E
2013-12-01
Full Text Available This article describes the technical advantages and economic benefits of the ice-covered pool aeration plants consuming power from renewable energy sources. We made a comparative evaluation of the wave flow-aeration method and other methods of pool aeration. We showed the indexes and the characteristics of the wave flow-maker for aeration of ice-covered pools on the territory of Russia. We also made calculations of the economic benefits of aeration plants using the devices converting renewable energy. The project can be scaled and extended to the territory of the CIS, Europe, USA and Canada in the changing climate conditions and the variety of feed reservoirs around the world.
Size distribution of oceanic air bubbles entrained in sea-water by wave-breaking
Resch, F.; Avellan, F.
1982-01-01
The size of oceanic air bubbles produced by whitecaps and wave-breaking is determined. The production of liquid aerosols at the sea surface is predicted. These liquid aerosols are at the origin of most of the particulate materials exchanged between the ocean and the atmosphere. A prototype was designed and built using an optical technique based on the principle of light scattering at an angle of ninety degrees from the incident light beam. The output voltage is a direct function of the bubble diameter. Calibration of the probe was carried out within a range of 300 microns to 1.2 mm. Bubbles produced by wave-breaking in a large air-sea interaction simulating facility. Experimental results are given in the form of size spectrum.
AN EXPLICIT MULTI-CONSERVATION FINITE-DIFFERENCE SCHEME FOR SHALLOW-WATER-WAVE EQUATION
Institute of Scientific and Technical Information of China (English)
Bin Wang
2008-01-01
An explicit multi-conservation finite-difference scheme for solving the spherical shallowwater-wave equation set of barotropic atmosphere has been proposed. The numerical scheme is based on a special semi-discrete form of the equations that conserves four basic physical integrals including the total energy, total mass, total potential vorticity and total enstrophy. Numerical tests show that the new scheme performs closely like but is much more time-saving than the implicit multi-conservation scheme.
Water Temperature and Concentration Measurements Within the Expanding Blast Wave of a High Explosive
2011-03-15
housing was made of 1018 steel , and the gauge roof was extended to shield the opto- mechanical components from the primary blast wave. The input fiber...regions of each image indicate the steel frame and support crossbars of the gauge. This set of images provides a sense of the speed with which the shock was...University Press) [3] Peuker J M, Lynch P, Krier H and Glumac N 2009 Optical depth measurements of fireballs from aluminized high explosives Opt
Kamath, Arun
2015-01-01
The application of computational fluid dynamics (CFD) methods to various problems in the field of coastal and ocean engineering is gaining importance due to the level of detail and accuracy offered by these methods. With the advances made in the computing power over the last decade and anticipated future increase in computational power, large and complex problems can be handled using CFD modeling. The PhD study aims at the development of a CFD-based numerical wave tank, vali...
Langone, Leonardo; Miserocchi, Stefano; Boldrin, Alfredo; Turchetto, Margherita; Foglini, Federica; Trincardi, Fabio
2010-05-01
The dense water forming in the North Adriatic (NAdDW) spreading southward along the Italian continental shelf, sinks in the Southern Adriatic basin through particular cascading events. Such events are seasonal, occurring specially in April, with variable intensity. These phenomena control the water mass mixing, the deep ocean ventilation, the behaviour of deep ecosystems, the formation of complex erosive and depositional bedforms and the abyssal export and burial of nutrients and carbon. Because of the NadDW formation is linked to climate factors (frequency, duration and size of Bura winds), the temporal variations of the NadDW dispersion into the Southern Adriatic allow to make inferences of the impact of recent climate changes on the ecosystems of the deep Mediterranean Sea. Previous research projects (EuroStrataform, HERMES) acquired a large data set of bathymetric, side-scan sonar (TOBI) and Chirp sonar profiles, which were used to build detailed morpho-bathymetric maps of the Southern Adriatic margin. There, the seabed is extremely complex, characterized by a large variety of bedforms (sediment waves, erosive scours, longitudinal furrows and giant comet marks). A branch of the cascading NAdDW is confined and accelerated through the Bari canyon where it produces a strong current capable of reaching down-slope velocities greater than 60 cm s-1 near the bottom at ~600 m of water depth, eroding the canyon thalweg and entraining large amounts of fine-grained sediment. At the exit of the canyon, in water depth greater than 800 m, the current becomes less confined, spreads laterally and generates an 80-km2-wide field of mud waves; these bedforms migrate up current and show amplitudes up to 50 m and wavelengths of about 1 km. Cruise IMPACT-09 of RV Urania was carried out in the Southern Adriatic Sea from 17-30 March 2009 with main scope of studying the impact of NadDW cascading events on the deep ecosystems of the Southern Adriatic. Experiments planned in the cruise
Druzhinin, Oleg A.; Troitskaya, Yuliya I.; Zilitinkevich, Sergej S.
2016-04-01
The detailed knowledge of the interaction of wind with surface water waves is necessary for correct parameterization of turbulent exchange at the air-sea interface in prognostic models. At sufficiently strong winds, sea-spray-generated droplets interfere with the wind-waves interaction. The results of field experiments and laboratory measurements (Andreas et al., JGR 2010) show that mass fraction of air-borne spume water droplets increases with the wind speed and their impact on the carrier air-flow may become significant. Phenomenological models of droplet-laden marine atmospheric boundary layer (Kudryavtsev & Makin, Bound.-Layer Met. 2011) predict that droplets significantly increase the wind velocity and suppress the turbulent air stress. The results of direct numerical simulation (DNS) of a turbulent particle-laden Couette flow over a flat surface show that inertial particles may significantly reduce the carrier flow vertical momentum flux (Richter & Sullivan, GRL 2013). The results also show that in the range of droplet sizes typically found near the air-sea interface, particle inertial effects are significant and dominate any particle-induced stratification effects. However, so far there has been no attempt to perform DNS of a droplet-laden air-flow over waved water surface. In this report, we present results of DNS of droplet-laden, turbulent Couette air-flow over waved water surface. The carrier, turbulent Couette-flow configuration in DNS is similar to that used in previous numerical studies (Sullivan et al., JFM 2000, Shen et al., JFM 2010, Druzhinin et al., JGR 2012). Discrete droplets are considered as non-deformable solid spheres and tracked in a Lagrangian framework, and their impact on the carrier flow is modeled with the use of a point-force approximation. The droplets parameters in DNS are matched to the typical known spume-droplets parameters in laboratory and field experiments. The DNS results show that both gravitational settling of droplets and
Kirezci, Cagil; Ozyurt Tarakcioglu, Gulizar
2016-04-01
Coastal development in Black Sea has increased in recent years. Therefore, careful monitoring of the storms and verification of numerical tools with reliable data has become important. Previous studies by Kirezci and Ozyurt (2015) investigated extreme events in Black Sea using different wind datasets (NCEP's CFSR and ECMWF's operational datasets) and different numerical tools (SWAN and Wavewatch III). These studies showed that significant effect to results is caused by the deep water source-sink terms (wave growth by wind, deep water dissipation of wave energy (whitecapping) and deep water non-linear wave-wave interactions). According to Timmermans(2015), uncertainty about wind forcing and the process of nonlinear wave-wave interactions are found to be dominant in numerical wave modelling. Therefore, in this study deep water source and sink term solution approaches of 3rd generation numerical tool (SWAN model) are tested, validated and compared using the selected extreme storms in Black Sea. 45 different storms and storm like events observed in Black Sea between years 1994-1999 are selected to use in the models. The storm selection depends on the instrumental wave data (significant wave heights, mean wave period and mean wave direction) obtained in NATO-TU Waves project by the deep water buoy measurements at Hopa, Sinop, Gelendzhik, and wind data (mean and peak wind speeds, storm durations) of the regarding events. 2 different wave growth by wind with the corresponding deep water dissipation terms and 3 different wave -wave interaction terms of SWAN model are used in this study. Wave growth by wind consist of two parts, linear growth which is explained by Cavaleri and Malanotte-Rizzoli(1981),and dominant exponential growth. There are two methods in SWAN model for exponential growth of wave, first one by Snyder et al. (1981), rescaled in terms of friction velocity by Komen et. al (1984) which is derived using driving wind speed at 10m elevation with related drag
Keune, Jessica; Sulis, Mauro; Kollet, Stefan; Wada, Yoshihide
2017-04-01
Recent studies indicate that anthropogenic impacts on the terrestrial water cycle lead to a redistribution of water resources in space and time, can trigger land-atmosphere feedbacks, such as the soil moisture-precipitation feedback, and potentially enhance convection and precipitation. Yet, these studies do not consider the full hydrologic cycle from the bedrock to the atmosphere or apply simplified hydrologic models, neglecting the connection of irrigation to water withdrawal and groundwater depletion. Thus, there is a need to incorporate water resource management in 3D hydrologic models coupled to earth system models. This study addresses the impact of water resource management, i.e. irrigation and groundwater abstraction, on land-atmosphere feedbacks through the terrestrial hydrologic cycle in a physics-based soil-vegetation-atmosphere system simulating 3D groundwater dynamics at the continental scale. The integrated Terrestrial Systems Modeling Platform, TerrSysMP, consisting of the three-dimensional subsurface and overland flow model ParFlow, the Community Land Model CLM3.5 and the numerical weather prediction model COSMO of the German Weather Service, is set up over the European CORDEX domain in 0.11° resolution. The model closes the terrestrial water and energy cycles from aquifers into the atmosphere. Anthropogenic impacts are considered by applying actual daily estimates of irrigation and groundwater abstraction from Wada et al. (2012, 2016), as a source at the land surface and explicit removal of groundwater from aquifer storage, respectively. Simulations of the fully coupled system are performed over the 2003 European heat wave and compared to a reference simulation, which does not consider human interactions in the terrestrial water cycle. We study the space and time characteristics and evolution of temperature extremes, and soil moisture and precipitation anomalies influenced by human water management during the heat wave. A first set of simulations
Directory of Open Access Journals (Sweden)
C. T. Duba
2012-05-01
Full Text Available Using the shallow water equations for a rotating layer of fluid, the wave and dispersion equations for Rossby waves are developed for the cases of both the standard β-plane approximation for the latitudinal variation of the Coriolis parameter f and a zonal variation of the shallow water speed. It is well known that the wave normal diagram for the standard (mid-latitude Rossby wave on a β-plane is a circle in wave number (ky,kx space, whose centre is displaced −β/2 ω units along the negative kx axis, and whose radius is less than this displacement, which means that phase propagation is entirely westward. This form of anisotropy (arising from the latitudinal y variation of f, combined with the highly dispersive nature of the wave, gives rise to a group velocity diagram which permits eastward as well as westward propagation. It is shown that the group velocity diagram is an ellipse, whose centre is displaced westward, and whose major and minor axes give the maximum westward, eastward and northward (southward group speeds as functions of the frequency and a parameter m which measures the ratio of the low frequency-long wavelength Rossby wave speed to the shallow water speed. We believe these properties of group velocity diagram have not been elucidated in this way before. We present a similar derivation of the wave normal diagram and its associated group velocity curve for the case of a zonal (x variation of the shallow water speed, which may arise when the depth of an ocean varies zonally from a continental shelf.
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John V. Ringwood
2013-08-01
Full Text Available Combining offshore wind and wave energy converting apparatuses presents a number of potentially advantageous synergies. To facilitate the development of a proposed floating platform combining these two technologies, proof of concept scale model testing on the wave energy converting component of this platform has been conducted. The wave energy component is based on the well-established concept of the oscillating water column. A numerical model of this component has been developed in the frequency domain, and the work presented here concerns the results of this modelling and testing. The results of both are compared to assess the validity and usefulness of the numerical model.
DEFF Research Database (Denmark)
Bigoni, Daniele; Engsig-Karup, Allan Peter; Eskilsson, Claes
2016-01-01
of the evolution of waves. The model is analyzed using random sampling techniques and nonintrusive methods based on generalized polynomial chaos (PC). These methods allow us to accurately and efficiently estimate the probability distribution of the solution and require only the computation of the solution...... at different points in the parameter space, allowing for the reuse of existing simulation software. The choice of the applied methods is driven by the number of uncertain input parameters and by the fact that finding the solution of the considered model is computationally intensive. We revisit experimental...
High-order Finite Difference Solution of Euler Equations for Nonlinear Water Waves
DEFF Research Database (Denmark)
Christiansen, Torben Robert Bilgrav; Bingham, Harry B.; Engsig-Karup, Allan Peter
2012-01-01
The incompressible Euler equations are solved with a free surface, the position of which is captured by applying an Eulerian kinematic boundary condition. The solution strategy follows that of [1, 2], applying a coordinate-transformation to obtain a time-constant spatial computational domain which...... with a two-dimensional implementation of the model are compared with highly accurate stream function solutions to the nonlinear wave problem, which show the approximately expected convergence rates and a clear advantage of using high-order finite difference schemes in combination with the Euler equations....
MEASURING METAL SULFIDE COMPLEXES IN OXIC RIVER WATERS WITH SQUARE WAVE VOLTAMMETRY. (R825395)
A sulfide identification protocol was developed to quantify specific metal sulfides that could exist in river water. Using a series of acid additions, nitrogen purges, and voltammetric analyses, metal sulfides were identified and semiquantified in three specific gr...
The doping concentration and physical properties measurement of silicon water using tera hertz wave
Energy Technology Data Exchange (ETDEWEB)
Park, Sung Hyeon; Oh, Gyung Hwan; Kim, Hak Sung [Dept. of Mechanical Convergence Engineering, Hanyang University, Seoul(Korea, Republic of)
2017-02-15
In this study, a tera hertz time domain spectroscopy (THz-TDS) imaging technique was used to measure doping concentration and physical properties (such as refractive index and permittivity) of the doped silicon (Si) wafers. The transmission and reflection modes with an incidence angle of 30° were employed to determine the physical properties of the doped Si wafers. The doping concentrations of the prepared Si wafers were varied from 10{sup 14} to 10{sup 18} in both N-type and P-type cases. Finally, the correlation between the doping concentration and the power of the THz wave was determined by measuring the powers of the transmitted and reflected THz waves of the doped Si wafers. Additionally, the doped thickness, the refractive index, and permittivity of each doped Si wafer were calculated using the THz time domain waveform. The results indicate that the THz-TDS imaging technique is potentially a promising technique to measure the doping concentration as well as other optical properties (such as the refractive index and permittivity) of the doped Si wafer.
Galaxy-like organization of floaters at the air-water interface of Faraday waves
Alarcón, Héctor; Périnet, Nicolas; Gutiérrez, Pablo; Gordillo, Leonardo; Mujica, Nicolás
2016-11-01
The fluid properties mismatch across an air-liquid interface allows to trap particles at it. These particles are called floaters and appear in nature at different scales: plankton, organic residues, and garbage, all relevant for the oceanic ecosystem. In static systems they tend to attract or repel each other, depending on their wetting properties and buoyancy. When they are subjected to a flow, such as surface waves, they may drift and form structures at the interface. In a recent work using PIV on Faraday waves, we have measured a streaming flow that emerges inside the bulk, leading to a slow circulation of fluid particles across the liquid. The flow is mainly generated by the viscous shearing at the walls of the container. Our new experiments show that this flow has a remarkable effect on the drift of small hydrophilic particles (floaters), which leads to a rare arrangement of the floaters that resemble rotating galaxies. The forcing amplitude determines the galaxy shape, controlling the number and the length of its arms as well as its rotation velocity. Thanks to FONDECYT POSTDOCTORADO N°3160341, N°3140522, N°3140550.
Directory of Open Access Journals (Sweden)
James L Falter
Full Text Available We present a three-dimensional hydrodynamic-biogeochemical model of a wave-driven coral-reef lagoon system using the circulation model ROMS (Regional Ocean Modeling System coupled with the wave transformation model SWAN (Simulating WAves Nearshore. Simulations were used to explore the sensitivity of water column carbonate chemistry across the reef system to variations in benthic reef metabolism, wave forcing, sea level, and system geomorphology. Our results show that changes in reef-water carbonate chemistry depend primarily on the ratio of benthic metabolism to the square root of the onshore wave energy flux as well as on the length and depth of the reef flat; however, they are only weakly dependent on channel geometry and the total frictional resistance of the reef system. Diurnal variations in pCO(2, pH, and aragonite saturation state (Ω(ar are primarily dependent on changes in net production and are relatively insensitive to changes in net calcification; however, net changes in pCO(2, pH, and Ω(ar are more strongly influenced by net calcification when averaged over 24 hours. We also demonstrate that a relatively simple one-dimensional analytical model can provide a good description of the functional dependence of reef-water carbonate chemistry on benthic metabolism, wave forcing, sea level, reef flat morphology, and total system frictional resistance. Importantly, our results indicate that any long-term (weeks to months net offsets in reef-water pCO(2 relative to offshore values should be modest for reef systems with narrow and/or deep lagoons. Thus, the long-term evolution of water column pCO(2 in many reef environments remains intimately connected to the regional-scale oceanography of offshore waters and hence directly influenced by rapid anthropogenically driven increases in pCO(2.
Directory of Open Access Journals (Sweden)
Huizhang Yang
2013-01-01
Full Text Available New Lax pairs of a shallow water wave model of generalized KdV equation type are presented. According to this Lax pair, we constructed a new spectral problem. By using this spectral problem, we constructed Darboux transformation with the help of a gauge transformation. Applying this Darboux transformation, some new exact solutions including double-soliton solution of the shallow water wave model of generalized KdV equation type are obtained. In order to visually show dynamical behaviors of these double soliton solutions, we plot graphs of profiles of them and discuss their dynamical properties.
Directory of Open Access Journals (Sweden)
Eric-Gustavo Bautista
2015-01-01
Full Text Available We obtain asymptotic formulas for the reflection/transmission coefficients of linear long water waves, propagating in a harbor composed of a tapered and slender region connected to uniform inlet and outlet regions. The region with variable character obeys a power-law. The governing equations are presented in dimensionless form. The reflection/transmission coefficients are obtained for the limit of the parameter κ2≪1, which corresponds to a wavelength shorter than the characteristic horizontal length of the harbor. The asymptotic formulas consider those cases when the geometry of the harbor can be variable in width and depth: linear or parabolic among other transitions or a combination of these geometries. For harbors with nonlinear transitions, the parabolic geometry is less reflective than the other cases. The reflection coefficient for linear transitions just presents an oscillatory behavior. We can infer that the deducted formulas provide as first approximation a practical reference to the analysis of wave reflection/transmission in harbors.
A Determination of an Abrupt Motion of the Sea Bottom by Using Snapshot Data of Water Waves
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T. S. Jang
2012-01-01
Full Text Available This paper presents an inverse problem and its solution procedure, which are aimed at identifying a sudden underwater movement of the sea bottom. The identification is mathematically shown to work with a known snapshot data of generated water wave configurations. It is also proved that the problem has a unique solution. However, the inverse problem is involved in an integral equation of the first kind, resulting in an ill-posed problem in the sense of stability. That is, the problem lacks solution stability properties. To overcome the difficulty of solution instability, in this paper, a stabilization technique, called regularization, is incorporated in the present solution procedure for the identification of the sea bottom movement. A numerical experiment is presented to demonstrate that the proposed (numerical solution procedure operates.
Study on the dynamic behavior of matters using laser-driven shock waves in the water confinement
Yu, Hyeonju; Yoh, Jack J.
2015-06-01
The strain rates achievable in laser-driven shock experiments overlap with gas gun and can reach much higher values. The laser-based method also has advantages in terms of system size, cost, repeatability, and controllability. In this research, we aim to measure equation of state, Hugoniot elastic limit, strain rate, and compressive yield strength of target samples by making use of the velocity interferometer or the VISAR. High pressure shock wave is generated by a Q-switched Nd:YAG laser operating at 1.064 μm wavelength with pulse energy up to 3 joules and 9 ns pulse duration. All the experiments are conducted in the water confinement to increase the peak stresses to an order of GPa. Furthermore, quantitative comparisons are made to the existing shock data in order to emphasize the novelty of the proposed setup which is relatively simple and reliable. Corresponding author.
On alpha stable distribution of wind driven water surface wave slope
Joelson, Maminirina
2008-01-01
We propose a new formulation of the probability distribution function of wind driven water surface slope with an $\\alpha$-stable distribution probability. The mathematical formulation of the probability distribution function is given under an integral formulation. Application to represent the probability of time slope data from laboratory experiments is carried out with satisfactory results. We compare also the $\\alpha$-stable model of the water surface slopes with the Gram-Charlier development and the non-Gaussian model of Liu et al\\cite{Liu}. Discussions and conclusions are conducted on the basis of the data fit results and the model analysis comparison.
Electron impact ionization of liquid and gaseous water: a single-center partial-wave approach
Energy Technology Data Exchange (ETDEWEB)
Champion, C [Universite Paul Verlaine-Metz, Laboratoire de Physique Moleculaire et des Collisions, ICPMB (FR CNRS 2843), Institut de Physique, 1 bd Arago, 57078 Metz Cedex 3 (France)], E-mail: champion@univ-metz.fr
2010-01-07
In this work, we report a unified methodology to express the molecular wavefunctions of water in both vapor and liquid phases by means of a single-center approach. These latter are then used as input data in a theoretical treatment-previously published and successfully tested-for describing the water ionization process in the first Born approximation (Champion et al 2006 Phys. Rev. A 73 012717). The multi-differential and total cross sections also obtained are reported for the two thermodynamical phases investigated and compared to the rare existing experimental and theoretical data.
The numerical simulation of green water loading including vessel motions and the incoming wave field
Kleefsman, K.M.Theresa; Loots, G. Erwin; Veldman, Arthur E.P.; Buchner, Bas; Bunnik, Tim; Falkenberg, Erik
2005-01-01
This paper presents results from simulation of green water loading including vessel motions. The simulation is performed through a domain decomposition: the far field and ship motions are calculated by potential theory and are used to simulate the local flow around the deck of an offshore floater us
Mercury-Free Analysis of Lead in Drinking Water by Anodic Stripping Square Wave Voltammetry
Wilburn, Jeremy P.; Brown, Kyle L.; Cliffel, David E.
2007-01-01
The analysis of drinking water for lead, which has well-known health effects, is presented as an instructive example for undergraduate chemistry students. It allows the students to perform an experiment and evaluate to monitor risk factors and common hazard of everyday life.
Troitskaya, Yuliya; Lebedev, Sergey; Soustova, Irina; Rybushkina, Galina; Papko, Vladislav; Baidakov, Georgy; Panyutin, Andrey
by the improved threshold algorithm. The possibility of determination of significant wave height (SWH) in the lakes through a two-step adaptive retracking is also studied. Calculation of the parameter SWH for Gorky Reservoir from May 2010 to March 2014 showed the anomalously high values of SWH, derived from altimetry data [15], which means that the calibration of this SWH for inland waters is required. Calibration ground measurements were performed at Gorky reservoir in 2011-2013, when wave height, wind speed and air temperature were collected by equipment placed on a buoy [15] collocated with Jason-1 and Jason-2 altimetry data acquisition. The results obtained on the basis of standard algorithm and method for adaptive re-tracking at Rybinsk , Gorky , Kuibyshev , Saratov and Volgograd reservoirs and middle-sized lakes of Russia: Chany, Segozero, Hanko, Oneko, Beloye, water areas of which are intersected by the Jason-1,2 tracks, were compared and their correlation with the observed data of hydrological stations in reservoirs and lakes was investigated. It was noted that the Volgograd reservoir regional re-tracking to determine the water level , while the standard GDR data are practically absent. REFERENCES [1] AVISO/Altimetry. User Handbook. Merged TOPEX/ POSEIDON Products. Edition 3.0. AVISO. Toulouse., 1996. [2] C.M. Birkett et al., “Surface water dynamics in the Amazon Basin: Application of satellite radar altimetry,” J. Geophys. Res., vol. 107, pp. 8059, 2002. [3] G. Brown, “The average impulse response of a rough surface and its applications,” IEEE Trans. Antennas Propagat., vol. 25, pp. 67-74, 1977. [4] I.O. Campos et al., “Temporal variations of river basin waters from Topex/Poseidon satellite altimetry. Application to the Amazon basin,” Earth and Planetary Sciences, vol. 333, pp. 633-643, 2001. [5] A.V. Kouraev et al., “Ob’ river discharge from TOPEX/Poseidon satellite altimetry (1992-2002),” Rem. Sens. Environ., vol. 93, pp. 238-245, 2004
Leijala, Ulpu; Björkqvist, Jan-Victor; Johansson, Milla M.; Pellikka, Havu
2017-04-01
Future coastal management continuously strives for more location-exact and precise methods to investigate possible extreme sea level events and to face flooding hazards in the most appropriate way. Evaluating future flooding risks by understanding the behaviour of the joint effect of sea level variations and wind waves is one of the means to make more comprehensive flooding hazard analysis, and may at first seem like a straightforward task to solve. Nevertheless, challenges and limitations such as availability of time series of the sea level and wave height components, the quality of data, significant locational variability of coastal wave height, as well as assumptions to be made depending on the study location, make the task more complicated. In this study, we present a statistical method for combining location-specific probability distributions of water level variations (including local sea level observations and global mean sea level rise) and wave run-up (based on wave buoy measurements). The goal of our method is to obtain a more accurate way to account for the waves when making flooding hazard analysis on the coast compared to the approach of adding a separate fixed wave action height on top of sea level -based flood risk estimates. As a result of our new method, we gain maximum elevation heights with different return periods of the continuous water mass caused by a combination of both phenomena, "the green water". We also introduce a sensitivity analysis to evaluate the properties and functioning of our method. The sensitivity test is based on using theoretical wave distributions representing different alternatives of wave behaviour in relation to sea level variations. As these wave distributions are merged with the sea level distribution, we get information on how the different wave height conditions and shape of the wave height distribution influence the joint results. Our method presented here can be used as an advanced tool to minimize over- and
Making Waves: Seismic Waves Activities and Demonstrations
Braile, S. J.; Braile, L. W.
2011-12-01
The nature and propagation of seismic waves are fundamental concepts necessary for understanding the exploration of Earth's interior structure and properties, plate tectonics, earthquakes, and seismic hazards. Investigating seismic waves is also an engaging approach to learning basic principles of the physics of waves and wave propagation. Several effective educational activities and demonstrations are available for teaching about seismic waves, including the stretching of a spring to demonstrate elasticity; slinky wave propagation activities for compressional, shear, Rayleigh and Love waves; the human wave activity to demonstrate P- and S- waves in solids and liquids; waves in water in a simple wave tank; seismic wave computer animations; simple shake table demonstrations of model building responses to seismic waves to illustrate earthquake damage to structures; processing and analysis of seismograms using free and easy to use software; and seismic wave simulation software for viewing wave propagation in a spherical Earth. The use of multiple methods for teaching about seismic waves is useful because it provides reinforcement of the fundamental concepts, is adaptable to variable classroom situations and diverse learning styles, and allows one or more methods to be used for authentic assessment. The methods described here have been used effectively with a broad range of audiences, including K-12 students and teachers, undergraduate students in introductory geosciences courses, and geosciences majors.