Wave–current interactions: an experimental and numerical study. Part 2. Nonlinear waves

1990 ◽  
Vol 216 ◽  
pp. 505-536 ◽  
Author(s):  
G. P. Thomas
Keyword(s):  
Numerical Study ◽  
Finite Depth ◽  
Finite Amplitude ◽  
Two Dimensions ◽  
Arbitrary Distribution ◽  
Current Interaction ◽  
Particle Velocities ◽  
The Waves ◽  
A Current ◽  
Theory And Experiment

The interaction between a regular wavetrain and a current possessing an arbitrary distribution of vorticity, in two dimensions, is considered for waves of finite amplitude. A numerical model is constructed, primarily for use in the finite depth regime, extending the work of Dalrymple (1973, 1977) and this is used to predict the wavelength and the particle velocities under the waves. These predictions agree very well with experimentally obtained data and the importance of the vorticity in the wave–current interaction is clarified. Amplitude and wavelength modulations are considered for finite amplitude waves on a slowly varying irrotational current; moderate agreement is found between theory and experiment.

Wave-current interactions: an experimental and numerical study. Part 1. Linear waves

1981 ◽  
Vol 110 ◽  
pp. 457-474 ◽  
Author(s):  
G. P. Thomas
Keyword(s):  
Numerical Study ◽  
Current Model ◽  
Two Dimensions ◽  
Constant Current ◽  
Arbitrary Distribution ◽  
Current Profile ◽  
A Value ◽  
Linear Waves ◽  
Particle Velocities ◽  
The Waves

The interaction between a regular wavetrain and an adverse current containing an arbitrary distribution of vorticity, in two dimensions, is studied using a linear theory. The model is used to predict the wavelength and the particle velocities under the waves and these are found to agree well with experimentally obtained data for a number of current profiles. Surprisingly accurate predictions, for the profiles considered, were also obtained from an irrotational wave–current model in which the constant current has a value equal to the depth-averaged mean of the measured current profile. The changes in the wave amplitude as the current magnitude increases are predicted using an irrotational slowly varying model with good agreement being found between theory and experiment.

scholarly journals INTEGRAL PROPERTIES FOR VOCOIDAL THEORY AND APPLICATIONS

1982 ◽  
Vol 1 (18) ◽  
pp. 56
Author(s):  
G.P. Bleach
Keyword(s):  
Reference Frame ◽  
Mass Flux ◽  
Reference Frames ◽  
Wave Theory ◽  
Finite Depth ◽  
Finite Amplitude ◽  
Zero Mass ◽  
Finite Amplitude Waves ◽  
Exact Relations ◽  
The Waves

A comparison is made between two reference frames that can each be used to define "still water" for finite amplitude waves on water of finite depth. The reference frame characterized by zero mass flux due to the waves is used to find some exact relations between the wave integral properties. The averaged Lagranian (wave action) approach and the energy/momentum approach to the interaction of finite amplitude waves with slowly-varying currents are also derived in this reference frame. Results in many cases are simpler than those in the more commonly chosen reference frame characterized by zero mean horizontal velocity under the waves. An application of the integral properties is made to Vocoidal wave theory, which is defined in the zero mass flux frame. It is shown that the rotation present in the orbital velocity field of Vocoidal waves is not always negligible.

A NUMERICAL STUDY OF NONLINEAR PROPAGATION OF DISTURBANCES IN TWO-DIMENSIONS

1996 ◽  
Vol 04 (03) ◽  
pp. 291-319 ◽  
Author(s):  
TONY W.H. SHEU ◽  
C.C. FANG
Keyword(s):  
Acoustic Field ◽  
Numerical Study ◽  
Element Model ◽  
Analytic Solutions ◽  
Finite Amplitude ◽  
Euler System ◽  
Two Dimensions ◽  
Nonlinear Propagation ◽  
Characteristic Model ◽  
Transport Problems

In the spirit of the method of characteristics, we present in this paper a generalized Taylor-Galerkin finite element model to simulate the nonlinear propagation of finite-amplitude disturbances. In a nonlinear Euler system, the multi-dimensional formulation is constructed through the conservation variables. Noticeable is that the scheme is found to exhibit high-phase-accuracy, together with minimal numerical damping. This scheme, therefore, is best-suited to simulation of disturbances in an acoustic field. To begin with, we validate the characteristic model by simulating two transport problems amenable to analytic solutions. Motivated by the apparent success, we apply the proposed third-order accurate upwind model to investigate a truly nonlinear acoustic field. The present analysis is intended to elucidate to what extent the nondissipative, nondispersive and isotropic characteristics pertaining to three wave modes of the acoustic system are still valid.

scholarly journals THE INTERACTION OF SMALL AND FINITE AMPLITUDE LONG WAVES AND CURRENTS

1984 ◽  
Vol 1 (19) ◽  
pp. 67 ◽  
Author(s):  
F. Raichlen ◽  
J.J. Lee
Keyword(s):  
Power Plants ◽  
Cooling Water ◽  
Breaking Waves ◽  
Finite Amplitude ◽  
Offshore Structure ◽  
Wave Refraction ◽  
Steady Current ◽  
Waves And Currents ◽  
The Waves ◽  
A Current

The interaction of waves and currents is important for many engineering problems. For example, when considering forces on marine structures, the velocity and acceleration field must be defined, and thus the manner in which a current interacts with small and finite amplitude waves must be understood. When the current is large and oblique to the waves, the direction of the force on an offshore structure may change significantly with depth introducing a torsional moment. Wave refraction and the concomitant attenuation or amplification of waves are also affected by offshore currents. An example is the effect on incident waves of offshore currents induced by the discharge of cooling water from coastal-sited power plants. This current can modify the direction and magnitude of approaching waves, and by these changes the breaking waves at the shore and the nearshore sediment transport associated with these waves may be changed. A number of theoretical studies have been conducted on various aspects of wave-current interactions; see Peregrine (1976). One theoretical study, Thomas (1981), will be used in this investigation. Careful experiments in this area are limited; several are: Iwagaki and Asano (1980), Sarpkaya (1957), and Thomas (1981). Each of these has given attention to certain aspects of small amplitude wave-current interactions. The experiments are difficult to conduct because of the problems inherent in introducing waves into a flume with a steadyuniform current or conversely a current into a wave tank with permanent waves. Certain features of these experimental problems can be seen through the following two examples. If a plunger-wave machine were used and located at one end of a flume in which a steady current is flowing, although the waves would be developing as they interact with the current, the previously steady current would be changed to an unsteady one by the periodic blockage of the flow by the plunger. If the waves are generated at one end of the tank and allowed to develop, and a current is introduced from the bottom of the tank, this current must expand to the full depth of the flow; hence, the waves propagate on a developing current. Therefore, comparisons to theory are, to some extent, difficult to realize, because the theory generally assumes wavecurrent interactions when each is fully developed.

scholarly journals A study of the waves and boundary layers due to a surface pressure on a uniform stream of a slightly viscous liquid of finite depth

2006 ◽  
Vol 2006 ◽  
pp. 1-24
Author(s):  
Arghya Bandyopadhyay
Keyword(s):  
Numerical Study ◽  
Surface Displacement ◽  
Finite Depth ◽  
Surface Boundary ◽  
Long Distance ◽  
Surface Boundary Layer ◽  
Linear Waves ◽  
Propagating Waves ◽  
The Waves ◽  
Asymptotic Forms

The 2D problem of linear waves generated by an arbitrary pressure distributionp0(x,t)on a uniform viscous stream of finite depthhis examined. The surface displacementζis expressed correct toO(ν)terms, for small viscosityν, with a restriction onp0(x,t). Forp0(x,t)=p0(x)eiωt, exact forms of the steady-state propagating waves are next obtained for allxand not merely forx≫0which form a wave-quartet or a wave-duo amid local disturbances. The long-distance asymptotic forms are then shown to be uniformly valid for largeh. For numerical and other purposes, a result essentially due to Cayley is used successfully to express these asymptotic forms in a series of powers of powers ofν1/2orν1/4with coefficients expressed directly in terms of nonviscous wave frequencies and amplitudes. An approximate thickness of surface boundary layer is obtained and a numerical study is undertaken to bring out the salient features of the exact and asymptotic wave motion in question.

Effects of wave-current interaction on the waves, cold-water mass and transport of diluted water in the Beibu Gulf

2020 ◽  
Vol 39 (1) ◽  
pp. 25-40
Author(s):  
Jingling Yang ◽  
Shaocai Jiang ◽  
Junshan Wu ◽  
Lingling Xie ◽  
Shuwen Zhang ◽  
...  
Keyword(s):  
Water Mass ◽  
Cold Water ◽  
Beibu Gulf ◽  
Cold Water Mass ◽  
Current Interaction ◽  
The Waves

Riser Fatigue Due to Currents and Waves

2002 ◽  
Author(s):  
C. Le Cunff ◽  
E. Fontaine ◽  
F. Biolley
Keyword(s):  
Modal Analysis ◽  
Environmental Conditions ◽  
Navier Stokes ◽  
Vortex Induced Vibrations ◽  
Two Factors ◽  
Shedding Frequency ◽  
The Waves ◽  
Structural Mode ◽  
A Current

Fatigue due to environmental conditions is studied on a top-tensioned riser. The fatigue is due to two factors. First, the waves produce a displacement of the top of the riser, which excites the structure. Secondly, currents create vortices behind the structures. The phenomenon is then referred to as vortex-induced vibrations (VIV), whereby the vortices can lock onto a structural mode through the shedding frequency. In the present paper, we have two objectives. The first is to compare the fatigue estimates given either by a modal analysis or by Navier-Stokes calculations for a riser in a current. The second is to determine if studying the wave and current effects separately produces conservative results or if they must be studied together.

scholarly journals Theoretical Studies of Convectively Forced Mesoscale Flows in Three Dimensions. Part II: Shear Flow with a Critical Level

2010 ◽  
Vol 67 (3) ◽  
pp. 694-712 ◽  
Author(s):  
Ji-Young Han ◽  
Jong-Jin Baik
Keyword(s):  
Shear Flow ◽  
Gravity Waves ◽  
Wind Direction ◽  
Critical Level ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Finite Depth ◽  
Vertical Displacement ◽  
Two Dimensions ◽  
Three Dimensions

Abstract Convectively forced mesoscale flows in a shear flow with a critical level are theoretically investigated by obtaining analytic solutions for a hydrostatic, nonrotating, inviscid, Boussinesq airflow system. The response to surface pulse heating shows that near the center of the moving mode, the magnitude of the vertical velocity becomes constant after some time, whereas the magnitudes of the vertical displacement and perturbation horizontal velocity increase linearly with time. It is confirmed from the solutions obtained in present and previous studies that this result is valid regardless of the basic-state wind profile and dimension. The response to 3D finite-depth steady heating representing latent heating due to cumulus convection shows that, unlike in two dimensions, a low-level updraft that is necessary to sustain deep convection always occurs at the heating center regardless of the intensity of vertical wind shear and the heating depth. For deep heating across a critical level, little change occurs in the perturbation field below the critical level, although the heating top height increases. This is because downward-propagating gravity waves induced by the heating above, but not near, the critical level can hardly affect the flow response field below the critical level. When the basic-state wind backs with height, the vertex of V-shaped perturbations above the heating top points to a direction rotated a little clockwise from the basic-state wind direction. This is because the V-shaped perturbations above the heating top is induced by upward-propagating gravity waves that have passed through the layer below where the basic-state wind direction is clockwise relative to that above.

Numerical Study of Two Vessels Seakeeping in Waves

2014 ◽  
Author(s):  
Dexin Zhan ◽  
Don Bass ◽  
David Molyneux
Keyword(s):  
Objective Function ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Wave Direction ◽  
Small Motion ◽  
Head Waves ◽  
Close Proximity ◽  
Connection Line ◽  
Sheltering Effect ◽  
The Waves

This paper presents a numerical study of seakeeping in regular waves for two vessels in close proximity using commercial seakeeping software HydroStar and an in-house code MOTSIM. The objective was to study the possible sheltering effect of the larger vessel (FPSO) on the smaller one (OSV) during personnel transfer between the two vessels, where one vessel was at some angle relative to the other vessel and there was no connection line between them. The study mainly focused on the OSV motion resulting from the interaction of the FPSO when the OSV was at different headings and wave directions. Initially the OSV motions close to the FPSO (and parallel) were compared with those for the OSV alone. For an un-parallel position of the two vessels, an objective function based on the OSV RAOs motion in roll, pitch and heave directions was used to optimize the OSV position. Finally comparisons between HydroStar and MOTSIM results are provided. The main conclusions are: 1) When the FPSO and OSV are located in parallel, the OSV motions in sway, roll and yaw are larger than the single OSV motions in head waves while surge, heave and pitch are almost the same. The OSV motions in most of the six degrees of freedom are smaller than the single OSV motions when the waves are from other directions (always on the port side of the FPSO), which means that there is a sheltering effect. 2) The simulation results from different OSV rotation angles show that the hydrodynamic interaction between the FPSO and OSV e.g. the sheltering effect is related to the OSV angle and the wave heading. The objective function in roll, pitch and heave RAOs indicates that the OSV should maintain a close to parallel position with the FPSO to minimize motion when the waves come from the port side of the FPSO from 180 to 240 degrees. When the wave direction is around 240 degrees the OSV should have relatively small motion in waves for any OSV rotation angle. 3) A comparison of HydroStar and MOTSIM results shows that the MOTSIM results of a single vessel seakeeping simulation is in a good agreement with HydroStar. In two vessels situation more validation work needs to be done.

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