Showing papers on "Wave flume published in 2004"
TL;DR: In this article, the morphodynamic response of the nearshore zone of an embayed beach induced by wave groups is examined with a numerical model, which utilizes the nonlinear shallow water equations to phase resolve the mean and infragravity motions in combination with an advection-diffusion equation for the sediment transport.
Abstract: [1] The morphodynamic response of the nearshore zone of an embayed beach induced by wave groups is examined with a numerical model. The model utilizes the nonlinear shallow water equations to phase resolve the mean and infragravity motions in combination with an advection-diffusion equation for the sediment transport. The sediment transport associated with the short-wave asymmetry is accounted for by means of a time-integrated contribution of the wave nonlinearity using stream function theory. The two-dimensional (2-D) computations consider wave group energy made up of directionally spread, short waves with a zero mean approach angle with respect to the shore normal, incident on an initially alongshore uniform barred beach. Prior to the 2-D computations, the model is calibrated with prototype flume measurements of waves, currents, and bed level changes during erosive and accretive conditions. The most prominent feature of the 2-D model computations is the development of an alongshore quasi-periodic bathymetry of shoals cut by rip channels. Without directional spreading, the smallest alongshore separation of the rip channels is obtained, and the beach response is self-organizing in nature. Introducing a small amount of directional spreading (less than 2°) results in a strong increase in the alongshore length scales as the beach response changes from self-organizing to being quasi-forced. A further increase in directional spreading leads again to smaller length scales. The hypothesized correlation between the observed rip spacing and wave group forced edge waves over the initially alongshore uniform bathymetry is not found. However, there is a correlation between the alongshore length scales of the wave group-induced quasi-steady flow circulations and the eventual alongshore spacing of the rip channels. This suggests that the scouring associated with the quasi-steady flow induced by the initial wave groups triggers the development of rip channels via a positive feedback mechanism in which the small scour holes start attracting more and more discharge.
348 citations
TL;DR: In this article, landslide generated impulse waves were investigated in a two-dimensional physical laboratory model based on the generalized Froude similarity, and four wave types were determined: weakly nonlinear oscillatory wave, nonlinear transition wave, solitary-like wave and dissipative transient bore.
Abstract: Landslide generated impulse waves were investigated in a two-dimensional physical laboratory model based on the generalized Froude similarity. The recorded wave profiles were extremely unsteady and nonlinear. Four wave types were determined: weakly nonlinear oscillatory wave, non-linear transition wave, solitary-like wave and dissipative transient bore. Most of the generated impulse waves were located in the intermediate water depth wave regime. Nevertheless the propagation velocity of the leading wave crest closely followed the theoretical approximations for a solitary wave. Between 4 and 50% of the kinetic slide impact energy propagated outward in the impulse wave train. The applicability ranges of the classical nonlinear wave theories to landslide generated impulse waves were determined. The main wave characteristics were related to the landslide parameters driving the entire wave generation process. The slide Froude number was identified as the dominant parameter. The physical model results were compared to the giant rockslide generated impulse wave which struck the shores of the Lituya Bay, Alaska, in 1958.
298 citations
TL;DR: In this article, a simple parameter study with trigonometric functions to get an idea about the numerical performance of the empirical mode decomposition (EMD) is performed, and the main results of estimating relative standardized errors made between analytically exact defined sine waves and disintegrated intrinsic functions as well as their specific influence on each other are determined.
218 citations
TL;DR: Experimental evidence that the tail of the probability density function for wave height strongly depends on the Benjamin-Feir index and the fact that large-amplitude waves in random spectra may result from the modulational instability is confirmed.
Abstract: We study random surface gravity wave fields and address the formation of large-amplitude waves in a laboratory environment. Experiments are performed in one of the largest wave tank facilities in the world. We present experimental evidence that the tail of the probability density function for wave height strongly depends on the Benjamin-Feir index (BFI)---i.e., the ratio between wave steepness and spectral bandwidth. While for a small BFI the probability density functions obtained experimentally are consistent with the Rayleigh distribution, for a large BFI the Rayleigh distribution clearly underestimates the probability of large events. These results confirm experimentally the fact that large-amplitude waves in random spectra may result from the modulational instability.
179 citations
TL;DR: In this paper, the maximum depth-integrated wave momentum flux (MSF) was proposed for characterizing the wave contribution to nearshore coastal processes on beaches and at coastal structures.
67 citations
TL;DR: In this paper, the authors investigated the generation and propagation of water waves in a numerical viscous wave flume and showed that the wave height attenuation caused by the energy dissipation in the wave motion was consistent with the theoretical results.
Abstract: This study investigated the generation and propagation of water waves in a numerical viscous wave flume. The numerical scheme developed by Huang and collaborators for solving the unsteady two-dimensional Navier–Stokes equations for wavemaking problems was employed to generate different incident waves, including small- and finite-amplitude waves and solitary waves. The accuracy of the numerical results for the wave and velocity profiles was verified by comparison with the analytical solutions. The wave propagation in a numerical wave flume was also investigated. For periodic gravity waves on finite water depth, the results showed that waves with larger Ursell numbers are more stable than those with smaller Ursell numbers. The propagation of solitary waves in the channel is stable. For stable waves, the wave height attenuation caused by the energy dissipation in the wave motion was shown to be consistent with the theoretical results.
50 citations
TL;DR: In this paper, the authors used zero down-crossing analyses of bed profiles measured by acoustic means along a 4-m transect normal to the ripple crests to estimate wave-generated ripple height, η, and wavelength, λ.
Abstract: [1] Experiments in a large-scale wave flume using regular and irregular waves with periods between 4 s and 6 s and heights between 0.2 m and 1.55 m have examined the formation of wave-generated ripples using sediment beds composed of four grain sizes (D50 = 0.349 mm, 0.329 mm, 0.220 mm, and 0.162 mm) in a water depth of approximately 4 m. Estimates of wave-generated ripple height,η, and wavelength, λ, were obtained using zero down-crossing analyses of bed profiles measured by acoustic means along a 4-m transect normal to the ripple crests. Further information pertaining to λ was obtained from bed images obtained using scanning sonar. The analyses reported here focus on the sequence bedforms that evolved in response to stepwise increases and decreases in wave height. Results show that ripples for the most part are suborbital in nature and do not conform well to empirical equations used frequently to predict η and λ values in the field. On the basis of the present data, two new equations for prediction of η and λ are obtained and their use in field situations where hydrodynamic and sedimentary conditions favor development of suborbital bedforms is recommended.
43 citations
TL;DR: In this article, a numerical investigation of random wave slamming on superstructures of marine structures in the splash zone is presented, where the impact pressures on the underside of the structure are computed based on the improved volume of fluid method (VOF).
43 citations
TL;DR: In this article, an experimental study of the Eulerian drift induced by weakly asymmetrical progressive waves in the bottom boundary layer over rippled beds in the transitional flow regime is presented.
32 citations
01 Sep 2004
TL;DR: In this paper, an efficient parabolic, "ray-tracing" solver was used for the propagation of directional random waves from offshore, and it was shown that waves with broad, but not narrow, directional spread are well predicted without taking diffraction into account.
Abstract: Long-term nearshore wave climate prediction requires an efficient solution method for the propagation of directional random waves from offshore. Predictions of laboratory data for waves over submerged shoals indicate that waves with broad, but not narrow, directional spread are well predicted without taking diffraction into account, and an efficient parabolic, ‘ray-tracing’ solver may thus be used. Application to the complex coastal bathymetry off East Anglia indicates that inshore wave climate is generally only slightly affected by the degree of directionality, tidal currents, and wind forcing over the propagation region. It thus seems realistic to define inshore wave climate for a range of offshore conditions, defined only by wave height, period and direction, and of course tidal level, using an efficient parabolic solver.
26 citations
TL;DR: In this paper, the threshold condition for ripple formation under asymmetrical oscillatory flows on an artificially roughened bed was examined using a wave flume and three types of sand beds were constructed with three kinds of well-sorted sand with similar density, but different diameters.
TL;DR: In this paper, a 3D sediment transport model with waves and currents is presented, which is not synchronously driven by both the wave field and the flow field, and the model is shown to be stable.
Abstract: Most of the existing sediment transport models are not synchronously driven by both the wave field and the flow field. This paper describes a 3D sediment transport model with waves and currents dir...
Journal Article•
TL;DR: According to the theory of sediment movement and the energy dissipation of wave-water and referred to the bottom sediment discharge formula developed by Dou in river flow, a formula for calculating bottom sediment transport rate has been derived.
Abstract: The mechanism of sediment transport under the coexisting action of wind, waves and tide is sediment-uplift, move and carrying by wave particle orbit velocity and transport by the resultant velocity of wave mass-transport current, wind brown current and tide-current. According to the theory of sediment movement and the energy dissipation of wave-water and referred to the bottom sediment discharge formula developed by Dou in river flow, a formula for calculating bottom sediment transport rate has been derived. The calculated sudden sedimentation amount in the access channel of Huanghua Port by the formula is close to the measured data.Moreover, fluid mud transport formulas derived before have been improved. This paper is a summary concerned this subject since 1987
01 Jan 2004
TL;DR: In this paper, the results of a flume investigation of surface wave motion over a fluidized bed are presented, and it is shown that a resonant wave interaction between a surface wave and two interfacial waves at the interface of the fresh water and the fluidised bed is a strong mechanism for instability of the interface and the subsequent mixing of the layers.
Abstract: The results of a flume investigation of surface wave motion over a fluidized bed are presented. It is shown that a resonant wave interaction between a surface wave and two interfacial waves at the interface of the fresh water and the fluidized bed is a strong mechanism for instability of the interface and the subsequent mixing of the layers. The interfacial waves are subharmonic to the surface wave and form a standing wave at the interface. The interaction is investigated theoretically using a fully viscous interaction analysis. It is shown that surface wave height and viscous effects are the determining factors in the instability mechanism. The results indicate that the net effect of viscosity on the interaction process is to suppress the interfacial waves.Copyright © 2004 by ASME
TL;DR: In this article, a 2D numerical wave flume based on VOF method, called CADMAS-SURF, was applied to hydraulic pressures acting on the structures because of the flooded water.
Abstract: The 2D numerical wave flume based on VOF method, called CADMAS-SURF, was applied to hydraulic pressures acting on the structures because of the flooded water. The validity of this model is verified due to the comparison with experimental data. Then the numerical simulation of the hydraulic pressure was carried out. The numerical results suggested the importance of detached breakwaters to decrease the amount of flooded water and hydraulic pressures.
TL;DR: In this article, the development of a spectral feedback control technique capable of generating precise Gaussian wave packets and incipient breaking waves at predetermined locations in a laboratory wave flume is described.
Abstract: This paper deals with the development of a spectral feedback control technique capable of generating precise Gaussian wave packets and incipient breaking waves at predetermined locations in a laboratory wave flume The design of the system includes the development of algorithms to generate the mathematical equations that define the wave packets and the spectral control algorithm for continuously correcting the system frequency response characteristics Descriptions of the mathematical model of the Gaussian wave packets and their corresponding frequency spectra are given, along with the procedure used for spectral feedback compensation, especially with regard to handling the phase The results of comparing wave packets generated by open and closed loop control systems are discussed Experimental results are also used to demonstrate the adequacy of the spectral feedback technique to accurately generate particular Gaussian wave packets with particular emphasis on the important role played by the phase in reconstruction of transient signals In addition, a method for generating breaking waves is explained and the results of experiments presented Using the technique developed, resultant breaking wave packets of similar shape can be repeatedly produced at a predetermined location along the flume
01 Jan 2004
TL;DR: Workpackage 5 as discussed by the authors aims to use numerical simulation of wave over-topping in order to solve the problem of suspected scale effects and to improve existing codes in such a way as they are able to simulate wave overtopping.
Abstract: The main objective of Workpackage 5 is to use numerical simulation of wave overtopping in order to solve the problem of suspected scale effects. A second, related, objective is to improve existing codes in such a way as they are able to simulate wave overtopping in a reliable way. The final, single, objective is to numerically model long waves on the shallow foreshore at Petten in order to understand the phenomenon of long waves and their effect on overtopping. This report deals with the work undertaken towards the first two objectives, the simulations undertaken for objective 3 are the subject of a separate report entitled Influence of low-frequency waves on wave overtopping by M.R.A. van Gent and C.C. Giarrusso and published by WL | Delft hydraulics in November 2003. Realistic simulations of wave overtopping require numerical methods which are able accurately to simulate the shoaling, breaking and possible overturning of waves prior to their impact on the seawall. It is a further requirement that the simulation continues after impact, modelling the formation of the overtopping jet and the reflection of the wave. The research groups at Manchester Metropolitan University (MMU) and the University of Gent (UGent) have been working in parallel on the development of such numerical codes. The MMU code, AMAZON-SC, is a numerical wave flume based on the free surface capturing approach. While the UGent code, LVOF, is a numerical wave basin based on the volume of fluid approach. This report describes the progress of these numerical methods, in order to address the first two objectives of Workpackage 5. Their application to various cases, is also discussed, including: a test problem involving wave overtopping of a smooth sea-dike, wave overtopping at Samphire Hoe and an investigation of scale effects on rough impermeable structures. The Report begins with a general introduction, followed by a section describing AMAZONSC (the MMU code), a section describing LVOF (the UGent code) and then some general conclusions.
TL;DR: In this article, the maximum depth-integrated wave momentum flux is proposed for characterizing wave processes at coastal structures, which is useful for developing meaningful physical formulations between the waves and the process occurring at the structure.
Abstract: A new parameter representing the maximum depth-integrated wave momentum flux occurring in a wave is proposed for characterizing wave processes at coastal structures. This parameter I s physically relevant descriptor of wave forcing; and having units of force, it is useful for developing meaningful physical formulations between the waves and the process occurring at the structure. This paper overviews the development of the wave momentum flux parameter, and it presents an empirical formula was estimating the parameter for nonlinear steady waves of permanent form. New formulas for irregular wave rump on plane, impermeable slopes are given in terms of wave momentum flux parameter as an example application.
01 Feb 2004
TL;DR: In this paper, the authors investigated wave overtopping on a laboratory wave flume and found that the over-topping rate for stepped seawalls is smaller than that for smooth seawalls.
Abstract: Wave overtopping on gentle slope seawalls was investigated in a laboratory wave flume. Overtopping rate was measured by a water tank placed behind the seawall. Velocity and water depth of overtopping water were simultaneously measured by using a Laser Doppler Velocimeter and a wave gage. It was found that overtopping rate for stepped seawalls is smaller than that for smooth seawalls. Steps on the front face of stepped seawalls reduce the wave reflection coefficient. Velocity of overtopping water has a peak just after the initiation of each overtopping event and overtopping volume could be estimated by using the velocity and water depth of overtopping water.
01 Jan 2004
TL;DR: In this paper, the characteristics of wave energy variations and transmission coefficient at the rear of the permeable submerged breakwater installed in the irregular wave field were investigated, and the spectral peak was shown to be converged within the significant wave period in the one-row and two-row submerged breakwaters in the case of non-breaking conditions.
Abstract: The different types of coastal structures have been constructed for the protection of coastal region from the incident waves. Among them, the permeable submerged breakwater has been widely used as a wave dissipater and sediment transport controller because of its excellent advantages in scenery effects, construction efficiency and environment aspects. This study numerically investigated the characteristics of wave energy variations and transmission coefficient at the rear of the permeable submerged breakwater installed in the irregular wave field. To analyze it"s performance numerically, a two-dimensional numerical wave flume based on VOF method was used. A frequency spectral analysis showed that the spectral peak moved to the short-period in the one-row submerged breakwater, and the wave energy was distributed evenly for the whole period in the two-row submerged breakwater in the case of breaking on the submerged breakwater. The spectral peak was shown to be converged within the significant wave period at the rear of the permeable submerged breakwater in the case of non-breaking conditions. From the result of transmission coefficients analysis, it was confirmed that a considerable quantity of wave energy was transmitted to the rear of the permeable submerged breakwater in the case of non-breaking rather than breaking.
01 Apr 2004
TL;DR: In this article, the authors investigate the influence of suspended sediment on sand wave dynamics and employ a vertical sediment concentration profile model to describe the phase-lag due to the time difference in pick-up and settling.
Abstract: seas, such as the North Sea, sand waves can be observed forming regular bed patterns. Present numerical sand wave models only take bed load transport into account, the most important transport mechanism for sand waves. We expect the suspended sediment transport becomes significant for full amplitude sand waves. Within this study, we investigate the influence of suspended sediment on sand wave dynamics. Firstly, we model the suspended sediment transport with a depth-averaged transport formula. Furthermore, we will employ a vertical sediment concentration profile model. The latter approach is able to describe the phase-lag due to the time difference in pick-up and settling. The suspended load formulation enables modelling influences of wind waves on sediment transport.
Journal Article•
TL;DR: Based on the principle of wave generation in physical flume, the simulation of wave generator is presented by setting the movement border as a wave generator in the FLUENT, and the numerical simulation of the regularly two-dimensional wave is realized.
Abstract: In the purpose of overcoming the shortages of physical model experiment, such as high investment and less similarities with the prototype,numerical models are used in the research of hydraulics. Based on the principle of wave generation in physical flume, the simulation of wave generator is presented by setting the movement border as a wave generator in the FLUENT, and the numerical simulation of the regularly two-dimensional wave is realized. It is also being recognized on the change of the wave height which varies according to the movement cycles, the vibration amplitude and the coordinate of the wave generator. The analysis of wave feature indicates that the numerically generated waves are comparable to the waves formed by physical wave generator. Using this method, the irregularly two-dimensional wave and random wave can also be realized by changing the boundary conditions.
TL;DR: In this paper, the AMAZON-SC multiphase numerical wave flume was used to simulate experiments of violent wave overtopping conducted in the Edinburgh University 20m Wave Flume.
Abstract: This paper describes how storm waves breaking in the surf zone and crashing over seawalls are a natural phenomenon with the potential for causing enormous damage. Much of the existing design guidance for seawalls considers the mean overtopping discharge on the structure. However, under impacting conditions the overtopping volumes associated with individual events can be significant. Under the UK Engineering and Physical Sciences and Research Council (EPSRC) funded VOWS project and the European Commission funded CLASH project work has been undertaken using both laboratory investigation and computer simulation in order to quantify these wave by wave overtopping volumes. This paper discusses the application of the AMAZON-SC multiphase numerical wave flume developed by Manchester Metropolitan University to simulate experiments of violent wave overtopping conducted in the Edinburgh University 20m wave flume.
Journal Article•
TL;DR: In this paper, the long non-linear waves in shallow water propagation were studied experimentally and numerically, and the Fourier analysis of measured and computed time history of water elevations with second order incident boundary condition showed that there is periodic transformation for different component of waves along wave flume.
Abstract: The long non-linear waves in shallow water propagation is studied experimentally and numerically. First order and second order incident boundary condition on fixed incident boundary are derived for numerical simulations, based on the cnoidal motion of wave maker paddle, which shows that the prediction with second order incident boundary condition is more accurate than the prediction with first order incident boundary condition. The Fourier analysis of measured and computed time history of water elevations with second order incident boundary condition shows that there is periodic transformation for different component of waves along wave flume, while no periodic transformation with first order incident boundary condition.
01 Jan 2004
TL;DR: In this paper, the mean of the boundary element method was used to model the generation and subsequent propagation of irregular waves in a numerical wave flume, where random waves were generated by a piston type wave generator at one end of the flume with the Mitsuyasu-Bretschneider spectrum used as the target spectrum for the generation.
Abstract: The modeling of generation and subsequent propagation of irregular waves in a numerical wave flume is performed by mean of the boundary element method. Random waves are generated by a piston-type wave generator at one end of the flume with the Mitsuyasu-Bretschneider spectrum used as the target spectrum for the generation. An artificial absorbing beach is placed at the other end of the flume to minimize wave reflection. Surface fluctuations are described by use of the Lagrangian description, and finite difference is adopted for the approximation of time derivative. To monitor the developments of the waves, a number of pseudo wave gauges are installed along the tank. Through comparison of the spectra from those gauges with the target spectrum, satisfactory results can be obtained from the present numerical scheme.
Journal Article•
TL;DR: In this article, a new method based on light refraction is specified for the measurement of wave surface elevation in wave flume via imaging technology, which can be taken as a digital method.
Abstract: Some authors have developed a few methods of measuring wave slopes based on light refraction, including the measurement method via the distribution of light intensity or color under water. A new method based on light refraction is specified for the measurement of wave surface elevation in wave flume via imaging technology. A plane painted with black and white stripes is put on the flume floor as an indication plane, which can be arranged easily and cheaply. Compared with the previous methods, the present method is less sensitive to the noise and nonlinear effects of optical process, which can be taken as a digital method. The CCD camera is fixed above the flume with its optical axis arranged vertically to grab the images of stripes modulated by the wave surface. The modulated value can be calculated from the Hilbert transform, and then the wave surface elevation can be obtained. The algorithm and experimental procedure are specified in detail, and some experimental results are provided to show the validity of the present method.
01 Jan 2004
TL;DR: In this article, Koshizuka et al. developed a numerical simulation method for breaking and run-upping waves on a beach, based on the particle analysis, which is applied to analyze the run-up height of long-period waves such as Tsunami or solitary wave.
Abstract: There are a lot of researches on the run-up of waves which propagate onto plain beaches. The results from them have been contributing to the estimations of wave run-up height for the real planning of maritime structures and the managements of coastal zones. Contrary to this, however, not enough knowledge has been given on the run-up phenomena of long-period waves on complex beaches, because of the difficulty of numerical simulations of breaking and run-upping waves and restrictions of experimental equipments for long-period waves.Koshizuka has developed a numerical simulation method for breaking and run-upping waves on a beach, based on the particle analysis. This Koshizuka's method is applied to analyze the run-up height of long-period waves such as Tsunami or solitary wave. The results are verified by Synolakis's experimental data for the run-up heights for the plain beach.