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Showing papers on "Wave flume published in 1992"


Book
01 Nov 1992
TL;DR: The main objective of as mentioned in this paper is to describe from a deterministic point of view the sediment transport in the general wave-current situation, which is useful for students with a background in basic hydrodynamics.
Abstract: The main objective of the book is to describe from a deterministic point of view the sediment transport in the general wave-current situation. For this purpose, the book is divided into two major parts. The first part of the book is related to flow and turbulence in combined wave-current. This part covers the turbulent wave boundary layer, bed friction in combined wave-current motion, turbulence in the surf zone, and wave-driven currents in the long- and cross-shore direction. The second part treats the sediment transport as a result of the wave-current action. This part includes an introduction to basic sediment transport concepts, distribution of suspended sediment in the sheet flow regime, description of bedforms formed by current and waves, and their influence on sediment transport pattern. Finally, the modelling of cross- and long-shore sediment transport is described. This book is useful for students with a background in basic hydrodynamics.

926 citations


Journal ArticleDOI
TL;DR: In this article, a wave flume with regular waves of very small amplitude-to-wavelength ratio (less than 0.01) was used to validate the oscillating surface pressure theory applied to wave energy absorption by oscillating water column (OWC) devices.
Abstract: Experiments were performed in a wave flume with regular waves of very small amplitude-to-wavelength ratio (less than 0.01). Their purpose was mainly the validation of the oscillating surface pressure theory of Sarmento and Falcao (1985) applied to wave energy absorption by oscillating water column (OWC) devices. Experimental and theoretical curves for the efficiency and for the reflection and transmission coefficients were obtained and compared. The test also included the validation of the two-wave-gauge experimental procedure used to decouple direct and reflected wave trains, as well as the effects of increasing the depth of immersion of the OWC overhang on the efficiency-wave period curves.

81 citations



Book
01 Dec 1992
TL;DR: In this paper, both regular and irregular waves were used to move sand with a mean diameter of 0.18 mm placed on the seaward side of a simulated vertical seawall.
Abstract: : Laboratory experiments consisting of 22 tests were conducted in the 6-ft-wide wave flume at the US Army Engineer Coastal Engineering Research Center (CERC) to evaluate methods for estimating wave-induced scour depth (Sl) at vertical seawalls. Existing scour prediction methods range from rule-of-thumb estimates to semi-empirically derived equations. In the study, both regular and irregular waves were used to move sand with a mean diameter of 0.18 mm placed on the seaward side of a simulated vertical seawall. In the initial part of the study, 18 cases were run using irregular waves with various water depths, seawall locations relative to still-water level (swl), wave heights, and wave periods. All of the bottom profiles generated by the 18 irregular wave tests in the study supported a rule-of-thumb method, which states that maximum scour depth will be less than or equal to the incident unbroken deepwater wave height Ho, or S/Ho less than or equal to 1. When additional data from other studies (which used regular waves exclusively) were considered, the rule of thumb did not hold for all cases. To examine the effects of regular versus irregular waves in movable-bed laboratory studies, four additional test cases were run using regular waves having comparable water depths, wave heights, wave periods, and seawall locations relative to swl to four of the irregular wave test cases. In each of the four regular wave cases, scour depth exceeded scour depths associated with comparable irregular wave tests. On the average, scour depth increased by approximately 15 percent with regular water conditions.

33 citations


01 Jan 1992
TL;DR: In this paper, an engineering procedure for calculating the static wave/current global load on a typical space frame structure has been synthesized and proposed for inclusion in the 20th edition of API-RP2A.
Abstract: Since results from the Ocean Test Structure were presented at Civil Engineering in the Oceans IV in 1979, there have been numerous laboratory experiments and a few full-scale measurements of local and global wave forces on offshore platforms. The laboratory experiments have shed considerable light on such phenomena as current blockage within dense structures, wave and current shielding in conductor arrays, wave and current interaction, three-dimensional wave kinematics, and the effects of wake encounter, surface roughness, and cylinder orientation on C d and C m . From these data, an engineering procedure for calculating the static wave/current global load on a typical space frame structure has been synthesized and proposed for inclusion in the 20th edition of API-RP2A. This procedure is still grounded on the Morison equation for calculation of local forces and a higher-order regular wave theory for calculation of two-dimensional wave kinematics, but involves a sequence of simple modifications to the traditional methodology.

22 citations


Journal ArticleDOI
TL;DR: In this article, an extension to the Morison equation including Duffing oscillator-type force terms is postulated through knowledge of the flow mechanisms, which is used to curve-fit measured force time-histories from velocity timehistories, generated experimentally from various sources.

11 citations


Proceedings ArticleDOI
22 Dec 1992
TL;DR: In this paper, a new optical instrument has been designed for combined slope/height measurements of the small-scale structure of the ocean surface, which takes stereo images of the specular reflexes on the water surface representing slope zero-crossings in a sector of about 30 X 40 cm2.
Abstract: A new optical instrument has been designed for combined slope/height measurements of the small-scale structure of the ocean surface. The compact and rugged sensor head contains two light sources and a short-base CCD stereo camera setup mounted 4 - 6 m above the water surface and looking straight down onto the water surface. It takes stereo images of the specular reflexes on the water surface representing slope zero-crossings in a sector of about 30 X 40 cm2. The height of the reflexes can be determined with a precision of about 2 mm. Experiments have been performed in the wind/wave flume of Delft Hydraulics, at the Scripps pier, and at the Noordwijk research platform in the North Sea. In these campaigns, a total of about half a million stereo images have been taken with continuous time series of up to 8 min at 30 frames/s. Some preliminary results are shown.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

11 citations


01 Oct 1992
TL;DR: The propagation of waves from offshore to onshore is a difficult problem due to the mathematical complexities of the governing equations and the degree of uncertainty of the bathymetry over which the waves must travel.
Abstract: The propagation of waves from offshore to onshore is a difficult problem due to the mathematical complexities of the governing equations and the degree of uncertainty of the bathymetry over which the waves must travel. In this lecture, the various methods of transforming offshore wave trains to shallow water are discussed. First, single wave trains will be covered and then the shoaling of spectra will be introduced. Various wave transformation methods, such as ray tracing and parabollic modelling, are covered.

6 citations


01 Jan 1992
TL;DR: In this paper, it was found that the spectra of the transmitted waves are generally quite different in total energy and in the frequency-wise distribution of the energy compared to the incident wave spectra.
Abstract: The results of this study have important application to the design of small boat marinas protected from incident waves by breakwaters that may be overtopped during extreme wave events. This overtopping results in transmitted waves with significantly different characteristics than the incident waves. Experiments were conducted with two different breakwater sections, regular and irregular waves, and with several depths representing storm surge effects. It was found that the spectra of the transmitted waves are generally quite different in total energy and in the frequency-wise distribution of the energy compared to the incident wave spectra. The important frequencies associated with the transmitted wave are up to twice that of the incident waves. The transmission characteristics for both regular and irregular incident waves are best defined by the root mean square of the wave amplitudes.

6 citations


14 Jun 1992
TL;DR: In this paper, the authors examined how knowledge accumulated in this field under shallow water conditions can be used for deep water and showed results of large-scale model tests on the breaking wave impact loading and dynamic response of a caisson breakwater.
Abstract: Little information is available on deep water breaking waves and their effect on structures and structural members. This paper examines how knowledge accumulated in this field under shallow water conditions can be used for deep water. Some results of large-scale model tests on the breaking wave impact loading and dynamic response of a caisson breakwater are presented which may be useful for structures in deep water.

5 citations


14 Jun 1992
TL;DR: In this article, a two-dimensional numerical wave tank has been developed using a boundary integral scheme, where waves are generated by a hinged "wave-maker" at one end of the "wave flume" and they are absorbed by a "damper" at the other end.
Abstract: A two-dimensional numerical wave tank has been developed using a boundary integral scheme. Waves are generated by a hinged "wave-maker" at one end of the "wave flume" and they are absorbed by a "damper" at the other end. In deep water,m the wave forms are solely determined by the motion of the wave-maker. A single-frequency sinusoidal motion of the paddle results in a steady progressive wave of the same frequency. Starting from the still- water condition, the first few waves are seen to disappear as they travel towards the other end of the tank, which is exactly what happens in a real wave flume. Comparisons between Stokes wave kinematics and that of monochromatic waves generated in the numerical wave tank have been carried out and the results are in good agreement with experimental observations.

Book ChapterDOI
01 Jan 1992
TL;DR: In this article, a computer model named "WAVE" is developed to simulate the development of coastal environments affected by wave-induced erosion, transport, and deposition, which combines wave refraction, wavecurrent interaction, wave set-up, wind, oscillatory wave motion, longshore currents, rip currents, and nearshore sediment transport.
Abstract: A computer model named “WAVE” has been developed to simulate the development of coastal environments affected by wave-induced erosion, transport, and deposition. The model simulates wave refraction, wavecurrent interaction, wave set-up, wind, oscillatory wave motion, longshore currents, rip currents, and nearshore sediment transport. Combining these processes into a unified model provides a process-response model that is dynamic in that the effects of wave energy on an evolving coastline are simulated through time. A series of equations based upon the principles of fluid dynamics as applied to coastal hydraulics, are used to calculate nearshore currents within a grid network representing a coastal area. The equations assume that mass and momentum are conserved as waves shoal towards shore, and are solved by integrating over the total water depth, and time-averaging over a single wave period. A finite-difference scheme provides solutions for the wave equations at each node in the grid. Once nearshore currents are calculated, sediment transport is initiated using empirical relationships that are effective in predicting raes of littoral transport.

01 Jan 1992
TL;DR: In this paper, a laboratory generated deep-water breaking wave is followed from its initial steepening, through the breaking phase, until after the plunging jet has re-entered the water.
Abstract: The development of a laboratory generated deep-water breaking wave is followed from its initial steepening, through the breaking phase, until after the plunging jet has re-entered the water. The surface profiles and internal kinematics are recorded photographically in a purpose-built wave flume, and compared with a time-stepping numerical model, up until the point of breading. After breaking, further kinematic measurements are presented and the problems associated with measuring the post-breaking turbulence identified and discussed.


01 Jan 1992
TL;DR: In this paper, the authors proposed a numerical method for the absorption of all outgoing nonlinear waves at a moving open boundary and a modified time-stepping technique for tracing particles of a material distributed on the free-surface.
Abstract: In this paper, the authors propose a numerical method for the absorption of all outgoing nonlinear waves at a moving open boundary and a modified time-stepping technique for tracing particles of a material distributed on the free-surface. The basis of these methods is the mixed Euler-Lagrange description. A control parameter, the beta-value, is introduced to control the lateral movement of nodal points on the moving free surface as prescribed by the Lagrangian description. It is shown that the beta-value does not affect the free surface profiles but does affect the trajectory of the nodal points on the free surface. The application of the beta-value to the moving boundary is useful in evaluating the average mass transport, and is also valuable in terms of dealing with the nonlinear interaction between the free surface and the large-amplitude motion of floating bodies. Our open boundary scheme is based on an extension of the Orlanski boundary condition. The crucial factor in this scheme is determining the time-dependent phase velocity on the moving open boundary. We examine the stability of our open boundary scheme by changing the prediction points on the free surface near the open boundary. The trajectory of the water particles and the average mass transport as calculated by our numerical model agree well with the 2nd-order Stokes wave. It is demonstrated that nonlinear irregular waves can pass through the moving open boundary without significant reflection, and this is confirmed by comparing the generated wave profiles for two different wave flume lengths.

Journal ArticleDOI
TL;DR: In this paper, a multivariate or joint probability density function for wave forces has been developed for the peak force distribution of wave forces, where peak force is defined by the Morison equation.