Method for calculating forces produced by irregular waves
Esso1
01 Mar 1970-Journal of Petroleum Technology (Society of Petroleum Engineers)-Vol. 22, Iss: 03, pp 359-367
TL;DR: In this paper, a new method is described and evaluated for calculating wave forces on offshore structures based on an extension of Airy theory for two-dimensional waves and uses a linear filtering technique to calculate wave forces as a function of time for wave profiles of arbitrary shape and length.
Abstract: A new method is described and evaluated for calculating wave forces on offshore structures. It is based on an extension of Airy theory for two-dimensional waves and uses a linear filtering technique to calculate wave forces as a function of time for wave profiles of arbitrary shape and length. It is especially useful for evaluating the forces exerted on offshore structures by a sequence of irregular storm waves. The accuracy of the method is checked by comparison with measured hurricane-wave forces. (Author)
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15 Mar 1996-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, the authors describe an experimental investigation in which a large number of water waves were focused at one point in space and time to produce a large transient wave group, which is consistent with an increase in the local energy density, and the development of large velocity gradients near the water surface.
Abstract: This paper describes an experimental investigation in which a large number of water waves were focused at one point in space and time to produce a large transient wave group. Measurements of the water surface elevation and the underlying kinematics are compared with both a linear wave theory and a second-order solution based on the sum of the wave-wave interactions identified by Longuet-Higgins & Stewart (1960). The data shows that the focusing of wave components produces a highly nonlinear wave group in which the nonlinearity increases with the wave amplitude and reduces with increasing bandwidth. When compared with the first- and second-order solutions, the wave-wave interactions produce a steeper wave envelope in which the central wave crest is higher and narrower, while the adjacent wave troughs are broader and less deep. The water particle kinematics are also strongly nonlinear. The accumulated experimental data suggest that the formation of a focused wave group involves a significant transfer of energy into both the higher and lower harmonics. This is consistent with an increase in the local energy density, and the development of large velocity gradients near the water surface. Furthermore, the nonlinear wave-wave interactions are shown to be fully reversible. However, when compared to a linear solution there is a permanent change in the relative phase of the free waves. This explains the downstream shifting of the focus point (Longuet-Higgins 1974), and appears to be similar to the phase changes which result from the nonlinear interaction of solitons travelling at different velocities (Yuen & Lake 1982).
266Â citations
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01 Jan 2008
TL;DR: In this article, a model of Rogue Wave Shapes in Shallow Water is presented, along with an analytical model of Large Amplitude Internal Solitary Waves in the North Sea.
Abstract: Preface.- Freak Waves: Peculiarities of Numerical Simulations.- Rogue Waves in High-Order Nonlinear Schrodinger Models.- Non-Gaussian Properties of Shallow Water Waves in Crossing Seas.- Modeling of Rogue Wave Shapes in Shallow Water.- Runup of Long Irregular Waves on Plane Beach.- Symbolic Computation for Nonlinear Wave Resonances.- Searching for Factors that Limit Observed Extreme Maximum Wave Height Distributions in the North Sea.- Extremes and Decadal Variations of the Northern Baltic Sea Wave Conditions.- Extreme Waves Generated by Cyclones in Guadeloupe.- An Analytical Model of Large Amplitude Internal Solitary Waves.
180Â citations
TL;DR: In this paper, a time domain model is applied to a three-dimensional point absorber wave energy converter, where the relative velocities between the body and the waves increase, and the non-linear hydrostatic restoring moment is calculated by a cubic polynomial function fit to laboratory test results.
115Â citations
TL;DR: In this paper, three different definitions of phase speed are used to calculate phase velocities of the wave crests from detailed surface elevation measurements, and the ratios of these fluid particle speeds to crest phase speeds are consistently less than unity.
Abstract: Experiments were performed that test the kinematic breaking criterion, which states that the horizontal fluid particle velocity at the surface of a crest exceeds the local phase speed of the crest prior to breaking. Three different definitions of phase speed are used to calculate phase velocities of the wave crests from detailed surface elevation measurements. The first definition, based on the equivalent linear wave, is constant over the wavelength of the wave. The second, based on partial Hilbert transforms of the surface elevation data, is local in space and time giving instantaneous values at all space and time measurements. The third, based on the speed of the position of the crest maximum, is local in time but not in space. Particle image velocimetry is used to obtain horizontal components of fluid particle velocity at the surface of crests of breaking and nonbreaking waves produced in a wave flume using the chirp-pulse focusing technique. The ratios of these fluid particle speeds to crest phase speeds are calculated and are consistently less than unity. The speed ratio for the rounded crest of a plunging breaker is at most 0.81, implying that the kinematic breaking criterion is far from satisfied. The ratio for the more sharply pointed crest of a spilling breaker is at most 0.95, implying that the kinematic breaking criterion is closer to being satisfied. Thus, for the breaking waves in this study the kinematic breaking criterion is not satisfied for any of the three definitions of phase speed and so it cannot be regarded as a universal predictor of wave breaking.
109Â citations
TL;DR: In this article, the velocity profiles under crest of a total of 62 different steep wave events in deep water are measured in laboratory using particle image velocimetry, and the experimental velocities have been put on a nondimensional form in the following way: from the wave record (at a fixed point) the (local) trough-to-trough period, TTT and the maximal elevation above mean water level, hm of an individual steep wave event are identified.
94Â citations