Statistical Analysis of a Set of Basin Waves

2011 ◽  
Author(s):  
Jule Scharnke ◽  
Janou Hennig
Keyword(s):  
Statistical Analysis ◽  
Wave Height ◽  
Water Depth ◽  
Water Waves ◽  
Rayleigh Distribution ◽  
Second Order ◽  
Distribution Functions ◽  
Wave Crest ◽  
Intermediate Water ◽  
Wave Measurements

In a recent paper the effect of variations in calibrated wave parameters on wave crest and height distributions was analyzed (OMAE2010-20304, [1]). Theoretical distribution functions were compared to wave measurements with a variation in water depth, wave seed (group spectrum) and location of measurement for the same initial power spectrum. The wave crest distribution of the shallow water waves exceeded both second-order and Rayleigh distribution. Whereas, in intermediate water depth the measured crests followed the second order distribution. The distributions of the measured waves showed that different wave seeds result in the same wave height and crest distributions. Measured wave heights were lower closer to the wave maker. In this paper the results of the continued statistical analysis of basin waves are presented with focus on wave steepness and their influence on wave height and wave crest distributions. Furthermore, the sampling variability of the presented cases is assessed.

scholarly journals Laboratory investigation of crest height statistics in intermediate water depths

2019 ◽  
Vol 475 (2229) ◽  
pp. 20190183 ◽  
Author(s):  
I. Karmpadakis ◽  
C. Swan ◽  
M. Christou
Keyword(s):  
Water Depth ◽  
Wave Breaking ◽  
Field Data ◽  
Full Range ◽  
Second Order ◽  
Intermediate Water ◽  
Sea State ◽  
Nonlinear Amplification ◽  
Effective Water ◽  
Water Depths

This paper concerns the statistical distribution of the crest heights associated with surface waves in intermediate water depths. The results of a new laboratory study are presented in which data generated in different experimental facilities are used to establish departures from commonly applied statistical distributions. Specifically, the effects of varying sea-state steepness, effective water depth and directional spread are investigated. Following an extensive validation of the experimental data, including direct comparisons to available field data, it is shown that the nonlinear amplification of crest heights above second-order theory observed in steep deep water sea states is equally appropriate to intermediate water depths. These nonlinear amplifications increase with the sea-state steepness and reduce with the directional spread. While the latter effect is undoubtedly important, the present data confirm that significant amplifications above second order (5–10%) are observed for realistic directional spreads. This is consistent with available field data. With further increases in the sea-state steepness, the dissipative effects of wave breaking act to reduce these nonlinear amplifications. While the competing mechanisms of nonlinear amplification and wave breaking are relevant to a full range of water depths, the relative importance of wave breaking increases as the effective water depth reduces.

Wave Measurements at Eastern Green Canyon During Hurricane Ike

2009 ◽  
Author(s):  
Oriol Rijken ◽  
Adam Bangs
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Repetitive Sequences ◽  
Wave Crest ◽  
Hurricane Ike ◽  
Wave Trough ◽  
Wave Measurements ◽  
Wave Event ◽  
Measurement Location ◽  
Insight Into

Wave measurements were obtained at an Eastern Green Canyon location during hurricane Ike in September 2009. The eye of the hurricane passed approximately 68 nautical miles to the South West of the measurement location. The significant wave height was above 30 ft for about 20 hours and above 40 ft for about 5.5 hours. The wave time series provide an insight into the wave field as the storm approaches and leaves the location. One of the interesting features observed was that there were repetitive sequences, where each sequence consisted of a period of increased wave energy followed by periods of reduced wave energy. Each sequence lasted approximately one hour. Measured wave crest, wave trough and wave height distributions are discussed. One unique wave event was observed. This event was characterized by a predictably-sized crest followed by a very deep trough.

Prediction of Wave Crest and Height Distributions and Wave Groups Using a Numerical Wave Tank

2010 ◽  
Author(s):  
Christian Schmittner ◽  
Sascha Kosleck ◽  
Janou Hennig
Keyword(s):  
Current Model ◽  
Power Spectra ◽  
Distribution Functions ◽  
Wave Crest ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Wave Measurements ◽  
Starting Point ◽  
Wave Basin ◽  
Numerical Wave

A major goal in current model test practice is the correct modeling of the environmental conditions, as they denote the starting point for all further hydrodynamic analyses. As a standard, wave power spectra are calibrated prior to the actual model tests whereas the corresponding wave group spectra follow from the arbitrarily chosen wave seeds and are not being predicted in advance. Wave crest and height distributions can be determined from the measured wave time traces at different reference locations in the basin but they are not calibrated purposely either. In this paper, a numerical wave tank based on a boundary element method is used to predict wave time traces measured in the wave basin. Resulting wave crest and height distributions are compared with theoretical distribution functions and wave measurements in MARIN’s Offshore Basin. Some thoughts on a possible application to the generation of “deterministic wave seeds” conclude the paper.

Nonlinear Crest Height Distribution in Three-Dimensional Ocean Waves

2008 ◽  
Author(s):  
Felice Arena ◽  
Alfredo Ascanelli
Keyword(s):  
Water Depth ◽  
Three Dimensional ◽  
Ocean Waves ◽  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
Order Model ◽  
Rayleigh Law ◽  
Wave Trough ◽  
Finite Water Depth

The interest and the studies on nonlinear waves are increased recently for their importance in the interaction with floating and fixed bodies. It is also well known that nonlinearities influence wave crest and wave trough distributions, both deviating from Rayleigh law. In this paper a theoretical crest distribution is obtained taking into account the extension of Boccotti’s Quasi Determinism theory, up to the second order for the case of three-dimensional waves, in finite water depth. To this purpose the Fedele & Arena [2005] distribution is generalized to three-dimensional waves on an arbitrary water depth. The comparison with Forristall second order model shows the theoretical confirmation of his conclusion: the crest distribution in deep water for long-crested and short crested waves are very close to each other; in shallow water the crest heights in three dimensional waves are greater than values given by long-crested model.

Improving Offshore Platforms Wave Measurements

2013 ◽  
Author(s):  
George Z. Forristall ◽  
Alexia Aubault
Keyword(s):  
Wave Height ◽  
Inverse Method ◽  
Wave Spectrum ◽  
Wave Crest ◽  
Offshore Platforms ◽  
Structural Members ◽  
Incoming Wave ◽  
Wave Measurements ◽  
Diffracted Waves ◽  
Wave Elevations

Offshore platforms are equipped with wave instrumentation at deck extremities to measure incoming wave elevations. When those instruments are close to large structural members they record the diffracted wave as well as the incident wave. This paper studies the effect of the diffracted wave on the measured wave height. First and second order diffracted wave elevations are computed for a model Tension Leg Platform (TLP) that was tested in the Offshore Basin of the Maritime Research Institute Netherlands (MARIN) offshore basin as part of the CresT Joint Industry Project (JIP). Their respective contributions to the wave spectrum are compared at locations near the structure. These calculations are useful for identifying the best locations for wave probes. The diffraction solution is used in forward calculations to compute the wave height and wave crest at locations under the deck from the undisturbed wave. These calculations can be used to set the air gap under the deck. Conversely, this paper introduces an inverse method to retrieve the undisturbed wave height and crest from the measured data by inverting the diffracted wave coefficients. The calculations are verified using measurements of undisturbed and diffracted waves under the TLP model. This work was sponsored by the Climatology and Simulation of Eddies (CASE) JIP.

Nonlinear Crest Height Distribution in Three-Dimensional Ocean Waves

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Felice Arena ◽  
Alfredo Ascanelli
Keyword(s):  
Water Depth ◽  
Three Dimensional ◽  
Ocean Waves ◽  
Order Theory ◽  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
Random Waves ◽  
Weakly Nonlinear ◽  
Wave Trough

The interest and studies on nonlinear waves are increased recently for their importance in the interaction with floating and fixed bodies. It is also well-known that nonlinearities influence wave crest and wave trough distributions, both deviating from the Rayleigh law. In this paper, a theoretical crest distribution is obtained, taking into account the extension of Boccotti’s quasideterminism theory (1982, “On Ocean Waves With High Crests,” Meccanica, 17, pp. 16–19), up to the second order for the case of three-dimensional waves in finite water depth. To this purpose, the Fedele and Arena (2005, “Weakly Nonlinear Statistics of High Random Waves,” Phys. Fluids, 17(026601), pp. 1–10) distribution is generalized to three-dimensional waves on an arbitrary water depth. The comparison with Forristall’s second order model (2000, “Wave Crest Distributions: Observations and Second-Order Theory,” J. Phys. Oceanogr., 30(8), pp. 1931–1943) shows the theoretical confirmation of his conclusion: The crest distribution in deep water for long-crested and short-crested waves are very close to each other; in shallow water the crest heights in three-dimensional waves are greater than values given by the long-crested model.

Wave Statistics in Nonlinear Sea States

2011 ◽  
Author(s):  
Mohamed Latheef ◽  
Chris Swan
Keyword(s):  
Empirical Distribution ◽  
Nonlinear Effects ◽  
Rayleigh Distribution ◽  
Second Order ◽  
Wave Crest ◽  
Statistical Distributions ◽  
Sea State ◽  
Wave Statistics ◽  
Wave Basin ◽  
Wave Heights

This paper concerns the statistical distribution of both wave crest elevations and wave heights in deep water. A new set of laboratory observations undertaken in a directional wave basin located in the Hydrodynamics laboratory in the Department of Civil and Environmental Engineering at Imperial College London is presented. The resulting data were analysed and compared to a number of commonly applied statistical distributions. In respect of the wave crest elevations the measured data is compared to both linear and second-order order distributions, whilst the wave heights were compared to the Rayleigh distribution, the Forristall (1978) [1] empirical distribution and the modified Glukhovskiy distribution ([2] and [3]). Taken as a whole, the data confirms that the directionality of the sea state is critically important in determining the statistical distributions. For example, in terms of the wave crest statistics effects beyond second-order are most pronounced in uni-directional seas. However, if the sea state is sufficiently steep, nonlinear effects arising at third order and above can also be significant in directionally spread seas. Important departures from Forristall’s empirical distribution for the wave heights are also identified. In particular, the data highlights the limiting effect of wave breaking in the most severe seas suggesting that many of the commonly applied design solutions may be conservative in terms of crest height and wave height predictions corresponding to a small (10−4) probability of exceedance.

Analysis and Applications of Second Order Models for Maximum Crest Height

2002 ◽  
Author(s):  
Harald E. Krogstad ◽  
Stephen F. Barstow
Keyword(s):  
Time Series ◽  
Wave Height ◽  
Water Depth ◽  
Second Order ◽  
Wave Steepness ◽  
Data Set ◽  
Wave Data ◽  
Definite Improvement ◽  
Crest Height

Expressions for the maximum crest height are reviewed and tested on data from five different sensors in the WACSIS data set. The overall agreement is good and the analysis supports that second order models give accurate expressions for the distribution of the maximum crest height for varying water depth and wave steepness. In the second part of the paper, the expressions are combined with the existing extreme crest and wave height framework and applied to sets of time series and long term wave data. It is concluded that the 2nd order models represent a definite improvement over earlier empirical parametrizations.

The Second Order Statistics of High Waves in Wind Sea and Swell

2007 ◽  
Author(s):  
Peter Tromans ◽  
Luc Vanderschuren ◽  
Kevin Ewans
Keyword(s):  
Wave Height ◽  
Probabilistic Method ◽  
Second Order ◽  
Wave Crest ◽  
Extreme Wave ◽  
Type Method ◽  
Second Order Statistics ◽  
Linear Effects ◽  
Wind Sea ◽  
Steep Waves

The statistics of extreme wave crest elevation and wave height have been calculated for realistic, directionally spread sea and swell using a probabilistic method tested and described previously. The non-linearity of steep waves is modelled to second order using Sharma and Dean kinematics and a response surface (reliability type) method is used to deduce the crest elevation or wave height corresponding to a given probability of exceedance. The effects of various combinations of sea and swell are evaluated. As expected, in all cases, non-linearity makes extreme crests higher than the corresponding linear ones. The non-linear effects on wave height are relatively small.

Effect of Variations in Calibrated Wave Parameters on Wave Crest and Height Distributions

2010 ◽  
Author(s):  
Janou Hennig ◽  
Jule Scharnke
Keyword(s):  
Power Spectra ◽  
Distribution Functions ◽  
Wave Crest ◽  
Wave Power ◽  
Wave Group ◽  
Wave Measurements ◽  
Initial Wave ◽  
Alternative Approach ◽  
Wave Basin ◽  
Wave Trains

In common model test practice, wave power spectra are calibrated prior to the actual model tests. The resulting wave crest and height distributions can be determined from the measured wave time traces at different reference location in the basin but they are not calibrated purposely. The corresponding wave group spectra follow from the wave power spectra together with arbitrarily chosen wave seeds applied to the wave trains. As an alternative approach, the seeds which give the highest and lowest wave group spectra can be applied in the tests. In this paper, results of wave measurements in MARIN’s Shallow Water Basin are presented which include a variation in water depth, wave seed (group spectrum) and location of measurement for the same initial wave power spectrum. The resulting wave crest and height distributions at different wave basin locations are analyzed and compared to theoretical distribution functions. A discussion of possible reasons for differences between theory and measurement concludes the investigation.

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