Simulation of Hurricane Seas in a Multidirectional Wave Basin

1991 ◽  
Vol 113 (3) ◽  
pp. 219-227 ◽  
Author(s):  
A. Cornett ◽  
M. D. Miles
Keyword(s):  
Ocean Waves ◽  
Entropy Method ◽  
Wave Spectra ◽  
Single Wave ◽  
Wave Condition ◽  
Wave Basin ◽  
Wide Range ◽  
Directional Wave ◽  
Wave Conditions ◽  
Multidirectional Wave

This paper describes the generation and verification of four realistic sea states in a multidirectional wave basin, each representing a different storm wave condition in the Gulf of Mexico. In all cases, the degree of wave spreading and the mean direction of wave propagation are strongly dependent on frequency. Two of these sea states represent generic design wave conditions typical of hurricanes and winter storms and are defined by JONSWAP wave spectra and parametric spreading functions. Two additional sea states, representing the specific wave activity during hurricanes Betsy and Carmen, are defined by tabulated hindcast estimates of the directional wave energy spectrum. The Maximum Entropy Method (MEM) of directional wave analysis paired with a single-wave probe/ bi-directional current meter sensor is found to be the most satisfactory method to measure multidirectional seas in a wave basin over a wide range of wave conditions. The accuracy of the wave generation and analysis process is verified using residual directional spectra and numerically synthesized signals to supplement those measured in the basin. Reasons for discrepancy between the measured and target directional wave spectra are explored. By attempting to reproduce such challenging sea states, much has been learned about the limitations of simulating real ocean waves in a multidirectional wave basin, and about techniques which can be used to minimize the associated distortions to the directional spectrum.

On the Estimation of Directional Wave Spectrum Based on Stationary Vessels 1st Order Motions: A New Set of Experimental Results

2008 ◽  
Author(s):  
Joa˜o V. Sparano ◽  
Eduardo A. Tannuri ◽  
Alexandre N. Simos ◽  
Vini´cius L. F. Matos
Keyword(s):  
Bayesian Inference ◽  
Wave Spectrum ◽  
Small Scale ◽  
Large Set ◽  
Wave Spectra ◽  
Inference Method ◽  
Peak Period ◽  
Wave Basin ◽  
Bayesian Inference Method ◽  
Directional Wave

The practicability of estimating directional wave spectra based on a vessel 1st order response has been recently addressed by several researchers. The interest is justified since on-board estimations would only require only a simple set of accelerometers and rate-gyros connected to an ordinary PC. The on-board wave inference based on 1st order motions is therefore an uncomplicated and inexpensive choice for wave estimation if compared to wave buoys and radar systems. The latest works in the field indicate that it is indeed possible to obtain accurate estimations and a Bayesian inference model seems to be the preferable method adopted for performing this task. Nevertheless, most of the previous analysis has been based exclusively on numerical simulations. At Polytechnic School, an extensive research program supported by Petrobras has been conducted since 2000, aiming to evaluate the possibility of estimating wave spectrum on-board offshore systems, like FPSO platforms. In this context, a series of small-scale tests has been performed at the LabOceano wave basin, comprising long and short crested seas. A possible candidate for on-board wave estimation has been recently studied: a crane barge (BGL) used for launching ducts offshore Brazil. The 1:48 model has been subjected to bow and quartering seas with different wave heights and periods and also different levels of directional spreading. A Bayesian inference method was adopted for evaluating the wave spectra based on the time-series of motions and the results were directly compared to the wave spectra measured in the basin by means of an array of wave probes. Very good estimations of the statistical parameters (significant wave height, peak period and mean wave direction) were obtained and, in most cases, even the directional spreading could be properly predicted. Inversion of the mean direction (180° shift), mentioned by some authors as a possible drawback of the Bayesian inference method, was not observed in any case. Sensitivity analysis on errors in the input parameters, such as the vessel inertial characteristics, has also been performed and attested that the method is robust enough to cope well with practical uncertainties. Overall results once again indicate a good performance of the inference method, providing an important additional validation supported by a large set of model tests.

scholarly journals Measuring Ocean Waves From Space: Objectives and Characteristics of the China-France Oceanography SATellite (CFOSAT)

2010 ◽  
Author(s):  
Danie`le Hauser ◽  
Ce´line Tison ◽  
Jean-Michel Lefe`vre ◽  
Juliette Lambin ◽  
Amiot Thierry ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Ocean Surface ◽  
Ocean Waves ◽  
Wave Spectra ◽  
Wind Vector ◽  
Satellite Mission ◽  
Surface Ocean ◽  
Related Science ◽  
Directional Wave ◽  
Ku Band

The Chinese and French Space Agencies are jointly preparing a satellite mission devoted to the monitoring of the ocean surface and related science and applications. This is the so-called “China France Oceanography SATellite” (CFOSAT), to be launched around 2013. This mission will provide simultaneous and collocated observations of wind at the ocean surface and spectral properties of surface ocean waves using two scatterometers, both in Ku-Band: SWIM for measurements of directional wave spectra and SCAT for wind vector measurements. The SWIM instrument will use a real aperture observation technique so as to avoid limitations encountered with SAR systems. This paper describes the main objectives and characteristics of the mission with a focus on the SWIM instrument designed and developed under French responsibility to measure directional spectra of ocean waves.

Model Tests With an FPSO in Design Environmental Conditions

2004 ◽  
Author(s):  
Jesper Skourup ◽  
Martin J. Sterndorff ◽  
Susan F. Smith ◽  
Xiaoming Cheng ◽  
R. V. Ahilan ◽  
...  
Keyword(s):  
Model Test ◽  
Environmental Conditions ◽  
Transfer Functions ◽  
Model Tests ◽  
Irregular Waves ◽  
Wind Condition ◽  
Test Programme ◽  
Wave Basin ◽  
Wide Range ◽  
Wave Conditions

An extensive model test programme has been carried out with a turret moored FPSO model in design environmental conditions. The model tests were carried out in the 3D offshore wave basin at DHI Water & Environment at a scale of 1:80. The objectives of the model tests were two-fold: 1. To determine quadratic transfer functions for the slow-drift forces. 2. To determine the turret moored FPSO response in design environmental conditions with wave spreading. The model tests were made with a wide range of monochromatic and bi-chromatic wave conditions and also with long- and short-crested irregular wave conditions. For the tests in design conditions the irregular waves were combined with the corresponding wind condition. The model (which was segmented into two parts) was equipped with instruments to measure forces in mooring lines and turret, 6 dof motions of the FPSO, bending moments on the FPSO hull and wave run-up on the FPSO model. The present paper describes the details of the experimental work and the measurements made in the tests. Comparisons between model test results themselves to demonstrate the effects of wave spreading on the responses and comparisons to numerical results are given. The model test programme is part of the REBASDO project, funded by the European Union, and involving companies and institutions from several European Countries. The overall objective with the REBASDO project is to develop met-ocean and hydrodynamic models, which will capture the significant features of directional wave effects on FPSO design so that relevant enhancements in the design process can be incorporated in the future.

A Preliminary Assessment of the Use of a Large Semi-Submersible Platform As a Motion-Based Wave Sensor

2017 ◽  
Author(s):  
J. Mas-Soler ◽  
Alexandre N. Simos ◽  
Pedro C. de Mello ◽  
Eduardo A. Tannuri ◽  
Felipe L. Souza
Keyword(s):  
Irregular Waves ◽  
Scale Model ◽  
Extreme Wave ◽  
Promising Alternative ◽  
Norwegian Sea ◽  
Experimental Campaign ◽  
Wave Basin ◽  
Extensive Test ◽  
Directional Wave ◽  
Wave Conditions

A well-known drawback of conventional wave monitoring systems, such as wave buoys, is that they experience a loss of accuracy in extreme wave conditions. Also, most of them require important initial investment and/or high maintenance costs. Over the last few years, directional wave inference obtained from the record of vessel motions is a technique that has significantly grown as complement to traditional methods. This article presents a feasibility study on the use of the motions of a semi-submersible platform for performing wave inference. Experiments were carried out at the USP wave basin (CH-TPN) using a 1:120 scale model of a large semi-submersible platform in operational condition and five different headings. In order to provide an extensive test matrix, the experimental campaign included a set of 32 different irregular waves (sea conditions) for each heading, selected from the scatter diagram of the Norwegian sea and covering many of the sea states of interest for this research. Moreover, each sea condition was obtained using the most appropriate type of energy spectrum (JONSWAP or Torsethaugen). Bayesian inference motion-based method was adapted for the semi-submersible platform by the proper adjustment of the hyper-parameters. The estimations obtained with the Bayesian wave inference method, using the semi-submersible recorded motions, were confronted with the directional wave spectra measured during the calibration process from an array of wave probes. The results attested that the method was able to capture all of the wave conditions tested during the experimental campaign with reasonable accuracy, even the more extreme cases. They suggest that the semisubmersible platform may indeed be a promising alternative for inferring severe sea conditions.

Shipboard Measurement of Ocean Waves

2011 ◽  
Author(s):  
Thomas C. Fu ◽  
Anne M. Fullerton ◽  
Erin E. Hackett ◽  
Craig Merrill
Keyword(s):  
Field Tests ◽  
Ocean Waves ◽  
Naval Research ◽  
Wave Spectra ◽  
Individual Measurement ◽  
Office Of Naval Research ◽  
Wave Radar ◽  
New Instrumentation ◽  
Directional Wave ◽  
Commercial Off The Shelf

Over the past several years a number of techniques have been utilized for the measurement of ocean waves from shipboard platforms. These systems have ranged from commercial off the shelf (COTS) navigation radar and Light Detection and Ranging (LIDAR) systems to specially developed in-house instrumentation systems. Most of these systems have been utilized to measure the directional wave spectra around the ship. More recently, the Naval Surface Warfare Center, Carderock Division (NSWCCD) and others have begun to utilize these techniques for shipboard measurement of individual ship generated waves as well as open ocean waves. NSWCCD has used a number of these methods on various Office of Naval Research (ONR) and Naval Sea Systems (NAVSEA) sponsored field tests. These field tests were performed on a variety of naval platforms over a range of sizes, including some fixed platforms, for various sea states. While each of these tests has had individual measurement goals and objectives, the series of tests has also provided an environment for testing and developing new instrumentation and exploring their capabilities. As a result of these efforts, instrumentation has grown in sophistication from qualitative video-based observations of the wave field around an underway vessel to laser and radar based imaging and ranging measurements of free surface dynamics. This work has led to higher fidelity data, as well as data that were previously unobtainable. In this paper we provide an overview of these systems and techniques and summarize the basic capabilities of each method by providing measurement examples/applications. These systems include a shipboard array of ultrasonic distance sensors for measuring directional wave spectra, a COTS wave radar system, and a COTS scanning LIDAR system. While not intending to be exhaustive, this paper seeks to highlight the insights gained from the recent applications of these techniques, as well as the difficulties and issues associated with shipboard measurements such as ship motion and logistical constraints.

scholarly journals Towards a three-dimensional model of wave–ice interaction in the marginal ice zone

2010 ◽  
Vol 662 ◽  
pp. 1-4 ◽  
Author(s):  
C. M. LINTON
Keyword(s):  
Three Dimensional ◽  
Ocean Waves ◽  
Wave Spectra ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
The Past ◽  
Marginal Ice Zone ◽  
Directional Wave ◽  
Ice Floes ◽  
Made In

Over the past forty or so years, considerable advances have been made in our understanding of the effects of ocean waves on sea ice, and vice versa, with observations, experiments and theory all playing their part. Recent years have seen the development of ever more sophisticated mathematical models designed to represent the physics more accurately and incorporate new features. What is lacking is an approach to three-dimensional scattering for ice floes that is both accurate and efficient enough to be used as a component in a theory designed to model the passage of directional wave spectra through the marginal ice zone. Bennetts & Williams (J. Fluid Mech., 2010, this issue, vol. 662, pp. 5–35) have brought together a number of solution techniques honed on simpler problems to provide just such a component.

scholarly journals Directional Surface Wave Spectra from Point Measurements of Height and Slope

2020 ◽  
Vol 37 (1) ◽  
pp. 67-83 ◽  
Author(s):  
William J. Plant ◽  
Mark A. Donelan
Keyword(s):  
Surface Wave ◽  
Spectral Estimation ◽  
Simulated Data ◽  
Processing Technique ◽  
Entropy Method ◽  
Wave Spectra ◽  
Double Peaks ◽  
Juan De Fuca ◽  
Directional Wave ◽  
Ocean Surface Wave

AbstractWe describe here a method for recovering directional ocean surface wave spectra obtained from height and slope measurements made over a small area, the iterative deconvolution method (IDM). We show that IDM is a more reliable method for estimating directional wave spectra than more common spectral estimation techniques by comparing it with the widely used maximum entropy method (MEM). IDM is based on the observation that pitch–roll buoys produce directional spectra that are the true spectra convolved with an angular windowing function and are therefore much broader than the true spectra. We test IDM against simulated data and find that it does a better job of retrieving the known input spectra than does MEM, which often produces false double peaks or incorrect angular widths. We compare IDM recoveries to spectra obtained using a nonstandard processing technique, the wavelet directional method (WDM) on data from a compact array of wave staffs on Lake Ontario. We find that IDM produces directional wave spectra very nearly identical to those obtained using WDM, verifying both techniques. Finally, we processed standard NDBC buoy directional spectra and showed that IDM recovers ocean wave spectra that narrow in the Strait of Juan de Fuca and that follow a changing wind in the expected manner. Neither of these phenomena are reliably obtained using MEM due to its tendency to produce false bimodal peaks and peaks that are too narrow.

scholarly journals The SPAIR method: Isolating incident and reflected directional wave spectra in multidirectional wave basins

2016 ◽  
Vol 114 ◽  
pp. 265-283 ◽  
Author(s):  
S. Draycott ◽  
T. Davey ◽  
D.M. Ingram ◽  
A. Day ◽  
L. Johanning
Keyword(s):  
Wave Spectra ◽  
Directional Wave ◽  
Multidirectional Wave

scholarly journals CALCULATION OF DIRECTIONAL WAVE SPECTRA BY THE MAXIMUM ENTROPY METHOD OF SPECTRAL ANALYSIS

1984 ◽  
Vol 1 (19) ◽  
pp. 33 ◽  
Author(s):  
MIchael J. Briggs
Keyword(s):  
Spectral Analysis ◽  
Maximum Entropy ◽  
Maximum Entropy Method ◽  
Adaptive Method ◽  
Entropy Method ◽  
Wave Spectra ◽  
Spectral Estimates ◽  
Directional Wave ◽  
Data Adaptive ◽  
Using Data

Two analysis techniques for calculating directional wave spectra from measured pressure and biaxial current components were intercompared using data from the 25 October 1980 Atlantic Remote Sensing Land Ocean Experiment (ARSLOE) storm. The two methods are the conventional Fast Fourier Transform (FFT) method and a Maximum Entropy Method (MEM). The MEM is a nonlinear data adaptive method of spectral analysis which is capable of generating higher resolution spectral estimates from shorter data records than conventional FFT methods. The MEM has shown good agreement with the frequency and directional wave spectra calculated using conventional methods.

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