PARAMETRIC ESTIMATION OF THE DIRECTIONAL WAVE SPECTRUM FROM SHIP MOTIONS

2021 ◽  
Vol 158 (A2) ◽  
Author(s):  
M A Hinostroza ◽  
C Guedes Soares
Keyword(s):  
A Priori ◽  
Wave Spectrum ◽  
Estimation Method ◽  
Parametric Estimation ◽  
Ship Motions ◽  
Offshore Platforms ◽  
Sea State ◽  
Directional Wave Spectrum ◽  
Directional Wave ◽  
Full Scale Tests

A parametric estimation of the directional wave spectrum based on ship motions is presented. The estimation of the sea- state parameters is essential to have an updated data base of the main characteristics of the sea-state, which are useful for several applications on open-sea such as offshore platforms installations and safe ship navigation. The sea-state parameters at a fixed position can be obtained using a traditional waverider buoy. The analogy between the ship and the buoy is clear thus, it is possible to obtain an estimate of the wave spectrum at the location of an advancing ship by processing its wave-induced responses similarly to the traditional waverider buoy. In the parametric procedure the estimated wave spectrum is a-priori assumed to be composed of one parameterized spectrum or by the summation of several parameterized spectra, e.g. the generalized JONSWAP spectrum. Genetic algorithms are applied to found the best estimation of wave parameters. The wave estimation method is validated against numerical simulations and full scale tests in a patrol ship.

Bayesian Estimation of Directional Wave-Spectrum Using Vessel Movements and Wave-Probes: Proposal and Preliminary Experimental Validation

2017 ◽  
Author(s):  
Felipe Lopes de Souza ◽  
Eduardo Aoun Tannuri ◽  
Pedro Cardozo de Mello ◽  
Guilherme Franzini ◽  
Jordi Mas-Soler ◽  
...  
Keyword(s):  
Linear Model ◽  
Wave Spectrum ◽  
Estimation Method ◽  
Scale Model ◽  
Spectral Energy ◽  
Peak Period ◽  
Directional Wave Spectrum ◽  
Wave Basin ◽  
Directional Wave ◽  
Probe Response

The measurement of the directional wave spectrum in oceans has been done by different approaches, mainly wave-buoys, satellite imagery and radar technologies; these methods, however, present some inherent drawbacks, e.g., difficult maintenance, low-resolution around areas of interest and high-cost. In order to overcome those problems, recent works in the area proposed a motion-based estimation procedure using the vessel, or the floating facility, as a wave sensor, what was called wave-buoy analogy. Despite of solving the issues, the solution is still incomplete, since it suffers from low estimation capabilities of the spectral energy below the cut-off period of the systems, around eight seconds, a frequency range that is responsible for the drift effects, that are critical for operation planning and dynamic positioning. This work studies the usage of wave-probes installed on the hull of a moored vessel to enhance the estimation capabilities of the motion-based strategy, using a high-order estimation method based on Bayesian statistics. The proposal is founded on the asymptotical response of the oceanic systems facing low period waves, which starts to behave like a wall, reflecting all the incoming energy, i.e., the worst the motion-based estimation is, the better the wave-elevation based estimation should be. Firstly, the measurements from the wave-probes are incorporated to the dynamic system of the vessel as new degrees-of-freedom, using a linear model extension, thus the Bayesian method can be expanded without additional reasoning. Secondly, the linear model hypothesis and the possible improvements are validated by experiments conducted in a wave-basin with a scale model of a moored FPSO-VLCC, concluding that the approach is able to improve not only the estimation of spectra with low peak period, but also the estimation in the entire range of expected spectra, mainly the significant height and the peak period properties. Lastly, some drawbacks are discussed, as the effect of the non-linear roll movement, which must be taken in account when calculating the wave-probe response; and the poor mean-direction estimation capability in some particular wave directions and low peak periods, in which even the vessel motions allied with the wave-probe response are not able to provide the proper direction discrimination.

Bayesian Estimation of Directional Wave-Spectrum Using Vessel Motions and Wave-Probes: Proposal and Preliminary Experimental Validation

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Felipe Lopes de Souza ◽  
Eduardo Aoun Tannuri ◽  
Pedro Cardozo de Mello ◽  
Guilherme Franzini ◽  
Jordi Mas-Soler ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Wave Spectrum ◽  
Estimation Method ◽  
Estimation Procedure ◽  
Scale Model ◽  
Spectral Energy ◽  
Peak Period ◽  
Directional Wave Spectrum ◽  
Wave Basin ◽  
Directional Wave

The measurement of the directional wave spectrum in oceans has been done by different approaches, mainly wave-buoys, satellite imagery and radar technologies; these methods, however, present some inherent drawbacks, e.g., difficult maintenance, low resolution around areas of interest and high cost. In order to overcome those problems, recent works proposed a motion-based estimation procedure using the vessel as a wave sensor; nevertheless, this strategy suffers from low-estimation capabilities of the spectral energy coming from periods lower than the cutoff period of the systems, which are important for the drift effect predictions. This work studies the usage of wave-probes installed on the hull of a moored vessel to enhance the estimation capabilities of the motion-based strategy, using a high-order estimation method based on Bayesian statistics. First, the measurements from the wave-probes are incorporated to the dynamic system of the vessel as new degrees-of-freedom (DOF); thus, the Bayesian method can be expanded without additional reasoning. Second, the proposal is validated by experiments conducted in a wave-basin with a scale model, concluding that the approach is able to improve not only the estimation of spectra with low peak period but also the estimation in the entire range of expected spectra. Finally, some drawbacks are discussed, as the effect of the nonlinear roll motion, which must be taken in account when calculating the wave-probe response; and the poor mean-direction estimation capability in some particular wave directions and low peak periods.

Sea State Estimation Based on Ship Motions Measurements and Data Fusion

2013 ◽  
Author(s):  
Céline Drouet ◽  
Nicolas Cellier ◽  
Jérémie Raymond ◽  
Denis Martigny
Keyword(s):  
Data Fusion ◽  
State Estimation ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Ship Motions ◽  
Sea State ◽  
Significant Wave ◽  
X Band

In-service monitoring can help to increase safety of ships especially regarding the fatigue assessment. For this purpose, it is compulsory to know the environmental conditions encountered: wind, but also the full directional wave spectrum. During the EU TULCS project, a full scale measurements campaign has been conducted onboard the CMA-CGM 13200 TEU container ship Rigoletto. She has been instrumented to measure deformation of the ship as well as the sea state encountered during its trip. This paper will focus on the sea state estimation. Three systems have been installed to estimate the sea state encountered by the Rigoletto: An X-band radar from Ocean Waves with WAMOS® system and two altimetric wave radars from RADAC®. Nevertheless, the measured significant wave height can be disturbed by several external elements like bow waves, sprays, sea surface ripples, etc… Furthermore, ship motions are also measured and can provide another estimation of the significant wave height using a specific algorithm developed by DCNS Research for the TULCS project. As all those estimations are inherently different, it is necessary to make a fusion of those data to provide a single estimation (“best estimate”) of the significant wave height. This paper will present the data fusion process developed for TULCS and show some first validation results.

HF Radar Directional Spectra Validation With Buoy and Model Data

2008 ◽  
Author(s):  
L. R. Wyatt ◽  
J. J. Green ◽  
A. Middleditch ◽  
J. C. Waters
Keyword(s):  
Wave Spectrum ◽  
Hf Radar ◽  
Model Data ◽  
Work In Progress ◽  
Directional Wave Spectrum ◽  
Directional Wave ◽  
Good Agreement

Examples of the measurement of the directional wave spectrum using HF radars are presented. These are compared with both buoy and model data and good agreement is demonstrated. Work in progress on partitioning these spectra for more detailed comparisons and for assimilation into models is discussed.

Dynamic Selection of Ship Responses for Estimation of On-Site Directional Wave Spectra

2012 ◽  
Author(s):  
Ingrid Marie Vincent Andersen ◽  
Gaute Storhaug
Keyword(s):  
Transfer Functions ◽  
Response Spectrum ◽  
Wave Spectrum ◽  
Selection Procedure ◽  
Selection Method ◽  
Parametric Modelling ◽  
Dynamic Selection ◽  
Directional Wave Spectrum ◽  
Reliability Method ◽  
Directional Wave

Knowledge of the wave environment in which a ship is operating is crucial for most on-board decision support systems. Previous research has shown that the directional wave spectrum can be estimated by the use of measured global ship responses and a set of transfer functions determined for the specific ship. The approach can either be based on parametric or Bayesian (non-parametric) modelling, and in both cases a set of three ship responses usually provides the best estimation. The optimal response combination of three responses at any time depends on the environmental conditions and the operation of the ship. Since measurements of more than three responses are usually available, a quick, dynamic selection procedure of the three signals best suited for the wave spectrum estimation procedure is essential. In the present paper the concept of a selection method based on a simple pre-estimate of the wave spectrum is suggested. The selection method needs to be robust for what reason a parameterised uni-directional, two-parameter wave spectrum is treated. The parameters included are the zero up-crossing period, the significant wave height and the main wave direction relative to the ship’s heading. The procedure basically seeks to minimise the difference between a set of spectral moments derived from a measured response spectrum and the corresponding response spectrum calculated from the parameterised wave spectrum and the transfer function for any given response. Subsequently, the three responses with the best overall agreement are selected for the actual estimation of the directional wave spectrum. The transfer functions for the ship responses can be determined using different computational methods such as striptheory, 3D panel codes, closed form expressions or model tests. The uncertainty associated with transfer functions depends on the computational method used, relative heading, frequency and type of response. This uncertainty is conceptually taken into account in the selection procedure using the First Order Reliability Method (FORM). However, specific assessment of the uncertainties has not been carried out, but is subject to later studies.

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