scholarly journals DEFORMATION OF COASTAL PROFILE DURING DIFFERENT STORM PHASES

2018 ◽  
pp. 43
Author(s):  
Dmitry Korzinin ◽  
Margarita Shtremel
Keyword(s):  
Extreme Event ◽  
Wave Spectrum ◽  
Relative Duration ◽  
Experiment Data ◽  
Peak Period ◽  
Morphological Effect ◽  
Storm Waves ◽  
Sediment Transportation ◽  
Steep Waves ◽  
Coastal Profile

The aim of the work is to describe the mechanisms controlling the sediment transportation at different stages of the storm cycle including three main phases, namely development, stabilization and attenuation. The resulting morphological effect of the considered storm depends presumably not only on its strength, but also on the relative duration of the destructive and recovery phases. Two full-scale experiments conducted on the Bulgarian coast in 2016 and 2018 provided materials on the shore profile dynamics under conditions of storm waves. It proved that the profile deformations usually considered to be seasonal may happen in the course of a single extreme event of once a year frequency. Field experiment data analysis proved the concept that long mild waves move sediments onshore (cause accumulative profile) and short steep waves create erosional profile with sandbar. In studied case waves steeper than 0.02 create sandbars and milder than 0.02 – transport sandbars onshore. It was observed that in some cases accumulative phase corresponds to decrease of the peak period while mean period stays unchanged, which indicates narrowing of the wave spectrum.

scholarly journals Sea State Monitoring by Ship Motion Measurements Onboard a Research Ship in the Antarctic Waters

2021 ◽  
Vol 9 (1) ◽  
pp. 64
Author(s):  
Silvia Pennino ◽  
Antonio Angrisano ◽  
Vincenzo Della Corte ◽  
Giampaolo Ferraioli ◽  
Salvatore Gaglione ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Wave Spectrum ◽  
Weather Forecast ◽  
Ship Motion ◽  
State Monitoring ◽  
Sea State ◽  
Peak Period ◽  
Research Ship ◽  
Antarctic Waters ◽  
The Antarctic

A parametric wave spectrum resembling procedure is applied to detect the sea state parameters, namely the wave peak period and significant wave height, based on the measurement and analysis of the heave and pitch motions of a vessel in a seaway, recorded by a smartphone located onboard the ship. The measurement system makes it possible to determine the heave and pitch acceleration spectra of the reference ship in the encounter frequency domain and, subsequently, the absolute sea spectra once the ship motion transfer functions are provided. The measurements have been carried out onboard the research ship “Laura Bassi”, during the oceanographic campaign in the Antarctic Ocean carried out in January and February 2020. The resembled sea spectra are compared with the weather forecast data, provided by the global-WAM (GWAM) model, in order to validate the sea spectrum resembling procedure.

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.

Performance Comparison Between Linear and Nonlinear Controllers for a Dynamic Positioning System

2013 ◽  
Author(s):  
Helio Mitio Morishita ◽  
Lázaro Moratelli ◽  
Rodrigo Santos Martinez
Keyword(s):  
Wave Spectrum ◽  
Notch Filter ◽  
Performance Comparison ◽  
Nonlinear Observer ◽  
Positioning System ◽  
Peak Period ◽  
Dynamic Positioning System ◽  
Nonlinear Controllers ◽  
Backstepping Controller ◽  
And Control

This paper addresses some preliminary discussion concerning the performance of different dynamic observer-controller-based positioning system for a shuttle tanker by considering her operational condition changes. The observer-controller models are nonlinear passivity based observer and backstepping controller, Extended Kalman Filter and Proportional-Derivative like controller, and notch filter and Proportional-Integral-Derivative controller. The variation of the operational condition of the vessel is obtained by changing the vessel draft and the environmental condition, such as relative incidence of the current, waves and wind, and the peak period of the sea wave spectrum. The performance of the dynamics of the vessel is investigated through numerical simulation in which a saturation model for the actuators is included. Preliminary results have indicated that the nonlinear observer-backstepping controller is the easiest approach to select the observer and control parameter in the case of variation of the draft.

scholarly journals The impact of wave physics in the CMEMS-IBI ocean system Part A: Wave forcing validation

2019 ◽  
Author(s):  
Romain Rainaud ◽  
Lotfi Aouf ◽  
Alice Dalphinet ◽  
Marcos Garcia Sotillo ◽  
Enrique Alvarez-Fanjul ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Wave Spectrum ◽  
Circulation Model ◽  
Wave Model ◽  
Heat Fluxes ◽  
Wave System ◽  
Peak Period ◽  
Wave Forecast ◽  
High Frequency Waves ◽  
The Impact

Abstract. The Iberian Biscay Ireland (IBI) wave system has the challenge to improve wave forecast and the coupling with ocean circulation model dedicated to western european coast. The momentum and heat fluxes at the sea surface are strongly controlled by the waves and there is a need of using accurate sea state from wave model. This work describes the more recent version of the IBI wave system and highlight the performance of system in comparison with satellite altimeters and buoys wave data. The validation process has been performed for 1-year run of the wave model MFWAM with boundary conditions provided by the global wave system. The results show on the one hand a slightly improvement on significant wave height and peak period, and on the other hand a better surface stress for high wind conditions. This latter is a consequence of using a tail wave spectrum shaped as the Philipps wave spectrum for high frequency waves.

Optimum Power Capture of a New Wave Energy Converter in Irregular Waves

2009 ◽  
Author(s):  
George A. Aggidis ◽  
Mohammad T. Rahmati ◽  
Robert V. Chaplin ◽  
Andrew P. McCabe ◽  
Majid A. Bhinder ◽  
...  
Keyword(s):  
Control System ◽  
Wave Energy ◽  
Wave Spectrum ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Energy Converter ◽  
Mean Power ◽  
Peak Period ◽  
Point Absorber ◽  
Power Capture

This paper presents the optimum power capture of a new point-absorber wave energy converter, in irregular waves. A stepwise control system for the wave energy converter (WEC) is developed. The control system is used to efficiently extract power from irregular waves where amplitudes vary from wave to wave. The Bretschneider spectrum is used in the experiment and the device is ‘tuned’ to the peak period of the sea state. It is shown that this WEC has a reasonable capture width in irregular waves. However, the optimum mean power depends on the wave spectrum, the shape of the collector body, its freeboard and the device pivot depth.

Reliability Analysis of Pipelines During Laying, Considering Ultimate Strength Under Combined Loads

1999 ◽  
Vol 122 (1) ◽  
pp. 40-46 ◽  
Author(s):  
Ragnar T. Igland ◽  
Torgeir Moan
Keyword(s):  
Structural Reliability ◽  
Limit State ◽  
Wave Spectrum ◽  
Probability Of Failure ◽  
Ultimate Limit State ◽  
Minor Importance ◽  
Target Level ◽  
Peak Period ◽  
System Effect ◽  
Load Effect

Structural reliability methods are applied to establish a measure of safety for pipelines during laying, and especially to calibrate semi-probabilistic ultimate limit state criteria based on measures of uncertainty, method of reliability, and a given target level. Ultimate collapse of thick tubes under combined external pressure, tension, and bending loads are studied applying the finite element method. Nonlinear effects of large deformations, effects of initial ovality, residual stresses, strain-hardening, yield anisotropy, and loading paths were accounted for in the analysis. A set of interaction equations is proposed. Load effects in the pipelines during installation by the S-lay method are studied. The effects of uncertainties in yield stress, mass, stiffness of the stinger, response amplitude operator and peak period for the wave spectrum were accounted for in the analysis. The major factors affecting strain concentration due to concrete coating are taken into account. A combination of design point calculation and importance sampling procedure is used to calculate the probability of failure. The study includes calibration of partial safety factors for the design format selected. The most important random variable is the model uncertainty for bending capacity, while the uncertainty of the load effect has minor importance for the probability of failure. The system effect is taken into account considering the correlation along the pipeline. The probability of failure is referred both to the total laying period as well as a 3-h period demonstrating that the target level needs to be defined in view of the reference time period. [S0892-7219(00)01501-6]

scholarly journals OBSERVATION OF WAVE SPECTRUM UNDER TYPHOON CONDITION

2017 ◽  
pp. 10
Author(s):  
Woo Jeong Sim ◽  
Hyun-Doug Yoon ◽  
Weon Mu Jeong ◽  
Kyong-ho Ryu
Keyword(s):  
Korean Peninsula ◽  
Wave Spectrum ◽  
Spatial And Temporal Variation ◽  
Northwestern Pacific ◽  
Wave Direction ◽  
Peak Period ◽  
Translation Speed ◽  
Wave Measurements ◽  
Left And Right ◽  
Wave Conditions

The spatial and temporal variation of wave spectrum under typhoon SANBA, which was the 16th typhoon originating in the northwestern Pacific Ocean in 2012, was examined. The typhoon SANBA passed through the middle of Korean peninsula whereas most of typhoons passed the Straits of Korea (eastern side of Korean peninsula). This unique path of typhoon SANBA provided interesting features of wave conditions. It was believed that wave heights were larger in the right side of the typhoon path because typhoons translation speed and rotational wind field were in the same direction (i.e., dangerous semicircle). However, observational evidence of wave spectrum under typhoon was still rare because of the difficulty in measurement. In this study, wave spectrum analysis under extreme storm condition of typhoon SANBA is given for the left and right sides of the path, including the information of significant wave height, peak period, and dominant wave direction. Wave measurements were obtained by directional wave rider buoys installed at Yeosu and Namhyeongjedo in Korea. Yeosu and Namhyeongjedo are located in each of the left and right of the path of the typhoon SANBA. The measurements provided distinguished wave conditions in each side of navigable semicircle and dangerous semicircle of the typhoon. Therefore it is possible to observe the spatial differences of the wave spectrum across the path of the typhoon, as well as temporal changes of wave spectrum as the typhoon evolves.

scholarly journals VISIR-I: small vessels, least-time nautical routes using wave forecasts

2015 ◽  
Vol 8 (9) ◽  
pp. 7911-7981 ◽  
Author(s):  
G. Mannarini ◽  
N. Pinardi ◽  
G. Coppini ◽  
P. Oddo ◽  
A. Iafrati
Keyword(s):  
Optimization Algorithm ◽  
Wave Spectrum ◽  
Route Optimization ◽  
Optimal Route ◽  
Wave Direction ◽  
Parametric Roll ◽  
Peak Period ◽  
Speed Reduction ◽  
Small Vessels ◽  
Safety Constraints

Abstract. A new numerical model for the on-demand computation of optimal ship routes based on sea-state forecasts has been developed. The model, named VISIR (discoVerIng Safe and effIcient Routes) is designed to support decision-makers when planning a marine voyage. The first version of the system, VISIR-I, considers medium and small motor vessels with lengths of up to a few tens of meters and a displacement hull. The model is made up of three components: the route optimization algorithm, the mechanical model of the ship, and the environmental fields. The optimization algorithm is based on a graph-search method with time-dependent edge weights. The algorithm is also able to compute a voluntary ship speed reduction. The ship model accounts for calm water and added wave resistance by making use of just the principal particulars of the vessel as input parameters. The system also checks the optimal route for parametric roll, pure loss of stability, and surfriding/broaching-to hazard conditions. Significant wave height, wave spectrum peak period, and wave direction forecast fields are employed as an input. Examples of VISIR-I routes in the Mediterranean Sea are provided. The optimal route may be longer in terms of miles sailed and yet it is faster and safer than the geodetic route between the same departure and arrival locations. Route diversions result from the safety constraints and the fact that the algorithm takes into account the full temporal evolution and spatial variability of the environmental fields.

scholarly journals Correlation Analysis between Wave Parameters using Wave Data Observed in HeMOSU-1&2

2021 ◽  
Vol 33 (4) ◽  
pp. 139-147
Author(s):  
Uk-Jae Lee ◽  
Dong-Hui Ko ◽  
Hong-Yeon Cho ◽  
Nam-Sun Oh
Keyword(s):  
Correlation Analysis ◽  
Wave Height ◽  
Wave Train ◽  
Wave Spectrum ◽  
Correlation Coefficients ◽  
Spectral Energy ◽  
Analysis Method ◽  
Peak Period ◽  
Wave Parameters ◽  
Elevation Data

In this study, waves were defined using the water surface elevation data observed from the HeMOSU-1 and 2 marine meteorological observation towers installed on the west coast of Korea, and correlation analysis was performed between wave parameters. The wave height and wave period were determined using the wave-train analysis method and the wave spectrum analysis method, and the relationship between the wave parameters was calculated and compared with the previous study. In the relation between representative wave heights, most of the correlation coefficients between waves showed a difference of less than 0.1% in error rate compared to the previous study, and the maximum wave height showed a difference of up to 29%. In addition, as a result of the correlation analysis between the wave periods, the peak period was estimated to be abnormally large at rates of 2.5% and 1.3% in HeMOSU-1&2, respectively, due to the effect of the bimodal spectrum that occurs when the spectral energy density is small.

scholarly journals Joint Distribution of the Wave Crest and Its Associated Period for Nonlinear Random Waves of Finite Bandwidth

2020 ◽  
Vol 8 (9) ◽  
pp. 654 ◽  
Author(s):  
Yong Jun Cho
Keyword(s):  
Joint Distribution ◽  
Wave Spectrum ◽  
Wave Period ◽  
Wave Crest ◽  
Theoretical Treatment ◽  
Destructive Interference ◽  
Random Waves ◽  
Peak Period ◽  
Nonlinear Random Waves ◽  
Finite Bandwidth

The theoretical treatment of statistical properties relevant to nonlinear random waves of finite bandwidth, such as the joint distribution of wave crest and its associated wave period, is an overdue task hampered by the complicated form of the analytical model for sea surface elevation. In this study, we first derive the wave crest distribution based on the simplified version of the Longuet-Higgins’ wave model and proceed to derive the joint distribution of the wave crest and its associated period, and the conditional wave period distribution with a given wave crest, which are of great engineering value. It is shown that the bandwidth of the wave spectrum has a significant influence on the crest distribution, and the significant wave crest is getting larger in an increasing manner as nonlinearity is increased as expected. It also turns out that the positive correlation of wave crest height with its associated period is extended to more massive waves as nonlinearity is enhanced contrary to the general perception in the coastal engineering community that the wave crest is a statistically independent random process with wave period over large waves. The peak period decreases due to the destructive interference of second-order free harmonics.

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