Human Injury Probability During Water Entry of Free-Fall Lifeboats: Operational Criteria Based on Long-Term Simulations Using Hindcast Data

2014 ◽  
Author(s):  
Sébastien Fouques ◽  
Thomas Sauder ◽  
Svein-Arne Reinholdtsen ◽  
Esra van Dam ◽  
Jeroen Uittenbogaard
Keyword(s):  
Numerical Simulations ◽  
Wind Velocity ◽  
Wave Height ◽  
Significant Wave Height ◽  
Free Fall ◽  
Water Entry ◽  
Mooring Line ◽  
Significant Wave ◽  
Heading Control ◽  
Injury Probability

The paper addresses the safety of occupants in free-fall lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall lifeboats. The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull. Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.

scholarly journals The land–sea coastal border: a quantitative definition by considering the wind and wave conditions in a wave-dominated, micro-tidal environment

Ocean Science ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 113-126 ◽  
Author(s):  
Agustín Sánchez-Arcilla ◽  
Jue Lin-Ye ◽  
Manuel García-León ◽  
Vicente Gràcia ◽  
Elena Pallarès
Keyword(s):  
Distribution Function ◽  
Wind Velocity ◽  
Wave Height ◽  
Significant Wave Height ◽  
Gaussian Copula ◽  
Logistic Distribution ◽  
Normal Distribution Function ◽  
Significant Wave ◽  
Fringe Width ◽  
Quantitative Definition

Abstract. A quantitative definition for the land–sea (coastal) transitional area is proposed here for wave-driven areas, based on the variability and isotropy of met-ocean processes. Wind velocity and significant wave height fields are examined for geostatistical anisotropy along four cross-shore transects on the Catalan coast (north-western Mediterranean), illustrating a case of significant changes along the shelf. The variation in the geostatistical anisotropy as a function of distance from the coast and water depth has been analysed through heat maps and scatter plots. The results show how the anisotropy of wind velocity and significant wave height decrease towards the offshore region, suggesting an objective definition for the coastal fringe width. The more viable estimator turns out to be the distance at which the significant wave height anisotropy is equal to the 90th percentile of variance in the anisotropies within a 100 km distance from the coast. Such a definition, when applied to the Spanish Mediterranean coast, determines a fringe width of 2–4 km. Regarding the probabilistic characterization, the inverse of wind velocity anisotropy can be fitted to a log-normal distribution function, while the significant wave height anisotropy can be fitted to a log-logistic distribution function. The joint probability structure of the two anisotropies can be best described by a Gaussian copula, where the dependence parameter denotes a mild to moderate dependence between both anisotropies, reflecting a certain decoupling between wind velocity and significant wave height near the coast. This wind–wave dependence remains stronger in the central bay-like part of the study area, where the wave field is being more actively generated by the overlaying wind. Such a pattern controls the spatial variation in the coastal fringe width.

scholarly journals The Condition of Significant Wave Height and Wind Velocity in Makassar Strait during 2017

2019 ◽  
Vol 3 (1) ◽  
pp. 179-189
Author(s):  
Hanah Khoirunnisa ◽  
Shofia Karima
Keyword(s):  
Energy Spectrum ◽  
Wind Velocity ◽  
Wave Height ◽  
Significant Wave Height ◽  
Secondary Data ◽  
Weather Forecasts ◽  
Significant Wave ◽  
A Value ◽  
One Year ◽  
Height Data

This study aims to look at the conditions and characteristics of significant wave height and its relationship to wind velocity in the Makassar Strait in 2017. The data used in this study are bathymetry data from GEBCO with a resolution of 30 seconds, significant wave height data (Hs) with a resolution of 0.25 x 0.25 as well as wind velocity and direction with a resolution of 0.25 x 0.25 which are secondary data results from the European Center for Medium-Range Weather Forecasts (ECMWF) with a span of one year in 2017. The method used in this research is an analysis of the energy spectrum of significant wave height using Fast Fourier Transform. In addition, wind velocity and direction are processed by using GrADS software to see the visual conditions. Based on this study, it can be concluded that wind velocity is strongly associated with significant wave height values. This can be seen at each sample point in the Makassar Strait, where when the value of wind velocity is high, the value of significant wave height has the same conditions, and vice versa. The wind velocity value has a maximum value in the Makassar Strait during the east season with a value of more than 4.5 m/s. The highest energy spectrum occurs at point 3 in the Makassar Strait, which is 7303 m2 with a period of 6 months.

Shallow Water STL Mooring and Riser System

2009 ◽  
Author(s):  
Qinzheng Yang ◽  
Muthu Chezhian ◽  
Geir Olav Hovde
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Model Test ◽  
Water Depth ◽  
Significant Wave Height ◽  
Mooring Line ◽  
Test Results ◽  
Sea State ◽  
Significant Wave ◽  
The Impact

A shallow water disconnectable STL turret mooring and riser system has been developed for water depth between 30 and 50 m. This technology is based on APL’s disconnectable STL (Submerged Turret Loading) and STP (Submerged Turret Production) technologies which had been widely applied for water depth between 70 m to 2600 m for FPSOs and LNG offshore terminals. The advantage of disconnectable system is that the mooring and riser system can be designed to a preferred sea state. When the sea state is higher than design sea state (like hurricane), the vessel can be disconnected and sail away. The shallow water STL system consists of STL buoy, mooring lines, riser system and landing pad. The interface with vessel is the same as traditional STL system. The mooring and riser system are connected to the vessel through STL buoy and can be pulled into vessel by using ship winch. Unlike traditional STP and STL buoys, the shallow STL buoy has a net weight and will stay on the landing pad when disconnected from vessel. The landing pad is designed to support the impact load from STL buoy and supply enough friction for the STL buoy to stay in position during 100-year storm. The mooring system design has taken the advantage of directionality of weather when close to the shore by using different mooring line length in different directions. Further an innovative Hold-Back-Wave riser configuration has been developed for shallow water system. The riser configuration has a larger flexibility compared to traditional wave configuration and has proved to be feasible for significant wave height at least 7 m when connected to the vessel and 10+ m when disconnected from the vessel. Model test for the disconnectable shallow water turret mooring and riser system had been performed in MARINTEK, Trondheim with a LNG re-gasification vessel model at 30 m water depth. For connected system, significant wave height Hs = 6 m and 8 m has been tested. The mooring and riser system perform well, as predicted. For disconnected system (when the buoy sitting on the landing pad), significant wave height Hs = 10 m has been tested. The STL buoy is sitting on the landing pad without significant movement and the riser system performs well. SIMO program has been used to calibrate the model test results with numerical simulations. By adjusting surge, sway, yaw damping and 2nd order wave drift force, the calibrated SIMO model agrees well with model test results and can be used for similar development.

scholarly journals The land-sea coastal border: A quantitative definition

2018 ◽  
Author(s):  
Agustín Sánchez-Arcilla ◽  
Jue Lin-Ye ◽  
Manuel García-León ◽  
Vicente Gràcia ◽  
Elena Pallarès
Keyword(s):  
Distribution Function ◽  
Wind Velocity ◽  
Wave Height ◽  
Significant Wave Height ◽  
Gaussian Copula ◽  
Logistic Distribution ◽  
Robust Estimator ◽  
Significant Wave ◽  
Fringe Width ◽  
Quantitative Definition

Abstract. A quantitative definition for the land-sea (coastal) transitional area is here proposed, based on variability and isotropy of met-ocean processes.Wind velocity and significant wave height fields are examined for anisotropy along four perpendicular transects on the Catalan coast (northwestern Mediterranean) illustrating a case of significant changes along shelf. The variation of anisotropy as a function of distance from the coast and water depth has been analyzed through heatmaps and scatter plots. The results show how the anisotropy of wind velocity and significant wave height decrease towards the offshore, suggesting an objective definition for the coastal fringe width. The more robust estimator turns out to be the distance at which the significant wave height anisotropy is equal to the 90th quantile of variance within a 100 km distance from the coast. Such a definition, when applied to the Spanish Mediterranean coast, determines a fringe of width of 2–4 km. Regarding the probabilistic characterization, the inverse of wind velocity anisotropy can be fitted to a lognormal distribution function, while the significant wave height anisotropy can be fitted to a log-logistic distribution function. The joint probability structure of the two anisotropies can be best described by a Gaussian copula, where the dependence parameter denotes mild to moderate dependence between both anisotropies, reflecting a certain decoupling between wind velocity and significant wave height near the coast. This wind-wave dependence remains stronger in the central, bay-like part of the study area, where the wave field is being more actively generated by the overlaying wind. Such a pattern controls the spatial variation of the coastal fringe width.

On the Sensitivity of Passive Multistatic Radar Amplitude and Doppler Measurements to Significant Wave Height

2021 ◽  
pp. 1-5
Author(s):  
Jeffrey D. Ouellette ◽  
William T. Bounds ◽  
David J. Dowgiallo ◽  
Jakov V. Toporkov ◽  
Paul A. Hwang
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Significant Wave ◽  
Multistatic Radar

scholarly journals Estimation of Significant Wave Heights from ASCAT Scatterometer Data via Deep Learning Network

2021 ◽  
Vol 13 (2) ◽  
pp. 195
Author(s):  
He Wang ◽  
Jingsong Yang ◽  
Jianhua Zhu ◽  
Lin Ren ◽  
Yahao Liu ◽  
...  
Keyword(s):  
Deep Learning ◽  
Wave Height ◽  
Significant Wave Height ◽  
Incidence Angle ◽  
Ocean Waves ◽  
Global Scale ◽  
Learning Technology ◽  
Sea State ◽  
Significant Wave ◽  
Wave Heights

Sea state estimation from wide-swath and frequent-revisit scatterometers, which are providing ocean winds in the routine, is an attractive challenge. In this study, state-of-the-art deep learning technology is successfully adopted to develop an algorithm for deriving significant wave height from Advanced Scatterometer (ASCAT) aboard MetOp-A. By collocating three years (2016–2018) of ASCAT measurements and WaveWatch III sea state hindcasts at a global scale, huge amount data points (>8 million) were employed to train the multi-hidden-layer deep learning model, which has been established to map the inputs of thirteen sea state related ASCAT observables into the wave heights. The ASCAT significant wave height estimates were validated against hindcast dataset independent on training, showing good consistency in terms of root mean square error of 0.5 m under moderate sea condition (1.0–5.0 m). Additionally, reasonable agreement is also found between ASCAT derived wave heights and buoy observations from National Data Buoy Center for the proposed algorithm. Results are further discussed with respect to sea state maturity, radar incidence angle along with the limitations of the model. Our work demonstrates the capability of scatterometers for monitoring sea state, thus would advance the use of scatterometers, which were originally designed for winds, in studies of ocean waves.

scholarly journals Physical Modelling of the Effect on the Wave Field of the WaveCat Wave Energy Converter

2021 ◽  
Vol 9 (3) ◽  
pp. 309
Author(s):  
James Allen ◽  
Gregorio Iglesias ◽  
Deborah Greaves ◽  
Jon Miles
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Significant Wave Height ◽  
Wedge Angle ◽  
Wave Energy Converter ◽  
Wave Period ◽  
Surface Elevation ◽  
Energy Converter ◽  
Significant Wave ◽  
Model Scale

The WaveCat is a moored Wave Energy Converter design which uses wave overtopping discharge into a variable v-shaped hull, to generate electricity through low head turbines. Physical model tests of WaveCat WEC were carried out to determine the device reflection, transmission, absorption and capture coefficients based on selected wave conditions. The model scale was 1:30, with hulls of 3 m in length, 0.4 m in height and a freeboard of 0.2 m. Wave gauges monitored the surface elevation at discrete points around the experimental area, and level sensors and flowmeters recorded the amount of water captured and released by the model. Random waves of significant wave height between 0.03 m and 0.12 m and peak wave periods of 0.91 s to 2.37 s at model scale were tested. The wedge angle of the device was set to 60°. A reflection analysis was carried out using a revised three probe method and spectral analysis of the surface elevation to determine the incident, reflected and transmitted energy. The results show that the reflection coefficient is highest (0.79) at low significant wave height and low peak wave period, the transmission coefficient is highest (0.98) at low significant wave height and high peak wave period, and absorption coefficient is highest (0.78) when significant wave height is high and peak wave period is low. The model also shows the highest Capture Width Ratio (0.015) at wavelengths on the order of model length. The results have particular implications for wave energy conversion prediction potential using this design of device.

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