bluuebunny/crossref_metadata_2025_split huggingface dataset:
Generation of Controlled Irregular Wave Crest Statistics in a Numerical Wavetank Using HOS-NWT Solver
Authors: Canard Maxime , Ducrozet Guillaume , Bouscasse Benjamin 
Published: October 2022

Abstract
In order to assess the reliability of offshore structures facing extreme environmental conditions, sea keeping tests are performed at model scale in experimental or numerical wave tanks. The scope of the present paper is limited to the generation of wave condition for such tests. The vast majority of industrial practices follow a stochastic approach. For each design sea state, several realizations of long irregular wave sequences are generated. The qualification of the waves mainly relies on the analysis of the mean spectrum and the ensemble crest height distribution at the structure (target) location (Xt). However, the wave propagation from the wavemaker to Xt is affected by nonlinear mechanisms and dissipation phenomena which lead to uncontrolled variations of the quantities of interest. To face those issues, the most advanced wave generation procedures usually focus on the quality of the wave spectrum at Xt, iterating on the wave maker motions. Nevertheless, depending on Xt, the crest height statistics can significantly differ. For instance with steep and narrow-banded unidirectional sea states, the distributions obtained at target locations far from the wave maker (Xt &gt; 20λp, λp being the peak wavelength) enlighten a significant number of extreme events that are likely to strongly affect the response of the tested structure. On those grounds, the present study proposes a procedure that offers the possibility to reproduce those extreme statistics at locations closer to the wavemaker. The framework is limited to non breaking unidirectional waves. The procedure is numerically tested with the open-source nonlinear potential wave solver HOS-NWT. The study opens the way to an accurate control of the wave statistics at any location in a wave tank environment.
Estimating Joint Extremes of Significant Wave Height and Wind Speed for Tropical Cyclones
Authors: Sando Kosuke , Wada Ryota , Rohmer Jeremy , Lecacheux Sophie , Jonathan Philip 
Published: October 2022

Abstract
We provide a computationally-efficient scheme for the estimation of joint extremes of significant wave height (Hs) and wind speed (U) for tropical cyclones. The method incorporates the simple spatial extremes method (STM-E) of Wada et al., 2019 (for spatial extremes of each of Hs and U) and the conditional extremes model of Heffernan and Tawn, 2004 (for conditional modeling of Hs given extreme U and U given extreme Hs). We demonstrate the methodology in application to data generated from hindcast simulations and track shifting of past tropical cyclones in the neighborhood of Réunion island in the Indian Ocean. Following the STM-E approach, spatio-temporal maxima (STM) and exposures (E) of both Hs and U are extracted for each tropical cyclone event. Marginal extreme value distributions are then estimated independently for the STM samples of Hs and U, providing a means for marginal extrapolation to long return periods. Exposure data are used to estimate densities for the spatial distribution of Hs and U. The conditional extremes model is then used to characterize the joint structure of STM for Hs and U, conditional on one of those variables being extreme. The estimated joint return values for Hs and U are validated by comparison with the original data.
Prelude FLNG Free Weathervaning Heading Prediction and Uncertainties, Based on Machine Learning Model
Authors: Delivré Quentin , Rajaobelina Jery , Kang Mengchen , McConochie Jason , Drobyshevski Yuriy 
Published: October 2022

Abstract
Prelude Floating Liquefied Natural Gas (FLNG) facility is moored with an internal turret allowing it to free weathervane (FW), i.e. by leaving the unit to rotate according to environmental loads. During the engineering phase, the FLNG FW heading is estimated by the heading analysis (i.e. physics-based approach), and results are then used as input for other studies.
Therefore, a good estimation of the various environmental effects (waves, current and wind) and their contributions in terms of loads on the FLNG is critical to ensure a correct prediction of the FW heading. For the predominant contributions (wind and current), the force coefficients have been initially derived from wind tunnel tests during the engineering phase. However, Prelude FLNG being now installed on-site, measurements over recent years have shown slight discrepancies with the numerical predictions by the heading analysis.
Preliminary investigations were carried out and were aimed to improve some parameters of the numerical model. Nevertheless, it appeared that even with these improvements, discrepancies between numerical predictions and measurements were not always resolved. These discrepancies may have several origins, such as inadequacy of the numerical model, variability of the metocean data, uncertainties in measurements, etc.
In order to overcome the aforementioned uncertainties and unknowns, it has been decided to set-up a machine learning model (i.e. data-based approach). This machine learning model (RBF ANN - Radial Basis Function Artificial Neural Network) was trained with the recorded metocean data (input) and measured FLNG FW heading (output). Considering the amount of the measured data available (two years with a time step of 10 minutes), the necessity to optimize the model’s hyperparameters and the computer capability, a stepwise approach has been applied to ensure an accurate model can be built in a reasonable timeframe.
Finally, the machine learning model calculation shows a significant improvement in the prediction capability when compared to the measured FLNG FW heading. The resulting surrogate model is hence used to predict the FW heading and to derive the associated prediction intervals, which define the range of error with certain probability (for instance 95%). This paper describes the machine learning model used, the methodology and challenges of the approach, and discusses the results. The main conclusions and lessons learnt are also shared.
Simulation of a Ship Advancing in Pre-Sawn Ice
Authors: Huang Luofeng , Li Fang , Li Minghao 
Published: October 2022

Abstract
Pre-sawn ice test is the standard testing method to negate ice-breaking resistance from the whole resistance of a ship breaking level ice, which is of great importance for understanding ship-ice interactions and predicting various sea-ice loads on ships. This work has developed a computational model that can realistically simulate a ship advancing in a pre-sawn ice channel. The model applies Computational Fluid Dynamics to solve ship hydrodynamics, which is coupled with a novel particle-bonded Discrete Element Method to model pre-sawn ice pieces. Experiments were also conducted to validate the simulations. Upon validation, analyses were performed to investigate the ship-ice interaction. It was demonstrated that the pre-sawn ice resistance’s speed dependence has three regimes: for low ship speeds, the ice resistance slightly increases with decreased speed due to ice piling up; for middle ship speeds, the ship-ice interaction could remain similar and there is no distinctive change in the ice resistance; for high ship speeds, ice resistance evidently increases with increasing ship speed, which results from strong ship-ice collisions that cause ice pieces to move dramatically.
Importance of Numerical Analyses to Inform Laboratory Testing for Offshore Slope Stability Assessment
Authors: Carlton Brian , Suroor Hadi , Choi Young Jae , Hansen Ragnhild , Nadim Farrokh , Saqab Mudasar , Kaynia Amir M 
Published: October 2022

Abstract
An offshore pipeline will cross a series of steep rocky escarpments. Borehole samples show that there are thin layers of uncemented sand deposits at the head and middle of the largest escarpment. Bathymetry data also show evidence of past landslide activity, and the escarpments lie in a moderately seismic area. As a result, advanced, site-specific slope stability analyses were carried out to assess the failure potential of the slope in the event of project-specific design earthquakes. Analyses included deterministic and probabilistic static and pseudo-static slope stability analyses as well as dynamic time domain analyses. The initial results showed unacceptably low factors of safety against slope instability in the event of an earthquake based on empirically derived soil parameters. Consequently, additional advanced laboratory testing was performed to characterize better the dynamic properties and strength of the critical soil layer, and the pseudo-static and time domain analyses were repeated. Using the updated soil properties, the factor of safety and expected displacements during seismic shaking were reduced to satisfactory levels. The case history presented in this paper provides a clear example of the benefit of performing additional advanced laboratory testing to reduce uncertainty after numerical analyses have identified critical soil layers.
Procedure for Torsional-Vibration Calculations in Ice
Authors: Kistner Gunnar , Lal Kevin , Klüss Jörn , Kaeding Patrick 
Published: October 2022

Abstract
The safety of navigation at sea is closely connected to the reasonable operation of the marine power transmission system of a vessel. The propulsion unit inside a ship is considered as one of the most significant on-board systems that is mostly subjected to dynamic loading. The dynamic behaviour can cause various vibrations along the propulsion line that will substantially affect the propulsion shaft’s reliability and efficiency. One vital factor that can influence the shafting design is the shafting vibration behaviour, particularly the torsional vibration behaviour.
This paper focuses on developing a FEM based Torsional Vibration Calculation (TVC) method to identify and examine the vibratory stresses arising in the propulsion shaft line of a container vessel with a new design approach of TVC analysis in ice conditions. The aim is to model the ice-based response of the propulsion system for different loading conditions and obtain the results in time-domain. Therefore, it has to be a completely numerical based approach. The developed method gives the dynamic response of the shafting system subjected to torsional vibrations for different engine operation conditions that are based on the Finnish-Swedish Ice Class Rules (FSICR).
Numerical Investigations on Ultimate Strength of a Double Hull VLCC Under Combined Loads and Initial Imperfections
Authors: Lindemann Thomas , Okpeke Bright Ebikemefa , La Ferlita Alessandro , Mühmer Markus , Kaeding Patrick 
Published: October 2022

Abstract
Nonlinear finite element analyses are performed to determine the ultimate strength of a double hull VLCC under pure vertical, horizontal and biaxial bending. A parametric finite element model is developed and the influence of nonlinear material behavior, mesh size and model length on the hull girder ultimate strength is demonstrated exemplarily for hogging and sagging conditions. An appropriate parameter configuration with respect to numerical efforts and accuracy is used to perform static implicit analyses for horizontal bending and biaxial load cases. Convergence is reached by using the full Newton-Raphson scheme — an incremental iterative solution approach. The results are validated against the well-established Smith method. Due to welding, initial deflections and residual stresses are produced. For the proposed finite element model initial deflections of plating and stiffeners have been considered. Furthermore, the influence of welding residual stresses on the ultimate hull girder strength is demonstrated for the different load cases. Nonlinear finite element analyses are also performed to determine the residual strength of the damaged double hull VLCC under combined loads. Different symmetric grounding damages are implemented by removing structural components of the model. Expectedly, the results show that the ultimate strength of the structure decreases as the damage extent increases.
Design of a Prototype Renewably-Powered Offshore AUV Servicing Platform
Authors: Haji Maha N. , Tran Jimmy , Woodcock Luke , de Weck Olivier L. 
Published: October 2022

Abstract
This paper describes the design, fabrication, and field testing plans of a 1:2 Froude-scale prototype of a Platform for Expanding AUV exploRation to Longer ranges (PEARL). PEARL is an autonomous floating platform that utilizes renewable energy to recharge docked AUVs, while simultaneously uploading their mission data to a high-bandwidth low-Earth orbit satellite constellation for remote access and monitoring. The prototype has a diameter of 2.28 m, a draft of 1.04 m, and a mass of 147.42 kg. It is equipped with two 110 W solar panels, a 100 Ah battery, and two 205 N (46 lbf) electric trolling motors. A suite of environmental sensors are integrated on the platform constantly measuring air and water quantities to mimic the data transfer needs of an AUV. The prototype was field tested for six months in Deep Pond in Orleans, MA to test solar power generation, autonomous data logging, autonomous data transmission via the Iridium satellite network, and autonomous manuevering via MOOS-IvP.
A Strategy for the Reduction of Structural Weight of Composite Vessels
Authors: Gaiotti Marco , Vergassola Gianmarco , Pais Tatiana 
Published: October 2022

Abstract
Hull weight is a main structural concern in pleasure craft design, being in such project the maximum speed one of the most important contractual limits imposed by owner to shipyards. This is particularly true for composite structures, where the structural layouts and the beams’ dimensions may vary significantly among very similar projects, resulting in very different structural weights. Moreover, for this type of vessels, the structural weight is a significant percentage of the total displacement, and, consequently, reducing the structural components leads to important total weight reduction.
The present work aims to orient the preliminary design stage of composite pleasure yacht structural design towards an optimal configuration of the structural layout in terms of hull weight, within the current framework of rules provided by classification societies.
Metocean Database of the North Sea
Authors: Chu Kai , Breugem W. Alexander , Decrop Boudewijn 
Published: October 2022

Abstract
To fulfil the needs of using reliable metocean data, IMDC North Sea Metocean Database has been constructed based on a long-term hindcast simulation of in-house ICSM model for 26 years from 1995 to 2020. The North Sea Metocean Database provides 26-year time series of water level and velocity data with 10-minute interval at +15,000 specific sites including all the conventional measurement stations and all the present wind farm sites inside of the North Sea. Online statistics were performed during the 26-year hindcast simulation, providing various statistics on water level and velocities, serving as a reliable data source for offshore engineering projects in the North Sea.
Ice Pressure Measurements With TekScan Sensors - Behaviour, Calibration and Application Limits
Authors: Kubiczek Jan M. , Herrnring Hauke , Kellner Leon , Ruckert Phil , Ehlers Sören 
Published: October 2022

Abstract
Ships and offshore structures operating in ice-covered sea areas have to withstand ice loads. In particular, the distribution of ice pressure in the contact area is critical. The pressure distribution changes temporally and spatially and depends on the ice failure behaviour. Experimental measurements of ice pressures are possible with pressure mapping systems. A commonly used system in academia uses sensors manufactured by TekScan. The resulting measurements can be used to gain insight into ice failure behaviour, to establish design pressure patches, and to develop numerical models. However, various issues emerge when using these pressure measurement systems, e.g., equilibration and calibration, which result in measurement uncertainties. Hence, this paper summarize and discuss possible issues and gives recommendations to address them.
Generating a Digital Twin of the Glen Lyon FPSO
Authors: Bailey Jonathan , Bamford Richard J. , Das Suvabrata , Maroju Soma S. , Barker Robert J. 
Published: October 2022

Abstract
A Digital Twin has been developed for the Glen Lyon FPSO to maintain vessel integrity and ensure operation within the allowable design limits. At the core of this Digital Twin are two components: the Integrated Marine Monitoring System (IMMS) installed on the FPSO, and BMT DEEP, a cloud-based platform that stores, manages, integrates, post-processes and displays the vast data sets collected by the IMMS as well as other data sources. This paper focuses on harnessing the benefits of Digital Twin Technology, by bringing in data from all sources and enabling to synthesize and monitor the FPSO in near real-time from any remote location. This Digital Twin is designed to allow rapid query of the data by filtering with any time window in terms of hour, day, month, quarter, and year of data collection for the life of the asset.
Several sensors feed data to the Glen Lyon IMMS. The sensors include FPSO motion, stress response monitoring, and metocean monitoring. In addition to the FPSO based measurements, metocean data is also available from Met Office weather buoy K7, and wind measurements from the nearby Clair platform. A composite of the measured metocean parameters is generated from the quality control of the data. This quality-controlled data is visualized on DEEP as a time series, as well as comparisons with the basis of design data for the facility in terms of several statistical charts that form the metocean and structural dashboards. Some key insights and findings from these comparisons are presented.
Picking the Optimum Directional Drilling Technology (RSS vs PDM): A Machine Learning-Based Model
Authors: Nour Muhammad , Farahat Mohamed S. , Mahmoud Omar 
Published: October 2022

Abstract
Introducing rotary steerable systems (RSS) to the drilling industry has extended the directional drilling envelope to new horizons. Its role in better hole cleaning, faster rate of penetration (ROP), and less stuck pipe incidents is unquestionable. However, it comes with more economical challenges in terms of operating rates and Lost-in-Hole (LIH) charges. Many factors control the operator decision to run RSS rather than positive displacement mud motors (PDMs) — which have been the industry standards for decades — and vice versa. The intent of this paper is to introduce an advisor system based on machine learning that makes the selection process easier and more straightforward.
The system predicts total section time (including casing running) and cost for both RSS and PDM, the user may use either section time or cost criterion to assess which technology is preferred based on drilling campaign needs. The system input features include offset data of interval measured length, formations encountered, ROP, dogleg severities, operating cost of both technologies, rig operating cost, and many other variables. Input data to the system are divided into training and testing data for more reliable modeling. Many algorithms are tested to avoid over-fitting or under-fitting of training data.
The past performance of both RSS and PDM technologies in different formation plays a major role in determining the result. The result comes in both visual and tabulated forms to give the drilling engineer both quick impression and detailed insights about the selection process. As the result depends on formation-specific performance, it would change between wells depending on the formations thickness at these wells. This means that the result is not fixed per field and may vary considerably based on small changes of input.
The use of this advisor system should help in speeding up operator companies’ decisions and improving drilling performance and cost-effectiveness. This occurs through automating the whole process and making best use of offset drilling data thought implementation of machine learning algorithms.
On Rogue Waves Generated by Abrupt Depth Transitions
Authors: Li Zhenhao , Tang Tianning , Draycott Samuel , Li Yan , van den Bremer Ton , Adcock Thomas 
Published: October 2022

Abstract
Wave propagation over variable bathymetry is known as one of the possible mechanisms that can provoke rogue waves. In this paper, we use a fully nonlinear potential-flow solver, Ocean-Wave3D, to simulate the process of waves propagating over variable bathymetry and analyse the kinematics under the free surface near the top of the slope. To achieve this, we first evaluate the accuracy of the numerical results generated by Ocean-Wave3D. We carry out convergence tests to examine the influence of different parameters in OceanWave3D on the numerical results. Based on verification and validation tests, we evaluate the accuracy of OceanWave3D for problems with variable bathymetry comparing numerical and experimental results. We find that OceanWave3D is accurate enough to solve equations for problems with abrupt depth transitions and the agreement between experimental results and numerical results is good. Finally, we investigate the kinematics and we find that a slope can not only amplify crest amplitudes but also increase the wave kinematics near the top of the slope, which has obvious implications for loads on offshore structures.
MCMC Based Probabilistic Wave Spectrum Estimation Using Onboard Measurement Data
Authors: Park Myong-Jin , Kim Yooil 
Published: October 2022

Abstract
Probabilistic wave model is not only more suitable to describe uncertainties affecting structural reliability than deterministic wave model but also used to calculate probabilistic motion and structural response, which are able to facilitate the evaluation of structural reliability. In this regards, efforts have been made in this research to estimate the probabilistic wave spectrum using onboard measurement data. Firstly, Markov chain Monte Carlo simulation, which archives sampling from arbitrary probability density function of wave parameter as a random variable, was adopted as a probabilistic optimization method. Prior distribution and constraints of wave parameter were defined according to design wave model and previous wave observations. Previous wave observations consist of full-scale measurements obtained from 14,000 TEU container ship and MetOcean data of actual sea. Secondly, Numerical case study was performed for checking the validity of the proposed method. Data based on numerical simulations were generated by combining assumed wave spectrum and response amplitude operator, with some noise added. Finally, the proposed method was applied to full-scale measurements gathered from 14,000 TEU container ship, then, the calculated wave spectrum, motion and structural response were compared with full-scale measurements.