bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of New Bow Shapes on FSICR Power Requirements
Authors: Matala Riikka , Suominen Mikko 
Published: September 2023

Abstract
In the Baltic Sea, merchant ships receive icebreaker assistance during the winter period based on their Ice Classes, which are granted based on the Finnish Swedish Ice Class Rules (FSICR). The FSICR set requirement for e.g. the ship minimum power demand to secure an adequate ice performance of ice-classed ships. The rules have been developed based on cumulative experiences on the winter navigation in the region with ships having traditional ice-going vessel design.
Recently, growing interest on sustainable transportation has led to new emission restrictions for merchant ships. This has generated new approaches for the ship bow design, especially for ships mainly operating in open water and only occasionally in ice. Some recently built ice-capable merchant ships have open-water-optimised bow shapes that substantially differ from traditional bow shapes of ice-going vessels. Instead of traditional low stem angles, the bow angle can be vertical or close to vertical.
Our recent research indicates that the current FSICR procedures may not evaluate the brash ice channel resistance of these modern bow shapes correctly. To secure the uniform ice class classification, this paper reflects the conclusions from our channel resistance research on the ice class rules power requirements and suggests improvements to current rules.
Drag Variation of a Coupled Rigid-Flexible System in Wind Tunnel Experiments
Authors: Zhao Yakun , Tian Xinliang , Zhang Huanyu , Sun Shuyue , Guo Xiaoxian , Peng Tao 
Published: September 2023

Abstract
A novel flow control method, by adding a closed flexible coating to a rigid body, has been proven a significant drag reduction in the two-dimensional flow in a soap film tunnel (Phys. Rev. Lett., vol. 125(3), 2020, pp. 034502). In the present study, we extend this method to three-dimensional rigid bluff body (a flat plate) flows through wind tunnel experiments. The Reynolds number (Re) based on the free-stream velocity (U∞) and the flat plate width is 24000. The length ratio of the flexible membrane (Lr) is in the range of 1.33∼3.23, and Lr = 1 represents a bare plate scenario. The effect of the length ratio on the drag of the rigid-flexible coupling system is discussed. It is found that the mean drag varies nonmonotonically to the length ratio. Benefiting from the closed flexible membrane, the coupled rigid-flexible system achieves a significant drag reduction in three-dimensional flows. The maximum drag reduction of approximately 19.1% is observed under specific conditions (Lr = 2.43). The flexible membrane self-adapts to a more streamlined shape and substantially changes the flow structures behind the plate. Controlled by the flexible membrane at Lr = 2.43, the flow separation is delayed, and the wake region changes to a narrow and shorter region, resulting in a significant drag reduction. The preliminary results obtained in the present study may shed some light on the closed flexible coating flow control method towards some real-life situations and potential applications.
Development of a Floating Dock Numerical Model and the Ballast Water Distribution Strategy
Authors: Zhang Jianan , Wen Xueliang , Ong Muk Chen 
Published: September 2023

Abstract
This study aims to develop a time-domain numerical model for simulating the dynamic response of a floating dock and propose a ballast water distribution strategy to help the dock reach a target draught with zero heel and trim. The floating dock is modelled as a six-degree-of-freedom (6-DOF) rigid body subjected to hydrostatic and hydrodynamic loads. A hydrostatic force model is built using Archimedes law and strip theory along the dock’s longitudinal direction. A hydrodynamic force model is made based on the effects of added mass and dynamic damping. The developed model is verified against the corresponding results obtained using HydroD, Autodesk Inventor and the theory of the dock’s free motions of heave, roll and pitch without damping. The ballast water distribution strategy provides the target water volumes in ballast tanks for a given draught and is created based on the equilibrium equations of draught, heel and trim. Vent pipes are installed in the ballast tanks to connect the air inside the tanks to the atmosphere outside the dock. Air cushions induced when the ballast water levels are higher than the bottoms of the vent pipes make the actual ballast water volumes not exceeding the target ballast water volumes at the maximum draught during ballasting operations. The relationship between the target ballast water volume and the height of the vent pipe bottom is investigated. In the case study, the freely floating processes of the dock with the ballast water distribution plans for different target draughts are simulated using the developed numerical model. The time histories of the dock’s draught, roll and pitch motions show that the proposed ballast water distribution strategy works successfully to make the dock reach its target draught with zero heel and trim. The maximum draught of the dock with the proper ballast water distribution and the corresponding vent pipe bottom heights in all ballast tanks are obtained.
A Novel Hybrid Transfer Learning Method for Bottom Hole Pressure Prediction
Authors: Zhang Rui , Song Xianzhi , Li Gensheng , Lv Zehao , Zhu Zhaopeng , Zhang Chengkai , Gong Chenxing 
Published: September 2023

Abstract
Accurate and efficient prediction of bottom hole pressure (BHP) is critical for safe drilling in complex formations. Recently, more and more studies have found that intelligent models have high accuracy in predicting BHP. However, most of the existing intelligent methods are limited to historical measurement, which is insufficient in processing new data. To overcome the problem of insufficient generalization ability of the model on new dataset, we propose a novel hybrid transfer learning approach to incrementally predict BHP in different well sections, combining long short-term memory (LSTM) and domain adversarial neural network (DANN). For deeper well sections, this method applies features learned from historical data in the upper well sections to boost the BHP prediction. LSTM is applied to extract temporal characteristics from the upper and deeper well sections. DANN tries to discover constant characteristics between the upper and deeper well sections. Next, LSTM-DANN model trained with data in the upper well sections can be used to support prediction of target BHP without degradation of accuracy due to data offset. Based on drilling data from the field, the performance of the proposed method is fully assessed. Results indicate that the hybrid transfer method can significantly improve the BHP prediction performance compared to models trained on data from different well sections. The mean absolute percentage error of the novel method reaches 0.15%, which is reduced by 30% compared with the original one. This study provides reference for accurate managed pressure drilling, and contributes to improve the transferability and generalization of intelligent models.
An Experimental Study on Vortex Induced Motion of a Submerged Cylindrical Buoy With a Short Tether Chain
Authors: Ledoux Thomas , Anne Florentin , Béguin Cédric , Gosselin Frédérick , Étienne Stéphane 
Published: September 2023

Abstract
Here we study experimentally the Vortex Induced Motion (VIM) of a cylindrical subsurface buoy tethered by a short chain. This system has 5 degrees of freedom (DOF), but can experience 3 DOF in translation (heave, surge and sway) and 3 DOF in rotation (yaw, pitch and roll). Previous studies focused on buoys with high ratio between tether line length and buoy diameter, which led to only 3 DOF motions (surge, sway and yaw). We put a reduced model buoy in the test section of a hydrodynamic loop. The mass ratio of the buoy was of 0.213, its slenderness ratio of 3.95, and the ratio between the tether line length and the diameter of the cylinder was of only 1.99, compared to around 15 in previous studies. Reduced velocity Ur ranging from 1.55 to 10.8 have been tested. The buoy was captured crosswise, and we got its surge and heave motions and the orientation of the buoy in terms of yaw, pitch and roll motions. Sway was not obtained in a satisfying way. Eventually, we found significant heave, surge, sway, yaw, pitch and roll motions above Ur ≈ 4. These motions were mostly harmonic, but with a irregular superimposed component, which was probably due to the turbulence of the flow. We did not observe any clear lock-in phenomenon, and the roll frequencies were always lower than Strouhal frequencies.
Acoustic Emission Based Damage Source Localization for Heterogeneous Structure of Wind Turbine Blades Using Long Short-Term Memory Neural Networks
Authors: Zhao Zhimin , Chen Nian-Zhong 
Published: September 2023

Abstract
The cost of operation and maintenance of wind farms has been increased significantly due to insufficient attention to structural damage of wind turbine blades. There is currently a great demand for structural health monitoring of wind turbine blades that could identify the location of damage source timely. The heterogeneity of the wind turbine blades poses a great challenge for damage source localization. A novel damage source localization method based on acoustic emission (AE) and long short-term memory neural networks is developed for heterogeneous structure of wind turbine blades in this paper. Two machine learning models based on long short-term memory (LSTM) neural networks, LSTM-Atten and LACNN, are pre-trained and utilized in a two-step approach to minimize the influence of propagation characteristics of AE signals. The first step is to identify the zone where the damage source is located and the second step is to determine the exact coordinates of the damage source. The time difference of arrival (TDOA) is used as the training feature. TDOA is calculated by the time of arrival (TOA), which is determined by the Akiake information criterion (AIC). Then, an example application of damage source localization for a “spar cap-trailing panel-shear web” heterogeneous structure of a wind turbine blade is performed to evaluate the performance of the method. A comprehensive comparison between the proposed method and the damage source localization method based on “L” shaped sensor cluster is carried out to verify the superiority of the proposed method. The results demonstrate the feasibility and robustness of the proposed damage source localization method for heterogeneous structure of wind turbine blades.
Coupled Hydrodynamic and Geotechnical Simulation of Floating Offshore Structures
Authors: Dyson Ashley P. , Tolooiyan Ali , Kefayati Gholamreza 
Published: September 2023

Abstract
Submerged and partially submerged moored structures subject to ocean conditions often require considerations regarding hydrodynamic loads impacting the behaviour of foundations and anchors attached to the seabed. Subsequent soil deformations can further affect the performance of anchored structures and, in extreme cases, result in anchor failure. This paper addresses simulation methods for assessing the response of offshore anchored structures under wave and current loading regimes with and without fluid-soil-structure interaction. Although coupled hydrodynamic-geotechnical simulation methods present a mechanism to analyse the full offshore fluid-soil-structure system, these methods are currently seldom implemented. In this research, numerical models combining rigid and deformable structural elements, fluids and soils in a single model are used to contrast the suitability and capabilities of various Finite Element (FE), Computational Fluid Dynamics (CFD) and Large Deformation Finite Element (LDFE) methods. Comparative results focus on applied mooring line loads, soil plasticity, and deformation characteristics to assess the behaviour and performance of anchors based on a range of ocean environmental loading conditions. An initial study of a four-point catenary moored floating box is presented for different numerical methods and compared with experimental scale model flume-test results. Further consideration is given to soil performance based on coupled hydrodynamic-geotechnical simulations of high-energy offshore conditions for a floating buoy and embedded pile in what is the first coupled Fluid-Structure-Seabed Interaction model of a moored floating system.
A Case Study on the Seabed Trenching Assessment and Anchor Design in Clay Based on the Hydrodynamic Calculation of the Floater
Authors: Rui Shengjie , Zhou Zefeng , Wang Baoxuan , Wang Hongyu , Zhang Haojie , Zhang Yaru 
Published: September 2023

Abstract
Seabed trenches near the anchors reduce anchor bearing capacity, and increase failure risks of the mooring system. However, the adverse influence is not well considered in the anchor design. This paper presents a case study on the anchor design in clay considering the seabed trenches based on the hydrodynamic calculation of the floater. The design procedure includes four steps. First, the hydrodynamic calculation of the floater coupled with mooring system is conducted under the 100-year return period to obtain the maximum mooring line tension and maximum cyclic displacement. Then, the 3-D potential trench profile is assessed by the mooring line-seabed dynamic model according to the fairlead movement. Third, the suction anchor is designed considering the calculated trench profile, and compared with that in the intact seabed. Last, the designed anchor is optimized to inhibit the potential trench development by adding a plate on the top of caisson. Some useful suggestions are concluded based on the case study results. This paper presents a systematic design from the hydrodynamic calculation of floater to the anchor design and optimization considering the potential seabed trenches.
Experimental Study on the Combination of Split Heave Point Absorber and TLP-Type Floating Turbine
Authors: Zhang Huidong , Wang Tong , Xu Cong , Shi Hongda 
Published: September 2023

Abstract
There are numerous wave energy resources in the ocean, and how to convert them efficiently is still a problem to be solved. Considering the waves in China sea area are characterized by short period and small height, one new model combining three split heave point absorbers with a tension leg platform (TLP) is proposed in this paper. Based on the physical model test, the hydrodynamic performance and wave energy capture efficiency of the split absorbers are investigated, and compared with those of the corresponding unsplit absorber. The experimental results reveal that the split absorber presents new hydrodynamic characteristics, and that the efficiency of the new wave energy capture device is greatly improved for small-period waves in the low sea state. However, the pitch motion of the platform is significantly increased in some cases with specific incident wave direction, which needs to be solved by further optimizing the TLP mooring system.
System Reliability Assessment of Jacket Structures Using Fault Tree Analysis Method
Authors: Renugadevi A. , Nallayarasu S. 
Published: September 2023

Abstract
Probabilistic methods have been used in offshore structures for individual components and whole structures based on the ultimate strength of the structural components. A new method for the assessment of system failure using individual member probability of failure using the fault tree method has been developed and demonstrated using a typical offshore platform jacket. The logical sequences of the component failure have been assessed using the importance of member for local strength, attached joint requirement and the load path required to continue the load distribution in case the other members fail. The proposed method has been used to verify the probability of failure for an existing jacket designed using the Allowable Stress Design (ASD) method and the corresponding Reserve Strength Ratio (RSR) has been computed. The critical failure path has been generated and the probability of failure of the members involved in the established failure paths and corresponding RSR is evaluated by First Order Reliability Method (FORM). The system reliability analysis is then used to identify the combined probability of failure of the individual failure paths, which in turn results in the dominant failure path that leads to the collapse of the structure. Finally, the system failure is assessed using simple bound formula.
Numerical Simulations of Three-Dimensional Scour Below Subsea Pipelines/Cables Under Steady Current Conditions
Authors: Zhang Bingchang , An Hongwei , Draper Scott , Jiang Hongyi , Cheng Liang 
Published: September 2023

Abstract
Scoured induced free span is one of the major engineering hazards for submarine pipelines/cables (P/Cs) in offshore oil and gas industry and offshore renewable energy industry. Due to the lack of knowledge about scour propagation along spanwise direction, conservative and costly stabilization methods are usually adopted for span mitigation. To address the concern related to free spans, great efforts have been made to establish the prediction models for scour propagation rate, most of the research is based on laboratory experiments to propose semi-theoretical equations. However, due to the limitation of present measuring techniques, it is hard to physically measure the gap flow and bed shear stress distribution under the P/C models. Thus, the physical mechanism for scour propagation is still not well understood. As a complement to laboratory experiments, numerical simulations can reproduce the whole flow fields around a P/C undergoing three-dimensional scour, which makes it a great tool to understand the interaction between flow and evolution of erodible seabed. Thus, in the present study, a scour model is used to simulate the three-dimensional scour below a P/C under steady current conditions. Two scour propagation stages are observed, the different mechanisms for the two stages are explained using the bed shear stress amplification factor. The flow fields around the scour hole are also analyzed. The present results, combined with the available laboratory experiments [1,3], will give a better understanding about the mechanism of 3-D scour.
Interdependency of Human Factors and Turbine State in Offshore Wind Farm Operations
Authors: Golestani Nima , Arzaghi Ehsan , Garaniya Vikram , Abbassi Rouzbeh 
Published: September 2023

Abstract
The effectiveness of operation and maintenance (O&M) activities significantly impacts the availability of offshore wind farms (OWFs) and the total cost of energy production. When a turbine is stopped to rectify a failure of any critical equipment or to perform preventive maintenance, there is a substantial cost for repair or replacement. Simultaneously, there is a production loss associated. Humans play a critical role in every stage of the O&M in the offshore wind industry. Human errors may jeopardize maintenance effectiveness, increase a system’s failure rate, or cause faster degradation, which may have substantial costs to the entire operation and cause pressure on the production to compensate for the downtime. This production pressure and repair cost pressure directly impact human performance, for instance, by shortening the time available to complete required maintenance activities. The cost pressure may also affect the industry’s operational budget, leading to hiring less trained and inexperienced maintenance crews or postponing training. These effects may lead to failure in different maintenance phases, including fault diagnosis and mistakes during repair tasks, further increasing human error probability (HEP). This paper proposes a causal loop diagram for the maintenance system of the offshore wind turbine, accounting for the interdependencies amongst human error likelihood, equipment health state, and associated uncertainties. By implementing various maintenance planning approaches, the dynamics of the system are modelled with more accuracy to identify the factor affecting the maintenance strategy and minimize human errors in the O&M of OWFs.
Algorithm to Develop Wave Scatter Table From Hindcast Data
Authors: Mangalathu Raj Samuel , Enshaei Hossein , Abdussamie Nagi 
Published: September 2023

Abstract
Any offshore structure requires engineering feasibility and fatigue study during the design and/or maintenance process. The studies mentioned above require an understanding of wave loading on the structure. Most wave loading studies consider wave scatter diagrams. However, the probability of wave occurrence depicted on wave scatter diagram change over region, season and period. Hence, the study based on any static wave diagram doesn’t reflect the probability of wave occurrence for a required region. Further, these waves scatter diagrams are not readily available for the specific local region of interest. Hence, in this study, an algorithm is developed to make a wave scatter diagram using hindcast Australian Meteorological data for a local region for a particular season or period of time. The data has 0.4 × 0.4 degrees spatial and one-hour temporal resolution and contain mean, wind and swell sea state; hence enables to make wave scatter diagram for mean, wind and swell sea for any offshore application. The advantage of the proposed hindcast wave scatter diagram includes flexibility and ease of customising wave scatter for any region, season or period of time compared to available sea area-specific wave scatter diagram. Also, the hindcast model is very well tested and updated regularly and hence wave scatter diagram is developed based on recently validated data. Since these data are free, making a more reliable and accurate wave scatter diagram is free. Additionally, in this study, the graphical comparison of the hindcast wave diagram with two additional sources for the North Atlantic wave and Australian water is provided for validation. The graphical comparison shows the differences and similarities of the wave scatter diagrams over different regions, seasons and periods.
Data Driven Identification of Ship Maneuvering Coefficients
Authors: Deogaonkar Vallabh Vinod , Jadhav Aditya Kailas , Ramachandran Krishnavelu , Somayajula Abhilash Sharma 
Published: September 2023

Abstract
Maneuvering models of a ship are quite complex and require accurate knowledge of the various hydrodynamic derivatives and coefficients to model the maneuvering trajectories undertaken by a ship accurately. Discerning these coefficients through practical tests in specialized facilities is expensive and time-consuming. Data-driven identification of the ship maneuvering coefficients using free-running model data is a possible alternative. In this study, the maneuvering motions of the KCS hull are simulated using the MMG model, which are then used as a starting point to identify an Abkowitz model for the vessel. The coefficients of the Abkowitz model are predicted without presuming any knowledge of the MMG model used to generate the data. Three different approaches — Least squares, LASSO optimization, and Support Vector Machines — are used to identify the hydrodynamic coefficients of the Abkowitz model. The identified coefficients are used to generate test trajectories not seen in training data and are compared with the MMG model to verify that the dynamics are accurately captured. The common issue of parameter drift occurring due to the problem being ill-posed is discussed, and sparsity-based solutions are suggested to overcome them.