bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comprehensive Evaluation of Surface Ship Performance Based on Deep Reinforcement Learning
Authors: Ji Shengchen , Wang Hao , Luo Liang , Hao Zhailiu , Li Shengzhong 
Published: September 2023

Abstract
In order to evaluate the performance of surface ships accurately, this paper presents a comprehensive evaluation method based on deep reinforcement learning. The evaluation index system involves ship hydrodynamics, structural safety and stealth. And the initial index weights of each level are calculated by the hierarchical analysis method. Considering the difficulty of weight calculation caused by too many evaluation indicators, a weight correction model based on deep reinforcement learning is proposed. The model can quickly revise the index weight according to the subjective opinions of experts. For verifying the effectiveness, a comprehensive evaluation test of surface performance is conducted based on the published data of Type 5 surface ships. The findings demonstrate that deep reinforcement learning can produce intelligent index weight and assessment result corrections based on the knowledge of numerous experts.
When Do JONSWAP Spectra Lead to Soliton Gases in Deep Water Conditions?
Authors: Lee Yu-Chen , Brühl Markus , Wahls Sander 
Published: September 2023

Abstract
When a large number of solitons dominates the dynamics of a system, scientists describe this collective behaviour of solitons as a soliton gas. Soliton gases are currently the subject of intense practical and theoretical investigations. The existence of soliton gases has been confirmed in experiments, but is not clear what kind of sea states might lead to soliton gases. Therefore, in order to determine the wave parameters for sea states that lead to soliton gases, large numbers of surface wave elevations are generated by the well-known JOSNWAP model in this paper. Here, we only discuss soliton gases in deep water governed by the nonlinear Schrödinger (NLS) equation. The nonlinear Fourier transform (NFT) with vanishing boundary conditions is applied to the simulated ocean surface waves. The resulting nonlinear Fourier spectrum is used to calculate the energy of radiation waves and solitons. We investigate which JONSWAP parameters result in sea states that can be characterized as soliton gases, and find that a large Phillip’s parameter α, a large peak enhancement parameter γ and a short peak period Tp are important factors for soliton gas conditions. The results allow researchers to estimate how likely soliton gases are in deep waters. Furthermore, we find that the appearance of rogue waves is slightly increased in highly nonlinear sea states with soliton gas-like conditions.
Nonlinear Aero-Mooring Effects on Floating Offshore Wind Turbines Under Random Wind and Waves: Environmental Direction Effects
Authors: da Silva Leandro Souza Pinheiro , Y. Sergiienko Nataliia , S. Cazzolato Benjamin , Kiu Kwong , T. Gonçalves Rodolfo , Ding Boyin 
Published: September 2023

Abstract
Floating offshore wind turbines (FOWTs) have been extensively investigated to harvest the vast offshore wind potential at transitional to deepwater locations. Among the main FOWT components, mooring systems play an important role in the platform dynamics, being the primary source of restoring force in the surge and sway directions. For such degrees, the platform motion can be highly affected by turbulent wind loads due to the platform’s low natural frequencies. Catenary mooring systems are generally applied to FOWTs, which are characterised by nonlinear loads (asymmetrical). In such a system, when the mean aerodynamic thrust force acts on the platform, it leads to an offset position that modifies the mooring restoring force, changing the platform’s natural frequency. In this context, this work investigates the aero-mooring nonlinear effects on the platform dynamics under environmental conditions coming from different directions. The OC4 semi-submersible platform supporting the NREL 5-MW baseline offshore wind turbine with three catenary lines is chosen as a base case. The FOWT is subject to random loads from the wave and wind (temporal and spatial effects). Since efficient tools are favourable during the initial stages of development and in assessing an extensive range of environmental conditions, the numerical model is built using frequency domain modelling and statistical linearisation to estimate the nonlinear effects. The results show that the nonlinear mooring loads affect the natural frequency, making the platform more susceptible to stochastic wind loads when the environmental direction comes with an angle of 60° with respect to the platform.
Design of Mooring System for a 15MW Semi-Submersible, TaidaFloat, in Taiwan Strait
Authors: Chen Chi-Ang , Chen Kai-Hung , Igarashi Yuki , Chen Donghui , Ma Kai-Tung , Lai Zhao-Yu 
Published: September 2023

Abstract
Floating offshore wind turbine (FOWT) is one of the trending topics in the offshore industry. Taiwanese government agency, Bureau of Energy, recently announced a 100 MW floating offshore wind turbine demonstration project, which is planned to be installed in Taiwan Strait to have a jump start in the readiness of floating wind technologies. Compared with bottom-fixed offshore wind turbines, semi-submersible FOWT has many advantages, among different floater types, in economic efficiency as offshore wind farms go to deeper water. This paper summarizes the design of a mooring system and the anchor type selection for a concept floating system, TaidaFloat. TaidaFloat is a floating platform designed to support a 15 MW wind turbine in a water depth of around 70 meters. The mooring design follows the rules and guidelines of American Bureau of Shipping. 3 × 2 and 3 × 3 mooring patterns are investigated for feasibility of withstanding the winds, waves, and currents in Taiwan Strait. According to the rules, the mooring system must sustain an environmental load of a 50-year return period. The priority of the design is to minimize the cost and the footprint of the mooring system. OrcaFlex and ANSYS Discovery are used for the analyses. The results show that a 3 × 3 mooring pattern with an anchor distance (radius) of 10 times water depth is required to meet the design targets under extreme environmental conditions. Anchors of around 23tons are needed to withstand the mooring loads. Overall, in the current design, the mooring chain size and anchor weight turned out to be relatively large as compared to other designs. Reducing the cost of the mooring and anchor systems remains to be a challenge in future work.
Temporal Discretization Investigation of the Unsteady Loading on an Infinitely Long Cylinder in High Reynolds Numbers Using DES
Authors: de Oliveira Marielle , da Silva Leandro S. P. , Saltara Fabio , Carmo Bruno S. , Gonçalves Rodolfo T. 
Published: September 2023

Abstract
The flow around circular cylinders has been extensively investigated over the past decades, both numerically and experimentally, due to its importance in offshore applications. However, the phenomenon of vortex shedding remains not completely understood at supercritical and postcritical regimes due to difficulties in representing the nature of separated flows past bluff bodies at such high Reynolds numbers. This work thus presents a numerical investigation of the flow field and its forces on a circular cylinder at supercritical and postcritical Reynolds regimes using Computational Fluid Dynamics (CFD), more specifically the Finite Volume Method (FVM) implemented in the Open-FOAM software. The flow past a fixed circular cylinder of aspect ratio equal to 2 and periodic boundary conditions at its ends is assessed for Re = 1 × 106, 3.6 × 106, and 1 × 107. We employed the hybrid detached eddy simulation (DES) along with Menter’s k-ω SST model as a turbulence closure model, and analyzed the loads acting on the cylinder and other flow features, such as Strouhal frequency, at each regime. A temporal discretization analysis was carried out for the Reynolds regime of 107, whereby three different Courant-Friedrichs-Lewy (CFL) numbers were tested, namely CFL equal to 0.25, 0.5, and 1. The capability of each CFD simulation in capturing the physics of the system is assessed by comparing it with results found in the literature for similar cases, in terms of lift and drag coefficients, and Strouhal frequency. The numerical investigations presented satisfactory results for all cases; however, a considerable increase in the computational demand was noticed for higher Reynolds numbers and lower CFL numbers, CFL = 0.25 and 0.5.
Integrated Optimization of Hybrid Steam-Solvent Injection in Post-CHOPS Reservoirs Under Uncertainty
Authors: Hou Senhan , Yang Shikai , Jiang Liwu , Yang Daoyong 
Published: September 2023

Abstract
In this paper, an integrated algorithm is proposed to optimize the hybrid steam-solvent injection-production schemes for post-CHOPS reservoirs under uncertainty. First of all, the newly developed pressure-gradient-based (PGB) sand failure criterion is employed to generate dendritic (or fractal-like) and regional wormhole networks, based on which the net present value (NPV) is defined and used as the objective function. A hybrid optimization technique based on the genetic algorithm (GA) is then integrated with the orthogonal array (OA) and Tabu search to maximize the objective function by rationalizing the injection and production parameters and simultaneously retarding the displacement front to extend the reservoir life under uncertainty. In a given CHOPS well, not only can the proposed method be used to determine the overall morphology of the wormhole network, including intensity and coverage, but also design, evaluate, and optimize performance of any potential EOR processes in a post-CHOPS reservoir within a unified, efficient, and accurate framework.
Numerical Investigation of Air-Blast Performance of Cross-Filled Honeycomb Sandwich Panel
Authors: Patel Murlidhar , Patel Shivdayal , Ahmad Suhail , Soares Carlos Guedes 
Published: September 2023

Abstract
Today’s biggest terrorist attack is the blast. The public and property are suffering significant harm as a result of the explosion. However, the modern period is looking for a structure that is blast-proof to safeguard people and pricey properties from explosions. Sandwich panels have an excellent capacity to absorb energy under blast as well as impact loads. As a result, a unique blast-proof sandwich panel was created in this study by using a cross-filled reinforced square honeycomb core. The investigation of blast mitigation performance through experiment is very dangerous, costly, and environmentally polluting. However, to overcome these issues, by using ABAQUS/Explicit, the blast mitigation performance of the modelled honeycomb sandwich panels was examined for a constant stand-off distance (SoD) of 100 mm at 1 kg to 3 kg TNT air-blast loadings. This study was carried out after the mesh convergence and validation studies. The new sandwich panel design’s blast resistance was examined by measuring the face deflection and energy absorption capabilities under air-blast loadings. A sandwich panel made of a reinforced square honeycomb core significantly increases blast resistance by reducing face deflection and increasing energy absorption contribution by the core. Compared to the sandwich panel with a square honeycomb core and a cross honeycomb core, the novel designed sandwich panel exhibits greater core energy absorption contribution, a smaller front face, and smaller rear face deflection at all applied air-blast pressures. Therefore, the sandwich made with a cross-filled square honeycomb core has the greatest blast-proof properties. The newly created sandwich panel may be used for several armoured vehicle components to protect soldiers.
A New Method for the Design and Coupled Analysis of Floating Offshore Wind Turbines
Authors: Veen Daniel , Pahos Spiro J. , Meng Shawn , Dillenburg Simon 
Published: September 2023

Abstract
Global power generation from floating offshore wind turbines is expected to grow from 132 MW in 2022 to 289 GW by 2035. During the design phase these floating systems will require advanced numerical analysis tools to ensure strucutural integrity and reliability.
A new method for the hydrodynamic analysis of these structures is presented. The long standing offshore operations simulation software MOSES has been enhanced with the addition of the AeroDyn aeroelastic wind turbine solver from OpenFAST. This coupled analysis tool is designed to compute the motions and loads on the floating system. An added benefit of using MOSES is that these loads can be readily mapped on to a structural model for assessing code compliance.
In this paper the MOSES-AeroDyn solver has been validated against published numerical and model test data of the OC3-Hywind system in regular waves. The coupled MOSES-AeroDyn results were found to be in good agreement with both the experimental and numerical data.
Numerical Study on the Deceleration Effect of Impact Velocity of Tsunami Drifting Objects in Front of Structures
Authors: Takekawa Mebae , Aida Yasuhiro , Nakazawa Hibiki , Sasaki Ami , Ikoma Tomoki , Masuda Koichi 
Published: September 2023

Abstract
Several formulas have already been proposed to predict the impact force of flotsam caused by tsunamis. All of these equations require the impact velocity of the flotsam to calculate the impact force, and many studies have been conducted on the drifting velocity of the flotsam. Although CFD calculation methods have been used for such as problems, detail of behaviors of the flotsam colliding with a structure is still unclear. However, it has been known that the drifting velocity in front of the structure decreases very much. In order to improve accuracy of the impact force, the deceleration and the behaviors should be clarified.
A purpose of this study is to investigate effects of the deceleration of a drifting object as flotsam in front of the structure. In this study, the MPS method was used to predict behaviors of the object in tsunamis. Then, the study estimated run-up height in front of the wall of the structure. in addition, the effects of the ratio between length of the drifting object and width of the wall and tsunami incidence angles were varied.
Numerical simulation results showed that the velocity before collision decreased when the tsunami incidence angle is 0 degrees,, the velocity decreased very much rather than 0 degrees cases when the width of the structure is wider than it of the object, and when the tsunami incidence angle is 45 degrees.
Time-Series Forecasting for Health Monitoring of Marine and Offshore Renewable Energy Systems
Authors: Abaei Mohammad Mahdi , BahooToroody Ahmad , Arzaghi Ehsan , Abbassi Rouzbeh , Inkinen Tommi , Garaniya Vikram 
Published: September 2023

Abstract
Marine and Offshore renewable structures are widely being developed across the globe, and specifically in Australia, under controlled conditions with little focus on having advanced health monitoring systems, optimization of the structures design and operation to undertake complex operations. Considering a data-driven approach to health management is an essential part of the future offshore renewable energy industries. It allows the detection of critical faults and assists in estimating the remaining useful lifetime (RUL) facilitating more reliable offshore renewable structures. Despite the advantage of machine learning techniques in asset health condition monitoring, few studies have considered the integration of such prognostics into maintenance planning for remotely operated offshore facilities. This paper proposes a model to help the marine and offshore industry in real-time maintenance planning. The model will consider the imperfect RUL prognostics incorporating higher degrees of uncertainty involved with remotely operating systems in offshore environments. A Bayesian Meta-Model is developed for time series change point (CP) detection of multiple anomalies in a random process. The proposed methodology will be useful in incipient failure detection and maintenance planning of complex systems operating in harsh and highly random marine environments.
Computational Fluid Dynamic Modelling of Vortex-Induced Motion of Wind Turbine Monopile Foundation During Installation
Authors: Liu Shengnan , Moen Petter , Fiore Fabrizio 
Published: September 2023

Abstract
The vortex-induced-motion (VIM) of a hollow monopile is investigated using a three-dimensional two-phase Computational Fluid Dynamic (CFD) model in ANSYS CFX. The turbulence effects are modelled using the k-omega SST turbulence model. Both air and water phases are included in the numerical model to consider the variation of the buoyancy due to the rigid body motion. Dynamic mesh techniques with six-degree-of-freedom (DOF) rigid body are used to capture the motion of the monopile. The mesh and time step convergence studies are conducted first, and the converged numerical set-up is used for the other cases. The numerical model is validated against the model test measurements for VIM of a scaled monopile foundation by Seaway7 to show the applicability of the present numerical model for the VIM prediction in subcritical flow regions. The characteristics of the inline and cross-flow motions, hydrodynamic coefficients and flow fields are discussed.
Frequency Domain Dynamic Response Analysis of Three Parallel Ships in a Twin Marine Lifter System
Authors: Zhang Huan , Teng Yanjun , Fan Shida , Wang Yuhan , Wang Chao , Yin Yan 
Published: September 2023

Abstract
Many aging large offshore platforms are facing the problem of decommissioning and dismantling. In this paper, a method of removing the upper module of the platform by using a twin marine lifter system (TML) is proposed. In order to study the reliability of this method, added mass, damping, wave force and RAO of the three-ship system are analyzed, and the influence of three-ship interaction and water depth on the hydrodynamic parameters of the three-ship system are investigated. The hydrodynamic analysis is carried out under different environmental conditions, and the variation characteristics of the hydrodynamic parameters of the ship in the three-ship system are obtained. The results show that when three ships are alongside, the interaction of the three ships will have a significant effect on the hydrodynamic parameters, and the interaction of the three-ship system on the hydrodynamic parameters is mainly in the wave frequency range; The system is sensitive to changes in sea state conditions, and the motion response is maximum when the wave angle is 90° and minimum at 0°, but there is still some lateral motion. In practical operation, it is necessary to avoid the wave frequency and the direction of environmental load when the motion response is large, and consider the relevant effects in mooring and dynamic positioning.
A Numerical Assessment of Mooring System Modelling Uncertainties in Hydrodynamic Model Testing of Floating Wind Turbines
Authors: Berthelsen Petter Andreas , Thys Maxime , Bachynski-Polić Erin 
Published: September 2023

Abstract
This paper presents a general uncertainty assessment in hydrodynamic testing of a floating wind turbine. A general uncertainty analysis is often carried out when the goal is to assess the sensitivity of the results to uncertainties in the input variables, regardless of whether the uncertainty is of systematic or random nature. The analyses are based on the 12MW INO WINDMOOR semisubmersible floating wind turbine. The assessment is carried out as a numerical study of the WINDMOOR hydrodynamic experiment [1]. A global simulation model of the experimental setup is established in the simulation framework SIMA. The propagation of uncertainty is assessed using two different approaches: The classical Taylor Series Method (TSM) and the Monte Carlo Method (MCM). Specifically, the uncertainties in the mooring system and their effects on the mooring line tension and platform responses are investigated. The assessment is performed for a range of standard uncertainties in the input variables, and the results from the two methods of assessing the uncertainty are compared.
The General Nonlinear Stiffness Matrix of Taut-Leg Platforms, TLPs and Suspension Systems of Cable-Connected Floater-Keel Platforms
Authors: Esber Ghaith , Kosleck Sascha 
Published: September 2023

Abstract
The static and dynamic behavior of taut-leg and tension leg platforms (TLPs) is highly characterized by the stiffness properties of their mooring systems. That also applies to the innovative offshore floating wind turbine platforms that are composed of a floater connected to a keel only via suspension cables. Several works have tried to derive the nonlinear stiffness matrix of such systems. Yet, the results are only partially similar. In this study, a general approach is developed for deriving the nonlinear tangent stiffness matrix of a floating platform moored with a single taut line. The stiffness matrix is derived using the virtual work principle as a function of the platform’s general displacement. The derived matrix is analytically verified. Furthermore, the stiffness matrix of a rectangular taut-leg platform and a rectangular TLP is constructed and their initial forms are computed and compared to previous works. In addition, the innovative floating platform concept CBTS (cable-based truss spar) is introduced and the previously presented methodology is adopted to derive the general nonlinear stiffness matrix of its suspension system. The floater initial pitch stiffness of the CBTS platform is further investigated at different initial positions of the platform.
Non-Linear Hydrodynamic Forces on Fixed Axi-Symmetric Bodies in Incident Waves
Authors: Tan Bryan , Orszaghova Jana , Kurniawan Adi , Wolgamot Hugh , Hals Todalshaug Jørgen 
Published: September 2023

Abstract
Hydrodynamic forces induced by surface gravity waves on a wave energy converter directly influence its motion and power capture. Characterisation of these forces is therefore critical to optimising the hydrodynamic design of these devices. This study experimentally investigates linear and higher harmonic hydro-dynamic forces on a fixed sphere at different immersion levels. Diffraction tests are performed in a wave flume where an aluminium sphere is instrumented with a 3-axis load cell to measure the induced horizontal and vertical forces experienced while subjected to incident focused wave groups with different focus amplitudes. The force harmonics are separated using two-phase harmonic separation and subsequently analysed. The measured first harmonic excitation force is found to be consistent with numerical results across all immersion levels but exhibits weak amplitude dependency. The second and third harmonic excitation forces appear to be consistent with the expected quadratic and cubic dependence on the incident wave amplitude. The second-order super-harmonic surge force is found to be the same order of magnitude as the linear force for the largest amplitude case considered. Dependence of the first, second, and third harmonic excitation forces on the immersion level is also investigated, motivated by the small-body approximation for linear forces.