bluuebunny/crossref_metadata_2025_split huggingface dataset:
NextFloat: Light Is Beautiful, Use of Lattice Structure in Floating Wind
Authors: Cahay Marc , Milde Lucy 
Published: August 2024

Abstract
Since the Hywind Demo project, the first Floating Offshore Wind Turbine (FOWT) of 2.3 MW installed 12 km offshore Karmøy island, South West of Norway by Equinor in 2009, up to the ongoing Hywind Tampen floating wind farm composed of 11 units of 8.6 MW to provide electricity for the Snorre and Gullfaks oil and gas fields in the Norwegian North Sea, most of the FOWT deployed are spread moored to the seabed and use upwind 3 bladed turbines.
Some other small scale prototypes using catenary or tension legs, spread or single point moorings, single or multi-turbine configurations and upwind or downwind turbines were also tested during this period in a variety of environments.
The NextFloat project (European Commission Grant Agreement n°101084300 under Horizon Europe program) has started in November 2022. NextFloat will engineer and build an innovative weathervanning concept of FOWT that will be deployed and operate on the Mistral test site in the South of France near Marseille. The unit will be a 6 MW version of the PivotBuoy previously deployed by X1-Wind on the PLOCAN site in the Canary Islands.
This innovative platform concept specifically developed by X1-Wind for floating offshore environments in deep waters combines the advantages of a semi-submersible and TLP through its single-point mooring (SPM, called PivotBuoy®). The result is a downwind tripod-like platform that self-aligns passively with the wind allowing an efficient structural design eliminating also the traditional tower (which suffer high bending moments at its base and is very sensitive to 1P/3P excitations). Substantially lighter, the downwind tripod structure is a more easier and scalable design than the SPAR, semi or barge existing technologies. Furthermore, the use of lattice structure for the tripod legs allows a high weight saving of more than 1000 tons compared to the typical tower structure for the future 20MW+ turbines. Those benefits will be detailed in the publication including a comparison with tower solution based on structural calculation of stresses usage ratios and natural periods.
Pull-Out Capacity of Suction Anchors Considering Trench Effect: A Numerical Study
Authors: Zhang Min-Hao , Fu Yong , Yin Zhen-Yu 
Published: August 2024

Abstract
With the increasing utilization of suction anchors in mooring systems, field surveys have observed seabed trenches near suction anchors caused by anchor chain motion and soil erosion. The presence of these trenches significantly reduces the pull-out capacity of suction anchors, emphasizing the need for attention. This study investigates the impact of seabed trenches on the undrained pull-out capacity of suction anchors at an optimal padeye depth through a series of finite element analyses. Rectangular cross section trenches are considered in this study. The effects of trench size, trench distance, trench shape and local scour on reducing the pull-out capacity of suction anchors are systematically examined. Furthermore, we present an optimal design approach for suction anchors considering seabed trenches that addressed two aspects: (a) determining whether higher pull-out capacity can be achieved by relocating the anchor padeye to a shallower depth and reducing trench depth; and (b) identifying the optimal anchor aspect ratio considering material cost and seabed trench conditions. These analyses provide valuable insights for practical design considerations when dealing with trench-related issues encountered by suction anchors.
Full-Field Strain Estimation From Measured Accelerations of Offshore Wind Turbine Support Structures
Authors: Guo Jianxun , Li Yanchen , Wu Xinyan , Tian Zhe , Liu Fushun 
Published: August 2024

Abstract
The strain history of an offshore wind turbine (OWT) during its operational phase is an essential parameter for assessing safety and estimating its remaining lifespan. In this context, a strain estimation scheme is proposed in this paper, which uses the measured acceleration to estimate the strain state of the OWT support structure. The proposed method relies on the adaptive displacement reconstruction technique in conjunction with the evolutionary orthogonal based response expansion method, which is implemented as an in-house code in numerical software. A mapping process is achieved to obtain full-field strain in the numerical space from measured acceleration in the physical space of the OWT support structures. The advantage of this approach is that it solely depends on the measured acceleration and structural geometry, without requiring measured displacement, strain or modal information. To assess the validity of the proposed method, physical experiments under cyclic loading were carried out on a scaled wind turbine model equipped with acceleration, laser displacement and Fiber Bragg Grating sensors as reference measurements. The results demonstrate that the proposed method could accurately predict the dynamic strain of the wind turbine support structures, while an excellent agreement between the estimated strain and the measured response from the Fiber Bragg Grating is observed, which provides valuable insights for the development of a strain monitoring system applicable to the OWT.
The Influence of Jacket Orientation on Integral Horizontal Forces For a Large 3-Legged Jacket Under Collinear Wave-Current Impact
Authors: Wynants Mareile , Schendel Alexander , Welzel Mario , Kerpen Nils , Schlurmann Torsten 
Published: August 2024

Abstract
Amidst the backdrop of the European “Green Deal,” mandating climate neutrality by 2050, the expansion of offshore wind energy in the German North Sea gains increasing significance. The projected trend in offshore wind energy turbines (OWTs) towards exceeding 20 MW, with hub heights surpassing 240 m and rotor diameters over 300 m, demands a concomitant shift in substructure design. Jacket-type substructures, tailored for sites with larger water depths, are expected to increase individual pile diameters or overall structural density to bear the new, markedly increased top loads. These Offshore Megastructures present a new approach to traditional slender structures. This study investigates the impact of individual and combined wave and current conditions on a 3-legged jacket-type Offshore Megastructure in a 1/140 scale laboratory study. The structure, a simplified iteration designed to support a &gt; 20 MW OWT, was mounted to a load cell for monitoring integral horizontal loads. Testing encompassed current-only, wave-only, and combined wave-current scenarios in both following and opposing configurations. Reference tests without structure, with a monopile, and tests with the jacket structure oriented at 0°, 15° and 30° were executed. Findings illustrate an influence of both wave steepness and jacket orientation on the integral horizontal forces. This relation changes in dependency of the presence and orientation of a superimposed current for values of wave steepness H/L &gt; 0.01.
An Efficient HOS-SPH-BEM Coupling Method for Wave-Structure Interaction Problems
Authors: Xie Chunmei , Yang Juncheng , Sun Pengnan , Ni Xinyun , Wang Qibin , Ye Yonglin 
Published: August 2024

Abstract
In this paper, a potential-viscous coupling method based on Xie’s HOS (Boundary Element Method)-SPH (Smoothed Particle Hydrodynamics) coupling method is proposed by introducing the BEM (Boundary Element Method). The domain decomposition model is adopted with the HOS method generating the incident waves, the BEM propagating the radiation and diffraction waves in the far field, and the SPH method used in the near field around the structure for simulating the wave breaking and nonlinear wave-structure interaction. Therefore, the whole coupling method can be divided into two parts: one-way coupling of HOS-SPH (which has been studied in Xie et al.’s paper) and two-way coupling of SPH-BEM. Similar to Xie et al.’s, Grid2Grid is used to connect the HOS and SPH, meanwhile the velocity and pressure transformation between SPH and BEM is achieved by a linear blending scheme. This coupling method combines the advantage of the potential methods in generating and propagating waves quickly and accurately and the SPH method in adopting the strong nonlinear free surface problems. The numerical results of the HOS, SPH, BEM and SPH-BEM coupling methods are validated by calculating regular and irregular waves. The accuracy of the whole coupling method was verified through the interaction between a two-dimensional freak wave and a three-degree of freedom floating body. Compared with experiment data, the HOS-SPH-BEM coupling method can effectively improve computational efficiency and extensively reduce numerical dissipation. It removes the reflected waves in Xie’s HOS-SPH coupling method.
Numerical Studies on Dynamic Responses of Honeycomb Sandwich Plate Under Slamming Loadings
Authors: Liao Yong , Guo Kailing , Zhu Ling , Yang Weixiang , Dai Shaoling 
Published: August 2024

Abstract
When ships travel with high speed in rough sea, the hull may be subjected to impact loading from water, and the phenomenon of slamming will appear. It may produce large slamming force which can lead to severe damages on the local structures of the ship, sometimes may cause accident. The honeycomb sandwich structure is one kind of lightweight structures, and possesses excellent performance on energy absorption. Hence honeycomb sandwich structure has great application prospect in impact protection.
In this paper, based on Arbitrary Lagrangian-Eulerian (ALE) method, the fluid-solid interaction numerical simulation model on aluminum honeycomb sandwich plates (AHSPs) is established, and the characteristics of slamming loads and structural responses are analyzed. Meanwhile, the accuracy of the numerical simulation has been verified by comparing the slamming pressure and permanent deflection of the numerical simulation with those of the slamming experiment. Based on the numerical method, the influence of the μ (face sheet thickness ratio) on slamming load and dynamic structural responses is investigated. The relationship between slamming pressure, structural responses and energy absorption with μ is analyzed. Results show that, with the increase of μ, the deformation of the front sheet and the honeycomb decrease gradually, while the deformation of the back sheet increases gradually. In terms of energy absorption, as μ increases, the front sheet increases gradually, while the back sheet and the honeycomb decrease gradually. Besides, the peak value of slamming pressure increases linearly with the increase of μ. Therefore, the proper decrease of μ can reduce the plastic deformation of AHSPs. The studies in this paper can provide reference for the design of ship structures suffering from slamming loads and improve the structural safety.
A Modular Steel Gravity Foundation (MSGF) for TLP Floating Offshore Wind Turbine (FOWT) Tendon
Authors: Periyaiah Rathinam , Huang Edward , Tang Zhaoxiang , Erten Mustafa , Tavassoli Moe 
Published: August 2024

Abstract
In general, Tension Leg Platform (TLP) demonstrates exceptional dynamic behavior with very low displacements and almost no vertical / rotational motions. Its lightweight structure and simple geometry lend themselves to simplifying fabrication / integration processes and competitive Levelized Cost of Energy (LCOE) levels. Furthermore, the much smaller footprint of TLP mooring compared to other alternatives like Semis or Spars allows for better accommodation for fishing and shipping lanes. However, the major cost driver for the TLP as an option of foundation system for Floating Offshore Wind Turbine (FOWT) is the cost of tendon systems and its installation, including the tendon foundation. The TLP with simplified installation method of Modular Steel Gravity Foundation (MSGF) and Tendon presented in this paper will make the TLP option much more competitive and reduce the overall LCOE.
The MSGF as TLP FOWT Tendon foundation is an innovative method of installing the traditional gravity base foundation. The proposed modular solution offers a simple, noiseless, and environmentally friendly installation process. It requires a simple decommissioning process without the need to mobilize a high day-rate installation vessel. It is suitable for all types of seabed soil conditions since the design can be adjusted to suit any support ground condition, and its components can be sized and designed within the handling capacity of locally available installation vessels. The above uniqueness of the MSGF foundation option results in a significant reduction in the installation schedule and cost of a FOWT. This paper contains the MSGF configuration and sizing for TLP with pontoon Extension (ETLP) tendon for the US west coast 15MW FOWT, including the design load conditions and design loads. It also provides details of foundation modules and the sequences of module fabrications, transportation, and installation. Additionally, this paper includes the execution plan for foundation installation, addressing the local supply chain and logistics, as well as providing a high-level cost estimate. This study finds that the MSGF option for ETLP FOWT reduces the foundation component level LCOE significantly compared to the traditional pile foundation.
Preliminary Numerical Assessment of Marine Turbines With Rigid Blades Using Low Reynolds Approach
Authors: Paredes Rubén J. , Zambrano Paul S. , Marin-Lopez Jose R. , Jasak Hrvoje 
Published: August 2024

Abstract
Tidal turbines with morphing blades could increases the mean time to failure of turbine blades and drive trains by mitigating power and loads fluctuations associated with the larger scales of the turbulent tidal stream flow. However, the numerical modeling of this fluid-structure interaction problem would require expensive high performance computing infrastructure to obtain results in a reasonable time. In order to develop this analysis capability, the goal of the present work is to identify the numerical setup details in OpenFOAM framework to assess the performance of the Oxford tidal turbine with rigid blades. For this, thrust and torque predictions were used to assess the performance of this turbine considering the steady inflow condition of with a rotor tip-speed ratio of 5.82 and turbulence intensity of 3.1%. For the near-wall treatment, a κ-ω SST turbulence model with low Reynolds number approach was used. Thrust and torque predictions using a grid with element size of 1.5%D in the turbine region have and error of 0.5% and 14.8% respectively. Also, a 1/15 power law velocity profile was assumed to assess its effect on load fluctuations. Further, a reduced order model will eventually be implemented to capture blade deformation and reduce load fluctuations.
A Preliminary Experimental Study of a Dual-Function Slotted Barrier Integrated With an Oscillating Water Column for Wave Energy Extraction and Shore Protection
Authors: Huang Zhenhua , Walker Mayah , Reyes Clint C. M. , Cross Patrick 
Published: August 2024

Abstract
Wave energy conversion is a promising technology to provide renewable energy, but its commercialization is limited mainly due to high initial investment and maintenance cost. One way to improve the economic feasibility of wave energy utilization is to integrate wave-energy converters (WECs) into shore-protection structures to form dual-function structures, which have the capability to harness wave energy for electricity generation and provide coastal protection. Among different types of existing WECs, oscillating water columns (OWCs) have the power takeoff (PTO) system out of water, which greatly reduces the influence of befouling on PTO performance and lowers maintenance cost. This study introduces a dual-function design by integrating an OWC-type WEC with a bottom sitting slotted barrier. For these types of dual-function structures, the main design objectives are to achieve the designed transmission coefficient, maximize the wave power extraction, and minimize the wave loading on the structure. In this study, we present preliminary results of an experimental study of the proposed dual-function structure in a small wave flume equipped with a piston-type wave generator. In the experiment, a circular orifice at the top of the pneumatic chamber was utilized to emulate the PTO system. Wave power extraction was measured using a differential pressure sensor. Wave loading on the structure was measured using a single-axis force balance. The focus of this study is to observe the effects of tide level and the porosity of the slotted barrier on the wave power extraction, wave transmission and wave loading under different wave conditions. Two slotted barriers and two water depths were studied. Main results reported include reflection, transmission and energy loss coefficients, wave power extraction efficiency, and wave loading.
Reinforcement Learning Driven Ship Biofouling Cleaning Strategy Optimization Considering Carbon Emission
Authors: Wei Qikun , Cheng Jianda , Xiang Gong , Liu Yan 
Published: August 2024

Abstract
The world has seen a rapid transition to a lower carbon future. As part of the global move, the marine field has been making effort to achieve a sustainable development. Ship biofouling adds resistance during navigation which not only increases cost of shipping operation but also weakens the competitiveness of vessels in terms of carbon reduction and efficiency improvement. Ship biofouling cleaning is an indispensable maintenance task in the life-cycle of ships. The fouling cleaning creates additional expenses and impacts schedules of shipping operation. Therefore, an appropriate strategy based on biofouling conditions is essential for cost optimization. This paper establishes a multi-state biofouling growth model based on Markov chain and solves the optimal strategy by reinforcement learning. An illustration case of a container ship is presented for verification. The proposed method is effective and efficient to support state-based decision making of stakeholders for reducing cost and carbon emissions.
Three-Dimensional Vortex-Induced Vibrations of Catenary Risers Under Sheared Flows at Different Incidence Angles
Authors: Ma Bowen , Srinil Narakorn 
Published: August 2024

Abstract
Marine risers may experience a complex vortex-induced vibration (VIV) owing to the enhanced nonlinear effects from structural curved shapes versus sheared flows. Many studies have focused on VIV of straight risers in sheared flows or curved risers in uniform flows. In this study, a numerical prediction model is advanced to investigate the multidirectional VIV of a catenary riser subjected to linearly sheared flow. The prediction model is described by equations of three-dimensional responses of the catenary riser coupled with the spatially distributed nonlinear wake oscillators calibrated against experimentally observed VIV responses of curved cylinders. Hydrodynamic lift and drag forces are mathematically modelled based on fluid-structural variables accounting for effects of space-varying riser local inclinations, vortex excitation frequencies and relative flow-cylinder velocities following the Independence Principle. The coupled VIV system is discretized in space by a second order finite difference scheme and integrated in time. To validate the model, simulations are performed based on a flexible curved cylinder under the concave sheared flow and compared with experimental results in the literature. By varying the relative directions between the riser equilibrium and the incoming flow in planar and non-planar configurations, VIV responses of a long flexible catenary riser in a uniform free stream flow versus a linearly sheared flow are compared and analysed in terms of amplitudes, resonant frequencies, lock-in conditions, and energy transfer mechanisms under perpendicular, convex and concave flows. Typical VIV features are captured alongside travelling wave responses, modulated amplitudes and frequency switching caused by sheared flows. Overall results highlight the influence of sheared flows on multidirectional VIV features.
Three-Dimensional Flow Around a Span Shoulder of a Pipeline/Cable: Insight From Experiments Combined With Numerical Modelling
Authors: Zhang Bingchang , An Hongwei , Draper Scott , Jiang Hongyi , Cheng Liang , Zhao Xu 
Published: August 2024

Abstract
Current-induced three-dimensional (3-D) scour below offshore pipelines and cables (P/Cs) is a concern in both the offshore oil and gas industry and the offshore renewable energy industry. This 3-D scour phenomenon can lead to elongation of free spans and control the time scale of self-burial. Thus, much experimental research has focused on span elongation due to 3-D scour. However, due to limitations in measurement techniques, especially in accurately assessing the flow structure in the gap, the scour propagation mechanism is not well understood. In this study, scour propagation below a pipe in steady current was investigated experimentally, and the 3-D flow around a span shoulder was further studied using a 3-D numerical RANS model. The experimental results and numerical simulations show that the scour propagation may be attributed to two processes: erosion induced by 3-D flow on the upstream side of the span shoulder, and spanwise avalanching (or sand sliding) towards the scour hole on the downstream side of the span shoulder. The numerical results indicate that the flow is highly three-dimensional at the scour front; a spiral flow forms upstream side of the scour front with the maximum spanwise flow velocity reaching 0.32Ūa under the pipe.
Cyclically Buckling/Plastic Collapse Behavior of Deck Beam-Column Obtained by Fluid-Structure Interaction Analysis for Floating Structure in Waves
Authors: Imai Nao , Toh Kimihiro , Yanagihara Daisuke 
Published: August 2024

Abstract
Fluid-structure interaction analysis applying ICFD solver incorporated in ANSYS LS-DYNA is applied to rigid motion of a floating box and hydro-elastic motion of a slender floating beam in waves, and the fundamental validity is confirmed comparing with the past test results and theoretical solutions. A structure with a slender beam-column in the deck is assumed to be floated in waves. The cyclically buckling/plastic collapse behavior of the deck and the overall bending response of the whole structure are examined through the fluid-structure interaction analysis varying the slenderness ratio of the deck. As a result, it is found that both the tensile and compressive load-carrying capacities of the deck are reduced with an increase in the number of wave encounters and this tendency becomes remarkable in the slenderer deck. The reduction of the compressive capacity especially depends on the residual deflection of the buckled deck. Regarding the bending moment acted on the whole structure, the maximum hogging moment is obtained just when the tensile axial force of the deck attains the peak. However, the sagging moment continuously increases even after the compressive force attains the peak because the intact bottom part can be subjected to a further moment. The overall bending deformation of the whole structure is influenced by the reduction of the load-carrying capacity of the deck after the peak.