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Collaborating Authors
Shi, Wei
Comparative Study of Hydrodynamic Responses of Floating Offshore Wind Turbine Platform Under Focused Wave Using Experiment and OpenFOAM
Zhou, Yiming (Huaneng Clean Energy Research Institute) | Cai, Yefeng (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology / Faculty of Infrastructure Engineering, Dalian University of Technology) | Zhao, Haisheng (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology / Faculty of Infrastructure Engineering, Dalian University of Technology) | Shi, Wei (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology / Faculty of Infrastructure Engineering, Dalian University of Technology) | Li, Xin (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology / Faculty of Infrastructure Engineering, Dalian University of Technology) | Zeng, Xinmeng (College of Engineering, Ocean University of China)
ABSTRACT The present study investigates the effect of focused wave on floating offshore wind turbine platform based on open source toolbox OpenFOAM. The focused waves are generated based on the Pierson-Moskowitz spectrum in the waves2Foam toolbox; the multiphase solver waveFoam developed based on interFoam in OpenFOAM and kOmegaSST turbulent model are used to solve viscous, incompressible, multiphase flows, where PIMPLE algorithm is adopted to deal with the velocity-pressure coupling; the dynamic mesh technique is utilized to realize the 6-DOF (six degrees of freedom) motion of semi-submersible platform; moreover, the waves2Foam mooring module, viz., a static catenary model, is embedded into OpenFOAM to implement the analysis of mooring line connected with the floating platform. A comparative study of CFD simulation and model test is conducted, including focused wave test, static equilibrium test, free decay test, platform dynamic response and mooring line tension and the comparisons show good consistency. The test cases considered in this study are those proposed in the 1st FOWT Comparative Study. INTRODUCTION As an important composition of renewable energy, wind energy has been the subject of widespread interest and attention due to the continued development of wind power. To further tap into wind energy resources in the ocean, wind farm construction is gradually expanding from offshore to deep sea locations, driven by advancements in wind power technology. Floating offshore wind turbine (FOWT) platform is a common form of wind power foundation in deep sea environment due to their ability to adapt to complex marine conditions. However, FOWTs are more susceptible to experiencing extreme wave conditions in deep sea areas, which can potentially cause platform destruction and mooring line breakage. The study of the hydrodynamic characteristics of FOWT platforms under extreme sea wave conditions is of great significance for platform design and application.
Global Sensitivity Analysis of Offshore Wind Turbine Supporting Structures
Li, Zhichuan (Clean Energy Branch, CNOOC Energy Technology & Services Limited) | Qi, Bo (Clean Energy Branch, CNOOC Energy Technology & Services Limited) | Chen, Shi (Clean Energy Branch, CNOOC Energy Technology & Services Limited) | Zhu, Yongfei (Clean Energy Branch, CNOOC Energy Technology & Services Limited) | Han, Fucheng (Faculty of Infrastructure Engineering, Dalian university of Technology Dalian, Liaoning province) | Li, Xin (Faculty of Infrastructure Engineering, Dalian university of Technology Dalian, Liaoning province) | Shi, Wei (Faculty of Infrastructure Engineering, Dalian university of Technology Dalian, Liaoning province) | Wang, Wenhua (Faculty of Infrastructure Engineering, Dalian university of Technology Dalian, Liaoning province)
ABSTRACT Nowadays, the probabilistic-based design method is gradually getting attention as an alternative method in the design and analysis field of offshore wind turbines (OWTs) to substitute the traditional deterministic design methods, which account for the uncertainties existing in structural geometrical parameters, loadings, materials, etc. by employing partial safety factors (PSFs). However, the partial safety factors method is a simplified and indistinct approach because it condenses several uncertain parameters that affect the OWTs' performance into a factor, and it ignores the discrepancy in the structural responses caused by these different uncertainties. In this paper, the sensitivity analysis of the typical load characteristics and structural responses concerning structural geometrical parameters, metโocean parameters, and material behaviors are investigated for a 5 MW OWT installed on a monopile foundation. The standardized regression coefficients (SRC) method and elementary effects (EE) method are utilized for two different load cases. Results show that the same parameters have different significance rankings according to which load case is considered. In general, the highest influence on deformation and stress output are both governed by these metโocean parameters. This work points out the parameters that affect the OWT structural response and should be emphasized by the designers. INTRODUCTION Over the past decades, offshore wind energy has shown significant potential in the energy market. "The Global Wind Report 2022" released by the Global Wind Energy Council states that the accumulative total installed wind-power capacity by 2021 reached 94 GW. However, the Levelized cost of energy concerning offshore wind energy is still too high to be truly competitive compared to the traditional energy resource. It should be noted that the manufacturing cost of the supporting structures of the offshore wind turbines (OWTs) and the cost of operation and maintenance after the wind farm have been put onto nets represent a significant part of these costs. Hence, an obvious cost-reduction method is optimizing the supporting structures as far as possible, on the premise of ensuring the safe operation of the OWT during the whole lifespan. Generally speaking, the optimization design process of OWT needs to take into account numerous randomness factors, such as structural geometrical parameters, loadings, materials so on, and these factors are represented by a couple of partial safety factors (PSFs) in the prevailing designs (Yang et al., 2015).
- Asia > China (1.00)
- North America > United States (0.68)
Abstract China launched the Deep Resources Exploration and Mining (DREAM) program in 2016. Since then, the program has made significant progress in the exploration of critical minerals, such as rare earth, rare, and rare scattered metals. A โfive-in-oneโ model, based on climate, landform, parent rocks, carrier minerals, and pH values of weathering crust, has been established for rare earth prospecting in South China. It has led to a major breakthrough in the discovery of a new type of ion-adsorption rare earth deposit in the weathered crust of low-grade metamorphic rocks in southern Jiangxi, South China. A pegmatite beryllium (Be), skarn beryllium-tungsten (Be-W), cassiterite sulfide tin-tungsten-beryllium (Sn-W-Be), independent fluorite, and lead-zinc (Pb-Zn) vein five-in-one model was developed for the prospecting of rare metals such as Be and W and polymetals in the Zhaxikang-Cuonadong ore-concentrated area of the eastern Himalayas. A series of metallogenic models has been proposed for the investigation of lithium (Li) resources, leading to important breakthroughs in the prospecting of large to superlarge Li deposits in the Jiajika (western Sichuan), Dahongliutan (southwestern Xinjiang), and Xiaoshiqiao (central Yunnan) ore fields. Meanwhile, the DREAM program has achieved significant advancements in its knowledge of the ultranormal enrichment of indium, germanium, gallium, niobium, and rare earth elements in the western Yangtze block, Southwest China.
- Phanerozoic > Mesozoic (1.00)
- Phanerozoic > Paleozoic (0.68)
- Geology > Structural Geology > Tectonics > Plate Tectonics (1.00)
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.94)
- (2 more...)
- Geophysics > Electromagnetic Surveying (0.47)
- Geophysics > Gravity Surveying (0.46)
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Study of the Interactions Between Ice and Offshore Wind Turbine Using Cohesive Element Method
Liu, Yingzhou (Faculty of Infrastructure Engineering, State Key Laboratory of Coast and Offshore Engineering, Dalian University of Technology) | Wang, Bin (Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province) | Shi, Wei (Faculty of Infrastructure Engineering, State Key Laboratory of Coast and Offshore Engineering, Dalian University of Technology) | Wang, Wenhua (Faculty of Infrastructure Engineering, State Key Laboratory of Coast and Offshore Engineering, Dalian University of Technology) | Li, Xin (Faculty of Infrastructure Engineering, State Key Laboratory of Coast and Offshore Engineering, Dalian University of Technology)
ABSTRACT Ice bending fracturing is a major failure mode for sea ice act on offshore wind turbines (OWTs) with icebreaker. The cohesive element method (CEM) is applied to simulate the bending fracturing and fragmentation accumulation of the level ice in the presented study. The elastoplastic linear softening constitutive model is used to consider the characteristics of S2 columnar ice, and the transversely isotropic Tsai- Wu failure criterion is adopted to predict the ice failure. The proposed interaction coupling model is implemented into the LS-DYNA finite element code. Then, the sea ice crack expansion, breaking, sliding, and accumulation are observed under different ice velocities. Meanwhile, the numerical results are validated against the ice force model test data. Furthermore, the structural motion responses of the OWT under sea ice loads are investigated, and influence of ice velocities is observed. The results show that the ice velocity has no significant effect on ice force and structural motion response. However, the fracture size are decreased with the increasing of ice velocities. INTRODUCTION With the continuous exploration of wind energy resources (Zhao et al., 2021; Ren et al., 2022; Wang et al., 2022), the dynamic response prediction of offshore wind turbines (OWT) under the action of sea ice has become a hot issue in the structural design and safe use. However, the research on ice-OWT collision mechanism is still insufficient, at present. The interaction between ice and OWT structures is a complex process, which mainly includes the local crushing failure and bending failure of sea ice, and the accumulation, slippage and removal of broken ice (Riska et al., 1995; Aksens et al., 2010). These processes interact and couple each other, which propose challenges to the numerical simulation of sea ice-OWT interaction and the accurate prediction of ice load (Liu et al., 2022). Each failure shall change the geometry and boundary conditions of the subsequent ice, which can have an impact on the subsequent ice destruction (Kuutti et al., 2013). After the ice sheet produces fragments ice due to crushing and bending, a small part of the ice fragments will rotate and slide until it is removed, and most of the ice fragments will form an accumulation effect in front of the structure. The accumulation effect plays an important role in the ice-structure interaction was discovered by Mรครคttรคnen (1986) and Sanderson (1988).
- Well Completion > Hydraulic Fracturing (0.96)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (0.81)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.81)
Development and Verification of Data Exchange System for Real-Time Hybrid Model Test of Offshore Wind Turbines
Fu, Jie (Deepwater Engineering Research Center, Dalian University of Technology) | Zhou, Yiming (Huaneng Clean Energy Research Institute) | Shi, Wei (Deepwater Engineering Research Center, State Key Laboratory of Coast and Offshore Engineering, Dalian University of Technology) | Li, Xin (Faculty of Infrastructure Engineering, State Key Laboratory of Coast and Offshore Engineering, Dalian University of Technology) | Lv, Xiaojing (Huaneng Clean Energy Research Institute)
ABSTRACT Due to the huge energy production potential, offshore wind technologies have been developed rapidly in recent years. Offshore wind turbines often require physical model tests for performance evaluation and design verification. The real-time hybrid model test of offshore wind turbines is based on the sub-structure analysis principle of structural dynamics. The model tests and numerical calculations are coupled in real time to solve the scaling conflict that is difficult to achieve in traditional offshore wind turbine model tests. Since real-time interaction is necessary during the test process, it poses challenges to the solution of numerical sub-structures, loading of loader and data exchange between sub-structures. The present study aims to solve the key issue of data exchange between the numerical module and physical module. A UDP/IP communication mechanism was developed to exchange the information between numerical module in AeroDyn and physical test to replace the traditional TCP/IP system. With the UDP/IP the host can communicate directly with the controller which significantly reduces the time consumption during the process of data acquisition and transmission. The developed data exchange system was verified against a model test with a 1:90 scaled NREL 5 MW wind turbine supported by the monopile. This system provides a technical reference for the further development of real time hybrid model test of offshore wind turbine. INTRODUCTION With the aggravation of the global greenhouse effect, offshore wind power, as a new field of clean energy, has great energy production potential and is widely supported and developed in many countries around the world (Lv et al.,2017; Esteban et al.,2011; Musial et al.,2016; Ren et al.,2021; Wang et al.,2022). In order to make better use of high-quality wind resources at the sea, the energy capacity and the hub height of offshore wind turbine are constantly increasing, and the whole wind turbine structure tends to be in large-scale. At the same time, due to the limitation of the available offshore space and the superiority of deep-sea wind power, offshore wind turbines have been developed from fixed offshore to floating offshore (Perveen et al.,2014). The development of the whole offshore wind power has continuously moved from offshore to deep-sea, which will lead to a more complex and extreme marine environment. In order to better ensure the structural integrity and operational safety of offshore wind turbines during their service life, it is necessary to strengthen the research on the structural performance and coupling mechanism of offshore wind turbines in the complex marine environment.
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (1.00)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
Experimental Investigation of Hydrodynamic Coefficients of Heave Plates for Floating Offshore Wind Turbines
Zhang, Lixian (Deepwater Engineering Research Center, Dalian University of Technology) | Shi, Wei (Deepwater Engineering Research Center, State Key Laboratory of Coast and Offshore Engineering, Offshore Renewable Energy Research Center, Dalian University of Technology) | Michailides, Constantine (International Hellenic University) | Zheng, Siming (School of Engineering, Computing and Mathematics, University of Plymouth) | Li, Xin (Faculty of Infrastructure Engineering, State Key Laboratory of Coast and Offshore Engineering, Dalian University of Technology)
ABSTRACT The hydrodynamic damping and added mass coefficients resulted by the use of the heave plates placed at the floating offshore wind turbine (FOWT) platform are discussed and presented via an experimental approach. Different diameters of the heave plates are designed. The objective of this paper is to investigate the contribution to the damping and added mass coefficients for different diameters of the heave plates by using forced oscillations of the FOWT. The effects of Keulegan-Carpenter (KC) number range from 0.18 to 1.11 and frequency of forced oscillation range from 0.40 Hz to 1.43 Hz and heave plate drafts range from 0.34 m to 0.42 m to the hydrodynamic coefficients were also analyzed. Over a variable Dd / Dc(D - the diameter of the heave plates, Dc -the diameter of the column) range from 1.5 to 2.5, calculations indicate that the diameter of the heave plates affect the hydrodynamic coefficients of the FOWT platforms. In addition, the hydrodynamic coefficients of the heave plates are quite different with different KC numbers. INTRODUCTION Compared with traditional offshore oil and gas industry(Peng et al., 2021), Floating offshore wind turbines (FOWTs) are considered to be good designs to exploit the tremendous wind energies in deep waters (Cheng et al., 2021; Ren et al., 2022; Wu et al., 2019). Among all the types of FOWTs, semisubmersible FOWTs have attracted more attention due to the low construction cost, competitive mooring system cost, and wide applicability of water depth (Liu et al., 2016; Wang et al., 2022). The semisubmersible FOWTs mainly consist of three columns connected by a set of braces (Zhang et al., 2020; Zhao et al., 2021). Large heave motion responses, will threaten the safety of the mooring systems and affect the efficiency of the power generation (Tao and Dray, 2008). To reduce the heave motions, heave plates are often attached at the bottom of the columns of semisubmersible FOWTs (Kvittem et al., 2012; Roddier et al., 2010).
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (1.00)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.92)
Experimental Study of a TLP-Type Floating Offshore Wind Turbine with Tendon Failure
Ren, Yajun (Institute for Energy Systems, the University of Edinburgh) | Venugopal, Vengatesan (Institute for Energy Systems, the University of Edinburgh) | Zhou, Yiming (Huaneng Clean Energy Research Institute) | Shi, Wei (Deepwater Engineering Research Centre, State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology)
ABSTRACT In this paper, a description of physical model tests conducted on a newly designed 5-MW TLP Floating Offshore Wind Turbine (FOWT) scale model with failed tendon and its results, are presented. The TLP FOWT is designed for moderate water depths of 60 m. A scale factor of 1:50 is used for the experiments. The free-decay tests, regular and random wave tests, and tendon broken tests are carried out in Dalian University of Technology's wave basin. The natural frequencies, motions of the platform and the corresponding response amplitude operators (RAOs), and forces on the tendons were obtained by the experiments. The results from the experiments show that, after the tendon failure occurred, the tendons adjacent to the broken one suffers from the significant increase of tension force. The outcomes of this research are expected to provide new knowledge towards the design of TLP FOWT with failed tendons. INTRODUCTION Tension leg platform (TLP) is seen as a key technology for floating offshore wind turbine (FOWT). As the stability of the platform is provided by the tension forces from its tendons and the excessive buoyancy of the hull, the platform has the potential to significantly reduce structural costs due to the reduced steel weight. The existing TLP FOWT concepts [e.g. Matha (2009), Ding et al. (2016) and Zhao et al. (2012)], were normally designed for water depths larger than 150 m. However, in many countries, for a large part of the ocean, the available water depth for FOWT installation is less than 100 m; therefore, design and analysis of TLP based FOWTs for intermediate water depths is critical and such designs will provide a stable and cost-effective alternative (Ren et al., 2022; Zhao et al., 2021). For TLP-type FOWTs, one of the particular concerns is the extremely high tension in the tendons. Since the stability of the structure is completely provided by the mooring system, the damage of the tendon, either by accident or fatigue, can lead to serious consequences. Several studies have assessed the effect of mooring failure on different types of FOWT. Bae et al. (2017) revealed that the damage of one mooring line in a semi-submersible FOWT can lead to significant drift of the platform. Wu et al. (2021) investigated the effect of tendon failure on a WindStar TLP FOWT, which showed different outcomes from Bae et al. (2017). It was reported that the change of response as the result of tendon failure is mainly observed in the transient increase of tower top acceleration and the tension force, while the responses in surge and heave are not significantly affected. However, the research in this area is still solely based on numerical modelling, while the reliability of the results may be questioned.
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (1.00)
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.92)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Mooring systems (0.89)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (0.83)
Abstract Iron Sulfide (FeS) scale is known as a troublesome scale during oil and gas production. The prevention of FeS precipitation in the injection water for a sour carbonate reservoir was required with an injection brine of low Fe concentration (10 mg/L) and high Ca concentration (5,000 mg/L). This work was proposed to identify a chemical which is able to effectively chelate Fe in the presence of high calcium to prevent or reduce the formation of FeS. Anaerobic bottle tests were conducted at 95ยฐC for 24 hours to compare the performance of selected chemicals, i.e., EDDS (Ethylenediamine-N,Nโ-disuccinic acid), DTPA (Diethylenetriamine Pentaacetic Acid), EDTA (ethylenediaminetetraacetic acid), THPS (Tetrakis(hydroxymethyl) phosphonium sulfate), and citric acid (CA). Several sets of performance test were conducted: a. with other cation ions and without other cation ions to compare the effects of other cations on chelation; b. with the aged and non-aged product, ie. product aging test at 250ยฐF for 7 days, to understand the effects of temperature on chemical stability; c. with 1.0 g/L and 10 g/L pre-existing calcite solids effects on the FeS chelation performance to simulate the carbonate reservoir conditions; d. with various Fe level of 10 ppm, 50 ppm, and 100 ppm. Citric acid and THPS showed better chelation performance on Fe than other tested chemicals. The effects of the presence of pre-existing calcite solids on citric acid and THPS were also investigated to simulate the interaction of chemicals with the carbonate formation. The chelation performance of citric acid was affected by the addition of calcite due to the reaction of citric acid with calcite solids. THPS is not affected by the presence of calcite solid at either 1.0 g/L or 10 g/L. From the above testing results, THPS is recommended for the field applications. This study systematically investigated FeS control and prevention chemical selection and presents the laboratory results to identify the best performance. It provided an insight into the influence of several potential application conditions, e.g., high levels of calcium and other cation ions, pre-existing solids from carbonate reservoir, and long-time exposure to application temperature (250ยฐF), on the selected chelator performance. This work also established a guideline for chelator dosages during field applications to successfully manage FeS scale.
- Asia > Middle East (0.46)
- Europe > United Kingdom > Scotland (0.29)
- North America > United States > Texas (0.28)
- Geology > Mineral > Carbonate Mineral > Calcite (1.00)
- Geology > Mineral > Sulfide > Iron Sulfide (0.68)
- Materials > Chemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Lifecycle > Disposal/Injection (0.86)
Hydrodynamic Analysis of a Floating Hybrid Renewable Energy System
Wang, Yapo (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Shi, Wei (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Zhang, Lixian (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Michailides, Constantine (Cyprus University of Technology) | Zhou, Li (School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology)
ABSTRACT Due to the energy crisis and green-house effect, offshore renewable energy is attracting more attention in the world. Various offshore renewable energy systems such as floating offshore wind turbines (FOWTs), wave energy converters (WECs), have been developed. To increase the power output and reduce the costs, a hybrid renewable energy system using FOWTs and WECs technologies has been designed, analyzed and presented in the present paper. The hybrid system combines a 5-MW braceless semisubmersible FOWT with a heave-type WEC. The WEC is installed on the floating central column of the braceless semiplatform. Wave power can be absorbed by a power-take off (PTO) system through the relative heave motions between central column of FOWT and the WEC. The hydrodynamic response of the hybrid system is investigated using a panel model and the numerical modeling of the combined system is presented. The effect of different power-take-off (PTO) system parameters, wave periods as well as wave heights on the performance of the WEC's wave energy production under typical wave conditions have been investigated, and a preliminary optimal value for the PTO's damping coefficient with different wave height has been obtained. Meanwhile, the motion and dynamic response of the hybrid system has been investigated under typical operational and extreme sea states. INTRODUCTION Due to the exhaustion of fossil fuels and its pollution to the environment, people are trying to develop various clean and renewable energies to replace the conventional energy resources. Offshore wind energy has experienced a rapid development during past ten years. The ocean contains a variety of clean and renewable resources such as wind energy, wave energy and tidal energy. Due to the natural correlation between wind and wave, the wave energy resources of wind-enriched waters are also considerable. Integration of offshore wind energy and wave energy power generation shares the supporting structure and energy transmission system, which not only improve the utilization efficiency of marine renewable energy, but also effectively reduce the LCOE.
Model Tests of a TLP Floating Offshore Wind Turbine with a Porous Outer Column
Mackay, Ed (University of Exeter) | Johanning, Lars (University of Exeter) | Shi, Wei (State Key Laboratory of Coastal and O?shore Engineering, Dalian University of Technology) | Ning, Dezhi (State Key Laboratory of Coastal and O?shore Engineering, Dalian University of Technology)
This paper presents the results of scaled model tests of a tension leg platform (TLP) for a floating wind turbine, comprising a central solid cylinder with a porous outer cylinder. Tests were conducted with outer cylinders with porosities of 0%, 15% and 30% and compared to a base case with no outer cylinder. For each configuration, the total mass and centre of mass are kept constant to allow consistent comparison. It is shown that for the cases with a solid outer cylinder the surge motion resonance is shifted to a lower frequency due to the entrained mass of water inside and increased added mass of the outer cylinder. Increasing the porosity of the outer cylinder is shown to increase the frequency of the resonant response, bringing the resonant frequency closer to that of the base case with no outer cylinder. Increasing the porosity of the outer cylinder also reduces the amplitude of the resonant response. The use of a porous outer layer increases the quadratic drag on the body and significantly reduces the low frequency resonant response where the radiation damping is low. INTRODUCTION A key challenge for developing cost-competitive floating offshore wind is the e cient design of stable platforms. Large platform motions can lead to reduced energy yield and increased fatigue loads on the turbine. Adding a porous outer layer to a floating platform has the potential to reduce platform motions without significant increase in size and cost. Porous structures are commonly used in fixed and floating breakwaters to dissipate wave energy and reduce wave disturbance (e.g. Huang et al, 2011; Dai et al, 2018). The use of porous structures has also been investigated for motion damping and load reduction on fixed offshore structures (e.g. Molin, 1990; Molin, 2011; Park et al, 2014) and floating structures (e.g. Downie et al, 2000a,b; Williams et al, 2000; Lee & Kerr, 2002; Park et al, 2013; Vijay & Sahoo, 2018).