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Eric Didier National Laboratory for Civil Engineering, Hydraulics and Environment Department Lisbon, Portugal Paulo R. F. Teixeira Federal University of Rio Grande, Engineering School Rio Grande, Rio Grande do Sul, Brazil This study aims to validate a numerical model based on Reynolds-averaged Navier-Stokes (RANS) equations to simulate the wave-interaction between regular incident waves and the overtopping-type wave energy converter. Results of the overtopping device with two reservoirs in small scale are compared with experiments. The methodology, which includes the use of a hybrid k-shear stress transport turbulence/laminar model, achieves good results, especially considering the difficulties of numerical models to reproduce overtopping because of the complexity of involved phenomena. Water wave energy has great potential to contribute significantly with this type of energy source. However, technical difficulties, such as high capital and maintenance costs, low efficiency, and structural risks as a result of storms, still restrict its use to some prototypes. Many approaches have been developed to overcome these challenges.
- North America > United States (0.46)
- Europe > Portugal > Lisbon > Lisbon (0.34)
- South America > Brazil > Rio Grande do Sul (0.24)
_ In this study, we perform CFD simulations for the NTNU Blind Test 2 experiment, in which two turbines were placed in a closed-loop wind tunnel and operating in line. The Reynolds-averaged Navier Stokes (RANS) equations with the k-ω SST turbulence model are adopted in the simulations. For each of the two wind turbines, geometries including the blades, hub, nacelle, and tower are fully resolved. The Moving-Grid-Formulation (MVG) approach with a sliding interface technique is leveraged to handle the relative motion between the rotating and stationary portions of the wind turbines. In the simulations, the values of tip-speed ratio (TSR) for the upstream and downstream turbines are 4 and 6, respectively. The CFD-predicted thrust and power coefficients are obtained under an inlet velocity of 10 m/s and are compared against the experiment results. In addition, the wake structures of the two wind turbines are also visualized and discussed. Introduction The wake generated by a horizontal-axis wind turbine (HAWT) is characterized by a decrease in wind velocity and an increase in the turbulence level compared to the free stream condition. Grouped in clusters in modern onshore and offshore wind farms, wind turbines will unavoidably be operating in the wake of upstream turbines. Therefore, the power generation efficiency of the downstream wind turbines in a wind farm will decline, and as a result, the overall power generated by a wind farm will be affected (Vanderwende et al., 2016). Researchers estimated that the overall power loss of a large wind farm is 10%–25% (Wu and Porté-Agel, 2015). To fulfill the potential of wind power as a major source of clean energy in the future, higher-efficiency wind turbines and wind farms need to be designed. Therefore, as the premise of the wind farm layout optimization algorithms, accurate prediction of the wind turbine wakes and wake interactions is of great importance.
- Europe (0.68)
- North America > United States (0.47)
Changing Soil Response During Episodic Cyclic Loading in Direct Simple Shear Tests
Laham, Noor (University of Southampton, Southampton) | Kwa, Katherine (University of Southampton, Southampton) | Deeks, Andrew (Norwegian Geotechnical Institute, Oslo) | Suzuki, Yusuke (Norwegian Geotechnical Institute, Oslo) | White, David (University of Southampton, Southampton) | Gourvenec, Susan (University of Southampton, Southampton)
_ Undrained cyclic loading of normally consolidated clays, interspersed with consolidation (i.e., episodic cyclic loading), has been shown to lead to softening followed by hardening, manifested by evolving parameters such as strength, stiffness, and coefficient of consolidation. The current evidence base is drawn from tests in which soil strength has been fully mobilized in each cycle of loading, whereas in practice, changes in stress around a geotechnical infrastructure typically occur only at a prefailure level. This paper presents results from a set of stress-controlled episodic cyclic direct simple shear tests imposing prefailure stress reversals in each cycle. Differences in soil response are identified for the same total number of cycles of loading but imposed through packets of different numbers of cycles and, consequently, different numbers of intervening consolidation stages. The results highlight the effect of load history on operational soil properties and quantify the effect of the undrained prefailure cyclic loading history on the evolution of the soil properties, supporting the application of whole-life geotechnical design in practice. Introduction The global energy industry is going through a significant period of transition aiming to net zero greenhouse gas emissions in the coming decades, and renewable energy is expected to be one of the fastest-growing energy sources globally (International Energy Agency, 2021).
- Europe (0.94)
- North America > United States (0.28)
Large Eddy Simulations of Wake Flows Around a Floating Offshore Wind Turbine Under Complex Atmospheric Inflows
Xu, Shun (Shanghai Jiao Tong University, Shanghai) | Wang, Nina (Huadong Engineering Corporation Limited) | Zhuang, Tiegang (Huadong Engineering Corporation Limited) | Zhao, Weiwen (Shanghai Jiao Tong University, Shanghai) | Wan, Decheng (Shanghai Jiao Tong University, Shanghai)
_ This study performed numerical investigations of a floating offshore wind turbine under a complex atmospheric boundary layer inflow. The complex and realistic ABL inflow was generated by large eddy simulations, and wind turbine blades were modeled by the actuator line model. The platform motions were solved by potential theory. A baseline case with a uniform inflow condition was conducted to provide some comparable data. The difference of the aerodynamic power in the two inflow scenarios is minor, except that small bumps in the atmospheric scenario are observed. The yaw moment is significantly enhanced as a result of the lateral asymmetry of the atmospheric inflow on the rotor plane. A significant observation of this study is the large-scale wake meandering caused by the presence of atmospheric turbulence structures. In addition, the high-velocity atmospheric airflow enters in the wind turbine wakes, and its mixing with the low-velocity wakes leads to a faster wake recovery. Introduction In recent years, with the great development of society, traditional fossil resources have had difficulty meeting the significant energy demands. Wind energy harvesting has received increasing attention because wind is a nonpolluting, renewable resource (Chehouri et al., 2015), and the increase in harvesting is responsible for the promising growth of wind turbine technology. According to the 2021 Global Wind Energy Report (Global Wind Energy Council, 2021), the installed capacity of wind turbines in 2020 reached up to 93 GW, resulting in a 53% year-on-year increase. The development trend of wind turbines has gradually moved toward the large-scale and floating type (Asim et al., 2022), which has had significant impacts on the aerodynamic performance and fatigue loads of wind turbines subjected to the complex atmospheric boundary layer (ABL). Consequently, it has become very necessary to study the dynamic responses of a floating offshore wind turbine (FOWT) under a complex ABL inflow.
- Asia > China (0.47)
- North America > United States > Massachusetts (0.28)
_ To improve the reliability of a mooring system of a floating wind turbine under extreme sea conditions, a constant tension mooring system is proposed in this paper. In extreme sea conditions, when the mooring force reaches the set value, the mooring system automatically releases the weights stored on the floating platform, and the floating platform moves along the waves with a basically constant mooring force. Through coupled time-domain simulations, the dynamic responses of the 5-MW-CSC, a semisubmersible wind turbine developed at the Centre for Ships and Ocean Structures with a constant tension mooring system, were studied under the extreme conditions with 50-year return period. Introduction Offshore floating wind power is maturing and has significantly reduced costs over the past few years. Compared with fixed offshore wind power, floating wind power is still in the stage of small-scale development. With the rapid maturity of technology and the continuous emergence of demonstration projects, it is expected to realize large-scale commercial development by 2030. According to the prediction of the European Wind Energy Association (now WindEurope), the global installed capacity of floating wind power will reach 15 GW by the end of 2030 (Corbetta et al., 2015). WindEurope conservatively estimates that the cost of floating units will decrease by 38% by 2050 (WindEurope Floating Wind Task Force, 2017). At that time, 150 GW of offshore floating wind power will be developed in Europe, which means that one-third of offshore wind power will be floating wind power in deep sea.
- Europe (1.00)
- North America > United States (0.47)
- Asia > China > Guangdong Province (0.28)
_ The seakeeping of a ship is estimated precisely at design time. However, computing the performance comprehensively under all operating conditions is time-consuming. Therefore, it is effective to estimate the performance using numerical calculations and measurements in actual seas. In this paper, a self-organizing state–space model is realized based on a three-degrees-of-freedom motion equation. The state variables and parameters of the model can be estimated simultaneously. The self-organizing state–space model is updated via measurement data in real time to predict the actual phenomena by applying the ensemble Kalman filter with a Monte Carlo approximation. As a result, the prediction capability of ship motion improves, and the ship’s added mass and damping coefficients are evaluated directly through the filtering step. This paper reports on validations of the proposed method using experimental data in tank tests. Introduction In recent years, the analysis of onboard monitoring data has been attractive to researchers evaluating full-scale ship performance in actual seas (Minoura et al., 2019). This tendency depends largely on the Energy Efficiency Design Index (EEDI) regulation introduced by the International Maritime Organization (IMO) to reduce greenhouse gas (GHG) emissions from ships in operation. It is necessary to use new fuels, such as hydrogen and ammonia, that do not emit GHG and to develop new systems that can control the production and consumption of propulsion energy to achieve zero emissions. However, these operational costs are high. Therefore, not only hull forms and devices for energy-saving but also efficient operations with control of ship motion are required to improve fuel efficiency while ensuring safety. Short-term predictions of a ship’s responses in actual seas are important since ocean-going ships often sail in severe sea states. However, the added mass and damping coefficients of a ship vary, depending on operating conditions such as loading, and it is difficult to calculate the performance comprehensively under all conditions. Therefore, it is significant to establish a method to accurately evaluate the seakeeping of a full-scale ship in actual seas by analyzing the measurement data. For example, sequentially understanding the added mass and damping coefficients of a full-scale ship through measurement data is useful for the support of ship operation in real time. Also, if all hydrodynamic force coefficients can be identified by the analysis of measurement data of ship motion in irregular waves, the time required for conventional towing tank test can be reduced.
- Transportation > Marine (1.00)
- Transportation > Freight & Logistics Services > Shipping (0.35)
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
- Data Science & Engineering Analytics > Information Management and Systems > Artificial intelligence (0.91)
- Health, Safety, Environment & Sustainability > Environment > Air emissions (0.88)
_ The springing response of a tension-leg-platform wind turbine (TLPWT) excited by the third-harmonic force of an extreme regular wave is investigated using an integrated (aero-hydro-mooring) numerical model developed and presented in this paper. The numerical model comprises a hybrid hydrodynamic model, which employs fully nonlinear potential theory for wave kinematic prediction and non-diffracting potential theory for wave force prediction, to simulate extreme wave and predict associated wave forces accurately and efficiently. Numerical simulations are carried out for the interaction of a floating TLPWT with waves. The focus is on the TLPWT motions, principally excited by the higher-order harmonic wave forces. In particular, the springing response at the triple wave frequency of a regular wave is investigated, together with the wind turbine response and the tensions in the mooring lines. Introduction As per the IEC TS 61400-3-2 (2019) standard, floating wind turbines are designed to survive 50 years of environmental conditions during their 25 years of service life. For a tension-leg- platform wind turbine (TLPWT), operational and extreme wave loads can induce high-frequency resonance and transient responses, e.g., springing and ringing, which may greatly amplify its global responses and reduce its fatigue lifetime. As TLPWTs are designed to avoid resonance by linear force at the dominant frequency fwa of the wave spectrum, they are likely to get excited by the nonlinear force at nfwa, where n = 2, 3,… It is then evident that the springing is principally due to the higher harmonic component of the nonlinear wave force. Thus, in the present work, we shall consider the springing behavior of a TLPWT excited by the higher-order harmonic force of a regular wave. Although the regular wave may not truly reflect the stochastic nature of the real sea state, the results obtained can provide some insight into the springing behavior of the TLPWT.
- Europe > United Kingdom (0.28)
- Europe > Norway (0.28)
Modeling the Influence of Soil-Structure-Interaction on Seismic Response of Jacket Substructure for the DTU 10MW Offshore Wind Turbine
Fan, Ting-Yu (Institute of Nuclear Energy Research, Taoyuan City) | Lin, Chin-Yu (Institute of Nuclear Energy Research, Taoyuan City) | Huang, Chin-Cheng (Institute of Nuclear Energy Research, Taoyuan City)
Abstract This paper is intended to study the influence of soil–structure interaction on the seismic response of jacket substructure for the Technical University of Denmark 10-MW reference wind turbine on the west coast of Taiwan. Since Taiwan is located in the circum-Pacific seismic belt, there is significant interest in assessing the behavior of a wind turbine subjected to seismic loading. Based on the flexible volume method, a finite element model was employed to quantify the contribution of foundation damping to overall damping of offshore wind turbines. The results show that foundation damping was estimated to contribute 1.28%–1.50% of critical damping to total offshore wind turbine damping. The soil–structure interaction effects have significant influence on seismic responses. Introduction Wind power is regarded as one of the most promising renewable energy resources, which provides an essential contribution to a clean, robust, and diversified energy portfolio. Advanced technologies and supply chain maturity make offshore wind power an increasingly viable option for renewable energy, as well. Offshore wind power has achieved rapid growth over the past several years. According to WindEurope’s technical reports, the European Union (EU) renewable policies aim to achieve at least 27% of the final energy consumption from renewable energy sources by the end of 2030. Therefore, a total of 323 GW of cumulative wind energy projects are planned to be installed in the EU by 2030. That would be more than double the capacity installed at the end of 2016 (160 GW) (European Wind Energy Association, 2017). With the aim of reducing the levelized cost of energy (LCOE), wind turbines with larger rated power capacities have significantly increased to more than 9.5 MW in recent years. However, a number of challenges remain to be resolved. Among the challenges are: 1) the potential resonance problem on larger wind turbines (Von Borstel, 2013), 2) site selection, 3) proper substructure type selection, and others. Although the west coast of Taiwan is rich in offshore wind resources (Chang et al., 2015), the support structures for offshore wind turbines (OWTs) could be subjected to different environmental loads through their design life, such as earthquakes, typhoons, extreme waves, and tsunamis. Consequently, Taiwan’s extreme environmental conditions play crucial roles for the installation and structural integrity of OWTs.
- Europe (1.00)
- Asia > Taiwan (0.98)
- North America > United States > California (0.46)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.61)
- Geology > Geological Subdiscipline > Geomechanics (0.48)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
- Health, Safety, Environment & Sustainability > Environment (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (1.00)
Efficient Properties of Different Types of Wave Energy Converters Placed in Front of a Vertical Breakwater
Konispoliatis, Dimitrios N. (National Technical University of Athens) | Mavrakos, Anargyros S. (National Technical University of Athens) | Mavrakos, Spyridon A. (National Technical University of Athens)
Abstract The present paper aims at investigating the efficiency of a cylindrical WEC placed in front of a vertical, surface-piercing breakwater of infinite length. A theoretical model is presented based on the linearized velocity potential, the image theory, and the matched axisymmetric eigenfunction expansion formulations. The WECs under examination are the heaving absorber and the oscillating water column device. From the present analysis, it is demonstrated that the absorbed wave power by the examined WECs in front of a vertical wall is strongly affected by the geometrical parameters of the converters and their mechanical components; thus, they should be properly considered when designing the WEC-breakwater system to increase its wave power efficiency. Introduction Ocean waves have vast energy potential. However, harnessing wave power is more complex than the process of converting other renewable energy sources like wind or solar into electricity. Wave conditions (i.e., wave heights and wave frequencies) can vary wildly over time and from one installation location to another. As a result, the wave energy sector is focusing on developing efficient solutions, which at the same time will be capable of withstanding the demanding environmental conditions in the installation areas. In this respect, various wave energy converters (WECs) characterized by different working principles, i.e., modes of power absorption, have been proposed and designed (Falnes, 2007; McCormick, 1981; Pelc and Fujita, 2002) with the oscillating water column devices (OWCs) and the heaving WECs (heaving absorbers) representing the most advanced device types (Magagna et al., 2016). To increase the efficiency of a WEC, several parameters have been examined up to date, namely (a) the optimization of the WEC’s geometrical characteristics, in the scope of harnessing maximum wave energy at the installation location; (b) the optimization of the WEC’s characteristics with respect to their mechanical components, to withstand the demanding environmental conditions, as well as to reduce the energy losses associated with the transformation of the wave power into electricity; and (c) the installation of WECs close to other near- or onshore maritime structures, such as a breakwater, a harbor, or a pier, so as to use already existent infrastructures (electric grid, etc.), reducing in parallel the WECs’ environmental impact (Konispoliatis et al., 2020; Mustapa et al., 2017).
Numerical Study on the Motion and Added Resistance of a Trimaran in Stern Waves Using a Hybrid Method
Gong, Jiaye (Shanghai Maritime University, Shanghai) | Li, Yunbo (Shanghai Maritime University, Shanghai) | Yan, Shiqiang (City, University of London) | Ma, Qingwei (City, University of London) | Hong, Zhichao (Jiangsu University of Science and Technology, Zhenjiang)
This paper presents a one-way coupling method based on the open-source computational fluid dynamics tool OpenFOAM. This hybrid method that couples the fully nonlinear potential theory (FNPT)-based quasi-arbitrary Lagrangian-Eulerian finite element method (QALE-FEM) with the viscous flow method is applied to simulate the forward movement and motion of a trimaran in stern waves. With this hybrid method and the corresponding solver qaleFOAM, the linear and nonlinear incident waves are generated by the external domain of FNPT-based QALE-FEM. The waves propagate to the internal domain by a transition zone. The interaction between the wave and trimaran model in the internal domain is simulated by the viscous flow method. The validation of the wave generation is carried out first. Then, the motion of the trimaran model in stern waves is simulated. Finally, by changing the forward speed and the wave parameters, the amplitude and time history are obtained to analyze the trimaran’s motion characteristics in stern waves. Introduction The motion and added resistance in waves play an important role in the design and performance optimization of a ship, a role that has been widely investigated in recent years (Yu et al., 2017; Chen et al., 2018; Diao et al., 2019; Begovic et al., 2020; Tang et al., 2021). Furthermore, the hydrodynamics of a trimaran, as a kind of high-performance ship, has been studied by both numerical methods and tank tests (Tang et al., 2017; Chen et al., 2018; Zong et al., 2019a). Therefore, the characteristics of a trimaran’s motion and added resistance in waves have attracted more and more attention in past decades. Furthermore, the trimaran has the advantages of low resistance in calm water, a large deck area, and good transversal stability. Hence, the study of the seakeeping performance of a trimaran in waves plays an essential role in the further application of a trimaran.
- Europe (0.68)
- North America > United States (0.46)
- Asia > China (0.29)
- Reservoir Description and Dynamics (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems (0.93)
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (0.46)
- Data Science & Engineering Analytics > Information Management and Systems > Artificial intelligence (0.46)