应用DES(Detached-Eddy Simulation)方法数值模拟了3种不同失速类型的翼型的升力特性.DES方法结合了RANS(Reynolds-averaged Navier-Stokes)和LES(Large Eddy Simulation approaches)的优点.基于Spalart-Allmaras湍流模型,在近壁面DES体现为RANS模型的特点而在远离物面处又具有LES的亚格子模型的特性.对此模型使用了LU-SGS隐式格式求解.通过和实验结果对比,显示这种方法可以有效地预测翼型的失速特性.

Detached—Eddy Simulation方法模拟不同类型翼型的失速特性

Reliability of multi-purpose offshore-facilities: Present status and future direction in Australia

Wind energy industry is expanded to offshore and deep water sites, primarily due to the stronger and more consistent wind fields. Floating offshore wind turbine (FOWT) concepts involve new engineering and scientific challenges. A combination of waves, current, and wind loads impact the structures. Often under extreme cases, and sometimes in operational conditions, magnitudes of these loads are comparable with each other. The loads and responses may be large, and simultaneous consideration of the combined environmental loads on the response of the structure is essential. Moreover, FOWTs are often large structures and the load frequencies are comparable to the structural frequencies. This requires a fluid–structure–fluid elastic analysis which adds to the complexity of the problem. Here, we present a critical review of the existing approaches that are used to (i) estimate the hydrodynamic and aerodynamic loads on FOWTs, and (ii) to determine the structures’ motion and elastic responses due to the combined loads. Particular attention is given to the coupling of the loads and responses, assumptions made under each of the existing solution approaches, their limitations, and restrictions, where possible, suggestions are provided on areas where further studies are required.

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On motion analysis and elastic response of floating offshore wind turbines

Floating offshore wind turbines (FOWTs) experience fluctuations in their platforms, owing to the various wave and wind conditions. These fluctuations not only decrease the output of the wind power generation system, but also increase the fatigue load of the structure and various equipment mounted on it. Therefore, when designing FOWTs, efficient performance with respect to waves and other external conditions must be ensured. In this study, a model test was performed with a 10 MW floating offshore wind turbine. The model test was performed by scaling down a 10 MW FOWT model that was designed with reference to a 5 MW wind turbine and a semisubmersible platform by the National Renewable Energy Laboratory and the DeepCwind project. A scale ratio of 1:90 was used for the model test. The depth of the East Sea was considered as 144 m and, to match the water depth with the geometric similarity of mooring lines, mooring tables were installed. The load cases used in the model test are combined environmental conditions, which are combined uniform wind, regular waves and uniform current. Especially, Model tests with regular waves are especially necessary, because irregular waves are superpositions of regular waves with various periods. Therefore, this study aimed to understand the characteristics of the FOWTs caused by regular waves of various periods. Furthermore, in this model test, the effect of current was investigated using the current data of the East Sea. The results obtained through the model tests were the response amplitude operator (RAO) and the effective RAO for a six degrees-of-freedom motion. The results obtained from the model tests were compared with those obtained using the numerical simulation. The purpose of this paper is to predict the response of the entire system observed in model tests through simulation.

Experimental and Numerical Analysis of a 10 MW Floating Offshore Wind Turbine in Regular Waves

Green Energy and Technology : Floating Offshore Wind Energy : The Next Generation of Wind Energy


 Most of the existing floating offshore wind turbines (FOWT), whether in concept or built, host a single turbine. Structures that can host multiple turbines have received attention in recent years, mainly with the aim of reducing the overall cost of energy production and maintenance. A concept challenge of placing multiple wind turbines on a single floating platform is that under variable wind directions, the leading turbines may block the wind against the trailing turbines. In this work, concept design of a wind-tracing floating structure accommodating three wind turbines is presented. The triangular-shapefloating platform is made of pre-stressed concrete, and the turbines are located on the corners. The floating structure uses a single-point mooring system which allows for the entire structure to rotate in response to the change of wind direction. Due to the particular configuration of the floating structure, it is essential to consider the wind, wave and current loads, along with the response of the structure, simultaneously. Response of the FOWT to simultaneous environmental loads from different directions is studied by use of the constant panel approach of the Green function method, subject to constant wind loads on the turbines and linear mooring loads. We also consider the elasticity of the structure by use of finite element analysis, coupled with the hydro- and aero-dynamic loads and responses.

Concept Design and Analysis of Wind-Tracing Floating Offshore Wind Turbines


 This study is concerned with motion analysis and hydroelastic response of a floating offshore wind turbine to wave loads. The novel floating structure, made of prestressed concrete, is designed to support multiple wind turbines, and it rotates according to the environmental loads to face the incoming wind. The floating structure is attached to a mooring line that allows the rotation of the structure in response to the environmental loads. The floating structure is an equilateral triangular platform. The wind turbines are located at the vertices. Due to the dimensional characteristics of the structure, elasticity of the floating platform plays an important role in its dynamics. While the dynamic response of the structure is driven by both aerodynamic and hydrodynamic loads, this study focuses on the motion and elastic response of the novel floating structure to the hydrodynamic loads only. The three dimensional hydrodynamic loads on the floating structure are obtained by use of the constant panel approach of the Green function method, subject to linear mooring loads. A finite element analysis is carried out for the calculation of the elastic response of the structure. Computations of the integrated linear structure-fluid-structure interaction problem are performed in frequency domain using HYDRAN, a computer program written for the linear dynamic analysis of rigid and flexible bodies. Results presented here include the response amplitude operators of both the rigid and flexible bodies to incoming waves of various frequencies and directions. Also presented are the wave-induced stresses on the floating body, and the elastic deformations.

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Azin Lamei

Papers

On motion analysis and elastic response of floating offshore wind turbines

Concept Design and Analysis of Wind-Tracing Floating Offshore Wind Turbines

On Motion and Hydroelastic Analysis of a Floating Offshore Wind Turbine