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CONTENTS
Volume 20, Number 1, January 2015
 

Abstract
This study applied long-term wind speed data from Penghu and Dongjidao weather stations to simulate the wind energy production for eight onshore and one offshore wind farms at Penghu Island, Taiwan by a commercial software package, Wind Atlas Application Program (WAsP). In addition, the RET Screen software suite was also applied to analyze economic characteristics of these nine wind farms (WFs). The results show that the capacity factors (CFs) of the nine wind farms mentioned above are in the range of 44.5% to 49.1%. In addition, utilizing 1.8-MW wind turbines (WTs) for all onshore WFs was the most feasible selection among the four potential types of WTs (600, 900, 1,800 and 3,600 kW) considered. 3-MW WTs selected for the offshore WF can produce the most wind energy and the smallest wake loss among the three possible types of WTs (1, 2 and 3MW). As a consequence of implementing these WFs, the emission of about 680,977 tons carbon dioxide (tCO2) into the local atmosphere in Penghu Island annually could be avoided. Finally, based on the payback periods achieved, the order of implementation of the considered WFs can be identified more clearly. Longmen WF should be the first priority, and the next one should be SiyuWF and so on. Besides, this study provides much useful information for WF planning on Penghu Island.

Key Words
wind energy; wind turbine; wind farm; carbon dioxide; Penghu Island

Address
Tsai-Hsiang Chen and Van-Tan Tran: Department of Electrical Engineering, National Taiwan University of Science and Technology No. 43, Section 4, Keelung Road, Taipei (10607), Taiwan R.O.C.


Abstract
Characterization of wind flows over a complex terrain, especially mountain-gorge terrain (referred to as the very complex terrain with rolling mountains and deep narrow gorges), is an important issue for design and operation of long-span bridges constructed in this area. In both wind tunnel testing and numerical simulation, a transition section is often used to connect the wind tunnel floor or computational domain bottom and the boundary top of the terrain model in order to generate a smooth flow transition over the edge of the terrain model. Although the transition section plays an important role in simulation of wind field over complex terrain, an appropriate shape needs investigation. In this study, two principles for selecting an appropriate shape of boundary transition section were proposed, and a theoretical curve serving for the mountain-gorge terrain model was derived based on potential flow theory around a circular cylinder. Then a two-dimensional (2-D) simulation was used to compare the flow transition performance between the proposed curved transition section and the traditional ramp transition section in a wind tunnel. Furthermore, the wind velocity field induced by the curved transition section with an equivalent slope of 30 was investigated in detail, and a parameter called the \'velocity stability factor\' was defined; an analytical model for predicting the velocity stability factor was also proposed. The results show that the proposed curved transition section has a better flow transition performance compared with the traditional ramp transition section. The proposed analytical model can also adequately predict the velocity stability factor of the wind field.

Key Words
mountain-gorge terrain; boundary transition section; wind characteristics; potential flow; wind tunnel test

Address
Peng Hu:School of Civil Engineering and Architecture, Changsha University of Science & Technology,
Changsha, Hunan 410114, China
Yongle Li, Guoqing Huang and Haili Liao: School of Civil Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
Rui Kang: Department of Civil Engineering, Southwest Jiaotong University, Emei, Sichuan 614202, China

Abstract
As wind flows around a sharp-edged body, the resulting separated flow becomes complicated, with multiple separations and reattachments as well as vortex recirculation. This widespread and unpredictable phenomenon has long been studied academically as well as in engineering applications. In this study, the flow characteristics around rectangular prisms with five different aspect ratios were determined through wind tunnel experiments and a detached eddy simulation, that placed the objects in a simulated deep turbulent boundary layer at Re=4.6 X 10 ^4. A series of rectangular prisms with the same height (h = 80 mm), different longitudinal lengths (l = 0.5h, h, and 2h), or different transverse widths (w = 0.5h, h, and 2h) were employed to observe the effects of the aspect ratio. Furthermore, five wind directions (0, 10, 20, 30, and 45) were selected to observe the effects of the wind direction. The simulated results of the surface pressure were compared to the wind tunnel experiment results and the existing results of previous papers. The vortex and spectrum were also analyzed to determine the detailed flow structure around the body. The paper also highlights the pressure distribution around the rectangular prisms with respect to the different aspect ratios. With an increasing transverse width, the surface suction pressure on the top and side surfaces becomes stronger. In addition, depending on the wind direction, the pressure coefficient experiences a large variation and can even change from a negative to a positive value on the side surface of the cube model.

Key Words
rectangular prisms; flow characteristics; aspect ratio; wind direction; wind-tunnel test; detached-eddy simulation

Address
Hee Chang Lim: School of Mechanical Engineering, Pusan National University, San 30, Jangjeon-Dong, Geumjeong-Gu, Busan, 609-735, South Korea
Masaaki Ohba: Department of Architecture, Faculty of Engineering, Tokyo Polytechnic University, Atsugi,
Kanagawa, 243-02/3, Japan


Abstract
A coupled model system for Wind Resource Assessment (WRA) was studied. Using a mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, global-scale data were downscaled to the inner nested grid scale (typically a few kilometers), and then through the coupling Computational Fluid Dynamics (CFD) mode, FLUENT. High-resolution results (50 m in the horizontal direction; 10 m in the vertical direction below 150 m) of the wind speed distribution data and ultimately refined wind farm information, were obtained. The refined WRF/FLUENT system was then applied to assess the wind resource over complex terrain in the northern Poyang Lake region. The results showed that the approach is viable for the assessment of wind energy.

Key Words
wind resource assessment; complex terrain; refined numerical simulation; WRF; FLUENT

Address
Xue-Ling Cheng, Jun Li and Fei Hu: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, P.R. China
Jingjing Xu: International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, P.R. China
Rong Zhu: Public Weather Service Center China Meteorological Administration, Beijing 100081, P.R. China

Abstract
This work is focused on a parametric numerical study of the barrier\'s bar inclination shelter effect in crosswind scenario. The parametric study combines mesh morphing and design of experiments in automated manner. Radial Basis Functions (RBF) method is used for mesh morphing and Ansys Workbench is used as an automation platform. Wind barrier consists of five bars where each bar angle is parameterized. Design points are defined using the design of experiments (DOE) technique to accurately represent the entire design space. Three-dimensional RANS numerical simulation was utilized with commercial software Ansys Fluent 14.5. In addition to the numerical study, experimental measurement of the aerodynamic forces acting on a vehicle is performed in order to define the critical wind disturbance scenario. The wind barrier optimization method combines morphing, an advanced CFD solver, high performance computing, and process automaters. The goal is to present a parametric aerodynamic simulation methodology for the wind barrier shelter that integrates accuracy and an extended design space in an automated manner. In addition, goal driven optimization is conducted for the most influential parameters for the wind barrier shelter.

Key Words
parametric numerical simulation; wind barrier shelter; RBF morph; CFD simulation; mesh morphing

Address
Marijo Telenta, Ivan Prebil and Jožef Duhovnik: Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia
Milan Batista: Faculty of Maritime studies and Transport, University of Ljubljana, Pot pomorščakov, 6320 Portorož, Slovenia
M.E. Biancolini: Department of Enterprise Engineering, University of Rome \"Tor Vergata\", Via Politecnico 1, 00133 Roma, Italy

Abstract
Wind effects on roofs are usually considered by equivalent static wind loads based on the equivalence of displacement or internal force for structural design. However, for large-span spatial structures that are prone to dynamic instability under strong winds, such equivalent static wind loads may be inapplicable. The dynamic stability of spatial structures under unsteady wind forces is therefore studied in this paper. A new concept and its corresponding method for dynamic instability-aimed equivalent static wind loads are proposed for structural engineers. The method is applied in the dynamic stability design of an actual double-layer cylindrical reticulated shell under wind actions. An experimental–numerical method is adopted to study the dynamic stability of the shell and the dynamic instability originating from critical wind velocity. The dynamic instability-aimed equivalent static wind loads of the shell are obtained.

Key Words
spatial structures; structural instability; Budiansky–Roth criterion; dynamic instability-aimed equivalent static wind loads; application

Address
Ming Gu: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji Univeristy, 1239 Siping Rd., Yangpu District, Shanghai, P.R. China
Youqin Huang:2Engineering Technology Research and Development Center for Structural safety and Health Monitoring in Guangdong Province, Guangzhou University, 230 West Wai\'huan RD., Higher Education Mega Center, Guangzhou, P.R. China


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