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CONTENTS
Volume 28, Number 3, March 2019
 

Abstract
In this study, we have focused on commonly used 14 different small wind turbine airfoils (A18, BW3, Clark Y, E387, FX77, NACA 2414, RG 15, S822, S823, S6062, S7012, SD6060, SD7032, SD7062). The main purpose of the study is to determine the lift, drag and lift/drag coefficients of these airfoils with numerical analysis and to verify 2 best airfoil\'s results with experimental analysis. Airfoils were determined from past studies on small wind turbines. Numerical analyzes of the airfoils were done with Ansys Fluent fluid dynamics program. Experimental analyzes were done at wind tunnel in Erciyes University, Turkey. Lift and drag coefficients of these airfoils were determined for 50,000-100,000-200,000 Reynolds numbers.

Key Words
wind turbine; airfoil; lift, drag

Address
Cevahir Tarhan and İlker Yilmaz: Erciyes University, Faculty of Aeronautics and Astronautics, Kayseri, 38280, Turkey

Abstract
This paper presents a novel test method for the galloping of iced conductor using wind generated by a moving vehicle which can produce relative wind field. The theoretical formula of transiting test is developed based on theoretical derivation and field test. The test devices of transiting test method for aerodynamic coefficient and galloping of an iced conductor are designed and assembled, respectively. The test method is then used to measure the aerodynamic coefficient and galloping of iced conductor which has been performed in the relevant literatures. Experimental results reveal that the theoretical formula of transiting test method for aerodynamic coefficient of iced conductor is accurate. Moreover, the driving wind speed measured by Pitot tube pressure sensors, as well as the lift and drag forces measured by dynamometer in the transiting test are stable and accurate. Vehicle vibration slightly influences the aerodynamic coefficients of the transiting test during driving in ideal conditions. Results of transiting test show that the tendencies of the aerodynamic coefficient curve are generally consistent with those of the wind tunnel tests in related studies. Meanwhile, the galloping is fairly consistent with that obtained through the wind tunnel test in the related literature. These studies validate the feasibility and effectiveness of the transiting test method. The present study on the transiting test method provides a novel testing method for research on the wind-resistance of iced conductor.

Key Words
transiting test method; moving vehicle; iced conductor; aerodynamic characteristic; wake galloping; wind tunnel test

Address
Pan Guo, Dongwei Wang, Shengli Li, Lulu Liu and Xidong Wang: School of Civil Engineering, Zhengzhou University,
No.100 Science Avenue, Zhengzhou City, Henan Province, P.R. China. Postcode: 450001


Abstract
This paper presents a restart iterative approach for time-domain flutter analysis of long-span bridges using the commercial FE package ANSYS. This approach utilizes the recursive formats of impulse-response-function expressions for bridge\'s aeroelastic forces. Nonlinear dynamic equilibrium equations are iteratively solved by using the restart technique in ANSYS, which enable the equilibrium state of system to get back to last moment absolutely during iterations. The condition for the onset of flutter instability becomes that, at a certain wind velocity, the amplitude of vibration is invariant with time. A long-span suspension bridge was taken as a numerical example to verify the applicability and accuracy of the proposed method by comparing calculated results with wind tunnel tests. The proposed method enables the bridge designers and engineering practitioners to carry out time-domain flutter analysis of bridges in commercial FE package ANSYS.

Key Words
long-span bridge; flutter; time domain; aeroelastic force; finite element (FE) model; ANSYS

Address
Wen-ming Zhang and Kai-rui Qian: Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing 211189, P.R. China
Lian Xie: T. Y. Lin International Engineering Consulting (China) Co., Ltd, Chongqing 401121, P.R. China
Yao-jun Ge: State Key Lab for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, P.R. China

Abstract
Light-frame wood structures have the ability to carry gravity loads. However, their performance during severe wind storms has indicated weakness with respect to resisting uplift wind loads exerted on the roofs of residential houses. A common failure mode observed during almost all main hurricane events initiates at the roof-to-wall connections (RTWCs). The toe-nail connections typically used at these locations are weak with regard to resisting uplift loading. This issue has been investigated at the Insurance Research Lab for Better Homes, where full-scale testing was conducted of a house under appropriate simulated uplift wind loads. This paper describes the detailed and sophisticated numerical simulation performed for this full-scale test, following which the numerical predictions were compared with the experimental results. In the numerical model, the nonlinear behavior is concentrated at the RTWCs, which is simulated with the use of a multi-linear plastic element. The analysis was conducted on four sets of uplift loads applied during the physical testing: 30 m/s increased by 5 m/s increments to 45 m/s. At this level of uplift loading, the connections exhibited inelastic behavior. A comparison with the experimental results revealed the ability of the sophisticated numerical model to predict the nonlinear response of the roof under wind uplift loads that vary both in time and space. A further component of the study was an evaluation of the load sharing among the trusses under realistic, uniform, and code pressures. Both the numerical model and the tributary area method were used for the load-sharing calculations.

Key Words
finite element method; wind load; roof-to-wall connections; wood structures; wind speed

Address
Adnan F. Enajar and Ashraf A. El Damatty: Department of Civil and Environmental Engineering, Faculty of Engineering, The University of Western Ontario, London Ontario Canada
Ryan B. Jacklin: Tacoma Engineers, Guelph Ontario Canada

Abstract
In this paper, the aerodynamic analysis of a vertical axis wind turbine was carried out by CFD approach to optimize the turbine performance. To perform numerical simulation, SST-Transition turbulence model was used, which demonstrated more precise results compared to non-transition models. A parametric study was conducted to optimize the VAWT performance based on the selected model. The investigation of pitch angle changes showed that the highest power produced by the turbine occurs at 2 angle. Considering the effect of the rotor\' s arm junction to the airfoil showed that by increasing the distance of the junction from the edge of the airfoil from 25 cm to 40 cm, the power of the turbine increases by 60%. However, further increase in this distance results in power decrease. Based on the proposed numerical model, a case study was conducted to consider the installation of four VAWTs in the southwest corner of the medical science building at TMU campus with a height of 42m. The results of the simulation showed that 8.27 MWh energy is obtainable annually.

Key Words
vertical axis wind turbine; CFD simulation; turbulence models; case study

Address
Seyed Kourosh Mirfazli and Ali Jafarian Dehkordi: School of Mechanical Engineering, Tarbiat Modares University, Jalal Ale Ahmad Highway, Tehran, Iran
Mohammad Hossein Giahi: School on Mechanical Engineering, Saskatchewan University, 69 Campus Dr, Saskatoon, SK, Canada


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