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CONTENTS
Volume 27, Number 1, July 2018
 

Abstract
In this study, the enhancement of the conventional Savonius wind rotor performance with extension plate has been investigated experimentally and numerically. Experimental models used in the study have been produced with 3D (three dimensional) printing, which is one of the rapid prototyping techniques. Experiments of produced Savonius wind rotor models have been carried out in a wind tunnel. CFD (Computational Fluid Dynamics) analyses have been performed under the same experimental conditions to ensure that experiments and numerical analyses are supported to each other. An additional extension plate has been used in order to enhance the performance of the conventional Savonius wind rotor with a gap distance between blades. It can be called modified Savonius rotor or Savonius rotor with built-in extension plate. Thus, the performance of the rotor has been enhanced without using additional equipment other than the rotor itself. Numerical and experimental analyses of Savonius wind rotor models with extension plate have been carried out under predetermined boundary conditions. It has been found that the power coefficient of the modified Savonius rotor is increased about 15% according to the conventional Savonius rotor.

Key Words
Savonius; wind rotor; 3D printer; performance; extension plate

Address
Burcin Deda Altan and Gurkan Altan: Faculty of Engineering, Department of Mechanical Engineering, Pamukkale University, Kinikli 20070 Denizli, Turkey
Volkan Kovan : Faculty of Engineering, Department of Mechanical Engineering, Akdeniz University, Antalya, Turkey

Abstract
The straight-cone steel cooling tower is a novel type of structure, which has a distinct aerodynamic distribution on the internal surface of the tower cylinder compared with conventional hyperbolic concrete cooling towers. Especially in the extreme weather conditions of strong wind and heavy rain, heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind, but existing studies mainly focus on the impact effect brought by wind-driven rain to structure surface. In addition, for the indirect air cooled cooling tower, different additional ventilation rate of shutters produces a considerable interference to air movement inside the tower and also to the action mechanism of loads. To solve the problem, a straight-cone steel cooling tower standing 189 m high and currently being constructed is taken as the research object in this study. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed with continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind sped and rainfall intensity on flow field mechanism, the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower cylinder is analyzed. On this basis, the internal pressures of the cooling tower under the most unfavorable working condition are compared between four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the 3D effect of equivalent internal pressure coefficient is the most significant when considering two-way coupling between wind and rain. Additional load imposed by raindrops on the internal surface of the tower accounts for an extremely small proportion of total wind load, the maximum being only 0.245%. This occurs under the combination of 20 m/s wind velocity and 200 mm/h rainfall intensity. Ventilation rate of shutters not only changes the air movement inside the tower, but also affects the accumulated amount and distribution of raindrops on the internal surface.

Key Words
straight-cone; steel cooling tower; two-way coupling between wind and rain; ventilation rate of shutters; aerodynamic force on internal surface; action mechanism; parameter analysis

Address
S.T. Ke, L.Y. Du and Q. Yang:Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Road, Nanjing 210016, China
Y.J. Ge: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
H. Wang: School of Civil Engineering, Southeast University, 2 Sipailou Road, Nanjing 210096, China
Y. Tamura: Center of Wind Engineering Research, Tokyo Polytechnic University, 1583 Iiyama, Atsugi, Kanagawa 243-0297, Japan


Abstract
To investigate the characteristics of the combined wind field produced by the natural wind field and the train-induced wind field on the bridge, the aerodynamic models of train and bridge are established and the overset mesh technology is applied to simulate the movement of high-speed train. Based on ten study cases with various crosswind velocities of 0~20 m/s and train speeds of 200~350 km/h, the distributions of combined wind velocities at monitoring points around the train and the pressure on the car-body surface are analyzed. Meanwhile, the difference between the train-induced wind fields calculated by static train model and moving train model is compared. The results show that under non-crosswind condition, the train-induced wind velocity increases with the train speed while decreases with the distance to the train. Under the crosswind, the combined wind velocity is mainly controlled by the crosswind, and slightly increases with the train speed. In the combined wind field, the peak pressure zone on the headstock surface moves from the nose area to the windward side with the increase of wind velocity. The moving train model is more applicable in analyzing the train induced wind field.

Key Words
high-speed train; train-induced wind; crosswind; combined wind field; numerical analysis; overset mesh

Address
Yujing Wang: School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
He Xia, Weiwei Guo and Nan Zhang: School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China;
Beijing Key Laboratory of Structural Wind Engineering and Urban Wind Environment, Beijing 100044, China
Shaoqin Wang: School of Science, Beijing University of Civil Engineering and Architecture, Beijing 100044, China

Abstract
Concentrated Solar Photovoltaic (CPV) is a promising alternative to conventional solar structures. These solar tracking structures need to be optimized to be competitive against other types of energy production. In particular, the selection of the structural parameters needs to be optimized with regards to the dynamic wind response. This study aims to evaluate the effect of the main structural parameters, as selected in the preliminary design phase, on the wind response and then on the weight of the steel support structure. A parametric study has been performed where parameters influencing dynamic wind response are varied. The study is performed using a semi-deterministic time-domain wind analysis method. Unsteady aerodynamic model is applied for the shape of the CPV structure collector at different configurations in conjunction with a consistent mass-spring-damper model with the corresponding degrees of freedom to describe the dynamic response of the system. It is shown that, unlike the static response analysis, the variation of the peak wind response with many structural parameters is highly nonlinear because of the dynamic wind action. A steel structural optimization process reveals that close attention to structural and site wind parameters could lead to optimal design of CPV steel support structure.

Key Words
solar concentrator structure; finite element analysis; wind simulation; dynamic effect; wind load optimization

Address
Bassem Kaabia, Sébastien Langlois and Sébastien Maheux: Department of Civil Engineering, Université de Sherbrooke, 2500 boul. de l\'Université, Sherbrooke, QC, Canada, J1K2R1

Abstract
In this paper, geometrically non-linear analysis of a functionally graded simple supported beam is investigated with porosity effect. The material properties of the beam are assumed to vary though height direction according to a prescribed power-law distributions with different porosity models. In the nonlinear kinematic model of the beam, the total Lagrangian approach is used within Timoshenko beam theory. In the solution of the nonlinear problem, the finite element method is used in conjunction with the Newton-Raphson method. In the study, the effects of material distribution such as power-law exponents, porosity coefficients, nonlinear effects on the static behavior of functionally graded beams are examined and discussed with porosity effects. The difference between the geometrically linear and nonlinear analysis of functionally graded porous beam is investigated in detail. Also, the effects of the different porosity models on the functionally graded beams are investigated both linear and nonlinear cases.

Key Words
geometrically nonlinear analysis; functionally graded material; porosity; total Lagragian; finite element method

Address
Şeref D. Akbaş: Department of Civil Engineering, Bursa Technical University, Yildirim Campus, Yildirim, Bursa 16330, Turkey


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