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CONTENTS
Volume 32, Number 6, June 2021
 


Abstract
In the present study, the well-adopted practice of minor aerodynamic modifications (chamfered corner and rounded corner) has been introduced on widely used irregular U plan shaped tall building to minimize the wind induced responses and also to give a good aesthetics. The necessary design inputs for a wind resistance design such as force coefficient and pressure coefficients have been well explored and illustrated graphically to provide a complete guideline to the designer. The randomness of wind directionality has a significant impact on tall structures, which is generally not detailed in existing design codes, is incorporated by considering wind directions ranging from 0° to 180° at an interval of 15°. Computational fluid dynamics (CFD) has been utilized to simulate wind flow using two turbulence models, i.e., k-epsilon and Shear Stress Transport. The model has been validated by comparing the results of a published research article on a U-shaped building without corner modification. The grid independence study has been done to check the reliability and accuracy of the analysis results. Since such study of wind directionality on corner modified U-shaped building is not observed in the existing literature, it constitutes the uniqueness of the present study. A significant reduction in force coefficient has been achieved by implementing modification, but the faces of those updated corners mostly been attracted by excessive pressure. This indicates the necessity of proper cladding configurations. The rounded corner buildings are turning out to be more effective when compared to the chamfered corner for reducing wind load.

Key Words
aerodynamic modifications; computational fluid dynamics; force coefficient; grid independence study; pressure coefficient; wind directionality

Address
Shanku Mandal:Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah – 711103, India

Sujit K. Dalui:Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah – 711103, India

Soumya Bhattacharjya:Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah – 711103, India

Abstract
This perusal surveys the design criteria indispensable for fences that are installed alongside the high-speed railway tracks to protect the passing high-speed rolling stock under strong side winds. Using a numerical code based on Lattice Boltzmann Method (LBM) it is attempted to initially investigate the airflow behavior behind the fences. A variety of geometries for air fences in a two-dimensional space are compared. A wind tunnel test is performed to verify the numerical results. The three-dimensional flow patterns around the German Intercity Express (ICE3) high-speed train with and without the air fences are numerically examined to be more realistic. It is found that the presence of the fences has a significant impact on decreasing the intensity of the airflow above the train. The edges on the top of the fences cause more reduction in the velocity of air flowing above the train.

Key Words
CFD; wind tunnel test; Lattice Boltzmann method; air fence; high-speed railway

Address
Masoud Mohebbi:Center of Excellence in Railway Transportation, School of Railway Engineering, Iran University of Science and Technology,Narmak, Tehran, 16846-13114, Iran

Mohammad Ali Rezvani:Center of Excellence in Railway Transportation, School of Railway Engineering, Iran University of Science and Technology,Narmak, Tehran, 16846-13114, Iran

Abstract
Refer to wind turbine airfoil wind tunnel test and consider the characteristics of wind generated by a moving vehicle, a new test method for wind turbine airfoil aerodynamic performance is proposed in this paper. Because of the relativity of motion, the vehicle will generate a relative wind field in the process of motion. Thus, the aerodynamic performance of wind turbine airfoil can be investigated using a transiting test method. In this study, a transiting test method is systematically introduced, the processing method of test data is discussed in detail, and the influence of vehicle vibration and end plate on the test results is evaluated. Three independent repeated tests are conducted, and the influence of natural wind is analyzed to eliminate the instability effect. The feasibility of the proposed test method is then verified by comparing its results with the results of wind tunnel test.

Key Words
transiting test method; wind turbine airfoil; aerodynamic performance; vehicle vibration; data processing; natural wind

Address
Shengli Li:Zhengzhou University of Industrial Technology, Zhengzhou China/School of Civil Engineering, Zhengzhou University, Zhengzhou, China/Zhengzhou Key Laboratory of Disaster Prevention and Control for Cable Structure, China

Jun Liang:School of Civil Engineering, Zhengzhou University, Zhengzhou, China

Pan Guo:School of Civil Engineering, Zhengzhou University, Zhengzhou, China

Xidong Wang:School of Civil Engineering, Zhengzhou University, Zhengzhou, China

Panjie Li:School of Civil Engineering, Zhengzhou University, Zhengzhou, China


Abstract
In this study was investigated of possibility using the recorded micro tremor data on ground level as ambient vibration input excitation data for investigation and application Experimental Modal Analysis (EMA) on the bench-scale earthquake simulator (The Quanser Shake Table) for model wind tunnel. As known EMA methods (such as EFDD, SSI and so on) are supposed to deal with the ambient responses. For this purpose, analytical and experimental modal analysis of a model wind tunnel for dynamic characteristics was evaluated. 3D Finite element model of the building was evaluated for the model wind tunnel based on the design drawing. Ambient excitation was provided by shake table from the recorded micro tremor ambient vibration data on ground level. Enhanced Frequency Domain Decomposition is used for the output only modal identification. From this study, best correlation is found between mode shapes. Natural frequencies and analytical frequencies in average (only) 2.5% are differences.

Key Words
experimental modal analysis; modal parameter; EFDD; wind tunnel

Address
Sertac Tuhta:Ondokuz Mayis University, Faculty of Engineering, Department of Civil Engineering,Atakum/Samsun, Turkey

Abstract
Wind turbine towers are sensitive to wind loads and lose efficiency when suffering excessive wind-induced vibrations. Structural control techniques such as tuned mass dampers (TMD) can be used to reduce the vibration response of the tower. However, the additional mass of this system would occupy a large amount of space within the wind turbine device, which can inconvenience installation and maintenance. An inerter is a high-efficiency two terminal mechanical element for vibration control with the characteristic of mass and damping enhancements. An ungrounded tuned mass inerter system (TMIS) –composed of a tuned mass, a tuned spring and an inerter subsystem – has potential to control wind-induced vibration efficiently. In this study, a simple design method for wind turbine towers equipped with a TMIS under wind loads is proposed, based on structural performance demand as well as control cost. A 1.5 MW wind turbine tower benchmark model is adopted to exemplify the proposed design method. Comparative analyses are conducted between a conventional TMD and the TMIS. Results show that the TMIS can achieve the same vibration control effect as the TMD while using a smaller tuned mass. A sensitivity study of the TMIS is also carried out to investigate the impact of mechanical element parameters on the performance of the vibration mitigation system. It is concluded that the optimal designed TMIS has the advantage of lightweight tuned mass over TMDs in wind-induce vibration control of wind turbine towers.

Key Words
Inerter; lightweight tuned mass; wind turbine tower; tuned mass damper; tuned mass inerter system

Address
Ruifu Zhang:State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Department of Disaster Mitigation for Structures, Tongji University, Shanghai 200092, China

Yanru Cao:State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China/ Department of Disaster Mitigation for Structures, Tongji University, Shanghai 200092, China

Kaoshan Dai:Department of Civil Engineering and Institute for Disaster Management & Reconstruction, Sichuan University, Chengdu 610065, China/ Key Laboratory of Deep Underground Science and Engineering, Ministry of Education, Sichuan University, Chengdu, China/Failure Mechanics & Engineering Disaster Prevention and Mitigation, Key Laboratory of Sichuan Province, Sichuan University, Chengdu,
China, 610065

Abstract
Wind speed is one of the most critical parameters in predicting structural performance under wind effects. In most of the current standards and codes, the design reference wind speed is usually determined by fitting a typical probability distribution model based on the historical wind speed data. However, a single distribution model is generally insufficient to reflect the regional differences in wind characteristics. Therefore, in this research, the optimal probability is selected to determine the extreme wind speed in different regions in China based on the fourth-order linear moment method (FLMM). Firstly, several probability models for estimating extreme wind speed distribution are introduced. Then, the optimal model, as well as the relative parameters, are determined by the linear moments (L-moments) method, and the one with the minimum value of the fourth-order linear moment between the probability model and the sample is taken as the optimal distribution. Finally, the extreme wind speed of each meteorological station is estimated according to the obtained optimal distribution, and the results are compared with the recorded extreme wind speed of typical metrological stations as well as that in the previous version of specification (JTG/T D60-01-2004). Compared with the traditional method that adopting a single distribution model-based wind speed estimation, the extreme wind speed obtained by the proposed method possessed higher accuracy.

Key Words
extreme wind speed; probability distribution; fourth-order linear moment method; bridge engineering; wind speed design values

Address
Cheng Xiang:Department of Bridge Engineering, Tongji University, 1239 Siping Road, Shanghai, China

Airong Chen:Department of Bridge Engineering, Tongji University, 1239 Siping Road, Shanghai, China

Qiheng Li:ShangHai Municipal Engineering Design Institute (Group) Co., Ltd., 901 Zhongshan North 2nd Road, Shanghai, China

Rujin Ma:Department of Bridge Engineering, Tongji University, 1239 Siping Road, Shanghai, China

Abstract
This paper studied the case of high-speed train running from flat ground to bridges and into/out of tunnels, with or without crosswind based on the Computational Fluid Dynamics (CFD) method. First, the flow structure was analyzed to explain the influence mechanisms of different infrastructures on the aerodynamic characteristics of the train. Then, the evolution of aerodynamic forces of the train during the entire process was analyzed and compared. Additionally, the pressure variation on the train body and the tunnel wall was examined in detail. The results showed that the pressure coefficient and the flow structure on both sides of the high-speed train were symmetrical for no crosswind case. By contrast, under crosswind, there was a tremendous and immediate change in the pressure mapping and flow structure when the train passing through the bridge-tunnel section. The influence of the ground-bridge transition on the aerodynamic forces was much smaller than that of the bridge-tunnel section. Moreover, the variation of aerodynamic load during the process of entering and exiting the bridge-tunnel sections was both significant. In addition, in the case without crosswind, the change in the pressure change in the tunnel conformed to the law of pressure wave propagation, while under crosswind, the variation in pressure was comprehensively affected by both the train and crosswind in the tunnel.

Key Words
high-speed train; bridge-tunnel transition; no wind and crosswind; aerodynamic load; flow structures

Address
Lei Zhou:Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong, China

Tanghong Liu:Key Laboratory of Traffic Safety on Track of Ministry of Education, School of Traffic & Transportation Engineering,Central South University, Changsha 410075, China

Zhengwei Chen:Key Laboratory of Traffic Safety on Track of Ministry of Education, School of Traffic & Transportation Engineering,Central South University, Changsha 410075, China/Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

Wenhui Li:Key Laboratory of Traffic Safety on Track of Ministry of Education, School of Traffic & Transportation Engineering,Central South University, Changsha 410075, China

Zijian Guo:Key Laboratory of Traffic Safety on Track of Ministry of Education, School of Traffic & Transportation Engineering,Central South University, Changsha 410075, China

Xuhui He: School of Civil Engineering, Central South University, Changsha 410075, China

Youwu Wang:Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

Abstract
Present experimental investigation aims to reduce the shedding of vortex in the near wake region of a circular cylinder using a perforated splitter plate. Perforated plates were placed in the wake region of the cylinder and aligned with the streamwise direction. The length of the plates was equal to the diameter of the cylinder. Different plate porosities and locations were examined and obtained results were compared to the baseline cylinder. Flow measurements downstream of the cylinder were performed in a water channel by employing a particle image velocimetry technique (PIV) at a Reynolds number of Re=5x103. It is observed that the effect of the porosity on the flow characteristics of the cylinder depends on the location of the plate. The strength of shear layers and flow fluctuations in the near wake region of the cylinder are considerably diminished by the perforated splitter plate. It is found that the porosity of ε=0.3 is the most effective control element for gap ratio of G/D=0.5. On the other hand, proper gap ratio is determined as G/D=2 for porosity of ε=0.7. It is concluded in the present study that the perforated splitter plate could be used as alternative passive flow control technique in order to reduce vortex shedding of the cylinder.

Key Words
circular cylinder; passive flow control; perforated splitter plate; vortex shedding reduction

Address
Serdar Sahin:Department of Mechanical Engineering, University of Cukurova, Adana, 01330, Turkey

Tahir Durhasan:Department of Aerospace Engineering, University of Adana Alparslan Turkes Science and Technology, Adana, 01250, Turkey

Engin Pinar:Department of Ceyhan Mechanical Engineering, University of Cukurova, Adana, 01950, Turkey

Huseyin Akilli:Department of Mechanical Engineering, University of Cukurova, Adana, 01330, Turkey


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