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CONTENTS
Volume 32, Number 3, March 2021
 


Abstract
A series of wind tunnel tests, including 1:50 sectional model tests, 1:50 free-standing bridge tower tests and 1:70 full-bridge aeroelastic model tests were carried out to systematically investigate the aerodynamic performance of the Hong Kong-Zhuhai-Macao Bridge (HZMB). The test result indicates that there are three wind-resistant safety issues the HZMB encounters, including unacceptable low flutter critical wind speed, vertical vortex-induced vibration (VIV) of the main girder and galloping of the bridge tower in across-wind direction. Wind-induced vibration of HZMB can be effectively suppressed by the application of aerodynamic and mechanical measures. Acceptable flutter critical wind speed is achieved by optimizing the main girder form (before: large cantilever steel box girder, after: streamlined steel box girder) and cable type (before: central cable, after: double cable); The installations of wind fairing, guide plates and increasing structural damping are proved to be useful in suppressing the VIV of the HZMB; The galloping can be effectively suppressed by optimizing the interior angle on the windward side of the bridge tower. The present works provide scientific basis and guidance for wind resistance design of the HZMB.

Key Words
Hong Kong-Zhuhai-Macao Bridge; aerodynamic performance; wind-induced vibration; suppression measure; wind tunnel test

Address
Cunming Ma:School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China

Zhiguo Li:School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China

Fanchao Meng:CCCC Highway Consultants Co., Ltd, Beijing, 100000, PR China

Haili Liao:Key Laboratory for Wind Engineering of Sichuan Province, Chengdu 610031, PR China

Junxin Wang:School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China

Abstract
The estimation of the extreme wind load (effect) under a mean recurrence interval (MRI) is an important task in the wind-resistant design for the structure. It can be predicted by either first-order method or full-order method, depending on the accuracy and complexity requirement. Although the first-order method with the consideration of wind directionality has been proposed, less work has been done on the full-order method, especially with the wind directionality. In this study, the full-order method considering the wind directionality is proposed based on multivariate joint probability distribution. Meanwhile, considering two wind directions, the difference of the corresponding results based on the first-order method and full-order method is analyzed. Finally, based on the measured wind speed data, the discrepancy between these two methods is investigated. Results show that the difference between two approaches is not obvious under larger MRIs while the underestimation caused by the first-order method can be larger than 15% under smaller MRIs. Overall, the first-order method is sufficient to estimate the extreme wind load (effect).

Key Words
extreme wind load (effect); first-order method; full-order method; wind directionality; multivariate joint distribution; mean recurrence interval

Address
Ying Luo:School of Civil Engineering, Changsha University of Science & Technology, Changsha, China 410114

Guoqing Huang:School of Civil Engineering, Chongqing University, Chongqing, China 400044

Yan Han:School of Civil Engineering, Changsha University of Science & Technology, Changsha, China 410114

C.S. Cai:Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, U.S.A.

Abstract
Cold regions with high air density and wind speed attract wind energy producers across the globe exhibiting its potential for wind exploitation. However, exposure of wind turbine blades to such cold conditions bring about devastating impacts like aerodynamic degradation, production loss and blade failures etc. A series of wind tunnel tests were performed to investigate the effect of icing on the aerodynamic properties of wind turbine blades. A baseline clean wing configuration along with four different ice accretion geometries were considered in this study. Aerodynamic force coefficients were obtained from the surface pressure measurements made over the test model using MPS4264 Simultaneous pressure scanner. 3D printed Ice templates featuring different ice geometries based on Icing Research Tunnel data is utilized. Aerodynamic characteristics of both the clean wing configuration and Ice accreted geometries were analysed over a wide range of angles of attack (α) ranging from 0° to 24° with an increment of 3° for three different Reynolds number in the order of 105. Results show a decrease in aerodynamic characteristics of the iced aerofoil when compared against the baseline clean wing configuration. The key flow field features such as point of separation, reattachment and formation of Laminar Separation Bubble (LSB) for different icing geometries and its influence on the aerodynamic characteristics are addressed. Additionally, attempts were made to understand the influence of Reynolds number on the iced-aerofoil aerodynamics.

Key Words
icing; wind turbine; surface pressure distribution; aerodynamic characteristics

Address
Aakhash Sundaresan:Turbulence and Flow Control Lab, School of Mechanical Engineering, SASTRA Deemed University, Thanjavur, Tamil Nadu-613401, India

S. Arunvinthan, A.A. Pasha:Department of Aerospace Engineering, King Abdulaziz University, Jeddah-21589 Saudi Arabia

S. Nadaraja Pillai:Turbulence and Flow Control Lab, School of Mechanical Engineering, SASTRA Deemed University, Thanjavur, Tamil Nadu-613401, India

Abstract
Wind tunnel test models for super tall buildings mainly include synchronized pressure models, high-frequency force balance models, forced vibration models and aeroelastic models. Aeroelastic models, especially MDOF aeroelastic models, are relatively accurate, and designing MDOF model is an important step in aero-model wind tunnel tests. In this paper, the authors propose a simple and accurate design method for MDOF model. The purpose of this paper is to make it easier to design MDOF models without unnecessary experimentation, which is of great significance for the use of the aero-model for tall buildings.

Key Words
wind tunnel test; tall buildings; MDOF aeroelastic model; design method

Address
Lei Wang:School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, 454000, China/ School of Urban Construction, Wuchang University of Technology, Wuhan, 430223, China/State Key Laboratory of Building Safety and Built Environment, Beijing, 100013, China

Yong-jie Zhu:School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, 454000, China

Ze-kang Wang:School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, 454000, China

Yu-hui Fan:School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan, 454000, China/ School of Urban Construction, Wuchang University of Technology, Wuhan, 430223, China

Abstract
This study analyzed the pressure patterns and local pressure of tall buildings with corner modifications (recessed and chamfered corner) using wind tunnel tests and proper orthogonal decomposition (POD). POD can distinguish pressure patterns by POD mode and more dominant pressure patterns can be found according to the order of POD modes. Results show that both recessed and chamfered corners effectively reduced wind-induced responses. Additionally, unique effects were observed depending on the ratio of corner modification. Tall building models with recessed corners showed fluctuations in the approaching wind flow in the first POD mode and vortex shedding effects in the second POD mode. With large corner modification, energy distribution became small in the first POD mode, which shows that the effect of the first POD mode reduced. Among building models with chamfered corners, vortex shedding effects appeared in the first POD mode, except for the model with the highest ratio of corner modifications. The POD confirmed that both recessed and chamfered corners play a role in reducing vortex shedding effects, and the normalized power spectral density peak value of modes showing vortex shedding was smaller than that of the building model with a square section. Vortex shedding effects were observed on the front corner surfaces resulting from corner modification, as with the side surface. For buildings with recessed corners, the local pressure on corner surfaces was larger than that of side surfaces. Moreover, the average wind pressure was effectively reduced to 88.42% and 92.40% in RE1 on the windward surface and CH1 on the side surface, respectively.

Key Words
tall building; aerodynamic modification; proper orthogonal decomposition; statistical analysis; wind tunnel test

Address
K.T. Tse:Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong

Zeng-Shun Chen:School of Civil Engineering, Chongqing University, Chongqing 400045, China

Dong-Eun Lee:School of Architecture, Civil, Environment and Energy Engineering, Kyungpook National University,
80, Daehak-ro, Buk-gu, Daegu, 41566, South Korea

Bubryur Kim:Department of Architectural Engineering, Dong-A University, Busan 49315, South Korea/ Department of ICT integrated Ocean Smart Cities Engineering, Dong-A University, Busan 49315, Korea

Abstract
In this study, three airfoil families, NACA, FX and S, in each case three from each series with different shapes were investigated at different angles of attack using Computational Fluid Dynamics (CFD) method. To verify the CFD model, simulation results of the NACA 0012 airfoil was compared against the available experimental data and k-ω SST was used as the turbulence model. Lift coefficients, lift to drag ratios and pressure distributions around airfoils were obtained from the CFD simulations and compared each other. The simulations were performed at three Reynolds numbers, Re=2x105, 1x106 and 2x106, and angle of attack was varied between -6 and 12 degrees. According to the results, similar lift coefficient values were obtained for symmetric airfoils reaching their maximum values at similar angles of attack. Maximum lift coefficients were obtained for FX 60-157 and S 4110 airfoils having lift coefficient values around 1.5 at Re=1x106 and 12 degrees of angle of attack. Flow separation occurred close to the leading edge of some airfoils at higher angles of attack, while some other airfoils were more successful in keeping the flow attached on the surface.

Key Words
aerodynamics; airfoil; CFD; NACA series; FX series; S series

Address
Mehmet Numan Kaya:Department of Mechanical Engineering, Necmettin Erbakan University, Konya, Turkey

Ali Riza Kok:Department of Mechanical Engineering, Necmettin Erbakan University, Konya, Turkey

Huseyin Kurt:Department of Mechanical Engineering, Necmettin Erbakan University, Konya, Turkey


Abstract
As high-rise buildings become more and more slender and flexible, the wind effect has become a major concern to modern buildings. At present, wind engineering for high-rise buildings mainly focuses on the following four issues: wind excitation and response, aerodynamic damping, aerodynamic modifications and proximity effect. Taking these four issues of concern in high-rise buildings as the mainline, this paper summarizes the development history and current research progress of wind engineering for high-rise buildings. Some critical previous work and remarks are listed at the end of each chapter. From the future perspective, the CFD is still the most promising technique for structural wind engineering. The wind load inversion and the introduction of machine learning are two research directions worth exploring.

Key Words
high-rise buildings; wind tunnel; field measurement; CWE; CFD; vortex; aerodynamic damping; aerodynamic modifications; proximity effect

Address
Haitao Zhu:College of Civil Engineering, Tongji University, Shanghai 200092, China

Bin Yang:College of Civil Engineering, Tongji University, Shanghai 200092, China

Qilin Zhang:College of Civil Engineering, Tongji University, Shanghai 200092, China

Licheng Pan:College of Civil Engineering, Tongji University, Shanghai 200092, China

Siyuan Sun:College of Civil Engineering, Tongji University, Shanghai 200092, China

Abstract
Bending-twisting coupling induced in big composite wind turbine blades is one of the passive control mechanisms which is exploited to mitigate loads incurred due to deformation of the blades. In the present study, flutter characteristics of bend-twist coupled blades, designed for load alleviation in wind turbine systems, are investigated by time-domain analysis. For this purpose, a baseline full GFRP blade, a bend-twist coupled full GFRP blade, and a hybrid GFRP and CFRP bend-twist coupled blade is designed for load reduction purpose for a 5 MW wind turbine model that is set up in the wind turbine multi-body dynamic code PHATAS. For the study of flutter characteristics of the blades, an over-speed analysis of the wind turbine system is performed without using any blade control and applying slowly increasing wind velocity. A detailed procedure of obtaining the flutter wind and rotational speeds from the time responses of the rotational speed of the rotor, flapwise and torsional deformation of the blade tip, and angle of attack and lift coefficient of the tip section of the blade is explained. Results show that flutter wind and rotational speeds of bend-twist coupled blades are lower than the flutter wind and rotational speeds of the baseline blade mainly due to the kinematic coupling between the bending and torsional deformation in bend-twist coupled blades.

Key Words
wind turbine; composite blade; bend-twist couple; flutter analysis

Address
Touraj Farsadi:Adana Alparslan Turkes Science and Technology University, Department of Aerospace Engineering, Turkey

Altan Kayran:Middle East Technical University, Department of Aerospace Engineering, RUZGEM, Turkey


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