Abstract
This paper presents a theoretical method to deal with the aerodynamic performance and pitch optimization of the
horizontal axis wind turbine blades at low wind speeds. By considering a blade element, the functional relationship among the
angle of attack, pitch angle, rotational speed of the blade, and wind speed is derived in consideration of a quasi-steady
aerodynamic model, and aerodynamic loads on the blade element are then obtained. The torque and torque coefficient of the
blade are derived by using integration. A polynomial approximation is applied to functions of the lift and drag coefficients for the
symmetric and asymmetric airfoils respectively, where specific expressions of aerodynamic loads as functions of the angle of
attack (which is a function of pitch angle) are obtained. The pitch optimization problem is investigated by considering the
maximum value problem of the instantaneous torque of a blade as a function of pitch angle. Dynamic pitch laws for HAWT
blades with either symmetric or asymmetric airfoils are derived. Influences of parameters including inflow ratio, rotational
speed, azimuth, and wind speed on torque coefficient and optimal pith angle are discussed.
Address
Ying Zhang:School of Mechanics and Optoelectronic Physics, Anhui University of Science and Technology, Huainan 232001, China
Liang Li:School of Mechanics and Optoelectronic Physics, Anhui University of Science and Technology, Huainan 232001, China
Long Wang:School of Mechanical Engineering, Anhui University of Science and Technology, Huainan 232001, China
Weidong Zhu:Department of Mechanical Engineering, University of Maryland, Baltimore County, Maryland 21250, USA
Yinghui Li:School of Mechanics and Aerospace Engineering, Southwest Jiaotong University, Chengdu 610031, China
Jianqiang Wu:1)School of Mechanics and Optoelectronic Physics, Anhui University of Science and Technology, Huainan 232001, China 2)School of Mechanics and Aerospace Engineering, Southwest Jiaotong University, Chengdu 610031, China
Abstract
Severe natural multi-hazard events can cause damage to infrastructure and economic losses of billions of dollars.
The challenges of modeling these losses include dependency between hazards, cause and sequence of loss, and lack of available
data. This paper presents and explores multi-hazard loss modeling in the context of the combined wind and rain vulnerability of
mid/high-rise buildings during hurricane events. A component-based probabilistic vulnerability model provides the framework
to test and contrast two different approaches to treat the multi-hazards: In one, the wind and rain hazard models are both
decoupled from the vulnerability model. In the other, only the wind hazard is decoupled, while the rain hazard model is
embedded into the vulnerability model. The paper presents the mathematical and conceptual development of each approach,
example outputs from each for the same scenario, and a discussion of weaknesses and strengths of each approach.
Key Words
hurricane; mid/high-rise buildings; model decoupling; wind-and-rain vulnerabilities
Address
Zhuoxuan Wei:1)Mechanical and Civil Engineering Department, Florida Institute of Technology, 150 W. University Blvd., Melbourne, Florida, United States
2)Engineering School of Sustainable Infrastructure & Environment, University of Florida, Gainesville, Florida, United States
Jean-Paul Pinelli:Mechanical and Civil Engineering Department, Florida Institute of Technology, 150 W. University Blvd., Melbourne, Florida, United States
Kurtis Gurley:Engineering School of Sustainable Infrastructure & Environment, University of Florida, Gainesville, Florida, United States
Shahid Hamid:Department of Finance, College of Business, Florida International University,
Modesto A. Maidique Campus, 11200 S.W. 8th Street, Miami, Florida, United States
Abstract
Compared with traditional transmission towers, T-shaped angle towers have long cross-arms and are specially used
for ultrahigh-voltage direct-current (UHVDC) transmission. Nevertheless, the wind loads of T-shaped towers have not received
much attention in previous studies. Consequently, a series of wind tunnel tests on the T-shaped towers featuring cross-arms of
varying lengths were conducted using the high-frequency force balance (HFFB) technique. The test results reveal that the Tshaped tower's drag coefficients nearly remain constant at different testing velocities, demonstrating that Reynolds number
effects are negligible in the test range of 1.26 x 104
-2.30 x 104. The maximum values of the longitudinal base shear and torsion
of the T-shaped tower are reached at 15° and 25° of wind incidence, respectively. In the yaw angle, the crosswind coefficients of
the tower body are quite small, whereas those of the cross-arms are significant, and as a result, the assumption in some load
codes (such as ASCE 74-2020, IEC 60826-2017 and EN 50341-1:2012) that the resultant force direction is the same as the wind
direction may be inappropriate for the cross-arm situation. The fitting formulas for the wind load-distribution factors of the tower
body and cross-arms are developed, respectively, which would greatly facilitate the determination of the wind loads on T-shaped
angle towers.
Key Words
drag coefficient; estimating equation; T-shaped tower; wind load-distribution factor; wind tunnel test
Address
Guohui Shen:College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China
Kanghui Han:College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China
Baoheng Li:College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China
Jianfeng Ya:1)College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China
2)College of Civil Engineering and Architecture, Zhejiang University of Water Resources and Electric Power,
508 2nd Street, Qiantang District, Hangzhou, China
Abstract
This study presents a mode analysis of 3D turbulent velocity data around a square-section building model to identify
the dynamic system for Karman-type vortex shedding. Proper orthogonal decomposition (POD) was first performed to extract
the significant 3D modes. Magnitude-squared coherence was then applied to detect the phase consistency between the modes,
which were roughly divided into three groups. Group 1 (modes 1-4) depicted the main vortex shedding on the wake of the
building, with mode 2 being controlled by the inflow fluctuation. Group 2 exhibited complex wake vortexes and single-sided
vortex phenomena, while Group 3 exhibited more complicated phenomena, including flow separation. Subsequently, a thirdorder polynomial regression model was used to fit the dynamics system of modes 1, 3, and 4, which revealed average trend of
the state trajectory. The two limit cycles of the regression model depicted the two rotation directions of Kármán-type vortex.
Furthermore, two characteristic periods were identified from the trajectory generated by the regression model, which indicates
fast and slow motions of the wake vortex. This study provides valuable insights into 3D mode morphology and dynamics of
Karman-type vortex shedding that helps to improve design and efficiency of structures in turbulent flow.
Key Words
3D turbulent structure analysis; dynamic system identification; limit cycle; proper orthogonal decomposition;
wind velocity field
Address
Lei Zhou, Bingchao Zhang and K.T. Tse:Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong, China
Abstract
Long-span suspension bridges located in typhoon-prone regions face significant risks of flutter instability,
particularly in girder erection. Despite the implementation of aerodynamic countermeasures designed for the service stage, the
flutter stability of bridge in girder erection may not meet the required standards. Nowadays, the double-deck truss girder is
increasingly common in practical engineering which exhibits different performance from the single-deck truss girder. To gain
insights into the flutter performance of this girder type and determine temporary aerodynamic countermeasures for flutter
suppression in girder erection, wind tunnel tests were conducted. The effects of affiliated members on the flutter performance
were first examined. Subsequently, different aerodynamic countermeasures were designed and their effectiveness was tested.
The results indicate that the stabilizers above and below the upper and lower decks are the most effective for the flutter stability
of bridge at positive and negative angles of attack, respectively. The higher the stabilizers are, the better the effect on flutter
suppression achieves. Considering the feasibility in practical engineering, a temporary stabilizer above the upper deck was
considered. It is expected that the results could provide references for the aerodynamic design of double-deck truss girder during
erection.
Address
Zewen Wang:Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
Bokai Yang:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
Haojun Tang:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)State Key Laboratory of Bridge Intelligent and Green Construction, 611756 Chengdu, China
3)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
Yongle Li:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)State Key Laboratory of Bridge Intelligent and Green Construction, 611756 Chengdu, China
3)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
