Abstract
To accurately predict the nonlinear vibration characteristics of large wind turbine blades under large
deformations, this study addresses the limitations of existing research in analyzing multi-directional coupled vibration
frequencies and modeling unsteady aerodynamic damping, conducting systematic theoretical and numerical
investigations. A comprehensive vibration governing equation, incorporating aerodynamic effects, cone angle, and
high-order nonlinear terms, is established; concurrently, a nonlinear modal analysis method based on the method of
multiple scales is developed, which effectively reveals the laws of nonlinear frequency shifts in the system.
Furthermore, nonlinear vibration equations with and without aerodynamic damping are derived, and a theoretical
framework is constructed—one capable of accurately describing unsteady aerodynamic forces and achieving efficient
coupling with nonlinear structural models. Comparative analysis with finite element solutions demonstrates the
superior accuracy of the proposed methodology. Numerical simulation findings demonstrate that nonlinear frequencies
are consistently lower than linearly predicted values, with notable deviations under extreme parameter conditions.
Parametric analyses uncover the influence of complex coupling relationships among setting angle, rotational speed,
and inflow speed ratio on blade vibration characteristics. This work delivers reliable theoretical foundations and
numerical tools for frequency prediction, resonance avoidance, and aeroelastic stability design of large wind turbine
blades.
Key Words
edgewise vibration; method of multiple scales; nonlinear modal analysis; wind turbine blades
Address
Zhidong Zhao:1)State Key Laboratory for Safe Mining of Deep Coal Resources and Environment Protection,
Anhui University of Science and Technology, Huainan 232001, P. R. China
2)School of Mechanics and Optoelectronic Physics, Anhui University of Science and Technology,
Huainan 232001, P. R. China
Liang Li:1)State Key Laboratory for Safe Mining of Deep Coal Resources and Environment Protection,
Anhui University of Science and Technology, Huainan 232001, P. R. China
2)School of Mechanics and Optoelectronic Physics, Anhui University of Science and Technology,
Huainan 232001, P. R. China
Hongwei Zhou:1)National Key Laboratory of Strength and Structural Integrity, China Aircraft Strength Research Institute,
Xi'an 710065, P. R. China
4State Key Laboratory of Strength and Vibration of Mechanical Structures, Xi
Abstract
Long-span flexible bridges are prone to vortex-induced vibration (VIV), constituting a complex wind
vehicle-bridge interaction together with crosswinds that compromises both operational safety and habitability. By
integrating wind tunnel testing, CFD, and multibody dynamics, this research explores the synergistic impacts of VIV
parameters and road friction on vehicular performance. Findings reveal that while safety metrics are primarily
sensitive to wind speed and surface adhesion—exacerbated by VIV—ride comfort is dictated by the wind angle of
attack (AoA). Specifically, a -3° AoA intensifies vertical oscillations and lateral drift, whereas a +3° AoA triggers
pronounced torsional vibration and yawing; both effects are nonlinearly amplified as road friction diminishes.
Notably, the Annoyance Rate Model (ARM) demonstrates superior sensitivity over the ISO 2631-1 standard in
quantifying vibration-induced psychological distress. These insights offer a robust theoretical foundation for
developing proactive traffic control and early-warning protocols for bridges under extreme wind conditions.
Key Words
bridge vortex-induced vibration; pavement friction coefficient; ride comfort; vehicle stability;
wind angle of attack; wind tunnel testing
Address
Zhiqun Yuan:1)Fujian Provincial Key Laboratory of Wind Disaster and Wind Engineering, Xiamen, 361024, China
2)School of Mechanical and Automotive Engineering, Xiamen University of Technology, Xiamen 361024, China
3)Fujian Provincial Key Laboratory of Advanced Design and Manufacture for Bus Coach,
Xiamen University of Technology, Xiamen 361024, China
Maoxing Zhu:School of Mechanical and Automotive Engineering, Xiamen University of Technology, Xiamen 361024, China
Jiayue Li:School of Mechanical and Automotive Engineering, Xiamen University of Technology, Xiamen 361024, China
Dandan Xia:Fujian Provincial Key Laboratory of Wind Disaster and Wind Engineering, Xiamen, 361024, China
Huaifeng Wang:Fujian Provincial Key Laboratory of Wind Disaster and Wind Engineering, Xiamen, 361024, China
Li Lin:Fujian Provincial Key Laboratory of Wind Disaster and Wind Engineering, Xiamen, 361024, China
Abstract
A significant portion of a vehicle's aerodynamic drag is generated at its rear, which is a key indicator of its
overall aerodynamic performance. Therefore, controlling flow separation at the vehicle's rear is a key method for
reducing aerodynamic drag. This study investigates the Ahmed car model with a rear slant angle of 25°, proposing
the introduction of a wavy structure above the vertical plane at the rear to manipulate the flow. The study employs the
Improved Delayed Detached Eddy Simulation (IDDES) method, based on the two-equation k-ω SST model, to
examine the influence of wave amplitude on aerodynamic drag. The impact of the wavy design on aerodynamic drag
is investigated by analyzing the near-wake flow field, the development of vortices around the wavy structure, and the
pressure distribution on the model's rear surface. The results indicate that properly placed wavy structures can
effectively improve the rear flow structure, increase the surface pressure at the tail, and significantly reduce the
overall pressure drag, achieving a maximum drag reduction of 18.8%.
Key Words
ahmed body; drag reduction; numerical simulation; passive flow control; wavy trailing edge
Address
Taowei Yang:School of Energy and Power Engineering, University of Shanghai for Science and Technology,
Shanghai 200093, China
Dahai Luo:School of Energy and Power Engineering, University of Shanghai for Science and Technology,
Shanghai 200093, China
Changhao Luo:School of Energy and Power Engineering, University of Shanghai for Science and Technology,
Shanghai 200093, China
Haojie Yang:School of Energy and Power Engineering, University of Shanghai for Science and Technology,
Shanghai 200093, China
Abstract
Double-curvature cable roofs are vulnerable to wind loads because of their high flexibility and light
weight. The accurate evaluation of wind pressure distribution on these roofs is necessary to gain insights into their
aeroelastic behavior. This study investigates computational fluid dynamics (CFD) performance to reproduce wind
pressure distribution on double-curvature roofs. Evaluation is based on steady Reynolds-Averaged Navier-Stokes
(RANS) and the Scale-Adaptive Simulation (SAS) approaches, validated with wind-tunnel data of a hyperbolic
paraboloid roof. The double-curvature nature of the roof is shown to lead to instability of flow and as such significant
changes in wind pressure distribution. The findings reveal that RANS and SAS models can efficiently reproduce
mean wind-induced pressure coefficient on the roof with an overall average absolute deviation of 0.06 and 0.17 for
θ=0°, and 0.1 and 0.06 for θ=90°, respectively. The mean flow field using RANS and SAS are compared showing
that RANS underestimates and overestimates the height and length of SAS separation bubble and as such RANS
predicts lower suction than SAS. The peak factor using SAS shows that the non-Gaussian nature of the flow is
pronounced at the flow-detaching regions of the roof, emphasizing how crucial it is to effectively replicate the peak
pressure distribution on double-curved roofs.
Key Words
Scale-Adaptive Simulation (SAS); double-curved roof; mean pressure; non-Gaussian flow; separation bubble; turbulence models
validation; S
Address
Elshaimaa A. Ahmed:1)Department of Civil and Environmental Engineering, Western University, London, Ontario, Canada
2)Department of Structural Engineering, Mansoura University, Mansoura, Egypt
Ashraf A. El Damatty:Department of Civil and Environmental Engineering, Western University, London, Ontario, Canada
Abstract
This paper presents an approximate iterative method for predicting flutter of bridge deck section models
taking into account the static rotation angle of attack of the bridge deck. The method consists of an iterative process
between the flow-induced static rotation angle of attack and the estimated critical flutter wind speed. The improved
flutter prediction relies on a simplified expression for the critical flutter speed from quasi-steady theory. This
simplified expression only considers the static moment slope and an assumed empirical factor. The iterative method
is also applied in flutter analysis based on aerodynamic derivatives. Both approaches effectively predict the critical
wind speed for the onset of flutter and the corresponding deck rotation angle of attack, in agreement with
experimental evidence. The improved flutter prediction is evaluated through wind tunnel testing by investigating four
variations of the twin-box deck of the 1915 Canakkale Bridge, changing the layout of the gantry rails. Using the
iterative method in both flutter prediction approaches on the four twin-box deck configurations, successfully predict
the critical flutter wind speed matching wind tunnel experiments. If the flutter prediction approaches are applied
without the iterative method, an incorrect flutter prediction is obtained. Through the investigation of the different deck
configurations, the inner gantry rails have proven to have a pronounced effect on the aerodynamic flutter stability of
the analysed twin-box girders. Including the inner gantry rails on the twin-box girder, makes the deck rotate nose-up
and enhances the flutter stability.
Key Words
aerodynamic derivatives; aerodynamic stability; angle of attack; flutter prediction; static force
coefficients; twin-box bridge deck; wind tunnel tests
Address
Maja RØnne:COW A/S, Parallelvej 2, 2800 Kongens Lyngby, Denmark
Allan Larsen:COW A/S, Parallelvej 2, 2800 Kongens Lyngby, Denmark
Tommaso Argentini:Department of Mechanical Engineering, Politecnico di Milano, Via Giuseppe La Massa 1, 20156 Milan, Italy
Jens H. Walther:Department of Civil and Mechanical Engineering, Technical University of Denmark, Koppels Allé 403, 2800, Kongens Lyngby, Denmark
Abstract
The aerodynamic interference effects between parallel twin box girders, motivated by bridges with
variable cross-sections, were investigated in this study. The analysis is performed on sectional models with varying
aspect ratios at different angles of attack (AoAs) and gap distances using wind tunnel pressure measurements.
Quantitative analysis of the interference effect on the drag and lift coefficients was conducted by introducing an
interference factor. Furthermore, static numerical simulations were performed to explore the underlying qualitative
mechanism of aerodynamic interference on force coefficients. Our investigation reveals that, compared with a single
box girder, the aerodynamic forces on the windward girder exhibit minimal changes, while those on the leeward
girder undergo significant alterations. Regarding the drag coefficient, the interference effect on the leeward girder
results in a pronounced reduction, particularly when both smaller gap distances and larger aspect ratios are present
simultaneously. For the lift coefficient, the interference effect on the leeward girder primarily manifests as a reduction
at most positive angles of attack. Numerical simulation results provide preliminary insights that the formation of
vortices on the windward-side web of the leeward girder is the primary mechanism responsible for these
aerodynamic force variations.
Key Words
aerodynamic force coefficient; Angle of Attack (AoA); aspect ratio; gap distance; interference
factor; parallel twin box girders with different aspect ratios
Address
Anjie Chen:School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
Dewang Zhang:School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
Xiaobing Liu:1)School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
2)Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province, Shijiazhuang 050043, China
3)State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures,
Shijiazhuang Tiedao University, Shijiazhuang 050043, China
