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CONTENTS
Volume 41, Number 6, December 2025
 

Abstract
To ensure the safety performance of VLFS at marine airports, it is essential to accurately estimate dynamic response under extreme marine conditions. The characteristics of VLFS at marine airports and the dynamic reaction of connectors play a crucial role. This study simulates water tank experiments under extreme wind-wave interactions using STAR-CCM+ and CFD FEM. It analyzes the vertical displacement of a single module of VLFS in marine and how it is affected by wavelength and direction from a frequency domain. And dynamic response of connectors how it is affected by various sea conditions, wave directions, and connectors stiffness. Research indicates that vertical displacement caused by elastic deformation cannot be ignored. The vertical displacement achieves maximum magnitude when the wavelength approaches the length of the floating body. When the wave angle increases or decreases, the amplitude of vertical displacement does not show a monotonically rising or falling pattern. Transverse loads are more strongly impacted by wave angle than in the other two directions, and the load values on the connectors are especially sensitive at wave angles of 45° and 60°. The stiffness of the connectors should be lower than the K6 for designing VLFS at marine airports.

Key Words
CFD-FEM; dynamic reaction; extreme winds and waves; frequency domain analysis; marine airports; VLFS

Address
Lijun Wang: 1)Department of civil and airport engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)Department of civil engineering, Jincheng College of Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China

Shitang Ke:1)Department of civil and airport engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)Department of civil engineering, Jincheng College of Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China

Hehe Ren:1)Department of civil and airport engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)3Jiangsu Airport Infrastructure Safety Engineering Research Center,
Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China

Abstract
The wind-induced responses of the transmission towers obtained using time and frequency domain methods were investigated and compared. The influence of key parameters, including the cut-off frequency ωu, time step, sampling period, and frequency amount N, on the simulating results was clarified in the process of the harmonic superposition method (HSM). Furthermore, the effects of the wind spectrum and coherence function on the transmission towers' responses are examined. Finally, the appropriate values for the cut-off frequencies for obtaining the displacement and acceleration responses were provided. In the process of HSM, it is recommended to use a time step of 2π/2ωu. Otherwise, the high-frequency component of the simulated spectrum will be distorted or inadequate if a larger or smaller time step is applied. The recommended sampling length is 2πN/ωu. Using a great sampling length will result in a repeating time history. If the cut-off frequencies used in the HSM of the time domain analysis and the upper limit of the integral in the frequency domain analysis are the same, the displacements of the two approaches are almost equal. In terms of acceleration, the responses at the cut-off frequency prior to and following the first-order circular frequency differ significantly. Suggestions for cut-off frequency selection are made based on response type. For the displacement response, the cut-off frequency should be more than the first-order circular frequency, while for the acceleration response, it should be at least 8π. The coherence function has a significant effect on the response, with the frequency-independent coherence function yielding greater standard deviations for both displacement and acceleration than the frequency-dependent model.

Key Words
cut-off frequency; frequency domain method; harmonic superposition method; time domain method; transmission tower

Address
Guohui Shen: Institute of Structural Engineering, Zhejiang University, Hangzhou, China

Hangcong Yu:The Architectural Design and Research Institute of Zhejiang University Co., Ltd. Hangzhou, China

Yingneng Zhao:China Energy Engineering Group Zhejiang Power Design Institute Co. Ltd, Hangzhou, China

Liang Yu:China Energy Engineering Group Jiangsu Power Design Institute Co. Ltd, Nanjing, China

Buhui Li:China Energy Engineering Group Jiangsu Power Design Institute Co. Ltd, Nanjing, China

Abstract
The novel Floating Tube Photovoltaic (FTPV) system at sea is subjected to dual nonlinear loads from wind and waves, with significant inter-row interference effects observed in both the upper photovoltaic array and the lower floating tube platform, leading to a more complex flow field driving mechanism and load distribution pattern across the entire structural system. This study, based on the Fujian Dongshan offshore floating photovoltaic demonstration project, independently designed a new type of floating tube support platform with a 6-row, 3-span flexible photovoltaic array structure. The study implemented real-time coupling of nonlinear interferences between wind and waves using the VOF wave model and established a fluid structure interference simulation method based on overlapping grid technology. Comparative analyses were conducted on the evolution mechanisms of the wind and wave fields of the FTPV array under 0° and 180° wind-wave co-directional conditions, exploring the dual nonlinear aerodynamic and hydrodynamic load distribution characteristics of the FTPV array. The research results indicate that the upper photovoltaic panels generate separated vortices and counterclockwise spanwise vortices under0° and 180° conditions, respectively, while the lower floating tubes exhibit bubble vortex breakdown under 0° conditions and vortex breakdown with early vortex dissipation under180° conditions. The maximum aerodynamic loads under both conditions occur at the windward first row and the fourth row, with a maximum reduction rate of 93.45% in the rear rows. In addition, a two-dimensional load distribution model was established based on nonlinear fitting. The maximum reductions in hydrodynamic loads were 52.6% and 66.9%, with spectral peak frequencies corresponding to 0.32 Hz and 0.24 Hz, respectively. The Hurst exponents consistently exceed 0.5, indicating significant nonlinear characteristics of the loads, and the nonlinearity continued to increase with the development of the wave field.

Key Words
flow field evolution; hurst exponent; new floating tube flexible photovoltaic array; nonlinear load characteristics; wind-wave coupling

Address
Tiantian Cai:1)Department of Civil and Airport Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)Key Laboratory of Civil Engineering Dynamic Multi Disaster Protection in Jiangsu Universities (Nanjing University of Aeronautics and Astronautics), Nanjing 211106, China

Shitang Ke:1)Department of Civil and Airport Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)Key Laboratory of Civil Engineering Dynamic Multi Disaster Protection in Jiangsu Universities (Nanjing University of Aeronautics and Astronautics), Nanjing 211106, China

Fawu Wang:1)Department of Civil and Airport Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)Key Laboratory of Civil Engineering Dynamic Multi Disaster Protection in Jiangsu Universities (Nanjing University of Aeronautics and Astronautics), Nanjing 211106, China

Wencai Wang:Key Laboratory of Civil Engineering Dynamic Multi Disaster Protection in Jiangsu Universities (Nanjing University of Aeronautics and Astronautics), Nanjing 211106, China

Qilong Li:1)Department of Civil and Airport Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)Key Laboratory of Civil Engineering Dynamic Multi Disaster Protection in Jiangsu Universities (Nanjing University of Aeronautics and Astronautics), Nanjing 211106, China

Xingyu Zhang:1)Department of Civil and Airport Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2)Key Laboratory of Civil Engineering Dynamic Multi Disaster Protection in Jiangsu Universities (Nanjing University of Aeronautics and Astronautics), Nanjing 211106, China

Abstract
This study experimentally investigates the vortex-induced vibration (VIV) of a 1:50 scale box girder bridge model in a multi-fan wind tunnel. We generated complex wind fields to reflect realistic conditions, including non-stationary (linearly increasing/decreasing, sinusoidal, and random) and spanwise non-uniform (linear and parabolic) velocity profiles. The effect of turbulence was also examined using active control blades at the tunnel inlet. Results show that all non-stationary and non uniform conditions reduce VIV displacement compared to stationary and uniform flow. Notably, a parabolic wind profile reduced the VIV RMS displacement by 34.4%, proving more effective in suppressing the VIV amplitude than a linear profile (7.8% reduction) due to its greater disruption of spanwise vortex correlation. In the non-stationary flow, the VIV response is governed by the time available for energy accumulation. Furthermore, a significant asymmetry was observed, with gradually increasing wind velocities inducing substantially larger VIV amplitudes than decreasing velocities, suggesting a hysteresis effect. For the random wind fields, VIV was significant when the velocity range (Max-Min=1 m/s) was close to the stationary VIV range (Max-Min=0.8 m/s), but became negligible when the range was larger (Max-Min=2 m/s). Activating the blades intensified turbulence (e.g., from 4.0% to 14.7%), which consistently suppressed VIV by disrupting periodic vortex shedding. These findings underscore the importance of considering spatio-temporal wind variations in bridge aerodynamics, as traditional uniform flow tests may be overly conservative.

Key Words
long-span bridge; multi-fan wind tunnel; non-stationary wind field; non-uniform wind field; vortex-induced vibration

Address
XiaoLong Deng:Artificial Intelligence for Wind Engineering (AIWE) Lab, School of Intelligent Civil and Ocean Engineering, Harbin Institute of Technology, Shenzhen, 518055, China

Hao Hong:Artificial Intelligence for Wind Engineering (AIWE) Lab, School of Intelligent Civil and Ocean Engineering, Harbin Institute of Technology, Shenzhen, 518055, China

Pengfei Lin:Artificial Intelligence for Wind Engineering (AIWE) Lab, School of Intelligent Civil and Ocean Engineering, Harbin Institute of Technology, Shenzhen, 518055, China

Gang Hu:1)Artificial Intelligence for Wind Engineering (AIWE) Lab, School of Intelligent Civil and Ocean Engineering,
Harbin Institute of Technology, Shenzhen, 518055, China
2)Guangdong Provincial Key Laboratory of Intelligent and Resilient Structures for Civil Engineering,
Harbin Institute of Technology, Shenzhen, 518055, China

Wenli Chen:1)Artificial Intelligence for Wind Engineering (AIWE) Lab, School of Intelligent Civil and Ocean Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
2)3Laboratory of Intelligent Civil Infrastructure (LiCi), Harbin Institute of Technology, Harbin, 150090, China

Bernd R. Noack:1)Chair of Artificial Intelligence and Aerodynamics, School of Mechanical Engineering and Automation,
Harbin Institute of Technology, Shenzhen, Room 313, Building C, University Town, Xili, Shenzhen, 518055, China
2)Guangdong Provincial Key Laboratory of Intelligent Morphing Mechanisms and Adaptive Robotics,
Harbin Institute of Technology, Shenzhen, 518055, China

Abstract
High-speed maglev trains have no direct contact with the track and rely on the modulation of the electromagnetic force to maintain their posture, which poses significant challenges to safety and comfort in crosswinds compared with the conventional wheel-rail trains. Regarding a high-speed maglev train on a common simply supported girder bridge, the aerodynamic forces of the high-speed maglev train and the bridge girder under different yaw angles are measured in the wind tunnel, with 1:20 scaled models and force balances. The aerodynamic admittances of the high-speed maglev train and the bridge girder are also tested and identified. Effects of the location of the maglev train, the suspension gap and the shape of the head car on the aerodynamic forces are explored. The results show that the aerodynamic lift coefficient of the maglev train increases as the suspension gap increases, with an increment of 0.302 from 2mm gap to 12mm gap. The turbulence affects the trend of the lift coefficient of the maglev train as the yaw angle is larger than 60°. The drag coefficients of the bridge girder in turbulent flow are larger than those in uniform flow, about 142.3% at 90° yaw angle. It is found that the aerodynamic admittances of the bridge girder are larger at lower reduced frequencies at high yaw angles, while they are larger at higher reduced frequencies at lower yaw angles. The side force and lift admittance of the maglev train are approximately the same to a specific reduced frequency as the yaw angle is larger than 60°. The aerodynamic admittances of the maglev train and bridge girder at different yaw angles are influenced by the maglev train location.

Key Words
aerodynamic admittance; aerodynamic force; high-speed maglev train; train-bridge system; wind tunnel test

Address
Bin Wang:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
3)State Key Laboratory of Bridge Intelligent and Green Construction, 610031 Chengdu, China

Lingfeng Ma:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
3)State Key Laboratory of Bridge Intelligent and Green Construction, 610031 Chengdu, China

Gang Deng:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
3)State Key Laboratory of Bridge Intelligent and Green Construction, 610031 Chengdu, China

Weixu Wang:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
3)State Key Laboratory of Bridge Intelligent and Green Construction, 610031 Chengdu, China

Huoyue Xiang:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
3)State Key Laboratory of Bridge Intelligent and Green Construction, 610031 Chengdu, China

Helu Yu:School of Civil Engineering, Chongqing Jiaotong University, 400074 Chongqing, China

Yongle Li:1)Department of Bridge Engineering, Southwest Jiaotong University, 610031 Chengdu, China
2)Wind Engineering Key Laboratory of Sichuan Province, 610031 Chengdu, China
3)State Key Laboratory of Bridge Intelligent and Green Construction, 610031 Chengdu, China

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