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CONTENTS
Volume 30, Number 4, April 2020
 

Abstract
In this paper, the improvement of the anti-snow performance of a high-speed train (HST) is studied using the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) coupled with the Discrete Phase Model (DPM). The influences of the proposed flow control scheme on the velocity distribution of the airflow and snow particles, snow concentration level and accumulated mass in the bogie cavities are analyzed. The results show that the front anti-snow structures can effectively deflect downward the airflow and snow particles at the entrance of the cavities and alleviate the strong impact on the bogie bottom, thereby decrease the local accumulated snow. The rotational rear plates with the deflecting angle of 45

Key Words
bogie cavity; High-Speed Train (HST); numerical simulation; passive flow control

Address
Guangjun Gao, Zhen Tian, Jiabin Wang, Yan Zhang, Xinchao Su and Jie Zhang: Key Laboratory of Traffic Safety on Track of Ministry of Education, School of Traffic & Transportation Engineering, Central South University, Changsha 410075, China
Z2Joint International Research Laboratory of Key Technology for Rail Traffic Safety, Central South University, Changsha 410075, China
National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle, Changsha 410075, China

Abstract
This study aims at modeling boundary layers (BLs) encountered in sparse and built environments (i.e., open, suburban and urban) at the subsonic Wind Tunnel (WT) at Ryerson University (RU). This WT has an insignificant turbulence intensity and requires a flow-conditioning system consisting of turbulence generating elements (i.e spires, roughness blocks, barriers) to achieve proper turbulent characteristics. This system was developed and validated in the current study in three phases. In phase I, several Computational Fluid Dynamic (CFD) simulations of the tunnel with generating elements were conducted to understand the effect of each element on the flow. This led to a preliminary design of the system, in which horizontal barriers (slats) are added to the spires to introduce turbulence at higher levels of the tunnel. This design was revisited in phase II, to specify slat dimensions leading to target BLs encountered by tall buildings. It was found that rougher BLs require deeper slats and, therefore, two-layer slats (one fixed and one movable) were implemented to provide the required range of slat depth to model most BLs. This system only involves slat movement to change the BL, which is very useful for automatic wind tunnel testing of tall buildings. The system was validated in phase III by conducting experimental wind tunnel testingof the system and comparing the resulting flow field with the target BL fields considering two length scales typically used for wind tunnel testing. A very good match was obtained for all wind field characteristics which confirms accuracy of the system.

Key Words
Wind Tunnel (WT); flow conditioning system; Boundary Layer (BL); turbulence; Computational Fluid Dynamics (CFD); Large Eddy Simulation (LES)

Address
Tarek Ghazal, Jiaxiang Chen, Moustaf Aboutabikh, Haitham Aboshosha and Sameh Elgamal: Civil Engineering Department, Ryerson University, 350 Victoria, St. M5B 2K3, Toronto, Canada

Abstract
Two-dimensional Delayed Detached Eddy Simulation (DDES) was carried out to investigate the uniform flow over a twin-box bridge deck (TBBD) with various gap ratios of L/C=5.1%, 12.8%, 25.6%, 38.5%, 73.3% and 108.2% (L: the gap-width between two girders, C: the chord length of a single girder) at Reynolds number, Re=4x104. The aerodynamic coefficients of the prototype deck with gap ratio of 73.3% obtained from the present simulation were compared with the previous experimental and numerical data for different attack angles to validate the present numerical method. Particular attention is devoted to the fluctuating pressure distribution and forces, shear layer reattachment position, wake velocity and flow pattern in order to understand the effects of gap ratio on dynamic flow interaction with the twin-box bridge deck. The flow structure is sensitive to the gap, thus a change in L/C thus leads to single-side shedding regime at L/C󖼩.6%, and co-shedding regime at L/C󖼳.8% distinguished by drastic changes in flow structure and vortex shedding. The gap-ratio-dependent Strouhal number gradually increases from 0.12 to 0.27, though the domain frequencies of vortices shedding from two girders are identical. The mean and fluctuating pressure distributions is significantly influenced by the flow pattern, and thus the fluctuating lift force on two girders increases or decreases with increasing of L/C in the single-side shedding and co-shedding regime, respectively. In addition, the flow mechanisms for the variation in aerodynamic performance with respect to gap ratios are discussed in detail.

Key Words
twin-box bridge deck; Delayed Detached Eddy Simulation; vortex shedding; aerodynamic forces; gap ratios

Address
Jingmiao Shang, Qiang Zhou, Jin Wang, Mingshui Li: Research Center for Wind Engineering, Southwest Jiaotong University, China
Allan Larsen: COWI Consulting Engineers and Planners A/S, Denmark

Abstract
The paper presents a Life-Cycle Cost–based optimization framework for wind-excited tall buildings equipped with Tuned Mass Dampers (TMDs). The objective is to minimize the Life-Cycle Cost that comprises initial costs of the structure, the control system and costs related to repair, maintenance and downtime over the building

Key Words
tall buildings; wind loads; non-prescriptive design; wind tunnel tests; tuned mass dampers; cost-based optimization

Address
Ilaria Venanzi, Laura Ierimonti : Department of Civil and Environmental Engineering, University of Perugia, Via G. Duranti 93, Perugia, Italy
Luca Caracoglia: Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering Center,360 Huntington Ave., MA 02115, USA

Abstract
One of the growing concerns of the wind energy production is wind ramp events. To improve the wind ramp event forecasts, the nonlinear Kalman filter bias correction method was applied to 24-h wind speed forecasts issued from the WRF model at 70-m height in Zhangbei wind farm, Hebei Province, China for a two-year period. The Kalman filter shows the remarkable ability of improving forecast skill for real-time wind speed forecasts by decreasing RMSE by 32% from 3.26 m s-1 to 2.21 m s-1, reducing BIAS almost to zero, and improving correlation from 0.58 to 0.82. The bias correction improves the forecast skill especially in wind speed intervals sensitive to wind power prediction. The fact shows that the Kalman filter is especially suitable for wind power prediction. Moreover, the bias correction method performs well under abrupt weather transition. As to the overall performance for improving the forecast skill of ramp events, the Kalman filter shows noticeable improvements based on POD and TSS. The bias correction increases the POD score of up-ramps from 0.27 to 0.39 and from 0.26 to 0.38 for down-ramps. After bias correction, the TSS score is significantly promoted from 0.12 to 0.26 for up-ramps and from 0.13 to 0.25 for down-ramps.

Key Words
numerical simulation; wind power prediction; bias correction; nonlinear Kalman filter; WRF model

Address
Jing-Jing Xu:International Center for Climate and Environment Science (ICCES), Institute of Atmospheric Physics,Chinese Academy of Science, Beijing 100029, China
Zi-Niu Xiao:State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG),
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Zhao-Hui Lin:International Center for Climate and Environment Science (ICCES), Institute of Atmospheric Physics,Chinese Academy of Science, Beijing 100029, China



Abstract
Quayside container cranes are important delivery machineries located in the most frontiers of container terminals, where strong wind attacks happen occasionally. Since the previous researches on quayside container cranes mainly focused on the mean wind load and static response characteristics, the fluctuating wind load and dynamic response characteristics require further investigations. In the present study, the aerodynamic wind loads on quayside container cranes were obtained from wind tunnel tests. The probabilistic and spectral models of the fluctuating aerodynamic loads were established. Then the joint probabilistic distributions of dynamic wind-induced responses were derived theoretically based on a series of Gaussian and independent assumption of resonant components. Finally, the results were validated by time domain analysis using wind tunnel data. It is concluded that the assumptions are acceptable. And the presented approach can estimate peak dynamic sliding force, overturning moments and leg uplifts of quayside container cranes effectively and efficiently.

Key Words
quayside container crane; probabilistic distribution; spectral model; wind tunnel tests; wind-induced response

Address
Su Ning, Peng Shitao, Hong Ningning, Wu Xiaotong and Chen Yunyue: Key Laboratory of Environmental Protection in Water Transport Engineering, Tianjin Research Institute for Water Transport Engineering,
China Ministry of Transport, Tianjin, 300456, China

Abstract
A steel high-rise building (HRB) with 15 stories was analyzed under the dynamic load of wind or four different earthquakes taking into consideration the effect of soil-structure interaction (SSI) and using tuned mass damper (TMD) devices to resist these types of dynamic loads. The behavior of the steel HRB as a lightweight structure subjected to dynamic loads is critical especially for wind load with effect maximum at the top of the building and reduced until the base of the building, while on the contrary for seismic load with effect maximum at the base and reduced until the top of the building. The TMDs as a successful passive resistance method against the effect of wind or earthquakes is used to mitigate their effects on the steel high-rise building. Lateral displacements, top accelerations and straining actions were computed to judge the effectiveness of the TMDs on the response of the steel HRB subjected to wind or earthquakes.

Key Words
high-rise building (HRB); steel building; wind; earthquake; dynamic response; tuned mass damper (TMD); soil-structure interaction (SSI)

Address
Denise-Penelope N. Kontoni : Department of Civil Engineering, University of the Peloponnese, 1 M. Alexandrou Str., Koukouli, GR-26334 Patras, Greece
Ahmed Abdelraheem Farghaly:Department of Civil and Architectural Constructions, Faculty of Industrial Education, Sohag University, Sohag 82524, Egypt

Abstract
The strong turbulence characteristic of typhoon not only will significantly change flow field characteristics surrounding the large-scale wind turbine and aerodynamic force distribution on surface, but also may cause morphological evolution of coast dune and thereby form sand storms. A 5MW horizontal-axis wind turbine in a wind power plant of southeastern coastal areas in China was chosen to investigate the distribution law of additional loads caused by wind-sand coupling movement of coast dune at landing of strong typhoons. Firstly, a mesoscale Weather Research and Forecasting (WRF) mode was introduced in for high spatial resolution simulation of typhoon \"Megi\". Wind speed profile on the boundary layer of typhoon was gained through fitting based on nonlinear least squares and then it was integrated into the user-defined function (UDF) as an entry condition of small-scaled CFD numerical simulation. On this basis, a synchronous iterative modeling of wind field and sand particle combination was carried out by using a continuous phase and discrete phase. Influencing laws of typhoon and normal wind on moving characteristics of sand particles, equivalent pressure distribution mode of structural surface and characteristics of lift resistance coefficient were compared. Results demonstrated that: Compared with normal wind, mesoscale typhoon intensifies the 3D aerodynamic distribution mode on structural surface of wind turbine significantly. Different from wind loads, sand loads mainly impact on 30° ranges at two sides of the lower windward region on the tower. The ratio between sand loads and wind load reaches 3.937% and the maximum sand pressure coefficient is 0.09. The coupling impact effect of strong typhoon and large sand particles is more significant, in which the resistance coefficient of tower is increased by 9.80% to the maximum extent. The maximum resistance coefficient in typhoon field is 13.79% higher than that in the normal wind field.

Key Words
large wind turbine system; typhoon; WRF mode; mesoscale/small-scale coupling; wind-sand coupling movement; aerodynamic distribution

Address
Shitang Ke, Yifan Dong, Rongkuan Zhu and Tongguang Wang: Jiangsu Key Laboratory of Hi-Tech Research for Wind Turbine Design, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

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