Techno Press
Tp_Editing System.E (TES.E)
Login Search
You logged in as

was
 
CONTENTS
Volume 35, Number 2, August 2022
 


Abstract
When the rolling stocks run on the curve, the external rail has to be lifted to a certain level to balance the centrifugal force acting on the train body. Under such a situation, passengers may feel uncomfortable, and the slanted vehicle has the potential overturning risks at high speed. This paper conducted a wind tunnel test in an annular wind tunnel with φ =3.2 m based on a 1/20th scaled high-speed train (HST) model. The sensitivity of Reynolds effects ranging from Re = 0.37x106 to Re = 1.45x106 was tested based on the incoming wind from U=30 m/s to U=113 m/s. The wind speed covers the range from incompressible to compressible. The impact of roll angle ranging from γ =0° to γ =4° on train aerodynamics was tested. In addition, the boundary layer development was also analyzed under different wind speeds. The results indicate that drag and lift aerodynamic coefficients gradually stabilized and converged over U=70 m/s, which could be regeared as the self-similarity region. Similarly, the thickness of the boundary layer on the floor gradually decreased with the wind speed increase, and little changed over U=80 m/s. The rolling moment of the head and tail cars increased with the roll angle from γ =0° to γ =4°. However, the potential overturning risks of the head car are higher than the tail car with the increase of the roll angle. This study is significant in providing a reference for the overturning assessment of HST.

Key Words
aerodynamics; high-speed train; Reynolds number; roll angle; wind tunnel test

Address
Zhixiang Huang:China Aerodynamics Research and Development Center, Mianyang, China 621000, China

Wenhui Li:1)Key Laboratory of Traffic Safety on Track of Ministry of Education, School of Traffic & Transportation Engineering,
Central South University, Changsha 410075, China
2)Joint International Research Laboratory of Key Technology for Rail Traffic Safety, Changsha 410075, China
3)National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle, Changsha 410075, China

Tanghong Liu:1)Key Laboratory of Traffic Safety on Track of Ministry of Education, School of Traffic & Transportation Engineering,
Central South University, Changsha 410075, China
2)Joint International Research Laboratory of Key Technology for Rail Traffic Safety, Changsha 410075, China
3)National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle, Changsha 410075, China

Li Chen:China Aerodynamics Research and Development Center, Mianyang, China 621000, China


Abstract
Steel tubular towers are commonly used in UHV and long crossing transmission lines. By considering effects of the model scale, the solidity ratio and the ratio of the mean width to the mean height, wind tunnel tests under different wind speeds on twenty tubular steel tower body models and twenty-six tubular steel cross-arm models were completed. Drag coefficients and shielding factors of the experimental tower body models and cross-arm models in wind directional axis for typical skewed angles were obtained. The influence of the lift forces on the skewed wind load factors of tubular steel tower bodies was evaluated. The skewed wind load factors, the wind load distribution factors in transversal and longitudinal direction were calculated for the tubular tower body models and cross-arm models, respectively. Fitting expressions for the skewed wind load factors of tubular steel bodies and cross-arms were determined through nonlinear fitting analysis. Parameters for skewed wind loads determined by wind tunnel tests were compared with the regulations in applicable standards. Suggestions on the drag coefficients, the skewed wind load factors and the wind load distribution factors were proposed for tubular steel transmission towers.

Key Words
Reynolds number; skewed wind; transmission tower; tubular steel; wind tunnel test

Address
Fengli YANG:China Electric Power Research Institute, Xicheng District, Beijing 100055, China

Huawei NIU:Wind Engineering Research Center, Hunan University, Changsha 410082, Hunan Province, China

Abstract
The force coefficients of rotating plates in the acceleration stage will vary with rotation rate from 0 to stable rotation rate w0, which are important for quasi-steady theory of plate-like windborne debris to simulate the trajectory. In this paper, a wind tunnel experiment is carried out to study the effects of geometry and the Reynolds number on the variations of mean force coefficients of rotating plates. The rotational lift coefficients are sensitive to both geometry effect and Reynolds number effect, while the rotational drag and moment coefficients are only sensitive to geometry effect. In addition, new empirical formulas for the rotational lift coefficient and moment coefficients are proposed. Its accuracy is verified by comparing the predicted results with existing test data. Based on the experimental data of rotating plates, a new rotational force model for quasi-steady theory, which can be applied to a wider scope, is proposed to calculate the trajectory of plate-like windborne debris. The results show that the new model provides a better match with the tested trajectories than previous quasi-steady theories.

Key Words
autorotation; quasi-steady theory; rotational force model; trajectories; windborne debris

Address
Huatan Lin, Peng Huang and Ming Gu:State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China

Abstract
In this paper, the issue of pitch control in a vertical axis wind turbine was tackled. Programming the Actuator Cylinder model in MATLAB, a theoretical optimum pitch solution was found and then a classic four-bar mechanism was adapted to that theoretical solution to achieve a simple and elegant control of the pitch in the turbine. A simulation using the mechanism worked to find the optimum pitch cycles, where it was found that the mechanism would, in fact, increase the efficiency of the VAWT, by at least 11% and in the best case, over 35%. Another aspect that is studied is the possibility of selfstart of the turbine by only changing the pitch on the blades. This analysis, however, proved that a further individual pitch control must be used to surpass the cogging torque. All analyses conducted were done for a specific wind turbine that is 2 m2 in the swept area.

Key Words
AC model; angle of attack; optimum pitch; VAWT; self-start

Address
Mariana Montenegro-Montero:Instituto Tecnológico de Costa Rica, Provincia de Cartago, Cartago, 30101, Costarica

Gustavo Richmond-Navarro:Instituto Tecnológico de Costa Rica, Provincia de Cartago, Cartago, 30101, Costarica

Pedro Casanova-Treto:Unversidad de Costa Rica, Ciudad Universitaria Rodrigo Facio Brenes, San José, San Pedro, Costarica

Abstract
Tornadic wind flow is inherently turbulent. A turbulent wind flow is characterized by fluctuation of the velocity in the flow field with time, and it is a dynamic process that consists of eddy formation, eddy transportation, and eddy dissipation due to viscosity. Properly modeling turbulence significantly increases the accuracy of numerical simulations. The lack of a clear and detailed comparison between turbulence models used in tornadic wind flows and their effects on tornado induced pressure demonstrates a significant research gap. To bridge this research gap, in this study, two representative turbulence modeling approaches are applied in simulating real-world tornadoes to investigate how the selection of turbulence models affects the simulated tornadic wind flow and the induced pressure on structural surface. To be specific, LES with Smagorinsky-Lilly Subgrid and k-

Key Words
CFD; civil engineering; pressure; turbulence models; tornado; velocity

Address
Ryan Honerkamp:Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA

Zhi Li:Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA

Kakkattukuzhy M. Isaac:Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA

Guirong Yan:Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2022 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-2-736-6800 (SCS, EAS, WAS, ANR) +82-42-828-7995 (GAE, SEM, SSS, CAC) Fax : +82-2-736-6801, Email: info@techno-press.com