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
