Vortex-induced vibration of a truss girder with high vertical stabilizers

2018 ◽  
Vol 22 (4) ◽  
pp. 948-959 ◽  
Author(s):  
Haojun Tang ◽  
KM Shum ◽  
Qiyu Tao ◽  
Jinsong Jiang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Vortex Shedding ◽  
Windward Side ◽  
Induced Response ◽  
Vortex Induced Vibration ◽  
Wind Tunnel Tests ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

To improve the flutter stability of a long-span suspension bridge with steel truss stiffening girder, two vertical stabilizers of which the total height reaches to approximately 2.9 m were planned to install on the deck. As the optimized girder presents the characteristics of a bluff body more, its vortex-induced vibration needs to be studied in detail. In this article, computational fluid dynamics simulations and wind tunnel tests are carried out. The vortex-shedding performance of the optimized girder is analyzed and the corresponding aerodynamic mechanism is discussed. Then, the static aerodynamic coefficients and the dynamic vortex-induced response of the bridge are tested by sectional models. The results show that the vertical stabilizers could make the incoming flow separate and induce strong vortex-shedding behind them, but this effect is weakened by the chord member on the windward side of the lower stabilizer. As the vortex-shedding performance of the optimized girder is mainly affected by truss members whose position relationships change along the bridge span, the vortex shed from the girder can hardly have a uniform frequency so the possibility of vortex-induced vibration of the bridge is low. The data obtained by wind tunnel tests verify the results by computational fluid dynamics simulations.

On the aerodynamic characteristics of stay cables attached with helical wires

2017 ◽  
Vol 21 (9) ◽  
pp. 1262-1272 ◽  
Author(s):  
Shouying Li ◽  
Yangchen Deng ◽  
Wei Zhong ◽  
Zhengqing Chen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Vortex Shedding ◽  
Aerodynamic Characteristics ◽  
Wind Tunnel Tests ◽  
Stay Cables ◽  
Computational Fluid Dynamics Simulations ◽  
The Mean ◽  
Dynamics Simulations

To investigate the aerodynamic characteristics of stay cables attached with helical wires, a series of wind tunnel tests and computational fluid dynamics simulations were both carried out on the smooth and helical-wire cable models. The diameters of helical wires include 2, 3, and 4 mm, and the distances between adjacent helical wires include 200, 300, and 600 mm. Pressure taps were uniformly arranged on seven cross sections of the cable models. First, wind tunnel tests including 50 test cases were conducted to measure the wind forces and wind pressures on the cables using the forced vibration system in HD-2 wind tunnel. The effects of the helical wires on the mean and fluctuating aerodynamic forces and the correlation coefficients along the cable axis were investigated in detail based on the experimental data. Second, large Eddy simulation module incorporated in software FLUENT® was used to simulate the aerodynamic forces on the smooth and helical-wire cables. The parameters of the cable and the helical wire are similar to those used in the wind tunnel tests. The results show that helical wires can attenuate vortex shedding and reduce the wind pressure correlation along the cable axis. Within the Reynolds number range from 0.4 × 105 to 1.6 × 105, the mean drag force of the helical-wire cable is lower than the value of the smooth cable, and the correlation coefficient decreases with the increase in wind velocity. The results obtained from wind tunnel tests and computational fluid dynamics simulations agree well with each other. Furthermore, the wind velocity contour around the helical-wire cables obtained from computational fluid dynamics simulations visually indicates that the approaching flow is forced to separate at the surface of the helical wire in advance, which makes the vortex shedding disorder along the cable axis.

scholarly journals Impact of wheel rotation on the aerodynamic drag of a time trial cyclist

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
Fabio Malizia ◽  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Aerodynamic Drag ◽  
Front Wheel ◽  
Wind Tunnel Tests ◽  
Wheel Rotation ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Drag Area

AbstractAerodynamic drag is the main resistive force in cycling at high speeds and on flat terrain. In wind tunnel tests or computational fluid dynamics simulations, the aerodynamic drag of cycling wheels is often investigated isolated from the rest of the bicycle, and sometimes in static rather than rotating conditions. It is not yet clear how these testing and simulating conditions influence the wheel aerodynamic performance and how the inclusion of wheel rotation influences the overall measured or computed cyclist drag. This study presents computational fluid dynamics simulations, validated with wind tunnel tests, that indicate that an isolated static spoked front wheel has a 2.2% larger drag area than the same wheel when rotating, and that a non-isolated static spoked front wheel has a 7.1% larger drag area than its rotating counterpart. However, rotating wheels are also subjected to the rotational moment, which increases the total power required to rotate and translate the wheel compared to static conditions where only translation is considered. The interaction with the bicycle frame and forks lowers the drag area of the front wheel by 8.8% for static and by 12.9% for the rotating condition, compared to the drag area of the isolated wheels. A different flow behavior is also found for static versus rotating wheels: large low-pressure regions develop from the hub for rotating wheels, together with a lower streamwise velocity region inside the circumference of the wheel compared to static wheels. The results are intended to help in the selection of testing/simulating methodologies for cycling spoked wheels.

Computational Fluid Dynamics Simulations of the Container Express as a Helicopter Slung Load

2003 ◽  
Author(s):  
Misty G. Berry
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Practical Applications ◽  
Rectangular Cylinder ◽  
Wind Tunnel Data ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Flow over rectangular boxes and cylinders has not been well studied, and yet has numerous practical applications. This bluff-body geometry causes immediate flow separation and periodic vortex shedding in the wake of the object, regardless of Reynolds number. This paper presents the use and verification of a CFD methodology for predicting the forces on a particular rectangular cylinder—a slung load cargo container known as a Container Express (CONEX). It presents a comparison of the numerically obtained forces to wind tunnel data for the CONEX that demonstrates ranges of validity for the simulations. These comparisons give confidence for force and moment results for CONEX and vertical stabilizer simulations. The forces and moments will be used to design a mounting system for the vertical stabilizer.

scholarly journals Wind-Induced Phenomena in Long-Span Cable-Supported Bridges: A Comparative Review of Wind Tunnel Tests and Computational Fluid Dynamics Modelling

2021 ◽  
Vol 11 (4) ◽  
pp. 1642
Author(s):  
Yuxiang Zhang ◽  
Philip Cardiff ◽  
Jennifer Keenahan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Careful Analysis ◽  
Wind Effects ◽  
Wind Tunnel Tests ◽  
Long Span Bridges ◽  
Long Span ◽  
Comparative Review ◽  
Dynamics Modelling

Engineers, architects, planners and designers must carefully consider the effects of wind in their work. Due to their slender and flexible nature, long-span bridges can often experience vibrations due to the wind, and so the careful analysis of wind effects is paramount. Traditionally, wind tunnel tests have been the preferred method of conducting bridge wind analysis. In recent times, owing to improved computational power, computational fluid dynamics simulations are coming to the fore as viable means of analysing wind effects on bridges. The focus of this paper is on long-span cable-supported bridges. Wind issues in long-span cable-supported bridges can include flutter, vortex-induced vibrations and rain–wind-induced vibrations. This paper presents a state-of-the-art review of research on the use of wind tunnel tests and computational fluid dynamics modelling of these wind issues on long-span bridges.

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