scholarly journals Aerodynamics of a Train and Flat Closed-Box Bridge System with Train Model Mounted on the Upstream Track

2021 ◽  
Vol 12 (1) ◽  
pp. 276
Author(s):  
Hui Wang ◽  
Huan Li ◽  
Xuhui He
Keyword(s):  
Reynolds Number ◽  
Bridge Deck ◽  
Shielding Effect ◽  
Flow Transition ◽  
Railway Bridge ◽  
Aerodynamic Forces ◽  
Promoting Effect ◽  
Highly Sensitive ◽  
Stall Angle ◽  
Bridge System

The aerodynamic features of a train and flat closed-box bridge system may be highly sensitive to train-bridge aero interactions. For the generally utilized railway bridge-deck with two tracks (the upstream and downstream ones), the aero interactions above are occupied-track-dependent. The present paper thus aims to reveal the aero interactions stated above via a series of wind tunnel tests. The results showed that the aero interactions of the present train-bridge system display four typical behaviors, namely, the underbody flow restraining effect, bridge deck shielding effect, flow transition promoting effect, and the flow separation intensifying effect. The above four aero interactions result in obvious reductions in the aerodynamic forces of the train in wind angle of attack α of [−4°, 12°] and in the static stall angle of the bridge-deck, and leads to sensible increases in the absolute values of the bridge aerodynamic forces in α of [−4°, 12°]. Upon comparing the results with the same train and bridge system but with the train model mounted on the downstream track, the quasi-Reynolds number effect was non-detectable when the train model was moved to the upstream track. Thus, no drag crisis and other saltatory aerodynamic behaviors were observed in the present study in α of [0°, 12°].

Aerodynamics of a two-dimensional bluff body with the cross-section of a train

2020 ◽  
Vol 23 (12) ◽  
pp. 2679-2693 ◽  
Author(s):  
Huan Li ◽  
Xuhui He ◽  
Hanfeng Wang ◽  
Si Peng ◽  
Shuwei Zhou ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Large Amplitude ◽  
High Speed ◽  
Bluff Body ◽  
Mean Amplitude ◽  
Two Dimensional ◽  
Aerodynamic Forces ◽  
Moderate Reynolds Number ◽  
Amplitude Mode

Experiments on the aerodynamics of a two-dimensional bluff body simplified from a China high-speed train in crosswinds were carried out in a wind tunnel. Effects of wind angle of attack α varying in [−20°, 20°] were investigated at a moderate Reynolds number Re = 9.35 × 104 (based on the height of the model). Four typical behaviors of aerodynamics were identified. These behaviors are attributed to the flow structure around the upper and lower halves of the model changing from full to intermittent reattachment, and to full separation with a variation in α. An alternate transition phenomenon, characterized by an alteration between large- and small-amplitude aerodynamic fluctuations, was detected. The frequency of this alteration is about 1/10 of the predominant vortex shedding. In the intervals of the large-amplitude behavior, aerodynamic forces fluctuate periodically with a strong span-wise coherence, which are caused by the anti-symmetric vortex shedding along the stream-wise direction. On the contrary, the aerodynamic forces fluctuating at small amplitudes correspond to a weak span-wise coherence, which are ascribed to the symmetric vortex shedding from the upper and lower halves of the model. Generally, the mean amplitude of the large-amplitude mode is 3 times larger than that of the small one. Finally, the effects of Reynolds number were examined within Re = [9.35 × 104, 2.49 × 105]. Strong Reynolds number dependence was observed on the model with two rounded upper corners.

scholarly journals Application of welded studs for fastening of railway bridge deck

2015 ◽  
Vol 2015 (1) ◽  
pp. 35-42
Author(s):  
V.V. Knysh ◽  
◽  
S.A. Solovej ◽  
A.A. Grishanov ◽  
G.O. Linnik ◽  
...  
Keyword(s):  
Bridge Deck ◽  
Railway Bridge

Effects of Cyclist Size and Position Within Formations on Drag and Side Force in the Presence of Cross Winds

2019 ◽  
Author(s):  
Ivaylo Nedyalkov ◽  
Alec Cunningham ◽  
Adam Lovell
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Reduction ◽  
Aerodynamic Forces ◽  
Side Force ◽  
Scale Models ◽  
Force Reduction

Abstract In the absence of cross-winds, a cyclist can expend up to 90% of their energy to overcome drag and can save up to 30% of that energy if riding behind another cyclist. The aerodynamic forces acting on cyclists in the presence of cross wind have not been studied in much detail. The effect of the offset distances between cyclists on the aerodynamic forces has been investigated in the literature for configurations of two cyclists. In the present study, 1:11 scale models of two different cyclists were rapid-prototyped and tested in a wind tunnel. The effect of the size of the cyclist was studied by placing the larger cyclist model behind the smaller one; the smaller behind the larger one; and the larger model behind an identical (larger model) copy. The effect of position within the group was studied by measuring the forces on each of the four cyclists placed in a favorable formation. The results suggest that the size of the cyclist matters, particularly when the leading cyclist is smaller than the drafting cyclist, and the effect is more prominent for the side forces. The results also show that in a formation of four cyclists, the leading cyclist experiences minor drag reduction compared to riding alone. The second and third cyclists experience the largest force reductions within the group, and the fourth cyclist experiences force reduction, which is not as significant. The results appear to be dependent on the Reynolds number, but may still be valuable for racing strategies and recreational cycling.

Field and numerical investigation of the effect of under-sleeper pads on the dynamic behavior of railway bridges

2018 ◽  
Vol 232 (8) ◽  
pp. 2126-2137 ◽  
Author(s):  
Jaber Mottahed ◽  
Jabbar A Zakeri ◽  
Saeed Mohammadzadeh
Keyword(s):  
Numerical Investigation ◽  
Dynamic Behavior ◽  
Field Experiments ◽  
Bridge Deck ◽  
Numerical Models ◽  
Bridge Decks ◽  
Span Length ◽  
Railway Bridge ◽  
Railway Bridges ◽  
Northern District

There is a growing need to minimise vibrations of railway structures, especially the railway bridges, due to the increasing speed of trains. Various methods are used to reduce the effects of vibration on bridges. One of the methods is using under-sleeper pads. In this study, a real railway bridge – located in the northern district of Iran – with two spans and a free span length of 7 m was selected for the investigation of the effect of under-sleeper pads on the reduction of vibrations imposed on railway bridges. Field experiments – including the installation of an accelerometer to measure the accelerations beneath bridge decks, on the rail web, and next to the sleeper, and also the installation of Linear variable differential transformers (LVDTs) to measure the displacements of midspan point of bridge decks – were conducted. The effect of under-sleeper pads on the reduction of vibration accelerations, displacements, and moments of bridge midspan was investigated by developing numerical models of the bridge and validating its results through experimental outputs. The modeling predicts that the reduction of acceleration imposed on the deck in the first and second spans was different; the reduction effects in the first span were higher, where there was 58% reduction after using under-sleeper pads beneath the sleepers. There was a 15% decrease in the displacement of the bridge deck when under-sleeper pads are used. Similar results were obtained for the midspan moment of the bridge which reduced by 16%.

scholarly journals Experimental Analysis of Stiffness of the Riveted Steel Railway Bridge Deck Members’ Joints

2014 ◽  
Vol 10 (2) ◽  
pp. 105-110
Author(s):  
Jozef Gocál ◽  
Richard Hlinka ◽  
Jozef Jošt ◽  
František Bahleda
Keyword(s):  
Stress Response ◽  
Experimental Analysis ◽  
Bridge Deck ◽  
Bending Stiffness ◽  
Traffic Load ◽  
Structural Members ◽  
Railway Bridge ◽  
The Real ◽  
Steel Railway Bridge ◽  
Main Girder

Abstract The paper deals with the real behaviour of the riveted steel railway bridge deck members’ connections with respect to their bending stiffness. Attention is paid to the stringer-to-cross beam connection as well as the cross beam-to-main girder connection. The stiffness of the two connections is investigated on the basis of evaluation of the experimentally determined stress response of the observed structural members to the actual traffic load on an existing railway bridge.

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