The slipstream and wake of a high-speed train

2001 ◽  
Vol 215 (2) ◽  
pp. 83-99 ◽  
Author(s):  
C. J. Baker ◽  
S. J. Dalley ◽  
T Johnson ◽  
A Quinn ◽  
N. G. Wright
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Scale Model ◽  
Upstream Region ◽  
Wake Region ◽  
High Speed Train ◽  
Near Wake ◽  
Time Histories ◽  
Layer Region ◽  
Particle Imaging

This paper describes the results of experimental work to determine the structure of the slipstream and wake of a high speed train. The experiments were carried out using a 1/25th scale model of a four-coach train on a moving model rig (MMR). Flow velocities were measured using a rake of single hot films positioned close to the model side or roof. Tests were carried out at different model speeds, with and without the simulation of a crosswind. Velocity time histories for each configuration were obtained from ensemble averages of the results of a number of runs. A small number of particle imaging velocimetry (PIV) experiments were also carried out, and a wavelet analysis revealed details of the unsteady flow structure around the vehicle. It was shown that the flowfield around the vehicle could be divided into a number of different regions of distinct flow characteristics: an upstream region, a nose region, a boundary layer region, a near wake region and a far wake region. If the results were suitably normalized, the effect of model speed was small. The effect of crosswinds was to add an increment to the slipstream and wake velocities, and this resulted in very high slipstream velocities in the nose region.

Passenger Train Slipstream Characterization Using a Rotating Rail Rig

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
N. Gil ◽  
C. J. Baker ◽  
C. Roberts ◽  
A. Quinn
Keyword(s):  
Boundary Layer ◽  
Turbulence Intensity ◽  
High Speed ◽  
Scale Model ◽  
High Speed Train ◽  
Measuring Time ◽  
Displacement Thickness ◽  
Time Histories ◽  
Attached Flow ◽  
Good Agreement

This paper presents the results of a new experimental technique to determine the structure of train slipstreams. The highly turbulent, nonstationary nature of the slipstreams make their measurement difficult and time consuming as in order to identify the trends of behavior several passings of the train have to be made. This new technique has been developed in order to minimize considerably the measuring time. It consists of a rotating rail rig to which a 1/50 scale model of a four car high speed train is attached. Flow velocities were measured using two multihole Cobra probes, positioned close to the model sides and top. Tests were carried out at different model speeds, although if the results were suitably normalized, the effect of model speed was not significant. Velocity time histories for each configuration were obtained from ensemble averages of the results of a large number of runs (of the order of 80). From these it was possible to define velocity and turbulence intensity contours along the train, as well as the displacement thickness of the boundary layer, allowing a more detailed analysis of the flow. Also, wavelet analysis was carried out on different runs to reveal details of the unsteady flow structure around the vehicle. It is concluded that, although this methodology introduces some problems, the results obtained with this technique are in good agreement with previous model and full scale measurements.

Effect of different typical high speed train pantograph recess configurations on aerodynamic noise

2020 ◽  
pp. 095440972094751
Author(s):  
Hogun Kim ◽  
Zhiwei Hu ◽  
David Thompson
Keyword(s):  
Unsteady Flow ◽  
High Speed ◽  
Flow Characteristics ◽  
Vortical Flow ◽  
Aerodynamic Noise ◽  
Upstream Region ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Noise Sources ◽  
Cavity Configuration

For high-speed trains, the aerodynamic noise becomes an essential consideration in the train design. The pantograph and pantograph recess are recognised as important sources of aerodynamic noise. This paper studies the flow characteristics and noise contributions of three typical high-speed train roof configurations, namely a cavity, a ramped cavity and a flat roof with side insulation plates. The Improved Delayed Detached-Eddy Simulation approach is used for the flow calculations and the Ffowcs Williams & Hawkings aeroacoustic analogy is used for far-field acoustic predictions. Simulations are presented for a simplified train body at 1/10 scale and 300 km/h with these three roof configurations. In each case, two simplified pantographs (one retracted and one raised) are located on the roof. Analysis of the flow fields obtained from numerical simulations clearly shows the influence of the train roof configuration on the flow behaviour, including flow separations, reattachment and vortex shedding, which are potential noise sources. A highly unsteady flow occurs downstream when the train roof has a cavity or ramped cavity due to flow separation at the cavity trailing edge, while vortical flow is generated by the side insulation plates. For the ramped cavity configuration, moderately large pressure fluctuations appear on the cavity outside walls in the upstream region due to unsteady flow from the upstream edge of the plate. The raised pantograph, roof cavity, and ramped cavity are identified as the dominant noise sources. When the retracted pantograph is located in the ramped roof cavity, its noise contribution is less important. Furthermore, the insulation plates also generate tonal components in the noise spectra. Of the three configurations considered, the roof cavity configuration radiates the least noise at the side receiver in terms of A-weighted level.

An improved delayed detached eddy simulation study of the bogie cavity length effects on the aerodynamic performance of a high-speed train

2020 ◽  
Vol 234 (12) ◽  
pp. 2386-2401 ◽  
Author(s):  
Jiabin Wang ◽  
Guglielmo Minelli ◽  
Yan Zhang ◽  
Jie Zhang ◽  
Sinisa Krajnović ◽  
...  
Keyword(s):  
High Speed ◽  
Cavity Length ◽  
Longitudinal Vortex ◽  
Resistance Force ◽  
Wake Region ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Near Wake ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

This paper uses an improved delayed detached eddy simulation method to investigate the unsteady flow features of the high-speed trains with various cavity lengths at Re = 1.85×106. The improved delayed detached eddy simulation results are validated against the experimental data obtained during previous wind tunnel tests. The effects of cavity length on the resistance force, flow structures beneath the high-speed train and in the wake are analyzed. The results show that a longer cavity significantly increases the streamwise velocity level near the rear plates and forms a stronger impinging flow on the rear plates, and thus contributes to a higher value of resistance. Furthermore, a longer cavity decreases the pressure coefficients around the near wake region from the top of the ballast to the tail nose in the vertical direction and thereby increases the pressure drag of the high-speed train. Additionally, a longer bogie cavity is found to increase the longitudinal vortex scales in the near wake region. All these changes on the flow field bring to 5.8% and 11.5% drag increase when the bogie cavities are elongated by 20% and 40%, respectively, of the wheelbase.

Investigation of speech privacy in high-speed train cabins using a 1:10 scale model

2014 ◽  
Vol 135 (4) ◽  
pp. 2365-2365
Author(s):  
Hansol Lim ◽  
Hyung Suk Jang ◽  
Jin Yong Jeon
Keyword(s):  
High Speed ◽  
Scale Model ◽  
High Speed Train

Wind Tunnel Tests on Flow Characteristics of the KRISO 3,600 TEU Containership and 300K VLCC Double-Deck Ship Models

2003 ◽  
Vol 47 (01) ◽  
pp. 24-38 ◽  
Author(s):  
Sang-Joon Lee ◽  
Hak-Rok Kim ◽  
Wu-Joan Kim ◽  
Suak-Ho Van
Keyword(s):  
Wind Tunnel ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Spatial Distributions ◽  
Wake Region ◽  
Turbulence Statistics ◽  
Near Wake ◽  
Mean Velocity ◽  
Freestream Velocity ◽  
Longitudinal Vortices

The flow characteristics in the stern and near-wake region of two ship models, the Korea Research Institute of Ships and Ocean Engineering (KRISO) 3,600 TEU containership (KCS) and the KRISO 300K very large crude oil carrier (VLCC) (KVLCC), were investigated experimentally. The double-deck ship models were installed in a subsonic wind tunnel. The freestream velocity was fixed at Uo = 25 m/s, and the corresponding Reynolds numbers based on the model length (Lpp) were about 3.3x 106 and 4.6x 106for the KCS and KVLCC models, respectively. The spatial distributions of mean velocity components and turbulence statistics, including turbulence intensities, Reynolds shear stresses, and turbulent kinetic energy, were measured using a hot-wire anemometer. For both ship models, the stern flow and near-wake show very complicated three-dimensional flow patterns. The longitudinal vortices formed in the stern region dominantly influence the flow structure in the near-wake region. In the region of main longitudinal vortices, the mean velocity deficits and all turbulence statistics have large values, compared with the surrounding flow. As the flow moves downstream, the turbulence statistics increase and have maximum values at the after-perpendicular (AP) plane and then decrease gradually due to the expansion of the shear layer. For the KVLCC model, the spatial distributions of mean velocity components and turbulence intensities behind the propeller plane clearly show hook-shaped contours. These experimental results, especially the turbulence statistics, can be used not only to understand the flows around modern practical hull forms but also to validate the computational fluid dynamics codes and turbulence models. The complete experimental data set is available on the website (http://www.postech.ac.kr/me/efml/data).

Effects of ground configurations on the slipstream and near wake of a high-speed train

2017 ◽  
Vol 168 ◽  
pp. 177-189 ◽  
Author(s):  
Chao Xia ◽  
Hanfeng Wang ◽  
Xizhuang Shan ◽  
Zhigang Yang ◽  
Qiliang Li
Keyword(s):  
High Speed ◽  
High Speed Train ◽  
Near Wake

Aerodynamics of a scale model of a high-speed train on a streamlined deck in cross winds

2019 ◽  
Vol 91 ◽  
pp. 102717 ◽  
Author(s):  
Huan Li ◽  
Xuhui He ◽  
Hanfeng Wang ◽  
Ahsan Kareem
Keyword(s):  
High Speed ◽  
Scale Model ◽  
High Speed Train

scholarly journals Vertical vibrations of composite bridge/track structure/high-speed train systems. Part 3: Deterministic and random vibrations of exemplary system

2014 ◽  
Vol 62 (2) ◽  
pp. 305-320 ◽  
Author(s):  
M. Podworna ◽  
M. Klasztorny
Keyword(s):  
High Speed ◽  
Extreme Values ◽  
Track Structure ◽  
Vertical Acceleration ◽  
Computer Algorithms ◽  
High Speed Train ◽  
Random Factor ◽  
Static And Dynamic Analysis ◽  
Time Histories ◽  
Vertical Vibrations

Abstract Based on the one-dimensional quasi-exact physical and mathematical modelling of a composite (steel-concrete) bridge/track structure/high-speed train system (BTT), developed in Part 2, advanced computer algorithms for the BTT numerical modelling and simulation as well as a computer programme to simulate vertical vibrations of BTT systems are developed. The exemplary bridge under numerical quasi-static and dynamic analysis, designed according to Polish standards, has a 15.00 m span length and belongs to the SCB series-of-types developed in Part 1. The bridge is loaded by a German ICE-3 high-speed train moving at the resonant and maximum operating speeds. A continuously welded ballasted track structure adapted to high operating velocities is applied. The output quantities include: time-histories of the vertical deflection of the main beams at the midspan, time-histories of the longitudinal normal stress in the bottom fibres of the main beams at the midspan, time-histories of the vertical acceleration of the bridge deck at the midspan, time-histories of the vertical accelerations of the suspension pivots in car-bodies, time-histories of the dynamic pressures of the wheel sets of moving rail-vehicles. The design quantities, understood as the extreme values of the output quantities, are used to verify the design conditions. The basic random factor, i.e. vertical track irregularities of the track, is taken into consideration. Basic statistics of the design quantities treated as random variables are calculated and taken into account in the design conditions.

scholarly journals Turbulent Wake-Flow Characteristics in the Near Wake of Freely Flying Raptors: A Comparative Analysis Between an Owl and a Hawk

2020 ◽  
Vol 60 (5) ◽  
pp. 1109-1122 ◽  
Author(s):  
Krishnamoorthy Krishnan ◽  
Hadar Ben-Gida ◽  
Gareth Morgan ◽  
Gregory A Kopp ◽  
Christopher G Guglielmo ◽  
...  
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Flow Characteristics ◽  
Wake Flow ◽  
Flight Behavior ◽  
Aerodynamic Noise ◽  
Particle Image Velocimetry System ◽  
Near Wake ◽  
Time Resolved ◽  
Turbulent Characteristics

Synopsis Owl flight has been studied over multiple decades associated with bio-inspiration for silent flight. However, their aerodynamics has been less researched. The aerodynamic noise generated during flight depends on the turbulent state of the flow. In order to document the turbulent characteristics of the owl during flapping flight, we measured the wake flow behind a freely flying great horned owl (Bubo virginianus). For comparison purposes, we chose to fly a similar-sized raptor a Harris’s hawk (Parabuteo unicinctus): one is nocturnal and the other is a diurnal bird of prey. Here, we focus on the wake turbulent aspects and their impact on the birds’ flight performances. The birds were trained to fly inside a large-scale wind tunnel in a perch-to-perch flight mode. The near wake of the freely flying birds was characterized using a long duration time-resolved particle image velocimetry system. The velocity fields in the near wake were acquired simultaneously with the birds’ motion during flight which was sampled using multiple high-speed cameras. The turbulent momentum fluxes, turbulent kinetic energy production, and dissipation profiles are examined in the wake and compared. The near wake of the owl exhibited significantly higher turbulent activity than the hawk in all cases, though both birds are similar in size and followed similar flight behavior. It is suggested that owls modulate the turbulence activity of the near wake in the vicinity of the wing, resulting in rapid decay before radiating into the far-field; thus, suppressing the aerodynamic noise at the far wake.

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