scispace - formally typeset

Journal ArticleDOI

Flow behaviour and aeroacoustic characteristics of a simplified high-speed train bogie

01 Sep 2016-Vol. 230, Iss: 7, pp 1642-1658

AbstractAerodynamic noise becomes significant for high-speed trains and its prediction in an industrial context is difficult to achieve. The aerodynamic and aeroacoustic behaviour of the flow past a simplified high-speed train bogie at scale 1:10 is studied using a two-stage hybrid method comprising computational fluid dynamics and acoustic analogy. The near-field unsteady flow is obtained by solving the Navier-Stokes equations numerically with the delayed detached-eddy model and the results are used to predict the far-field noise through the Ffowcs Williams-Hawkings method. The sound radiated from the same scaled bogie model is measured in an anechoic open-jet wind tunnel. The aeroacoustic characteristics of tandem wheelsets are also investigated for comparison. It is found that the unsteady flow past the bogie is characterized by coherently alternating vortex shedding from the axles and more randomly distributed vortices of various scales and orientations from the wheels and frame. The vortices formed behind the upstream geometries are convected downstream and impinge on the downstream bodies, generating a highly turbulent wake behind the bogie. The noise predictions correspond fairly well with the experimental measurements for the dominant frequency of tonal noise and the shape of spectra. Vortex shedding from the axles generates the tonal noise with the dominant peak corresponding to the vortex shedding frequency. The directivity exhibits a dipole shape for the noise radiated from the bogie. Compared to the wheelsets of the bogie, the noise contribution from the bogie frame is relatively weaker.

Topics: Bogie (58%), Vortex shedding (58%), Noise (54%), Vortex (52%), Wind tunnel (51%)

Summary (2 min read)

1. Introduction

  • Over the last few decades, researches have been conducted regarding the source mechanisms of flow-induced noise, particularly in aerospace engineering for landing gears and airframes [1,2].
  • In contrast, modelling numerically some simplified geometries can reveal more details of the flow behaviour and the corresponding aeroacoustic mechanisms for some main noise-generating components of high-speed trains.
  • 4     DDES is an extension of the detached-eddy simulation (DES) method which combines the large-eddy simulation (LES) in the main flow region with the Reynolds-averaged Navier-Stokes (RANS) approach in the boundary layer region close to the solid objects.
  • The cell size on the axle surface is implemented as 0.42 mm around the perimeter and 0.88 mm in the spanwise direction.

4.1. Flow field

  • Fig. 3 visualizes the iso-surfaces of the second invariant of the velocity gradient 𝑄 to get an overview of the unsteady flow developed around the bogie.
  • Distinct features are observed in different regions of the flow field.
  • The flow separates from the upstream wheel front edges and interferes with the flow separated on the wheel tread; therefore, the coherent vortex shedding, seen behind the front axle, cannot be formed behind the front wheel and the wake developed there becomes fully three-dimensional.
  • For the point one axle radius above and behind the front axle in the mid-plane between the wheel inner surface and axle mid-span, a tonal peak appears in the spectrum at 324 Hz, as seen in Fig. 5(a).
  • A peak appears in the drag coefficient of the bogie and the front wheelset at 641 Hz, which is twice the frequency of the tonal peak in the lift coefficient while at a much lower amplitude.

4.3. Wall pressure fluctuations

  • Fig. 8 displays the wall fluctuating pressure level in decibels (𝐿! = 10log 𝑝!"/𝑝!"#!  , where 𝑝!"  is mean-square fluctuating pressure and  𝑝!"#  is reference acoustic pressure 20𝜇𝑃𝑎) on the bogie surface, which can be used to identify the potentially significant noise source regions.
  • This also indicates that the massive vortex shedding generated from the front axle may potentially be a major contributor to the noise radiated from the bogie.
  • Furthermore, the high pressure fluctuations can be seen around the downstream wheelset due to the flow impingement by the incoming vortex convected from the upstream geometry as well as the flow separation developed from the rear wheel front edges and the vortex shedding formed behind the rear axle.
  • Based on the near-field unsteady flow data obtained from the CFD calculations, the far-field noise signals can be predicted by the FW-H acoustic analogy using equivalent acoustic sources.
  • Additionally, equivalent circular-shaped receiver positions are defined in the horizontal x-z plane (the coordinates referred to Fig. 1).

5.1. Acoustic spectra computation

  • Flow statistics on lift and drag coefficients in Section 4.2 suggest that the flow transient is washed out after 0.1 s.
  • Moreover, compared with the experimental data, the tonal peak has a higher amplitude from the calculations in both cases.
  • The directivity of the noise radiated to far-field is calculated based on the OASPL determined from the PSD in the frequency range below 2 kHz.
  • Note that the similar directivity pattern of sound radiation occurs from the two cases with the slight difference of noise amplitudes between them, which also demonstrates that the wheelsets are the dominant noise sources of the bogie and the noise contribution from the bogie frame is relatively small.

6. Conclusions

  • The aerodynamic and aeroacoustic behaviour of the flow past a simplified bogie has been studied using the DDES model and FW-H acoustic analogy.
  • It is found that both streamwise and spanwise vortices are generated due to flow separation and vortex shedding around the bogie.
  • Furthermore, a vertical dipole pattern of noise radiation is predicted for the upstream wheelset; whereas the downstream wheelset has a multi-directional directivity pattern due to the lift and drag dipoles being aligned perpendicular to each other and its sound generation is relatively weaker.
  • These findings are helpful to understand the aerodynamic noise generating mechanisms from the bogie at full scale.
  • The turbulent inflow and the complex geometry will lead to complex flow structures and these will also affect the noise generation.

Did you find this useful? Give us your feedback

...read more

Content maybe subject to copyright    Report

Citations
More filters

Journal ArticleDOI
Abstract: The operation of high-speed trains in ice and snow weather results in a large amount of snow accumulation with ice on the bogies, which will pose a risk to the safety of high-speed trains. In this paper, the snow accumulating on the bogie has been investigated using a numerical simulation method based on the Realizable k - e turbulence model and Discrete Phase Model (DPM). The accuracy of mesh resolution and methodology of CFD was validated by the experimental results of wind tunnel tests. The DPM was used to investigate the mechanism of snow accumulation on the bogie by analysing the characteristics of movement of snow particles. Based on this analysis, two deflectors with the angles of 2.58° and 5.14° were designed, and the anti-snow effect of deflectors for the bogies was compared with numerical results. The results show that lots of snow particles underneath the bogie have direct impacts on the equipment of the bogie, causing massive snow accumulation on the bottom surface. A small amount of snow particles turn back to the region above the bogie from the rear cabin cover, which leads to little snow accumulation on the upper surface of the bogie. The number of particles accumulating on the bottom surface of the bogie is much more than that on the top. Application of deflectors with different angles can improve the anti-snow performance in the bogie region of high-speed trains. The deflector with an angle of 5.14° has the better anti-snow performance. It can reduce the snow accumulation on the whole bogie surfaces by 49.34%, while on the primary heat-producing devices, such as calipers and motors, by 42.47% and 47.40%, respectively.

21 citations


Journal ArticleDOI
Abstract: In this paper, the snow accumulation on the bogies of high-speed trains has been investigated using a numerical simulation method based on the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) coupled with the Discrete Phase Model (DPM). The effects of bogie cut outs’ shape, running speed of high-speed trains and snow particle density and diameter on the snow accumulation and particle movement characteristics are discussed. The results show that the bogie installation region with inclined plates shows better anti-snow performance than the configuration with straight plates, which greatly affects the flow structure and snow concentration distribution in the upper space of bogie regions. The running speed of high-speed trains has dominant effect on the snow accumulation on the bogies, and the snow accumulation issue of bogie becomes more serious with increasing running speed. Furthermore, the snow particle density and diameter also have large influence on the snow accumulation on the bogies. With the increase of snow particle density and diameter, the flow range at height direction around bogie region of snow particles become lower and the quality of snow accumulation decrease significantly.

19 citations


Journal ArticleDOI
Abstract: The aerodynamic behaviour of flow past a simplified high-speed train bogie including the ground underneath with ballast particles at scale 1:10 is studied numerically. It is found that the flow around the bogie is highly unsteady due to strong flow separations and flow interactions developed there. Generally, the ballast particles distributed inside the wheels are situated in the stronger turbulent flow and are subject to much higher aerodynamic forces than the particles located outside the wheels. Moreover, these aerodynamic forces increase when the ballast particles are located downstream of the bogie cavity and reach the peak values close to the bogie cavity trailing edge. The force time-series are produced based on the simulations of an array of the ballast particles in a wind-tunnel setup and it shows that the ballast flight is apt to happen as the rear part of the bogie cavity passing by the ballast bed. When the ballast particles become airborne, the fluctuating forces generated increase significantly. Therefore, the stronger unsteady flow developed around the bogie cavity, especially in the cavity trailing edge region, will produce larger fluctuating forces on the ballast particles, which will be more likely to cause ballast flights for high-speed railways.

18 citations


Journal ArticleDOI
17 Apr 2018
Abstract: Aerodynamic noise is a significant source for high-speed trains but its prediction in an industrial context is difficult to achieve. In this article, the flow and aerodynamic noise behaviour of a s...

14 citations


Cites methods from "Flow behaviour and aeroacoustic cha..."

  • ...A similar meshing strategy has been previously employed for the isolated wheelset and bogie cases in which good agreements were achieved between numerical simulations and experimental measurements for the radiated far-field noise.(8,9,12) The boundary conditions applied are as follows: the upstream inlet flow is represented as a steady uniform flow (U11⁄4 30m/s) with a low turbulence intensity....

    [...]


Journal ArticleDOI
TL;DR: A numerical study using IDDES is carried out to investigate the aerodynamic and the aeroacoustic response of a simplified ICE3 high-speed train model, focusing on the front part of the train and, in particular, on the first bogie cavity.
Abstract: A numerical study using IDDES is carried out to investigate the aerodynamic and the aeroacoustic response of a simplified ICE3 high-speed train model. The work focuses on the front part of the train and, in particular, on the first bogie cavity. The choice is justified by a literature survey which shows that this part of the train is the principal contributor of critical noise pollution created at pass-by in populated areas. Detailed CFD can provide useful insight and be of great importance in the identification of noise generation mechanisms and their relation with the flow structures. Results show the formation of two main aerodynamic structures with a clear relation to the aeroacoustic response calculated on the train and ground surfaces. Simulations were made at Re = 1 . 8 × 10 5 and M = 0.058 to match the experimental observations found in literature and generate a set of benchmark data for future investigations.

11 citations


References
More filters

Journal ArticleDOI
Abstract: A theory is initiated, based on the equations of motion of a gas, for the purpose of estimating the sound radiated from a fluid flow, with rigid boundaries, which as a result of instability contains regular fluctuations or turbulence. The sound field is that which would be produced by a static distribution of acoustic quadrupoles whose instantaneous strength per unit volume is ρv i v j + p ij - a 2 0 ρ δ ij , where ρ is the density, v i the velocity vector, p ij the compressive stress tensor, and a 0 the velocity of sound outside the flow. This quadrupole strength density may be approximated in many cases as ρ 0 v i v j . The radiation field is deduced by means of retarded potential solutions. In it, the intensity depends crucially on the frequency as well as on the strength of the quadrupoles, and as a result increases in proportion to a high power, near the eighth, of a typical velocity U in the flow. Physically, the mechanism of conversion of energy from kinetic to acoustic is based on fluctuations in the flow of momentum across fixed surfaces, and it is explained in § 2 how this accounts both for the relative inefficiency of the process and for the increase of efficiency with U . It is shown in § 7 how the efficiency is also increased, particularly for the sound emitted forwards, in the case of fluctuations convected at a not negligible Mach number.

4,380 citations


"Flow behaviour and aeroacoustic cha..." refers methods in this paper

  • ...The equivalent source terms under the integral sign are: Qi and Lij thickness and loading noise; Tij the Lighthill stress tensor.(16) Due to a low-Mach-number flow around the geometries, sound radiation from the quadrupole source (the last term in equation (3)) is neglected and Farassat’s Formulation 1A with an integral solver based on the retarded time approach was used to solve the FW–H equation....

    [...]


Journal ArticleDOI
Abstract: Monograph on sound generation by turbulence and surfaces in arbitrary motion, discussing sound and multipole fields and governing equations

2,771 citations


Journal ArticleDOI
Abstract: Detached-eddy simulation (DES) is well understood in thin boundary layers, with the turbulence model in its Reynolds-averaged Navier–Stokes (RANS) mode and flattened grid cells, and in regions of massive separation, with the turbulence model in its large-eddy simulation (LES) mode and grid cells close to isotropic. However its initial formulation, denoted DES97 from here on, can exhibit an incorrect behavior in thick boundary layers and shallow separation regions. This behavior begins when the grid spacing parallel to the wall Δ∥ becomes less than the boundary-layer thickness δ, either through grid refinement or boundary-layer thickening. The grid spacing is then fine enough for the DES length scale to follow the LES branch (and therefore lower the eddy viscosity below the RANS level), but resolved Reynolds stresses deriving from velocity fluctuations (“LES content”) have not replaced the modeled Reynolds stresses. LES content may be lacking because the resolution is not fine enough to fully support it, and/or because of delays in its generation by instabilities. The depleted stresses reduce the skin friction, which can lead to premature separation.

1,788 citations


Additional excerpts

  • ...DDES has been developed to avoid grid-induced separation and preserve the RANS mode throughout the boundary layer.(14)...

    [...]


15 Feb 2016
Abstract: Flow around circular cylinders , Flow around circular cylinders , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

470 citations


Book
11 Dec 2008
Abstract: Railways are an environmentally friendly means of transport well suited to modern society. However, noise and vibration are key obstacles to further development of the railway networks for high-speed intercity traffic, for freight and for suburban metros and light-rail. All too often noise problems are dealt with inefficiently due to lack of understanding of the problem. This book brings together coverage of the theory of railway noise and vibration with practical applications of noise control technology at source to solve noise and vibration problems from railways.

467 citations


"Flow behaviour and aeroacoustic cha..." refers background in this paper

  • ...It is generally accepted that aerodynamic noise becomes a significant problem for high-speed trains running at speeds over 300 km/h.(5,6) Considerable progress has been made in understanding the aerodynamic phenomena associated with high-speed trains....

    [...]


Frequently Asked Questions (2)
Q1. What have the authors contributed in "Flow behaviour and aeroacoustic characteristics of a simplified high-speed train bogie" ?

The aerodynamic and aeroacoustic behaviour of the flow past a simplified high-speed train bogie at scale 1:10 is studied using a two-stage hybrid method comprising computational fluid dynamics and acoustic analogy. 

Such factors need to be accounted for in future work.