Bogie Cavity Research Articles

The Influence of bogie cavity bottom plate on the aerodynamic noise characteristics of high speed trains

The bogie area with a complex structure is an extremely important source of noise for trains. Based on the large-eddy simulation(LES) and Ffowcs Williams-Hawkings(FW-H) analogy, aero-acoustic simulation was conducted on a 3-car high-speed train of a certain type with a bogie cavity bottom plate installed on the front and rear cars. The results show that bottom plate changes the flow field around the bogie, weakens the flow separation of airflow at the leading edge of the bogie cavity, mitigates the flow impact of airflow on various components of the bogie, suppresses the formation and detachment of large-scale vortices in the bogie area, and reduces the formation of pressure pulsations on the geometric surface of the bogie area. The bogie cavity bottom plate scheme reduces the far-field aerodynamic noise of the train by 1.63dBA, and the noise reduction effect is significant. The aerodynamic noise of the measurement point equipped with a bogie cavity bottom plate is lower than that of the conventional bogie cavity in all frequency bands, and the energy reduction is more significant at medium and low frequencies.

Validation of numerical method of unsteady Reynolds-averaged Navier–Stokes coupled with discrete phase model and optimization for the snow-resistance performance of bogies of a high-speed train

This paper presents an investigation aimed at enhancing the snow resistance of bogies in a three-car grouped alpine high-speed train (HST) that operates in a snowy region. The study employs a combination of the unsteady Reynolds-averaged Navier–Stokes model, coupled with the discrete phase model. This modeling approach has been validated through wind tunnel tests, including flow field tests, two-phase flow tests, and snow-ice tests. The study comprehensively compares the characteristics of the wind-snow flow, spatial snow concentration, and the distribution of snow on the train's underbody between two scenarios: the original train's underbody structure and the multifactor collaborative optimization scheme (MCOS). The results indicate that the MCOS case facilitates the escape of snow particles from the bogie cavities by weakening the upward and reverse flows. Furthermore, the MCOS case significantly reduces the concentration of snow particles around the heat-producing elements and decreases the accumulation of snow on both the lower and upper surfaces of the bogies. As a result, it reduces snow accumulation on the bogies by 50.6%, 56.4%, 60.8%, and 62.4% at train speeds of 200, 250, 300, and 350 km/h, respectively. In summary, this research provides valuable insights for improving the snow resistance of HSTs operating in snowy regions, with potential applications in enhancing railway transportation safety and efficiency.

Flow and sound fields of scaled high-speed trains with different coach numbers running in long tunnel

Segregated incompressible large eddy simulation and acoustic perturbation equations were used to obtain the flow field and sound field of 1:25 scale trains with three, six and eight coaches in a long tunnel, and the aerodynamic results were verified by wind tunnel test with the same scale two-coach train model. Time-averaged drag coefficients of the head coach of three trains are similar, but at the tail coach of the multi-group trains it is much larger than that of the three-coach train. The eight-coach train presents the largest increment from the head coach to the tail coach in the standard deviation (STD) of aerodynamic force coefficients: 0.0110 for drag coefficient (Cd), 0.0198 for lift coefficient (Cl) and 0.0371 for side coefficient (Cs). Total sound pressure level at the bottom of multi-group trains presents a significant streamwise increase, which is different from the three-coach train. Tunnel walls affect the acoustic distribution at the bottom, only after the coach number reaches a certain value, and the streamwise increase in the sound pressure fluctuation of multi-group trains is strengthened by coach number. Fourier transform of the turbulent and sound pressures presents that coach number has little influence on the peak frequencies, but increases the sound pressure level values at the tail bogie cavities. Furthermore, different from the turbulent pressure, the first two sound pressure proper orthogonal decomposition (POD) modes in the bogie cavities contain 90% of the total energy, and the spatial distributions indicate that the acoustic distributions in the head and tail bogies are not related to coach number.

Research on snow prevention in the bogie region based on active blowing method

To reduce excessive snow accumulation on bogie surfaces during high-speed train operations in cold regions, two active blowing schemes are designed in this study based on the shape of the bogie cavity and the relative position of the brake caliper. The unsteady Reynolds-averaged Navier–Stokes algorithm coupled with a discrete phase model was used to calculate the airflow and snow flow under the train. Moreover, the algorithm is employed to explore the impact of active blowing on the flow field characteristics and snow accumulation in the bogie region. Results show that active blowing changes the upward airflow in the bogie region, causing air at the bottom of the train to flow outwards, carrying off numerous snow particles from the bogie region. Active blowing accelerates the surface friction velocity on the bogie, increases the shear force on snow particles, and effectively reduces the snow accumulation on the bogie surface. The foregoing observation indicates that active blowing has considerable potential for snow accumulation prevention.

Effect of Bogie Cavity End Wall Inclination on Flow Field and Aerodynamic Noise in the Bogie Region of High-Speed Trains

Effect of Bogie Cavity End Wall Inclination on Flow Field and Aerodynamic Noise in the Bogie Region of High-Speed Trains

Aerodynamic noise from a high-speed train bogie with complex geometry under a leading car

Among the various aerodynamic noise sources associated with high-speed trains, the bogie regions, and particularly the leading bogie, contribute most to the overall noise. To control this noise, insight into the noise generation mechanisms is imperative but relevant studies are limited due to the difficulties of simulating the flow in regions with complex geometry. An investigation is presented of the aerodynamic noise from a bogie under the leading car of a high-speed train using Delayed Detached Eddy Simulation method. A hybrid grid system is utilized to simulate the flow field, which provides input for the far-field noise calculations based on the Ffowcs Williams and Hawkings equation. Analysis shows that the outer bogie components experience large pressure fluctuations as they are immersed in the shear layer detached from upstream, which is therefore identified as playing a critical role in the noise generation. The resulting noise spectra are broadband and dominated by low frequencies. Compared with the bogie, the bogie cavity and train nose emit 5 dB greater sound power for the current geometry. This study improves understanding of the mechanisms behind the generation of aerodynamic noise in train bogies and lays the foundations for future studies of train bogie noise reduction.

Impact of bogie fairing configuration on the aerodynamic performance of high-speed train under crosswind

In this paper, the unsteady aerodynamic characteristics of a three-car grouped high-speed train (HST) with different bogie fairing configurations under the crosswind are studied using improved delayed detached eddy simulation (IDDES) at Re = 1.85 × 106. The numerical method results are validated against the previous wind tunnel experiments. There are three cases with original half-fairing configuration (HFC), non-fairing configuration (NFC) and full-fairing configuration (FFC), respectively. The numerical results show that the bogie fairing configuration has significant effects. Compared to the HFC case, the drag force coefficients of the head, middle and tail cars with NFC increase by 53.13%, 14.87% and 27.04%, and corresponding parts of the FFC case decrease by 49.98%, 24.40% and 12.41%, respectively. The FFC case can also optimize the pressure distribution on the windward and leeward sides of the HST, and the flow structure and vertex distribution around the car body are also optimized. In addition, the increasing encirclement of the fairing configurations reduces the maximum lateral flow velocity inside the bogie cavities by 70% for HFC and 50% for FFC compared to the NFC. Overall, the FFC presents better aerodynamic performance than the NFC and HFC cases under crosswind, which is recommended for the design of the HST.

Effect of bogie fairing on aerodynamic and aeroacoustic behaviour of a high-speed train nose car

ABSTRACT The influence of bogie fairing on the flow feature and aerodynamic noise performance of a high-speed train nose car model is studied based on large-eddy simulation combined with acoustic analogy approach. For the case having no fairing, the strong flow interactions and impingements occur around the bogie cavity region due to the mass addition and expulsion induced from the cavity leading edges. When a streamlined fairing is mounted outside the bogie cavity, the fluid entrainment and vortices evolvement within the bogie cavity are weakened and the shear layer impingement and flow separation outside the fairing are mitigated greatly. Thus the wall pressure fluctuations on the solid surfaces of geometries located within bogie cavity are decreased and the flow-induced noise is reduced noticeably. Based on the semi-anechoic wind tunnel measurements on a high-speed train nose car model without and with bogie fairing, it is found that the dominant sound source around bogie cavity moves from its central area to rear wall region and the aerodynamic noise is reduced effectively with a streamlined fairing mounted around the bogie cavity. The numerical predictions of aerodynamic noise are verified by the experimental measurements. The investigation would be beneficial for guiding the low-noise design and configuration optimization of a high-speed train bogie fairing.

On the feasibility of a component-based approach to predict aerodynamic noise from high-speed train bogies

At speeds above 300 km/h, aerodynamic noise becomes a significant source of railway noise. In a high-speed train, the bogie area is one of the most important aerodynamic noise sources. To predict aerodynamic noise, semi-empirical component-based models are attractive as they allow fast and cheap calculations compared with numerical methods. Such component-based models have been previously applied successfully to predict the aerodynamic noise from train pantographs which consist of various cylinders. In this work, the feasibility is evaluated of applying them to the aerodynamic noise from bogies, which consist of various bluff bodies. To this end, noise measurements were carried out in an anechoic wind tunnel for different flow speeds using simple shapes representing various idealised components of a bogie. These results have been used to adjust the empirical constants of the component-based prediction model to enable its application to the bogie case. In addition, the noise from a 1:10 scale simplified bogie mock-up was measured and used for comparison with the prediction model. The results show good agreement between measurements and predictions for the bogie alone. When the bogie is located between two ramps approximating a simplified bogie cavity the noise is underpredicted at low frequencies. This is attributed to the noise from the cavity which is not included in the model.

Analysis of unsteady flow field and near-field aerodynamic noise of scale high-speed trains in long tunnel

The hybrid LES/APE method is used to simulate the unsteady flow field and the near-field aerodynamic noise of a 1/25 scale eight-coach high-speed train in long tunnel, validated by time-averaged pressure coefficients and Power Spectral Density of surface pressure from the aerodynamic wind tunnel test of a same scale two-coach train model. Train induced wind with the maximum velocity of 28 m/s in the opposite direction of train operating is formed in tunnel. Blocking effect leads to larger turbulent pressure and streamwise increment of turbulent power level from 133.7 dB to 138.2 dB, which is from130.3 dB to 133.4 dB in open air. With APE solver, three cases including tunnel with fully reflective walls, tunnel with fully absorptive walls and open air, are conducted to compare the influence of blocking effect and acoustic reflection on sound pressure. Total sound pressure level on the train body in tunnel is overall stronger than that in open air. The difference of sound power level between tunnel and open air is mostly contributed by acoustic reflection: 84.7 % at Coach 1, 84.3 % at Coach 8 and 66.0 ∼ 77.5 % from Coach 2 to Coach 7. Five peak frequencies: 520 Hz, 800 Hz, 1440 Hz, 2600 Hz and 3880 Hz are found from the frequency spectra of sound pressure of the probes in bogie cavities and pantograph grooves, in tunnel with fully reflective walls. Sound pressure modes help to clarify the generation mechanisms of peak frequencies: 520 Hz and 800 Hz are caused by the tunnel cavity resonance; 1440 Hz is caused by the first-order vertical mode from the bottom of the pantograph groove to the top of tunnel walls; 2600 Hz is caused by the first-order vertical mode from the ground to the top of bogie cavity, but 3880 Hz is not generated by simple in-phase cavity resonance.

Noise contribution and coherence analysis of high-speed train head shape under moving slab track

Aerodynamic noise generated by 1:8 scale three carriages high-speed train was investigated by numerical simulation and wind tunnel test. The difference of far-field noise below 1600 Hz between simulation based on dense mesh and test is less than 3 dB(A), which indicates that the current simulation method has reasonable accuracy. It is found that dipole source can be used as the only sound source to calculate the far-field noise because its intensity is more significant than that of the quadrupole source. The subdomain method is applied to investigate the noise contribution and coherence analysis of full-scale head shape. It is found that the far-field noise contributions of the frame, bogie cavity and wheel set are significant, and the peak frequency occurs at the frequency of 630 Hz. Coherence analysis indicates that the far-field noise with the train body as the sound source has a relatively high correlation with the pressure pulsation caused by the vortex structure generated at the wiper housing and the bogie. Also, the side vortex near the front wheel has a higher correlation with the far-field noise at a higher frequency, while a stronger correlation between that near the rear wheel and the far-field noise occurs at a lower frequency.

Numerical investigation on aerodynamic forces and flow patterns of high-speed trains from open air into long tunnel

Method of sliding mesh and segregated compressible large eddy simulation was used to simulate the flow field of a 1/25 scale eight-coach China Railway train running from open air into long tunnel, validated by the same scale Intercity Express 2 (ICE2) train. Side force fluctuation increases greatly when train enters tunnel. Short-time Fourier transform on side force coefficients of Coach 5 and 8 presents the peak frequency at about 95Hz. The hunting motion of laterally swinging airflow in lower space near the train is analyzed. Correlation analyses of pressure time histories reflect its traveling mode. Propagating velocity is 57–62% in open air, and 75–80% in tunnel of the operating speed. Wavelength is both in the range of 0.3–0.6m. Spectral Proper Orthogonal Decomposition (SPOD) and POD extract the transverse pattern of hunting motion. Total POD energy increases when hunting motion appears. Consistent to side force spectrums, SPOD energy spectrums present peak frequencies at 95Hz, where energy is larger in tunnel than open air. Mode 1 of POD and SPOD under peak frequencies presents similar spatial distribution: anti-symmetrical streamwise velocity fluctuation, vortex pairs outside bogie cavities and large-scale circulation. The relation between coherent structures and side forces is well established by SPOD.

Investigation on aerodynamic noise generated from the simplified high-speed train leading cars

The aerodynamic noise behavior of flow passing the simplified leading car and nose car scale models of a high-speed train is investigated through the vortex sound theory and acoustic analogy approach. The unsteady flow developed around the geometries is solved numerically and the data are applied to study the near-field quadrupole sound source and calculate the far-field noise radiated. It is found that the turbulent flow developed around the leading car is characterized by multi-scale vortices separated from the geometries. The intensity of volume dipole source is much larger than that of volume quadrupole source and the volume dipole source becomes the predominate source of the near-field quadrupole noise. The flow is separated noticeably in the regions of the nose, bogies, bogie cavities, and train tail of the leading car where the pressure fluctuations are generated largely upon the solid surfaces and correspondingly a dipole noise of high level is produced. By comparison, the noise contribution from the leading bogie and bogie cavity is larger than that from the other components. Moreover, the numerical and experimental results of train nose car model demonstrate that the flow around the bogie region is the dominant aerodynamic sound source. Therefore, the flow-induced noise generated from the leading cars may be reduced efficiently within a certain frequency range and specific direction by mitigating the flow interactions around the areas of leading bogie and bogie cavity.

Influence of bogie fairing configurations on the snow accretion around bogie regions of a high-speed train under crosswind conditions

In this paper, the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) was coupled with the Discrete Phase Model (DPM) to study snow accretion on the bogies of a high-speed train under crosswind conditions. The influence of bogie fairing configurations on the snow particles’ movement, accumulation and flow characteristics around bogie regions are assessed. The results show that the larger bogie fairings have a positive effect on snow reduction around the main components of bogies under crosswind conditions. Compared to currently used bogie fairings, the total snow accretion of a head car increases by 41.5% by removing the fairings, while it decreases by 24.9% with the installation of full bogie fairings. The larger bogie fairings can lower the velocity of underbody flow and prevent high-speed airflows from entering the bogie regions from the windward side of bogie cavities. Moreover, the larger bogie fairings reduce the snow concentration around the heat-producing components of the bogies and attenuate the amount of snow particles near the rear plates of the cavities. Thus, the larger fairings can provide better anti-snow performance of train bogies under crosswind conditions.

Impact of the bogies and cavities on the aerodynamic behaviour of a high-speed train. An IDDES study

This study investigates the effects of bogie cavities and bogies on the aerodynamic behaviour of a high-speed train (HST) using improved delayed detached eddy simulation (IDDES) at Re ​= ​3.3 ​× ​105. The main aim of this work is to identify the individual influence of bogies and cavities on the surrounding flow, thereby revealing aspects to further improve the HST aerodynamic performance. The accuracy of the numerical method has been validated against the experimental data obtained from a previous reduced-scale moving-model test, a wind tunnel test and a full-scale field test. The underbody flow, wake flow, slipstream velocity, aerodynamic drag and the computational costs are compared for three cases. The results show that installing the bogies around the cavities in Case 1 and sealing the cavities in Case 3 can effectively reduce the turbulence kinetic energy (TKE) and slipstream velocity around the HST. The cavities in Case 2 produce the highest level of TKE and slipstream velocity distribution in both underbody flow region and the wake region, compared to other two cases. This presents the largest scales of the shear vortices in the cavities and longitudinal vortices in the wake. Compared to Case 2, the TSI values of the slipstream velocity at the trackside position decreases by about 18.9% in Case 1 and 56.9% in Case 3, respectively.The cavities account for approximately 65% of the aerodynamic drag of the HST. Installing bogies in Case 1 and sealing cavities in Case 3 gives a 24% and 56% drag reduction for the overall HST. It is recommended to invest 10% higher resources to achieve an accurate surrounding flow prediction of a HST in presence of bogies.

Optimization of the anti-snow performance of a high-speed train based on passive flow control

In this paper, the improvement of the anti-snow performance of a high-speed train (HST) is studied using the unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) coupled with the Discrete Phase Model (DPM). The influences of the proposed flow control scheme on the velocity distribution of the airflow and snow particles, snow concentration level and accumulated mass in the bogie cavities are analyzed. The results show that the front anti-snow structures can effectively deflect downward the airflow and snow particles at the entrance of the cavities and alleviate the strong impact on the bogie bottom, thereby decrease the local accumulated snow. The rotational rear plates with the deflecting angle of 45

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

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.

A numerical study on water spray from wheel of high-speed train

The influence of water spray from wheels on the ice accumulation in the bogie regions of high-speed train has been studied using the coupling numerical methods of improved delayed detached eddy simulation (IDDES) and Lagrangian Model. The rotation of the wheels was simulated using the moving overset grid technique. The flow field, spatial distribution and surface distribution of droplets on the bogies have been analysed to identify the effect of various speed on the movement of droplets. The results show that the inlet speed between 160 ​km/h and 250 ​km/h will lead to the most severe influence on water spray from wheel in the whole bogie regions. A large amount of water droplets gathering on the surface of the bogies and bogie cavities is likely to cause severe ice accretion. The influence of water spray for high-speed train decreases rapidly at the speed of 300 ​km/h and changes a little as the speed continues to increase. Among all the components of the bogie, the brake clamp is most affected by droplets. Furthermore, the droplets were found to have a severe effect on the draft sill and air spring.

Measurement of aerodynamic bogie noise and flow-speed in the bogie cavity of high-speed train

Measurement of aerodynamic bogie noise and flow-speed in the bogie cavity of high-speed train

A numerical investigation on the improvement of anti-snow performance of the bogies of a high-speed train

In this paper, numerical simulations combining unsteady Reynolds-averaged Navier-Stokes (URANS) simulation and the discrete phase model are used to study the application of countermeasure for snow accumulation in the regions of bogie cavities of a high-speed train. The influence of the cowcatcher heights and guide structure configurations on the flow features and snow accumulation was studied. The results of the study show that the cowcatcher with a downward elongation of 4% of the distance between the two axles decreases the snow accumulation in the first and the second bogie regions by about 56.6% and 13.6%, respectively. Furthermore, the guide structures have been found to significantly alter the velocity and pressure distribution in the second bogie region, resulting in a relatively large snow-accumulation reduction. The deflector is found to perform better in reducing snow accumulation when compared to the diversion slots. The cowcatcher, elongated in the downward direction, and the deflector proved to be a good countermeasure for snow accumulation around the bogies of high-speed trains operating in snowy weather conditions.