| 1. |
- Dong, Tianyun, et al.
(författare)
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Effects of simplifying train bogies on surrounding flow and aerodynamic forces
- 2019
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 191, s. 170-182
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Elsevier Ltd In this study, the numerical solution of a high-speed train with several simplified bogies is investigated. The time-averaged flow field around the train, the surface pressure, and the aerodynamic forces on the train are discussed. The results reveal that a simpler bogie structure can achieve a higher underbody flow velocity and change fluctuations beneath the train owing to the resulting turbulence level. The simplification of bogies has a smaller effect on the side slipstream velocity and pressure compare to which in underbody, and at 3 m away from the centre of the track, the simplified bogie with wheels and a simple side frame used in this study obtains similar results to cases wherein more complex bogies are used. The surface pressure under the train is affected by bogie simplification, especially in the bogie cabin end area, resulting in aerodynamic drag and lift variations. If underbody flow or aerodynamic drag and lift forces are the focus of study, then the geometry of the centre region of the bogie, i.e. its main structures features, should be maintained in simplified models.
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| 2. |
- Liang, Xifeng, et al.
(författare)
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On the aerodynamic loads when a high speed train passes under an overhead bridge
- 2020
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 202
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Tidskriftsartikel (refereegranskat)abstract
- The aerodynamic loads on the overhead bridge bottom surface induced by train passage are reported in this paper. Both moving model test and numerical simulation approaches at the 1:20 scale are used. The numerical work is validated through both mesh independence tests and comparison with experimental data. Typical pressure variation curves are plotted and compared with previous studies. The peak pressure values’ dependence on the Reynolds number is considered through four sets of experiments with different train running speeds. The peak pressure coefficient distribution law for the bridge bottom surface is presented. Differences in the pressure distribution in different bridge bottom areas are explained based on more detailed flow field information. The influence of the bridge height on the aerodynamic load magnitude and time interval is presented. Moreover, the application of the CEN Standard to practical engineering issues is discussed.
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| 3. |
- Wang, Pan, et al.
(författare)
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Genome-wide study identifies the regulatory glycosyltransferase genes networks and signaling pathways from Keshan disease
- 2014
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Ingår i: Journal of Health Science. - : David Publishing Company. ; 2:4, s. 165-173
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Tidskriftsartikel (refereegranskat)abstract
- KD (Keshan disease) is an endemic cardiomyopathy occurring only in China. Its pathogenesis is unclear till now. In the study, gene expression profiles of the PBMC (peripheral blood mononuclear cell) derived respectively from KD patients and healthy in KD areas were compared. Total RNA was isolated, amplified, labeled and hybridized to Agilent 4 × 44 K Whole Human Genome Oligonucleotide Microarray. Significant canonical pathways were analyzed by IPA (ingenuity pathway analysis) to identify differently expressed genes and pathways involved in the cardiovascular system development and function. Quantitative RT-PCR was applied tofurther validate our microarray results. Eighty-three up-regulated (ratios ≥ 2.0) and nine down-regulated glycosyltransferase genes (ratios ≤ 0.5) in PBMC in KD patients were detected by significance analysis of microarrays. Two significant canonical pathways from glycosyltransferase gene expression profiles were screened by IPA. The results of qRT-PCR show that four up-regulated (BMP1/7/10 and FGF18) and one down-regulated (BMP2) genes are consistent with those in microarray experiment, confirming the validity of the microarray data. Based on the results of the study, it is suggested that bone morphogenetic proteins and fibroblast growth factors might play an important role in the pathogenesis of KD. This further helps us to understand the pathogenesis of KD, as well as dilated cardiomyopathy
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| 4. |
- Zhang, Jie, et al.
(författare)
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A novel vented tunnel hood with decreasing open ratio to mitigate micro-pressure wave emitted at high-speed maglev tunnel exit
- 2023
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - 0167-6105. ; 240
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Tidskriftsartikel (refereegranskat)abstract
- The significant increase in train speed contributes to stronger vehicle/tunnel coupling aerodynamic effect, especially on the intensity of the micro-pressure wave (MPW) emitted at high-speed maglev tunnel exit. Hence when the train speed reaches 600 km/h and more, how to effectively mitigate the MPW becomes a challenge for aerodynamic researchers. In this study, a novel vented tunnel hood with the decreasing open ratio along the enlarged cross-section wall was proposed, while one consistent and two inconsistent layouts of the hoods applied at the tunnel portals were attempted to obtain a better hood combination for the mitigation of MPW. In addition, the sliding mesh technique was used to simulate the train passing through the single-track high-speed maglev tunnel. The validation of the methodology has been carried out to compare with the previous moving model test results. The peak variations of pressure wave and MPW were analysed in combination with the grid-independence study and numerical validation. The new hoods installed consistently at the tunnel portals (entrance and exit), can reduce the maximums of MPWs at required locations, i.e., 20m and 50m from the tunnel exit, by 66.9% and 40.9% respectively, when compared to the existing unvented tunnel hood; however, when the new hood at the tunnel exit is replaced by the existing tunnel hood without vents, the maximums of MPWs at the corresponding 20m and 50m are significantly increased by 79.1% and 71.0%. After changing the set-up of the inconsistent hoods, i.e., the tunnel entrance hood is unvented and this novel hood is installed at the tunnel exit, the corresponding MPW peaks can be reduced by 84.0% and 71.1%. Therefore, the hoods at both of tunnel entrance and exit can affect the variations of MPWs, and a reasonable arrangement of the hood openings at tunnel portals can effectively mitigate the MPW emitted at the high-speed maglev tunnel exit.
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| 5. |
- Zhang, Jie, 1987, et al.
(författare)
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A study of the influence of bogie cut outs' angles on the aerodynamic performance of a high-speed train
- 2018
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 175, s. 153-168
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Tidskriftsartikel (refereegranskat)abstract
- The aerodynamic drag of a high-speed train can contribute significantly to its energy consumption. Hence, the purpose of this paper is to find out a new compound mode of bogie cut outs to achieve drag reduction for a Chinese high-speed train. In this paper, a Detached Eddy Simulation method based on the Realizable k-ε turbulence model was used to investigate the underbody flow features of high-speed trains with different compound modes in the angles of bogie cut outs at Re = 1.85 × 10 6 . The time-averaged aerodynamic drag was compared with experimental data from wind tunnel tests. The results show that the DES simulations present high accuracy in predicting this kind of flow underneath the train body, and those numerical results closely agree with the experimental data. The variations of bogie cut outs' angles only cause the changes of flow structures around the bogies and in the wake. As a result, obtain different aerodynamic drag forces. Most of drag of the train is experienced by the streamlined head and all bogie regions. A new compound mode of bogie cut outs is proposed in the present paper, achieving 2.92% drag reduction for a three-car model.
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| 6. |
- Zhang, Jie, 1987, et al.
(författare)
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Detached eddy simulation of flow characteristics around railway embankments and the layout of anemometers
- 2019
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- Anemometers are usually set up along railway embankments to monitor wind speeds, and the layout for them has to be investigated. This work used an improved delayed detached eddy simulation (IDDES) approach to explore the flow properties around railway embankments, and then a proposal was put forward for the layout of anemometers. The numerical method was validated against previous wind tunnel tests on the speed-up ratios of the flow around a 1/300 scale two-dimensional embankment with the slope gradient of 1:2. The effects of inlet velocity profiles, i.e., uniform velocity and atmospheric boundary layer velocity profiles, on the speed-up ratios around a 5 m high railway embankment were compared. The study indicates that using a uniform velocity profile to assess the operational safety of trains running across strong wind regions could be favourable, especially when complex local terrains contribute to different wind characteristics. The anemometers should be set upstream, i.e., at a well defined distance in locations with sufficient extent of open ground and on the electrification masts along railway lines. This is not in line with the anemometer layout of the existing SWEWS (Strong Wind Early Warning Systems), the difference being due to the speed-up effect of the railway embankment, which is usually not considered explicitly. Formulas have been developed on the basis of regression of the simulation results to express the relationships between e.g. top wind speed over the embankment (located in an area where it is not possible to install anemometers) and measured wind speeds. In this way it is possible to take into account the speed-up effect encountered by the wind passing over the embankment, which needs to be considered in the operational rules in order to ensure safe operations.
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