A comparative study of methods to simulate aerodynamic flow beneath a high-speed train
A comparative study of methods to simulate aerodynamic flow beneath a high-speed train
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DOI：
10.1177/0954409717734090
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发表时间：
2018-05
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影响因子：
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通讯作者：
D. Soper;Dominic Flynn;C. Baker;A. Jackson;H. Hemida
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文献类型：
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作者：
D. Soper;Dominic Flynn;C. Baker;A. Jackson;H. Hemida
世界各地的高速铁路专用线的引入带来了与高速列车运行相关的问题。空气动力效应与列车速度的平方成比例增加；因此，在较高速度时，空气动力效应将明显大于低速列车。在有碴轨道床上，道碴颗粒在高速列车通过时悬浮在空气中的现象，导致需要了解列车和轨道相互作用(包括空气动力学和岩土工程)所涉及的过程。在高速列车下进行全尺寸空气动力测量的困难产生了能够在模型尺度上准确模拟这些复杂的空气动力流动的要求。在这项研究中，分析了动模试验和数值模拟的结果，以确定每种方法模拟高速列车底部空气动力流动的性能。通过将结果与全面测量的结果进行比较，对这两种情况进行了验证。在1/25比例尺上进行了动模试验和数值模拟。移动模型试验和计算流体力学模拟得到的水平速度除了接近压舱物的速度外，其余大部分都是相似的。在该区域，多孔气动探头无法准确测量速度。数值模拟能够将流动分解到比实验所能测量到的更小的湍流尺度，并显示出峰值速度量级的超调。数值模拟中的压力和速度值比实验测试中的要大。这被认为是由于压载石的影响，在实验研究中允许流动扩散通过它们，而在计算流体力学模拟中，流动停滞在光滑的无孔表面上。对标准偏差和湍流强度的进一步验证发现，实验数据之间有很好的一致性，但数值模拟存在超调。运动模型和计算流体力学技术均能模拟高速列车下的流动发展过程。因此，可以使用这些技术作为一种方法来模拟地下流动，以期训练同源性。
The introduction of dedicated high-speed railway lines around the world has led to issues associated with running trains at very high speeds. Aerodynamic effects proportionally increase with train speed squared; consequently, at higher speeds aerodynamic effects will be significantly greater than those of trains travelling at lower speeds. On ballasted track beds, the phenomenon in which ballast particles become airborne during the passage of a high-speed train has led to the need for understanding the processes involved in train and track interaction (both aerodynamical and geotechnical). The difficulty in making full-scale aerodynamic measurements beneath a high-speed train has created the requirement to be able to accurately simulate these complex aerodynamic flows at the model scale. In this study, the results of moving-model tests and numerical simulations were analysed to determine the performance of each method for simulating the aerodynamic flow underneath a high-speed train. Validation was provided for both cases by juxtaposing the results against those from full-scale measurements. The moving-model tests and numerical simulations were performed at the 1/25th scale. Horizontal velocities from the moving-model tests and computational fluid dynamics simulations were mostly comparable except those obtained close to the ballast. In this region, multi-hole aerodynamic probes were unable to accurately measure velocities. The numerical simulations were able to resolve the flow to much smaller turbulent scales than could be measured in the experiments and showed an overshoot in peak velocity magnitudes. Pressure and velocity magnitudes were found to be greater in the numerical simulations than in the experimental tests. This is thought to be due to the influence of ballast stones in the experimental studies allowing the flow to diffuse through them, whereas in the computational fluid dynamics simulations, the flow stagnated on a smooth non-porous surface. Additional validation of standard deviations and turbulence intensities found good agreement between the experimental data but an overshoot in the numerical simulations. Both moving model and computational fluid dynamics techniques were shown to be able to replicate the flow development beneath a high-speed train. These techniques could therefore be used as a method to model underbody flow with a view to train homologation.