Double-unit trains increase passenger capacity but also increase energy consumption. Therefore, research about the aerodynamic resistance of a double-unit train is of great importance to save energ...

https://www.tandfonline.com/doi/pdf/10.1080/19942060.2021.1895321

Numerical investigation on the aerodynamic resistances of double-unit trains with different gap lengths

Aerodynamic response of high-speed trains under crosswind in a bridge-tunnel section with or without a wind barrier

Study on the aerodynamic noise characteristics of high-speed pantographs with different strip spacings

In order to study the aerodynamic characteristics of high-speed trains in the evacuated tube in the low-pressure environment, the fluid model, mathematical model and numerical model of aerodynamic computation of high-speed trains in the evacuated tube in the low-pressure environment are established. The effect of internal tube pressure(1.01×103-1.01×104 Pa), blockage ratio(0.2-0.7) and train speed(600-1 000 km/h) on the drag coefficient, aerodynamic drag force and aerothermal effect are studied. The computational results show that in the lower-pressure(1.01×103-1.01×104 Pa) environment, the air flow in the evacuated tube can be described by continuum model. The flow field of high-speed trains in the evacuated tube can be described by 3D compressible Navier-Stokes equation. The friction drag coefficient of high-speed trains is far smaller than the pressure drag coefficient. The pressure drag coefficient and aerodynamic drag coefficient is basically nothing to do with the internal tube pressure and train speed, but mainly depends on the blockage ratio. The aerodynamic drag force of high-speed trains is almost linear with the tube pressure, and almost square with the train speed, and also increases with the increase of blockage ratio. The maximum temperature on the surface of high-speed trains is essentially independent of the internal tube pressure, and mainly depends on the train speed and blockage ratio.

Analysis of Aerodynamic Characteristics of High-speed Trains in the Evacuated Tube

For high-speed trains the aerodynamic noise sources become important for speeds above about 300 km/h. The pantograph is mounted on the train roof, often in a shallow cavity. Because of its elevated position it is an important source of noise from high-speed trains, especially in the presence of noise barriers which shield sources that are lower on the train. In this paper, the flow features and noise sources of a high-speed train pantograph and its recess are numerically investigated at a speed of 300 km/h (Mach number 0.24). The geometry of the pantograph recess is simplified as a 'closed' rectangular cavity and two pantographs (one opened and one retracted) are included that are based on a DSA 350 pantograph. To resolve the details of the turbulent flow structures and hence enable accurate noise predictions, the Improved Delayed Detached-Eddy (IDDES) model is used to model the flow field. The Ffowcs-Williams & Hawkings aeroacoustics model is employed for far-field acoustic calculations. In comparison with the same cavity without pantographs, the flow around the cavity shows slightly different characteristics when the pantographs are placed in the cavity. The wake region in the downstream region of the cavity is slightly reduced due to interaction between cavity flow and pantographs. This can affect the noise emission from this region. This study indicates that the main noise sources are from the raised pantograph, and the panhead of the retracted pantograph as shear layers impinge on them. The cavity trailing edge also generates significant levels of noise. The far-field noise is found to be broadband. The directivity of the noise radiated from pantographs and cavity is also obtained.

Effect of cavity flow on high speed train pantograph aerodynamic noise

The numerical simulation based on Reynolds time-averaged equation is one of the approved methods to evaluate the aerodynamic performance of trains in crosswind. However, there are several turbulence models, trains may present different aerodynamic performances in crosswind using different turbulence models. In order to select the most suitable turbulence model, the inter-city express 2 (ICE2) model is chosen as a research object, 6 different turbulence models are used to simulate the flow characteristics, surface pressure and aerodynamic forces of the train in crosswind, respectively. 6 turbulence models are the standard k-e, Renormalization Group (RNG) k-e, Realizable k-e, Shear Stress Transport (SST) k-ω, standard k-ω and Spalart–Allmaras (SPA), respectively. The numerical results and the wind tunnel experimental data are compared. The results show that the most accurate model for predicting the surface pressure of the train is SST k-ω, followed by Realizable k-e. Compared with the experimental result, the error of the side force coefficient obtained by SST k-ω and Realizable k-e turbulence model is less than 1 %. The most accurate prediction for the lift force coefficient is achieved by SST k-ω, followed by RNG k-e. By comparing 6 different turbulence models, the SST k-ω model is most suitable for the numerical simulation of the aerodynamic behavior of trains in crosswind.

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Effect of RANS Turbulence Model on Aerodynamic Behavior of Trains in Crosswind

Abstract In this paper, the unsteady flow around a high-speed train is numerically simulated by detached eddy simulation method (DES), and the far-field noise is predicted using the Ffowcs Williams-Hawkings (FW-H) acoustic model. The reliability of the numerical calculation is verified by wind tunnel experiments. The superposition relationship between the far-field radiated noise of the local aerodynamic noise sources of the high-speed train and the whole noise source is analyzed. Since the aerodynamic noise of high-speed trains is derived from its different components, a stepwise calculation method is proposed to predict the aerodynamic noise of high-speed trains. The results show that the local noise sources of high-speed trains and the whole noise source conform to the principle of sound source energy superposition. Using the head, middle and tail cars of the high-speed train as noise sources, different numerical models are established to obtain the far-field radiated noise of each aerodynamic noise source. The far-field total noise of high-speed trains is predicted using sound source superposition. A step-by-step calculation of each local aerodynamic noise source is used to obtain the superimposed value of the far-field noise. This is consistent with the far-field noise of the whole train model’s aerodynamic noise. The averaged sound pressure level of the far-field longitudinal noise measurement points differs by 1.92 dBA. The step-by-step numerical prediction method of aerodynamic noise of high-speed trains can provide a reference for the numerical prediction of aerodynamic noise generated by long marshalling high-speed trains. 

/pdf/step-by-step-numerical-prediction-of-aerodynamic-noise-we5xt0vo.pdf

Step-by-Step Numerical Prediction of Aerodynamic Noise Generated by High Speed Trains

In recent years, the evacuated tube maglev train (ETMT) has gradually become the research hotspot due to the increasing demand of the travelling speed. The suspension gap related to running safety ...

Deng Qin

Papers

Effect of RANS Turbulence Model on Aerodynamic Behavior of Trains in Crosswind

Study on the aerodynamic noise characteristics of high-speed pantographs with different strip spacings

Step-by-Step Numerical Prediction of Aerodynamic Noise Generated by High Speed Trains

Aerodynamic characteristics of the evacuated tube maglev train considering the suspension gap

Numerical study on the aerodynamic and acoustic scale effects for high-speed train body and pantograph