Experimental and simulation research on the aerodynamic effect on a train with a wind barrier in different lengths

https://doi.org/10.1016/j.jweia.2021.104644Get rights and content

Highlights

  • Wind tunnel tests on trains with a wind barrier in different length were conducted.

  • Various aerodynamic characteristics were explained by the pressure distribution on the train.

  • Wind barrier length was proved to have an obvious influence on the head car other than the tail car.

  • The suggested length of wind barrier and its effect on the aerodynamics of high-speed train were discussed.

Abstract

Wind tunnel tests and the improved delayed detached eddy simulation (IDDES) were carried out to study the aerodynamic characteristics of a train with a wind barrier in different lengths. The results were obtained at 20° and 30° yaw angles, which are the highest realistic values for high-speed trains. The rationality of the experiment was assessed according to standards, based on which the accuracy of numerical simulations was validated. After the validation, further cases that were difficult to conduct in wind tunnel experiments were simulated to explore how the barrier length affects the train aerodynamics. Results show that the length of the wind barrier has an obvious influence on the head car other than the tail car. As the length of the wind barrier increases, the lift force of the head car decreases, while the lateral force increases, and the drag force approaches to 0. The lateral and drag forces of the head car do not change significantly when the wind barrier length was longer than 66.49H at a 20° yaw angle and 40.54H at a 30° yaw angle.

Introduction

The aerodynamic performances of high-speed trains under crosswinds have been an important research topic in recent years (Baker, 2013; Guo et al., 2019, 2020). It is mentioned in some European standards that external wind protection measures have a positive effect on the safety of trains operating in crosswinds. The implementation of these measures has greatly improved the safety of train operation, while wind barriers, as low-cost facilities with good wind-proofing effects, have been widely used in wind-proofing projects around the world (Buljac et al., 2017; He et al., 2014; Tomasini et al., 2016). To study the shielding efficiency of the wind barriers of trains, researchers have used methods such as numerical simulations (Hemida and Baker, 2010; Hemida and Krajnović, 2010; Liu et al., 2020; Niu et al., 2018), wind tunnel tests (Avila-Sanchez et al., 2016; Charuvisit et al., 2004; Hashmi et al., 2019), and full-scale vehicle tests (Baker et al., 2004; Bell et al., 2020; Soper et al., 2017), and many valuable research results have been obtained. Among these approaches, wind tunnel tests are widely used due to their lower costs, high measurement accuracies, and controllable flow parameters, and they are not affected by weather conditions.

In the research of the aerodynamic performances of high-speed trains under crosswinds in wind tunnel tests, moving and stationary train models have been mainly used. For moving train models (Bocciolone et al., 2008; Dorigatti et al., 2015; Li et al., 2018; Wang et al., 2018, 2018; Xiang et al., 2018), the biggest advantage is that they can provide a more realistic simulation of train operation. The relative movement between the train and the surrounding facilities can be well reproduced by this method when the train is operating, and the results are more realistic. However, this type of testing method is expensive and difficult to execute, and the data collection process is short during the test. In addition, the speed of the moving model is not easy to control, which can cause damage to the measurement devices, and the collected results have more interference components due to the unstable factors. For stationary train models (Hashmi et al., 2019; Tomasini et al., 2016), the yaw angle can be set by rotating the train and the infrastructure models around the vertical axis. Tests with stationary trains are simple and easy to control, and the test results are relatively stable. However, the wind motion in these tests is different from that in a real train system, where the relative wind speed acting on the vehicle is the sum of the vectors of the train velocity and the crosswind velocity, while the infrastructure, being motionless, is subjected to the absolute wind speed (Premoli et al., 2016). Moreover, the relative motion between the train and the surrounding structures, such as a wind barrier wall or embankment, is not correctly reproduced.

Due to their convenience and lower costs, static tests have been widely employed. Dorigatti et al. (2015) studied the differences between moving and static experiments, and found that, in terms of the overall mean aerodynamic side and lift forces and rolling moment coefficients, static experiments were sufficiently accurate. Tomasini et al. (2016) carried out a number of static tests in the Politecnico di Milano wind tunnel to study the properties of different wind barriers for high-speed railway lines. Xue et al. (2020) conducted static wind tunnel tests and evaluated the effects of barrier parameters on the aerodynamic characteristics of the wind–vehicle–bridge system. In the above-mentioned studies and others (Buljac et al., 2017; Chen et al., 2015; He et al., 2014), the motion of the train relative to the walls was not taken into account, but the results presented were considered remarkable.

When conducting wind tunnel tests, a reasonable selection of the model parameters is crucial. Cheli et al. (2010a) measured the aerodynamic coefficients of the ETR500 train model based on wind tunnel tests, and the results indicated that the infrastructure scenarios had significant influences on the relationship between the aerodynamic coefficients and yaw angles. Tomasini et al. (2014) concluded that the distance from the upstream end of the ground model to the train model is a key parameter for determining the aerodynamic coefficients. Sicot et al. (2018) researched the influence of the reproduction scale of the geometric details on models during wind tunnel tests and determined that the presence of geometric structures deeply affected the forces and moments measured under crosswinds.

In engineering applications, a wind barrier is a long wall that can be regarded as having an infinite length at a certain time when a train passes. The wind barrier model should be as long as possible to reduce its end effects on the train model. The flow deviations generated by a wall-to-wall layout barrier are significantly reduced (Tomasini et al., 2014). However, it is usually difficult to use a very long wind barrier for testing due to the limitations of the wind tunnel size and the test cost. The EN standard (CEN European Standard, 2013) has a simple definition of the length of the noise barrier with a lower thickness, but it may be unsuitable for heavy-duty wind barrier walls made of concrete with a certain thickness. There is currently no consensus on the length of the wind barrier to guide static wind tunnel tests with wind barriers. In some previous studies, the length of the barrier was equal to the length of the subgrade model (Hashmi et al., 2019; Tomasini et al., 2016). However, Schober et al. (2010) and Diedrichs et al. (2007) investigated finite-length embankment models, which did not reach the side walls of the wind tunnel, and found unrealistic flows on the leeward sides of the embankment models subjected to crosswinds.

Therefore, determining how to select the length of the wind barrier based on the corresponding test conditions and minimizing the test error in static wind tunnel tests requires attention. In this paper, a wind tunnel test and numerical simulation were conducted to study the differences in the aerodynamic performances of trains with different wind barrier lengths, which provides guidance for selecting the length of wind barriers in the static wind tests of trains. The paper is organized as follows. The set-up of the wind tunnel test is described in Section 2. The test results and simulation are presented in Section 3, and Section 4 presents the conclusions.

Section snippets

Wind tunnel and test device

Wind tunnel tests were carried out at the National Engineering Laboratory of High-Speed Railway Construction Technology of Central South University in China. This wind tunnel (Fig. 1) is a circulating wind tunnel, and the dimensions of the high-speed test section are 15 ​m (length) ​× ​3 ​m (width) ​× ​3 ​m (height). The wind speed range is 5–94 ​m/s, and the turbulence is less than 0.5%.

The flow velocity in test section was measured by a four-hole dynamic pressure “cobra” probe. The train body

Results and discussion

The non-dimensional aerodynamic forces were calculated according to the CEN European Standard (2009) as follows:CP=(PP0)/0.5ρUref2,CS=Fx/0.5ρUref2S,CL=Fz/0.5ρUref2S,CD=Fy/0.5ρUref2S,where CP is the pressure coefficient, CS, CL, and CD denote the coefficients of the side, lift, and drag forces, respectively, the reference area S for the 1:31 scaled model was 0.01165 ​m2, the incoming flow density ρ was 1.225 ​kg/m3, (P ​− ​P0) is the differential pressure measured using the pressure scanning

Conclusions

In the present paper, wind tunnel tests and numerical simulations were carried out to study the aerodynamic performance of a train with wind barriers in different lengths. Results for two yaw angles, 20° and 30°, were also analyzed. The conclusions of the study are as follows.

  • 1.

    The presence of the wind barrier effectively weakened the negative pressure on the top regions of the head car, while it strengthened the negative pressure on the tail car. The length of the wind barrier has an obvious

CRediT authorship contribution statement

Houyu Gu: Idea, Writing – original draft. Tanghong Liu: Supervision, Validation. Zhiwei Jiang: Visualization, Investigation. Zijian Guo: Idea, Writing – original draft.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by Postgraduate Scientific Research Innovation Project of Hunan Province [Grant number CX20200105] and Fundamental Research Funds for the Central Universities of Central South University [Grant number 2020zzts108].

References (45)

  • F. Cheli et al.

    Experimental study on the aerodynamic forces on railway vehicles in presence of turbulence

    J. Wind Eng. Ind. Aerod.

    (2013)
  • F. Cheli et al.

    Aerodynamic behaviour investigation of the new EMUV250 train to cross wind

    J. Wind Eng. Ind. Aerod.

    (2010)
  • N. Chen et al.

    Effects of wind barrier on the safety of vehicles driven on bridges

    J. Wind Eng. Ind. Aerod.

    (2015)
  • T. Dong et al.

    Effects of simplifying train bogies on surrounding flow and aerodynamic forces

    J. Wind Eng. Ind. Aerod.

    (2019)
  • F. Dorigatti et al.

    Crosswind effects on the stability of a model passenger train—a comparison of static and moving experiments

    J. Wind Eng. Ind. Aerod.

    (2015)
  • Z. Guo et al.

    Aerodynamic influences of bogie’s geometric complexity on high-speed trains under crosswind

    J. Wind Eng. Ind. Aerod.

    (2020)
  • Z. Guo et al.

    Numerical study for the aerodynamic performance of double unit train under crosswind

    J. Wind Eng. Ind. Aerod.

    (2019)
  • S.A. Hashmi et al.

    Wind tunnel testing on a train model subjected to crosswinds with different windbreak walls

    J. Wind Eng. Ind. Aerod.

    (2019)
  • X.H. He et al.

    Aerodynamic characteristics of a trailing rail vehicles on viaduct based on still wind tunnel experiments

    J. Wind Eng. Ind. Aerod.

    (2014)
  • H. Hemida et al.

    Large-eddy simulation of the flow around a freight wagon subjected to a crosswind

    Comput. Fluids

    (2010)
  • H. Hemida et al.

    LES study of the influence of the nose shape and yaw angles on flow structures around trains

    J. Wind Eng. Ind. Aerod.

    (2010)
  • W. Khier et al.

    Flow structure around trains under side wind conditions: a numerical study

    Comput. Fluids

    (2000)
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