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With the increase in high-speed train (HST) operation speed, the light-weight design of the train body and component structure is pursued to reduce energy consumption during operation, but this seriously deteriorates the aerodynamic performance of the light-weight structure outside the train body under the effect of strong unsteady airflow, and the more obvious case is the frequently occurring problem of vibration, large deformation, and damage to the rubber exterior windshield at the connection position of HST carriages. We investigate the fluid–structure coupling mechanism of the interaction between the rubber external windshield and aerodynamic force, and compare the dynamic characteristics of windshield structure under different design parameters. A numerical simulation of three rubber outer windshield structure parameters (sidewall distance of U-shaped capsule, sidewall thickness, sidewall inclination angle) is carried out using FSI simulation of the two-way coupling method. The aerodynamic load, airflow dynamics around the windshield, and the nonlinear vibration and deformation form of the windshield is analyzed in detail. The results show that the aerodynamic response of the HST rubber external windshield analyzed by the FSI method is in good agreement with the full-scale test results. Additionally, the stiffness of the windshield can be improved by increasing the thickness of the windshield sidewall. When the distance between the sidewall of the windshield is increased, an insufficient thickness at the top of the arc causes a large local deformation at the top of the arc of the windshield. The method established and relevant research results can provide good support for the aerodynamic stability evaluation of HST windshields. [ABSTRACT FROM AUTHOR]

By using three different head types (5 m, 7.5 m and 10 m nose lengths), the CRH3 (China Railway High-speed 3) flow field structure at 15° yaw was studied through wind tunnel experiments and numerical simulations. The modifications of the aerodynamic coefficients were studied using the Improved Delayed Separation Eddy Simulation (IDDES) method. The results show that the longer the nose length of the tail car, the more it is affected by crosswind. However, the increase in turbulence mitigates the risk of overturning the tail car as the pressure distribution between the train side surface and the underbody becomes more disturbed. The nose length of the head car can affect the position and length of the longitudinal vortex core on the leeward side, thus affecting the lift and side force of each section of the train. The location of the time-averaged vortex core for a 15° crosswind is approximately 0.67H~0.7H high from the ground and 0.65H~0.67H wide from the center of the train. The main frequency of the leeward vortex ranges from 0.1 to 0.3. The transient vibration amplitude at the position of the vortex core is the largest, and the main frequency of vibration is 0.18. The tail car nose length should be properly lengthened since increasing the length of the tail car reduces the negative pressure on the surface of the tail car, thus reducing drag and side force. However, the excessive length of the tail car nose increases the risk of overturning under crosswind. [ABSTRACT FROM AUTHOR]

The external windshield is a key component in high-speed trains for drag reduction. However, the installation gap between external windshields, which is intended for improving curve-passing ability, could lead to strong aerodynamic instability in train-end area and therefore significant operating risk for train. This study aims to advance this field based on detailed numerical simulation, investigating the related flow features in this area, particularly from a time-dependent perspective. Flow field around external windshields with different installation gaps (10, 20 and 30 mm) is resolved based on Improved Delayed Detached Eddy Simulation (IDDES). The aerodynamic forces on different windshield components, turbulent flow fields around the train-end area, and corresponding low-dimensional modes are analyzed. The results show that the difference in the external windshield gap can significantly affect the related aerodynamic forces, with the 20 mm case having the highest time-averaged values. The aerodynamic spectrum shows primary, secondary and tertiary peak frequencies with a relatively high power spectral density (PSD). Decreasing the gap distance generally increases the overall PSD in the Strouhal number ranges considered, particularly for the secondary and tertiary peaks. The load forms and their energy distributions under different external windshield gaps are obtained through the proper orthogonal decomposition analysis. [ABSTRACT FROM AUTHOR]

The pressure variations induced by a CRH380A EMU on a 2.15 m high bridge noise barrier are investigated in a field measurement. The familiar fluctuating pressure time history curves and the peak-to-peak pressure ( ΔP ) distributions attributing to the train head on the barrier surfaces are presented. A comparison of the positive head pulse pressure is made between the measurement results and the data calculated by empirical equations in EN 14067-4. Furthermore, the influences of train speed, train running lines, locations of measurement points, train marshalling length and environmental wind speed on ΔP are analysed. The results indicate as the train speed increases, the corresponding time intervals of ΔP decrease gradually, whereas their slopes become increasingly steep. For a CRH380A EMU, the aerodynamic length of the train head is between 7.63 and 7.64 m, which differs from the physical length of a realistic train with 12.00 m. Along the noise barrier from bottom to top, the ΔP values on the inner surface decrease with the increase of height, while these values on the outer surface increase. Taking the wind direction into account, the ΔP values are a little higher when the high-speed trains run against the wind direction. [ABSTRACT FROM AUTHOR]

Transient aerodynamic pressures induced by the passage of high-speed trains past noise barriers can result in noise barrier damage. This issue is investigated experimentally in the present study by applying pressure sensors to measure the transient aerodynamic pressures acting on the inner surface (close to the railway track) of a 2.15-m high straight-type noise barrier arising from the passage of two different full-scale high-speed trains with different streamlined head cars operating at a speed of 380–420 ​km/h. The results demonstrate that the amplitudes of transient aerodynamic pressures acting on the inner surface of the noise barrier are greatest at the bottom of the noise barrier, and the pressure decreases with increasing height along the barrier. In addition, the dynamic characteristics of the aerodynamic loads are investigated using the fast Fourier transform algorithm. The main frequencies of the transient aerodynamic pressures observed over the train speed range considered are found to be proportional to the train speed and inversely proportional to the single-car length. Moreover, the results of analysis indicate that noise barrier damage can be minimized over the train speed range considered by building noise barriers with natural frequencies residing outside of the 4.21–4.74 ​Hz range. • Full-scale experiment about transient pressure on noise barrier induced by high-speed trains running at 380–420 km/h. • The amplitudes characteristics of transient aerodynamic pressures acting on the surface of the noise barrier. • The main frequencies of the transient aerodynamic pressures at different train speed. [ABSTRACT FROM AUTHOR]

The current research attempts to describe the association between the aerodynamic drag and flow structures induced by train running in time-averaged and time-dependant views. A ICE2 train model is used as the research object, with the flow field solved by Large Eddy Simulation (LES). The validation is carried out through comparison with existing research data, and grid independence study in terms of time-averaged and second-order statistics. Numerical results are firstly presented by description of the time-averaged near wake flow topology based on surface flow visualization. Then, the wake integration method is used both time-averaged and instantaneously to link the aerodynamic force with integrated flow quantities on different wake planes: from the time-averaged perspective, the contribution of different flow terms to total drag is presented and compared; from the instantaneous perspective, the overall wake variation tendency is linked to the fluctuating component of aerodynamic force, based on the wake convection velocity and downstream distance of wake planes. The dynamic features of flow quantities in different locations are presented, with cross-correlation method used to describe the correlation between fluctuating aerodynamic drag and wake motion. Approaches and findings presented in the current study could serve as fundamentals which support future study. • Large eddy simulation employed to solve flow field around a generic ICE2 high-speed train model. • Surface flow visualization techniques utilized to illustrate the time-averaged near wake flow topology. • Wake integration method applied to link the aerodynamic force with integrated flow quantities on different wake planes. • Dynamic features of flow quantities presented, with cross-correlation method used to describe correlation between aerodynamic drag and wake motion. [ABSTRACT FROM AUTHOR]