Abstract
With the continuously increased speed of the high-speed train, the lateral aerodynamic performance of high-speed trains has attracted more and more attention. Under strong crosswinds, the aerodynamic performance of trains deteriorate and air drag, lift and lateral forces borne by trains quickly increase, which has an impact on the lateral stability of trains and even leads to train derailment. This paper adopted computational fluid dynamics theory to establish an aerodynamic model for a high-speed train, computed aerodynamic forces and moments acting on the high-speed train and obtained the unsteady flow field of the high-speed train. In the meanwhile, this paper combined with multi-body system dynamics theory to establish a system dynamics model for the train and analyzed the safe aerodynamic performance of the high-speed train under cross winds. Computational results showed: Under cross winds, the aerodynamic performance of the high-speed train had a random fluctuation. When wind direction angle was 90°, aerodynamic forces (drag, lift and lateral forces) and moments (overturning moment, shaking moment and nodding moment) borne by the high-speed train were the largest; train speed was a main factor affecting the size of positive pressures of train and cross wind velocity had no obvious impacts on the positive and negative pressures of train body; the aerodynamic forces and moments of the high-speed train had a random fluctuation within a certain range with time; the frequency for the peak value of power spectral density of lateral forces of head train was within 25 Hz and the peak value of power spectral density was the largest when the main frequency was 1.6 Hz; the frequency for the peak value of power spectral density of overturning moment of head train was within 20 Hz and main frequency was 0.57 Hz. When the cross wind speed was 15 m/s, all safety indexes of the high-speed train running at the speed of 250 km/h were within the range of limited values and satisfied design requirements. Aerodynamic performance of the high-speed train with the suction chamber under the cross wind was computed and compared with original results. Aerodynamic force and force moments of the high-speed train under cross wind will be reduced obviously and running safety of the high-speed train can be improved through application of the suction chamber.
Highlights
With the continuously increased speed of the high-speed train, the lateral aerodynamic performance of high-speed trains has attracted more and more attention
In order to show real performance of the high-speed train as accurately as possible and make computation and analysis convenient, the rational hypotheses were made during establishing the multi-body dynamic model of the high-speed train: 1) Front and rear bogies of the same train body had the same structure and parameters, while they were symmetrical to the train body center; 2) Components including bogies, framework, wheel set and train body were deemed as rigid bodies, while other elastic deformation was not considered; 3) Only the irregular excitation of steel tracks was taken into account, where its elastic deformation was not taken into account
It was clear that train speed was a main factor affecting the size of positive pressures of train and cross wind velocity had no obvious impacts on the positive and negative pressures of train body
Summary
With the continuously increased speed of the high-speed train, the lateral aerodynamic performance of high-speed trains has attracted more and more attention. Liu studied the running safety characteristic of the high-speed train under the action of unsteady aerodynamic forces under cross winds based on large eddy simulation (LES) method and SIMPACK software [15, 16]. This paper combined the aerodynamics of the high-speed train with system dynamics to study the transient aerodynamic response and safety of the high-speed train under cross winds. This paper established a multi-body system dynamics model for the high-speed train, took aerodynamic loads as external loads, loaded them to the multi-body system dynamics model for computation, and studied the impact of cross winds on the safety of the aerodynamic performance of the high-speed train. According to the basic thought of DES, RANS was adopted at the boundary layer near wall surface, and turbulence model was used to simulate small-scale fluctuations. Computational model for the aerodynamic performance of trains under cross-winds
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