# Dynamic Response of Outer Windshield Structure in Different Schemes under Aerodynamic Load
## 1 Introduction  
With the continuous improvement in the speed of passenger train operation, the fluid drag force acting on the train body increases significantly, leading to more energy consumption [1; 2; 3]. A smooth design of the HST body surface is important for setting the exterior windshield at the connection between train carriages, which can effectively reduce the aerodynamic resistance and aerodynamic noise of the connecting parts of vehicles [4; 5; 6], and reduce the energy consumption of the train operation. When the train passes through a curve, the distance between the adjacent carriages changes. The outer windshield of the carriage end is usually made of rubber material with certain elasticity and stiffness, or a certain gap is reserved for the outer windshield, which provides a safe offset distance for the relative movement of the train carriage. Owing to its good curve passing ability and drag and noise reduction characteristics, the windshield is widely used in HSTs, as shown in Figure 1.  
It is known that the airflow around the HST is within a turbulent state when the train runs at high speed, especially at the connection between carriages [7, 8, 9, 10]. The flow separation produces a great quantity of vortices, and the movement and development of the vortices at the end of the carriage leads to the external windshield being subjected to complex and strong aerodynamic load [11, 12, 13]. Owing to the stiffness and strength of rubber, which is much lower than that of metal materials, under the action of strong pulsating airflow around the connection of HST carriages, large deformation, vibration, and damage of the rubber outer windshield structure frequently occurs [14, 15], seriously affecting the train running stability and reducing driving safety. At present, research on HST windshields mainly focuses on aerodynamic drag, aerodynamic noise, and surrounding flow-field structure of the external windshield, and little work is focused on the FSI characteristics between the external windshield and the complex aerodynamic loads. [PERSON] et al. [16] studied the aerodynamic performance of an exterior HST windshield at the running speed of 350 km/h and compared the effect of different schemes of the exterior windshield structure on the aerodynamic resistance of the train by full-scale testing and numerical simulation. [PERSON] et al. [17], through the numerical simulation of one-eight-scale HST models with different gap spacing between adjacent vehicles, found that different external windshield gaps have significant effects on the airflow structure and aerodynamic drag of train models. [PERSON] et al. [18] researched the gangway noise of the carriage connection, and noise mitigation methods were suggested. It was found that the additional fairings structure blocked the influx of air in the carriage connection gap, and noise in the cavity was reduced by 8 \(\sim\) 10 dB at 300 km/h. [PERSON] [15] introduced that installing a full circumference hood between the carriage of FASTECH series trains can effectively suppress aerodynamic noise that occurs in the spaces between railcars. The relaxation state of the rubber exterior windshield, however, changes with train operation speed. [PERSON] et al. [4] adopted a hybrid method to study the aerodynamic noise around the windshield region between carriages, and the results show that a full-windshield form is better for noise reduction, which apparently reduces the overall sound pressure level on the near-field sides. [PERSON] et al. [19] utilized the improved delayed-detached eddy simulation (IDDES) to resolve the flow field around the outer windshield by using different installation gaps (10, 20, and 30 mm). The aerodynamic forces on different windshield components, turbulent flow fields around the train-end area, and the corresponding low-dimensional modes were analyzed.