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Strong crosswinds can cause catastrophic accidents like overturning and derailment in extreme circumstances, therefore the train's capacity to tolerate their impacts is crucial. Despite the significance of this issue, there exists a notable research gap in understanding the specific effects of various positions of a high-speed train within a tunnel on its aerodynamic loads and flow structure under different crosswind conditions. To address this gap, numerical simulations were performed using computational fluid dynamics. The crosswind angles (Ψ) were 15°, 30°, 45°, and 60° and the number of coaches exiting the tunnel was one to three coaches, respectively. The incompressible flow around the train was simulated using the Unsteady Reynolds-Averaged NavierStokes (URANS) equations in conjunction with the k-epsilon (k-ε) turbulence model. The Reynolds number employed in the simulation was 1.3 x 106, calculated based on the height of the train and the freestream velocity. With regard to aerodynamic performance due to the crosswind, force coefficients such as drag, side, and lift and moment coefficients of rolling, pitching, and yawing were measured. The higher crosswind angles including ψ = 45° and ψ = 60° cases produced the worse results of aerodynamic load coefficients compared to the lower crosswind angles of ψ = 15° and ψ = 30°. For instance, the highest side force coefficient (Cs) was recorded at a crosswind angle of ψ = 45°, with a value of 23.6. Meanwhile, the flow structure revealed that the leading coach of the train experienced intricate flow patterns during crosswinds, characterized by vortices and flow separation. These findings indicate that aerodynamic instabilities can potentially affect the overall performance of the train. Additionally, this increases the risk of derailment or overturning to be high, particularly when the majority of coaches are exiting the tunnel under strong crosswind conditions. [ABSTRACT FROM AUTHOR]

Through the comparison and analysis of three numerical simulation methods, the optimal simulation scheme was obtained. Therefore, the separation vortices method was used to study the aerodynamic characteristics of Ahmed model, and the influence of different side wind angles on the distribution law of vorticity, turbulence intensity, pressure and streamline of blunt body wake was analyzed. The variation characteristics of force and moment coefficient were obtained, and the comprehensive formula of tail inclination angle changing with side wind angle was summarized. The results show that the influence of the side wind angle on the characteristic parameters of the blunt body wake is not monotonous, and the rear vorticity of the blunt body is the largest when the side wind angle is 30°. The inclination angle and aerodynamic coefficient of the wake of the blunt body increase with the increase of the side wind angle. Back windward side pressure and average head speed of the blunt body also reach maximum values at a side wind angle of 50°. The conclusions provide some basis for the safety and stability of vehicle operation under complex transverse inflow conditions. [ABSTRACT FROM AUTHOR]

To enhance the cooling capacity of a single air inlet induced draft cooling tower (SIDCT), the stepped fill layout pattern is proposed in this paper. A three-dimensional numerical model is established and validated by field measurement data. The cooling capacity of towers equipped with uniform fill and stepped fill is compared under various crosswind velocities (0 m/s–12 m/s) and crosswind angles (0°–180°). The results showed that the ventilation rate of the total tower with stepped fill is increased. Under the studied crosswind velocity and angle, the cooling capacity of the stepped fill tower is superior to the uniform fill tower. After using stepped fill, the mean drop of outlet water temperature rises by 0.29 °C, 0.27 °C, 0.17 °C, 0.10 °C, and 0.19 °C, corresponding to crosswind angles from 0° to 180°. The increment of cooling capacity is the maximum under the crosswind angles of 0° and 45° and is the minimum under the crosswind angles of 90° and 135°. The maximum increased value of N is 0.65 under the crosswind velocity of 4 m/s, 0.85 under 8 m/s, and 0.95 under 12 m/s.

To enhance the cooling capacity of a single air inlet induced draft cooling tower (SIDCT), the stepped fill layout pattern is proposed in this paper. A three-dimensional numerical model is established and validated by field measurement data. The cooling capacity of towers equipped with uniform fill and stepped fill is compared under various crosswind velocities (0 m/s–12 m/s) and crosswind angles (0°–180°). The results showed that the ventilation rate of the total tower with stepped fill is increased. Under the studied crosswind velocity and angle, the cooling capacity of the stepped fill tower is superior to the uniform fill tower. After using stepped fill, the mean drop of outlet water temperature rises by 0.29 °C, 0.27 °C, 0.17 °C, 0.10 °C, and 0.19 °C, corresponding to crosswind angles from 0° to 180°. The increment of cooling capacity is the maximum under the crosswind angles of 0° and 45° and is the minimum under the crosswind angles of 90° and 135°. The maximum increased value of N is 0.65 under the crosswind velocity of 4 m/s, 0.85 under 8 m/s, and 0.95 under 12 m/s. [ABSTRACT FROM AUTHOR]