Effects of streamline-blunted aerodynamic braking plates on turbulent flow around a high-speed train with and without yaw angle

This study employs the improved delayed detached eddy simulation (IDDES) method to investigate the aerodynamic characteristics of a high-speed train (HST) equipped with streamlined-blunted aerodynamic braking devices under crosswind conditions at yaw angles of 0° and 15°, with a Reynolds number of 5.0 × 105. The accuracy and reliability of the numerical simulations were validated against scaled wind tunnel experiments conducted at the same Reynolds number. Aerodynamic forces, pressure distributions, and flow field characteristics were systematically compared and analyzed for four cases: 0° OC, 0° BC, 15° OC, and 15° BC. The results indicate that IDDES provides a reliable tool for numerically evaluating the aerodynamic performance of braking devices under both open-air and crosswind conditions. At a yaw angle of 0°, deploying aerodynamic braking plates significantly enhanced the positive pressure distribution on the head car and the negative pressure distribution on the tail car. Consequently, the overall pressure drag increased substantially, leading to a marked rise in aerodynamic drag. Compared with the original configuration (OC), the drag coefficients of the head and tail cars increased by approximately 364.65% and 354.46%, respectively, resulting in an overall aerodynamic drag increase in about 235.4%. At a yaw angle of 15°, owing to reduced interference among some braking plates, the braking plates contributed even more to aerodynamic drag than in the 0° yaw case. Specifically, relative to the 0° yaw case, the drag increments of the head and tail cars further increased by approximately 103.15% and 60.63%, respectively, resulting in a total aerodynamic drag increase in about 334.47%. Moreover, crosswind conditions significantly altered the surface pressure distribution on the original high-speed train, producing positive pressure on the windward side and negative pressure on the leeward side and roof. With the deployment of braking plates, the total lateral force on the train increased by approximately 13.67% compared with the original configuration, while the lift force decreased by about 5.04%.