Diffusion–diversion wind barrier for high-speed train protection passing real terrain

This study, based on real terrain in Xinjiang, China, examines a novel wind barrier known as the diffusible diversion case (DDC) and compares its effectiveness in protecting moving trains from crosswinds to that of the original porous case. It utilizes the Unsteady Reynolds-Averaged Navier–Stokes equations along with the Trimmed Mesher for numerical simulations. Two-stage wind tunnel experiments are conducted to verify the method's accuracy, and the movement of the train is achieved through a sliding mesh. Results show that upon reaching the maximum crosswind speed point, the DDC reduces side forces on the head, middle, and tail cars by 22.76%, 8.44%, and 30.38%, respectively, due to decreased pressure differences. During this moment, the pressure differences between the windward and leeward sides of the head, middle, and tail cars drop by 24.48%, 25.95%, and 14.44%, respectively. Meanwhile, with DDC's assistance, the airflow on the windward side of the train undergoes a three-stage redirection, becoming constrained to the bridge deck area and slowing down. The airflow entering the bogie cavity shifts from predominantly horizontal to predominantly vertical, with lateral components decreasing by 60.93% and 69.33%. The intense negative pressure zones on the leeward side fade and rapidly separate from the train body. Moreover, the DDC releases crosswind energy from the wake flow either on the windward side of the train region or outside it. The separation line, which shifts toward the windward side along with an expanded reverse flow area, indicates the optimization of asymmetric vortex shedding in the wake.