Aerodynamic crosswind stability of a regional train model

This work compares aerodynamic results of crosswind stability obtained experimentally and numerically for a typical regional train model. The experimental work focuses attention on relatively high yaw angles of 30 degrees, 41.5 degrees, 50 degrees, and 60 degrees, whereas the numerical results are confined to 30 degrees and 41.5 degrees that are typically critical for regional trains. In particular, two vehicle models (VM1 and VM2) with different roof configurations are exploited numerically. VM1 has a flat roof with two boxy roof equipments. VM2 has a flat roof where the roof equipments are streamlined. The numerical work addresses the ability to resolve the flowfield around the vehicles subjected to relatively high yaw angles with Reynolds average navier-stokes (RANS) and Delayed-Detached Eddy Simulation (D-DES) by employing the commercial code STAR-CD in conjunction with automatically generated polyhedral meshes of CCM+. High- and low-Reynolds meshes are exploited for this purpose. The massively separated flow, for the higher yaw angles, on the leeward side of the vehicles justifies the use of D-DES, where the results show good agreement with the experimental work. The results of RANS are fair, and the ability to predict the challenging lift force is again found to be problematic.