A review of air drag related freight train aerodynamics part 1: Assessment methods

Air drag characteristics for freight trains have unique features and play important roles for rail decarbonisation. This study reviews relevant issues including aerodynamics, assessment methods and drag reduction methods. Due to the comprehensiveness, the review is presented as two parts. This part 1 covers freight train aerodynamic characteristics and assessment method. The research indicates that inter-wagon gaps and wagon end profiles significantly influence air drag of the downstream wagons. Vortex shielding effects in small gaps help to reduce drag for downstream wagons, and open top empty wagons. Combinations of physical tests (wind tunnel or full-scale) and numerical simulations provide good methods for air drag assessments. Empirical formulas and look-up tables can be used for other related research such as train dynamics simulations and loading optimisation. Further research topics are proposed; the findings not only provide valuable insights for researchers and engineers but also emphasise the need for continued research in this area.