A review of air drag related freight train aerodynamics part 2: Energy efficient designs

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 2 focuses on drag reduction methods, which has identified a range of methods can be used to reduce air drag. These are grouped into loading arrangements and wagon modifications. The former involves container arrangements for intermodal trains and bulk loading arrangements for heavy haul and mixed trains. Wagon modifications can be end treatments, fairing, smooth surfaces, baffles/dividers, and top covers. They have different drag reduction performances range from less than 1% to multi-fold drag reductions. Cost benefits should also be considered while assessing these methods. The industry has strong interests into retrofitting and small modifications that can bring considerable drag reduction. A comprehensive review was carried out; the published drag reduction performances are discussed and presented in tables. 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.