Flow topology of a container train wagon subjected to varying local loading configurations

Abstract

How the positioning and length of a container placed on an arbitrary train wagon in an otherwise fully loaded train affects the local aerodynamics, and consequently the contribution to drag, is examined here. Results from scale-model wind-tunnel tests undertaken at a Reynolds number of 0.3 × 106 for a combination of 49 upstream and downstream gap spacings (Gf,Gr) are presented. Surface flow topology, pressure profiles and planar velocity fields are measured. Gf dominated the drag variations, with Gr only causing a secondary effect. The greatest drag reduction potential is found between gaps size of 1.77W and 3.23W, where W represents the wagon width. Over the range of Gf and Gr investigated, a number of distinct physical mechanisms were observed. These affect the separation size and the nature of boundary layer enveloping the wagon, which have a direct impact on the entrainment and shedding frequency of the wake.