A field based assessment of the aerodynamics of operational freight trains

Kurzfassung

A novel field based method for analysing the aerodynamic pressure drag acting on intermodal freight trains is presented. A full-scale 48ft shipping container was instrumented with surface pressure taps and loaded onto a number of single and doublestacked container freight trains that operate between Melbourne and Perth, Australia (a distance of 3,500km). Container surface pressure data enabled the instrumented container pressure drag coefficient to be evaluated for a range of different train loading configurations, container positions along the train and atmospheric wind conditions. Field based measurements show that for low wind conditions surface pressure distributions measured on the front and base faces of the instrumented container are synonymous with those reported on in past studies. However, the magnitude of the pressure drag coefficient was found to be approximately 50% lower for all loading cases analysed compared with previous analogous wind-tunnel and numerical investigations. For high wind conditions the drag coefficient was generally found to increase and this change in the drag coefficient was well correlated with the level of asymmetry observed in the measured pressure distributions. In the absence of direct information of the incident free-stream wind conditions, the level of asymmetry in the pressure distributions is found to provide a viable indirect method for assessing the impact that cross-winds have on the aerodynamics of freight trains.