Technical Reports

Aerodynamic Forces on Various Configurations of Railroad Cars and Carrying Trailers and Containers

  • 01
  • Jan
  • 1979
AUTHOR: Andrew G. Hammitt
OFFICE: RPD
REPORT NUMBER: FRA/ORD-79/39
SUBJECT: Facilities & Test Equipment, Freight Operations, Evaluation
KEYWORDS: Intermodal, TOFC, PIggyback Aerodynamics, Train Resistance, Wind Tunnel Testing
ABSTRACT: Toward improving the energy efficiency of rail intermodal service, the aerodynamic characteristics of the rolling stock offer a significant opportunity for betterment. At speeds above 45 miles per hour more than half of the resistance of an intermodal train is caused by the aerodynamic drag of the cars and their loads. Methods by which the aerodynamic drag may be minimized are, therefore, of considerable interest to railroads and car designers. This report covers the wind tunnel testing of scale models of railcars for carrying trailers and containers. The purpose was twofold: First, to determine whether significant differences in the aerodynamic characteristics of such scale models could be measured in the wind tunnel showing that it could be utilized as an evaluation tool in future railcar design programs and, second to obtain comparative performance data on five new intermodal railcar configurations. The findings confirm that wind tunnel testing is a viable design evaluation method. The cost of this series of tests was about $9000 for the wind tunnel utilization, about $20,000 for the models plus a nominal amount for the data analysis and report preparation. Compared to full scale testing, wind tunnel testing, therefore, requires only minimal resources. From the data collected, differences between the aerodynamic characteristics of existing and developmental configurations are apparent. Worthy of particular note is the influence of air moving across the train as denoted by yaw angles of values other than zero. Combinations of train speed and ambient air movement which produce a resultant relative wind vector of 10¬į or greater were shown to increase aerodynamic drag by as much as 75% on some configurations. Reduction of susceptibility to crosswinds therefore, appears to be a high-payoff design goal for new intermodal railcars.
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