High-Speed Train Aerodynamics

Passing trains can exert significant aerodynamic loads on each other. These loads can produce stress on passenger car windows and can produce reduced wheel/rail loads on the train being passed. These effects are of greater concern at higher train speeds. A sensible approach to studying the aerodynamic loads for passing trains is to use CFD to analyze a variety of scenarios. However, the changing geometry of the passing trains (due to their relative motion) and the unsteady airflow makes numerical solutions difficult. Thus, it is important to verify CFD solutions with experiments wherever possible. In response to the need for experimental data to verify CFD calculations, under the direction of the Department of Transportation, ARA performed experiments designed to gather pressure-time histories on a stationary freight car as a high-speed train passes. The experiments recorded transient static pressure at several locations on the stationary car, thus allowing partial verification of the total forces on the car predicted by CFD simulations.

Figure 1 shows the instrumented double stack container car next to the High Speed Non-Electric Locomotive (HSNEL) used during the test. The containers were instrumented with 9 pressure transducers on the side closest to the HSNEL while two more sensitive gauges were mounted on the container far-side.

Recorded pressure histories compared to CFD calculations are shown below in Figure 2. For the measured data, the HSNEL was traveling at approximately 130 mph. One can see generally very good agreement between the CFD calculation and the predicted pressure histories. Discrepancies between the measured data and CFD prediction are due to geometric and solution scheme simplifications used in the CFD model. Still, the differences are small and the model predicts the peak pressures and the character of the pulse very well.

The large scale dynamic CFD calculations illustrated in the passing train problem and be applied to related problems including the passing of highway vehicles, the dynamic pressures generated by fan blades, and vortex shedding in marine and other environments.

References:

• MacNeill, R.A., Holmes, S., and Lee H.S., "Measurement of the Aerodynamic Pressures Produced by Passing Trains," Proceedings of: JRC2002, The 2002 ASME/IEEE Joint Rail Conference, Washington D.C., April 23-25, 2002.
  Abstract

For inquiries or comments, please contact:
Robert MacNeill
Principal Engineer
e-mail: rmacneill@ara.com