The influence of ballast shoulder height on train aerodynamic flow development

The need for interoperability for rail operators across Europe has led to the development of the Technical Specifications for Interoperability (TSI); a series of regulations for railway operation, including safety limits for train aerodynamics. Safety limits are calculated within a set of guidelines, including environmental conditions, train speeds and ballast shoulder height. There are however many cases on the European rail network which fall outside the ballast shoulder height limits, raising questions about the suitability of the TSI limits. This paper describes a detailed set of model-scale experiments carried out at the University of Birmingham's moving model TRAIN rig facility to assess the influence of ballast shoulder height on aerodynamic flow development around a train. A typical UK train type was tested to investigate the influence of ballast shoulder height in relation to the experimental framework set out in the TSI. Analysis of maximum 1 second moving average gusts calculated using the current TSI methodology indicated values did not break existing TSI limits. The largest slipstream velocities were found for the configuration with no ballast shoulder modelled. The effect of increasing the ballast shoulder height was shown to decrease slipstream velocities away from TSI limits.