flow behind a train

The influence of the aerodynamics on small objects around the high speed trains

Assist. prof.: Sinisa Krajnovic
Project leader: Lars Davidson
Cooperation: Bombardier Transportation
Sponsors: Banverket
Publications: -
Start of project: January 2005




The aim of this project is to investigate how the aerodynamic effects caused by the flow around the high speed train influence small objects in the vicinity of the train. During last few years, large number of damages on the trains caused by the stones and other smaller objects below and around them have been observed. Also in Sweden several damages have been reported on the Swedish high-speed trains Regina and X2000. These were attributed to the flying objects. The damages were broken windows and imprints on the train body. Both these trains have top speed between 180 - 200 km/h. The possible explanation for these damages is that the train lifts the stones from the ground which then hit the train.

There are two possible explanations for this phenomena:
  1. As the pressure under the train is dependent on the velocity of the train, it is possible that when the train reaches some velocity the small objects (such as stones) are lifted from the ground toward the train.
  2. Flow streams under and especially behind the train pull the stones from the ground and suck them toward the train (so called 'Slipstream effects').
Irrespective of which of these explanations is the correct one, we need a thorough understanding of the flow around the train.

The first study aims to identify the important mechanisms in the flow around trains that can produce flying objects (such as stones) causing damages on trains. We shall use the time-dependent simulations such as Large Eddy Simulations and unsteady RANS simulations. The results of simulations will be used to determine the time-dependent forces around the trains and to explain the mechanisms that can produce flying stones around the trains. The knowledge obtained in this project will be used to improve our understanding of the flows around trains and to help engineers to design better trains and railways

Preliminary simulations have been carried out. Below one instants when a stone hits the underbody of the train is shown.
flow behind a train

This page, The influence of the aerodynamics on small objects around the high speed trains, should be part of a frames system at www.tfd.chalmers.se/~lada/projects/proind.html
Ingalena Ljungström