Understanding the phenomena of train aerodynamics
26 September 2013 • Author(s): Chris Baker, Director of the Birmingham Centre for Railway Research and Education
In very broad terms, railway aerodynamic effects increase in severity with the square of the speed of the train – and historically came to become of concern as the speed of passenger trains increased beyond around 100km/h. In the first instance, attention was paid to reducing the aerodynamic drag of trains, both to reduce fuel consumption and to enable higher speeds to be achieved. As long ago as 1938, tests were being carried out at the London, Midland and Scottish Railway Research Centre at Derby to measure the aerodynamic drag of Coronation class steam engines, and to investigate smoke dispersion around the locomotive. But a whole series of other issues rapidly became apparent as train speeds of 200km/h or more became common.
The existence of severe pressure transients in tunnels that caused considerable passenger discomfort was investigated in both Europe and Japan. Indeed in the UK aerodynamic speed limits were imposed on some narrow Victorian tunnels where the pressure transients were found to be very severe at higher train speeds.