Citation

Vardy A. J. Adv. Transp. 1979; 13(3): 61-83.

Copyright

(Copyright © 1979, Institute for Transportation, Publisher John Wiley and Sons)

DOI

unavailable

PMID

unavailable

Abstract

The use of flow restrictions is proposed as a method eliminating some of the pressure changes which are a potential source of passenger discomfort in railway tunnels. Flow restrictions in railway tunnels could have a highly beneficial influence on the pressure experienced by passengers on trains. An adjustable restriction at the exit portal of a tunnel could be used to eliminate the nose-exit wavefront and also the reflection of the nose-entry wavefront. Additionally, a restriction at the tail of a train could eliminate the tail-entry and tail-exit wavefronts. It is argued that geometrical blockages are the most sensible type of restriction at both of these locations. Theoretical predictions obtained from a numerical solution of the one-dimensional equations of motion are shown to be in satisfactory agreement with experimental evidence. The theoretical model is therefore used to optimize the utilization of the restrictions. It is found that the exit portal restriction should be capable of very rapid adjustment. If it is, the pressure histories can be improved so much that no sudden pressure changes are experienced by passengers. The pressure histories are then composed solely of ramp charges in pressure which are due to skin friction on the train and tunnel surfaces.