Ms. Howe, Prolongation of the rise time of the compression wave generated by a high-speed train entering a tunnel, P ROY SOC A, 455(1983), 1999, pp. 863-878
Citations number
12
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
An analysis is made of the large-amplitude compression wave formed when a h
ighspeed train enters a tunnel whose entrance is 'vented' by perforations i
n the tunnel walls. The vents are designed to increase the rise time of the
wave in order to alleviate shock formation in a long tunnel by progressive
nonlinear steepening of the wavefront. The wave emerges from the far end a
s an impulsive 'micro-pressure wave', and the presence of shocks increases
its propensity to cause significant structural damage and environmental ann
oyance. Detailed predictions are given for a 'tunnel' consisting of a thin-
walled circular cylinder, of the type frequently used in model-scale experi
ments. A finite length of the cylinder entrance is perforated with an axisy
mmetric distribution of circular apertures. The apertures are equivalent to
a distribution of sources, and it is shown that the profile of the compres
sion wavefront can be greatly extended, so that the wave amplitude increase
s smoothly and linearly, by 'shading' the aperture distribution to make the
effective source strengths approximately uniform along the perforated zone
. The maximum compression wave rise time that can be obtained by this means
is equal to the time of passage of the front of the train through the perf
orated section.