Numerical Simulation of Passenger Train Aerodynamics in Tunnels
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Date
2017-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
In the present study, an analysis to investigate the aerodynamic drag and related pressure
characteristics of the passenger train traveling in tunnel is performed. In particular, the effect of
aerodynamic loads on the Ethiopian National passenger train at speed of 120 km/hr operating in
open field and as it travels through in currently constructing Addi-onfito tunnel with 179m length
is analyzed. The aerodynamic drag and pressure loads developed on the train are estimated and
compared; while the train is moving in open field and while the train travels in the tunnel. In
addition the study also investigated the effect of the blockage ratio of an underground train upon
the aerodynamic drag and pressure developed on a train body, by altering the train-tunnel gaps.
The investigation uses computational fluid dynamics techniques (CFD). First a numerical
simulation was developed to estimate the aerodynamic drag and peak pressures on operational
passenger train operating in open filed and underground railway with existing tunnel crosssectional
area
and
blockage
ratio
which
is
currently
under
construction.
The
results
of
the
study
show
that
in
existing
high
blockage
ratio
underground
railways,
the
pressure
acting
on
the
train
body
experienced
huge
fluctuations
as
the
train
moved
along
the
current
Addi-onfito
tunnel.
The
maximum
pressure
change
(∆��
������
) on the train body reaches around the value of 4.36 kPa, which
exceeds the maximum admissible limit of change in pressure on train body travelling in tunnel.
There is significant increment of the aerodynamic drag approximately 3.65 times that of the train
in open field. Peak-pressures experienced are also greater on all train position when the train
travels in the tunnel as compared to the train travelling in open field. Then the blockage ratio of
the underground railway is varied (by increasing the train-tunnel gaps) to evaluate the effects
upon aerodynamic drag and pressure developed. The simulation results shows that due to
reduction of the blockage ratio by 12.19% of train in tunnel the value of maximum pressure change
(∆��
������
) on the train body reduced to around 3.20 kPa, which satisfy the maximum admissible limit
of change in pressure on train body travelling in tunnel. Due to reduction of blockage ratio; the
magnitude of the drag force decreased by 28.46% at constant train speed and tunnel length. These
results of reduction of aerodynamic drag and pressure is enormous indicating that without
affecting the shape and speed of the train one can save 28.48% of aerodynamic power
requirements by little modification of the blockage ratio.
Description
Keywords
Train, Tunnel, Blockage ratio, Aerodynamic drag, Pressure, Velocity