Aerodynamic pressures around high-speed trains: the transition from unconfined to enclosed spaces

Abstract

The theory and practice of train-induced aerodynamic pressure loads on surfaces near to the tracks is compromised by an incomplete understanding of trains operating in short tunnels, partially enclosed spaces, and next to simple structures such as vertical walls. Unique pressure-loading patterns occur in each case. This work has been carried out to obtain a fundamental understanding of how these loading patterns transition from one to the other as the infrastructure becomes more confined. It also considers the impact of the results on two separate European codes of practice applying to tunnels and other structures. A parametric moving-model study was undertaken, transitioning from the open air to single and double vertical walls, partially enclosed spaces, short single-track tunnels and a longer tunnel. The train model was based on a German ICE2, and was fired at 32 m/s past the structures. Multiple surface pressure tappings and in-flow probes were used, providing the opportunity to assess the three-dimensional nature of the pressure and velocity fields. The experiments successfully mapped the transition between the three loading patterns and isolated the geometric changes. Further loading patterns were discovered relating to the length of the train, the length of the tunnel and the distance from the tunnel entrance. The three-dimensional nature of the pressure was related to the length of the tunnel and the distance from the tunnel entrance. Issues surrounding the lack of provision in codes of practice for short tunnels were discussed.

CFD simulation of train aerodynamics: Train-induced wind conditions at an underground railroad passenger platform

“…train-induced slipstreams in open field (Baker et al, 2006;Sterling et al, 2008) and in confined spaces (Gilbert et al, 2013a(Gilbert et al, , 2013b; effect of crosswinds on trains and the risk of a train to fall over while running in open field Eighinger et al, 2013;Sima and Venkatasalam, 2013); pressure distribution and variation inside tunnels (Baron et al, 2001;Raghunathan et al, 2002;Ricco et al, 2007;Hieke et al, 2013); ballast flying and projection, displacement of ballast stones induced by high speed of a train and damaging train details (Sima et al, 2008;Saussine et al, 2013;Weise and Sima, 2013). Baker et al (2006) and Baker (2010) discussed a number of experimental and numerical studies on the assessment of the slipstream gusts caused by passing trains in open field, with and without cross winds.…”

“…A number of railway stations lie underground and due to the space confinement this results in increased air movements and augmented velocities in front of and behind the running train Gilbert et al, 2013aGilbert et al, , 2013b. Air inside a tunnel is confined by the tunnel walls and, therefore, a compression wave is created in front of the moving train, while an expansion wave is created behind the train (Fig.…”

Enhancing the piston effect in underground railway tunnels

“…They noted that the size of a separation bubble at the train nose increases the effective blockage ratio of the train, which in turn increases pressure peaks, and is influenced by the shape of the nose. Gilbert et al (2013) carried out an experimental study into the gusts generated by trains in tunnels, finding that they are strongly dependent on the length and the cross sectional area of the tunnel. Choi and Kim (2014) investigated increasing the nose length and cross sectional area of a tunnel to reduce the drag of a subway train with reductions of 50% found from either method.…”

Mathematical modeling of aerodynamic processes in railway tunnels on high-speed railways

“…Today, the software allows with sufficient accuracy to predict and to reproduce the aerodynamic processes in the conditions of high speed traffic. Existing methods and their combinations are the main apparatus of researchers who set various tasks, which allows for comparative analysis [3,4,5,6,9,12]. However, many studies contain assumptions, inaccuracy and incomplete dependencies between the geometric and mechanical parameters of a tunnel and a high-speed train and the environment, which can lead to insufficient physical similarity of processes.…”