000022508 001__ 22508
000022508 005__ 20170724144652.0
000022508 04107 $$aeng
000022508 046__ $$k2017-07-04
000022508 100__ $$aFlynn, Dominic
000022508 24500 $$aThe aerodynamic flow beneath a high speed train: A numerical and experimental analysis

000022508 24630 $$n7.$$p7th European and African Conference on Wind Engineering 
000022508 260__ $$bl'Association pour l'Ingénierie du Vent
000022508 506__ $$arestricted
000022508 520__ $$2eng$$aIn the operation of high-speed trains, ballast stones on the track bed sporadically lift off which damages the underside of trains, trackside barriers and rail heads. This phenomenon is known as ‘ballast projection’. Because ballast projection occurs intermittently it is difficult to observe during operation. The exact mechanisms that cause ballast projection are not fully understood, although from the available evidence it is thought to be due to a combination of sleeper movement and aerodynamic effects. To investigate the aerodynamic aspect of ballast projection the flow beneath a high speed train has been investigated using full-scale tests, moving-model experiments and numerical simulations in order to better understand the flow beneath the train. Results show excellent agreement between the full-scale test results and physical modelling results. However the results from the CFD simulations show some overshoot in both pressure and velocity in comparison to the experimental work. This is hypothesised to be due to the influence of the modelled wall roughness in the physical model that was not replicated in the CFD simulations. INTRODUCTION High speed railways now exist in the majority of developed nations and allow trains to operate at speeds of over 300 kph. In countries such as South Korea and China train speeds have steadily increased over time and the infrastructure is now capable of coping with train speeds approaching 400 kph. Aerodynamic effects increase proportionally with train speed squared, consequently at higher speeds these effects will be significantly greater than for trains travelling at lower speeds. Ballast projection is the phenomenon by which ballast particles become airborne during the passage of a high speed train and was first observed on Japanese and Korean high speed railways [1]. Flying ballast particles can cause damage to the underbody of trains and to the rail head if crushed between a wheel and the rail. Figure 1, replicated from Quinn et al. [2], shows ballast pitting damage as a result of a ballast particle being crushed between the wheel and the rail head. Ballast flight is also known to cause damaged wheel sets, broken glass in stations and damage to trackside acoustic screens. The work presented in this paper is part of a collaborative project with the University of Southampton to investigate the geotechnical and aerodynamic influences of the ballast projection phenonenon. This paper contains a description of the physical modelling, numerical simulations and full-scale experimental tests.

000022508 540__ $$aText je chráněný podle autorského zákona č. 121/2000 Sb.
000022508 653__ $$a

000022508 7112_ $$a7th European and African Conference on Wind Engineering$$cLiège, BE$$d2017-07-04 / 2017-07-07$$gEACWE2017
000022508 720__ $$aFlynn, Dominic$$iBaker, Chris$$iHemida, Hassan$$iJackson, Adam$$iSoper, David
000022508 8560_ $$ffischerc@itam.cas.cz
000022508 8564_ $$s1131895$$uhttps://invenio.itam.cas.cz/record/22508/files/20.pdf$$yOriginal version of the author's contribution in proceedings, id 20, section .
000022508 962__ $$r22493
000022508 980__ $$aPAPER