The flying ballast phenomenon has become an important problem, in the last years, because of the development of high speed trains and the consequent increase of the speed up to 350 km/h. The problem is very complex since it is related to both railway infrastructure and train characteristics and since it involves mechanical and aerodynamic effects. The results of an experimental study carried out on the Italian high-speed railway and on a 1:1 real stretch of the railways in wind tunnel are presented in the paper. The study was aimed to analyze the effects of the height of the ballast level, the stone shape in the upper layer of the ballast and the compaction of the ballast bed on the problem. To this purpose a specific wind tunnel test rig was designed to reproduce in the wind tunnel a flow with the same average characteristics of the one measured on the real line, especially in the region close to the ballast and sleepers. Finally, starting from the results of these tests, possible countermeasures to ballast lifting onset are proposed.
Tank trucks dynamics can get worse because of fluid sloshing in partially filled tanks. During braking manoeuvres fluid sloshing may lead to load transfers causing rear wheels locking up and lose of directional control, while during turnings or lane changes it may cause rollover. In this paper, a methodology for evaluating the interaction between fluid sloshing and vehicle dynamics is proposed. The fluid and the tank are modelled using the CFD code FLUENT, based on the Navier-Stokes equations and incorporating the Volume Of Fluid (VOF) and the Moving Mesh (MM) techniques. The motion of the tank is determined based on the response of a 14 dofs vehicle model subjected to the forces due to the fluid sloshing. Straight line braking manoeuvres and lane change manoeuvres have been carried to evaluate the effects of fill level, baffles and tank shape
The effect of the relative motion between a train and the surrounding infrastructure may result in critical scenarios where the infrastructure has a significant effect on the atmospheric wind. This paper analyses using a computational dynamics approach the variation of the aerodynamic force coefficients on the leading vehicle of a high speed train due to the relative motion between the train and the infrastructure. A limited increase (below 10%) in force coefficients are calculated and a small decrease (below 7%) is observed in the characteristic wind curve computation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.