| Nowadays, the speed-up of transportation vehicles has been made with the timely requirements for a safe and bulk volume of transportation. High-speed rail (HSR) is a type of passenger rail transport that operates significantly faster than the normal speed of rail traffic. It can easily reach speeds from400to450km/h in safety conditions. However some meteorology phenomenon such as crosswind and strong rain can generate negative effects on the running safety of the train travelling in high speed train. The work here presented intends to be contribution on the current research of high-speed modern’s vehicles as well to give input in the understanding of the critical externalities of these systems such as:economic feasibility, environment feasibility and technology feasibility. The aerodynamics of high-speed trains is linked not only to efficiency but to the key issues like safety and how these perform under extreme weather conditions and other external factors.Aerodynamic influences on the high speed train due to heavy rain and crosswind are still an on-going research subject, and needs further investigations. Hence, this project thesis aim set out to1) analyze the speed ranges within safe operational values and performance;2) Give input to the research on the effects of heavy rain in high speed train systems and increase knowledge about this decisive safety matter;3) analyze the surface pressure distributions and their influence on the geometric design and performance;4) analyse the results and validate with previous researches as conceptual and theoretical framework. In this context the available knowledge and research here presented opens lines of discussion for further improvementThe theory and calculations about aerodynamics, fluid mechanic, fluid dynamic, numeric analysis, computational fluid dynamics and multi-flow analysis here performed consider the flow around a train’s body to be under the influence of crosswind and rain. These parameters were analyzed from multiphase flow mixture model theory, the turbulent realizable k-epsilon model, the polyhedra mesh and standard wall function. The tools and computational platform used was the ANSYS WORKBENCH-FLUENT software for simulation using a high-end desktop PC client. The selected geometry design was done with a standard CAD platform integrated with Inventor from Autodesk and Nx7.5(Unigraphic) as the mechanical design platform.The current project uses three sizes of cells:1824488;2285764and3555243respectively. These were selected based on computing and time availability constraints. In this sense a train performance’s is partially determined by its mechanics but moreover by external conditions such as crosswind and rain. For the crosswind design-parameters a fixed range was selected:24m/s,20m/s,16m/s,10m/s,4m/s. Regarding the rainfall constraint a fixed value of60mm/h was used with a raindrop5m/s; these were taken again from previous researches. Concerning the mesh design theory and model a y+wall function was set between range of30<y+<60for critical parts of the train such as the rear and front parts. For the rest of the train the selected range was120<y+<200given the computational power constrains.In short terms, the following conclusions have been drawn:· According the computations requirements, the computation domain of type cylindrical and the mesh of type polyhedral are the most suitable for the simulation.· The results showed that highest and lowest pressures around the train are located in the nose and rear parts of the train.· The drag force, side force, lift force, rolling moment, and yawing moment increased significantly under crosswind and rain conditions.· The results show that the system works in unsafe conditions under rain conditions. Hence, it has a high probability the derailment and overturning.· In order to avoid possible distortions in the results such as inverse flow and low residual solution scale. The computational domain size, relaxation factors, and discretization method are critical factors in the simulation. |
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