Simulation of Circumferential air flow around Parsi Passenger Train under the influence of Crosswinds

Compared to the past, derailment prevention for a majority of railway machineries is now a more important task. Crosswinds are amongst the reasons for the derailment of the railway vehicles. Combination of the moving train and the turbulent transient flow of air causes complexity in the air flow domain. This can expose the rail vehicle to sever instability and increases the oscillations in the resultant aerodynamic forces and momentums. Interaction between such loads and the vehicle dynamics can cause instability problems. This can eventually lead to the derailment of the vehicle. On the other hand, to comply with the never ending demand for increasing the speed of travel, lighter materials are used in the structure of the railway vehicles. Combination of the lightweight and the increased speed of travel adds to the anxiety about the stability of the train. Such anxieties amplify especially when the vehicle is subjected to crosswinds.
This paper deals with the numerical simulation of the air flow surrounding the moving railway vehicle (Parsi coach) under the influence of crosswinds. Computational fluid dynamic engineering software is used. The aerodynamic forces and momentums for a variety of deviation angles and conditions of turbulence are calculated. The pattern for the flow of air around the vehicle and the pressure distribution on the vehicle surface are also calculated. Effects of the relative distance between the vehicles are also investigated. The most appropriate and practical distances between the vehicles are suggested. It is observed that doubling the speed of air that is directed at a yaw angle of 8 degrees, causes an increase of 4-45% in the corresponding aerodynamic coefficients.