Influence of Marshalling Length on Aerodynamic Characteristics of Urban Emus under Crosswind

Urban electric multiple units (EMUs) is based on high-speed trains and metro vehicle technology. Their design speeds are generally from ۱۶۰km/h to ۲۰۰km/h, which mitigates the low operating speeds of metro vehicles. Traditional crosswind calculations for the aerodynamic characteristics of trains often assume a ۳-marshalling train. Urban trains are generally ۴-marshalling and ۶-marshalling. Evaluating the aerodynamic characteristics of urban EMUs of different marshalling lengths is instructive for system design. Based on CFD, aerodynamic models of urban trains are established. The train models include ۳-marshalling, ۴-marshalling and ۶-marshalling. The aerodynamic characteristics of ۲۰۰km/h urban trains subject to different crosswind velocities are numerically simulated. The research display that the aerodynamic performance of the head-car and the first middle-car, under the same crosswind velocity, of different marshalling lengths, are almost the same, whereas the aerodynamic characteristics of the tail-cars for different marshalling lengths are significantly different. The side forces of the ۴ middle-cars of the ۶-marshalling train decrease, sequentially. At a crosswind velocity of ۳۵m/s, ۳۴% difference in Fs of the tail-car of a ۶-marshalling train compared to a ۳-marshalling, and the overturning moment differs by ۲۲.۸%. Because of the significant difference in side force and overturning moment, the three-marshalling train model cannot represent the real train. Therefore, the real marshalling length should be used, as far as possible, when studying crosswind effects on the train.

Keywords:

Crosswind , Marshalling length , Train aerodynamics , Urban trains , Numerical simulation