Computational fluid dynamics simulation of rail vehicles in crosswind: Application in norms and standards

The application of computational fluid dynamics (CFD) to the determination of aerodynamic coefficients for crosswind stability in the context of vehicle assessment has been studied as part of the AeroTRAIN project. The work consisted in establishing best practice guidelines for the use of standard Reynolds-averaged Navier–Stokes (RANS) approaches using a streamlined and less-streamlined vehicle, project partners applying different computational codes and turbulence models to a common vehicle, and then application to further vehicles in order to cover a range of different vehicles and yaw angles. The simulations were complimented with wind tunnel measurements to allow the accuracy of standard RANS approaches to be judged for various vehicle shapes and yaw angles. This paper summarises the overall results and the recommendations made for the use of CFD in vehicle assessment of crosswind stability in relation to the EN 14067-6: 2010 standard. The main aspects of the guidelines are reported in a separate paper in this special issue. The considered standard allows the use of CFD for vehicle speeds up to a maximum of 200 km/h whereas the HS RST TSI (2008) only allows aerodynamic coefficients to be determined using wind tunnel measurements. The obtained results show that a well-performed RANS CFD can predict the aerodynamic coefficient of streamlined trains with a relatively high accuracy. The challenges increase for blunter-shaped trains and may be further influenced by equipment installed on the roof of a train. Combined with the developed simulation guidelines it is considered that CFD can be used as an alternative to wind tunnel tests in all cases provided that the accuracy of the approach is validated on a benchmark train with similar features to those of the simulated train.