Numerical study of the influence of synthetic turbulent inflow conditions on the aerodynamics of a train

The necessity of a more complete definition of the turbulent wind acting on a train is studied in this paper using computational fluid dynamics (CFD). A stochastic approach for the modeling of turbulent winds is proposed here. Synthetic winds are defined based on two different spectral models, namely the Kaimal spectrum and the Kraichnan spectrum. These are generated using Turbsim and ANSYS-FLUENT software, respectively. To complete the comparison, a third oncoming wind definition is considered, corresponding to a uniform (low-turbulence) wind. Large-Eddy Simulation (LES) and Scale-Adaptive Simulation (SAS) turbulence models have been used for the numerical simulation. Comparison is made of the average, standard deviations and extreme values of the loads calculated with the different methods. The corresponding flow fields are also studied and compared. The transient behavior is analyzed using the spectra of the velocity and loads, and the aerodynamic admittance curves. The results obtained for the last inlet condition are in good agreement with previous studies, while the importance of the spectral model choice is evidenced in the analysis of the velocity and force spectra, as well as in the aerodynamic admittance curves.