This paper presents unsteady aerodynamic results of crosswind stability obtained numerically for the class 808 leading control unit of Deutsche Bahn AG's high-speed train Inter-City Express 2. The effects of two linearly increasing gusts are explored by means of Detached Eddy Simulation (DES), where the yaw angle of the flow goes from a basic wind of 8.1943 deg to a maximum wind of 23.3644 deg. The rise times of the gusts correspond to 1.3073 and 2.6146 vehicle lengths (0.5 and 1 sec at the train speed of 250 km/h), which are chosen with respect to the potential excitation of the natural car body frequencies regarding the vehicle dynamics. In total, one DES and three Delayed-DES (D-DES) are carried out with the commercial code STAR-CD, using three background turbulence models, k-epsilon, k-omega SST and Spalart-Allmaras, on two meshes adapted for high- and low-Reynolds number wall modeling about the vehicle surfaces. The results show a satisfactory level of coherence, where results are indirectly verified against wind tunnel data and Reynolds Averaged Navier Stokes (RANS) results of the basic and maximum wind. Admittedly, the results of the D-DES using the k-omega SST turbulence model are questionable in that the turbulence prediction on the lee-ward side seems deficit. However, the level of the principal loads agrees well with the other DES and RANS. It is demonstrated that the drag force, the pitch moment and in particular the yaw moment overshoot significantly (depending on the gust properties) compared to the steady results, which may have implications on the vehicle stability. Assessing the unsteady effects of numerous gusts on various vehicles may seem prohibitively expensive from a computational point of view. To overcome the bottle neck of the indeed compute intensive DES, a Quasi Transient Gust Modelling technique is invented and tested somewhat satisfactorily using the linear gusts. The aerodynamic effects of exiting a tunnel and the gust used in European TSI are subsequently explored with this technique. The results of particularly the TSI gust are very instructive, as it shows significant unsteadiness of the kind that is not taken into account in the current standard.
Unsteady aerodynamic crosswind stablity of a high-speed train subjected to gusts of various rates
Instationäre, aerodynamische Seitenwindstabilität eines Hochgeschwindigkeitszuges, der Böen unterschiedlicher Geschwindigkeit ausgesetzt ist
2009
12 Seiten, 13 Bilder, 1 Tabelle, 16 Quellen
Conference paper
English
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