Prediction of Cross-Wind Stability for a Generic Train

Abstract

External aerodynamics has not been widely established in the rail-vehicle industry until recent years. Nonetheless, the subject is of fundamental importance in some respects, e.g. aerodynamic loads due to the head-wave or the slip-stream of a train, running resistance and cross-wind stability. The latter is the dominating safety issue when attention is drawn to high cruising speeds. The objective of this study is to scrutinise the predictive prospects of unsteady, scale resolving Detached Eddy Simulations (DES) for cross-wind train aerodynamics. Attention is restricted to a mirrored pair of generic end cars of the German ICE2 high-speed train. The example included refers to a yaw angle of 30° and a Reynolds number - based on the length of the first car - of Re ≈ 107. Computational results are reported for DES, supported by companion steady and unsteady RANS simulations and windtunnel measurements. More comprehensive consequences on the stability of the vehicle are briefly addressed by means of a quasi-static mechanical analysis. The aerodynamic loads obtained from the DES approach are in fair agreement with experimental data and outperform RANS predictions slightly. Results indicate that — in terms of the maximum allowable cross-wind speed — the predictive failure returned by DES corresponds roughly to only 1% of the actual value. Moreover, DES provides some insight into potential risks for an excitation of natural frequencies due to cross winds, which might detract the riding comfort.