These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Air resistance is an important factor in the speed performance of high-speed trains. Air resistance increases quadratically with speed, so that at higher speeds the influence of air flow becomes greater and greater. The design of high-speed trains is therefore focused on minimizing air resistance to maximize efficiency. Using modern calculation methods, the main aerodynamic losses of a train have been analyzed and possible optimization approaches were developed. In addition to the primary losses, the overall drag of the train was reduced through suitable shaping. The bogies play a decisive role here with a total share of approx. 25% on the total air resistance of a high-speed train. In high-speed trains bogies do not have any aerodynamic panels now. For the next generation high speed train of Siemens - the Velaro Novo - Siemens wanted to develop the most efficient train possible. Therefor aerodynamic panels for bogies are essential! When developing an aerodynamic housing for high-speed bogies on the one side of course the aerodynamic shape is important to reduce drag. On the other hand, is important to look on the thermal effects of the housing on components. It will be shown in the presentation what steps have been done to develop the optimal aerodynamic shape including side wind and other effects. Here from a model of the whole train boundary conditions are taken to a very detailed model for the shape optimization on only a part model of the train to have more loops in shorter time for the shape optimization. One crucial condition in the development of the housing is that it has to work in both directions of the train. Plenty of simulation have been done to get the best solution. For the thermal effect of the housing a different simulation model has been built to check thermal effects. In-depth thermal simulations play a significant role in ensuring the optimal performance of high-speed trains. These simulations involve various mechanisms of heat transfer, including natural convection, radiation, convection, and conduction. One critical use case in this respect is the emergency braking of high-speed trains with a full housing of bogies and then standing after braking. Here natural convection, radiation and other simulation topics must be solved which are not so easy. To check what happens a thermal model was set up with the help of CFD including all form of heat transfer (conduction, convection, radiation). All material characteristics, all emission and absorption coefficients have to be defined and of course inducing heat in the brakes have to be simulated. Real times needed are 50 minutes and are a challenge for simulation. At the end results show which components need to be focused on when talking about thermal stresses. The synergy between aerodynamics, CFD, and thermal simulation is essential in the development of high-speed trains. These technologies enable engineers to design trains that not only travel at remarkable speeds but also provide a safe, comfortable, and efficient transportation solution. As we look to the future, continued innovation in these fields will drive the next generation of high-speed rail systems, bringing us faster and more sustainable travel options.