Dynamic instability and discomfort of high-speed trains, in particular induced by aerodynamics in tunnels |
PhD student: |
Lic. Eng. Ben Diedrichs ben.diedrichs@se.transport.bombardier.com |
Project leaders: |
Prof. Mats Berg mabe@kth.se Prof. Evert Andersson everta@kth.se |
Supervisors, fluid mechanics: |
Assist. Prof. Sinisa Krajnovic (main supervisor) sinisa@chalmers.se Prof. Lars Davidson (co-supervisor) lada@chalmers.se |
Partners: |
1. KTH, Division of Aeronautical and Vehicle engineering, Department of Railway
Technology 2. Chalmers, Department of Thermo and Fluid Dynamics. 3. Bombardier, Division of Intercity trains, Department of Specialist Engineering |
Sponsors: | Banverket (Swedish National Rail Administration) and partly by Bombardier Transportation in Sweden |
Publications: | [1,2] |
Start of project: | December 2002 |
Problem description and scope of study The scope of the project is to explore the origin of lateral dynamic instability of high-speed trains related to aerodynamics and vehicle dynamics. These instability phenomena that induce vehicle oscillations can be strong enough to disrupt the passenger comfort and also to yield a more rapid mechanical wear of the rolling-stock and infrastructure. It is also a safety concern. The problem is in much dependent on the factor of aerodynamic forcing over train weight, which has increased for modern trains, especially for non-motorized driving units and double deckers. As the traditional suspension systems are designed to reduce the influence of track irregularities by using soft enough springs and small enough dampers this obviously conflicts situations where forcing are applied directly to the body shell. As far as the aerodynamics is concerned the applied forces and typical forcing frequencies scale with the flow speed squared and linearly, respectively. These basic facts brought together with the discrete natural eigenfrequencies of the vehicle, including the kinematic frequency due to wheel conicity, indicate that critical forcing can arise at some distinct train speeds. Therewith, the apprehension is that aerodynamic phenomena that are undiscovered or under control at lower speeds can quickly manifest themselves under these critical conditions depicted above. One main object of the current project is aerodynamic simulations, see Figs. 1 and 2, and eventually measurements on real trains inside tunnels. The figures show surface pressures and wake flow velocity calculated with Large Eddy Simulations for a 25 m train inside a tunnel. The project will also explore the effects of vehicle motion on the aerodynamics and the interaction between vehicle dynamics and aerodynamics. REFERENCES
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