Aerodynamic/Train System Interactions |
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Named Investigators: Dr Simon Iwnicki (Manchester Metropolitan University); Prof Chris Baker (University of Birmingham)
Researchers: Dr A Bouferrouk (University of Birmingham); Dr Javier Perez (Manchester Metropolitan University)
Industry Collaboration and Mentors: Bombardier; Network Rail; RSSB; Siemens
Background:
Around the world there is a general trend of increasing train speeds, which brings a number of associated problems. One of these is the increasing significance of aerodynamic forces, because their magnitude increases roughly with the square of train speed. In the past the major aerodynamic concern of train designers has been the aerodynamic drag force, the magnitude of which relates directly to the traction requirements and energy consumption. However in recent years the importance of a number of other aerodynamic forces of an unsteady or transient nature has come to be realised.
A recent RSSB scoping study has identified effectively three types of aerodynamic forces on trains that are of continuing concern:
- The forces and moments on trains due to high cross winds which can, in the extreme, cause vehicles to overturn, and can also cause vehicle and load displacements that potentially, particularly for freight trains, can infringe the kinematic envelope
- The transient forces caused by passing high speed trains, which can result in high transient loadings on train structural members
- The transient forces on train structural members due to the pressure pulses that occur as trains pass through tunnels
These issues all have major safety implications and are becoming of increasing concern to the railway industry. The RSSB review of current work in this field broadly identified two areas in which fundamental research is required – the specification of the unsteady aerodynamic loads on trains for a variety of situations, and the determination of how these loads interact with the train system.
Brief Summary of Research Methods:
- Determination of aerodynamic forces from analytical methods and previous work.
- Analytical simulation of cross wind characteristics and the resulting forces
- Use of analytical cross wind forces in VAMPIRE model of train, with realistic track simulation
- FE simulation of transient aerodynamic forces in train frames
Original Project Scope and Objectives:
- To review current knowledge on the unsteady aerodynamic forces on trains
- To specify appropriate analytical/numerical formulations of the unsteady loading due to cross wind effects, the effects of passing trains, and the pressure transients in tunnels
- To develop a model of train dynamic systems that enables inclusion of the effects of unsteady aerodynamic forces and can be used to predict resulting vehicle displacements
- To develop a model of the internal vehicle forces due to unsteady aerodynamic force input
- To utilise the above formulations of unsteady aerodynamic loads and models to investigate the effects for a variety of different wind speeds, train passing speeds, tunnel sizes etc
- To research and develop methods to link aerodynamic forces on railway vehicles with the dynamic behaviour of the vehicle such that aspects of the behaviour relating to derailment, passenger comfort and structure gauge infringement can be simulated effectively.
Work Done – including statement of key findings to date:
- Development of analytical models for cross wind forces on trains, and simulation of cross wind force time histories
- Inclusion of these forces within VAMPIRE model and determination of running conditions that involve risk in terms of vehicle roll over and flange climb derailment.
Work to date has concentrated on cross wind effects, and these aspects of the first three objectives have been achieved.
Work Remaining:
Future work will begin to look at sudden pressure transients, and then move onto objectives 4 and 5 which will look at FE modelling of aero forces in train frames. These models will be applied to assess the vehicle behaviour in various running conditions This work will more than consume the remaining staff resources and it is likely that the original project scope will have to be trimmed somewhat.
Outputs: