Investigation of the pressure variation generated by freight train passing through a tunnel

Liu, Zhen ORCID: 0000-0001-9382-1104 (2024). Investigation of the pressure variation generated by freight train passing through a tunnel. University of Birmingham. Ph.D.

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Abstract

As a train passes through a railway tunnel is creates a series of pressure waves, which travel at the speed of sound within the tunnel environment. These pressure waves not only generate aerodynamic loads on freight train body and tunnel infrastructures, but also have an adverse effect on the comfort of people on the train or within the tunnel as the train passes through. There are a range of methods by which to predict the magnitude of these pressure waves, most notably numerical approaches through 1-dimensional (1d) codes.
The bluff nature of a freight train, coupled with large gaps between wagons and loaded goods, influence the pressure wave pattern generated by it passing through a tunnel. This research addresses the intricate challenges associated with predicting pressure wave patterns caused by freight trains passing through tunnels. The accurate resolution of separation regions at the train nose, within containers, and at unloaded gap sections is essential for precise predictions. Achieving this accuracy demands exceptional mesh quality, significant computational resources, and the careful selection of numerical models. This study evaluates various numerical models to capture these complexities in separation regions. It quantitatively analyses how alterations in train head shape and loading configurations influence resulting pressure patterns within tunnels. These insights are synthesised into an advanced 1d computational framework designed to accurately simulate pressure waves generated by partially loaded freight trains. To achieve these goals, firstly a 1d program is developed, validated against published research, and successfully models pressure wave propagation and reflection. The program's accuracy is further enhanced by integrating a separation bubble model. A comprehensive parameterisation study explores the relationship between train head bluntness, blockage ratio, and separation bubble model parameters. These equations are validated and applied to various train types and tunnel configurations. The programme is extended to consider the discontinuities of the train body by implementing a new mesh system and boundary conditions into the 1d programme, and results are validated against LES data. A parameterisation study for different loading configurations improves program adaptability, and the relationship between predetermined parameters and gap length is investigated. This research bridges the gap in freight train tunnel aerodynamics, offering a versatile 1d computational tool for accurate pressure wave prediction.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):