Simulating rolling noise on ballasted and slab tracks: vibration, radiation, and pass-by signals
Doctoral thesis, 2022
Shifting to rail-bound freight and passenger traffic is key in Europe's strategy towards transport decarbonisation. However, increasing railway traffic can increase environmental noise pollution. Rolling noise is often the dominant noise source. It originates from the interaction of the rough running surfaces of wheel and rail. Predicting rolling noise and performing acoustic optimisation of existing and new tracks requires validated, flexible, and physics-based prediction tools. This is especially relevant for the different designs of ballastless tracks, which are increasingly used for high-speed lines. Therefore, this thesis aims to develop and implement a modelling approach for rolling noise in the time and frequency domain to increase understanding of sound radiation, investigate noise mitigation measures, and allow research of the perception of transients in rolling noise.
To achieve this, models for vibration in wheels and several types of ballasted and slab tracks have been implemented using the Waveguide Finite Element method. This method allows an efficient prediction of the track vibration up to high frequencies. Next, models for the sound radiation from wheel and track were implemented using adaptions of the Boundary Element method (BEM), such as the Fourier series BEM and the wavenumber domain BEM.
The computational efficiency was addressed in multiple ways. Finally, an approach to simulate the sound produced at a stationary track-side receiver has been developed and implemented based on moving Green's functions. The simulations were largely implemented in in-house Python code. The ballasted and slab track dynamic models have been tuned and compared with measurements on full-scale tracks.
The developed models have been used to analyse the vibrations in track and wheel and the acoustic radiation from these vibrations. This allowed the investigation of noise mitigation measures. Further, the necessary complexity of the dynamic track model for predicting rolling noise in time domain was investigated. Two parameter studies were carried out with a focus on track design with lower noise emission. Slab tracks with booted sleepers showed a potential for noise reduction without increasing loads on the track structure. A continuous rail support lowered the radiated sound power at high frequencies. The contributions of different wheel modes to the radiated sound were investigated considering the directivity of each mode, and dominant modes were identified. The established models produce time signals usable for auralisation, which, among others, has the potential to research human perception of transients in rolling noise.
To achieve this, models for vibration in wheels and several types of ballasted and slab tracks have been implemented using the Waveguide Finite Element method. This method allows an efficient prediction of the track vibration up to high frequencies. Next, models for the sound radiation from wheel and track were implemented using adaptions of the Boundary Element method (BEM), such as the Fourier series BEM and the wavenumber domain BEM.
The computational efficiency was addressed in multiple ways. Finally, an approach to simulate the sound produced at a stationary track-side receiver has been developed and implemented based on moving Green's functions. The simulations were largely implemented in in-house Python code. The ballasted and slab track dynamic models have been tuned and compared with measurements on full-scale tracks.
The developed models have been used to analyse the vibrations in track and wheel and the acoustic radiation from these vibrations. This allowed the investigation of noise mitigation measures. Further, the necessary complexity of the dynamic track model for predicting rolling noise in time domain was investigated. Two parameter studies were carried out with a focus on track design with lower noise emission. Slab tracks with booted sleepers showed a potential for noise reduction without increasing loads on the track structure. A continuous rail support lowered the radiated sound power at high frequencies. The contributions of different wheel modes to the radiated sound were investigated considering the directivity of each mode, and dominant modes were identified. The established models produce time signals usable for auralisation, which, among others, has the potential to research human perception of transients in rolling noise.
Railway rolling noise
Numerical modelling
Green's functions
Time domain
Spherical harmonics
Slab track
2.5D FE/BE
SB-H2, Architecture and Civil Engineering, Sven Hultins Gata 6, 41258 Gothenburg, Sweden
Opponent: Prof. David Thompson, Institute of Sound and Vibration Research, University of Southampton, United Kingdom
Author
Jannik Theyssen
Chalmers, Architecture and Civil Engineering, Applied Acoustics
Sound Radiation from Railway Wheels including Ground Reflections: A half-space formulation for the Fourier Boundary Element Method
Journal of Sound and Vibration,; Vol. 493(2021)
Journal article
Calibration and validation of the dynamic response of two slab track models using data from a full-scale test rig
Engineering Structures,; Vol. 234(2021)
Journal article
The Influence of Track Parameters on the Sound Radiation from Slab Tracks
Notes on Numerical Fluid Mechanics and Multidisciplinary Design,; (2021)p. 90-97
Book chapter
Transport gives people access to education, goods, jobs, and other services and contributes to fulfilled lives. However, today, transport relies to over 90% on fossil fuels and is one of the main drivers of human-made climate change. We need to change how we transport ourselves and the goods we consume. Part of the solution is to increase the share of railway traffic, because trains are much more energy efficient than cars, trucks, and planes. Electric trains can also be independent of fossil fuels.
However, more railway traffic also means more people might be exposed to railway noise. Therefore, we need to better understand how railway noise is produced, how people are affected, and how tracks and vehicles can be designed to minimise this noise. Railway noise is mainly rolling noise produced by the wheels and the track, which vibrate when the wheels roll over the rails because their contact surfaces are not perfectly smooth. The frequency range from 20 Hz to 8000 Hz is most relevant for high-speed trains. Simulation tools can help us to, for example, find the best ways to build new railway lines so that these vibrations are absorbed efficiently.
This thesis presents a simulation tool to predict rolling noise from trains. Predicting the vibration of the wheel and the track at such high frequencies can be computationally costly. A numerical method called the Waveguide Finite Element method is used to model the rail and entire slab tracks to overcome these difficulties. Comparing with measurements of real tracks showed that the approach is suitable for modelling the track vibration. Predicting sound radiation can be equally demanding. By adopting suitable variants of the Boundary Element method, the sound field produced by wheel and rail vibrations can be computed with high resolution. This high resolution is relevant for the final step in the simulation, the simulation of the sound that a wheel moving on a rail produces at a position on the side of the track. This step is realised by so-called moving Green's functions.
This simulation tool has been used to investigate sound radiation from different tracks, with the goal of limiting the noise emitted by the tracks. By tuning certain track parameters, the noise radiated from the track could be reduced. The presented approach makes it possible to listen to the sound that is produced when a wheel rolls over a rail, which a lot of other models do not allow. Certain effects in railway noise, such as noise impulses at crossings, are assumed to be more annoying than noise levels can capture. The modelling approach in this thesis allows us to study these effects in future research.
However, more railway traffic also means more people might be exposed to railway noise. Therefore, we need to better understand how railway noise is produced, how people are affected, and how tracks and vehicles can be designed to minimise this noise. Railway noise is mainly rolling noise produced by the wheels and the track, which vibrate when the wheels roll over the rails because their contact surfaces are not perfectly smooth. The frequency range from 20 Hz to 8000 Hz is most relevant for high-speed trains. Simulation tools can help us to, for example, find the best ways to build new railway lines so that these vibrations are absorbed efficiently.
This thesis presents a simulation tool to predict rolling noise from trains. Predicting the vibration of the wheel and the track at such high frequencies can be computationally costly. A numerical method called the Waveguide Finite Element method is used to model the rail and entire slab tracks to overcome these difficulties. Comparing with measurements of real tracks showed that the approach is suitable for modelling the track vibration. Predicting sound radiation can be equally demanding. By adopting suitable variants of the Boundary Element method, the sound field produced by wheel and rail vibrations can be computed with high resolution. This high resolution is relevant for the final step in the simulation, the simulation of the sound that a wheel moving on a rail produces at a position on the side of the track. This step is realised by so-called moving Green's functions.
This simulation tool has been used to investigate sound radiation from different tracks, with the goal of limiting the noise emitted by the tracks. By tuning certain track parameters, the noise radiated from the track could be reduced. The presented approach makes it possible to listen to the sound that is produced when a wheel rolls over a rail, which a lot of other models do not allow. Certain effects in railway noise, such as noise impulses at crossings, are assumed to be more annoying than noise levels can capture. The modelling approach in this thesis allows us to study these effects in future research.
Buller från ballastfria spår
Swedish Transport Administration, 2017-01-01 -- 2018-12-31.
Driving Forces
Sustainable development
Areas of Advance
Transport
Subject Categories
Applied Mechanics
Fluid Mechanics and Acoustics
Infrastructure
C3SE (Chalmers Centre for Computational Science and Engineering)
ISBN
978-91-7905-756-5
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5222
Publisher
Chalmers
SB-H2, Architecture and Civil Engineering, Sven Hultins Gata 6, 41258 Gothenburg, Sweden
Opponent: Prof. David Thompson, Institute of Sound and Vibration Research, University of Southampton, United Kingdom