Projects
Ongoing projects of the Waves and Dynamics Research Group are within the following research areas.
- Elastic wave propagation in periodic and non-periodic structures
- Nonlinear elastic metamaterials
- Marine energy harvesting, including from ocean waves
- Stochastic systems and related phenomena, including the stochastic resonance phenomenon
- Nonlinear dynamics of parametric amplifiers, energy harvesters and mineral processing equipment
- Novel passive and semi-active strategies of vibration control
More information on ongoing projects can be found on each of the Team members‘ page.
There are several projects available for new PhD students, briefly described below. If you are interested, please contact us.
Uncertainty and Nonlinearity: How to harness these for effective sound and vibration attenuation?
From footfall noise on the floor above you, to aircraft vibrations transmitted into the cabin, controlling structural vibrations is a key engineering challenge. While benefits of adding nonlinearity to a vibration suppression system have been shown before for simple, 1DOF systems, the issue of improved control of broadband vibration transmission using nonlinearity is largely unaddressed. The inevitable existence of uncertainties, for example in properties or attachment locations, of manufactured vibration suppression elements is another key factor that needs to be accounted for. The aim of this project is to develop a new passive method of attenuating noise and vibration transmission in mechanical structures by exploiting nonlinearity of attached elements, with robust performance that is maintained even in the face of uncertainties. By understanding the effects of uncertainties on the overall dynamic behaviour, the intention is to exploit these effects further by the deliberate, designed addition of variability to improve the vibration attenuation performance.
A conventional passive method of attenuating vibration and sound transmission in structures and materials involves discrete linear attachments, such as vibration neutralizers or tuned mass dampers. However, these devices are fundamentally governed by the mass ratio between the elements and the overall structure, lower mass in the elements resulting in poorer attenuation. This limitation along with manufacturing complexity has limited uptake from industry.
Previously, it was shown that variability (uncertainty) in properties and locations of discrete linear vibration suppression elements or scatterers can be beneficial for vibration transmission attenuation. For structures with (discrete) nonlinear attachments, effects of variability, inevitable in real systems or introduced intentionally to improve vibration attenuation performance, remain unstudied.
Research question: how to design sound and vibration attenuation methods for structures under effects of uncertainty and nonlinearity? The project implies studying, on a fundamental level, effects of nonlinearity and uncertainty on noise and vibration transmission in structures to lay the foundation for developing new passive vibration control methods important to the building, aerospace and other industries.
Sound and vibration attenuation in periodic structures with spatially varying stiffness, mass and damping properties
Analysis of elastic wave propagation in periodic structures is a popular research topic, and such structures are extensively used for vibration attenuation purposes, e.g., to secure certain parts of technological devices or constructions from vibrations. This is accomplished by employing the characteristic feature of periodic structures that is the presence of frequency bandgaps, frequency ranges in which travelling waves attenuate. The frequency bandgaps occur due to two different physical mechanisms, 1) Bragg scattering, related to multiple wave scattering leading to destructive wave interference, 2) Local resonance, when the vibrational energy of the hosting structure is transferred into vibrations of resonant attachments, such as masses on springs. Examples of periodic structures featuring Bragg scattering bandgaps include beams and rods with periodically varying cross-sections and plates with varying thickness. Typically, when analysing the Bragg scattering bandgaps, the periodic structure is assumed to be undamped. However, real structures feature inherent damping and for periodic structures it can vary with spatial coordinates. The present project aims to reveal the effects of spatially varying damping on wave propagation in periodic structures and Bragg scattering bandgaps. In particular, we aim to reveal whether periodic structures with properly arranged stiffness, mass and damping variations can outperform conventional periodic structures with only stiffness and mass variations. The project implies both theoretical and experimental studies. The Method of varying amplitudes combined with Physics-informed neural networks will be used for theoretical prediction and optimisation of dispersion relations and Bragg scattering bandgaps. The obtained results will be tested experimentally for a rod, beam or plate with periodically varying properties (cross-sectional area).
Other available PhD projects include
Using high frequency vibrations to control elastic properties of structural elements
Energy harvesting in linear and nonlinear elastic systems exposed to combined parametric and direct excitations. Applications to micro- and nanoscale electromechanical systems
Thermal metamaterials with advanced heat transfer properties
Tribo-electro-magnetic generator for wave energy converters
Tidal energy for powering marine aquaculture farms