Impact pile driving is the predominant foundation technique for offshore wind turbines. The pressure waves generated during pile driving produce high noise levels that can harm marine life. To protect marine mammals, regulations have been established to limit underwater noise. Recent monopile installations already surpass these limits, necessitating noise mitigation measures to proceed with piling operations. As monopiles and hammers grow larger, noise levels are expected to increase further, escalating the need for effective noise mitigation strategies.

The ongoing evolution of offshore technologies makes it essential to understand the behavior and effectiveness of noise mitigation measures and to develop accurate models for predicting their performance. Currently, limited predictive models exist for most noise mitigation techniques, and it remains unclear how their efficiency will be affected by future piling conditions. As monopiles and hammers increase in size, the noise they produce shifts toward lower frequencies, challenging the effectiveness of current mitigation measures.

This study addresses these knowledge gaps by investigating the performance of existing noise mitigation measures under future piling conditions. A numerical model is developed using the Finite Element Method in COMSOL for near-field analysis, coupled with the Boundary Element Method in SILENCE for far-field analysis. Four categories of noise mitigation measures are examined: the bubble-curtain, a resonator-type mitigation screen, an isolation casing, and pulse prolongation. A critical piling scenario -designed to maximize noise propagation- serves as the baseline for analyzing the individual and combined effectiveness of these measures. Additionally, the scenario is re-simulated with softer soil conditions to assess how environmental factors influence mitigation efficiency.

Key findings reveal that most noise mitigation measures are more effective at attenuating higher frequencies. However, as monopiles become larger and stiffer, natural frequencies decrease, while greater hammer strikes and deeper waters enhance the propagation of lower frequencies. These changes result in a general decline in mitigation efficiency for future piling scenarios. Furthermore, the efficiency of each measure is highly dependent on the frequency content and environmental conditions, such as soil stiffness and water depth. For instance, softer soil conditions significantly alter the effectiveness of certain mitigation measures, with some showing improved performance and others becoming less efficient compared to stiffer soil conditions, and the same goes for combinations of measures.

This study highlights the importance of frequency-specific analyses when applying noise mitigation measures. It underscores the need for tailored approaches to ensure effective noise reduction under varying environmental and piling conditions, offering critical insights into the future of noise mitigation in offshore wind development.

Hyperloop is a new high-speed transportation system currently in development. Utilising an electromagnetic suspension within a low-pressure tube, this approach eliminates the traditional wheel-track friction and drastically reduces the air resistance, targeting speeds up to 1000 km/h. Compared to traditional trains and aeroplanes, the Hyperloop is a more sustainable alternative as it produces no greenhouse gas emissions and uses ten times less energy than road and aviation transportation. The Hyperloop, therefore, has great potential to contribute to the goal of achieving climate neutrality by 2050.

Ensuring the stability of the Hyperloop is a critical challenge in its realisation. Multiple instability mechanisms are present in the system: (1) electromagnetic instability, (2) wave-induced instability, and (3) aeroelastic effects, such as galloping. Additionally, the imperfections in the guideway, make the Hyperloop system prone to parametric instability. This thesis primarily investigates how aeroelastic forces and parametric resonance interact with the electromagnetic and wave-induced instability mechanisms, impacting the overall stability of the Hyperloop system.

Based on the results, it can be concluded that the aeroelastic force destabilises the system, where its impact increases as the velocity rises. As the aeroelastic force continuously injects energy into the system, the unstable domain expands. Furthermore, parametric resonance, represented by ellipse-shaped indentations in the stability planes, is observed when the excitation frequency is twice the natural frequency of the system. Based on the control parameter range used for maglev trains, it is found that the stable domain is narrow, with only a small region prone to parametric resonance. Therefore, choosing the control parameters precisely is essential to prevent instability and parametric resonance.

When examining the combined effect of aeroelastic force and the irregular guideway profile, the results show that the aeroelastic force shifts the overall position of the stability boundaries but it does not affect the parametric resonance regions. Instead, the amplitude of the guideway’s irregular profile influences the size of the ellipses and the stable domain. A larger amplitude leads to an expansion of the unstable domain and an increase in the size of the ellipse; therefore, it is advised to maintain a smooth guideway.

This thesis further evaluates the capabilities of analytical expressions for the simpler 1.5 degree-of-freedom (DOF) electromagnetically suspended mass system by comparing it to systems that incorporate the beam dynamics. The results show that the analytical expressions from the 1.5 DOF system cannot approximate the position of the ellipses for the more complicated systems across all velocities. However, beyond the velocities of $1.3v_{cr}$, the analytical expressions effectively approximate the ellipse size. Notably, while the position and size of the ellipse are influenced by the guideway’s surface roughness amplitude, only the size of the ellipse is affected by the amplitude of the oscillations in the 1.5 DOF system. For the more complicated systems, the analytical expressions of the ellipse size relative to the amplitude provide accurate results, making the simplified system a valuable approach for estimating the ellipse size of parametric resonance in systems with beam dynamics.