Abstract
Understanding fluid-structure interactions (FSI) at various scales is paramount for optimizing performance and ensuring stability in systems characterized by significant fluid and structural dynamics. This thesis addresses the critical role of multi-scale modulation in FSI. By integrating experimental investigations and numerical simulations, this research elucidates the complex interplay between fluids and structures across different scales. The findings bridge theoretical frameworks and practical applications, thereby contributing valuable insights into the design of efficient and resilient systems. This study's outcomes underscore the importance of a multi-scale approach to FSI, highlighting its implications for enhancing system performance and stability.In Chapter 3, a 2D numerical model is developed to simulate the deformation of microcapsule shells under flow conditions. Starting with multiphase flow formulations, the model transitions into an FSI framework to capture the deformation of a core-shell structured microcapsule in a microchannel. Microcapsules for potential drug delivery were fabricated using a needle-based device with PLA bio-based resin for the outer shell and a core mix of deionized water and blue ink. The microcapsules' resilience and stability were demonstrated through compression experiments and numerical simulations under Poiseuille flow and controlled vibration. Chapter 4 develops a 2D numerical model to study fluid-structure interactions in core-shell structured microcapsules within fully developed pipe flow. This model, validated by theoretical calculations, examines the effects of flow velocities and shell thicknesses on stress distribution and deformation, revealing that higher flow velocities and thinner shells lead to increased stress and deformation. Chapter 5 presents novel boundary layer enhancement structures to improve the voltage output of piezoelectric energy harvesters. Using both numerical and experimental methods, the study finds that 6-cylinder and inverse 6-cylinder arrangements significantly enhance performance, with a positive correlation between flow velocity and voltage output. Chapter 6 introduces the Tandem Energy Harvesting System (TEHS), a hybrid energy harvester featuring Savonius rotors with semi-arc-shaped deflectors as bluff bodies for a piezoelectric cantilever beam. Numerical and experimental investigations show that this configuration generates chaotic flow, improving the beam's vibration characteristics and enhancing power output, especially at low inflow velocities. The TEHS can outperform traditional systems by up to 457.67\% under optimal conditions. The combined findings of these chapters provide comprehensive insights into optimizing designs for energy harvesting and drug delivery systems, emphasizing the importance of flow dynamics, material properties, and structural configurations for maximizing performance.
| Date of Award | 13 Jul 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Yong Ren (Supervisor), Xinyu Zhang (Supervisor) & Yuying Yan (Supervisor) |