https://www.um.edu.mt/library/oar/handle/123456789/138214 2026-04-14T22:31:50Z https://www.um.edu.mt/library/oar/handle/123456789/143783 Title: Examining the effects of different winglet designs on aerodynamic forces using computational fluid dynamics Abstract: The pursuit of better aerodynamic efficiency in aircraft design has led to significant advancements, with winglets being one of the most impactful innovations. Winglets are aerodynamic extensions at the tips of an aircraft’s wings designed to reduce induced drag by minimizing wingtip vortices. This reduction in drag improves lift-to-drag ratios, leading to fuel savings, extended range, lower carbon emissions, and quieter flight operations. Over time, various winglet designs have emerged, including bio-inspired configurations, each offering distinct aerodynamic advantages. While traditional wind tunnel tests remain useful, Computational Fluid Dynamics (CFD) has become essential for optimizing winglet geometry, providing insights into flow fields and aerodynamic forces under various conditions. Despite progress, designing universally optimal winglets remains challenging due to the need to balance lift, drag, structural strength, and manufacturing feasibility. This thesis uses CFD to examine the effects of different winglet geometries on aerodynamic performance, contributing to a deeper understanding of their impact on efficiency. First, an intensive review of the current literature related to CFD studies of winglets was carried out. The different setups used in literature combined with further information obtained through background theory research were used to determine the set up used for the simulations carried out in this thesis. Within this study, no winglet, raked winglet, fenced winglet, blended winglets and split winglet models were analysed. In this thesis, the end section of the winglet attached to the full wing geometry and the end geometry by themselves were analysed and compared. These results provided similar trends for both geometries, with the raked winglet providing the highest lift-to-drag ratio, followed closely by the blended winglet. From this study, the split and fenced winglet provided the lowest values of lift-to-drag ratio meaning that these winglets were the least efficient. Furthermore, to analyse clearly the trailing vortices formed behind the winglet, another set of simulations were carried out with the same geometry and domain, only editing the mesh to be more refined behind the wing. This resulted in a more clear display of the vortices, making it easier to compare how the different winglets effected the formation of these vortices. The effect of the Cant angle on blended winglets was also analysed, to see which model produced the best lift-to-drag ratio. The results were very close to each other. The 45° Cant angle winglet produced the best results, closely followed by the 30° Cant angle model and lastly by the 60° Cant angle model. Description: B.Eng. (Hons)(Melit.) 2025-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/143782 Title: CFD modelling of the indoor unit of an air conditioner Abstract: Air conditioning (AC) systems are crucial for maintaining thermal comfort and indoor air quality. With the growing demand for efficient cooling, understanding AC unit performance is crucial for improving efficiency and reducing operational costs. Monitoring airflow dynamics is key to optimizing system design and energy efficiency. This study investigates the airflow behaviour within a split-type indoor air conditioning (SAC) unit using computational fluid dynamics (CFD) modelling, supported by experimental validation. A two-dimensional transient CFD model was developed in ANSYS Fluent 2024 R2 software to simulate airflow at three different fan speeds. The CFD analysis revealed several critical airflow patterns within the indoor SAC unit, including three major recirculation zones: an eccentric vortex at the periphery of the impeller, a recirculation zone at the intake of the impeller near the rear wall and another at the unit outlet. The eccentric vortex, formed by the interaction between the rotating fan and the stationary vortex wall, created low-velocity regions and reversed flow. Additional recirculation zones formed due to flow disruptions caused by internal components including the rear and vortex walls, while stagnation regions around sharp geometries indicated potential obstructions or redirection of airflow. The recirculation zones contributed to the displacement of the eccentric vortex, thereby reducing discharge efficiency and affecting overall air delivery. The highest velocity occurred along the rear wall due to centrifugal force, resulting in a jet flow that remained attached to the rear wall. Although the shape of the jet flow deviated from typical CFD literature, it was supported by experimental observations, emphasizing the importance of realworld validation. Overall, this study demonstrates the effectiveness of CFD in capturing key airflow behaviours in indoor SAC units and provides a basis for further research on optimizing airflow performance. Description: B.Eng. (Hons)(Melit.) 2025-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/143781 Title: Comparative analysis and validation of different measurement technologies for vertical jump performance Abstract: Force plates (FP) are a primary tool used by the Malta Olympic Committee (MOC) in the Functional Diagnostic Lab (FDL) to assess vertical jump performance in athletes, particularly through the countermovement jump (CMJ) and the multi-rebound jump (MRJ) tests. The main aim of this dissertation is to develop a custom-built software to extract previously unattainable performance metrics from the MRJ test. The double integration method, using numerical trapezium integration, proved to be a viable approach to replicate CMJ performance metrics. However, this method is unsuitable for MRJ analysis due to integration drift, which introduced significant inaccuracies in deriving performance metrics. As a result, the flight time method was adopted as the preferred method for MRJs. The initial version of the software evaluated two force threshold methods to detect the take-off and landing instants. The first method employed a standard deviation method, while the second method applied a 10 N threshold on one leg. Both approaches replicated nearly all the metrics to within a 5% error. Following consultation with the FP manufacturer (Hawkin Dynamics) it was identified that their FP use a 25 N force threshold. Therefore, the final version of the software implemented this threshold which replicated the metrics to a near zero percent error when compared to the FP outputs. A secondary objective is to validate the use of FP using alternative technologies. Three motion capture methods were compared to assess discrepancies in different jump height definitions which resulted in discrepancies ranging from 4 cm up to 16.5 cm. These findings highlighted the importance of defining the jump height relative to the measurement technology used. When comparing the force threshold methods against motion capture technology, the standard deviation method proved most accurate, underestimating jump height by ~0.6 mm on average, and is best suited for symmetrical jumpers. Although the single leg 10 N threshold overestimated jump height by ~6.1 mm and the 25 N by ~4.2 mm, they aligned best with the FP software. All methods produced consistent results across 11 tests. Additionally, the smartphone accelerometer overestimated jump height by ~1 cm, showing improved accuracy over previous research, but was deemed unsuitable for FDL use due to limited reliability and automation. Therefore, the FP were still considered the gold standard for assessing vertical jump performance in the FDL at the MOC. Description: B.Eng. (Hons)(Melit.) 2025-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/141255 Title: Modelling and analysis of the hydraulic energy conversion processes for offshore hydro-pneumatic energy storage systems Abstract: Energy storage systems are imperative for addressing instability issues in the electricity network arising from a high penetration of intermittent sources of renewable energy, such as wind and solar power. The integration of storage will avoid the curtailment of renewable energy production and revenue loss during periods of low energy demand and grid congestion. This thesis investigates the performance of an offshore Hydro-Pneumatic Energy Storage (HPES) system consisting of a subsea accumulator pre-charged with compressed air. Unlike conventional pumped hydro systems, HPES systems operate under a highly variable head. As a result, designing the hydraulic machinery to be able to maintain high energy conversion efficiencies over a wide pressure range is a major engineering challenge. The present study applies numerical modelling to understand the hydraulic performance of a megawatt-scale, topside Energy Conversion Unit (ECU) of an offshore HPES system when used to smoothen the intermittent supply of energy from offshore wind and solar parks. The ECU comprises a centrifugal pump to store excess energy in the HPES system and a Pelton turbine to convert the stored energy back into electricity during periods of low renewable energy production. Three different numerical models are used to investigate the ECU performance: The first model (Alpha) is a quasi-steady state and computationally efficient model of the storage system implemented in PythonTM. The second model (Beta), modelled in MATLAB® Simulink® and SimscapeTM is a more comprehensive model which provides more realistic operation due to the addition of transients, losses and inertias. The third model (Alpha Plus) is the Alpha model that has been upgraded to integrate Time Series Forecasting to simulate a smoothened power output from an intermittent power input. The simulations have shown that the power absorbing capacity of the large scale centrifugal pump is highly dependent on the state of charge (pressure) of the subsea HPES accumulator. Additionally, a single centrifugal pump is limited in its ability to meet the smoothing requirements of the wind turbine when operating under the HPES system’s variable head constrains. While the Pelton turbine model showed excellent operational flexibility over a wide range of pressure and power levels, maintaining a high efficiency over the same wide range with a centrifugal pump remains challenging given that the pressure and power are hydraulically coupled. The final stage of this study involved a techno-economic feasibility assessment of a floating breakwater integrating the proposed HPES system in deep waters. The proposed hybrid breakwater is modelled to generate multiple revenue streams, including the provision of energy storage services to offshore wind and solar parks as well as sheltered waters for facilitating multi-use of space at sea. The hybridisation is aimed at reducing costs for integrating the HPES offshore. However the technoeconomic assessment showed that the overall revenue generation, including that involving the use of the storage system, is insufficient to cover the high investment costs of the hybrid breakwater. Description: Ph.D.(Melit.) 2025-01-01T00:00:00Z