https://bura.brunel.ac.uk/handle/2438/236 2026-10-18T12:14:28Z 2026-10-18T12:14:28Z Canpolat, Hakan Berk https://bura.brunel.ac.uk/handle/2438/33984 2026-10-13T02:01:06Z 2026-01-01T00:00:00Z

Title: Numerical optimisation of ply orientation for aeroelastic tailoring Authors: Canpolat, Hakan Berk Abstract: This research explores the aeroelastic performance of a composite cantilever wing. The aim is clear: design a structure that resists flutter while staying light. We connect aerodynamic analysis with structural dynamics to reach this goal. First, we run CFD simulations to measure lift and drag coefficients at different flow speeds. We then convert these coefficients into forces. Next, we apply these forces as uniform pressure loads on the wing surfaces in ANSYS Workbench. This step directly links fluid flow results to structural response. We model the structure in both shell and solid forms. Each model captures stiffness and mass differently. The modal analysis reveals the natural frequencies and mode shapes. We track changes in torsional and bending modes as the ply count increases. More plies make the structure stiffer, but the gain slows after a certain thickness. The 8-ply configuration offers the best balance between stiffness, weight, and mode separation. Harmonic response simulations test the wing under realistic oscillating loads. We focus on vibration amplitudes near resonance. We compare multiple stacking sequences, especially for the 12-ply case. Some layups reduce torsion–bending coupling and shift resonance away from critical flight frequencies. One configuration shows the lowest displacement peaks at both 60 m/s and 80 m/s, making it the top candidate. These results give engineers a direct method to link aerodynamic loads with structural vibration data. The workflow is simple, fast, and repeatable. Future work will extend the method to high-speed compressible flows and validate results with wind tunnel experiments. Description: This thesis was submitted for the award of Master of Philosophy and was awarded by Brunel University London

2026-01-01T00:00:00Z Widgington, Joseph Jake https://bura.brunel.ac.uk/handle/2438/33963 2026-10-09T02:00:58Z 2026-01-01T00:00:00Z

Title: Flow boiling of HFE-7100 in a single microchannel Authors: Widgington, Joseph Jake Abstract: The global drive towards electrification and carbon reduction has created an urgent requirement for compact, high-performance thermal management systems capable of dissipating high heat fluxes while maintaining component reliability. Flow boiling in microchannels has emerged as a promising solution due to its high heat transfer capability arising from latent heat effects and large surface area to volume ratios. However, industrial implementation remains limited by incomplete understanding of microscale flow behaviour, heat transfer, pressure drop, and critical heat flux (CHF). Existing predictive methods are often empirical, fluid-specific, and lack general applicability. This thesis addresses these limitations through an experimental investigation of flow boiling of HFE-7100 in a single rectangular microchannel. An experimental facility was designed and constructed to obtain accurate measurements of wall temperature, pressure drop, and high-speed flow visualisation. Two oxygen-free copper test sections with rectangular channels and hydraulic diameters of 0.75 mm were fabricated, with heated lengths of 30 mm and 75 mm to investigate length effects. Experiments were conducted over mass fluxes from 100–1000 kg/m²s, wall heat fluxes up to CHF, and inlet pressures of 1–2 bar. HFE-7100 was selected due to its dielectric properties and lack of prior single-channel flow boiling data. Single-phase validation and uncertainty analysis confirmed the reliability of the methodology. Flow visualisation identified bubbly, slug, churn, and annular flow regimes, with transitions strongly dependent on mass flux, heat flux, inlet pressure, and heated length. Stratified flow was not observed, confirming the confined nature of microscale boiling. Nucleation consistently initiated at channel corners due to geometric confinement. Increasing mass flux and pressure altered bubble coalescence and stability, shifting transition boundaries accordingly. Shorter heated lengths promoted earlier slug formation due to accelerated bubble growth at higher local heat fluxes. Transition maps demonstrated that existing predictive models only partially capture the combined effects of confinement, evaporation momentum, interfacial shear, and geometry. Heat transfer measurements showed that boiling incipience occurred at lower wall superheats with increasing inlet pressure. Heat flux significantly enhanced heat transfer coefficients through increased nucleation activity, while mass flux primarily extended the subcooled boiling region. Higher inlet pressures further improved heat transfer by stabilising nucleation. The 30 mm channel produced higher average heat transfer coefficients than the 75 mm channel at equivalent outlet vapour qualities due to intensified nucleation from concentrated heat input. Nucleate boiling persisted throughout the vapour quality range, limiting the applicability of convective boiling models. Evaluation of twelve existing correlations showed that the best-performing models were those capable of accounting for nucleate boiling dominance. Two-phase pressure drop increased with heat flux due to increased vapour generation and interfacial shear. Increasing pressure generally reduced pressure drop by delaying flow regime transitions through changes in fluid properties. Shorter heated lengths produced steeper pressure gradients due to intensified bubble activity and frictional losses. Existing pressure drop correlations showed considerable discrepancies, although the homogeneous flow model provided reasonable agreement. CHF investigations in the 30 mm channel showed that dryout occurred primarily through liquid film depletion in annular flow. Higher mass flux and pressure increased CHF, with mass flux having the strongest influence due to improved liquid replenishment and bubble removal. Existing CHF correlations performed reasonably well overall but did not accurately capture the weak pressure dependence observed experimentally. Finally, a novel neural network framework for predicting microscale flow pattern transitions was developed. A multi-stage feed-forward neural network architecture was trained using a large experimental database with robust preprocessing, cross-validation, and hyperparameter optimisation. The model achieved an overall classification accuracy of 95.5%, outperforming conventional empirical approaches and demonstrating the potential of data-driven methods for predicting complex microscale two-phase flow behaviour. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2026-01-01T00:00:00Z Naicker, Clinton Jared https://bura.brunel.ac.uk/handle/2438/33871 2026-09-16T02:00:51Z 2026-01-01T00:00:00Z

Title: Computational investigation of installation noise reduction in urban air mobility vehicles using structured porous surface treatments Authors: Naicker, Clinton Jared Abstract: Urban Air Mobility Vehicles (UAMVs) offer a possible solution to the ever-increasing ground-based congestion by utilising the free airspace. However, since these vehicles are expected to operate close to densely populated areas, the noise generated during take-off, landing and low-altitude flight is a major concern, both with respect to certification and public perception. Due to the use of electric propulsion, the contribution of engine noise is reduced, and therefore aerodynamic noise from the rotors, airframe and their interactions becomes increasingly important. This thesis investigates the use of turbulence-resolving Computational Fluid Dynamics (CFD) and computational aeroacoustics to predict the flow and noise associated with UAMVs, alongside the impact of porous coatings for installation noise reduction. The simulations were carried out using OpenFOAM. The computational setup was first assessed using high-performance computing scaling tests, followed by 2-D and 3-D NACA 0012 validation cases. The 2-D Reynolds-Averaged Navier–Stokes (RANS) validation showed good agreement with NASA reference data, with maximum deviations of 2% in lift coefficient and 3.5% in drag coefficient when compared to computational reference codes. The 3-D Large-Eddy Simulation (LES) validation captured the main flow features of the blunt trailing-edge case, including separation, reattachment, transition and vortex shedding. The validated setup was then applied to low-Mach-number aeroacoustic simulations of a tripped NACA 0012 airfoil. The results showed that tripping was required to reproduce the experimental boundary-layer development, and that LES and Zonal LES were able to predict the main flow and acoustic behaviour. In contrast, the Improved Delayed Detached Eddy Simulation (IDDES) produced limited resolved turbulence in the near-wall region and significantly underpredicted the acoustic levels. The acoustic predictions also showed that Ffowcs Williams–Hawkings (FW-H) surface and closing-disc placement had a strong influence on the predicted acoustic spectra. The best placement and closing disc location were identified providing future guidance. Structured porous coatings were then investigated using both fully resolved geometry and reduced-order approaches. Fully resolved LES of a structured porous coated cylinder showed that the coating modified the near-cylinder flow through internal separation, circumferential pore flow, shear-layer diffusion and boundary-layer development on the inner cylinder. A Darcy–Forchheimer approximation was then developed to represent the porous coating at lower computational cost, and was shown to reproduce several of the main wake trends while also highlighting the sensitivity of the results to the selected model coefficients. Finally, the porous coating was assessed for modelled vortex impingement on both a cylinder and an airfoil leading edge. For the cylinder case, the coating diffused the incoming vortex, reduced near-wake turbulence intensity and reduced the Overall Sound Pressure Level by up to 5.8 dB. For the airfoil leading-edge case, the coating weakened the downstream vortex imprint, reduced surface-pressure fluctuations near the leading edge and reduced the Overall Sound Pressure Level at all observer angles, with a maximum reduction of 8.1 dB. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2026-01-01T00:00:00Z Vahid Dastjerdi, Leyli https://bura.brunel.ac.uk/handle/2438/33570 2026-07-13T14:06:53Z 2025-01-01T00:00:00Z

Title: Optimizing of bread quality and sustainability: Evaluating the impact of conventional, microwaves and hybrid baking methods Authors: Vahid Dastjerdi, Leyli Abstract: Baking is a final and one of the most important stages in the breadmaking process, shaping product quality, energy performance, and overall sustainability. Conventional baking methods is widely adopted but it is energy-intensive and often results with uneven heat distribution. This study evaluates the effects of three baking methods including conventional oven (CB), industrial solidstate microwave (IM), domestic microwave (DM) baking, and evaluates the sensorial and physicochemical properties of the resulting breads including moisture content, hardness, colour, specific volume, cell structure, and acrylamide levels, as well as energy consumption, cost, and greenhouse gas (GHG) emissions. A hybrid baking approach, combining CB with microwave baking (applied separately for IM and DM), was also investigated, and the resulting breads were analysed for the same quality attributes. In addition, temperature distribution and moisture variation were monitored during the baking processes for all baking modes. Response Surface Methodology (RSM) was employed to optimise the baking parameters and identify the best baking conditions to maximise improved quality and sustainability performance. The results indicated that IM baked bread achieved the highest moisture content, while domestic microwave led to pronounced moisture loss. Colour analysis revealed that microwave- baked samples developed lighter crusts, whereas CB produced darker crusts due to the higher surface temperatures. Texture analysis showed that IM baking generated softer bread, while DM baking resulted in significantly highest hardness. Although conventional baking achieved the highest specific volume, microwavebaked breads exhibited more irregular crumb structures and lower acrylamide levels. Among all baking modes, IM baking proved to be the most energy-efficient and cost-effective, generating the lowest GHG emissions and therefore representing a more sustainable alternative. It also provided rapid and uniform heating with improved moisture preservation, whereas DM baking caused surface drying and poor internal hydration. Hybrid baking, particularly when incorporating IM, improved thermal uniformity and moisture preservation compared to CB. RSM optimisation further identified IM as the optimal method, achieving highest moisture retention, low hardness, and a desirability score of 0.865. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2025-01-01T00:00:00Z