https://bura.brunel.ac.uk/handle/2438/33746 Thu, 08 Oct 2026 17:02:58 GMT 2026-10-08T17:02:58Z https://bura.brunel.ac.uk/handle/2438/33914 Title: Additive manufacturing for microscale heat exchangers operating in flow boiling Authors: Bekir, Enes; Askounis, Alexandros; Karayiannis, Tassos G Abstract: Micro scale heatsinks provide a promising thermal solution for high-power electronic components. However, the capabilities of current top-to-bottom subtractive manufacturing techniques are constraining the production of complex geometric features required for optimised micro-scale heatsink designs. Thus, additive manufactured heatsinks are introduced as a bottom-up alternative for producing complex surface geometries. The effect of these two different manufacturing techniques, particularly surface characteristics and their effect on heatsink performance, should be evaluated. Sun, 06 Sep 2026 00:00:00 GMT https://bura.brunel.ac.uk/handle/2438/33914 2026-09-06T00:00:00Z https://bura.brunel.ac.uk/handle/2438/33910 Title: EFFECTS OF CEMENT CONDUCTIVITY ON THE THERMAL PERFORMANCE OF AGS SYSTEMS Authors: Kalkisim, AT; Yavuzdogan, A; Ozturk, Z; Sewell, P; Karayiannis, TG Abstract: Geothermal energy applications have gained significant importance within the renewable energy sector. This growth is caused primarily by supply constraints in fossil-fuel-based energy sources. Recent advancements focus on developing various techniques to extract subsurface heat. Advanced designs and innovative materials are constantly emerging to support these novel applications. This highlights the necessity to carefully analyse all system components. Closed-loop geothermal systems also referred to as Advanced Geothermal Systems (AGS), can be configured in various design methods to extract this energy. This study evaluates the influence of casing cement thermal conductivity on the thermal performance of closed-loop systems. The study compares three cement options using fixed design parameters as low-conductivity (0.8 W/mK) and high-conductivity (2.8 W/mK), and a hybrid model. Also, the surrounding rock formation is modelled with a homogeneous thermal gradient along the wellbore, analysed both for low (35 K/km) and high (75 K/km ) thermal gradient scenarios. The results demonstrate that varying cement thermal conductivity impacts the overall thermal output by 8.3 to 12.6%. The hybrid configuration provides a further 1 to 1.5% improvement compared to uniform high conductivity cement, demonstrating the benefit of selecting cement conductivity based on the local direction of heat transfer. Sun, 06 Sep 2026 00:00:00 GMT https://bura.brunel.ac.uk/handle/2438/33910 2026-09-06T00:00:00Z https://bura.brunel.ac.uk/handle/2438/33871 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 Thu, 01 Jan 2026 00:00:00 GMT https://bura.brunel.ac.uk/handle/2438/33871 2026-01-01T00:00:00Z https://bura.brunel.ac.uk/handle/2438/33858 Title: Integrating LLM-based agents with uncertainty-aware optimization for water-energy-carbon nexus management in irrigation districts Authors: Yu, Lei; Li, Zhikai; Huang, Kai; Li, Fulin; Lu, Zixiang; Fan, Yurui; Jiang, Yanan; Zhang, Chenglong; Fu, Guangtao Abstract: Efficient irrigation water use is vital for food security, economic returns and ecological protection, yet it faces multiple uncertainties within the water-energy-carbon (WEC) nexus. Conventional optimization models are often limited by complexity, lack of interpretability, and poor alignment with routine management. This study develops an LLM-agent driven intelligent optimization framework for WEC-coupled irrigation management. The framework comprises three sequential agents: a task analysis agent that converts natural language instructions into standardized model configurations; an algorithm execution agent that runs a scenario-based multi-objective fuzzy-credibility constrained programming model (integrated with NSGA-III and AHP-TOPSIS); and a result analysis agent that interprets optimization outputs, compares alternative schemes, identifies trade-offs, and generates structured decision reports. A hybrid LLM setup uses DeepSeek-V4-Flash for task parsing and Qwen3.6-Plus for decision analysis. Applied to four instruction types (standard, punctuation-free, swapped word-order, and ambiguous scenarios), the framework achieved 100% task completion without manual intervention, demonstrating efficiency in automated parsing, execution, and reporting. In the Zhaokou Yellow River Diversion Irrigation Area Phase II, the framework quantified critical management trade-offs. Under the 75% hydrological frequency, increasing the credibility level from 0.5 to 1.0 increases water shortage by 9.43×10⁶ m³, pollutant emissions by 0.18×10³ tonnes, carbon emissions by 0.05×10⁶ tonnes, and decreases net economic benefit by 2.56×10⁶ CNY. By improving accessibility and interpretability, this framework offers an interactive decision-support pathway for irrigation water management under hydrological and parametric uncertainties. Description: Data availability: The data that has been used is confidential.; Supplementary materials are available online at: https://www.sciencedirect.com/science/article/pii/S0043135426014144?via%3Dihub#sec0018 . Sat, 15 Aug 2026 00:00:00 GMT https://bura.brunel.ac.uk/handle/2438/33858 2026-08-15T00:00:00Z