PhD, EngD and MSc by research theses (SATM)
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Item Open Access Conceptual design methodologies appropriate to electric vertical take-off and landing aircraft in urban air mobility(Cranfield University, 2023-08) Peng, Quan; Smith, Howard; Stockford, JackThis project aims to investigate the current state of conceptual design issues related to electric Vertical Take-off and Landing aircraft (eVTOL) in Urban Air Mobility (UAM). The thesis seeks to develop design methodologies appropriate for eVTOLs and explore the design space for various configurations, including Vectored Thrust, Lift+Cruise, and Multicopter concepts. This project developed a design model for eVTOL within the multi-disciplinary design analysis and optimization environment - GENUS at Cranfield University. The GENUS framework integrates various aerodynamic analysis tools, efficient geometric parameterization methods, semi-empirical mass breakdown models, and effective boundary layer ingestion analysis models. This enables comprehensive conceptual design and design space exploration for novel aircraft, considering real-world considerations. In this project, optimization and comparison are conducted across more than 200 cases involving different aircraft configurations, passenger capacities, battery capacities, cruising speeds, and ranges. Multicopter configurations are suited for short-range, low-speed flights due to the simpler structure and rotor system, despite limitations in range and speed imposed by disk loading and propeller efficiency. Vectored Thrust configurations are suitable for long-range and high-speed flights due to the high lift-to-drag ratio. The Lift + Cruise configuration is versatile due to the combination of lift rotors and propulsion propellers, resulting in higher efficiency for both cruising and hovering. Battery technology is a crucial factor in eVTOL design. With a battery energy density of 300 Wh/kg, the battery weight accounts for approximately 60% of the total weight for a 2-passenger eVTOL undertaking a 200-mile mission. However, at a battery energy density of 900 Wh/kg, the battery weight for a 20-passenger eVTOL performing a 200-mile mission reduces to around 15-20%.Item Open Access Analysis and experiment of a VTOL flapping wing rotor micro aircraft(Cranfield University, 2023-06) Pan, Yingjun; Guo, Shijun J.; Whidborne, James F.This thesis presents an in-depth study of the aerodynamic and structural analysis of a novel bio-inspired flapping wing rotor (FWR) micro aerial vehicle (MAV) capable of vertical take-off and landing. The FWR is characterized by a combination of active flapping motion with passive rotation of the wings in an asymmetric installation to produce a significantly higher lift coefficient than traditional flapping wings. This research is aimed at further enhancing the FWR MAV’s efficiency and aerodynamic performance with flight capability and stability. This is approached by improving the FWR kinematics of motion and mechanism through analytical, numerical simulation, and experimental methods. In the first step, an efficient wing rotation method that allowed a small angle of attack in the downstroke and a larger one in the upstroke was considered. A novel Passive Pitching Angle Variation (PPAV) device, replacing traditional active rotation, was developed and integrated into the flapping mechanism. Using a high-speed camera and a load cell device for experiments, the PPAV-integrated FWR demonstrated a significant increase in aerodynamic efficiency compared to its constant pitch angle counterpart. In the second step, the study focused on enhancing FWR-MAV power efficiency by integrating springs into the mechanism, thereby reducing input power due to the counterbalance between elastic and inertia forces. Numerical analysis and experimentation with an FWR test model were conducted to simulate and measure the resultant kinematics of motion and forces. Specific emphasis was placed on the influence of spring stiffness on the FWR’s aerodynamic and power efficiency. This led to the development of a PPAV-integrated FWR model capable of remote-controlled vertical take-off and hovering. In the third step, the study explored wing flexibility’s impact on FWR’s unsteady aerodynamics using Fluid-Structure Interaction (FSI) analysis and experiments. A novel dragonfly-like wing with a curved sweep-back wingtip demonstrated aerodynamic benefits. The study elucidates the mechanism of wing bending deformation linked to vortex variation, implying that optimal spanwise variable stiffness can enhance lift and power efficiency. Employing flexible wings, the FWR model’s lift significantly increased from 25 g to 51 g, highlighting enhanced efficiency and payload capacity. The study finally explored the FWR-MAV's flight performance and efficiency, including VTOL and forward flight. It proposed a transformable MAV concept from VTOL FWR mode to a bird-like flapping-wing mode in forward flight. A test model was built to validate the transformation concept. Using MSC.ADAMS/Simulink co- simulations and a quasi-steady aerodynamic method, the flights of the FWR model in both flight modes were simulated and stability was demonstrated.Item Open Access Development and design of applications for UAV-based satellite communication terminal antenna evaluation using deep-reinforcement learning(Cranfield University, 2023-08) Omi, Sake; Shin, Hyo-Sang; Tsourdos, AntoniosIn recent years, satellites are launched almost on a daily basis and most of them are to be operated in Non-Geostationary Orbit (NGSO). The number of user terminals communicating with satellites is rapidly increasing. The interference has become a serious issue due to the crowded communication environment and the increased popularity of NGSO. Utilization of NGSO adds more complexity for operating user terminals since it requires tracking the satellite which is not static from the terminals’ points of view. Also, the risk of interference has escalated due to the greater demand for Satellite-communication-On-The-Move (SOTM), which involves the need to keep terminals constantly pointing toward the target satellite while they are installed on a moving object. To ensure a safe communication environment, the terminal antenna must be verified based on set requirements. However, the test process at conventional test facilities is inefficient and does not have a solution to test antennas in the new communication scenarios. Therefore, this thesis aims to develop in-situ Unmanned Aerial Vehicle (UAV) -based measurement applications that are autonomously guided to enhance the efficiency of the measurement and to propose novel measurement methods to verify the antennas operated in new environments. Utilizing UAVs and performing measurements onsite is challenging due to the additional error sources and uncertainties in measurements and sensor positioning. In this work, a new deep-reinforcement learning algorithm is developed which can adapt to the dynamic environment under the presence of disturbances. Using this algorithm, the applications to verify the boresight angle offset of terminal antennas and to evaluate SOTM terminal antennas are proposed. The proposed applications are tested based on the numerical simulations and the results showed that the developed applications improved the efficiency of measurements and satisfied the required measurement accuracy. The thesis investigates novel measurement approaches for a new generation of satellite communication aiming to respond to the measurement demands that currently have no solution.Item Open Access Machine learning (ml) approaches to model interdependencies between dynamic loads and crack propagation(Cranfield University, 2023-09) Omar, Intisar; Khan, Muhammad Ali; Starr, AndrewThe application of machine learning in structural health and crack prediction is of paramount importance, as it offers the potential to enhance the accuracy, efficiency, and reliability of detecting and predicting damage in various materials and structures. This research presents an in-depth exploration of machine learning (ML) applications in the field of Structural Health Monitoring (SHM) across various materials, including composites, metals, and polymers. The study identifies the current challenges in implementing ML in SHM, such as data sparsity, interpretability of ML models, overfitting, and the absence of general guidelines for ML model selection. The research analyses the dynamic response data of different materials and establishes significant crack depth predictors for materials such as aluminum, concrete, and 3D-printed Acrylonitrile Butadiene Styrene (ABS). It further investigates and validates selected ML models to predict crack depth in different materials. The models' performance is evaluated using Mean Squared Error (MSE) on both training and test sets, demonstrating their ability to capture meaningful patterns within the data and make reasonably accurate predictions. A significant contribution of this study is the proposal of an automated model utilizing the H2O library for crack propagation prediction in ABS materials. This model demonstrates the potential of automation in SHM, offering substantial benefits for structural integrity assessment, maintenance strategies, and materials design in various industries. This research concludes with recommendations for future research, including the exploration of advanced ML algorithms, investigation of additional predictive features, and evaluation of the models in different real-world scenarios.Item Open Access Influence of dynamic load and temperature on guided wave ultrasonic damage detection in thin plates(Cranfield University, 2023-08) Olisa, Samule Chukwuemeka; Khan, Muhammad Ali; Starr, AndrewLong-thin metallic materials are essentially used in constructing structures of high economic importance, but their service life is shortened by damage such as cracks, corrosion, cavities, notches, and dents. Damage is an inevitable condition of metallic structures over time and, when not detected, could result in a catastrophic breakdown. In the past decades, high interest has been developed in using the guided wave ultrasonic technique (GWUT) to monitor the health of structures and detect damage due to its long-distance coverage potential with little attenuation and cost-effectiveness. Most guided wave ultrasonic studies have focused on detecting and characterising empty cracks or notches. Limited literature is available to explain the behaviour of guided waves while travelling in thin plates exposed to damage filled with debris, which is more likely possible in long-thin structures such as pipelines for oil, water or gas transportation. Debris- filled damage leads to corrosion processes, particularly inducing pitting corrosion. This form of corrosion is localised and difficult to detect. It has contributed to many structural failures, particularly in oil and gas pipelines. Hence, early detection and characterisation of this form of damage is vital to avert catastrophic failure. This study explored the detection of damage filled with different proportions of debris in thin plates using guided wave ultrasonic techniques. The captured response signals underwent analysis through various signal-processing methods in MATLAB. Additionally, the research examined how temperature variations and low-frequency vibrations impact the guided wave responses, aiming to simulate the effect of environmental operation conditions. Through the analysis, an empirical model was developed to predict debris-filled damage and differentiate it from empty damage and the health state of the structure. The predictive model has an average error of about 1.34. Also, the analysis revealed that cross- correlation of the detrended response and reference signals could demonstrate a quick way to visualise and spot debris-filled damage in the structure. Additionally, a model called Olisa-Khan low-vibration mitigation architecture (Olisa-Khan LMA) was created to counteract the severe effects of varying low- frequency vibrations and improve the performance of the damage detection technique. The average percentage deviation of the model response signal and static response signal was about 1.64 %, suggesting the two signals are very close. The slight deviation could be attributed to the signal loss due to clipping and imperfection in the system. In characterising debris that filled the damage, an excitation signal with a central frequency of 80KHz was found optimal because the deviation of each state of damage differs from the other and decreases from an empty case to a debris-filled case and continues as fluid-filled viscosity increases. The study's merit cannot be overemphasised as it establishes models, especially for predicting novel damage of debris-filled and characterising different debris that filled the damage even in severe environmental operation conditions. Hence, the study would be useful for continuously monitoring long-thin structures of high economic values for possible damage detection and characterisation.Item Embargo Unmanned aerial vehicles as an efficient platform to enable agriculture's digital future(Cranfield University, 2023-05) Mwesigwa, Grace Elisha; Zolotas, Argyrios; Ignatyev, Dmitry I.The potential for Unmanned Aerial Vehicles to revolutionise agriculture, particularly small-scale farms, is enormous. Today, most agriculture UAVs are bulky, expensive, and primarily designed for heavy-lift applications, making them unaffordable for most small-scale farmers. Despite the availability of smaller UAVs, they were not designed for agricultural purposes, and have limited endurance. This project presents an innovative solution that involves integration of cylindrical Li-ion cells into the multirotor’s airframe structure, thereby cost- effectively enhancing endurance. Through the proposed engineering design approach, a prototype UAV is built and tested, demonstrating a significant endurance improvement over similarly sized vehicles powered by LiPo batteries. This design presents a budget friendly solution that could enable small-scale farmers to take advantage of affordable UAV technology.Item Open Access Synergistic aerodynamic force assessment through an extended exergy approach(Cranfield University, 2023-06) Mutangara, Ngonidzashe E.; Laskaridis, Panagiotis; Sanders, Drewan S.Drag decomposition using energy and exergy-based methods has shown large utility for aerodynamic performance assessment through their flow-field decompositions into different physical mechanisms. A particularly significant advantage of these methods is their ability to identify recoverable energy, which describes the available energy imparted to the flow by the aircraft as it traverses through the fluid. This type of assessment is not possible with traditional momentum analysis. Thus, energy/exergy analysis uniquely evaluates the potential benefits of wake energy utilisation for thrust production through novel architectures such as boundary layer ingestion. The velocity decomposition approach has introduced notable improvements to this analysis framework. This allows for a phenomenological drag decomposition into reversible and irreversible components by splitting the velocity field into its isentropic and non-isentropic contributions within the flow. From this, the reversible drag originating from the bulk flow can be obtained through the isentropic field, whilst the non-isentropic field provides the irreversible dissipative drag arising from the boundary layer and wake zones. The work conducted in this thesis aims to improve the velocity decomposition approach by combining it with partial pressure field analysis, enabling the decomposition of pressure into Euler and dissipative parts, previously not achievable with velocity decomposition alone. Assessment in this manner improves the evaluation of recoverable energy by identifying the additional pressure work potential within the dissipative field. Additionally, the unification extends energy/exergy-based analysis principles to the near- field, providing a unique decomposition capable of evaluating the local accumulation of viscous drag through dissipative pressure and skin friction, whilst the induced drag is assessed from the non-dissipative pressure.Item Open Access A study of control mechanisms in micro and nano system-enhanced polymer nanocomposites under mechanical and electrical stimuli: an experimental and computational investigation(Cranfield University, 2023-11) Mishra, Raghvendra Kumar; Chianella, Iva; Yazdani Nezhad, Hamed; Goel, SauravNanocomposite materials, particularly those reinforced with graphene nanoplatelets (GNPs) and Barium Titanate (BaTiO₃), have been the focus of extensive study within diverse industries aiming to enhance mechanical and electrical properties. This thesis investigates the intricate relationship between external mechanical and electrical stimuli and the effectiveness of these reinforcing agents within nanocomposites, presenting significant findings and novel contributions, while addressing an unexplored aspect within the field. The research highlights a two-part exploration. The first part of the thesis details the creation of GNP/BaTiO₃ polymer nanocomposite fibrils via mechanical stimulation, specifically cold drawing, emphasising the compatibility of recycled polypropylene (PP)/polyethylene terephthalate (PET) blends. The resulting fibrils, exhibiting a significant aspect ratio disparity of 400:1, have demonstrated substantially improved electrical, thermomechanical, and electromagnetic properties. This in-situ mechanical stimulation (cold drawing) not only alters the morphology but also enhances electrical conductivity, limits polymer chain mobility, and reinforces the PP matrix, significantly improving its electrical, thermomechanical, and electromagnetic interference shielding. In the subsequent second part of the thesis, the study explored the integration of graphene-based materials and BaTiO₃ within epoxy composites. Computational modelling and statistical analysis have revealed the influence of these fillers on DC conductivity, dielectric properties, and thermal behaviour. In addition, a comprehensive examination of variations in filler thickness and volume percentage that seemed to significantly impact material’s behaviour has been investigated for the first time under electric fields. Specifically, the investigation into BaTiO₃ nanoparticles and Si-BaTiO3 in epoxy under electric fields has revealed the interplay between electrical stimuli, material properties, and mechanical behaviour, highlighting ferroelectric and piezoelectric effects observed in BaTiO₃ ceramics.i This comprehensive study not only contributes novel findings but also significantly fills a research gap within the field of nanocomposites by presenting an in-depth examination of mechanical and electrical responsiveness, a study that has not been previously undertaken in such a detailed and exhaustive manner. The research conducted, sheds light on the potential for advanced materials in diverse industrial applications and underscores the importance of material selection, offering a pioneering step towards potential industrial utilisation. Additionally, this research offers guidance for further computational exploration, particularly in selecting GNP and BaTiO₃ materials to enhance the electrical and thermal properties of the epoxy matrixItem Open Access Decentralized mission planning for multiple unmanned aerial vehicles(Cranfield University, 2023-02) Liu, Ruifan; Shin, Hyo-Sang; Tsourdos, AntoniosThe focus of this thesis is the mission planning challenge for multiple unmanned aerial vehicles (UAVs), with a particular emphasis on their stable operations in a stochastic and dynamic environment. Mission planning is a crucial module in automated multi-UAV systems, allowing for efficient resource allocation, conflict resolution, and reliable operation. However, the distributed nature of the system and physical and environmental constraints make it challenging to develop effective mission planning algorithms. The thesis begins with a review of the taxonomy, frameworks, and techniques in multiple-UAV mission planning. Following this, it identifies four critical research challenges, encompassing scalability, efficiency, adaptability and robustness, and energy management and renewable strategies. In response to these challenges, four objectives have been defined with the overall aim of developing a generic decentralized mission planning paradigm for multi-UAV systems. The thesis subsequently concentrates on accomplishing these objectives, with notable contributions in the development of 1) a decentralized task coordination algorithm, 2) an efficient route planner in consideration of recharging, and 3) an energy-aware planning framework. This research first proposes a decentralized auction-based coordination strategy for task-constrained multi-agent stochastic planning problems. Through casting the problem as task-constrained Markov decision processes (MDPs), the task dependency due to an exclusive constraint is despatched from Multi-agent Markov decision processes (M-MDPs) and then resolved by adopting an auction-based coordination method. For multi-agent stochastic planning problems, the suggested technique resolves the trade-off concern between computational tractability and solution quality. The proposed method ensures convergence, achieves at least 50% optimality under the assumption of a submodular reward function, and greatly reduces the computational complexity compared to multi-agent MDPs. Deep Auction is then proposed as an approximate modification of the suggested auction-based coordination method, where two neural network approximators are introduced to facilitate scaled-up implementations. By theoretical analysis, these two proposed algorithms achieve better robustness and feature less computing complexity compared to the state-of-the-art. Finally, a case study of drone delivery with time windows is implemented for validation. Simulation results demonstrate the theoretical benefits of the recommended methodologies. Then, an efficient route planner for individual UAVs accounting for recharging services is proposed. Despite extensive research in decision-making algorithms, existing models have limitations in accurately representing real-world scenarios in terms of UAV’s physical restrictions and stochastic operating environments. To address this, a drone delivery problem with recharging (DDP-R) is proposed. The problem is characterized by directional edges and stochastic edge costs affected by winds. To solve DDP-Rs, a novel edge-enhanced attention model (AM-E) is proposed and trained via the REINFOCE algorithm to map the optimal policy. AM-E consists of a series of edge-enhanced dot-product attention layers that capture the heterogeneous relationships between nodes in DDP-Rs by incorporating adjacent edge information. Simulation results show that the edge enhancement achieves better results with a simpler architecture and fewer trainable parameters, compared to other deep learning models. Extensive simulations demonstrate that the proposed DRL method outperforms state-of-the-art heuristics in solving the DDP-R problem, especially at large sizes, for both non-wind and windy scenarios. Finally, we integrate the above route planning algorithm into an online energy inference framework, namely, the Energy-aware Planning Framework (EaPF), with the aim of optimizing solution quality in consideration of possible time-window violation and battery depletion. The framework comprises a statistical energy predictive model, a risk assessment module, and a route optimizer, with functions of modelling energy costs, estimating risks, and optimizing the risk-sensitive objective. Concretely, a Mixture Density Network (MDN) is established for predicting the distribution of future energy consumption taking account of wind conditions. The MDN is trained by historical data and continuously updated as new data is collected. Then, a risk-sensitive criterion is formed based on the MDN model of energy consumption to assess the risk of task lateness and battery depletion. To minimize the risk-sensitive objective, the EaPF incorporates the proposed AM-E planner using a Model-based Multi-Sampling (MBMS) route construction strategy, to further improve solution quality and planning robustness. In the context of drone deliveries, simulations validate the effectiveness of the MDN energy model and the EaPF. Results show that the integration of EaPF achieves an average cost reduction of 25%, which implies a lower energy cost, a higher task accomplishment rate, and a smaller battery depletion risk compared to the stand-alone DRL planner.Item Open Access Enhancing mechanical properties of concrete material with fibres of different materials(Cranfield University, 2022-12) Khalel, Hamad; Khan, Muhammad Ali; Starr, AndrewFibre reinforced cementitious composites are highly effective for construction due to their enhanced concrete properties. Materials such as steel fibre have been used extensively to reinforce concrete because of their excellent mechanical properties. Academic researchers have comprehensively discussed the impact and challenges of fibre reinforcement to obtain optimal properties in the resultant concrete. Most researchers have reported the mechanical performance of fibre- reinforced concrete (FRC) under static loads. Concrete with fibre reinforcement is stronger and more ductile than concrete without reinforcement. Significant efforts have been made to demonstrate the properties and enhancements of concrete after reinforcing it with different types and shapes of fibres. However, the optimization in the reinforcement process is still unanswered. No academic study in the literature now available can pinpoint the ideal fibre type, quantity, shape, and, more crucially, the overall technical viability of the reinforcement. After performing the optimization, researchers considered how these optimizations could affect the crack resistance or properties under dynamic loads with different temperatures. However, a comprehensive analysis is still missing that can explain the crack resistance performance of FRC under dynamic loads at relatively high temperatures. The main aim of this thesis is to investigate the mechanical behaviour of concrete structures under thermo-mechanical dynamic loads about reinforcing fibres of different weight ratios. This study uses parametric analysis in accordance with extensive mechanical tests to identify the optimal shape, size, and percentage of fibres. The design variables for optimization are divided into input and output parameters. The input parameters are the influences of the type, length, and percentage of fibres on concrete performance, including samples of fresh and mechanical concrete properties, to search for the most effective relation of fibre dose and dimension to optimize the combined responses of workability, splitting tensile strength, flexural strength, and compressive strength. The current work also proposes the Khan Khalel model, which can predict the desirable compressive and flexural strengths for any given values of key fibre parameters. Statistical tools are used to develop and validate the model with numerical results. The proposed model is easy to use but predicts compressive and flexural strengths with errors under 6% and 15%, respectively. This error primarily represents the assumption made for the input of fibre material during model development. It is based on the elastic modulus of the material and hence neglects the plastic behaviour of the fibre. A possible modification in the model for considering the plastic behaviour of fibre will be considered as future work. Finally, this study analyses the efficacy of FRC beams for crack resistance under coupled loads, i.e., dynamic loads at relatively high temperatures. Cantilever FRC beams are tested on a modal exciter in a band heater to expose the beams to bending loads at different temperature values. The variation in the dynamic response parameters of the beam, including modal amplitude and frequency, is discussed and compared with experimental results for regular and reinforced concrete beams. The stress intensity factor and displacement amplitude characteristics show that the steel FRC specimens have excellent ductile behaviour and higher crack resistance than ordinary concrete samples.Item Open Access Vortex formation downstream of an active vane vortex generator(Cranfield University, 2022-07) Li, Dingyu; Garry, Kevin P.; Prince, SimonA blended wing body aircraft, with embedded engine intakes near the wing trailing edge, requires aerodynamic optimisation under flight conditions to ensure satisfactory aerodynamic performance. In such a configuration, the wing surface upstream of the intake is a critical region within which active boundary layer flow control could provide significant benefits. The static vortex generator has additional drag under cruise conditions, but the active vortex generator not have the same issue. If the active vortex generator (VG) were to be utilised, the transient behavior of the flow downstream of the VG following its activation would need to be understood. The active vortex generator concept adopted in the current study is a thin flat blade, inclined at a constant angle to the local flow direction, which can be deployed from its ‘stowed’ (fully retracted position), allowing it to project into the surface boundary layer and operate as a conventional blade vortex generator once fully extended. This study investigates the transient characteristics of the flow structure downstream of the blade during the deployment, using both up- scaled experimental and numerical simulations. The results contribute data to the development of an effective active flow control strategy, enhancing understanding of the flow control techniques. The experimental approach is designed to examine the fundamental characteristics of the transient behaviour and is split into two work-phases. In Phase I, the study is focused on exploring the feasibility of the experimental approach to generate the vortex-forming transient. Phase II involves the use of a scaled-up experiment for a detailed study of the transient flow structure at Reynolds numbers in the range 1500 to 3500, based on local velocities in the boundary layer and the heights of the blade. In the Phase II experiment, a multi-hole pressure probe is used to record the vortex formation and decay characteristics in a given downstream plane. The data show that the vortex development has a nonlinear response to the blade deflection during the blade deployment. This Phase II data is compared to both RANS CFD steady-state simulations and analytical predictions using empirical models under steady conditions. The supplementary study indicates that the vortex-forming process is dependent on the transient nature of the VG blade deployment and cannot be adequately represented by the steady analysis. A key outcome of this study relates to the practical application of vortex movement within the embedded boundary layer as a result of the VG blade deflection. The transient vortex position profile between the stowed (no vortex) and the deployed (steady-state or static vortex) location is very different from that predicted by steady-state modeling. The transient vortex vertical motion causes a smoother local circulation increase compared to the starting vortex, and the nonlinear circulation variations remain independent of blade size effects. Furthermore, the findings presented in this thesis offer insight into active flow control. With continued study, the active blade vortex generator can increase the aircraft's efficiency and performance.Item Open Access Swarm drones - efficient machine learning and informatics(Cranfield University, 2022-12) Li, Chen; Guo, Weisi; Tsourdos, AntoniosIn 2020, worldwide consumer drone unit shipment was 5 million, which is expected to be 9.6 million in 2030. This generates a global drone market with 26.3 billion USD in revenue. The popularity of drones in civilian and professional environments has changed the way humans live and work. However, they have also brought new challenges and threats to the environment and society (e.g., property and personal damage caused by inappropriate drone operations or hostile drones) which requires more robust regulatory mechanisms and advanced technologies of drones. Supervision of tiny shape, high-mobility drones by humans is inefficient and inaccurate, whereas Artificial Intelligence (AI) methods, especially deep learning (DL) show potential in drone detection, classification and tracking. However, as data-driven models, the performance of DL models is decided by the quality of data and model structure. At the same time, the structural complexity of black-box DL models affects their explainability and energy efficiency. These factors affect the willingness of people to trust DL models. Therefore, this thesis aims to analyze the impact of drone informatics on DL behaviour, and achieve more efficient training of high-trustworthiness DL models by efficient drone informatics. This will require research on DL explainability, trustworthiness and efficiency. The aforementioned researches are all interrelated and highly relevant to the data. In this thesis, firstly, explainable AI (XAI) and DL trust factors are reviewed. A theoretical DL trustworthiness metric Quality of Trust (QoT) and a lifelong AI trust- worthiness supervision protocol are proposed. Secondly, a novel partially explainable Gaussian-process-based neural network structure is proposed. Compared with conventional machine learning methods, it is more transparent and without any sacrifice in accuracy. Thirdly, a GAN-TDA method is proposed to analyze the learning efficiency of convolutional layers on drone images and guide the collection of new data. Collecting new data with direction could boost the DL model performance more efficiently in time and cost. Fourthly, a transistor operations (TOs) model is proposed to analyze the DL energy consumption scaling law to different model architectures and settings. Finally, a physical visual neural stealth drone canopy is designed with the hard-to-learn design features analyzed by GAN-TDA and painted with adversarial evasion features to escape DL drone detection and classification. The canopy design method is further extended to swarm drone scenarios. This thesis shows: 1) both model explainability and performance are related to DL trustworthiness, and need a trade-off according to the QoT of different tasks; 2) combining human-understandable efficient drone informatics and the understanding of DL energy scaling laws can find high-efficiency datasets and network structures, resulting in efficient DL models with high trustworthiness; 3) The above knowledge can be used to formulate attacks on drone-related DL models to reduce their trustworthiness.Item Open Access Thermodynamic and combustion characteristics of ultra-high performance engines for motorsport applications(Cranfield University, 2023-08) Le Roux de Bretagne, Olivier; Harrisson, Matthew F.; Temple, CliveUsing steady-state and transient one-dimensional gas dynamic engine models developed with AVL Boost™, critical assessment of the performance characteristics of the current 2014+ Formula One™ engine and of the future 2026 Formula One™ Power Unit are investigated. For the 2014+ regulations, a Digital Twin, aiming at replicating the trends of the real engine despite a lack of component-level-detail data, is created and used to scientifically explain how this engine achieves 50+% brake fuel conversion efficiency and to rank the contribution of each enabling technologies (high compression ratio, lean combustion, passive pre-chamber, direct injection, asymmetric valve profiles, MGU-H and waste gates used as pressure-relief valves). The impact of the 2026 Formula One™ Power Unit regulations on engine performance is investigated and highlights that the reduction in fuel flow will not only result in the obvious reduction in power output but also in in-cylinder pressure which introduces opportunities for enhanced combustion process and higher air/fuel ratios. Nevertheless, with the high MGU-K power, both the 2014+ and 2026 Power Units are predicted to have similar peak output power despite an advantage at low speed for the 2026 regulations thanks to the capacity of electric motor to produce torque at low speed. Using transient simulations, the impact of the removal of the MGU-H in the 2026 regulations is assessed and an anti-lag solution using the MGU-K called torque consuming is investigated. It is demonstrated that always operating the engine at full load during acceleration phases and using the MGU-K to absorb the excess power compared to the power demand / to control the amount of power delivered to the wheels helps to reduce turbo lag, improve engine efficiency, and reduce the need for the MGU-K to torque fill, but at the expense of a higher fuel consumption.Item Embargo Implications of military aircraft’s mission optimal performance on gas turbine engine life expectancy(Cranfield University, 2023-08) Lazarou, Georgios; Nikolaidis, Theoklis; Devaiah, NaliandaGas turbine engines have a crucial role in evaluating military aircraft performance. Operating in a range of missions and environmental conditions, they are subjected to an excessively demanding usage often reaching their operating limits. The impact prediction on engine components degradation of this adverse usage requires a multi-disciplinary approach to best capture its effects. This master thesis investigates the implications of optimal mission performance on the degradation of military gas turbine engines. The research focuses on the degradation of first stage of the high-pressure turbine caused by the failure mechanisms of creep, low cycle fatigue and high cycle fatigue, each acting independently on the turbine blades. By exploring the implications of mission performance on engine degradation, this study provides valuable insights for optimizing mission execution strategies and improving operational efficiency in military aviation. Through a comprehensive analysis, several key findings have been identified. It was observed that as the turbine entry temperature (TET) decreases, the stresses on the turbine blade have a disproportionately greater effect on the overall damage. This suggests that maintaining optimal TET levels is crucial for mitigating engine degradation, as an increase of 0.005% in blade temperature can lead to 40% more thrust, 100% more fuel consumption but can reduce life by 18% in Creep, 15% in LCF and 14% in HCF. In addition, the study reveals that the use of afterburner though having similar thermo-mechanical stresses upon the blades with the maximum dry setting, the extensive usage in a mission can significantly impact the life consumption. A mission with 40% less overall duration can present an up to 40% reduced life expectancy. Lastly, the investigation highlights the significant differences in life consumption during several optimal climb paths. A time optimized profile is found to be the most damage inflicting having 3 times less lifespan than noise and IR optimized paths. A life expectancy of only 80 flight hours is predicted for the usage applied on this profile resulting from the impact of low cycle fatigue contribution. This research contributes to the field of military-related costs by shedding light on the operational availability of gas turbine engines.Item Open Access Investigation of multiphase of multiphase flow instabilities and development of turbulence models for transient hydrodynamic slug flow in horizontal pipelines(Cranfield University, 2023-05) Kouadjo, Bobo Claude; Könözsy, László Z; Jenkins, Karl W.The knowledge of the slug flow is essential to the design and safety of hydrocarbon transportation in the pipelines systems of the petroleum industry. This thesis presents a theoretical and computational investigation of hydrodynamic slug flow in horizontal pipelines. As slug flow is part of multiphase flows, a literature review of multiphase models and their instabilities including the turbulent models involved. A focus on the anisotropic aspect of the prediction of turbulence has been considered by setting up a new turbulence model that will help us to solve this multiphase problem (hydrodynamic slug flow). A User-Defined Function based C code has been implemented to model the anisotropic turbulence for the new multiphase turbulence model created as a contribution to the knowledge. The Ansys Fluent computational fluid dynamics (CFD) software package has been used to set up the simulations with the aim of investigating the characteristics of slug flows such liquid holdup, pressure drops in different pipe sizes (diameter 16mm, 26mm and 50mm). The challenges including the three- dimensional simulations were carried out with both isotropic and anisotropic turbulent models to investigate the differences, similarities, and improvements. The isotropic simulations were validated with a journal paper (Deendarlianto et al., 2018). As a result, different flow patterns such as stratified Fig. (4-14.) and Fig. (4-15), pseudo slug Fig. (4-23.), slug Fig. (4-5) and Fig. (4-8) have been obtained. The analysis shows that at some time steps, numerical and experimental data values are very closed, showing a good validation. A comparative study has been performed to compare and assess the performance of isotropic and anisotropic simulations results for an industrially relevant engineering application. The validation shows a better result Fig. (4-43) compared to isotropic simulation.Item Open Access A holistic methodology for value-driven conceptualisation of passenger cabin interiors(Cranfield University, 2023-11) Kirenskis, Romans; Lawson, Craig; Jia, HuaminThe design of aircraft cabin interiors is a multi-disciplinary, multi-domain activity challenged by the need to satisfy technical, operational, and commercial product requirements simultaneously. Addressing these in isolation proves ineffective in delivering cabin interiors destined for long-term success in the modern market driven by holistic forces. However, no unified approaches exist for their integrated co-development. Engineering tools like Multi-Disciplinary Optimisation resolve the technical challenges, but are unable to integrate the commercial factors. Resource-efficient innovation is further perplexed by the competitive data-sharing practices and conflicting priorities pursued by the many cabin stakeholders. As a result, the parties involved in cabin interior design lack awareness of each other’s preferences, needs, and constraints. The integration of contrasting stakeholder priorities can be streamlined by conceiving a holistic methodology for early-stage cabin product design. It shall implement effective decision-making practices into a collaborative cabin design toolset to facilitate co-creation. This thesis proposes such a methodology, which was developed in a multi-step approach. First, the identification of a suitable design assessment basis is enabled by deriving a synoptic taxonomy of discrete Multi-Criteria Decision Analysis tools. It is then employed to map the diverse multitude of drivers relevant to cabin interior design and prioritise among them using context-based logic defined by the case being addressed. Industry expertise was gathered to consolidate multiple stakeholder preferences into a robust capability for the evaluation of potential interior design solutions. Finally, the holistic cabin design approach proposed is used to assess the sustainability of cabin interior products as the most pertinent issue faced by the industry at the moment. This is achieved in a cost-efficient manner at a scale unachievable with existing Life Cycle Assessment methods. The effectiveness of the toolset proposed is validated by its application to a hypothetical case study.Item Open Access Multidisciplinary preliminary design and integration of the transmission system in a pusher geared contra-rotating open rotor(Cranfield University, 2020-09) San Benito Pastor, Diana Guiomar; Nalianda, Devaiah; Sethi, VishalOne of the main challenges for the aviation industry is to reduce its global environmental footprint. Geared contra-rotating open rotors have the potential to further reduce fuel consumption relative to geared turbofans, but require a more- complex speed-reducing transmission system to drive the propellers. Hitherto, the preliminary design for such transmission systems has been reported independently of the overall engine modelling or has been limited by many pre- determined engine constraints. This has restricted the feasible design space of the engine and the transmission system. Therefore, this research addresses two key questions: Can the preliminary design of the transmission system be done from cycle parameters without imposing additional engine-based constraints? How does the introduction of more rigorous preliminary design processes for the transmission system affect the design space of the open rotor engine? The transmission system in the contra-rotating open rotor comprises two main components: a power gearbox and a pitch change mechanism. These technology enablers enhance engine performance by decoupling the operation of the propellers from the free power turbine and adjusting the pitch of the blades respectively. The best power gearbox option in a contra-rotating open rotor is a differential planetary gearbox, which enables contra-rotation of the output shafts and a high power transfer with a reduced size. The space envelope of the power gearbox varies with the torque ratio between its output shafts, connected to the propellers. The effect of torque ratio variation on gearbox design has been analysed in this research for equal propeller rotational speeds and different speed ratios between the output shafts. This research shows that potential torque ratios lie between 1.1 and 1.33, with the higher ratios enabling more compact gearboxes having four or five planet gears. However, for a prescribed propeller rotational speed, higher torque ratios would reduce the rotational speed of the low-pressure turbine driving the propellers and potentially reduce its efficiency. Alternatively, increasing propeller rotational speeds would result in thicker radial shafts for the pitch change mechanism connected to the propeller blades. The presence of these shafts radially traversing the engine’s gas path might contribute to the blockage of the exhaust duct. To address these issues, a preliminary design framework has been developed that combines 0D thermodynamic modelling with flow path sizing and weight estimation and enables assessing the integration effects of the transmission system on engine performance. The engine’s optimum performance design space might not be accessible due to mechanical constraints or integration interactions. Relative to a baseline design, the reduction in fuel burnt can be as high as 1% with current technology levels and 3% for future designs with entry into service by 2035. However, the potential performance gains derived from improvements in turbine design might not be achievable when the transmission system is integrated. The integration of the transmission system further reduces potential fuel burn gains to 0.6% relative to a baseline engine design. A wide range of activities for future work is opened by the methods developed in this research in both performance and mechanical development of the components in the transmission system.Item Open Access Sustainable sandwich composites for automotive applications(Cranfield University, 2022-10) Jiang, Qihong; Rahatekar, Sameer; Mills, AndrewThe increasing regulation and demand are raising the pressure on manufacturing automotive components towards lighter weight and more recyclability. The commercial road transport industry, contributing a giant part of emissions, is still significantly utilising wood panels as trucks’/ lorries’/ vans’/ buses’ floor or side walls (of boxes), which is cost-effective and used for a very long time. However, with the increasing pressure on lighter weight and more recyclability, the wood panels that could cause deforestation, become a bio- degradable landfill at the end of life and have a relatively high density are no longer the best-fit choice for the floor or side panels of such vehicles. The challenge is to have a floor panel design that could satisfy the increasing pressure and product requirements such as mechanical properties, price, and durability. This research aimed to complete such a challenge by designing sandwich composite structures with fibre-reinforced plastics and foam materials (foam is used in case thermal resistance is needed, and honeycomb materials could be applied when thermal insulating is unnecessary). A fully recyclable sandwich composite achieved using recycled carbon fibre, polypropylene, and recycled PET foam underwent various tests to evaluate its applicability as a commercial transport vehicle floor or side panel. Single fibre tensile tests were operated to understand the behaviour of the RCF mats. Composite mechanical properties were estimated from tensile and three-point bending results, and impact behaviour was analysed after drop tower impact testing. Fibre embedding and sandwich bonding were verified under SEM, and the resulting sandwich composite product properties were also tested using three-point bending. The novelty of such sandwich composite is using RCF with PP to achieve a fully recycled composite skin, while RCF were used mainly with thermoset resin (in the same ways as virgin carbon fibre fabrics). Also, thermoplastic materials such as PP were hard to process with fibre fabrics to form suitable composites due to their non-polar constitution and high viscosity. Fibre fabric would be squeezed together and create a layered structure with fibre rich zone at a very high fibre volume fraction, while the intermedia zone mostly has resins. However, when RCF and PP are mixed, the randomly oriented fibre could also hinder the load from the viscose melt and reduce the amount of fabric pressed closely, forcing some of the melt to pass through inter-fibre areas to create a better filling. Different forms of PP (sheet, powder) were used, and their effect on the compression moulding process and the final product were studied in this research. A faster-pressing cycle was achieved, and a lower pressing pressure was needed for the powder PP process, but disadvantages came from the emission and cost side.Item Open Access Green hydrogen revolution in aviation: requirements and possibilities(Cranfield University, 2023-05) Janjua, Shahzada Sulman; Nalianda, Devaiah; Pilidis, PericlesThis work investigates the case for sustainable aviation for the Asia Pacific region and focusses on Hong Kong. Hong Kong presently generates 50% of its energy from coal. The aim is to remove carbon from aviation fuels for Hong Kong and replace it with green hydrogen. This is a viable choice of sustainable aviation fuel but switching it from kerosene would require the overcoming of some challenges. This thesis comprises of three parts: firstly, the modelling and simulation of the Trent-XWB-97 jet engine as a baseline combusting Jet-A fuel. Its aircraft performance is then compared to a cryogenically fuelled green hydrogen engine. Secondly, the reference engine is then fitted with an intercooler with the gain of aircraft performance benefits in mind as well as to utilise it as a heat exchanger to vapourise the liquid hydrogen and thirdly, large-scale green hydrogen production using renewables is envisaged as part of a Green Hydrogen Hub network encompassing a green hydrogen logistical supply chain paving the way for a future aviation hydrogen micro-economy. It was discovered that relative to the Jet-A fuelled engine, the engine with a constant net thrust for ODP (Take-Off) and DP (Cruise) conditions decreased the ESFC for both baseline and intercooled engines. For the reference case at ODP this drop in ESFC was (1.71%) and (1.3%) for the intercooled scenario. There was also an accompanying decrease in TET; for the baseline engine this was 47K and for the intercooled engine this was 50K. The addition of the intercooler achieved the greater aircraft thrust requirement of 448kN and also vapourised the cryogenic hydrogen to high enough temperatures. These were calculated to be 536K and 296K for the ODP and DP respectively. The results showed that the baseline engine carried the greatest payload of 31866 kg with a block fuel burn of 36267 kg and a flight duration of 11.83 hours. The intercooled engine yielded a maximum carried payload of 27184 kg and the block fuel burn was 43349 kg and a flight time of 11.97 hours. The study also discovered that the 43.4 tonnes of green hydrogen can be generated in Hong Kong using wind and solar power and that its usage reduced the civil aviation carbon footprint of Hong Kong by 11.6%.Item Open Access The aeropolitical realities underpinning the formation of an asean single air market(Cranfield University, 2023-09) Jaharudin, Mohd Hariszuan Bin; Ellis, Darren; Pagliari, RomanoThis study investigated regional air transport liberalisation in Southeast Asia based on a mixed-methods approach which incorporated a pilot survey (n=10), an online expert survey (n=50) and in-depth interviews (n=15), while employing a strategic framework adapted for this study called the Aeropolitical Regional Integration Framework (ARIF). The Association of Southeast Asian Nations (ASEAN) has significantly promoted regional air transport liberalisation. This initiative is an integral part of the ASEAN Community project, designed to enhance connectivity and economic development that contribute to building a regional identity. However, despite initial progress, the regional open skies agreement known as the ASEAN single aviation market (ASAM) has not unfolded as anticipated, with existing literature suggesting that aeropolitical challenges are among the primary reasons for this. The hybrid thematic analysis of the data, incorporating both inductive and deductive approaches, has identified key aeropolitical barriers and opportunities from political economy, geopolitics, and geoeconomics dimensions. Additionally, the research identifies mechanisms ASEAN employs to mitigate these challenges and capitalise on the opportunities. Within this study, aeropolitics emerges from the dynamic interplay among diverse state entities, with a particular emphasis on power relations among smaller nations and superpowers, as well as non-state actors, including those beyond the aviation sector, across various levels — national, intraregional, and interregional — which collectively exert influence over the aviation market. Despite the strong influence of politics in the region, it also reveals a genuine desire within ASEAN for meaningful liberalisation of air markets. While ASEAN may not replicate the European-style single aviation market model, there is clear evidence that regional divisions and obstacles gradually diminish over time. The ASEAN Way is not inertia in disguise but rather progress in a different form, where ASEAN does not aim to establish a single regulatory institution but pursues advanced cooperation within its member states and regional partners.