PhD, EngD and MSc by research theses (SATM)

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https://dspace.lib.cranfield.ac.uk/handle/1826/8739

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Open Access
4DT generator and guidance system
(Cranfield University, 2015-10) Amaro Carmona, Manuel Angel; Jia, Huamin
This thesis describes a 4D Trajectories Generator and Guidance system. 4D trajectory is a concept that will improve the capacity, efficiency and safety of airspace. First a 4D trajectories synthetizer design is proposed. A flight plan composed by a set of waypoints, aircraft dynamics model and a set of limits and constraints are assembled into an optimal control problem. Optimal solution is found by making use of an optimal control solver which uses pseudo spectral parametrization together with a generic nonlinear programming solver. A 4D Trajectories generator is implemented as a stand-alone application and combined with a graphic user interface to give rise to 4D Trajectories Research Software (4DT RS) capable to generate, compare and test optimal trajectories. A basic Tracking & Guidance system with proportional navigation concept is developed. The system is implemented as a complementary module for the 4D trajectories research software. Simulation tests have been carried out to demonstrate the functionalities and capabilities of the 4DT RS software and guidance system. Tests cases are based on fuel and time optimization on a high-traffic commercial route. A standard departure procedure is optimized in order to reduce the noise perceived by village’s population situated near airport. The tracking & guidance module is tested with a commercial flight simulator for demonstrating the performance of the optimal trajectories generated by the 4DT RS software.
Open Access
A framework for sustainable construction project based on BIM environment
(Cranfield University, 2023-06) Alnahdi, Sultan Saleh; Al-Ashaab, Ahmed; Salonitis, Konstantinos
The global construction industry's significant resource consumption and environmental impact underscore the urgency of sustainability. This research emphasizes the intersection of sustainability and construction, focusing on ecological, economic, and social considerations. It highlights Building Information Modelling (BIM) as a key enabler of sustainability within the construction value chain. Construction, vital to economic and societal development, necessitates sustainability as a core project objective. Efficient resource utilization, compliance with evolving sustainability standards, and effective collaboration among stakeholders are crucial. However, communication challenges often impede shared understanding and data integration. BIM emerges as a digital solution, unifying project phases, facilitating collaboration, and informed decision-making. In response to the global sustainability mandate, construction projects worldwide are adopting more effective approaches. BIM plays a pivotal role in enhancing efficiency, performance, and productivity. This research addresses a gap by presenting a framework to assess how building materials impact energy consumption within the BIM environment. The research aims to develop a comprehensive framework for promoting sustainability in construction projects through BIM. This involves investigating sustainable practices, assessing BIM's role in sustainability, selecting optimal engineering calculations, and creating an integrated framework. The framework's effectiveness will be evaluated through a hypothetical case study. Key research questions include BIM's alignment with sustainability, expected improvements in addressing sustainability issues, and the value of sharing sustainability calculations within the construction value chain. The thesis comprises seven chapters, including a literature review on sustainability and BIM, a detailed research methodology, a hypothetical case study, analysis of conduction heat transfer calculations, the development of a sustainable construction framework, and discussions, conclusions, and future directions. This research seeks to empower the construction industry with a practical framework for embedding sustainability within the BIM environment, driving efficiency, environmental responsibility, and societal well-being.
Open Access
A framework to leverage human resources information system for business performance
(Cranfield University, 2023-04) Sofi, Fadi; Fan, Ip-Shing; McLaughlin, Patrick
Payroll is one of the earliest applications in the history of business information system. Despite the early start, Human Resources Information System (HRIS) is primarily perceived as an administration tool. Most business managers do not recognise the business potential of HRIS. This research is motivated to address this phenomenon by identifying key Information System (IS) factors and organisation characteristics and initiatives to enhance HRIS business potential. The study proposes that, with the appropriate skills and knowledge, Human Resource (HR) practitioners can effectively use HRIS data to contribute to greater business success. Similarly, through effective initiatives implemented by business line managers, HR practitioners would be more capable of unlocking the potential of HRIS. A qualitative approach is adopted in exploring the key IS success factors, assessing HR practitioners’ skills, and understanding the initiatives that line managers could implement. The field data of this study were collected from HR practitioners and business line managers who worked for large companies in the UK. The field study confirmed that HRIS has been mainly used in an administrative context, with limited business impact. The two reasons suggested are: 1) there are shortfalls in HR practitioners’ strategic, analytic, and business skills and knowledge; 2) deficiencies in the line managers’ initiatives to maintain a productive HR-line relationship, empower HR practitioners, and adopt business expectations regarding the HR role. The research proposes a HRIS implementation framework that includes key IS success factors, required characteristics and initiatives that help HR practitioners to use HRIS effectively and unlock their potential to contribute to business success. The framework was developed into a Readiness Assessment Checklist (RAC) tool and used successfully in the implementation planning of a HRIS project. The research successfully applied information systems adoption research theories to develop a new model that captures the characteristics of Human Resource Management business practice.
Open Access
A3 thinking approach to enhance a complaints handling process in the airline sector
(Cranfield University, 2019-07) Alshahrani, Bader Mohammed; Al-Ashaab, Ahmed; McLaughlin, Patrick
A prescription for the business success is a matter of concern for company management, researchers and policy makers. There is an ongoing debate regarding the key tools which can increase business efficiency. For example, one stream of research argued that focusing on short-term goals is enough to boost up business performance. On the other hand, another stream argued that companies should focus on long-term performance by emphasising the importance of continuous improvement to assure the delivery of business sustainability. From this point of view, researchers proposed that problem solving is the key for achieving continuous improvement. Problem solving approaches are essential for maintaining the customer service quality as high as possible given the fact that they (problem solving approaches) focus on preventing the reoccurrence of complaints from customers. However, researcher did not reach a consensus regarding the effectiveness of the ‘traditional’ approaches of problem solving (e.g. the 5 whys). As a result, this study develops an A3 Thinking approach for problem-solving in order to enhance the complaints handling process in the airline sector. This approach is validated by using case studies of Saudi Airlines. One of the main advantages of developing such an approach is that it enables the capture of subsequent provision of useful knowledge gained from each complaint, thus enabling the prevention of the reoccurrence of problems, and supporting decision- making. This study provided a valid evidence on the importance of handling customer complaints in different touchpoints during customer journey (pre-flight, on board and post-flight phases). This study found that breaking down customer journey to touchpoints help company management prevent the reoccurrence of customer complaints by increasing the efficiency of responding to customer complaints. The research contributes to the literature by providing a detailed explanation of the journey encountered by airline customers, and it contributes towards enhanced practitioner outcomes by developing a customised A3 Thinking approach for problem-solving in the airline sector based on a learning cycle.
Open Access
Accidents caused by hazardous materials released in an urban environment: a numerical and experimental approach.
(2019-04) Vasilopoulos, Konstantinos; Tsoutsanis, Panagiotis; Könözsy, László Z.
This research studies the transport and dispersion of hazardous materials after a fire accident in an urban setting and the unpredictable threats provoked for the population and the environment. A fire accident may result, inter alia, from industrial activity or during the transportation of hazardous materials, such as diesel, petrol or kerosene liquids. In the current research, mineral oil pool fire accidents are examined in order to define the toxic smoke zones at different urban scale geometries. Three different urban scale geometries are examined: a) an isolated building, b) a street canyon and c) a staggered array of urban blocks. The fluid flow, the hazardous dispersion and the safety limits are studied using the Computational Fluid Dynamics (CFD) techniques and wind tunnel experiments. The Computational simulations were conducted using the CFD solver of Fluent and the Fire Dynamic Simulator (FDS). Both Reynolds-average Navier-Stokes (RANS) modes and Large Eddy Simulations (LES) methods were applied. Wind tunnel experiments were conducted in order to better understand the flow around these geometries and evaluate them with LES models. The numerical models were validated with wind tunnel experiments and with additional experimental data selected from the bibliography. The numerical results defined the toxic smoke limits and allowed the creation of simplified risk maps. The latter can define the mitigation measures after a fire accident.
Open Access
Active magnetic bearing for ultra precision flexible electronics production system
(Cranfield University, 2015-12) Tantau, Mathias; Shore, Paul; Morantz, Paul
Roll-to-roll printing on continuous plastic films could enable the production of flexible electronics at high speed and low cost, but the granularity of feature sizes is limited by the system accuracy. Technologies such as gravure printing and nanoimprint lithography demand a level of rotary motion precision that cannot be achieved with rolling element bearings. Manufacturing tolerances of the rotating parts, thermal drift and process forces in combination with structural compliance add up to additional error motions. In this master by research an active magnetic bearing (AMB) solution is designed for a new, super-sized roll-to-roll flexible electronics production machine, which was so far based on hydrostatic bearings. The magnetic bearing could actively compensate the accumulated synchronous error and maintain high accuracy under all conditions. However, the asynchronous error of a conventional AMB with the required size and power is a problem. In order to reduce the relatively high positioning uncertainty of active magnetic bearings an innovative radial position measurement based on linear, incremental encoders with optical conversion principle is proposed. A commercial encoder scanning head faces a round scale with concentric, coplanar lines on its face. By counting these lines the radial position can be measured. Because such a scale is not readily available, it is made by micro-machining. In experiments, different machining methods are compared. Then a magnetic bearing is built to demonstrate the efficacy of the proposed sensor. As a result, the best measurement noise is 3.5nm at 10kHz and a position uncertainty of approximately 0.25µm has been achieved for the magnetic bearing. These promising results are especially interesting for applications with high precision requirements at low speed of rotation.
Open Access
Adaptive intelligent traffic control systems in smart city
(Cranfield University, 2023-05) Ahmed, Aminag Hardwan B.; Al-Rubaye, Saba; Panagiotakopoulos, Dimitrios
Traffic congestion in urban areas presents a significant challenge with far-reaching impacts on the economy, environment, and overall quality of life. To address this challenge, this thesis proposes a novel approach to traffic signal control aimed at alleviating traffic congestion more effectively. The research problem this study explores is the design and implementation of an adaptive system for traffic signal control in urban road networks, specifically focused on how to effectively manage traffic signal timings to mitigate congestion. The major contributions of this study include the development of a unique coordination algorithm for adaptive traffic signal control, utilizing Multi- Agent Reinforcement Learning (MARL) and Ant Colony Optimization (ACO). This algorithm's uniqueness is reflected in its capacity to simulate the behavior of ant colonies to guide multiple agents in managing traffic signals at various intersections, enabling them to learn from their environment and interactions to optimize signal timings By simulating the behavior of ant colonies, the algorithm guides multiple agents in managing traffic signals at various network intersections, learning from their interactions with the environment and each other to optimize signal timings. This research sets out to address the challenge of traffic congestion in urban areas. With cities worldwide struggling with this issue, the task of managing traffic signal timings to reduce congestion is paramount. The problem formulation involved the exploration of how novel Machine Learning (ML) techniques, such as Multi-Agent Reinforcement Learning (MARL) and Ant Colony Optimization (ACO), could be utilized to develop an adaptive coordination algorithm for traffic signal control. These techniques were chosen due to their potential for learning and adapting over time to optimize signal timings based on ever-changing traffic conditions. The novelty of this research lies in the unique combination of MARL, Actor-Critic (AC), and ACO techniques to develop an adaptive coordination algorithm for traffic signal control. By integrating these techniques, we've created a system where multiple agents can independently control traffic signals at different intersections, learning from their surroundings and interactions to continually improve signal timings. This innovative use of ML, especially MARL and ACO, represents a significant contribution to the field of traffic management, as it offers the potential to adapt to changing traffic patterns and conditions in real-time. This adaptability is expected to lead to more efficient traffic flow and decreased congestion, outcomes not fully realized by existing fixed-time and traditional adaptive signal control methods.
Open Access
Adhesive joint geometry variation in non-rigid aircraft structures
(Cranfield University, 2019-11) Coladas Mato, Pablo; Webb, Phil; Xu, Yigeng
Adhesive bonding is a proven alternative to mechanical fasteners for structural assembly, offering lighter and thus more fuel efficient aircraft and cost-effective manufacturing processes. The effective application of bonded structural assemblies is however limited by the tight fit-up requirement, which is with tolerance ranges of hundreds of microns; this can be a challenge for the industry to meet considering the variability of current part manufacturing methods and the conservative nature of the conventional tolerance stack-up analysis method. Such a (perceived) limitation can discourage effective exploitation of bonding technologies, or lead to development of overengineered solutions for assurance. This work addresses such challenge by presenting an enhanced bondline thickness variation analysis accounting for part deflection of a bonded skinstringer assembly representing a typical non-rigid airframe structure. A semianalytical model accounting for unilateral contact and simplified 1D adhesive flow has been developed to predict bondline thickness variation of the assembly given the adherends’ mechanical properties, adhesive rheological properties, and external assembly forces or boundary conditions. A spectral-analysis method for assembly force requirement estimation has also been tested. The bondline dimensions of several representative test articles have been interrogated, including a reconfigurable test assembly designed specifically to test the input conditions that affect bondline geometry variation. It has been demonstrated that the part deflections need to be accounted for regarding the fit-up requirement of bonded non-rigid structural assembly. The semi-analytical model has been found to more reliable and realistic prediction of bondline thickness when compared to a rigid tolerance stack-up. The analysis method presented can be a major technology enabler for faster, more economical development of the aircraft of the future, as well as of any analogue structures with high aspect ratios where weight savings and fatigue performance may be core objectives.
Open Access
Adoption of product service systems in health care.
(2017-10) Mittermeyer, Stephan Alexander; Tomiyama, Tetsuo; Tiwari, Ashutosh
Health care systems are constantly challenged to deliver better quality of care at lower cost. Product Services Systems (PSS) aim to output a higher value to a customer, while reducing resource input required to achieve such value and sustainability. In the health care market this could help companies increase their focus on value for the patient, but also for the health care system as such. This focus on value can ultimately help drive down health care cost, which is one of the most pressing issues in health care systems today. The potential of PSS to address some of the major challenges in the health care market was recognised early in PSS research, however adoption in this field is still below expectation. Motivated by the potential of PSS in health care this work aims to explore the current status of adoption as well as drivers and barriers to future adoption in this market and evaluates if and how PSS can be designed and implemented by companies active in this market. This work showed that PSS can be feasible and useful in this sector as they address relevant current challenges. Future changes in the health care market will likely make PSS even more relevant. Certain concepts of PSS are already applied in the market without leveraging the benefits of a fully developed PSS. Limitations in how the value for patients and other market actors is determined and made transparent is a major challenge in the adoption of PSS. An assessment method is proposed to enable companies to evaluate the value generation of their PSS offerings. In addition, a guideline for PSS design is proposed based on results of this work and field observations. This thesis contributes to a better understanding of PSS adoption in health care by investigating mechanisms in the health care market to understand if PSS can be implemented in a useful manner and how PSS can be adopted in health care in the future. As PSS consists of a number of separate concepts that may be used by themselves and also outside a PSS concept, a detailed analysis was performed to evaluate how PSS concepts are already utilized by industry, as such partial implementations may be a good starting point for full PSS adoption. Adoption of a PSS in any industry requires a measure to evaluate the success of a system implementation or the quality of PSS offerings. Given the complex market network in health care, metrics for evaluations have been identified, linking different dimensions of clinical utility to PSS. Those metrics enable companies to assess PSS systems or scenarios, but also enable development teams to focus their PSS design efforts, as those assessment metrics provide a framework for PSS requirements engineering in this market. Based on the results of the work outlined above, design guidelines were defined to support the development process of PSS in health care.
Open Access
Advanced carbon/flax/epoxy composite material for vehicle applications: vibration testing, finite elements modelling, mechanical and damping characterization.
(Cranfield University, 2015-05) Ampatzidis, Theofanis; Blackburn, Kim; Abhyankar, Hrushikesh
Nowadays, research in automotive and construction industries focuses on materials that offer low density along with superior dynamic and static performance. This goal has led to increasing use of composites in general, and carbon fibre (CF) composites in particular. CF composites have been adopted widely in the space industry and motorsports. However, their high stiffness and low density leads to low damping performance, which is responsible for increased levels of noise and reduction in service life. On the other hand, natural fibres (NF) like flax fibres (FF) are capable of delivering a much better damping performance. A hybrid composite comprising of FF and CF can potentially deliver both on strength and higher damping performance. In this study the mechanical and damping properties of CF, FF and their hybrid composites were examined. Composites' anisotropic nature affects their response to vibrations and so traditional damping experimental setups used for metals had to be ruled out. A damping set up based on Centre Impedance Method (CIM) was adopted for the purpose of this study which was based on an ISO standard originally developed for glass laminates. Standard tensile and flexural tests were conducted in order to characterise the performance of the hybrid composite. The experimental work was accompanied by finite elements analysis (FEA). The experimental data and FEA were used to optimize the hybrid structure layup with respect to damping and structural response.
Open Access
Advanced flow technologies for the controlled & continuous manufacture of nanoscale materials
(Cranfield University, 2019) Isaev, Svetlin; Makatsoris, Charalampos (Harris)
Batch processes have been successfully used in the process industry over two centuries. However, changing customer demands and discovery of novel products have led the scientists and engineers to develop new manufacturing methods for the process industry. High-value products such as nanomaterials, smart and functional materials require precise process control for the entire product. Controlling of particle size and shape becomes more difficult in the large scale batch processes. Therefore, over the past few decades, there has been an increasing interest in the flow processing techniques due to their inherent benefits, such as better heat and mass transfer and small control volumes. Continuous Oscillatory Baffled Reactor (COBR) is a novel type of flow reactor. COBR combines oscillatory motion and periodically placed baffled flow channels to generate plug flow conditions, providing better mixing control similar to microreactors. Plug flow conditions can be achieved with the combination of optimum net flow, oscillatory amplitude and frequency using COBRs. With this new reactor and mixing concept, high-value products can be manufactured more efficiently using uniform mixing conditions and better temperature control. This will decrease the reaction time and production cost of novel products, use less energy, and increase time-to-market of novel products. The aim of this research is to develop a scalable and continuous manufacturing platform using continuous oscillatory baffled reactors to produce high-value products in low cost. The focus of this study includes developing modular oscillatory baffled reactors, characterisation of modular oscillatory baffled reactors using experimental methods, developing scale-up methodology from laboratory scale to industrial production size and demonstration of nanomaterial synthesis using modular oscillatory flow reactor...[cont.]
Open Access
Advanced numerical methods for dissipative and non-dissipative relativistic hydrodynamics
(Cranfield University, 2020-05) Townsend, Jamie F.; Könözsy, László Z. ; Jenkins, Karl W.
High-energy physical phenomena such as astrophysical events and heavy-ion collisions contain a hydrodynamic aspect in which a branch of fluid dynamics called relativistic hydrodynamics (RHD) is required for its mathematical description. The resulting equations must be, more often than not, solved numerically for scientists to ascertain useful information regarding the fluid system in question. This thesis describes and presents a twodimensional computational fluid dynamics (CFD) solver for dissipative and non-dissipative relativistic hydrodynamics, i.e. in the presence and absence of physically resolved viscosity and heat conduction. The solver is based on a finite volume, Godunov-type, HighResolution Shock-Capturing (HRSC) framework, containing a plethora of numerical implementations such as high-order Weighted-Essentially Non-Oscillatory (WENO) spatial reconstruction, approximate Riemann solvers and a third-order Total Variation Diminishing (TVD) Runge–Kutta method. The base numerical solver for the solution of non-dissipative RHD is extensively tested using a series of one-dimensional test cases, namely, a smooth flow problem and shock-tube configurations as well as the two-dimensional vortex sheet and Riemann problem test cases. For the case of non-dissipative relativistic hydrodynamics the relativistic CFD solver is found to perform well in terms of the orders of accuracy achieved and its ability to resolve shock wave patterns. Numerical pathologies have been identified when the relativistic HLLC Riemann solver is used in multi-dimensions for problems exhibiting strong shock waves. This is attributed to the so-called Carbuncle problem which is shown to occur because of pressure differencing within the process of restoring the missing contact discontinuity of its predecessor, the HLL Riemann solver. To avoid this numerical pathology and improve the robustness of numerical solutions that make use of the HLLC Riemann solver, the development of a rotated-hybrid Riemann solver arising from the hybridisation of the HLL and HLLC (or Rusanov and HLLC) approximate Riemann solvers is presented. A standalone application of the HLLC Riemann solver can produce spurious numerical artefacts when it is employed in conjunction with Godunov-type high-order methods in the presence of discontinuities. It has been found that a rotated-hybrid Riemann solver with the proposed HLL/HLLC (Rusanov/HLLC) scheme could overcome the difficulty of the spurious numerical artefacts and presents a robust solution for the Carbuncle problem. The proposed rotated-hybrid Riemann solver provides sufficient numerical dissipation to capture the behaviour of strong shock waves for relativistic hydrodynamics. Therefore, focus is placed on two benchmark test cases (odd-even decoupling and double-Mach reflection problems) and the investigation of two astrophysical phenomena, the relativistic Richtmyer– Meshkov instability and the propagation of a relativistic jet. In all presented test cases, the Carbuncle problem is shown to be eliminated by employing the proposed rotated-hybrid Riemann solver. This strategy is problem-independent, straightforward to implement and provides a consistent robust numerical solution when combined with Godunov-type highorder schemes for relativistic hydrodynamics...[cont.]
Open Access
Advanced state of charge estimation for lithium-sulfur batteries.
(2017-05) Propp, Karsten; Auger, Daniel J.
Lithium-sulfur (Li-S) batteries have a high theoretical energy density, which could outperform classic Li-ion technology in weight, manufacturing costs, safety and environmental impact. The aim of this study is to extend the research around Li-S through practical applications, specifically to develop a Li-S battery state of charge (SoC) estimation in the environment of electrical vehicles. This thesis is written in paper based form and is organised into three main areas. Part I introduces general topic of vehicle electrification, the framework of the research project REVB, mechanisms of Li-S cells and techniques for SoC estimation. The major scientific contribution is given in Part II within three studies in paper-based form. In Paper 1, a simple and fast running equivalent circuit network discharge model for Li-S cells over different temperature levels is presented. Paper 2 uses the model as an observer for Kalman filter (KF) based SoC estimation, employing and comparing the extended Kalman filter, the unscented Kalman filter and the Particle filter. Generally, a robust Li-S cell SoC estimator could be realized for realistic scenarios. To improve the robustness of the SoC estimation with different current densities, in Paper 3 a fast running online parameter identification method is applied, which could be used to improve the battery model as well as the SoC estimation precision. In Part III, the results are discussed and future directions are given to improve the SoC estimation accuracy for a wider range of applications and conditions. The final conclusion of this work is that a robust Li-S cell SoC estimation can be achieved with Kalman filter types of algorithms. Amongst the approaches of this study, the online parameter identification approach could deliver the best results and also contains most potential for further improvement.
Open Access
Advanced uncertainty quantification with dynamic prediction techniques under limited data for industrial maintenance applications.
(Cranfield University, 2021-07) Grenyer, Alex; Erkoyuncu, John Ahmet; Zhao, Yifan
Engineering systems are expected to function effectively whilst maintaining reliability in service. These systems consist of various equipment units, many of which are maintained on a corrective or time-based basis. Challenges to plan maintenance accounting for turnaround times, equipment availability and resulting costs manifest varying degrees of uncertainty stemming from multiple quantitative and qualitative (compound) sources throughout the in-service life. Under or over-estimating this uncertainty can lead to increased failure rates or, more often, unnecessary maintenance being carried out. As well as the quality availability of data, uncertainty is driven by the influence of expert experience or assumptions and environmental operating conditions. Accommodating for uncertainty requires the determination of key contributors, their influence on interconnected units and how this might change over time. This research aims to develop a modelling approach to quantify, aggregate and forecast uncertainty given by a combination of historic equipment data and heuristic estimates for in-service engineering systems. Research gaps and challenges are identified through a systematic literature review and supported by a series of surveys and interviews with industrial practitioners. These are addressed by the development of two frameworks: (1) quantify and aggregate compound uncertainty, and (2) predict uncertainty under limited data. The two frameworks are brought together to produce the Multistep Compound Dynamic Uncertainty Quantification (MCDUQ) app, developed in MATLAB. Results demonstrate effective measurement of compound uncertainties and their impact on system reliability, along with robust predictions under limited data with an immersive visualisation of dynamic uncertainty. The embedded frameworks are each validated through implementation in two case studies. The app is verified with industrial experts through a series of interviews and virtual demonstrations.
Open Access
Aero-propulsive performance assessment approach to boundary layer ingestion aircraft
(Cranfield University, 2023-04) Moirou, Nicolas G. M.; Laskaridis, Panagiotis; Sanders, Drewan S.
A promising solution towards more sustainable and efficient aircraft propulsion relies upon the ingestion of the boundary layer flow that develops around the airframe. Amongst the plethora of concepts, the propulsive fuselage concept appears to be the most pragmatic configuration, as a direct adoption of conventional tube-and-wing aircraft, which has an additional propulsor integrated around its tail. Nonetheless, there is a lack of consensus in the quantification and interpretation of the performance of such vehicles. Long-established momentum-based bookkeeping schemes break down as their underlying assumptions do not hold true in highly-integrated airframe-propulsion systems. Alternative approaches have been brought forth by considering holistically the aircraft to evaluate its performance and decompose its aerodynamic forces. Notably, energy- and exergy-based approaches improve one’s understanding on the cause and effect of boundary layer ingestion mechanisms but require high computational demands with dense grids. In sought of a universal approach, energy- and momentum-based methods are used together in this work to quantify the coupled aerodynamic performance of boundary layer ingestion aircraft. The strengths of near-field momentum integrations are coupled with more informative energy-based flow assessments. The design space of a propulsive fuselage aircraft is explored via CFD after a reduction of its modelling to an axi-symmetric partial assembly of the fuselage and propulsor. With variations in the thruster position along the tail, its flow passage through the fan and pressure rise, and exhaust design, best performance is achieved with a concept where the propulsor lies at 90% of the fuselage chord, for a fan hub radius of 30% of the fuselage radius, that ingests around 43% of the boundary layer mass-flow, and applies a pressure rise of 1.29, to generate around a third of the total propulsive force requirement whilst savings 11% of fuel relative to a short-to-medium range aircraft propelled by state-of-the-art turbofans. The reasons for such savings are detailed with a first-of-its-kind fully energetic flow decomposition which aims at attributing boundary layer ingestion benefits to changes in propulsor design.
Open Access
Aeroacoustic simulation of rotorcraft propulsion systems.
(Cranfield University, 2019-11) Vouros, Stavros; Pachidis, Vassilios
Rotorcraft constitute air vehicles with unique capabilities, including vertical take- off and landing, hover and forward/backward/lateral flight. The efficiency of rotorcraft operations is expected to improve rapidly, due to the incorporation of novel technologies into current designs. Moreover, enhanced or even new capabilities are anticipated after the introduction of advanced fast rotorcraft configurations into the future fleet. The forecast growth in rotorcraft operations is essentially associated with an expected increase in adverse environmental impact. With respect to the forthcoming rotorcraft aviation advancements, regulatory and advisory bodies, as well as communities, have focused their attention on reducing pollutant emissions and acoustic impact of rotorcraft activity. Consequently, robust and computationally efficient noise modelling approaches are deemed as prerequisites towards quantifying the acoustic impact of present and future rotorcraft activity. Ultimately, these approaches need to cater for unique operational conditions encompassed by modern rotorcraft across designated flight procedures. Additionally, individual variations of key design variables need to be resolved, in the context of design or operational optimisation, targeted at noise mitigation. This work elaborates on the development and application of a robust and computationally efficient methodology for the aeroacoustic simulation of rotorcraft propulsion systems. A series of fundamental modelling methods is developed for the prediction of helicopter rotor noise at fully-integrated operational level. An extensive validation is carried out against existing experimental data with respect to prediction of challenging aeroacoustic phenomena arising from complex aerodynamic interactions. The robustness of the deployed method is confirmed through a cost-effective uncertainty analysis method focused on aerodynamic sources of uncertainty. A set of generalised modelling guidelines is devised for the case of not available input parameters to calibrate the aerodynamic models. The aspect of multi-disciplinary optimisation of rotorcraft at aircraft level in terms of maximising the potential benefits of novel technologies is also tackled within this work. A holistic schedule of optimal active rotor morphing control is derived, offering simultaneous mitigation of pollutant emissions and acoustic impact across a wide range of the helicopter flight envelope. Finally, the developed noise prediction method is incorporated into an operational-level optimisation algorithm, demonstrating the potential of active rotor morphing with respect to reduction of ground-noise impact. The contribution to knowledge arising from the successful completion of this work comprises both the development of methodologies for helicopter aeroacoustic analysis and the derivation of guidelines and best practices for morphing rotor control. Specifically, a generic operational-level simulation approach is developed which effectively advances the state-of-the-art in mission noise prediction. New insight is provided with respect to the impact of wake aerodynamic modelling uncertainty on the robustness of noise predictions. Moreover, the aeroacoustic aspects of a novel morphing rotor concept are explored and quantifications with respect to the trade-off between environmental and noise disciplines are offered. Finally, a generalised set of optimal rotor control guidelines is derived towards achieving the challenging environmental goals set for a sustainable future rotorcraft aviation.
Open Access
Aerodynamic analysis and experiment of a micro flapping wing rotor
(Cranfield University, 2015-03) Li, Hao; Guo, Shijun J.
This project is aimed at developing a bio-inspired flyable micro/nano aerial vehicle (MAV) of high agility and performance capable of vertical take-off and landing and hovering (VTOLH). To achieve the aim, a novel flapping wing rotor (FWR) concept invented by Dr. Guo has been adopted, which is ideal for MAVs of sub 60 gm and especially for nano scale of sub 5 gm according to aerospace industry’s definition. The advantages and potential of the FWR concept for MAV development has been studied consistently by Dr. Guo’s research team in the last five years. However making a flyable micro FWR model especially in sub 5gm and demonstrate its VTOLH feasibility remains as a big challenge and has not been achieved in previous projects. To meet the above objective, the first achievement in the project is the successful design, build and test of a flyable micro FWR model (FWR-EX1) of only 3 gm based on off-the-shelf available micro motor. The key breakthrough is to achieve the necessary large aeroelastic twist of the flapping wing during the upstroke in an adaptive manner for structural and aerodynamic efficiency. To achieve the next objective for design and performance improvement, study has also been focused on deeper scientific understanding and analysis of the FWR mechanisms. Attention has therefore been paid to a systematic study on aerodynamic modelling and efficiency of the FWR. The method is based on a revised quasi-steady aerodynamic model that combines the theoretical method and experimental data. The numerical results of the revised quasi-steady aerodynamic model are in agreement with existing results obtained via CFD methods. Based on the model and analysis, the optimal kinematics for the FWR has been determined. Subsequently a comparison of the FWR aerodynamic efficiency was made with two other most studied configurations of MAVs, the insect flapping wing and rotorcraft ... [cont.].
Open Access
Aerodynamic analysis of large wind farms using two-scale coupled modelling approaches.
(2021-08) Ma, Lun; Tsoutsanis, Panagiotis; Antoniadis, Antonios
The effects of turbine aerodynamics and response characteristics of the atmospheric boundary layer on the overall wind farm efficiency are investigated in this research. Various wind farm modelling strategies, which include a theoretical and several CFD models, are presented. This study consists of three main parts: (i) improve and validate an existing theoretical wind farm model, (ii) infinitely large wind farm modelling with actuator-disc and fully-resolved turbine models, and (iii) finite-size wind farm modelling with a numerical weather prediction model. In the first part, an extended theoretical model based on a two-scale coupled momentum balance method is proposed to estimate aerodynamic effects of wind turbine towers on the performance of large wind farms. The modified theoretical model predicts that the optimal turbine spacing should increase with the value of normalised support-structure drag, as well as additional parameters describing the response characteristics of the atmospheric boundary layer to the total farm drag. The Detached-Eddy simulations of a periodic array of fully staggered actuator discs (AD) show a reasonably good agreement (within 10% in the prediction of power) with the modified theoretical model. In the second part, a fully resolved (FR) NREL 5MW turbine model is employed in two URANS simulations (with and without the turbine tower) of a fully developed wind farm boundary layer. The FR-URANS results show stronger tower effects than both AD-RANS and theoretical model predictions, which is a strong indication of the necessity of considering turbine support structure within large wind farm models. The possibility of performing DDES is also investigated with the same FR turbine model and periodic domain setup. The results show complex turbulent flow characteristics within a large wind farm, where typical hairpin and hub vortices have been clearly captured. In addition, the computational cost of DDES has been found to be similar to URANS (for a given number of rotations), which is a positive sign for conducting DDES in future studies. In the third part, a numerical weather prediction model is used as a realistic farm-scale flow model to investigate how the streamwise pressure gradient, Coriolis force and acceleration/deceleration terms in the farm-scale momentum balance equation tend to change in time. The results suggest that the streamwise pressure gradient may be enhanced substantially by the resistance caused by the wind farm, whereas its influence on the other two terms appears to be relatively minor. These results suggest the importance of modelling the farm-induced pressure gradient accurately for various weather conditions in future studies of large wind farms
Open Access
Aerodynamic and cost modelling for aircraft in a multi-disciplinary design context.
(Cranfield University, 2015-12) Di Pasquale, Davide; Savill, Mark A.; Kipouros, Timoleon; Holden, Carren
A challenge for the scientific community is to adapt to and exploit the trend towards greater multidisciplinary focus in research and technology. This work is concerned with multi-disciplinary design for whole aircraft configuration, including aero performance and financial considerations jointly for an aircraft program. A Multi-Disciplinary (MD) approach is required to increase the robustness of the preliminary design data and to realise the overall aircraft performance objectives within the required timescales. A pre-requisite for such an approach is the existence of efficient and fully integrated processes. For this purpose an automatic aero high-speed analysis framework has been developed and integrated using a commercial integration/building environment. Starting from the geometry input, it automatically generates aero data for loads in a timescale consistent with level requirement, which can afterwards be integrated into the overall multi-disciplinary process. A 3D Aero-solution chain has been implemented as a high-speed aerodynamic evaluation capability, and although there is not yet a complementary fully automated Aerodynamic design process, two integrated systems to perform multi-objective optimisation have been developed using different optimisation approaches. In addition to achieving good aircraft performance, reducing cost may be essential for manufacturer survival in today's competitive market. There is thus a strong need to understand the cost associated with different competing concepts and this could be addressed by incorporating cost estimation in the design process along with other analyses to achieve economic and efficient aircraft. For this reason a pre-existing cost model has been examined, tested, improved, and new features added. Afterwards, the cost suite has been integrated using an integration framework and automatically linked with external domains, providing a capability to take input from other domain tool sets. In this way the cost model could be implemented in a multi-disciplinary process allowing a trade-off between weight, aero performance and cost. Additionally, studies have been performed that link aerodynamic characteristics with cost figures and reinforce the importance of considering aerodynamic, structural and cost disciplines simultaneously. The proposed work therefore offers a strong basis for further development. The modularity of the aero optimisation framework already allows the application of such techniques to real engineering test cases, and, in future, could be combined with the 3D aero solution chain developed. In order to further reduce design wall-clock time the present multi- level parallelisation could also be deployed within a more rapid multi-fidelity approach. Finally the 3D aero-solution chain could be improved by directly incorporating a module to generate aero data for performance, and linking this to the cost suite informed by the same geometrical variables.
Open Access
The aerodynamics of aero-engine Nacalles.
(2018-02) Robinson, Matthew H.; MacManus, David G.
This thesis deals with the aerodynamics of aero-engine nacelles with a focus on the influence of a short and slim nacelle design on the drag performance. As turbofan engines are designed with increasingly reduced specific thrusts in order to improve propulsive efficiency, the fan diameter tends to grow. With a larger fan, the engine weight and nacelle drag grow which may offset the benefit from the reduced specific thrust. It is imperative to determine if a reduced length and thickness nacelle, compared to a conventional design, will enable the viable use of these reduced specific thrust aero-engine designs. The research aims to answer this question with a focus on cruise drag, spillage drag, drag rise and windmill performance of isolated and installed short, and slim nacelles. An innovative optimisation process was developed with a computational fluid dynamics process included as a means to evaluate nacelle drag. This was applied to different nacelle designs in a novel design space to optimise for cruise and off-design performance with a multi-objective genetic algorithm. The optimisation routine was extensively tested and verified against a number of analytical functions to ensure it could adequately approximate optimal Pareto sets. The optimisation of both axisymmetric and non-axisymmetric nacelles was carried out on drag, spillage and drag rise Mach number as well as on two metrics which control the pressure distribution of the nacelle. Optimal nacelles were then chosen to study the influence of nacelle incidence, the windmill condition and installation onto an aircraft on the drag performance and to provide a new quantification of these impacts. The optimisation demonstrated that under cruise conditions it is possible to have compact nacelle designs that offer reductions in drag. For example, a nacelle with a 23% reduction in length resulted in a 22% reduction in nacelle drag. However, these compact designs are more sensitive to off design condition. Specifically the spillage drag at a required drag rise Mach number of 0.87 could be 9 times higher for the reduced length nacelle. Nonetheless, it is possible to create a nacelle at the shortest length tested which had spillage of less than 6% of the cruise drag and met all requirements on drag rise to cruise at a Mach number of 0.85. This was enabled by an increase in the trailing edge radius such that it was equal to the highlight radius which improved the wave drag characteristics. Whilst the shortened nacelle was viable at low incidence, the increased wave drag resulted in the drag benefit relative to the conventional design being negated by an incidence of 6 degrees. In addition, this reduced length nacelle experienced separation at the end of runway windmill condition at 22 degrees, which is below the requirement of 30 degrees. Once installed on an aircraft the impact of reducing the nacelle length was a decrease in overall cruise aircraft drag of 3%. These studies demonstrate that there is a significant cruise benefit available from a short nacelle but that the off design conditions, most notably windmill requirements, will need to be addressed.