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Browsing School of Aerospace, Transport and Manufacturing (SATM) by Course name "PhD in Aerospace"
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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 A set-based design space exploration framework for hybrid-electric aicraft design(Cranfield University, 2023-08) Spinelli, Andrea; Kipouros, Timoleon; Laskaridis, PanagiotisEngineering design is characterised by uncertainty caused by a lack of experience and information. The traditional approach focuses on iterating and refining an initial conceptual design, which often is similar to the final one. Although this method serves well in the case of evolutionary design, it is unsuitable for innovation. In fact, without a suitable initial starting point, many rework iterations may be required to correct early inadequate design decisions. In addition, it may be challenging to map the requirements directly onto the design space. This dissertation aims at developing a methodology to address this problem. The developed framework starts from the hypothesis, and the knowledge to carry out the mapping of requirements onto the input parameters is embedded in the simulation model, and hence no additional rules are required. Instead, a probabilistic surrogate model based on Gaussian processes is used in conjunction with Bayesian statistics to find and eliminate unfeasible areas of the design space. This selection criterion is used in a set-based design approach to explore pockets of the entire continuous design space. Finally, sets with a sufficient likelihood of satisfying the requirements are searched with a local multidisciplinary optimisation algorithm to recover the individual design points. This process reduced the computational cost of the design space exploration by 80% without sacrificing the number of alternative solutions. Thanks to the large amount of data obtained, it was possible to produce new knowledge on hybrid-electric aircraft design. Specifically, it was found that linear segments are sufficient for defining energy management strategies, and the reduction of NOx emissions and fuel consumption are associated with climb and cruise, respectively. Furthermore, when studying regional aircraft operating missions, it was found that partial recharge is necessary to maintain the design performance. However, this could reduce the duration of the battery. The battery ageing rate correlates with the EMS’s demand for electrical energy. Finally, it was found that the battery’s energy density is a determinant of the pack’s durability and the feasibility of HE aircraft. The rate of improvement in emissions and fuel consumption is non-linear, suggesting that investing in considerable technological improvements has better returns. Indeed, the required technological level will not be available until the 2040s without an exponential increment of the cell energy density.Item 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.Item Open Access Adaptive intelligent traffic control systems in smart city(Cranfield University, 2023-05) Ahmed, Aminag Hardwan B.; Al-Rubaye, Saba; Panagiotakopoulos, DimitriosTraffic 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.Item Embargo Advanced turbofan architectures with alternative fuels(Cranfield University, 2023-10) Sasi, Sarath; Roumeliotis, Ioannis; Mourouzidis, ChristosAviation at present is required to reach net zero carbon emissions by 2050. An effective method to reduce aviation’s carbon footprint with immediate effect is to switch to alternative fuels. This thesis explores novel alternative fuels that could be used for future civil aviation and investigates their impacts on turbofan design to aid in research and development of future turbofan engines operating with alternative fuels. Investigations have been conducted in a systematic manner by adopting an appropriate methodology to answer the identified research questions. The proposed novel alternative fuels for civil aviation consists of seven fuels namely Hydrogen, Ammonia, Methane, DME, Butane, Butanol and Octane with SAF as an additional drop in fuel. The potential impacts and design opportunities for turbofan engines when operating with the proposed alternative fuels is highlighted through a preliminary turbofan design space exploration study. Maximum impacts in the design space are observed for zero carbon fuels Hydrogen and Ammonia. They offer 3% and 6% ESFC benefits respectively against kerosene with up to 20K and 40K peak cycle temperature reduction at take-off. The potential impacts on turbofan engine size and weight when operated by alternative fuels is brought to light through this research. Maximum impacts on engine size, weight and temperature are observed for zero carbon fuels Hydrogen and Ammonia. The maximum benefits in weight and take-off temperatures are 20% and 164K respectively for Ammonia cycles whereas for Hydrogen cycles, it is 6% and 64K respectively. The potential role that aircraft mission range can play in affecting the turbofan engines powered by alternative fuels is showcased in this thesis. Hydrogen SMR and LR aircraft leads to BPR increment up to 31.7% and 61.5% respectively considering a retrofitted style Hydrogen aircraft application.. The potential role of various fuel conditioning strategies and thermal power requirements in affecting turbofan designs highlighted through this research work indicates fuel conditioning to be a major design driver for future turbofan engines operating with alternative fuels. For the investigated LR thrust class application, Hydrogen, Methane and Ammonia requires up to 3 MW, 2.28 MW and 2.2 MW of thermal power to condition the fuel respectively. Finally, the thesis explores the feasibility of utilising Ammonia as a Hydrogen carrier in aviation and highlights certain challenges at mission level and turbofan design implications. For the investigated LR thrust class application, the amount of thermal power required to crack Ammonia into Hydrogen for the Hydrogen turbofan engines can be up to 25 MW which is interestingly an order of magnitude higher than the fuel conditioning requirements of Hydrogen, Methane and Ammonia.Item 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.Item Open Access Aeroacoustic simulation of rotorcraft propulsion systems.(Cranfield University, 2019-11) Vouros, Stavros; Pachidis, VassiliosRotorcraft 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.Item 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, CarrenA 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.Item Open Access Aeroelastic investigation of conventional fixed wings and bio-inspired flapping wings by analysis and experiment.(2018-09) Li, Hao; Guo, Shijun J.In this thesis, the structure and aeroelastic design, analysis and optimization of conventional fixed wing is firstly addressed. Based on the study results of conventional fixed wing, the study then focuses on the more complicated aerodynamics and aeroelasticity of flapping wing Micro Air Vehicles (MAV). A Finite Element (FE) model of a composite aircraft wing is firstly used as case study for the aeroelasticity of conventional fixed wing. A MATLAB-NASTRAN interfaced optimization platform is created to explore the optimal design of the wing. Optimizations using the developed platform show that 13% of weight reduction can be achieved when the optimization objective is set to minimize wing weight; and 18.5% of flutter speed increase can be achieved when aeroelastic tailoring of composite laminate layups is carried out. The study results further showed that the most sensitive part of the wing for aeroelastic tailoring is near the engine location, which contributes to the majority of flutter speed increment for optimization. In order to facilitate the structural design of non-circular cross section fuselage of Blended-Wing-Body (BWB) aircraft, an analytical model of 2D non-circular cross section is developed, which provides efficient design and optimization of the fuselage structure without referring to FE models. A case study based on a typical BWB fuselage using the developed model shows that by optimizing the fuselage structure, significant weight saving (17%) can be achieved. In comparison with the conventional fixed wing, insect flapping wings demonstrate more complicated aerodynamic and aeroelastic phenomena. A semi-empirical quasi-steady aerodynamic model is firstly developed to model the unsteady aerodynamic force of flapping wing. Based on this model, the aerodynamic efficiency of a Flapping Wing Rotor (FWR) MAV is investigated. The results show that the optimal wing kinematics of the FWR falls into a narrow range of design parameters governed by the dimensionless Strouhal number (St). Furthermore, the results show that the passive rotational of the FWR converges to an equilibrium state of high aerodynamic efficiency, which is a desirable feature for MAV applications. Next, the aerodynamic lift coefficient and efficiency of the FWR are calculated and compared with typical insect-like flapping wings and rotary wing. The results show that the aerodynamic efficiency of FWR in typical wing kinematics is higher than insect-like flapping wings, but slightly lower than the conventional rotary wing; the FWR aerodynamic lift coefficient (CL) surpassed the other wings significantly. Based on the numerical results, the study then continued to experimental investigations of the FWR. A prototype FWR model of weight 2.6g is mounted on a load cell to measure the instantaneous lift production. The kinematics of the wing is captured using high speed camera. Aeroelastic twist of the wing is measured using the resulting wing motion. Analyses by CFD and the quasi-steady aerodynamic model is then carried out and compared with experimental results. The study revealed that passive twist of the FWR wing due to aeroelastic effects forms desirable variations of wing Angle of Attack (AoA), which improves the aerodynamic performance of FWR. The results of the thesis provide guidance for structural, aerodynamic and aeroelastic design, analysis and optimization of conventional fixed wing, as well as bio-inspired flapping wing MAVs.Item Open Access Aircraft assembly process design for complex systems installation and test integration.(Cranfield University, 2019-04) Li, Tao; Lockett, Helen L.; Lawson, CraigThe assembly line planning process connects product design and manufacturing through translating design information to assembly integration sequence. The assembly integration sequence defines the aircraft system components installation and test precedence of an assembly process. From a systems engineering view point, this activity is part of the complex systems integration and verification process. At the early conceptual design phase of assembly line planning, the priority task of assembly process planning is to understand product complexities in terms of systems interactions, and generate the installation and test sequence to satisfy the designed system function and meet design requirements. This research proposes to define these interactions by using systems engineering concept based on traceable RFLP (Requirement, Functional, Logical and Physical) models and generate the assembly integration sequence through a structured approach. A new method based on systems engineering RFLP framework is proposed to generate aircraft installation and test sequence of complex systems. The proposed method integrates aircraft system functional and physical information in RFLP models and considers these associated models as new engineering data sources at the aircraft early development stage. RFLP modelling rules are created to allow requirements, functional, logical and physical modes be reused in assembly sequence planning. Two case studies are created to examine the method. Semi- structured interviews are used for research validation. The results show that the proposed method can produce a feasible assembly integration sequence with requirements traceability, which ensures consistency between design requirements and assembly sequences.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 Analysis of the effect of impact damage on the repairability of CFRP composite laminates.(2017-02) Alzeanidi, Nasser; Ghasemnejad, HessamPolymer composite materials are common in the aerospace application such as aircraft structures including primary and secondary structures. Therefore, there has been an increasing demand for composites in both the military and civilian aircraft industry. At least 50% of the next generation of military and civil aircraft structures are likely to be made from composites. The most important properties for composite materials in aircraft application was the high strength-to-weight ratios, stiffness-to-weight ratios and easy to repair. However, the composite materials have low resistance for impact damage. Impact can lead to significant strength reduction in aircraft structure about 40% to 60% of an undamaged composite laminate strength. Therefore, establish a numerical methodology to defined the optimum repair joint to restore sufficient strength of damaged aircraft composite structures during some operations and exercise activities with limited resources which will be the main contributions to knowledge in this thesis. To achieve this contribution need to understanding of the behaviour of Carbon Fibre Reinforced Plastic (CFRP) composite laminates subject to high velocity impact and the unrepaired composite laminates and repaired (stepped joint) subject to compression after impact test. Therefore, this study consists of two parts:- first, part a combined of numerical simulation and experimental investigation have been used to evaluate the woven CFRP laminate subject high velocity impact. The selected impact velocities were (140m/s, 183m/s, 200m/s, 225m/s, 226m/s, 236m/s, 270m/s, 305m/s, 354m/s and 368m/s) in order to evaluate the induced impact damage in three different thickness of CFRP composite laminates (6 mm, 4.125 mm and 2.625 mm) these velocities were selected according the gas gun limitation. The woven composite laminate made of Hexcel G0926 Carbon Fabric 5 harness 6K, Areal Weight 370 gsm. The resin used was Hexcel RTM 6, cured for 1 hour 40 minutes at 180° C at a pressure of 100 psi, with an average thickness of 0.375mm. The laminates were comprised of 16 layers, using the following stacking sequence: [(0/90); (±45); (±45); (0/90); (±45); (±45); (0/90); (0/90); (±45); (0/90); (±45); (0/90); (±45); (0/90); (±450); (0/90)], 11 layers, using the following stacking sequence: 0/90; ± 45; 0/90; ± 45; 0/90; ±45; 0/90; ± 45; 0/90; ±45; 0/90 and 7 layers, using the following stacking sequence: ± 45; 0/90; 0/90; ±45; 0/90; 0/90; ±45. The density of woven CFRP laminates was 1.512e-3 ±1e-6 grm/mmÖ³. The penetration process and also change of kinetic energy absorption characteristics have been used to validate the finite element results. The experimental and numerical method in this study show a significant damage occurs, including delamination, compression through thickness failure, out-of-plane shear failure and in-plane tensile failure of the fibres located at the rear surface when the projectile penetrates the laminate. The penetration mechanism of the projectile had a “plugging-type” (shear) failure and the hole that was formed after impact was conical in shape were shown in experimental and also verified in the numerical model. The residual kinetic energy in numerical model is 5.0 % larger than experimental data which is significantly matched in all simulated cases. In part two a finite element model is established to optimise the repair joint to restore sufficient strength of damaged composite laminate and used compression after impact test to compare the compression failure load of the sample. In order to achieve this an optimised repair models of stepped lap joints with variable parameters such as number of steps and length of steps have been experiment the undamaged composite laminate and composite laminate subject to high velocity impact and also created a numerical model for these experimental. The experimental CAI failure load of undamaged 7 Plies CFRP composite laminate higher than the failure load of damaged specimens by approximately 23%. The undamaged 11 Plies CFRP composite laminate failed at approximately 40% higher than the damaged specimens. Moreover, the difference between the experimental and numerical results of above tests was about 10%. The numerical model of repaired composite laminate show the damage initiated at the end of overlap and the average compression failure load of the stepped lap joint increased with the increasing of the number of step and length of step. The 85% and 90% of compressive failure load has been restored.Item Embargo Application of CFD zooming for preliminary design of a low emissions combustor.(2018-10) Sun, Xiaoxiao; Sethi, Vishal; Li, YiguangThe design of low emissions combustors is particularly challenging as there is a requirement to deliver designs that meet a large number of performance, emissions and operability (often conflicting) objectives. There is an increasing need for combustor preliminary design and performance tools which can be used in the early phases of the design process for rapid design space exploration thereby reducing the risk and cost in the long term. Although both reduced order models and higher fidelity tools have been widely used for preliminary design independently, significant benefit can be derived from using a multi-fidelity modelling approach to address the limitation of reduced order model (accuracy) and high fidelity CFD (time and cost). To the author’s best knowledge there is no information in the public domain related to the coupling of reduced order models with higher fidelity 3D CFD multi-fidelity modelling tools for low emissions gas turbine combustion systems. Such a tool has a potential to offer a good compromise between modelling accuracy and computational expense. In this PhD research, a novel multi-fidelity zooming combustor preliminary design method is proposed. The method uses design outcomes of an existing reduced order model based design tool to construct CFD models for a series of RANS simulations. A case study for the design of a Lean Direct Injection Partially Premixed combustor was conducted to identify the limitations of an existing reduced order modelling approach. Dedicated CFD simulations were performed to demonstrate that improved methods/models/correlations can be derived from these higher fidelity simulations to refine the existing reduced order model. The main research contributions are summarised below: External aerodynamics – Performance is sensitive to inlet velocity profiles, the effect of which cannot be reflected in ROMs, realistic compressor outlet profiles is needed instead of generic turbulent pipe flow profiles. – Performance maps were generated from CFD which include more degrees of freedom and suggest a different ‘optimum locus’ than 1D correlations. Fuel injector initial conditions – The Sauter Mean Diameter calculated from correlations in the ROM is not suitable to be used as injection initial condition. Detailed correlations on jet breakup were used to generate representative droplet size and velocity for different nozzle designs and conditions. – Swirler flow split correlations does not account for flow turning in the venturi and the pre-mixer, coarse mesh CFD was sufficient to generate more accurate flow splits among different stages. Reacting flow – The initial 10 fuel nozzle ports design from the ROM was not sufficient for good mixing quality at the main stage, which resulted in higher flame temperature. The number was increased to 16, which provides more uniform flame distribution at the circumferential direction. – Three of the four methods used to generate the time delay provides consistent results. The time delay was used as an input of the ROM thermoacoustic analysis model. – The reactor layout can be better customised for emissions prediction with extra zones within the pilot injector and the dilution zone to account for reaction and recirculation. – Combustor cooling design was refined without modifying the variables of ROM, in which circumferential distribution was not captured. Simplified re-fining method was developed at less computational expense compared to complete Conjugate Heat Transfer simulations with the radiation model. Based on these findings, the reduced order design tool could be refined once the data from all parametric study cases are extracted and incorporated in the model, which is recommended as the future development of the work. The CFD model constructed could also be used to initiate higher fidelity Large Eddy Simulation.Item Open Access Application of compressor water injection for the reduction of civil aircraft NOᵪ emissions.(2018-12) Block Novelo, David Alejandro; Igie, Uyioghosa; Nalianda, DevaiahGas turbine Nitrogen Oxide (NOx) emissions are directly proportional to combustion temperature. These contaminants are associated with respiratory diseases and damage to the local water quality and wildlife. Higher demand on civil aviation, coupled to high-pressure ratio (and thus, temperature-ratio) engines, have caused aviation-borne NOᵪ Gas turbine Nitrogen Oxide (NOx) emissions are directly proportional to combustion temperature. These contaminants are associated with respiratory diseases and damage to the local water quality and wildlife. Higher demand on civil aviation, coupled to high-pressure ratio (and thus, temperature-ratio) engines, have caused aviation-borne NOᵪ emissions to double since 1990. This is of concern around airports, at operations below 3,000 ft. where the concentration of air traffic is high and the population faces direct exposure to engine contaminants. This thesis explores the use of atomized water droplets into an engine compressor as a way of intercooling the cycle and in doing so reducing NOᵪ emissions. The use of water injection is proposed to be applied only during take-off and climb up to 3,000 ft. The analysis of water injection is firstly applied to common turbofan architectures (2 and 3-spool), under varied ambient conditions. The gas turbines are simulated by means of an in-house performance simulating tool, Turbomatch. The changes in cycle temperature when water injection is applied, are accounted for by means of a stand-alone analytical compressor model. The platform calculates the thermodynamic exchange between the gas path of the engine and the water droplets in the Lagrangian frame of reference. The engine models are then integrated into an in-house aircraft performance simulating tool, Hermes. Two types of aircraft, narrow and wide-body, are considered for operations with the water injection system. The performance benefits noted in the stand-alone engine section, are evaluated considering the extra system weight for different missions ranging from 500 to 11,000 km. The observed theoretical trends are then confirmed by means of an experiment performed on a stationary gas turbine. The test includes performance monitoring (pressures, temperatures, mass flows), water droplet measurements, and exhaust emissions analysis. The most optimistic case of water injection shows a reduction of NOx emissions greater than 50%, for the period when water is used. This technology, when applied after the fan compressor, is effective at ambient temperatures as low as 5°C and is more promising in 3-spool engines. For the shortest mission considered, equivalent to a journey from London to Paris, the aircraft benefits from a small fuel saving, despite of the extra weight. For longer missions, there is a negligible fuel penalty (0.05%) derived from the extra payload. In all the cases Landing and Take-Off (LTO) emissions are estimated to be reduced by 42-43%. A reduction of NOx emissions of 25% is achieved experimentally when injecting 2% water-to-air ratio. The study concludes that compressor water injection is a feasible solution that can significantly reduce the environmental footprint of aviation emissions to double since 1990. This is of concern around airports, at operations below 3,000 ft. where the concentration of air traffic is high and the population faces direct exposure to engine contaminants. This thesis explores the use of atomized water droplets into an engine compressor as a way of intercooling the cycle and in doing so reducing NOᵪ emissions. The use of water injection is proposed to be applied only during take-off and climb up to 3,000 ft. The analysis of water injection is firstly applied to common turbofan architectures (2 and 3-spool), under varied ambient conditions. The gas turbines are simulated by means of an in-house performance simulating tool, Turbomatch. The changes in cycle temperature when water injection is applied, are accounted for by means of a stand-alone analytical compressor model. The platform calculates the thermodynamic exchange between the gas path of the engine and the water droplets in the Lagrangian frame of reference. The engine models are then integrated into an in-house aircraft performance simulating tool, Hermes. Two types of aircraft, narrow and wide-body, are considered for operations with the water injection system. The performance benefits noted in the stand-alone engine section, are evaluated considering the extra system weight for different missions ranging from 500 to 11,000 km. The observed theoretical trends are then confirmed by means of an experiment performed on a stationary gas turbine. The test includes performance monitoring (pressures, temperatures, mass flows), water droplet measurements, and exhaust emissions analysis. The most optimistic case of water injection shows a reduction of NOᵪ emissions greater than 50%, for the period when water is used. This technology, when applied after the fan compressor, is effective at ambient temperatures as low as 5°C and is more promising in 3-spool engines. For the shortest mission considered, equivalent to a journey from London to Paris, the aircraft benefits from a small fuel saving, despite of the extra weight. For longer missions, there is a negligible fuel penalty (0.05%) derived from the extra payload. In all the cases Landing and Take-Off (LTO) emissions are estimated to be reduced by 42-43%. A reduction of NOx emissions of 25% is achieved experimentally when injecting 2% water-to-air ratio. The study concludes that compressor water injection is a feasible solution that can significantly reduce the environmental footprint of aviation.Item Open Access Assessment of non-elliptic lift distributions on span-extended wing design(Cranfield University, 2022-12) Bragado Aldana, Estela; Riaz, Atif; Whidborne, James F.In the pursuit of reducing the environmental impact of aviation, novel aircraft concepts and technologies are receiving increased attention from researchers and manufacturers. Amongst the solutions expected to improve aerodynamic efficiency, aircraft with high aspect ratio wings are being regarded as a promising solution, despite the numerous hindrances derived from such a configuration. Furthermore, the current socio-economic prospect has exacerbated the need to address the multi-disciplinary nature of the conceptual design process, in which traditional methods are becoming less reliable for the modelling of the envisioned novel configurations and technologies. To address some of these challenges, an elegant analytical approach promising improvements in the aero-structural efficiency and flight dynamic characteristics of wings has gained the interest of researchers around the world. This design approach proposes to remove the fixed-span constraint and instead prescribe structural requirements. This yields a set of non-elliptic lift distributions with theoretically improved aero-structural efficiency and lateral-directional flight dynamic characteristics. However, conclusions on the actual benefits and practical implications of the application of this theory remain unsettled. This thesis investigates some of the research questions posed by such an approach applied to the conceptual design of high aspect ratio wings. To do so, it provides a multidisciplinary physics-based design environment that integrates in-house developed and existing computational models within a setbased design approach. This allows for the analysis of feasible solutions with regard to overall performance improvement whilst shedding light on the relevant trade-offs. The proposed design and analysis approach yields span-extended configurations for which aerodynamic efficiency is improved through span extension and the consequent growth in wing structural weight is reduced as a result of the applied non-elliptic spanloads. The presentation of alternative figures of merit to comparatively assess the performance of the designs provides further insight than the use of other traditional metrics such as the lift-to-drag ratio. This yields several span-extended configurations without penalties in performance, following the methodology and metrics employed in the proposed design and analysis process. Furthermore, the semi-analytical approach to proverse yaw enables to identify the unconventional behaviour of induced drag during aileron deflection on wings with the selected non-elliptic spanloads. Additionally, it highlights that attainment of these solutions are highly dependent on flight condition, aileron sizing and location within a given spanload, and the magnitude of deflection. Overall, this thesis contributes to a further insight on the aero-structural trade-offs and proverse yaw characteristics derived from the use of such a design approach. This can facilitate the identification of the determining contributors and compromises to be made at early stages of the design, amplifying the designer’s control over the design and decision-making processes, while delaying critical decisions and enhancing the optimisation process with more informed drivers.Item Open Access Assumption management in model-based systems engineering: an aircraft design perspective.(2021-12) El Fassi, Soufiane; Riaz, Atif; Guenov, Marin D.Early design of complex systems is characterised by significant uncertainty due to lack of knowledge, which can impede the design process. In order to proceed with the latter, assumptions are typically introduced to fill knowledge gaps. However, the uncertainty inherent in the assumptions constitutes a risk to be mitigated. In fact, assumptions can negatively impact the system if they turn out to be invalid, such as causing system failure, violation of requirements, or budget and schedule overruns. Within this context, the aim of this research was to develop a computational approach to support assumption management in model-based systems engineering, with an explicit consideration of the uncertainty in assumptions. To achieve the research aim, the objectives were to: (1) devise methods to enable assumption management in a model-based design environment; and (2) devise methods to manage risk of change due to invalid assumptions, with an explicit consideration of both assumptions and margins. The scope was limited to the early stages of aircraft design. To evaluate this research, a demonstration was performed based on two use cases to assess whether the methods work as intended. The developed methods were demonstrated to industry experts in order to obtain feedback on expected usefulness in practice, thus assessing the impact of this research. The experts concluded that the proposed methods are innovative, useful and relevant to industry, where these methods can lead to: (i) fewer undesired iterations, due to earlier identification and management of risks associated with assumptions; and (ii) a better margin balance, due to timely and interactive margin revision. Future work includes further industrial evaluation, extending the research scope and studying the scalability and associated costs of the proposed methods.Item Open Access Boundary layer ingestion performance assessments with application to business jets.(2018-07) Sanders, Drewan S.; Laskaridis, PanagiotisAdvancements in propulsion system performance are reliant on improvements in propulsive efficiency, through increases in turbofan bypass ratio. This requires larger nacelle diameters, which incur external aerodynamic penalties. Business jets cruise at high subsonic Mach numbers, and are therefore normally propelled by high specific thrust turbofans. The business jet may benefit from a BLI propulsion system, whereby the specific thrust may be reduced without incurring such heavy penalties in external drag rise. The aim of the research is to perform a design exploration study on BLI applied to a business jet, with emphasis on external aerodynamics. Methods are developed to thoroughly analyse aerodynamic coupling between propulsor and airframe. A multi-physics, control-volume based approach led to the development of near-field momentum-based, far-field momentum-based and energy-based net-vehicle-force formulations. The former two, allowed for a set of thrust-force accounting systems to be defined. Energy-based methods, allowed for flow-field decompositions into different physical mechanisms. These include flow phenomena internal and external to the jet plume. The practical implications associated with applying these methods to RANS CFD solutions, is examined. This hinges around viscous stress tensor field continuity in the flow domain. It was found that the k — w SST turbulence model, along with a Green-Gauss Cell-Based gradient scheme, produced a continuous viscous stress tensor field. Having resolved this, the assessment methods were applied to solutions of non-propelled and propelled bodies. These methods were applied to control volumes having varying extents, which showed the far-field momentum-based method to be sensitive to spurious affects. The energy-based formulation, on the other hand, was observed to be relatively insensitive spurious affects. Good agreement (within 4%) was found between the forces predicted by all three methods over a non-propelled body. A very close agreement was observed between far-field momentum-based and energy-based results (within 1%) over the propelled body. However, much larger discrepancies were observed when compared against the near-field results. This was attributed to the increase in flow-field complexity, which now contained BL, shock and jet interaction regions. A design exploration study was performed by retrofitting a business jet with a fuselage concentric propulsor, powered by the baseline podded engines. A preliminary parametric study was first performed to gauge conditions favourable to BLI benefit. A ram drag approach to modelling BLI benefit was based on a flat plate analogy to obtain boundary layer profiles. Thrust-split, BLR, fan efficiency and intake pressure recoveries, were varied parametrically to asses potential benefits. An optimum SFC benefit between 5-7.5% was achieved at thrustsplits between 30-35%, when ingesting 65-90% of the BL thickness. This guided the the parametric CFD studies, where two tail-cone positions were examined. The first was placed at the top of the tail-cone, and the second positioned midway along the tail-cone. Benefits were only realised for the latter, where a 3-4% improvement in SFC was realised for a thrust-split around 20%, by ingesting 40% of the BL thickness. Energy breakdowns and decompositions were performed on all of the cases. One of the significant outcomes of this research was revealing that a significant proportion of the thrust force may be attributed to the isentropic expansion region within the jet plume's core.Item Open Access Building safety into the conceptual design of complex systems. An aircraft systems perspective.(2021-06) Jimeno Altelarrea, Sergio; Guenov, Marin D.; Riaz, AtifSafety is a critical consideration during the design of an aircraft, as it constrains how primary functions of the system can be achieved. It is essential to include safety considerations from early design stages to avoid low-performance solutions or high costs associated with the substantial redesign that is commonly required when the system is found not to be safe at late stages of the design. Additionally, safety is a crucial element in the certification process of aircraft, which requires compliance with safety requirements to be demonstrated. Existing methods for safety assessment are limited in their ability to inform architectural decisions from early design stages. Current techniques often require large amounts of manual work and are not well integrated with other system engineering tools, which translates into increased time to synthesise and analyse architectures, thus reducing the number of alternative architectures that can be studied. This lack of timely safety assessment also results in a situation where safety models evolve at a different pace and become outdated with respect to the architecture definition, which limits their ability to provide valuable feedback. Within this context, the aim is to improve the efficiency and effectiveness of design for safety as an integral part of the systems architecting process. Three objectives are proposed to achieve the stated aim: automate and integrate the hazard assessment process with the systems architecting process; facilitate the interactive introduction of safety principles; and enable a faster assessment of safety and performance of architectures. The scope is restricted to the earlier (conceptual) design stages, the use of model-based systems engineering for systems architecting (RFLP paradigm) and steady-state models for rapid analysis. Regarding the first objective, an enabler to support the generation of safety requirements through hazard assessment was created. The enabler integrates the RFLP architecting process with the System-Theoretic Process Analysis to ensure consistency of the safety assessment and derived safety requirements more efficiently. Concerning the second objective, interactive enablers were developed to support the designer when synthesizing architectures featuring a combination of safety principles such as physical redundancy, functional redundancy, and containment. To ensure consistency and reduce the required amount of work for adding safety, these methods leverage the ability to trace dependencies within the logical view and between the RFLP domains of the architecture. As required by the third objective, methods were developed to automate substantial parts of the creation process of analysis models. In particular, the methods enable rapid obtention of models for Fault Tree Analysis and subsystem sizing considering advanced contextual information such as mission, environment, and system configurations. To evaluate this research, the methods were implemented into AirCADia Architect, an object-oriented architecting tool. The methods were verified and evaluated through their applications to two aircraft-related use cases. The first use case involves the wheel brake systems and the second one involves several subsystems. The results of this study were presented to a group of design specialists from a major airframe manufacturer for evaluation. The experts concluded that the proposed framework allows architects to define and analyse safe architectures faster, thus enabling a more effective and efficient design space exploration during conceptual design.Item Open Access Component-driven computational design of complex engineering systems.(2018-08) Bile, Yogesh Hanumant; Guenov, Marin D.; Molina-Cristobal, ArturoDuring the conceptual design of complex systems, architects study a number of different options, which comprise the architectural design space. Usually, new system architectures (SAs) are created by modifying existing ones, e.g., by deleting existing and/or adding new elements. Once the concept is synthesised, the architect wishes to swiftly find the effect of the proposed architectural changes at system level. This would involve sizing of the modified sub-systems, and then, obtaining the system level performance. In turn, this involves time-consuming activities, such as re-arrangement (orchestration) of computational tasks and models. Also, depending on the results, the architect may undertake further modifications. When doing this, a means to navigate across the RFLP (Requirements-Functional-Logical-Physical) views of the SA may be required, in order to trace elements affected by these modifications. Generally, several iterations are involved between architecting and sizing during conceptual design, which, if manually performed, result in a tedious and time-consuming process. There are existing methods which address this problem, but these have significant limitations in that they are usually system specific and often involve an excessive amount of time-consuming manual tasks. Within this context, the research aim is to improve the efficiency of the architectural design space exploration (ADSE) process, by automating repetitive computational tasks, thus enabling the designer to swiftly and interactively explore multiple SA options. A novel method, comprised of two parts, has been developed to achieve the aim. In the first part, a graph-theoretic approach is employed to enable architectural element dependency analysis. Here, the relationships between the architectural elements are stored as a graph. Algorithms, such as ‘Depth First Search’ and ‘Transitive Closure’ are then applied to assist the architect in tracing the dependencies between elements that might be affected by a proposed change to other elements of the SA. In the second part, the architecture is assessed to find the system level performance. The inputs needed for rapid assessment include the functional and logical views of the SA, and the requisite steady-state computational models associated with each of the ‘logical’ components. The assessment process itself consists of three steps. In the first step, the sequence of the sub-systems is automatically generated by extracting a sub-systems source-sink ‘Dependency Structure Matrix (DSM)’ from the logical view, followed by the application of an algorithm which determines the systems’ sizing sequence. In the second step, the individual sub-systems and system level workflows are constructed. Here, the computational workflow (a network of computational models) is represented as a bipartite graph. A maximum matching enumeration algorithm is used to find all possible workflows for a given model set, and another algorithm, to choose from these the most computationally efficient one, i.e., the workflow with the lowest number of reversed variables. In the third step, the workflows produced in the second step and subsystems ’sizing sequence obtained in the first step are combined to produce a complete workflow. To demonstrate and evaluate the proposed enablers, the author developed a prototype object-oriented architecting tool. The enablers were individually and collectively verified on representative test-cases. Comparison with the existing methods confirmed the claimed advantages of the proposed approach, namely, reducing the number of manual activities, which results in swifter and interactive ADSE process. Feedback obtained from experts in the aircraft industry during an initial qualitative evaluation session confirmed the usefulness of the proposed method.Item Open Access Computational techniques for aircraft evolvability exploration during conceptual design.(2018-02) van Heerden, Albert Stevan Johan; Guenov, Marin D.; Molina-Cristobal, ArturoEvolvability is a critical consideration during the design of an aircraft. It refers to the extent to which a baseline design could be reused, or `easily' modified to create descendant designs that would meet future requirements. Since a major fraction of the cost of an aircraft programme is determined by decisions made during conceptual design, it is essential that the design space is explored thoroughly during this stage to find evolvable designs. Existing computational methods to perform such exploration exist, but are limited in two respects. The first of these is that, with existing techniques, derivatives are usually generated by applying pre-specified modifications to a selected baseline, such that each derivative in a study is only linked to a single baseline. The designer must therefore evaluate large numbers of baseline-derivative pairs to adequately capture the evolution options available. The second limitation concerns an absence of appropriate down-selection criteria to narrow down the number of design points when evolvability is considered. The work presented in this thesis addresses these limitations. The aim was to develop computational techniques that would enable aircraft designers to explore the evolvability of their designs more efficiently and effectively during the conceptual design stage. The scope was limited to civil transport aircraft and specifically to airframes. The work is applicable to both single- and twin-aisle aircraft, but the focus was, to a small degree, more on single-aisles. The research resulted in two main contributions: 1) a framework to provide a means to link all derivatives to all the baselines; and 2) a set of techniques to filter out inferior designs systematically. The framework builds on the premise that the degree of `similarity' between two ,designs could be used as an estimate for the redesign e ort (i.e. resource expenditure) required to change one of these into the other. Case studies involving existing aircraft families were conducted to determine which design changes could be considered `reasonable'. Based on this information, a set of techniques to assess airframe similarity was developed, which involves automatically predicting possible commonality across two designs. Several algorithms were devised to achieve this, including one that solves a longest common subsequence problem to find common body segments and a simple optimisation procedure to find common wing elements. Notably, these techniques can be used to compare aircraft with dissimilar configurations. For testing purposes, the framework was applied to several existing and future aircraft. The results showed that the predicted commonality matches published information regarding commonality and design re-use between designs. The framework essentially removes the need to model each future design option based on a specific starting design. The design filtering techniques involve the application of set-based design to facilitate systematic down-selection of potential designs. Specifically, it is demonstrated how established set-based design criteria could be adapted to prune an evolvability design space progressively. To demonstrate the usefulness of the research, it was applied to an example, concerning design candidates for a new single-aisle, environmentally friendly passenger aircraft. The results of this study were presented to a panel of design specialists from Airbus UK. The panel concluded that the proposed similarity assessment provides reasonable initial estimates for redesign e ort and that the overall approach adds value to the evolvability exploration process.