Staff publications (AA)

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Open Access
Use of non-intrusive flow diagnostics for aero-engine inlet flow distortion measurements in an industrial wind-tunnel
(AIAA, 2025-01-06) Piovesan, Tommaso; Zachos, Pavlos K.; MacManus, David; Michaelis, Dirk; van Rooijen, Bart; Sheaf, Christopher; Arzoglou, Dimitris
In crosswind conditions, aero-engine intakes experience unsteady flow distortions at the fan face, typically caused by the ingestion of ground vortices and flow separation. These distortions can negatively impact both intake performance and the compatibility of the downstream propulsion system. Understanding the aerodynamics of these flows is crucial for developing next-generation aircrafts with propulsion systems integrated more closely with the airframe. Optical measurement techniques provide detailed datasets in both space and time to support this understanding, but several challenges limit their widespread use in propulsion integration testing. This study demonstrates a novel application of non-intrusive flow diagnostics in an industrial setting for propulsion integration testing. Optical measurements were conducted within an aspirated intake configuration and, later, within a fully coupled fan-intake propulsion system representative of a modern high-bypass aero-engine. Several innovative solutions were developed to improve the integration of optical systems into industrial settings and enhance data acquisition efficiency. The analysis of the results yielded significant contributions about the unsteady interactions within civil intakes at crosswind and high incidence conditions, which are expected to have a notable impact on the development of future, closely integrated propulsion systems architectures able to meet the specified NetZero targets.
Open Access
Framework for multi-fidelity simulations of flow interaction and noise of an open rotor
(American Institute of Aeronautics and Astronautics, 2025-01-06) Huang, Guangyuan; Sharma, Ankit; Chen, Xin; Jimeno, Sergio; Riaz, Atif
Flow-induced noise from open rotor aircraft has received immense research interests as the flow interactions of the components of open rotors lead to significant non-linear features and the flow-induced noise is complicated. Numerical approaches for predicting open rotor flow interactions and the induced noise are in demand without compromising computational accuracy and reducing cost. In this paper, an existing multi-fidelity framework for propeller noise modelling is extended to open rotor configuration. A generic contra-rotating open rotor (CROR) configuration is developed to assess the capability of this multi-fidelity framework. The flow and noise of this configuration are modelled separately in hybrid manner. The flow solution is computed using two methods, which employ unsteady Reynolds average Navier-Stokes (URANS) equations and lattice-vortex method (VLM) at respectively higher- and lower-fidelity levels. Then, the acoustic solution is computed based on the flow solution using Gutin’s method. Results show that transonic features over the rotor blades and significant tip vortices in the wake characterise the CROR flow. Multi-rotor interactions are observed. The aerodynamic loadings are investigated in terms of their mean and fluctuating components. In addition, the far-field noise from the two rotors are compared. The present multi-fidelity framework will be used in future aircraft design which involves open rotor engines. This work is being administered as part of the Innovate UK, Aerospace Technology Institute (ATI) funded research project - ONEheart (Out of Cycle NExt generation highly efficient air transport).
Open Access
Adaptive UAV control with sensor and actuator faults recovery
(MDPI, 2025-03-01) Bekhiti, Abdellah; Souanef, Toufik; Toubakh, Houari; Horri, Nadjim; Kafi, Mohamed Redouane; Bouzid, Zakaria
This paper presents an adaptive fault-tolerant control strategy tailored for fixed-wing unmanned aerial vehicles (UAV) operating under adverse conditions such as icing. Using radial basis function neural networks and nonlinear dynamic inversion, the proposed framework effectively handles simultaneous actuator and sensor faults with arbitrary nonlinear dynamics caused by environmental effects, model uncertainties and external disturbances. A nonlinear disturbance observer is incorporated for accurate sensor fault detection and estimation, thereby enhancing the robustness of the control system. The integration of the radial basis function neural network enables an adaptive estimation of the faults, ensuring accurate fault compensation and system stability under challenging conditions. The observer is optimised to minimise the deviation of the closed-loop dynamics eigenvalues from the assigned eigenvalues and to approach unity observer steady-state gain. The stability of the control architecture is mathematically proven using Lyapunov analysis, and the performance of the approach is validated through numerical simulations on a six Degrees of Freedom fixed-wing unmanned aerial vehicles model. The results show superior performance and robustness to challenging fault scenarios. This research provides a comprehensive fault management solution that enhances the safety and reliability of unmanned aircraft operations in extreme environments.
Open Access
Fault diagnosis across aircraft systems using image recognition and transfer learning
(MDPI, 2025-03-02) Jia, Lilin; Ezhilarasu, Cordelia Mattuvarkuzhali; Jennions, Ian K.
With advances in machine learning, the fault diagnosis of aircraft systems is becoming more efficient and accurate, which makes condition-based maintenance possible. However, current fault diagnosis algorithms require abundant and balanced data to be trained, which is difficult and expensive to obtain for aircraft systems. One solution is to transfer the diagnostic knowledge from one system to another. To achieve this goal, transfer learning was explored, and two approaches were attempted. The first approach uses relational similarity between the source and target domain features to enable the transfer between two different systems. The results show it only works when transferring from the fuel system to ECS but not to APU. The second approach uses image recognition as the intermediate domain linking the distant source and target domains. Using a deep network pre-trained with fuel system images or the ImageNet dataset finetuned with a small amount of target system data, an improvement in accuracy is found for both target systems, with an average of 6.90% in the ECS scenario and 5.04% in the APU scenario. This study outlines a pioneering approach that transfers knowledge between completely different systems, which is a rare transfer learning application in fault diagnosis.
Open Access
Assessing uninstalled hydrogen-fuelled retrofitted turbofan engine performance
(MDPI, 2025-03-12) Farabi, Jarief; Mourouzidis, Christos; Pilidis, Pericles
Hydrogen as fuel in civil aviation gas turbines is promising due to its no-carbon content and higher net specific energy. For an entry-level market and cost-saving strategy, it is advisable to consider reusing existing engine components whenever possible and retrofitting existing engines with hydrogen. Feasible strategies of retrofitting state-of-the-art Jet A-1 fuelled turbofan engines with hydrogen while applying minimum changes to hardware are considered in the present study. The findings demonstrate that hydrogen retrofitted engines can deliver advantages in terms of core temperature levels and efficiency. However, the engine operability assessment showed that retrofitting with minimum changes leads to a ~5% increase in the HP spool rotational speed for the same thrust at take-off, which poses an issue in terms of certification for the HP spool rotational speed overspeed margin.
Open Access
Integrated power and thermal management system in a parallel hybrid-electric aircraft: an exploration of passive and active cooling and temperature control
(MDPI, 2025-03-13) Ouyang, Zeyu; Nikolaidis, Theoklis; Jafari, Soheil; Pontika, Evangelia
Hybrid-electric aircraft (HEAs) represent a promising solution for reducing fuel consumption and emissions. However, the additional heat loads generated by the electrical propulsion systems in HEAs can diminish these benefits. To address this, an integrated power and thermal management system (IPTMS) is essential to mitigate these challenges by optimizing the interaction between thermal management and power management. This paper presents a preliminary IPTMS design for a parallel HEA operating under International Standard Atmosphere (ISA) conditions. The design includes an evaluation of active cooling, passive cooling, and active temperature control strategies. The IPTMS accounts for heat loads from the engine system, including the generators, shaft bearings, and power gearboxes, as well as from the electrical propulsion system, such as motors, batteries, converters, and the electric bus. This study investigates the impact of battery power (BP) contribution to cooling power on required coolant pump power and induced ram air drag. A comparison of IPTMS performance under 0% and 100% BP conditions revealed that the magnitude of battery power contribution to cooling power does not significantly impact the thermal management system (TMS) performance due to the large disparity between the total battery power (maximum 950 kW) and the required cooling power (maximum 443 W). Additionally, it was determined that the motor-inverter loop accounts for 95% of the pump power and 97% of the ram air drag. These findings suggest that IPTMS optimization should prioritize the thermal domain, particularly the motor-inverter loop. This study provides new insights into IPTMS design for HEAs, paving the way for further exploration of IPTMS performance under various operating conditions and refinement of cooling strategies.
Open Access
Use of Bayesian Networks to understand sustainability requirements
(MDPI, 2025-03-13) Spinelli, Andrea; Kipouros, Timoleon
Sustainability is a key requirement in contemporary engineering design, but it is difficult to quantify due to its multidimensionality. We propose the application of Bayesian Networks for modeling the cause and effect of engineering systems and their environment. Emphasis is placed on capturing the impact on sustainability indicators of design decisions. These include the performance of the system, its economic viability in terms of cost, and its environmental and societal impacts. The method leverages data from simulation models, enabling the designer to perform assumption-free inferences on the variables at play.
Open Access
Installation effects of supersonic inlets on next-generation SST turbofan engines
(MDPI, 2025-03-14) Adamidis, Stylianos; Del Gatto, Dario; Mourouzidis, Christos; Brown, Stephen; Pachidis, Vassilios
This study explores inlet-related installation effects on next-generation SST aircraft, focusing on supersonic business jets. Using a comprehensive framework with consistent thrust/drag bookkeeping and realistic modeling of inlet losses, including operational limits for “buzz” and distortions, the inlet drag accounts for 8.8% to 14.2% of the installed net thrust during the supersonic segment of the mission. Variable airflow control technology is assessed, with a scheduling methodology developed to optimize the inlet operation by minimizing the installed SFC. The results show that this technology improves the installed SFC by 0.80% during supersonic cruise, enhancing the overall propulsion system performance.
Open Access
Impact monitor framework: development and implementation of a collaborative framework for aviation impact assessment
(MDPI, 2025-03-18) Alder, Marko; Ratei, Patrick; Riaz, Atif; Gupta, Utkarsh; Lefebvre, Thierry; Prakasha, Prajwal Shiva
The development and implementation of a collaborative framework for aviation impact assessment studies is presented. The focus is on which technologies can be used to enable the collaborative aspect, including the use of a common data model, the secure transfer of data between domain experts in different locations, and the automated execution of impact assessment workflows. It is demonstrated how the selected technologies can be extended to meet the requirements of air transport systems assessment and how they can be integrated into a common framework. The results of the developments are discussed in terms of their technical capabilities and the lessons learned from their practical use. The proposed framework shows that collaborative impact assessment studies can be conducted efficiently and securely. This forms the basis for three application studies in the same research project.
Open Access
Energy optimization strategies for automatic tiltrotor electric vertical takeoff and landing aircraft
(AIAA, 2025-03-25) Kang, Namuk; Lu, Linghai; Whidborne, James F.
Open Access
Advanced thermal imaging processing and deep learning integration for enhanced defect detection in carbon fiber-reinforced polymer laminates
(MDPI, 2025-03-25) Garcia Rosa, Renan; Pereira Barella, Bruno; Garcia Vargas, Iago; Tarpani, José Ricardo; Herrmann, Hans-Georg; Fernandes, Henrique
Carbon fiber-reinforced polymer (CFRP) laminates are widely used in aerospace, automotive, and infrastructure industries due to their high strength-to-weight ratio. However, defect detection in CFRP remains challenging, particularly in low signal-to-noise ratio (SNR) conditions. Conventional segmentation methods often struggle with noise interference and signal variations, leading to reduced detection accuracy. In this study, we evaluate the impact of thermal image preprocessing on improving defect segmentation in CFRP laminates inspected via pulsed thermography. Polynomial approximations and first- and second-order derivatives were applied to refine thermographic signals, enhancing defect visibility and SNR. The U-Net architecture was used to assess segmentation performance on datasets with and without preprocessing. The results demonstrated that preprocessing significantly improved defect detection, achieving an Intersection over Union (IoU) of 95% and an F1-Score of 99%, outperforming approaches without preprocessing. These findings emphasize the importance of preprocessing in enhancing segmentation accuracy and reliability, highlighting its potential for advancing non-destructive testing techniques across various industries.
Open Access
Cluster-based tracking method for the identification and characterisation of vortices
(Association Aéronautique et Astronautique de France (3AF), 2025-03-26) Ibanez, Claudia; Migliorini, Matteo; Giannouloudis, Alexandros; Tejero, Fernando; Zachos, Pavlos K.
An unsupervised, flow-agnostic and automatic cluster-based tracking algorithm for the segmentation of vortex-dominated flows has been successfully developed. It combines the Rortex method and density-based clustering algorithms. The Rortex method differs shear from rotation and overcomes the sensitivity to user-defined thresholds that characterises current practice of vortex identification methods. The algorithm is demonstrated with experimental Stereoscopic Particle Image Velocimetry data from two cases; a high-Reynolds (≈ 106) vortex generated by a half-delta wing, and distorted flow in a scaled-model of a civil aero-engine intake under cross-wind conditions. The approach is a successful method for the segmentation of complex vortical flows under a wide range of conditions.
Open Access
Aerodynamics of a short intake at high incidence
(European Turbomachinery Society, 2025-03-28) Tejero, Fernando; MacManus, David; Hueso Rebassa, Josep; Frey Marioni, Yuri; Bousfield, Ian
This work assesses the aerodynamics of a short aero-engine intake for a new rig that is planned to be tested at the Large Low-Speed Facility of the German Dutch Wind Tunnels (LLF-DNW) in 2025. A range of computations were performed to assess if the expected aerodynamics in this arrangement encompass the envisaged range of flow field characteristics of the equivalent isolated configuration. The effect of massflow capture ratio and angle of attack are investigated. In addition, an intake flow separation taxonomy is proposed to characterize the associated flows. The wind tunnel analysis is based on two different modelling approaches: an aspirated isolated intake and a coupled fan-intake configuration. The coupled configuration uses a full annulus model with a harmonic mixing plane method. Across the range of operating conditions with changes in massflow capture ratio and angle of attack, there are attached and separated flows. The main separation mechanisms are diffusion-driven and shock-induced, which shows the different aerodynamics that may be encountered in a short intake. Overall, this work provides an initial evaluation of the aerodynamics of the new fan/intake test rig configuration, provides guidance for the wind tunnel testing, and lays a foundation for subsequent unsteady coupled fan-intake studies.
Open Access
Assessing advanced propulsion systems using the impact monitor framework
(MDPI, 2025-03-28) Gupta, Utkarsh; Riaz, Atif; Brenner, Felix; Lefebvre, Thierry; Ratei, Patrick; Alder, Marko; Prakasha, Prajwal Shiva; Weber, Lukas; Pons-Prats, Jordi; Markatos, Dionysios
Presented in this paper is the Impact Monitor framework and interactive Dashboard Application (DA) validated through a use case, focusing on investigating the viability and competitiveness of future propulsion architectures for next-generation aircraft concepts. This paper presents a novel collaborative framework for integrated aircraft-level assessments, focusing on secure, remote workflows that protect intellectual property (IP) while enabling comprehensive and automated analyses. The research addresses a key gap in the aerospace domain: the seamless matching and sizing of aircraft engines within an automated workflow that integrates multiple tools and facilitates real-time data exchanges. Specifically, thrust requirements are iteratively shared between aircraft and engine modeling environments for synchronized sizing. Subsequently, the fully defined aircraft data are transferred to other tools for trajectory analysis and emissions and other assessments. The Impact Monitor framework and Dashboard Application demonstrate improved efficiency and data security, promoting effective collaboration across institutions and industry partners.
Open Access
Unsteady flow interactions and ground plane proximity in a coupled compact intake-fan in crosswind
(Association Aéronautique et Astronautique de France (3AF), 2025-04-01) Lobuono, Luca; MacManus, David G.; Hueso Rebassa, Josep; Christie, Robert
The assessment of the crosswind flow separation mechanisms and resulting distortion for compact intakes can be a key contributor for the design of viable large civil aeroengines. Under crosswind conditions, the intake aerodynamics are strongly influenced by both the fan and the ground plane. However, the impact of key design parameters, such as ground clearance, on the intake flow distortion is not fully understood. This study investigates the effects of a large variation in ground clearance on the intake-fan unsteady aerodynamics using an Unsteady Reynolds-Averaged Navier-Stokes fully coupled with a rotating fan stage. The work includes an assessment of the unsteady swirl distortion and the unsteady peak distortion events. The findings show that increased ground clearance can have adverse effects for the considered compact intake design. Gross separation can occur at lower crosswind velocities and arise at the intake lower section due to mass flow redistribution. When the ground clearance is increased, the gross separation on the windward side of the intake occurs at a greater crosswind velocity but exhibits greater levels of unsteady intake flow distortion. Overall, intake designs should be assessed at the expected ground clearance as the distortion and the onset of separation can vary substantially.
Open Access
Advanced diagnostics of aircraft structures using automated non-invasive imaging techniques: a comprehensive review
(MDPI, 2025-04-01) Bardis, Kostas; Avdelidis, Nicolas P.; Ibarra-Castanedo, Clemente; Maldague, Xavier P. V.; Fernandes, Henrique
The aviation industry currently faces several challenges in inspecting and diagnosing aircraft structures. Current aircraft inspection methods still need to be fully automated, making early detection and precise sizing of defects difficult. Researchers have expressed concerns about current aircraft inspections, citing safety, maintenance costs, and reliability issues. The next generation of aircraft inspection leverages semi-autonomous and fully autonomous systems integrating robotic technologies with advanced Non-Destructive Testing (NDT) methods. Active Thermography (AT) is an example of an NDT method widely used for non-invasive aircraft inspection to detect surface and near-surface defects, such as delamination, debonding, corrosion, impact damage, and cracks. It is suitable for both metallic and non-metallic materials and does not require a coupling agent or direct contact with the test piece, minimising contamination. Visual inspection using an RGB camera is another well-known non-contact NDT method capable of detecting surface defects. A newer option for NDT in aircraft maintenance is 3D scanning, which uses laser or LiDAR (Light Detection and Ranging) technologies. This method offers several advantages, including non-contact operation, high accuracy, and rapid data collection. It is effective across various materials and shapes, enabling the creation of detailed 3D models. An alternative approach to laser and LiDAR technologies is photogrammetry. Photogrammetry is cost-effective in comparison with laser and LiDAR technologies. It can acquire high-resolution texture and colour information, which is especially important in the field of maintenance inspection. In this proposed approach, an automated vision-based damage evaluation system will be developed capable of detecting and characterising defects in metallic and composite aircraft specimens by analysing 3D data acquired using an RGB camera and a IRT camera through photogrammetry. Such a combined approach is expected to improve defect detection accuracy, reduce aircraft downtime and operational costs, improve reliability and safety and minimise human error.
Open Access
Performance evaluation approach for design space explorations of propulsive fuselage aircraft concepts
(Springer, 2025-04-01) Moirou, Nicolas G. M.; Sanders, Drewan S.
A promising architecture to enhance the performance of next-generation commercial aircraft involves embedding the propulsion system within the airframe, thereby capturing energy from the fuselage through boundary layer ingestion. However, in cases of strong aerodynamic coupling, traditional accounting methods break down, necessitating alternative approaches. The lack of consensus surrounding the interpretation and quantification of these benefits underscores the need for a unified assessment method. In this work, commonly used near-field momentum-based bookkeeping schemes are discussed and unified with a more holistic energy-based approach to evaluate aero-propulsive performance and facilitate more intuitive physical interpretations of the aerodynamics. The contribution of this work lies in the correction of the power balance, leading to the development of new metrics for assessing the efficiencies of both the aircraft and the boundary layer ingestion propulsion system. Notably, a surrogate for propulsive efficiency and limits to the power saving coefficient are given, which address inconsistencies present in the literature. Despite their application to an axi-symmetric propulsive fuselage, the metrics introduced are applicable to higher levels of representativity of propulsive fuselage concepts. The potential impact of this work is the transformation of established evaluation practices by employing these newly introduced metrics to assess aircraft and system efficiencies.
Open Access
Pilots’ training backgrounds affecting the attribution of event causal factors and airline safety management
(Elsevier, 2025-05) Chan, Wesley Tsz-Kin; Li, Wen-Chin; Braithwaite, Graham
For safety management in diverse aviation operators, it is necessary to investigate how different cultural factors interact in flight operations. Whilst prior studies have evaluated between-group cultural differences, there remains a research gap on whether within-group subcultural differences challenge the assimilation of people into the safety culture of the wider group. Cultural differences in how causal factors are perceived in the context of systemic safety deficiencies can affect the implementation of safety management strategies. In the present study, pilots from airline-sponsored, self-funded, and ex-military initial training backgrounds were invited to categorise an identical set of aircraft accident causal factors using the Human Factors Analysis and Classification System (HFACS). Results from 121 participants found significant differences amongst the three groups in the attribution of human factors conditions to organisational-level and supervisory-level categories. Significant associations amongst HFACS categories also differed amongst the three professional groups, with a considerable number of same-level associations found between ‘Preconditions for Unsafe Acts’ at the same level. Familiarity with organizational cultures was considered to impact the perception of causal factors. The finding of same-level associations presents a new contribution to the theoretical basis of the HFACS taxonomy, calling for a conceptual change in the directionality of causal sequences. The results suggest that the direction of safety remedies for different parts of the organisation is dependent on perceived relevance, which differs amongst subcultural groups. Findings are relevant to industry, particularly international airlines with diverse employee subcultural groups, for the implementation of safety management systems.
Open Access
Creating more viable safety recommendations in accident investigation by revising the human factors intervention matrix (HFIX)
(Elsevier, 2025-05-01) Chan, Wesley Tsz-Kin; Li, Wen-Chin; Yeun, Richard; Wang, Thomas
Open Access
A review of hydrogen micromix combustion technologies for gas turbine applications
(Elsevier, 2025-05-13) Singh, Gaurav; Schreiner, B. Deneys J.; Sun, Xiaoxiao; Sethi, Vishal
Hydrogen micromix combustion is a promising technology for gas turbines, introducing rapid, miniaturized air-fuel mixing, significantly reducing combustion zone length and nitrogen oxides (NOx) emissions. This review evaluates the state-of-the-art hydrogen micromix combustion technologies, focusing on injector performance, flashback characteristics, and NOx reduction strategies. Injector designs are categorized based on premixing and flame stabilization techniques. While stationary gas turbines approach Technology Readiness Level (TRL) 9, aviation applications remain below TRL 4. This review identifies key design principles and predictive modelling challenges and presents a development roadmap for advancing hydrogen micromix combustion technology for aviation from TRL 4 to TRL 9 by 2040.

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