Because of their considerably higher fuel efficiency compared to turbofans, turboprop aircraft are the best choice for short and middle-haul flights. Yet, propeller acoustic emissions need to be reduced to comply with future noise certification standards, and to improve the comfort of passengers and crew. The CFD solver of the University of Glasgow, HMB3, was first validated for propeller aerodynamics and acoustics against JORP and IMPACTA wind tunnel data, and then employed for comparing different innovative designs and installation options to identify the quietest solution. OSPL and frequency tonal spectra were directly computed from (U)RANS results. Cabin noise was estimated via experimental transfer functions. The design of the propeller is the key to decrease the emitted sound at source level. A blade design that moves the loading inboard and operates at lower rotational speed yielded relevant noise gains (up to 6 dB in OSPL) without strong performance penalties. Hub configurations meant to redistribute the acoustic energy over more frequencies did not clearly appear more pleasant for passengers. The presence of the airframe modifies the propeller inflow, and causes additional noise sources as well as sound waves reflections. The need of simulating the whole airplane in real operating conditions to accurately estimate in-flight noise was shown. For a twin-engined high-wing aircraft with propellers in phase at cruise conditions, the counter-rotating top-in layout was found the quietest, with a benefit in interior OSPL of more than 4 dB compared to co-rotating propellers. The inboard-up propeller rotation led louder noise because of the higher blade loading on the fuselage side, and of constructive sound waves interferences. The latters are instead used favorably from propeller synchrophasing, promoting noise cancellation. This strategy was shown to provide more than 3 dB of OSPL noise reduction inside the cabin on co-rotating propellers, whereas propellers in-phase appeared the best operating option for the counter-rotating top-in layout.

The phenomenon of cavitation is of great importance when ship propellers and rudders are considered, as it can often be the cause of vibrations, noise, reduced efficiency and even erosion in some instances. The underlying fracture mechanisms of erosion, however, have not been fully understood yet. As such, this study aims to expand our knowledge regarding the fracture mechanisms of common shipbuilding alloys and explore whether cavitation erosion can be monitored, by using the relevant quantitative and qualitative data. As such, an experimental test rig was built, based on the induction of cavitation by ultrasonic means, in order for a series of tests, including mass loss and acoustic emission measurements as well as microscopic observations to be conducted. Due to the interest of BAE Systems, a number of protective coatings were also examined under an analogous context. Specimens were initially exposed to ultrasonically induced cavitation under identical experimental conditions. Mass loss was periodically measured thus materials were categorized in that respect while the positive effect of cathodic protection on the resulting erosion was confirmed. Examination through optical and scanning electron microscopes was also conducted thus the fracture mechanisms and macroscopic characteristics of cavitation erosion were identified, for each of the examined materials. Results showed that, erosion initiates through plastic deformation (orange peeling) before proceeding into ductile and brittle, due to work hardening, fracture, whereas the extent and crack propagation characteristics of each phase, depend on the material’s mechanical properties and crystalline structure. Acoustic emissions were also examined, with the aim of, characterizing the materials and potentially be utilized for erosion monitoring. Upon the successful establishment of acoustic thresholds for cavitation erosion, in the case of small specimens, a small model rudder was also examined under an analogous context, although in that instance, cavitation localization was also considered, through a triangulation source location technique. In that instance, cavitation induced erosion, was effectively monitored and characterized both in terms of intensity and location. A model rudder twice as large as the small one was also examined in order for any possible scale effects to be identified. Cavitation induced erosion, was again effectively monitored, both in terms of intensity and location, although results indicated that the method should be optimized, with respect to the parameter of size. As such, the future researcher could further promote the evolvement of the aforementioned ship rudder monitoring system, by means of optimizing the analytical procedures in order to overcome any possible scale effects, further adapting the characteristics of the system to match the size of the objects to be monitored and eventually lead to the full – scale application of the system. The conduction of sea trials would also be of great benefit and importance towards the direction of forming a solid cavitation erosion monitoring system.

This thesis presents evidence on the ability of grid-based, Computational Fluid Dynamics methods based on the Unsteady Reynolds Averaged Navier-Stokes equations to accurately predict axial flight performance of rotors with modest computer resources. Three well-studied blades, the B0-105, S-76, and PSP main rotor blades, are used and results are compared with experimental data. Likewise, performance analyses of the JORP propeller and XV-15 tiltrotor blades are carried out, respectively, aiming to validate the employed CFD method for such relevant flows. Validation of the HMB3 CFD solver for complete tiltrotors is also presented. The aim is to assess the capability of the present CFD method in predicting tiltrotor airloads at different flight configurations. In this regard, three representative cases of the ERICA tiltrotor were selected, corresponding to aeroplane, transition corridor, and helicopter modes, covering most modes of tiltrotor flight. Aerodynamic optimisation of tiltrotor blades with high-fidelity computational fluid dynamics coupled with a discrete adjoint method is also carried out. This work shows how the main blade shape parameters influence the optimal performance of the tiltrotor in helicopter and aeroplane modes, and how a compromise blade shape can increase the overall tiltrotor performance. Finally, the implementation and validation of an efficient, high-order, finite-volume scheme (up to 4th-order of spatial accuracy) in the HMB3 CFD solver is presented. The scheme shows a higher level of accuracy if compared with the standard-MUSCL, and 4th-order accuracy was achieved on Cartesian grids. Furthermore, a significantly high spectral resolution (dispersion and dissipation) of the new scheme is observed. Two-and three-dimensional test cases were considered to demonstrate the new formulation. Results of the steady flow around the 7AD, S-76, JORP propeller, and XV-15 blades showed a better preservation of the vorticity and higher resolution of the vortical structures compared with the standard MUSCL solution. The method was also demonstrated for three-dimensional unsteady flows using overset and moving grid computations for the UH-60A rotor in forward flight and the ERICA tiltrotor in aeroplane mode. For medium grids, the new high-order scheme adds CPU and memory overheads of 22% and 23%, respectively. The parallel performance of the scheme is fair but can be further improved.

This thesis addresses the problem of controlling the unsteady flow separation over an aerofoil using plasma actuators, with the aim of improving the performance of fluid systems through the use of robust feedback controllers. Despite the complexity of the dynamics of interest, it is shown how the problem of controlling flow separation can be successfully formulated and solved as a simple output regulation problem. First, a novel control-oriented reduced-order model for nonlinear systems evolving on attractors is obtained. Its application to the incompressible Navier-Stokes equations is proposed, in order to obtain a linear reduced-order model (whose state variables have a clear and consistent physical meaning) of the complex flow/actuator dynamics. On the basis of the proposed model, a new robust multivariable feedback control algorithm for flow separation suppression is designed, using real-time velocity measurements, which are available in realistic applications. The presented control scheme is tested in both Single-Input-Single-Output (SISO) and Multi-Input-Multi-Output (MIMO) configurations, thus allowing for optimising the closed-loop system, with the aim of selecting suitable numbers and positions of the actuator/sensor pairs along the aerofoil, as well as desired references for the real-time measurements, according to the specific application (e.g., flow separation suppression, mixing enhancement etc.). Accurate numerical simulations of incompressible flows around both 2D aerofoils and 3D wings are performed in order to optimise the closed-loop system and illustrate the effectiveness of the proposed approach in the presence of complex dynamics that are neglected at the design stage. Robust performances, with respect to both parameter variations (e.g. geometry of the domain and Reynolds number) and model uncertainties, are demonstrated. The designed controller is able to effectively suppress the flow separation along the aerofoil, as well as the shedding vortices, thus yielding both a reduction of the drag and an increase of the lift. This allows for stall avoidance and increased efficiency.

Cavity flow induces strong flow oscillations, which increase noise, drag, vibration, and structural fatigue. This type of flow impacts a wide range of low speed applications, such as aircraft wheel wells, ground transportations, and pipelines. The objective of the current study is to examine the reverse flow interaction inside the cavity, which has a significant impact on the cavity flow oscillations. The study also investigates the impact of steady jets with different-configurations on the time-average field and the oscillations of the cavity separated shear layer. The purpose of the steady jets is suppressing the oscillations of the cavity separated shear layer. The experiments were performed for an open cavity with L/D = 4 at Reθ between 1.28×103 to 4.37×103. The steady jets were applied with different: momentum fluxes (J = 0.11 kg/m.s2,0.44 kg/m.s2 and 0.96 kg/m.s2), slot configurations (sharp edge and coanda), and blowing locations (blowing from the cavity leading and trailing edges). The data were acquired using qualitative (surface oil flow visualisation) and quantitative (hot-wire anemometry, laser Doppler anemometry, particle image velocimetry, and pressure measurements) flow diagnostics techniques. The study found that a low-frequency instability dominates the velocity spectra of the cavity separated shear layer. This instability decreases with increasing Reθ and is related to the reverse flow interaction. This interaction takes place when the reverse flow influences the sensitive separation point of the cavity separated shear layer. As a result, a large amplitude flapping wave is generated and propagates downstream of the cavity separated shear. It was also revealed that increasing J for the leading and trailing edges blowing enhances the reverse flow interaction and increases the broadband level of the unsteady wall pressure spectra. Thus, these types of jet blowing are not suitable for controlling the oscillations of the cavity separated shear layer.

Automotive manufacturers are receiving pressure from customers and regulators to reduce emissions. Reducing the weight of the vehicle through the use of carbon fibre is seen as one of these mechanisms. The challenge is to develop suitable manufacturing processes that can offer appropriate cycle times to meet demand and deliver materials with adequate mechanical properties for structural applications. Compression moulding of discontinuous fibre moulding compounds with local continuous fibre inserts provide better production rates and part complexity compared to the autoclave components and higher performances than injection moulding. However, combining a unidirectional carbon fibre (UD) material with a random short fibre orientation sheet moulding compound (SMC) that flows heterogeneously will lead to degradation in the properties of the continuous reinforcement. This work aims to demonstrate a hybrid of continuous and discontinuous fibre compounds in a single moulding operation with increased stiffness and determine if the surface distortion of the reinforcement can be used to predict local stiffness. A benchmarking study was carried out with UD and the SMC followed by hybridisation. This was non-destructively tested for flexural moduli providing a localised map of stiffness which was compared with a theoretical value. This work demonstrated that simply placing unidirectional (UD) prepreg with the SMC caused significant distortion and migration of the reinforcement in a one-dimensional flow scenario. Resin tended to bleed out of the hybrid reinforcement, causing a resin rich area at the UD ply drop off point. This resin bleed was more prominent at the ends of the UD fibres. The resin system in the UD was staged by partially curing it to a controlled level through the measurement of the storage modulus, and showed that flow could be dramatically reduced. This was determined by rheology and inter-laminar shear tests to measure material degradation from staging to improve flow control. It was found that for flow control of the reinforcement staging beyond gelation was required. The inter-laminar shear strength of UD is significantly higher than the SMC, and found that even with 50% staging properties were still higher. Where there were high levels of flow resistance in compression moulding, staged hybrids resulted in to two moulding defects; a dry region on the SMC under the reinforcement and rippling outside the reinforcement, which reduced the stiffness by nearly 50% in the affected areas. Staging accompanied with charge layout design of the UD to 902/0 showed markedly reduced flow in one, two and three dimensional scenarios, almost completely resisting the flow of the SMC. In the 2D flow scenario where the SMC charge coverage was 60% compared to the manufacturers’ recommended 80%, flow was limited to 3% and the stiffness could be locally predicted to an accuracy of 16%. By controlling the level of staging and careful consideration of the charge design, hybrid components can be manufactured repeatedly with increased accuracy in stiffness prediction and demonstrated an improved flexural strength and modulus increase of >44%, increasing the potential use to a wider range of complex geometry structural applications.

With the growth of electrical power onboard aircraft, the interaction between the electrical systems and the engine will become significant. Moreover, since the drivetrain has a flexible shaft, higher load connections can excite torsional vibrations on the aircraft drivetrain. These vibrations can break the shaft if the torque induced is higher than the designed value, or reduce its lifespan if the excitation is constant. To avoid these problems, the electromechanical interaction between the electrical power system and the drivetrain must be evaluated. Past studies have identified the electromechanical interaction and introduced experimental setups that allow its study. However, strategies to reduce the excitation of the torsional vibrations have not been presented. This thesis aims to analyse the electromechanical interaction in aircraft systems and develop an advanced electrical power management system (PMS) to mitigate its effects. The PMS introduces strategies based on the load timing requirements, which are built on the open loop Posicast compensator. The strategies referred as Single Level Multi-edge Switching Loads (SLME), Multilevel Loading (MLL), and Multi-load Single Level Multi-edge Switching Loads (MSLME) are applied to different loads, such as pulsating loads, ice protection system, and time-critical loads, such as the control surfaces. The Posicast based strategies, eliminate the torsional vibrations after a switching event, by the addition of zeros that cancel the poles of the system. For this reason, the knowledge of the natural frequencies of the mechanical system is necessary. Experimentally, the system parameters are obtained through Fourier analysis of the step response and the strategies are applied. A robust analysis of the strategies allows the establishment of the range of uncertainty on the frequencies that allow the proper operation of the strategies. Simulation and experimental results show that the torsional vibrations can be reduced to values close to zero by the application of the strategy. Therefore, the PMS mitigates the electromechanical interaction between the electrical power system and the aircraft drivetrain.

Advanced Receiver Autonomous Integrity Monitoring (ARAIM) is a new Aircraft Based Augmentation System (ABAS) technique, firstly presented in the two reports of the GNSS Evolutionary Architecture Study (GEAS). The ARAIM technique offers the opportunity to enable GNSS receivers to serve as a primary means of navigation, worldwide, for precision approach down to LPV-200 operation, while at the same time potentially reducing the support which has to be provided by Ground and Satellite Based Augmented Systems (GBAS and SBAS). Previous work analysed ARAIM performance, clearly showing the potential of this new architectures to provide the Required Navigation Performance down to LPV 200 approach procedures. However, almost all of the studies have been performed with respect to fixed points on a grid on the Earth’s surface, with full view of the sky, evaluating ARAIM performance from a geometrical point of view and using nominal performance in simulated scenarios which last several days. Though, the operational configuration was not examined; attitude changes from manoeuvres, obscuration by the aircraft body and shadowing from the surrounding environment could all affect the incoming signal from the GNSS constellations, leading to configurations that could adversely affect the real performance. In this research, ARAIM performances in simulated operational configurations are presented. Four different algorithms were developed that integrate the ARAIM technique for performance prediction analysis. These algorithms could usefully be implemented: • In the design of instrument approach procedures. The algorithms could be used to improve the procedure of the development of new instrument approaches, reducing time, effort and costs. • In the aircraft Flight Management Systems. The algorithms could support the pilots in the pre-flight briefing, highlighting possible integrity outage in advance and allowing them to select a different approach or making them aware of the need to utilise additional positioning systems. Increased awareness and better pre-flight planning could ultimately improve the safety of flights and contribute to the safe introduction of GNSS as a viable positioning method for instrument approach. The results showed that the aircraft attitude and the surrounding environment affect the performance of the ARAIM algorithm; each satellite lost generates a peak in the performance parameters that depends on the total number of satellites in view, their relative geometry and on the number of satellites lost at the same time. The main outcome of this research is the identification that the ideal scenario would be to have a tri-constellation system that provides at the same time high redundancy, reliability and increased safety margin.

Daylight changes from moment to moment, in brightness, colour and direction under changing bright daylight, in-vehicle displays can become unreadable due to washout or glare, causing driver distraction or masking safety critical information. With an increasing number of vehicle systems being controlled through a centralised display, the legibility of automotive displays under ambient lighting conditions has become an important consideration for engineers in terms of perceived quality, safety and driver distraction. Due to the dynamic nature of the sky, testing under natural daylight would not give the control required for meaningful measurements. Therefore, the challenge for the automotive industry is to standardise the simulation of illumination for performing assessments and to make the process controlled, repeatable and comparable to real daylight situations. The main objective of this project is to propose a method for recreating a daylight-comparable lighting environment to enable the evaluation of vehicle interiors under high ambient lighting conditions and to propose best-practice for illumination used in legibility evaluation for design and validation activities. This is achieved with a measurement and simulation approach, to evaluate current procedures and determine the gap between real world, simulation and lab-based assessments, and bring them closer to the real-world. There are two main outputs from this project; a comparative simulation study which verifies digital tools for use by JLR in display design and evaluation activities, and the recommendation to align physical and digital methods to move evaluations earlier in the new product development process. A concept has been included to enable controlled measurements as part of physical evaluations, as are the critical factors required for a repeatable physical environment for physical testing as the basis of continuous improvement of digital simulations.

Vehicle electrification is a technology pathway being adopted by original equipment manufacturers (OEMs) to either reduce or eliminate tailpipe emissions. However, electric vehicles (EV’s) that employ a rechargeable energy storage system (RESS) still face significant barriers within the marketplace when compared to incumbent internal combustion engine (ICE) vehicle technology. One of these barriers is ensuring that the RESS lasts the life of the product or maintains customer satisfactory performance over a warranted life (such as 10 years or 100,000 miles of customer usage). There has been comparably little published research critically examining the effect of vibration on high voltage (HV) batteries within battery electric vehicles (BEV) and hybrid electric vehicles (HEV). Subsequently the effects of vibration on RESS components and subsystems are potentially a major cause of in market durability failures. The following thesis presents the findings from an International Engineering Doctorate (EngD (int.)) investigating factors influencing the vibration durability of HV batteries and components. This research programme has the objective of providing the underpinning knowledge that allows manufacturers to improve the mechanical durability and performance of EV battery assemblies with respect to vibration. This objective has been achieved through several novel studies within three primary areas of investigation. Firstly, the research focused on defining the “in-service” vibration environment of BEV components and assemblies through the analysis of vibration measurements from contemporary BEVs. This study was the first to synthesise a vibration profile that is representative of a durability life of 100,000 miles of UK customer usage from multiple real world BEV measurements. The presented profile can be employed by academics and engineers to underpin future vibration durability assessments of BEV battery components. The second avenue of investigation was to characterise the natural vibration and modal response of EV components and assemblies. This was to determine their susceptibility to vibration excitation, as identified from measurements of the in-service environment. It was also the first of its kind to fully characterise the natural vibration characteristics and mode shapes of lithium-ion pouch cells via modal analysis techniques. The final objective was to determine the durability behaviour of EV components and assemblies, by subjecting them to vibration, via state of the art single and multi-axis test techniques, which were the equivalent of a typical vehicle life (10 years) or customer mileage (100,000 miles). As well as defining the degradation characteristics of a contemporary BEV module and multiple EV cells, the impact of packaging variation and state of charge (SOC) on cell ageing was also determined. In conclusion, this research thesis defines innovative testing techniques and characterisation data, which can be employed by engineers to predict the warranty performance, with respect to the effects of in-service vibration, of future EV battery assemblies.