Within the context of preliminary aerodynamic design with low order models, the methods have to meet requirements for rapid evaluations, accuracy and sometimes large design space bounds. This can be further compounded by the need to use geometric and aerodynamic degrees of freedom to build generalised models with enough flexibility across the design space. For transonic applications, this can be challenging due to the non-linearity of these flow regimes. This paper presents a nacelle design method with an artificial neural network (ANN) for preliminary aerodynamic design. The ANN uses six intuitive nacelle geometric design variables and the two key aerodynamic properties of Mach number and massflow capture ratio. The method was initially validated with an independent dataset in which the prediction error for the nacelle drag was 2.9% across the bounds of the metamodel. The ANN was also used for multi-point, multi-objective optimisation studies. Relative to computationally expensive CFD-based optimisations, it is demonstrated that the surrogate-based approach with ANN identifies similar nacelle shapes and drag changes across a design space that covers conventional and future civil aero-engine nacelles. The proposed method is an enabling and fast approach for preliminary nacelle design studies.

It is envisaged that future civil aero-engines will operate with ultra-high bypass ratios to reduce the specific fuel consumption. To achieve the expected benefits from the new engine cycles, these new powerplants may mount compact nacelles. For these new configurations the aerodynamic coupling between the powerplant and the airframe may increase. For this reason, it is required to quantify and further understand the effects of aircraft integration for compact aero-engine nacelles. This study provides an insight of the changes in flow aerodynamics as well as quantification of the most relevant performance metrics of the powerplant, airframe and the combined aircraft system across a range of different installation positions. Relative to a conventional architecture, there is an aerodynamic benefit in net vehicle force of about 1.2% for a compact powerplant when installed in forward positions. This is the same improvement that was identified when the aero-engine nacelles were in isolation. However, for close-coupled installation positions, the aerodynamic benefit in net vehicle force erodes to 0.44% due to the larger effects of aircraft integration on compact nacelles.

The next generation of civil large aero-engines will employ greater bypass ratios compared with contemporary architectures. This results in higher exchange rates between exhaust performance and specific fuel consumption (SFC). Concurrently, the aerodynamic design of the exhaust is expected to play a key role in the success of future turbofans. This paper presents the development of a computational framework for the aerodynamic design of separate-jet exhaust systems for civil aero-engines. A mathematical approach is synthesised based on class-shape transformation (CST) functions for the parametric geometry definition of gas-turbine exhaust components such as annular ducts and nozzles. This geometry formulation is coupled with an automated viscous and compressible flow solution method and a cost-effective design space exploration (DSE) approach. The framework is deployed to optimise the performance of a separate-jet exhaust for very-high-bypass ratio (VHBR) turbofan engine. The optimisations carried out suggest the potential to increase the engine’s net propulsive force compared with a baseline architecture, through optimum exhaust re-design. The proposed method is able to identify and alleviate adverse flow-features that may deteriorate the aerodynamic behaviour of the exhaust system.

Shock-wave/turbulent boundary-layer interactions (SWTBLIs) with separation are known to be inherently unsteady but their physical mechanisms are still not totally understood. An experimental investigation has been performed in a supersonic wind tunnel at a freestream flow Mach number of 2·42. The interaction between a shock wave created by a shock generator (α = 3°, α = 9°, α = 13° and α = 15° deflection angles) and a turbulent boundary layer with thickness δ = 5mm has been studied. High-speed Schlieren visualisations have been obtained and used to measure shock wave unsteadiness by means of digital image processing. In the interactions with separation, the reflected shock’s unsteadiness has been in the order of 102Hz. High-speed wall pressure measurements have also been obtained with fast-response micro-transducers along the interactions. Most of the energy of the incoming turbulent boundary layer is broadband and at high frequencies (>104Hz). An addition of low-frequency (<104Hz) fluctuation energy is found at separation. Along the interaction region, the shock impingement results in an amplification of fluctuation energy due to the increase in pressure. Under the main recirculation region core there is only an increase in high frequency energy (>104Hz). Amplification of lower frequency fluctuation energy (>103Hz) is also observed close to the separation and reattachment regions.

The ground vortices generated by an intake under both headwind and crosswind configurations have been investigated using computational and experimental approaches. The flow field of a scale-model intake was experimentally studied using stereoscopic particle image velocimetry to measure the ground vortex in conjunction with induct total pressure measurements for the internal flow. The computational predictions were performed using an unsteady Reynolds averaged Navier-Stokes approach. The experimental results show that under crosswind conditions a single ground vortex forms which becomes stronger as the crossflow velocity is increased. Under headwind conditions the measured ground vortex strength initially increases with freestream velocity before it reaches a local maximum and then reduces thereafter. The computations also exhibit the same characteristics and show good agreement with the measurements for some configurations. Based on the predictions, the complex flow field topology is investigated and a detailed flow model of the vortex flow field under crosswind conditions is proposed.

A Parabolised Navier-Stokes (PNS) flow solver is used to predict the aerodynamic heating on the surface of a hypersonic vehicle. This case study highlights some of the main heat flux sensitivies to various conditions for a full-scale vehicle and illustrates the use of different complimentary methods in assessing the heat load for a realistic application. Different flight phases of the vehicle are considered, with freestream conditions from Mach 4 to Mach 8 across a range of altitudes. Both laminar and turbulent flows are studied, together with the effect of the isothermal wall temperature, boundary-layer transition location and body incidence. The effect of the Spalart-Allmaras and Baldwin-Lomax turbulent models on the heat transfer distributions is assessed. A rigorous assessment of the computations is conducted through both iterative and grid convergence studies and a supporting experimental investigation is performed on a 1/20th scale model of the vehicle’s forebody for the validation of the numerical results. Good agreement is found between the PNS predictions, measurements and empirical methods for the vehicle forebody. The present PNS approach is shown to provide useful predictions of the heat transfer over the axisymmetric vehicle body. A highly complex flow field is predicted in the fin-body-fin region at the rear of the vehicle characterised by strong interference effects which limit the predictions over this region to a predominately qualitative level.

Nanosized Co-doped ZnO samples were synthesized using an ultrasonic spray assisted chemical vapour deposition method. Microstructural and magnetic properties of these samples were studied. The room-temperature ferromagnetism was observed in the Co-doped ZnO. Also, x-ray analysis revealed a wurtzite ZnO structure with a small change of the lattice constants due to the doping of Co in ZnO. Raman spectroscopy of the Co-doped ZnO films indicated direct substitution of Co. Scanning electron microscopy showed nanostructured Co-doped ZnO with a ring or cup shape. Transmission electron microscopy analysis revealed nano grains within the rings of an average diameter of around 10 nm. Both energy dispersive spectroscopy and energy-filtered transmission electron microscopy indicated a uniform distribution of Co.

ZnO, which exhibits a direct bandgap of 3.37 eV at room temperature with a large exciton binding energy of 60 meV,is of considerable technological importance because of its potential use in short-wavelength devices, such as ultraviolet (UV) light-emitting diodes and laser diodes. The fabrication and application of 1-D ZnO nanostructures has attracted considerable interest in recent years. In this work, we produced single crystal nanowires of zinc oxide using a novel self-seeded growth using ultrasonic spray assisted chemical vapour deposition, in which a nanocrystalline seed layer was first deposited onto a glass substrate and the nanowires subsequently grown using a different precursor concentration and substrate temperature. The diameter of the nanowires is in the range of 20-80 nm and the length of the wires is as long as 10 μm. The single crystal nature of the nanowires was revealed by high resolution transmission electron microscopy. The formation of liquid droplets due to the reducing atmosphere and the higher temperature during the nanowire growth was found to be the key step of the ZnO nanowire formation.

The primary objective of this work is to determine the detailed characteristics of the flow features induced in a boundary layer by suction through laminar flow control (LFC) perforations. An additional goal is to validate a predictive method for generic LFC suction surfaces and to apply this technique to typical flight condition configurations. Fundamental insights into the flow physics of LFC suction surfaces are obtained from a unique series of high-resolution three-component laser Doppler velocimetry (LDV) flow field measurements. The flow fields induced by isolated super-scale perforations under low-speed conditions are mapped and found to be strongly three-dimensional and profoundly different from the idealized concept of continuously distributed suction. Over a range of sub- and super-critical suction flow rates a variety of suction-dependent complex flow features are identified, including a pair of contra-rotating streamwise vortices, multiple co-rotating streamwise vortices, spanwise variations of the mean flow and inherently unstable boundary layer profiles. The measurements reveal that suction-induced transition commences with an instability of these attached vortices, resulting in the development of a pair of turbulent wedges downstream of the perforation. A finite-volume Navier–Stokes method is validated by simulating a variety of low-speed experiments and comparisons are made between the LDV measurements and the predicted flow field. The computational technique reproduces all of the observed flow features, although it slightly under-predicts their magnitude and extent. By analysing the predicted flow fields the mechanism for the formation of the trailing vortex pair is established. Earlier flow visualization experiments, which exhibited vortex shedding, are also simulated by solving the time-dependent governing equations and it is found that the principal unsteady flow features are captured. Despite the challenge posed to the computational method by the diverse range of flow phenomena induced by discrete suction, the predictions provide good agreement with the measurements and observations. The computational tool is subsequently applied to predict the flow fields of single and multiple rows of actual-scale micro-perforations under low-speed and typical transonic flight conditions. A range of suction-induced flow features are predicted and a variety of distinct flow modes are identified. The low-speed critical suction limits are also measured and a design criterion, based on the sucked streamtube characteristics, is established. The basis of this critical suction criterion is also validated for transonic flight configurations.

To evaluate whether the lines occasionally detected on clinical magnetic resonance (MR) images are genuine hippocampal layers, a formalin fixed hippocampal specimen was scanned using T2 weighted sequences at 7 Tesla (voxel dimensions 0.064×0.064×1 mm) and at 1.5 Tesla (voxel dimensions: 0.156×0.156×1 mm) and compared with the results of histological examination. In addition, a healthy volunteer was scanned with a T2 weighted sequence at 1.5 Tesla (voxel dimensions: 0.469×0.469×2 mm). On 7 Tesla images hippocampal layers and the granule cell layer of the dentate were visible. On 1.5 Tesla images of the specimen, the hippocampal layers were again identified, but the granule cell layer of the dentate was not detectable. On 1.5 Tesla images of the hippocampus in vivo, 3 layers could be distinguished in the hippocampus on some slices. These mainly represented the alveus, pyramidal cell layer and stratum radiatum. A dark line consisting of a few pixels possibly represented the dentate gyrus. Our results show that the lines occasionally detected on clinical MR images are likely to be real hippocampal layers. However, the resolution currently used in clinical imaging (typically 0.469×0.469×2 mm or lower) is not sufficient for the detection of all hippocampal layers. For the reliable detection of all hippocampal layers on MR images an increase by a factor of approximately 20 would be necessary.

The structural changes and magnetoresistance (MR) properties of as-grown and post-annealed La0.7Ca0.3MnO3 films were investigated by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The data for the films were compared to that for bulk La0.7Ca0.3MnO3 post-annealed under the same conditions. The main structure of the as-grown films was face-centered pseudo-cubic with a doubled perovskite unit cell, of size ∼2ap × ∼2ap × 2ap, where ap is the single perovskite parameter. The phase showed a cube-on-cube epitaxy with the underlying LaAlO3 substrate. Upon annealing to a saturation point, a minor primitive pseudo-tetragonal structure evolved, of cell parameters . A total of four possible orientations of the two structures was observed by TEM, comprised of one orientation of the ∼ 2ap × ∼ 2ap × ∼ 2ap cell, i.e., the cube-on-cube epitaxy, giving rise to (00l) peaks in x-ray, and three orientations of the cell, giving rise to a single (00l)/(hk0) peak in x-ray. The bulk La0.7Ca0.3MnO3 sample also contains the × structure. The difference between the bulk and the film and the effects of annealing on films can be ascribed to the influence of strain between the film and substate, induced by lattice mismatch.

Thin films of colossal magnetoresistance material La0.7Ca0.3MnO3 were implanted with different fluence 200keV Cr ions. Resistivity measurements in zero and applied fields of up to 8T were made in order to determine the effects of the implanted magnetic ions on the magnetoresistance (MR). As the Cr fluence was increased, the resistivity increased and the metal-insulator transition (MI) temperature was suppressed to values below the experimentally accessible temperature range as a result of oxygen loss and the creation of defects. However, for the highest fluence of 5×1015 ions/cm2, a re-entrant metal-insulator type transition was observed. Furthermore a significant improvement in the low field MR was observed for fields less than 500mT. These results are interpreted in terms of substitution of Cr ions onto Mn sites and the creation of a magnetically inhomogeneous material and the influence of oxygen deficiency.