bluuebunny/crossref_metadata_2025 huggingface dataset:
Civil aviation and the environment – the next frontier for the aerodynamicist
Authors: Green J. E.
Published: February 2016

In the coming century, the impact of air travel on the environment will become an increasingly powerful influence on aircraft design. Unless the impact per passenger kilometre can be reduced substantially relative to today’s levels, environmental factors will increasingly limit the expansion of air travel and the social benefits that it brings. The three main impacts are noise, air pollution around airports and changes to atmospheric composition and climate as a result of aircraft emissions at altitude. The lecture will review the work done within the Air Travel – greener by Design programme to assess the technological, design and operational possibilities for reducing these impacts. The main aeronautical disciplines all have something to contribute but it is in aerodynamics that the greatest opportunities appear to lie. If these opportunities are pursued, the aircraft in production in 2050 could be very different from those of 2005. It is for the aerodynamicists, supported by the structures and systems engineers and the materials scientists, to make the case for a radical leap.
Civil aircraft design priorities: air quality? climate change? noise?
Authors: Brooker P.
Published: February 2016

A variety of related questions is posed. Are the right priorities for future aircraft design being set now? New civil aircraft types could be ‘silent’, i.e. make much less noise than current types. They could be ‘green’, i.e. safeguard the environment. Is silent as important as Green? The crucial answer is that future aircraft design should focus on substantial reductions on climate change impact. The air quality targets proposed by the ‘Sustainable Aviation’ initiative appear very ambitious: they should be pursued only to the extent that they do not affect improved fuel efficiency and reduced climate-changing emissions. Good progress has already been made on the aircraft noise targets proposed by the ‘Sustainable Aviation’ initiative, but again they should be pursued only to the extent that they do not affect improved fuel efficiency and reduced climate-changing emissions. The financial case for designing to reduce aircraft noise in order to deliver novel financial benefits, e.g. increase airport flights at night and/or relocate airports, is weak.
Greener manufacturing, maintenance and disposal – towards the Acare targets
Authors: Lee J. J.
Published: February 2016

This paper looks at how the aerospace industry can achieve the Acare goal of greener manufacturing, maintenance and disposal. It looks further than merely reducing waste and eliminating hazardous materials and processes and suggests that the organisational structure of the industry will play an important role in facilitating a move towards such a goal. Greater co-operation or integration within the industry at all stages of the product life cycle chain is a fundamental requirement as individual companies run a risk of increasing the total environmental burdens if they concentrate solely on reducing their own impacts without considering the effect a change they make may have on other companies. The use of comprehensive environmental supply chain management systems and end of life plans can smooth the implementation of extended product responsibility and accelerate the benefits of greener manufacturing, maintenance and disposal.
Impact of solar storms on high altitude long endurance unmanned aircraft and airship design and operations
Authors: Newcome L. R.
Published: February 2016

This paper applies existing information on solar storms to unmanned aviation; no new research data is presented. The purpose of this paper is to alert the unmanned aviation community to the potential hazards posed by solar storms, to familiarise it with the effects of solar storms and how to mitigate them, and to encourage research on solar storm effects on high altitude long endurance (HALE) aircraft and airship design and operations. As unmanned aircraft and airships move increasingly into high altitude (50,000+ft), endurance (24+ hr) roles, they will become vulnerable to the effects of space weather, specifically that of solar storms. Although solar storms are commonly associated with their impact on satellites, they affect the routing and timing of airline flights flying for six to eight hours at 30,000 to 40,000ft. Operating twice as high and with flight times twice as long (or longer) than those of airliners, HALE aircraft and airships occupy a middle zone of vulnerability, being more so than airliners but less so than satellites. A key difference however is that satellites are designed for space weather, whereas some current HALE vehicles are not. The paper concludes that unmanned HALE aircraft and airships can be one to three orders of magnitude more vulnerable to solar storms than a trans-Pacific airliner.
A comparative study of two UCAV type wing planforms — performance and stability considerations
Authors: Nangia R. K. , Palmer M. E.
Published: February 2016

Currently there is a revival of interest in flying wings for military (and civil) use. The military context has arisen from the future ‘stealthy’ high altitude long endurance (HALE) and unmanned combat air vehicles (UCAV) aircraft. Questions on aerodynamics, control and structural efficiency arise. Compared with conventional wing/tail arrangements, flying wings have a special set of very different constraints. These are mentioned.

Without a trim surface, the constraints on the wing pitching moment dictate the design camber and twist. Control power requirements can be high because of effectively short moment arms. The camber and twist are strongly dependent on trim stability margins. This aspect needs to be understood in detail when comparing different types of planforms.

This paper covers three inter-related aspects – a wing design method, the suitability of solvers used with the method and a comparative study of two, typical UCAV planforms. This is inspired by the need to understand a variety of wings (in the public domain) that are, at first sight, aimed at similar missions. The main emphasis has been on developing and understanding cruise design camber and twist with Cm constraints of stable, neutral and unstable static margins. Spanwise lift and drag loadings have also been presented. Camber design has been via attained thrust methods and a modal approach. It is shown that starting from basic information such as the planform, we are able to predict the anticipated performance with sufficient confidence for comparative assessments of published project data.

Further work is proposed in several areas.
Wing tip vortex control using synthetic jets
Authors: Margaris P. , Gursul I.
Published: February 2016

An experimental investigation was conducted to study the effect of synthetic jet (oscillatory, zero net mass flow jet) blowing near the wing tip, as a means of diffusing the trailing vortex. Velocity measurements were taken, using a Particle Image Velocimetry system, around the tip and in the near wake of a rectangular wing, which was equipped with several blowing slots. The effect of the synthetic jet was compared to that of a continuous jet blowing from the same configurations. The results show that the use of synthetic jet blowing is generally beneficial in diffusing the trailing vortex and comparable to the use of continuous jet. The effect was more pronounced for the highest blowing coefficient used. The driving frequency of the jet did not generally prove to be a significant parameter. Finally, the instantaneous and the phase-locked velocity measurements helped explain the different mechanisms employed by the continuous and synthetic jets in diffusing the trailing vortex.
A method for predicting the rate and effect of approach to the stall of a microlight aeroplane
Authors: Gratton G. B.
Published: February 2016

The stall and immediately post-stall behaviour of a microlight aeroplane are shown to be a function of the deceleration rate prior to the stall; therefore, it is necessary to use a representative deceleration rate when determining the acceptability of stall and post-stall handling qualities. This research has found means by which the range of deceleration rates likely to be seen in a particular type can be estimated, so that flight test programmes can ensure these rates are included, and thus aircraft are confirmed to have acceptable stalling characteristics. Recommendations are made towards the use of this research for all aircraft type, and of further work which might usefully be carried out.
Integration of friction stir welding into a multi-disciplinary aerospace design framework
Authors: van der Laan A. H. , Curran R. , van Tooren M. J. L. , Ritchie C.
Published: February 2016

Multidisciplinary design and innovative highly automated manufacturing methods are increasingly important to today’s aircraft industry: multidis-ciplinary design because it reduces lead-time and results in a better design, and automated manufacturing methods because they are more capable and reduce manufacturing cost. In this paper a cost estimation model is presented that integrates the manufacturing cost of friction stir welded connections within a multidisciplinary design decision tool. Due to the fact that friction stir welding is a new manufacturing method, the cost estimation model is based on the actual process physics, meaning what the process looks like in terms of processing speeds and characteristics. As an integral part of a multidisciplinary design framework, the developed cost estimation model contributes to a design support tool that assesses not only manufacturing but also structural and aerodynamic issues. It is shown that the cost model developed can be integrated into this more holistic design process support architecture. The predicted costs are accurate to the historical data and allow tradeoff of manufacturing and economic considerations within the context of the multidisciplinary design tool. The tradeoff capability is highlighted through a presented case study that compares the friction stir welding process as an alternative solution to more tradition riveting. Most importantly, this results in a quantitative tradeoff between two processes that shows the manufacturing cycle time of friction stir welding to be reduced by 60% and the recurring assembly cost by 20%.
Decoupled controller for mixed exhausts turbofan engine
Authors: Nada T. R.
Published: February 2016

This paper points out the capabilities of fully decoupled fuzzy controller which introduces simple design approach to deal with the coupling effects in controlling two spools, mixed exhausts turbofan engines. The decoupling is performed through proper selection of input parameters to the controller. Digital nonlinear engine/control system simulation is used to construct the fuzzy rules depending on simple logic. The performance of this controller is compared with that of an optimal controller representing efficient classical and conventional techniques. The decoupled fuzzy control system produces favorable transient strategies that other conventional controllers can not attempt due to its inherent proportionality characteristics. It displays improvements in surge margin for both fan and compressor, and temperature margin with almost similar response time during acceleration. Also, the proposed controller has the capabilities to increase the response speed during deceleration independently from acceleration transient.
Optical imaging techniques for hypersonic
impulse facilities
Authors: McIntyre T. J. , Kleine H. , Houwing A. F. P.
Published: February 2016

The application of optical imaging techniques to
hypersonic facilities is discussed and examples of
experimental measurements are provided. Traditional
Schlieren and shadowgraph techniques still remain as
inexpensive and easy to use flow visualisation
techniques. With the advent of faster cameras, these
methods are becoming increasingly important for
time-resolved high-speed imaging. Interferometry’s
quantitative nature is regularly used to obtain
density information about hypersonic flows. Recent
developments have seen an extension of the types of
flows that can be imaged and the measurement of
other flow parameters such as ionisation level.
Planar laser induced fluorescence has been used to
visualise complex flows and to measure such
quantities as temperature and velocity. Future
directions for optical imaging are discussed.
Periodic transonic flow and control
Authors: Raghunathan S. , Early J.M. , Tulita C. , Benard E. , Quest J.
Published: February 2016

The current understanding of periodic transonic flow is reviewed briefly. The effects of boundary-layer transition, non-adiabatic wall conditions and modifications to the aerofoil surface geometry at the shock interactions on periodic transonic flow are discussed. Through the methods presented, it is proposed that the frequency of periodic motion can be predicted with reasonable accuracy, but there are limitations on the prediction of buffet boundaries associated with periodic transonic flows. Several methods have been proposed by which the periodic motion may be virtually eliminated, most relevantly by altering the position of transition fix, contouring the aerofoils surface or adding a porous surface and a cavity in the region of shock interaction. In addition, it has been shown that heat transfer can have a significant effect on buffet.
Morphing skins
Authors: Thill C. , Etches J. , Bond I. , Potter K. , Weaver P.
Published: February 2016

A review of morphing concepts with a strong focus on morphing skins is presented. Morphing technology on aircraft has found increased interest over the last decade because it is likely to enhance performance and efficiency over a wider range of flight conditions. For example, a radical change in configuration, i.e. wing geometry in flight may improve overall flight performance when cruise and dash are important considerations. Although many morphing aircraft concepts have been elaborated only a few deal with the problems relating to a smooth and continuous cover that simultaneously deforms and carries loads. It is found that anisotropic and variable stiffness structures offer potential for shape change and small area increase on aircraft wings. Concepts herein focus on those structures where primary loads are transmitted in the spanwise direction and a morphing function is achieved via chordwise flexibility. To meet desirable shape changes, stiffnesses can either be tailored or actively controlled to guarantee flexibility in the chordwise (or spanwise) direction with tailored actuation forces. Hence, corrugated structures, segmented structures, reinforced elastomers or flexible matrix composite tubes embedded in a low modulus membrane are all possible structures for morphing skins. For large wing area changes a particularly attractive solution could adopt deployable structures as no internal stresses are generated when their surface area is increased.
Genetic optimisation of a neural network damage diagnostic
Authors: Manson G. , Papatheou E. , Worden K.
Published: February 2016

This paper presents an automated optimisation procedure for the feature selection stage of a previously proposed structural health monitoring methodology using a genetic algorithm. The same diagnostic is used in the attempt to progress up the levels of damage detection to location and severity. It was validated experimentally on a Gnat aircraft wing. An artificial neural network is used as a classifier and the work is compared with the previous selection strategy based on engineering judgement.
Monitoring of aircraft landing gear structure
Authors: Schmidt R. K.
Published: February 2016

Landing gear structure is developed predominantly using safe life design criteria. Health monitoring and structural prognosis techniques for landing gear cannot focus on crack detection; techniques for determining input loads and calculating damage or methods for directly measuring material damage must be employed. This paper will discuss Messier-Dowty’s research into structural monitoring over the past several years. Principally, direct damage detection systems and load monitoring systems will be discussed.
Prediction of laminar, transitional and turbulent flow regimes, based on three-equation k-ω turbulence model
Authors: Taghavi-Zenouz R. , Salari M. , Etemadi M.
Published: February 2016

A recently developed transitional model for boundary-layer flows has been examined on a flat plate and the well-known S809 wind turbine blade. Proposed numerical model tries to simulate streamwise fluctuations, induced by freestream turbulence, in pre-transitional boundary-layer flows by introducing an additional transport equation for laminar kinetic energy term. This new approach can be used for modeling of transitional flows which are exposed to both the freestream turbulence intensity and streamwise pressure gradient, which are known as the most dominant factors in occurrence of transition. Computational method of this model is based on the solution of the Reynolds averaged Navier-Stokes (RANS) equations and the eddy-viscosity concept. The model includes three transport equations of laminar kinetic energy, turbulent kinetic energy and dissipation rate frequency. The present model is capable of predicting either natural or bypass transitional mechanisms, which may occur in attached boundary-layer flows. In addition, the model can simulate transition in the separated free shear layers and the subsequent turbulent re-attachment to form a laminar separation bubble. Flat plate was exposed to different freestream turbulence intensities and streamwise pressure gradients. Wind turbine blade was examined under two different Reynolds numbers, with one of them suitable for the occurrence of laminar separation bubbles on its surfaces. To evaluate the performance of this new model in resolving transitional boundary-layer flows, final results have been compared to those obtained through application of conventional turbulence models. Comparison of final results for the flat plate and the S809 aerofoil with available experimental data show very close agreements.
Experimental investigation on spiked body in hypersonic flow
Authors: Kalimuthu R. , Mehta R. C. , Rathakrishnan E.
Published: February 2016

A spike attached to a hemispherical body drastically changes its flowfield and influences aerodynamic drag in a hypersonic flow. It is, therefore, a potential candidate for drag reduction of a future high-speed vehicle. The effect of the spike length, shape, spike nose configuration and angle-of-attack on the reduction of the drag is experimentally studied with use of hypersonic wind-tunnel at Mach 6. The effects of geometrical parameters of the spike and angle-of-attack on the aerodynamic coefficient are analysed using schlieren picture and measuring aerodynamic forces. These experiments show that the aerodisk is superior to the aerospike. The aerodisk of appropriate length, diameter and nose configuration may have the capability for the drag reduction. The inclusion of an aero disk at the leading edge of the spike has an advantage for the drag reduction mechanism if it is at an angle-of-attack, however consideration to be given for increased moment resulting from the spike is required.
Comparison between blade-element models of propellers
Authors: Gur O. , Rosen A.
Published: February 2016

Blade-element models are the most common models for the analysis of propeller aerodynamics, performance calculations and propeller design. In spite of their simplicity these models are very efficient and accurate. Blade-element models use the local induced velocities as an input thus they should be combined with another model in order to calculate these induced velocities. Various models are used for the calculation of the induced velocity, where the most popular ones include: momentum, simplified-momentum, lifting-line (prescribed and free wake), and vortex (McCormick and Theodorsen) models. The paper describes the various models, compares their results and discusses the advantages and disadvantages of each one. The results indicate that the Bladeelement/simplified-momentum model offers very good accuracy together with high efficiency. For propeller performance calculations during steady axial flight, where most of the cross-sections do not experience stall, detailed and complicated models for calculating the induced velocities do not show advantages over the simple bladeelement/simplified-momentum model,
Development of a VTOL mini UAV for multi-tasking missions
Authors: Bataillé B. , Moschetta J.-M. , Poinsot D. , Bérard C. , Piquereau A.
Published: February 2016

Recent developments in the field of Mini-UAVs lead to successful designs in both hovering rotorcraft and fixed wing aircraft. However, a polyvalent MAV capable of stable hovering and fast forward flight is still expected. A promising candidate for such versatile missions consists of a tilt-body tail-sitter configuration. That concept is studied in this paper both from the flight mechanics and control points of view. Developments are based on an existing prototype called Vertigo. It consists of a tail sitter fixed-wing mini-UAV equipped with a contra-rotating pair of propellers in tractor configuration.

A wind-tunnel campaign was carried out to extract experimental results from the Vertigo aerodynamic characteristics. A 6-component sting balance was fitted in the powered model enabling excursion in angles of attack and sideslip angles up to 90°. Thus, a detailed understanding of the transition mechanism could be obtained. An analytical model including propwash effects was derived from experimental results.

The analytical model was used to compute stability modes for specific flight conditions. This allowed an appropriate design of the autopilot capable of stabilisation and control over the whole flight envelope. A gain sequencing technique was chosen to ensure stability while minimising control loop execution time. A MATLAB-based flight simulator including an analytical model for the propeller slipstream has been developed in order to test the validity of airborne control loops.

Simulation results are presented in the paper including hover flight, forward flight and transitions. Flight tests lead to successful inbound and outbound transitions of the Vertigo.
Downward pointing winglet design and assessment within the M-DAW research project
Authors: Hantrais-Gervois J.-L. , Grenon R. , Mann A. , Büscher A.
Published: February 2016

The design and performance analysis of a wing tip device proposed within the M-DAW project by ONERA is presented. A proto-design process is described and the device was thoroughly assessed (mainly with Reynolds-Averaged Navier-Stokes simulations). The process was further explained through wind-tunnel tests at both low speed and high speed in the pressurised and cryogenic European transonic wind tunnel in Cologne. The device is a downward pointing winglet designed for a retrofit scenario (the wing could be modified only within the 96% – 100% bounds of the span). It was designed to keep the wing root bending moment of the clean wing at cruise unchanged so that the aerodynamic gains are the net gains provided by the device that can be directly installed without structural modifications of the wing.
Effects of boundary-layers bleeding on unstart/restart characteristics of hypersonic inlets
Authors: Chang J. , Yu D. , Bao W. , Fan Y. , Shen Y.
Published: February 2016

A series of mixed-compression hypersonic inlets at different bleeding rates were simulated at different freestream conditions in this paper. The unstart/restart characteristics of hypersonic inlets were analysed and the reasons why the unstart/restart phenomenon is in existence is presented. The unstart/restart characteristics of hypersonic inlets at different bleeding rates were given. The effects of boundary-layer bleeding on the performance parameter (mass-captured coefficient, total-pressure recovery coefficient), starting and restarting Mach number of hypersonic inlets were discussed. In conclusion, boundary-layer bleeding can improve the performance parameter of hypersonic inlets, and can reduce the starting and restarting Mach number, and can broad the operation range of the hypersonic inlet.
CLoVER: an alterntive concept for damage interrogation in structural health monitoring systems
Authors: Salas K. I. , Cesnik C. E. S.
Published: February 2016

Structural Health Monitoring (SHM) is the component of damage prognosis systems responsible for interrogating a structure to detect, locate, and identify any damage present. Guided wave (GW) testing methods are attractive for this application due to the GW ability to travel over long distances with little attenuation and their sensitivity to different damage types. The Composite Long-range Variable-direction Emitting Radar (CLoVER) transducer is introduced as an alternative concept for efficient damage interrogation in GW SHM systems. This transducer has an overall ring geometry, but is composed of individual wedge-shaped anisotropic piezocomposite sectors that can be individually excited to interrogate the structure in a particular direction. The transducer is shown to produce actuation amplitudes larger than those of a similarly sized ring configuration for the same electric current input. The electrode pattern design used allows each sector to act as an independent actuator and sensor element, decreasing the number of separate transducers needed for inspection. The fabrication and characterisation procedures of these transducers are described, and their performance is shown to be similar to that of conventional piezocomposite transducers. Experimental studies of damage detection demonstrating the proposed interrogation approach are also presented for simulated structural defects.
A homogenisation-based continuum damage mechanics model for cyclic damage in 3D composites
Authors: Ghosh S. , Jain J. R.
Published: February 2016

This paper develops a 3D homogenisation based continuum damage mechanics (HCDM) model for fibre-reinforced composites undergoing micromechanical damage under cyclic loading. Micromechanical damage in a representative volume element (RVE) of the material occurs by fibre-matrix interfacial debonding, which is incorporated in the model through a hysteretic bilinear cohesive zone model. The proposed model expresses a damage evolution surface in the strain space in the principal damage co-ordinate system or PDCS. PDCS enables the model to account for the effect of non-proportional load history. The material constitutive law involves a fourth order orthotropic tensor with stiffness characterised as a macroscopic internal variable. Cyclic damage parameters are introduced in the monotonic HCDM model to describe the material degradation due to fatigue. Three dimensional damage in composites is accounted for through functional forms of the fourth order damage tensor in terms of components of macroscopic strain and elastic stiffness tensor. The HCDM model parameters are calibrated from homogenisation of micromechanical solutions of the RVE for a few representative cyclic strain histories. The proposed model is validated by comparing results of the HCDM model with pure micromechanical analysis results followed by homogenisation. Finally, the potential of cyclic HCDM model as a design tool is demonstrated through macro-micro analysis of cyclic damage progression in composite structures.
Vascular design for thermal management of heated structures
Authors: Lee J. , Lorente S. , Bejan A.
Published: February 2016

Vascular structures are contemplated for cooling the skins and leading surfaces of future high speed aircraft. This paper evaluates the proposal to cool with a flow architecture shaped as trees (dendritic) a parallelepipedic body that is heated uniformly. The coolant enters the body through one face and exits through the opposite face. The vasculature connects the two faces, and consists of trees that alternate with upside down trees. The fields for fluid flow and heat transfer are determined numerically in three dimensions. The effect of local pressure losses at bends, junctions and entrances is documented. Designs with tree-shaped architectures having up to four levels of bifurcation are evaluated for fluid flow and heat transfer performance, and are compared with the performance of a design with a single sheet of fluid sweeping the upper surface of the body. The fluid flow conductance of the tree designs increases when the number of bifurcation levels increases. The thermal performance of tree designs can be improved by endowing the tree design with more freedom such that the bifurcations generate asymmetric daughter channels. The tree designs outperform the fluid sheet design dramatically: the global thermal resistance of the tree designs is roughly one tenth of the global thermal resistance of the fluid sheet design.
Time delay comb transducers for aircraft inspection
Authors: Yan F. , Rose J. L.
Published: February 2016

An ultrasonic guided wave technique based on time delay comb transducers is introduced for aircraft inspection. It is demonstrated that for isotropic plate structures the time delay comb transducers with appropriate excitation are capable of performing discontinuity detections without knowing the precise isotropic material properties of the objects being inspected. Fibre-reinforced composite plates are also considered. The wave skew effects are investigated using both the slowness curve and the Poynting vector. A composite inspection technique that takes advantage of the skew effects is proposed. Using time delay comb transducers to excite the guided wave modes with different skew angles, the proposed technique is capable of scanning the composite plate in different directions without moving or rotating the transducers. By contrast with the applications in the isotropic cases, knowledge of the material properties and other necessary information that is needed to produce dispersion curves is generally required. Experimental results are provided as a validation of the proposed techniques.
Feasibility study of a supersonic business jet based on the Learjet airframe
Authors: Chudoba B. , Coleman G. , Czysz P. A. , Butler C. M.
Published: February 2016

Since the dawn of the jet age, passengers on all jet transports, except Concorde, have traveled at about the same speed — a standard Mach 0 83-0 87 range as a practical compromise. After 27 years of supersonic commercial travel, British Airways and Air France retired their fleet of Concorde aircraft at the end of 2003 because it was considered no longer profitable. Clearly, with the retirement of Concorde, the world has lost the only aircraft offering passenger transportation at supersonic speeds. Over the past several years manufacturers have proposed new aircraft designs that promise an increase in transportation speeds. In particular, the business jet market appears to present a business case for an exclusive supersonic business jet (SSBJ). However, there is a key-hurdle which has, until now, prevented the successful launch of a SSBJ hardware program: the development cost for an all-new aircraft quickly eradicates the soughtafter business case. This paper presents the results of a parametric sizing study which aims to answer the following question: is it possible to drastically reduce the development effort of a supersonic business jet design by converting an existing Learjet airframe into a supersonic vehicle while sustaining FAA interest and approval? This paper discusses selected aircraft sizing trades and operations related constraints. The feasibility study indicates some level of technical plausibility for the case of converting an existing airframe into a certifiable lower-cost supersonic aircraft. Acknowledging the range of actual complications related to the task of economically modifying and certifying a legacy airframe towards a SSBJ, it appears that a larger size SSBJ offers significant technical and economical advantages which outweigh the ‘off-the-shelf’ Learjet case.
Modelling methane-air turbulent diffusion flame in a gas turbine combustor with artifical neural network
Authors: Mehdizadeh N. S. , Sinaei P.
Published: February 2016

The present paper reports a way of using an artificial neural network (ANN) for modelling methane-air jet diffusion turbulent flame characteristics, such as temperature and chemical species mass fractions in a gas turbine combustion chamber. Since the neural network needs sets of examples to adapt its synaptic weights in the training phase, we used pre-assumed probability density function (PDF) method and considered chemical equilibrium chemistry model to compute the flame characteristics for generating the examples of input-output data sets. In this approach, flow and mixing field results are presented with a non-linear first order k-ε model. The turbulence model is applied in combination with preassumed β-PDF modelling for turbulence-chemistry interaction. The training algorithm for the neural network is based on a back-propagation supervised learning procedure, and the feed-forward multilayer network is incorporated as neural network architecture. The ability of ANN model to represent a highly non-linear system, such as a turbulent non-premixed flame is illustrated, and it can be summarized that the results of modelling of the combustion characteristics using ANN model are satisfactory, and the CPU-time and memory savings encouraging.
Development of a proof–of–concept aircraft smart control system
Authors: Hutapea P. , Jacobs K. , Harper M. , Meyer E. , Roth B.
Published: February 2016

Hutapea et al showed that an actuation system based on shape memory alloy coils could be employed for a wing flap of an aircraft. A continued research and development of these previously demonstrated smart flight control mechanisms was performed with the goal to develop a proof-of-concept shape memory alloy (SMA) actuation system, which utilises SMA springs to control the six degrees of freedom of an aircraft. For this actuation system, the springs are heated via an electric current, causing the spring to contract as the metal’s phase changes from martensite to austenite. The contraction allows the springs to function as linear actuators for the aircraft’s control surfaces, specifically the flaps and ailerons on the wings and horizontal stabilisers and a rudder on the tail. As a significant advancement to the overall actuation system, an air burst-cooling system increases the cooling rate of the coils by means of forced convection. Computer-based finite element model analysis and experimental testing were used to define and optimise SMA spring specifications for each individual control surface design. A onesixth scale proof-of-concept model of a Piper PA-28 Cherokee 160 aircraft was constructed to demonstrate and to verify the final actuation system design.
A method for calculating inlet distortion effects on stability of split-flow fans
Authors: Khaleghi H. , Doulgeris G. , Boroomand M. , Pilidis P. , Tousi A. M.
Published: February 2016

This paper presents a methodology for calculating the operability and performance of split-flow fans with inlet distortion. A one-dimensional stage-by-stage model has been developed to include parallel compressor theory. The model is capable of providing a detailed definition of the circumferential and radial flow fields. The low-pressure fan is divided to three radial divisions, near-hub, near-tip, and mid-span. The characteristics of each radial segment are calculated by using fan radial profiles. The stable and unstable operations of a split-flow fan, with and without inlet distortion, have been investigated in this study. For the clean inflow surge was triggered by the core compressor, whereas the fan spoiled sector was found to cause the compression system to surge for the distorted case.
Low noise engine design for the Silent Aircraft Initiative
Authors: Hall C. A.
Published: February 2016

The Silent Aircraft Initiative was a Cambridge-MIT Institute programme involving a large team of researchers from both the University of Cambridge and the Massachusetts Institute of Technology (MIT). The aim of the project was to produce a concept aircraft design that would be so quiet it would be imperceptible in the urban environments around airports.. This paper gives an overview of how all the sources of engine noise were carefully addressed within the Silent Aircraft design. Novel technologies, a new engine configuration, improved airframe integration, new operational procedures and advanced component design were all required in order to reduce the overall engine noise level to the Silent Aircraft target. The study suggests that in order to dramatically reduce the noise of future aircraft engines a number of major design changes must be combined.
The pilot model balked landing simulation project: A government, industry and national research cooperation
Authors: Hosman R. , Belyavin A. , Hörmann H. , Robel G. , Schuring J. , der Geest P. van , Towler J.
Published: February 2016

The introduction of new larger aeroplanes presents the ICAO Instrument Flight Procedures Panel (IFPP) with the need to review the requirements for the Obstacle Free Zone. To support future decisions, the IFPP took the initiative to ask for the development of pilot models which are capable to control the simulated aircraft during the approach — go-around manoeuvre. The aim of this development was to obtain a tool to perform Monte Carlo simulations for the determination of the flight path statistics of the manoeuvre. In 2001, both QinetiQ and the National Aerospace Laboratory (NLR) were invited to develop pilot models. The two pilot models are based on fundamentally different descriptions of a pilot’s control behaviour. The QinetiQ pilot model is based on a discrete-event representation of pilot control movements and has been developed in the Integrated Performance Modelling Environment (IPME). The NLR pilot model is based on control engineering and is a linear model with visual and motion feedback extended with stochastic disturbances. This development was supported by Boeing, which provided a simulation model of the B747–400 as the representative aircraft model. The integration of the pilot models with the aircraft model was performed by Boeing. Statistical data on the flight path tracking during the approach – go-around manoeuvre and on discrete pilot actions were obtained from simulations performed in a full flight simulator (FFS) at NASA Ames and a fixed-base simulator at Boeing. Both pilot models, the use of the statistical data from the simulations and the integration with the aircraft model are discussed in the paper.
Simulation of wake vortex effects for UAVs in close formation flight
Authors: Saban D. , Whidborne J. F. , Cooke A. K.
Published: February 2016

This paper addresses the development of multiple UAV deployment simulation models that include representative aerodynamic cross-coupling effects. Applications may include simulations of autonomous aerial refuelling and formation flying scenarios. A novel wake vortex model has been developed and successfully integrated within a Matlab/Simulink simulation environment. The wake vortex model is both sufficiently representative to support studies of aerodynamic interaction between multiple air vehicles, and straightforward enough to be used within real time or near real time air-to-air simulations. The model integration process is described, and computational results of a two-vehicle-formation flight are presented.
A multidisciplinary approach to structural health monitoring and damage prognosis of aerospace hotspots
Authors: Chattopadhyay A. , Peralta P. , Papandreou-Suppappola A. , Kovvali N.
Published: February 2016

The health monitoring and damage prognosis of aerospace hotspots is important for reducing maintenance costs and increasing in-service capacity of aging aircraft. One of the leading causes of structural failure in aerospace vehicles is fatigue damage. Based on the physical mechanism of damage nucleation and growth, a physics-based multiscale model is considered for fatigue damage assessment in metallic aircraft structures. A guided-wave based sensing approach is utilised to enable effective damage detection in a common structural hotspot: a lug joint. Finite element analysis is carried out with piezoelectric wafers bonded to the host structure and the simulated sensor signals are analysed. A damage classification strategy is developed, which integrates physically motivated time-frequency approaches with advanced stochastic modelling techniques. In particular, a variational Bayesian learning scheme is used to estimate the optimal model complexity automatically from the data, adapting the classifier for real-time use. Classification performance is studied as a function of signal-to-noise ratio and results are reported for the detection of fatigue crack damage in the lug joint. An adaptive hybrid prognosis model is proposed, which estimates the residual useful life of structural hotspots using damage condition information obtained in real-time.
New adaptive controller method for SMA hysteresis modelling of a morphing wing
Authors: Grigorie T. L. , Botez R. M.
Published: February 2016

A neuro-fuzzy controller method for smart material actuator (SMA) hysteresis modelling is presented, conceived for a morphing wing application. The controller correlates each set of forces and electrical currents that are applied to the smart material actuators with the actuator elongation. The actuator is experimentally tested for four forces, using a variable electrical current. The final controller is obtained through the Matlab/Simulink integration of three independent neuro-fuzzy controllers, designed for the increase and decrease of electrical current, and for null electrical current in the cooling phase of the actuator. This final controller gives a very small error with respect to the experimental values.
Simulation of automatic helicopter deck landings using nature inspired flight control
Authors: Voskuijl M. , Padfield G. D. , Walker D. J. , Manimala B. J , Gubbels A. W.
Published: February 2016

Research studies have indicated that the optical flow parameter, time to close tau, is the basis of purposeful control in the animal world, and used by both fixed wing and helicopter pilots during manoeuvring. This parameter is defined as the instantaneous time to close a gap (spatial or force) at the current closing rate. A novel automatic flight control strategy has been developed that makes use of optical flow theory and in particular, the parameter tau. This strategy has been applied to two distinct problems; (1) the landing of a helicopter on a ship and (2) the lateral repositioning of a helicopter. The first is a challenging case because the landing of a helicopter on a ship is one of the most dangerous of all helicopter flight operations. Furthermore, helicopters are often subject to torque oscillations during rapid collective control, which increases pilot workload significantly when operating with low power margins and/or whilst performing tasks that require accurate heave control. The second case demonstrates the generality of the technique. Both automatic manoeuvres were simulated successfully within desired limits, with the novel control strategy creating a ‘natural’, smooth, tau motion.
Performing co-ordinated turns with articulated wing-tips as multi-axis control effectors
Authors: Bourdin P. , Gatto A. , Friswell M. I.
Published: February 2016

This paper investigates a novel method for the control of aircraft. The concept consists of articulated split wing-tips, independently actuated and mounted on a baseline flying wing. The general philosophy behind the concept was that adequate control of a flying wing about its three axes could be obtained through local modifications of the dihedral angle at the wing-tips, thus providing an alternative to conventional control effectors such as elevons and drag rudders. Preliminary computations with a vortex lattice model and subsequent wind tunnel tests and Navier-Stokes computations demonstrate the viability of the concept for co-ordinated turns, with individual and/or combined wing-tip deflections producing multi-axis, coupled control moments. The multi-axis nature of the generated moments tends to over-actuate the flight control system, leading to some redundancy, which could be exploited to optimise secondary objective functions such as drag or bending moment.
Helicopter icing
Authors: Cao Y. , Chen K.
Published: February 2016

Due to constraints of natural condition, cost and of available time associated with model fabrication and for extensive wind-tunnel tests or flight tests, Computational Fluid Dynamics (CFD) simulation was considered an alternative means of providing air vehicle icing simulation and aeromechanic performance analysis. Full-scale icing experiments and, therefore, certification and cost can be significantly reduced by developing full-numerical simulation methods to evaluate the air vehicle performance for a wide range of icing conditions. This paper summarises helicopter icing simulation methods that include the development of helicopter aerodynamics, calculation methods of helicopter icing, icing protection system performance, icing effects on the helicopter performance, and some challenges in helicopter icing simulation.
An evaluation of the historical issues associated with achieving non-helicopter V/STOL capability and the search for the flying car
Authors: Saeed B. , Gratton G. B.
Published: February 2016

Combined Vertical and short take-off and landing, or ‘V/STOL’ capability has been of great demand and interest in the field of aeronautics since the creation of the aircraft. V/STOL capability is a targeted capability for many projected or prototype future aircraft. Past V/STOL aircraft are reviewed and analysed with regard to their performance parameters. This research has found two embedded categories in this class of aircraft based on their propulsion systems, i.e. jet and non-jet propulsion, and highlights the significant performance differences between them. In light of historical experience the performance of a relatively new class of aircraft, the flying cars, has been evaluated.
On the aerodynamics of the Miles M.52 (E.24/43) – a historical perspective
Authors: Brinkworth B. J.
Published: February 2016

The aerodynamic design of the Miles M.52 experimental supersonic aircraft is reviewed relative to the state of knowledge at its time of 1943 – 1946. Drawing on widely-ranging material, much not previously published, this study enlarges upon, and in places amends, previous accounts of the project.

Based on advice collated from the fields of aerodynamics and ballistics, Miles conceived an original and forward-looking design, backed by an extensive test programme. Novel solutions to new requirements in the areas of structures and systems provided a robust airframe, showing fair prospects of being stable and controllable throughout the specified flight envelope. An equally innovative power plant was devised for it by Whittle’s company, Power Jets Ltd.

Contradictory predictions of its performance were made by Miles and the RAE, through differences in their estimations of fuselage drag. A new evaluation suggests that the available information would have shown the aircraft to be capable of providing vital aerodynamic data for the transonic and early supersonic regimes at a time when no other sources were available, though further engine development would be needed for it to reach its full potential.