bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of hydrogen–air non–equilibrium chemistry on the performance of a model scramjet thrust nozzle
Authors: Stalker R. J. , Truong N. K. , Morgan R. G. , Paull A.
Published: February 2016

Two aspects of hydrogen-air non-equilibrium chemistry related to scramjets are nozzle freezing and a process called ‘kinetic afterburning’ which involves continuation of combustion after expansion in the nozzle. These effects were investigated numerically and experimentally with a model scramjet combustion chamber and thrust nozzle combination. The overall model length was 0·5m, while precombustion Mach numbers of 3·1±0·3 and precombustion temperatures ranging from 740K to 1,400K were involved. Nozzle freezing was investigated at precombustion pressures of 190kPa and higher, and it was found that the nozzle thrusts were within 6% of values obtained from finite rate numerical calculations, which were within 7% of equilibrium calculations. When precombustion pressures of 70kPa or less were used, kinetic afterburning was found to be partly responsible for thrust production, in both the numerical calculations and the experiments. Kinetic afterburning offers a means of extending the operating Mach number range of a fixed geometry scramjet.
Investigation into clustering of synthetic jet actuators for flow separation control applications
Authors: Liddle S. C. , Wood N. J.
Published: February 2016

An investigation into the behaviour of clustered synthetic jet Actuators for flow-control applications is described. Experiments have been undertaken with two small-scale synthetic jet actuators in a zero-pressure gradient boundary-layer, in order to investigate the effect of configuration yaw angle and relative input signal phase. Oil-flow visualisation and hotwire anemometry techniques were used, demonstrating that changes in the downstream flow structure could be observed. Compared to a streamwise configuration, in which a symmetrical counter-rotating vortex pair was produced by the synthetic jet-boundary-layer interaction, a broader asymmetric interaction was produced in a 15° yaw configuration. Streamwise velocity contour plots, illustrating the development of the interaction downstream, over four phase angles, were presented. Significant differences in the PSD analyses of downstream streamwise velocity time histories were found, suggesting that input signal phase could influence the stability and hence effectiveness of flow structures used in flow-control applications.
The Vortex Merger Factor in Aircraft Wake Turbulence
Authors: Mokry Miroslav
Published: February 2016

Vortex merger is studied within the context of two-dimensional discrete vortex sheets and demonstrated on two equally oriented circular vortices and aircraft tip and flap vortices. It is confirmed that, depending on the wing load distribution, the latter may or may not coalesce into a single counter-rotating pair. The interaction of a vortex with an equally oriented shear layer, governed by the same physical principle, suggests a possible intensification of an aircraft vortex in cross-wind shear.
2D numerical study of circular synthetic jets in quiescent flows
Authors: Tang H. , Zhong S.
Published: February 2016

2D numerical simulations of flows generated by a synthetic jet actuator with a circular orifice were conducted at two different diaphragm displacement settings, one representing a typical laminar case and the other a fully turbulent case. The flow in the cavity was included in the computation in order to provide more accurate predictions. A velocity boundary condition was applied at the neutral position of the diaphragm to account for its temporal deformation. Comparisons were made between the computational results and existing PIV and hot-wire data in terms of the time sequence of the velocity vector field, velocity variations in space and with time. It is found that computational results for the laminar case agree well with the experimental data. Four turbulent models were tested for the fully turbulent case. It was found that the predictions using the RNG κ-ε and Standard k-ε models were reasonably close to the experimental data. This initial study has produced some encouraging evidence for the capacity of FLUENT in simulating the key features of synthetic jets.
Industry applications of advanced flow diagnostics experience in the BAE Systems ground effects rig
Authors: Curtis P.
Published: February 2016

This paper reviews some of the work performed on the ground effects rig at BAE Systems in Warton, the now unique facility for modelling dynamic vertical landings and measuring hot gas ingestion. The paper discusses the flow diagnostic tools which have been used in recent times, up to the complexity of 3D PIV, and uses examples from the F-35 JSF programme to illustrate these. The paper hopefully demonstrates the difficulties of using these tools, as well as the benefits they can bring to a development programme.

The ground effects rig is a facility designed to measure temperature rise in aircraft intakes during vertical manoeuvres close to the ground. It is a complex facility that comes as close as possible to accurately modelling the flowfields around an aircraft moving both vertically and horizontally near the ground, with the ability to model dynamic pitch and roll at the same time.

Standard instrumentation for the models consists of rapid response thermocouples mounted in a rake at the engine face. 45 thermocouples of 0·05mm diameter with a time constant of about 10ms are used.

Although, with its standard instrumentation, the rig can measure how much hot gas gets to the engine face, it doesn’t show how it got there, or where it came from, which is the knowledge required to improve the design. Hence there is a need for flow diagnostics.
Jet thrust vectoring using a miniature fluidic oscillator
Authors: Raman G. , Packiarajan S. , Papadopoulos G. , Weissman C. , Raghu S.
Published: February 2016

This paper presents a new approach to vectoring jet thrust using a miniature fluidic actuator that provided spatially distributed mass addition. The fluidic actuators used had no moving parts and produced oscillatory flow with a square wave form at frequencies up to 1·6kHz. A subsonic jet with an exit diameter of 3·81cm was controlled using single and dual fluidic actuators, each with an equivalent circular diameter of 1·06mm. The fluidic nozzle was operated at pressures between 20·68 and 165·47kPa. The objectives of the present work included documentation of the actuation characteristics of fluidic devices, assessment of the effectiveness of fluidic devices for jet thrust vectoring, and evaluation of mass flow requirements for vectoring under various conditions. Measurements were made in the flow field using a pitot probe for the vectored and unvectored cases. Some acoustic measurements were made using microphones in the near-field and for selected cases particle image velocimetry (PIV) measurements were made. Thrust vectoring was obtained in low speed jets by momentum effects with fluidic device mass flow rates of only 2 × 10–4kg/sec (0·6% of main jet mass flow per fluidic oscillator). Although a single fluidic device produced vectoring of the primary jet, the dual fluidic device configuration (with two fluidic devices on either side of the jet exit) produced mass flux enhancement of 28% with no vectoring. Our results indicate that fluidic actuators have the potential for use in thrust vectoring, flow mixing and industrial flow deflection applications.
Simulation and flight test of a temperature sensing stabilisation system
Authors: Herrmann P. , Bil C.
Published: February 2016

Thermopile sensors detect electromagnetic radiation as a function of the object’s temperature. Because there is a temperature difference between the cold ground and the warm sky, these sensors could be used to detect the horizon and thus be used as a reference to stabilise a small aircraft, such as an unmanned aerial vehicle (UAV) in visual meteorological conditions (VMC). To verify this hypothesis, a system has been developed providing horizon detection using thermopile sensors to stabilise an R/C model aircraft. The aircraft has gone through a number of flight trials using remote control to enable and disable the stabilisation system. During the flight trials the aircraft was set at various attitudes when the system was enabled. The stabilisation system was able to assume wing level under various bank angles and weather conditions with minimum overshoot and oscillation.

Although the system shows good performance during flight trials, most of the original design was done using trial and error. A design tool was needed to implement further improvements to the system and to efficiently implement it on other aircraft. This required a good understanding of the physical behaviour of the system and the interaction between the sensors, aircraft and the environment. A mathematical model of the overall system was developed using the MATLAB/Simulink environment to simulate the behaviour of the system under various conditions. The simulation results were then compared with actual flight experiments. This paper describes the modelling techniques used for the different system components and the results of the simulation compared to actual flight trials.
Collision avoidance within flight dynamics constraints for UAV applications
Authors: Penney R. W.
Published: February 2016

Avoiding collisions with other aircraft is an absolutely fundamental capability for semi-autonomous UAVs. However, an aircraft avoiding moving obstacles requires an evasive tactic that is simultaneously very quick to compute, compatible with the platform’s flight dynamics, and deals with the subtle spatio-temporal features of the threat.

We will give an overview of a novel prototype method of rapidly generating smooth flight-paths constrained to avoid moving obstacles, using an efficient trajectory-optimisation technique. Obstacles are described in terms of simple geometrical shapes, such as ellipsoids, whose centres and shapes can vary with time. The technique generates a spatio-temporal trajectory which offers a high likelihood of avoiding the volume in space-time excluded by the predicted motion of each of the known obstacles. Such a flight-path could then be passed to the aircraft’s flight-control systems to negotiate the threat posed by the obstacles. Results from a demonstration implementation of the collision-avoidance technique will be discussed, including non-trivial scenarios handled well within 100ms on a 300MHz processor.
Design and structural analysis of a thrust chamber for a spinning supersonic rocket – a case study
Authors: Rajan K. M. , Narasimhan K.
Published: February 2016

The design of a thrust chamber for a rocket propulsion system is a challenging task. The thrust chamber has to be designed for minimum structural weight with an adequate factor of safety. This calls for a thorough knowledge of various structural loads, both internal and external, and the behaviour of the structure in flight. This paper presents the design and structural analysis of a pressure vessel used as thrust chamber for a rocket propulsion unit. The effects of kinetic heating, thermal stress, spinning and various aerodynamic loads and their mutual interactions are accounted for in this analysis. Based on a detailed stress analysis of the components and a modal/structural dynamic analysis of the flight vehicle as a whole, in which the thrust chamber is the main load bearing member, the required mechanical properties of the thrust chamber are obtained.
A novel approach to encouraging proper fatigue management in british army aviation training and operations
Authors: King R. P.
Published: February 2016

Fatigue management in military aviation remains problematic and can be easily neglected by planners and aircrew in a busy operational environment. The basic assessment tool (BAT) is an objective and educational computer tool for evaluating and combining various fatigue factors. It provides an impartial performance comparison while at the same time educating and reminding its users of the importance of fatigue management. Individual factors of the BAT were chosen because they affect fatigue, sleepiness, alertness and performance. A short explanation of components not chosen is also included. An example of how the BAT can be used is described and figures of the resulting outputs (screenshots) are included. Most commercial fatigue estimation products are subjective and do not consider specific issues associated with tactical operations in a field environment. This novel approach can be used to help plan missions by minimizing the BAT score while still maximising the tactical advantage and keeping fatigue management fresh in the minds of military rotary wing pilots while in training and on operations. Although the BAT is military aviation focused and objective, it can be easily modified to suit particular fatigue concerns.
A numerical study on the mixing of air and hydrogen in a scramjet combustor
Authors: Ali M. , Fujiwara T.
Published: February 2016

A numerical study on mixing of air and hydrogen is performed by solving two-dimensional full Navier-Stokes equations. The main stream is air of Mach 5 entering through the configured inlet of the combustor and gaseous hydrogen is injected from the configured jet on the side wall. Supersonic mixing and diffusion mechanisms of a transverse hydrogen jet in two-dimensional finite air streams have been analyzed and discussed. The computed results are compared with the experimental data and show good agreement. For an otherwise fixed combustor geometry, the air inlet width and injection angle are varied to study the physics of mixing and flow field characteristics. On the effect of inlet width variation, two competing phenomena have been observed: (i) upstream of injector the strength of recirculation is higher for wider inlet and consequently the mixing increases, and (ii) downstream, the diffusion of hydrogen decreases with the increase of inlet width and eventually mixing decreases. As a result, in far downstream the mixing efficiency increases up to certain inlet width and then decreases for further increment of inlet width. For the variation of injection angle results show that upstream of injector the mixing is dominated by recirculation and downstream the mixing is dominated by mass concentration of hydrogen. Upstream recirculation is dominant for injecting angle 60° and 90°. Incorporating the various effects, perpendicular injection shows the maximum mixing efficiency and its large upstream recirculation region has a good flame holding capability.
Development of an airship for tropical rain forest canopy exploration
Authors: Dorrington G. E.
Published: February 2016

The design, manufacture and testing of a 480 cubic metre helium-filled airship, or dirigible balloon, intended for flight above tropical rain forest canopy is outlined. The requirements for the airship and the preliminary sizing method are set-out. Details of the final design and flight test results are included, as well as suggestions concerning future work. Particular attention is paid to the issue of accurate station-keeping and operation close to the canopy with winds present. It is concluded that the development of a truly useful aerial platform for canopy biological studies requires further research in aerodynamics, dynamic simulation and ultra-quiet propulsion systems.
Bio-inspired design of flapping-wing micro air vehicles
Authors: Jones K. D. , Bradshaw C. J. , Papadopoulos J. , Platzer M. F.
Published: February 2016

In this paper the development and flight testing of flapping-wing propelled, radio-controlled micro air vehicles are described. The unconventional vehicles consist of a low aspect ratio fixed-wing with a trailing pair of higher aspect ratio flapping wings which flap in counterphase. The symmetric flapping-wing pair provides a mechanically and aerodynamically balanced platform, increases efficiency by emulating flight in ground effect, and suppresses stall over the main wing by entraining flow. The models weigh as little as 11g, with a 23cm span and 18cm length and will fly for about 20 minutes on a rechargeable battery. Stable flight at speeds between 2 and 5ms–1 has been demonstrated, and the models are essentially stall-proof while under power. The static-thrust figure of merit for the device is 60% higher than propellers with a similar scale and disk loading.
Studies of capacity estimation of the airport with two parallel runways
Authors: Cao Yihua , Chen Yong , Zhou Yong
Published: February 2016

The analytical capacity models of an airport with two runways system are developed in this paper and the theoretical capacity curves yielded by this model are analysed. The statistic airport capacity estimation methodology based on historical data is introduced as well. Both analytical models and statistic strategy are applied to estimate the capacity of the two runways system of a typical airport. Two sets of airport capacity curves obtained in different ways are compared and analysed. The result of the analysis indicates that the mathematical model works effectively in a fairly accurate way in the estimation of airport capacity.
Air Travel – Greener by Design Mitigating the environmental impact of aviation: Opportunities and priorities
Authors:   Report of the Air Travel - Greener by Design Science and Technology Sub Group
Published: February 2016

The Technology Sub-Group of Air Travel – Greener by Design was instituted at the first full meeting of the GBD community in March 2000. Its first period of intense activity was from the summer of 2000 to the spring of 2001, culminating in the publication of its report The Technology Challenge in July 2001 at the first Air Travel – Greener by Design Conference at the Royal Aeronautical Society.

In the period that followed, the contents of the report were further disseminated by presentations at conferences and publication of the report in The Aeronautical Journal but there was no substantial activity by the Sub-Group as such. In July 2003, a workshop on ‘The Effect of Aviation on the Atmosphere’, was held at St Catherine’s College, Cambridge. This was planned jointly by members of the Sub-Group and of the Centre for Atmospheric Science in the Department of Chemistry at Cambridge and was jointly funded by GBD and the EC project SCENIC. The organisation of events on the day and the collating and editing of the workshop report was done by Dr Helen Rogers of the Centre for Atmospheric Science. The workshop was attended by a broad cross section from the manufacturing and operating industries, government and academia and its report is a valuable summary of current understanding in 2003.
A civil aviation safety assessment model using a Bayesian belief network (BBN)
Authors: Greenberg R. , Cook S. C. , Harris D.
Published: February 2016

In this paper we present a Bayesian belief network (BBN) socio-technical model for investigating the accident rate for multi-crew civil airline aircraft. The model emphasises the influence of airline policy and societal behaviour patterns on the pilots within the piloting system. The main claim of this paper is that a BBN can be used to bring most aviation safety-critical elements into a common quantitative safety assessment despite the unique problems posed by the very low probability of accidents. We support this claim by replicating certain phenomena such as the low accident rate, the difference between the ‘more’ and ‘less’ safe airlines and other statistical factors of civil aviation. In particular, the model succeeds in explaining the large gap of six to seven orders of magnitude between in-flight measurements of pilots’ error and accident rate.
Dynamic gain-scheduled control of the ICE 101-TV
Authors: Jones C. D. C. , Richardson T. S. , Lowenberg M. H.
Published: February 2016

This paper shows the theoretical development and application of dynamic gain scheduled control – a novel method for the control of nonlinear systems – to an aircraft model. The idea behind this method is to schedule the control law gains with a fast varying state variable rather than with a slow varying state or an input parameter. This is advantageous as it is then possible to schedule the gains with a state variable that is dominant in the mode that we are most interested in controlling. The use of this type of gain scheduling is shown to improve the transient response of the aircraft model when stepping between trim conditions and to overcome some of the problems associated with conventional gain scheduled controllers (such as control surface position limit saturation). ‘Hidden coupling terms’ that introduce unwanted dynamics when scheduling gains with a fast state (rather than the input design parameter) are eliminated directly by applying a transformation to the classical parameter-scheduled gain distributions which are calculated using eigenstructure assignment. A second order longitudinal model and a 5th order longitudinal/lateral model of the ICE 101-TV tailless delta-wing aircraft configuration are used to demonstrate the design process.
Status and perspectives of laminar flow
Authors: Schrauf G.
Published: February 2016

After identifying the ecological and economic drivers for use of laminar flow technology, we outline the mechanisms of laminarturbulent boundary layer transition and review the status of natural laminar flow (NLF) and hybrid laminar flow control (HLFC). New ways to reduce the complexity of HLFC systems are presented, and the remaining steps to achieve technology readiness are discussed.
A civil aviation safety assessment model using a bayesian belief network (BBN)
Authors: Greenberg R. , Cook S. C. , Harris D.
Published: February 2016

In this paper we present a Bayesian belief network (BBN) sociotechnical model for investigating the accident rate for multi-crew civil airline aircraft. The model emphasises the influence of airline policy and societal behaviour patterns on the pilots within the piloting system. The main claim of this paper is that a BBN can be used to bring most aviation safety-critical elements into a common quantitative safety assessment despite the unique problems posed by the very low probability of accidents. We support this claim by replicating certain phenomena such as the low accident rate, the difference between the ‘more’ and ‘less’ safe airlines and other statistical factors of civil aviation. In particular, the model succeeds in explaining the large gap of six to seven orders of magnitude between in-flight measurements of pilots’ error and accident rate.
A feasiblity study on designing model support systems for a blended wing body configuration in a transonic wind tunnel
Authors: Maina M. , Corby N. , Crocker E. L. , Hammond P. J. , Wong P. W. C.
Published: February 2016

It is considered that the blended wing body may offer the possibility of improvements in performance efficiency over the conventional civil transport. Such configurations will require transonic wind tunnel testing. Hence, a feasibility study has been carried out at ARA to investigate possible model support systems that could be used for this purpose. The study addressed issues arising from the mechanical design of two support systems; namely, a blade or Z-sting and a standard rear sting. In particular, the relatively restricted space available within the model fuselage has presented challenges in the design of the layout of the balance and instrumentation required for the model. CFD analysis has been carried out to assess the relative interference effects of the two support arrangements. This initial work has shown unexpectedly significant interference effects associated with the Z-sting support and attention is drawn to the need for further design work to minimise these effects.
Modelling the flight dynamics of the hang glider
Authors: Cook M. V. , Spottiswoode M.
Published: February 2016

The development of the non-linear equations of motion for the hang glider from first principles is described, including the complex geometry of control by pilot ‘weight shift’. By making appropriate assumptions the linearised small perturbation equations are derived for the purposes of stability and control analysis. The mathematical development shows that control is effected not by pilot weight shift, but by centre of gravity shift and that lateral-directional control by this means is weak, and is accompanied by significant instantaneous adverse response.

The development of a comprehensive semi-empirical mathematical model of the flexible wing aerodynamics is described. In particular, the modelling attempts to quantify camber and twist dependencies. The performance of the model is shown to compare satisfactorily with measured hang glider wing data obtained in earlier full scale experiments. The mathematical aerodynamic model is then used to estimate the hang glider stability and control derivatives over the speed envelope for substitution into the linearised equations of motion.

Solution of the equations of motion is illustrated and the flight dynamics of the typical hang glider are described. In particular, the dynamic stability properties are very similar to those of a conventional aeroplane, but the predicted lateral directional stability margins are significantly larger. The depth of mathematical modelling employed enables the differences to be explained satisfactorily. The unique control properties of the hang glider are described in some detail. Pitch and roll control of the hang glider is an aerodynamic phenomenon and results from the pilot adjusting his position relative to the wing in order to generate out of trim aerodynamic control moments about the centre of gravity. Maximum control moments are limited by hang glider geometry which is dependent on the length of the pilot‘s arm. The pilot does not generate control moments directly by shifting his weight relative to the wing. The modelling thus described would seem to give a plausible description of the flight dynamics of the hang glider.
Benefits and design challenges of adaptive structures for morphing aircraft
Authors: Moorhouse D. , Sanders B. , Spakovsky M. von , Butt J.
Published: February 2016

The purpose of this paper is to discuss the future of adaptive structures leading towards the concept of a fully morphing aircraft configuration. First, examples are shown to illustrate the potential system-level mission benefits of morphing wing geometry. The challenges of design integration are discussed along with the question of how to address the optimisation of such a system. This leads to a suggestion that non-traditional methods need to be developed. It is suggested that an integrated approach to defining the work to be done and the energy to be used is the solution. This approach is introduced and then some challenges are examined in more detail. First, concepts of mechanisation are discussed as ways to achieve optimum geometries. Then there are discussions of non-linearities that could be important. Finally, the flight control design challenge is considered in terms of the rate of change of the morphing geometry. The paper concludes with recommendations for future work.
The development of a target-lock-on optical remote sensing system for unmanned aerial vehicles
Authors: Hsiao F-B , Liu T-L , Chien Y-H , Lee M-T , Hirst R.
Published: February 2016

The use of unmanned aerial vehicles (UAVs) in various military and civil applications is the subject of much current attention. With recent developments in personal computer technology, and the availability at affordable cost of peripherals, and electronic and optical sensors, UAVs for long endurance missions, with flight autonomy beyond the visual range, have become an attractive challenge for study in universities and research institutes. This paper describes the development of a target-lock-on optical remote sensing system to be used as a payload in a university-class UAV. To accomplish autonomous way-point navigation for the conduct of optical sensing surveillance, a gimbaled-platform with servo control and an Attitude and Heading Reference System (AHRS) navigation system for UAV position and attitude measurements have been developed. The UAV also utilises a Global Position System (GPS) receiver, a pressure altimeter, gyroscopes and an electric compass. A novel mathematical model is proposed to calculate the optimal parameters for orientating the CCD camera line of sight with a ground target, designated in real time from a ground control station. Both ground and flight test results have demonstrated the feasibility of the navigation control scheme and the UAV’s ability to conduct ground target acquisition and image transmission.
Numerical calculation of separated flow past square and rectangular cylinders using panel technique
Authors: Roy A. , Bandyopadhyay G.
Published: February 2016

In the present investigation, a potential flow model based on panel method has been developed for calculation of two dimensional separated flows past square and rectangular cylinders. Free vortex lines are assumed to emanate from the points of separation that converge downstream of the body. The converged wake shape is iteratively obtained by integrating the velocity vectors at the collocation points. For solving separated flow past square and rectangular cylinders, four different versions of the solver have been developed for a wide range of incidence, namely, for zero, low, moderate and high angles of incidence. For validation of computed results, experimental investigations have been carried out in a low speed wind tunnel to obtain the surface pressure distribution on square cylinder and rectangular cylinder over a range of angles of incidence. Comparison is reasonably good.
System of systems force structure optimisation
Authors: McCoy M. S.
Published: February 2016

A system of systems study plan was developed and a prototype was executed to optimise a recommended military force structure. This methodology defined the optimal force structure, using constrained optimisation to reflect budget limitations and desired mission performance. The force structure included surface and air assets, a command, control, communications, computers, intelligence, surveillance and reconnaissance (C4ISR) architecture, and a recommended logistics infrastructure. A second aspect of the study plan defined the total acquisition strategy, which accounted for: retiring legacy assets, extending the service life of existing assets until new replacements became available, and acquiring new assets for deployment, within the budget allocation. This methodology combined various modeling and simulation techniques to meet three study objectives. First, a nonlinear mixed integer programming model maximised performance, subject to cost constraints, cost as an independent variable (CAIV). Second, a dynamic programming model scheduled the transition from the legacy force structure to the future force, defined by the previous modeling technique. Third, a process simulation model simulated performance, over a one-year time period, for 25 areas of responsibility and five missions. This model verified performance estimates generated by the previous models.
Potential of reducing the environmental impact of aviation by using hydrogen Part I: Background, prospects and challenges
Authors: Haglind F. , Hasselrot A. , Singh R.
Published: February 2016

The main objective of the paper is to evaluate the potential of reducing the environmental impact of civil subsonic aviation by using hydrogen fuel. The paper is divided into three parts of which this is Part I, where the background, prospects and Challenges of introducing an alternative fuel in aviation are outlined. In Part II the aero engine design when using hydrogen is covered, and in Part III the subjects of optimum cruising altitude and airport implications of introducing liquid hydrogen-fuelled aircraft are raised.

Looking at the prospect of alternative fuels, synthetic kerosene produced from biomass turns out to be feasible and offers environmental benefits in the short run, whereas hydrogen seems to be the more attractive alternative in the long run.

Powering aero engines and aircraft with hydrogen has been done successfully on a number of occasions in the past. Realising this technology change for a fleet of aircraft poses formidable challenges regarding technical development, energy requirement for producing hydrogen, handling, aircraft design and making liquid hydrogen economically compatible with kerosene.
Dynamics and Control of Single-Line Kites
Authors: Sánchez G.
Published: February 2016

This paper presents a dynamic analysis of a single-line kite with two degrees of freedom. A Lagrangian formulation is used to write convenient equations of motion. The equilibrium states of the system and their stability are studied; Eigenvalues and eigenmodes are calculated by using linear theory. The stability in the parametric plane δ – W0 is discussed, where δ defines the bridle geometry and W0 is wind velocity. The system goes through a Hopf bifurcation and periodic branches of solutions appear. The orbits and their stability have been calculated numerically using Floquet theory and wind velocity seems to play an important role in their existence. Finally the kite response against gusts is considered and an open loop control system developed to keep the flight altitude invariant under changing atmospheric conditions. Modifying the bridle’s geometry seems to be a convenient way to control a kite’s performance.
Longitudinal flight control design with handling quality requirements
Authors: Saussié D. , Saydy L. , Akhrif O.
Published: February 2016

This work presents a method for selecting the gain parameters of a C* control law for an aircraft’s longitudinal motion. The design incorporates various handling quality requirements involving modal, time- and frequency-domain criteria that were fixed by the aircraft manufacturer. After necessary model order-reductions, the design proceeds in essentially two-steps: stability augmentation system (SAS) loop design and control augmentation system (CAS) loop design. The approach partly relies on the use of guardian maps to characterise, in each case, the set of gain parameters for which desired handling quality requirements are satisfied. The approach is applied throughout the full flight envelope of a business jet aircraft and yields satisfactory results.
Single and multi–objective UAV aerofoil optimisation via hierarchical asynchronous parallel evolutionary algorithm
Authors: Gonzalez L. F. , Lee D. S. , Srinivas K. , Wong K. C.
Published: February 2016

Unmanned aerial vehicle (UAV) design tends to focus on sensors, payload and navigation systems, as these are the most expensive components. One area that is often overlooked in UAV design is airframe and aerodynamic shape optimisation. As for manned aircraft, optimisation is important in order to extend the operational envelope and efficiency of these vehicles. A traditional approach to optimisation is to use gradient-based techniques. These techniques are effective when applied to specific problems and within a specified range. These methods are efficient for finding optimal global solutions if the objective functions and constraints are differentiable. If a broader application of the optimiser is desired, or when the complexity of the problem arises because it is multi-modal, involves approximation, is non-differentiable, or involves multiple objectives and physics, as it is often the case in aerodynamic optimisation, more robust and alternative numerical tools are required. Emerging techniques such as evolutionary algorithms (EAs) have been shown to be robust as they require no derivatives or gradients of the objective function, have the capability of finding globally optimum solutions among many local optima, are easily executed in parallel, and can be adapted to arbitrary solver codes without major modifications. In this paper, the formulation and application of a evolutionary technique for aerofoil shape optimisation is described.

Initially, the paper presents an introduction to the features of the method and a short discussion on multi-objective optimisation. The method is first illustrated on its application to mathematical test cases. Then it is applied to representative test cases related to aerofoil design. Results indicate the ability of the method for finding optimal solutions and capturing Pareto optimal fronts.
Thermal buckling of a thin uniform circular disk: a comparison of predictions
Authors: Seffen K. A.
Published: February 2016

The conditions for thermally-induced buckling of an unloaded thin, circular disk are compared from two well-known but unconnected studies: an approximate solution by Freund for a constant thickness disk, which must neglect the free edge condition, and an exact solution by Mansfield but only for a disk whose thickness tapers to zero in a particular manner. It is shown that buckling occurs at slightly higher values compared to a finite element analysis of a constant thickness disk but that the case of variable thickness seems to offer a closer result, which suggests that it better models the boundary layer behaviour near the free edge.
Considerations for UAV design and operation in South African airspace
Authors: Ingham L. A. , Jones T. , Maneschijn A.
Published: February 2016

At present, the lack of UAV regulations and standards precludes UAVs from being certified to operate commercially in un-segregated civilian airspace. Because of strategic, economical and security requirements, it is necessary to devise a method to operate UAVs in South African airspace within existing regulatory arrangements. This paper suggests specific UAV missions, viz; maritime patrol/boarder control, search and rescue, and cargo transport, together with design considerations and possible concepts of UAV; operations, maintenance and training, that will enable UAVs to satisfy the immediate South African strategic requirements whilst further UAV standards and regulations are being developed.
Aeroelastic response of helicopter rotors using a 3D unsteady aerodynamic solver
Authors: Gennaretti M. , Bernardini G.
Published: February 2016

The prediction of blade deflections and vibratory hub loads concerning helicopter main rotors in forward flight is the objective of this work. They are determined by using an aeroelastic model derived through the coupling between a nonlinear blade structural model and a boundary integral equation solver for three-dimensional, unsteady, potential aerodynamics. The Galerkin method is used for the spatial integration, whereas the periodic blade response is determined by a harmonic balance approach. This aeroelastic model yields a unified approach for aeroelastic response and blade pressure prediction that may be used for aeroacoustic purposes, with the possibility of including effects from both blade-vortex interaction and multiple-body aerodynamic interaction. Quasi-steady aerodynamic models with wake-inflow from the three-dimensional aerodynamic solver are also applied, in order to perform a comparative study. Numerical results show the capability of the aeroelastic tool to evaluate blade response and vibratory hub loads for a helicopter main rotor in level flight conditions, and examine the sensitivity of the predictions on the aerodynamics model used.
Computational and experimental
investigations of low-Reynolds-number flows past an
aerofoil
Authors: Yuan W. , Khalid M. , Windte J. , Scholz U. , Radespiel R.
Published: February 2016

This paper presents investigations of
low-Reynolds-number flows past an SD7003 aerofoil at
Re = 60k, where transition takes place across a
laminar separation bubble (LSB). Results of
experimental measurements and numerical calculations
are analysed and discussed. In particular,
reasonably good results were obtained using two
different numerical approaches: Large-eddy
simulation (LES) that demonstrated vortical
structures at different transition stages, and where
the transition occurred naturally; unsteady
Reynolds-averaged Navier-Stokes (URANS) simulations
for several turbulence models based on the
ω-length-scale equation, coupled to a linear
stability solver to predict the transition
position.
Effect of stagnation temperature on
supersonic flow parameters application for air in
nozzles
Authors: Zebbiche T. , Youbi Z.
Published: February 2016

When the stagnation temperature of a perfect gas
increases, the specific heats and their ratio do not
remain constant and start to vary with the
temperature. The gas remains perfect; its state
equations remain valid, so it can be named as
calorifically imperfect gas. The aim of this
research is to develop the necessary thermodynamic
and geometrical equations and to study the
supersonic flow at high temperature, lower than the
dissociation threshold. The results are found by the
resolution of nonlinear algebraic equations and
integration of complex analytical functions where
the exact calculation is impossible. The dichotomy
method is used to solve the nonlinear equations and
Simpson’s algorithm for the numerical integration
applied. A condensation of the nodes is used. The
functions to be integrated have a high gradient at
the extremity of the interval of integration. The
comparison is made with the calorifically perfect
gas to determine the error. The application is made
for air in a supersonic nozzle.
Aircraft flight characteristics in
conditions of windshear and icing
Authors: Cao Yihua , Yuan Kungang
Published: February 2016

Complex weather conditions, especially windshear and
icing encounter, have severe effects on aircraft
flight safety. The effect of low-altitude windshear
and ice accretion on aircraft performance and
control has been studied in this paper. With the
employment of a windshear model and nonlinear
inverse dynamics (NID) method, a low-altitude
windshear penetration flight control law is
designed. The effect of ice accretion was modeled on
the stability and control of an aircraft. Several
icing parameters are imported to the small
disturbance flight dynamics model to calculate the
change of performance, stability and control
derivatives between clean and iced aircraft. These
derivatives were used to calculate the elevator, the
aileron and the rudder step responses to investigate
the icing effect.

The simulation results indicate that the NID control
logic works effectively in the trajectory control of
the aircraft during the penetration of windshear.
The method used to study the effect of ice accretion
on aircraft is valid and it can provide data for
real-time calculation for icing encounter.
New commercial opportunities in space
Authors: Ashford D. M.
Published: February 2016

This paper assesses new commercial opportunities in space. The main conclusion is that spaceplanes can reduce the cost of human transport to orbit sufficiently for large new commercial markets to develop. Combining the reusability of spaceplanes with the high traffic levels of space tourism offers the prospect of a thousandfold reduction in the cost per seat to orbit. The result will be airline operations to orbit involving dozens of spaceplanes, each capable of one or two flights per day. These low costs will make possible a rapid expansion of space science and exploration.

The prototype of a small orbital spaceplane, needed to trigger this line of development, could be developed in about six years at a cost comparable to one or two flights of the Space Shuttle. It might be possible to progress from this prototype to airline operations within ten years, given a massive development effort.
Performance of non-rigid airships operating in the neutral buoyancy condition
Authors: Dorrington G. E.
Published: February 2016

The feasibility of using neutrally-buoyant (or fully-buoyant) airships for passenger and cargo transportation is investigated. The drag coefficients of rigid and non-rigid airships are deduced from flight data. Comparisons are made with empirical drag formulas and previous wind tunnel data. Some general trends for airship drag are derived. The mass breakdown of non-rigid airships with hull volumes up to 35,000m3is analysed using parametric equations. The maximum feasible airspeed and useful load carrying capacity of projected airships are calculated. ‘Specific productivity’ is found to be lower than values achievable with fixed-wing aircraft, but ‘fuel-specific productivity’ is found to be competitive, confirming results of a previous NASA study. The use of gaseous hydrogen and fuel cells is briefly discussed.
A review of supersonic business jet design Issues
Authors: Smith H.
Published: February 2016

Key issues relating to the Supersonic Business Jet (SBJ) concept are reviewed with the intent to assess the readiness of enabling technologies and hence the concept itself. The multidisciplinary nature of aircraft design precludes an in-depth analysis of each specific aspect, which could individually be the subject of a separate discipline review, hence an overview is presented.

The review looks at the market, environmental issues, with particular reference to the sonic boom phenomenon & solutions, technological issues, including prediction methods, flight testing, systems, certification and interested aerospace companies and design organisations.

It is apparent that the need to reduce the sonic boom signature is vital if the vehicle is to be permitted to operate over land and hence be economically viable. It is clear that sonic boom acceptability requirements must be set if resources are to be effectively focused and designs are to converge. Despite this challenge, considerable investment is aimed at de-risking many of the enabling technologies and raising readiness levels. Many technologies are moving beyond theoretical and numerical analysis into the experimental and flight test domains. Collaboration between the civil and military sectors is increasing.

Clearly, supersonic air travel is not an efficient means of personal conveyance; however, concerns for the environment are difficult to balance against the ‘value of time’ benefits offered by the SBJ concept. Air travel, of which this is a specialised form, is important to the global economy. Continued effort in the areas of human factors, customer demand and certification & requirements would be beneficial.
A model for solar powered aircraft preliminary design
Authors: Rizzo E. , Frediani A.
Published: February 2016

Solar powered aircraft are becoming more and more interesting for future long endurance missions at high altitudes, because they could provide Earth monitoring, telecommunications, etc. without any atmospheric pollution and, hopefully in the near future, with competitive costs compared with satellites. The research activities carried out till now have been mainly focused on flying wings or conventional aircraft configurations, with a great emphasis on the technological aspects. The present paper aims to define a mathematical model for solar powered aircraft preliminary design, valid independently of the aerodynamic configuration. A preliminary analysis is carried out in order to simulate Helios and the results are compared with those available from the flights of this aircraft. The proposed mathematical model is used also to compare four different aircraft configurations, namely: a flying wing, a conventional aircraft, a twin boom aircraft and a biplane aircraft. The results obtained are discussed in the paper and an optimum aircraft is analysed.