bluuebunny/crossref_metadata_2025_split huggingface dataset:
Future challenges for powerplant aerodynamic integration in combat aircraft
Authors: Philpot M. G. 
Published: July 2016

AbstractThe operational requirements of modern combat aircraft demand complex engine intake and exhaust systems, capable of working efficiently over a very wide range of flight conditions and throttle settings. In addition to high aerodynamic efficiency and avoidance of high distortion levels at the engine face, these systems must also meet rigorous radar and infra-red signature targets. This paper discusses the implications from the aerodynamics point of view. Examples of technical approaches which seek to balance the sometimes conflicting requirements of aerodynamics and signatures are outlined. The potential offered by in-flight thrust vectoring to enhance flight performance and/or safety is also reviewed and the aerodynamic implications considered. Overall, propulsion integration for combat aircraft presents several challenges to the aerodynamicist, not least the development and validation of improved theoretical design methods capable of analysing the highly complex flows involved.
Performance enhancement evaluation of an actuated trailing edge flap
Authors: Chan W. , Brocklehurst A. 
Published: July 2016

AbstractAn analytical evaluation of the performance enhancement due to a servo-actuated trailing edge flap was carried out using the coupled rotor-fuselage model (CRFM). The performance enhancement from a trailing edge flap is achieved by introducing effective camber around the azimuth for a nominal aerofoil. An investigation on the best combination of flap parameters, namely the span, position, chord and deflection was carried out in order to identify an optimal configuration within given design constraints. The effects on vibratory control loads over a range of speed for a flap of 10% span, 20% chord, actuated at once per rev has expanded the retreating blade envelope for a Lynx aircraft by some 20kt. The flap hinge load was also examined and it was found not to be excessive. It was also confirmed that an actuated trailing edge flap does not have adverse effect on the pilot's control inputs to trim to a particular flight condition. This paper will discuss the aerodynamic enhancements derived from the application of the trailing edge flap and present conclusions drawn from this study.
Numerical and experimental investigations of air-jet vortex generators in streamwise pressure gradients
Authors: Lewington N. P. , Henry F. S. , Peake D. J. , Singh C. 
Published: July 2016

AbstractNumerical and experimental results are presented demonstrating the sensitivity of the performance of air-jet vortex generators (AJVGs) operating at jet to freestream velocity ratios of up to 4 to jet pitch and jet skew. The merits of installing co- or counter-rotational systems are shown. Numerical results for AJVG arrays on a flat plate in a zero pressure gradient indicate optimum values for jet spacing and velocity ratios to enhance the downstream skin friction above the uncontrolled value. The installation of a co-rotating array of AJVGs into a modified NACA 23012 unswept wing and the improvements in the lift and drag performance are illustrated. It is demonstrated that by careful implementation of boundary conditions in relatively straightforward ‘numerical’ experiments it is possible to carry out a sensitivity analysis on the vortex generator arrays before they are implemented in successfully enhancing wing performance.
Numerical and experimental investigations on the reduction of wind tunnel wall interference by means of adaptive slots
Authors: Meyer O. , Nitsche W. , Futterer I. 
Published: July 2016

AbstractThe flow in many wind tunnel experiments is affected by the presence of test section walls. The resulting interference can be minimised by correcting the measured model pressures, or by influencing the model flow directly with the use of ventilated or adaptive test section walls. The objective behind the latter technique is to guide the flow in the test section to achieve low interference (i.e. free flow) condition at the model. The most successful technique of flexible, adaptive walls is still restricted to small research wind tunnels due to its mechanical complexity. However, a very promising alternative is the use of adaptive slots in the test section walls. This concept combines the method of passive slotted walls, as they are already implemented in many large wind tunnels, and flexible walls. Additionally, this technique presents the opportunity of full 3D adaptations because the slots can be situated in all four test section walls.This paper presents preliminary experimental results and the latest numerical calculations on the effectiveness of adaptive slots. The experiments were conducted under high subsonic flow conditions in the new slotted test section of the transonic wind tunnel at TU Berlin’s Aeronautical Institute (ILR).The numerical results presented are focussed on the 2D slot adaptation of a 2D-model (CAST7 aerofoil) and the 3D slot adaptation of a body of revolution (3D-ETB). In addition, basic studies were made of the flows associated with a single slot on one wall and a bump on the other.The numerical and the first experimental investigations have shown the potential of adaptive slots to reduce wall interferences effectively. The adaptation accuracy of the investigated slot configurations deviated not more than 3% from the reference case (2D-wall adaptation).
Saving costs in design, manufacturing and operation of aero engine parts
Authors: Broede J. 
Published: July 2016

AbstractBasic requirements for aero engine parts are to carry loads at high temperatures safely over service periods of 30-40 years. This generally calls for the best and latest materials and for highly sophisticated design and manufacturing procedures.These requirements are frequently in contrast to the desire to keep costs at affordable levels. This aims at the costs at both the customer’s side as well as the manufacturer’s side. The measures to reduce cost in the design and production phase are various:• redesign to allow for less complex manufacturing processes• reassessment of quality characteristics without reduction of overall quality (only those characteristics to be maintained which are really critical)• acceptance of minor damage in new parts which would be acceptable for repaired parts according to technical standards• assessment of all steps in the production process with respect to their influence on the final product properties• more stabilised manufacturing processes which use only a portion of accepted tolerance bands to reduce the subsequent test effort• change of material.In the service phase, cost reduction can be achieved by optimum exploitation of part’s life potential. The means are improvement of the lifing concepts where portions of the crack propagation life may be utilised in addition to the traditionally cleared crack initiation life. Accurate records of life consumption can be obtained with modern systems for life usage monitoring.
Hypersonic missiles — some problem areas
Authors: East R. A. , Edwards J. A. 
Published: July 2016

AbstractAn overview of some of the problems, which have to be overcome in the design of hypersonic missiles or projectiles, is given. In the main, these are connected with the high levels of heat transfer rate suffered by such vehicles, particularly those induced by aerodynamic control surfaces. Some of the aspects of heat transfer, induced by, and suffered by such controls are presented. Data are presented and discussed, regarding the effects of flow separation due to flaps or flares, the effects of sharp and bluff fins (both swept and unswept). Finally, the aerodynamic interactions and heat transfer rates induced by reaction control jets are presented.
Inflight icing data gathering during routine flight operations — a case study
Authors: Brown A. P. 
Published: July 2016

AbstractFor the purpose of the design and certification of inflight icing protection systems for transport and general aviation aircraft, the eventual re-definition/expansion of the icing environment of FAR 25/JAR 25, Appendix C is under consideration. Such a re-definition will be aided by gathering as much inflight icing event data as reasonably possible, from widely-different geographic locations. The results of a 12-month pilot programme of icing event data gathering are presented. Using non-instrumented turboprop aircraft flying upon mid-altitude routine air transport operations, the programme has gathered observational data from across the British Isles and central France. By observing a number of metrics, notably windscreen lower-corner ice impingement limits, against an opposing corner vortex-flow, supported by wing leading edge impingement limits, the observed icing events have been classified as ‘small’, ‘medium’ or ‘large’ droplet. Using the guidance of droplet trajectory modelling, MVD values for the three droplet size bins have been conjectured to be 15, 40 and 80mm. Hence, the ‘large’ droplet category would be in exceedance of FAR/JAR 25, Appendix C.Data sets of 117 winter-season and 55 summer-season icing events have been statistically analysed. As defined above, the data sets include 11 winter and five summer large droplet icing encounters. Icing events included ‘sandpaper’ icing from short-duration ‘large’ droplets, and a singular ridge formation icing event in ‘large’ droplet. The frequency of ‘large’ droplet icing events amounted to 1 in 20 flight hours in winter and 1 in 35 flight hours in summer. These figures reflect ‘large’ droplet icing encounter probabilities perhaps substantially greater than previously considered. The ‘large’ droplet events were quite localised, mean scale-size being about 6nm.
Numerical studies of infrared signature levels of complete aircraft
Authors: Mahulikar S. P. , Sane S. K. , Gaitonde U. N. , Marathe A. G. 
Published: July 2016

AbstractThis paper begins with an outline of the procedure for predicting the infrared signature emissions from the airframe, engine casing, and the plume, and their attenuation by the intervening atmosphere. These emissions are contrasted against the background, to obtain the infrared signature levels. The infrared detector’s — noise equivalent flux density, is proposed as an operational constraint on the flight envelope. The shift of this newly imposed constraint on the flight envelope for several engine-operating conditions, and for turbojet and turbofan engines is studied. The signature levels from the casing and plume, of a turbofan and equivalent turbojet engine, are compared at different operating points on the flight envelope. Result in the form of a polar plot of infrared signature level variation with aspect is also examined for low flying missions. The results are analysed to direct stealth design and operation.
Compact analytic solutions for a decaying, precessing circular orbit
Authors: McInnes C.R. 
Published: July 2016

AbstractThe evolution of low Earth orbit satellites under the action of atmospheric drag and J2 oblateness perturbations has been widely investigated. Simple analyses describing the altitude decay of a circular orbit through energy arguments have also been widely available. This paper extends these simple analyses by providing compact analytic expressions for true anomaly and ascending node angle along with a more accurate expression for altitude decay. The resulting solutions then allow a fast and efficient method of investigating the orbital evolution of decaying, precessing circular orbits. Applications include the rapid evaluation of station-keeping budgets for both single platforms and the orbital evolution of satellite constellations. Passive station-keeping by continuous low thrust acceleration is investigated and shown to be naturally unstable.
An experimental study of dynamic stall on a finite wing
Authors: Coton F. N. , Galbraith R. A. McD. 
Published: July 2016

AbstractThis paper examines the dynamic stalling of a finite wing of aspect ratio 3·0 when subject to constant pitch motions up to and beyond stall. In particular, unsteady surface pressure data were obtained at 192 locations on the wing surface and these were then analysed to provide information on the nature and phasing of dynamic stall events in both the chordwise and spanwise directions. It was also possible to obtain sectional force and moment coefficients by integration of the pressures measured on specific chordal arrays. This provided valuable insight into the load distribution on the wing throughout the range of motion. On this basis, it was established that the wing loading distribution was consistent with conventional understanding of steady wing loading up to the incidence at which the dynamic stall vortex was initiated. Beyond this point, the formation and subsequent convection of the vortex structure was found to be strongly three-dimensional but, nevertheless, exhibited many of the features of two-dimensional dynamic stall.
Induced drag prediction for wing-tail and canard configurations through numerical optimisation
Authors: Lombardi G. , Vicini A. 
Published: July 2016

AbstractA computational procedure has been developed in order to predict aerodynamic interference between lifting surfaces, and to devise configurations which best meet given aerodynamic requirements. The procedure, which couples an aerodynamic solver with a numerical optimisation routine, is useful in the preliminary design of aircraft. The essential features of the aerodynamic code and of the optimisation routine are described, along with the coupling criteria. Some of the most significant predictions obtained in induced-drag minimisation for wing-tail and canard configurations are described and discussed.
Some reflections on trends in rotorcraft technology and configurations — into the 21st century
Authors: Balmford D.E.H. 
Published: July 2016

This series of lectures recalls the achievements of that outstanding pioneer of rotary wing flight Juan de la Cierva. At around the age of 23, he began to develop the concept of improved safety in flying machines, and included in his studies the concept of the helicopter. Having carried out many tests of various possible configurations, he discarded the concept of true helicopter flight as not being achievable with the then current state-of-the-art.However, he became convinced that his basic objectives of short takeoff and landing, and safe low speed flight could be achieved by replacing the wing of a conventional aircraft with an autorotating rotor.
Project review — do you really know where you are?
Authors: Balthazor L. R. 
Published: July 2016

AbstractProject reviews are carried out to enable the right decisions to be taken to achieve project objectives. However, these decisions are often taken on incomplete, optimistic, inaccurate, misleading or simply wrong information. Whilst incompleteness is inevitable with the complex and rapidly changing nature of high technology engineering projects, it is important that the project manager has a good appreciation of the extent to which these other factors may affect the progress information upon which judgements are made. This paper explores a few of the traps the author has come across, and suggests possible approaches to avoid some of them.A systems perspective is recommended, with a focus on risk management, resolving ambiguity, rapid response, trend analysis, earned value principles and taking account of the effects of organisational changes.
The Superorbital Expansion Tube concept, experiment and analysis
Authors: Neely A. J. , Morgan R. G. 
Published: July 2016

AbstractIn response to the need for ground testing facilities for super orbital re-entry research, a small scale facility has been set up at the University of Queensland to demonstrate the Superorbital Expansion Tube concept. This unique device is a free piston driven, triple diaphragm, impulse shock facility which uses the enthalpy multiplication mechanism of the unsteady expansion process and the addition of a secondary shock driver to further heat the driver gas. The pilot facility has been operated to produce quasi-steady test flows in air with shock velocities in excess of 13 km/s and with a usable test flow duration of the order of 15 μs. An experimental condition produced in the facility with total enthalpy of 108 MJ/kg and a total pressure of 335 MPa is reported. A simple analytical flow model which accounts for non-ideal rupture of the light tertiary diaphragm and the resulting entropy increase in the test gas is discussed. It is shown that equilibrium calculations more accurately model the unsteady expansion process than calculations assuming frozen chemistry. This is because the high enthalpy flows produced in the facility can only be achieved if the chemical energy stored in the test flow during shock heating of the test gas is partially returned to the flow during the process of unsteady expansion. Measurements of heat transfer rates to a flat plate demonstrate the usability of the test flow for aerothermodynamic testing and comparison of these rates with empirical calculations confirms the usable accuracy of the flow model.
An experimental study of transition and the development of turbulence in a linearly retarded boundary-layer flow
Authors: van Oudheusden B. W. 
Published: July 2016

AbstractAn experimental investigation was carried out of the incompressible boundary layer flow along a flat plate, in the presence of an adverse pressure gradient that corresponds to a linear retardation of the free stream velocity. The turbulence level in the free-stream was 0·12% and transition occurred with the laminar boundary layer being close to separation. For three values of the Reynolds number (2·56, 3·11 and 4·09 million based on the reference length that is defined as the reciprocal of the nondimensional-velocity gradient) the laminar, transitional and turbulent regions were studied by single (normal) hot-wire surveys at several streamwise positions. This allows the fluctuations of the streamwise velocity component to be followed from the amplification of laminar instability waves, through breakdown in the intermittency region, and the subsequent development towards a more or less developed turbulence structure. The study reveals that within the transition region fluctuation levels are reached throughout a large part of the boundary layer that are significantly higher than those in fully developed turbulent flow, which is partly a direct consequence of the intermittent character of the flow. For the highest Reynolds number additional cross-wire surveys were carried out in the turbulent region to observe the development of the turbulent stresses following transition. The data are interpreted in terms of structural coefficients, eddy viscosity and mixing length. Also, these results indicate that the transition process can be associated with turbulence levels well in excess of those occurring in fully developed turbulence, and reveal the relaxation of the outer region turbulence structure.
An introductory guide to literature in aeroelasticity
Authors: Battoo R. S. 
Published: July 2016

AbstractThis paper is meant primarily for non-specialist readers who may not be familiar with aeroelasticity. The main objective is to direct the reader to some important texts and papers that have been published in the areas which embrace aeroelasticity, from which the reader may gain sufficient knowledge about the subject. Since aeroelasticity is a large field which requires considerable knowledge in several related areas newcomers can often be daunted by the subject. This is further compounded by the great amount of published material available. This paper will assist the reader to locate key publications and help identify major works which have been useful in studying the subject. A comprehensive list of references is included which will help to identify key subject areas, researchers, research establishments and publications for further study.
Energy partitioning in high speed impact of analogue solid rocket motors
Authors: Schonberg W. P. 
Published: July 2016

AbstractModelling the response of solid rocket motors to bullet and fragment impacts is a high priority among the military services from standpoints of both safety and mission effectiveness. Considerable effort is being devoted to characterising the bullet and fragment vulnerability of solid rocket motors, and to developing solid rocket motor case technologies for preventing or lessening the violent responses of rocket motors to these impact loadings. Because full-scale tests are costly, fast-running analytical methods are required to characterise the response of solid rocket motors to ballistic impact hazards. In this study, a theoretical first-principles-based model is developed to determine the partitioning of the kinetic energy of an impacting projectile among various solid rocket motor failure modes. Failure modes considered in the analyses include case perforation, case delamination, and fragmentation of the propellant simulant material. Energies involved in material fragmentation are calculated using a fragmentation scheme based on a procedure developed in a previous impact study utilising propellant simulant material. The model is found to be capable of predicting a variety of response characteristics for analogue solid rocket motors under high speed projectile impact that are consistent with observed response characteristics. Suggestions are made for improving the model and extending its applicability to a wider class of impact scenarios.
Cone cavity flow at M = 8·2 with injection of air and helium
Authors: Bellone F. , Stollery J. L. 
Published: July 2016

AbstractAn experimental investigation of cone cavity flow at M = 8·2 with injection of air and helium has been performed in the Cranfield University gun tunnel. The cone used had a 10° semi-angle and incorporated an annular cavity. The boundary layer ahead of the cavity was laminar. The study concentrated on the effects of increasing the mass injected into the cavity.With no injection the external flow bridged the cavity. A shock wave and a pressure peak occurred at the rear face corner. By injecting gas, this pressure peak was decreased in intensity and a shock wave was formed at the front face corner. As the mass injected was increased, the shocks initially formed at the front and rear face corners were shifted upstream from their initial positions and boundary layer separation occurred ahead of the cavity. For the highest mass flow rate injected, the pressure peak at the rear face corner was very small. The cavity flow was never more than mildly unsteady.
The role of modelling and simulation in the development of advanced non-destructive evaluation systems
Authors: Generazio E. R. , Harris C. E. 
Published: July 2016

AbstractNon-destructive evaluation (NDE) technologies are a critical component of a collaborative engineering environment. The role of NDE simulations in component design, manufacturing, certification, integrity and repair are identified and discussed in the context of a futuristic intelligent synthesis environment (ISE) that facilitates collaborative engineering. Each of these critical areas needs to be simulated in a virtual reality environment and is expected to have a large effect on the cost, life, safety, and risk of aerospace products. In a collaborative engineering environment, NDE simulations will provide ‘real-time’ feedback to component designers and systems engineers. This feedback is necessary to achieve optimum overall system-level benefits.