bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation interoperability — where are the challenges?
Authors: Tomlinson B. N. 
Published: February 2016

AbstractThis paper will discuss and review the nature of simulation interoperability. It will analyse the scope of interoperability in terms of basic intercommunication features (technical interoperability), fitness for purpose (functional interoperability) and suitability for use in distributed training (training interoperability). Only technical interoperability has received close attention, through DIS and HLA standards. Other aspects still present many challenges. The ability to create a common ‘outside world’ database is frequently cited as the dominant component and principal challenge in any discussion of interoperability. While this is often true, this paper identifies how interactions among all participants in the shared operational space (‘battlespace’) should be the starting point in defining interoperability, these interactions of course being dictated by the training requirement. Interactions are accomplished through ‘sensors’, which could be the human eye, night vision goggles (NVGs), radios, data links, radar, FLIR etc. Comprehensive interoperability demands comparable levels of modelling among all participants, including the effect of the environment (whether terrain or meteorology) on the performance of each simulator’s sensor suite. The paper will identify these significant effects and discuss where simulation technology is challenged and needs to advance, particularly in the context of mission simulation of future joint (Air/Land/Maritime) operations. The paper concludes with some discussion of the way ahead, including how guidelines based on experience could augment the use of standards.
Interchanging simulation databases with third parties using SEDRIS
Authors: Harris R. 
Published: February 2016

AbstractSuccessful, seamless interchange of simulation databases has long proved surprisingly difficult to achieve. Numerous technical difficulties, arising from the different environmental representations used by different simulation systems, have proved to be only one facet of this difficulty. Often such problems are in fact the result of more fundamental underlying issues, such as the mathematical relationships between different co-ordinate systems. Logistical issues, and collaborative aspects of database interchange between different groups or companies, also contribute to the problems.Thales has encountered many of these issues over the years in generating a range of databases for its simulation systems. These databases are required to correlate closely with other sensor systems, in particular the visual, but it is often the case that these other systems are third party products, using databases modelled by companies other than Thales. In these circumstances, the strategy used by Thales to generate its databases has typically been to derive them directly from the visual database. This has involved directly processing the visual database, extracting relevant geometry and attribution and formatting it for use by the Thales simulation systems. Historically, such visual databases have been provided by third parties using the SIF/HDI interchange format and imported directly into the Thales database generation toolset. While generating such derived databases in this way has been achieved successfully, many interchange issues referred to above were encountered and needed to be addressed.When the need arose to replace SIF/HDI, the opportunity was taken to seek a replacement that would not only provide better representational capabilities but also address many of the wider, non-technical issues as well. Analysis of a variety of formats was undertaken and SEDRIS emerged as by far the strongest contender. Not only did it provide the best all round support for existing data representation requirements, it also gave good support for addressing wider interchange issues and offered a variety of opportunities to enhance the database generation toolset, both during initial development and over time.This paper will discuss experiences using SEDRIS in this context. It will examine the basic representational requirements that needed to be met and the interchange problems that were to be overcome. The ways in which SEDRIS was seen to address these problems will be considered, along with the other advantages SEDRIS offered. Experiences developing SEDRIS software and interchanging databases using SEDRIS will also be described, including some lessons learned concerning both the use of SEDRIS and database interchange in general.
Structural health monitoring systems – benefits and airworthiness issues
Authors: Lloyd P. A. 
Published: February 2016

AbstractIn recent years there has been an increasing interest in the application of advanced structural monitoring systems to aircraft structures. A great deal of research effort has, and is being directed towards technologies that can detect damage and estimate its significance. In this paper the benefits of deploying such systems are discussed and illustrated with quantitative estimates where these are available. It is concluded that significant benefits should accrue from their use, but that a number of outstanding technical issues remain which include the realistic verification of performance and reliability. The impact on aircraft airworthiness is also considered and it is suggested that while no significant new issues emerge, considerable work will need to be done to qualify systems, and that this is unlikely to be worthwhile unless the expected benefits can be assured.
On the aerodynamics of the Gloster E28/39 – a historical perspective
Authors: Brinkworth B. J. 
Published: February 2016

AbstractAs commissioned to demonstrate the feasibility of jet propulsion, the E28/39 needed to exceed the performance of contemporary fighters. But Carter, the chief designer, took the opportunity to look further ahead, and devised an aircraft in which the onset of compressibility effects was taken into account from the beginning of the design. Successful operation over a wide speed range required a shrewd synthesis of previous experience and practice with uncertain material emerging from the research domain. The resulting aircraft showed no significant aerodynamic vices, requiring only minor modifications from its first flight to its participation in diving trials, that took it into hitherto unexplored regions of high subsonic speed. It proved to be fully worthy of its pivotal role at the beginning of a new era in aeronautics.The aerodynamic features of Carter’s design are reviewed in relation to the limited state of knowledge at the time. Drawing upon fragmented material, much not previously published, this study enlarges upon, and in places amends, previous accounts of this notable machine.
The generation of sound in turbulent motion
Authors: Lilley G. M. 
Published: February 2016

AbstractThe present paper reviews and discusses the physical mechanisms of noise generation and reduction in turbulent flows with their applications towards aircraft noise reduction at takeoff and on the approach. This work began in 1948 when Lilley undertook an experimental investigation into the source of jet noise as a necessary precursor to finding methods for the reduction of high speed jet engine noise on civil jet airliners. Westley and Lilley completed this experimental programme in 1951, which included the design of a range of devices for high speed jet noise reduction. It was about this time that similar studies on jet noise were being started elsewhere and in particular by Lassiter and Hubbard in USA. The major contribution to the subject of turbulence as a source of noise came from Sir James Lighthill’s remarkable theory in 1952. In spite of the difficulties attached to theoretical and experimental studies on noise from turbulence, it is shown that with the accumulated knowledge on aerodynamic noise over the past 50 years, together with an optimisation of aircraft operations including flight trajectories, we are today on the threshold of approaching the design of commercial aircraft with turbofan propulsion engines that will not be heard above the background noise of the airport at takeoff and landing beyond 1-2km, from the airport boundary fence.It is evident that in the application of this work, which centres on the physical mechanisms relating to the generation of noise from turbulence and turbulent shear flows, to jet noise, there is not one unique mechanism of jet noise generation for all jet Mach numbers. This author in this publication has concentrated on what appears to be the dominant mechanism of noise generation from turbulence, where the mean convection speeds of the turbulence are subsonic. The noise generated at transonic and supersonic jet speeds invariably involves extra mechanisms, which are only briefly referred to here.
Computational aeroacoustics: The low speed jet
Authors: Avital E. J. , Alonso M. , Supontisky V. 
Published: February 2016

AbstractLow speed circular, elliptic and planar jets are investigated computationally for basic sound generation and hydrodynamics. The jets are assumed to be incompressible and are simulated using the large eddy simulation (LES) approach. The emitted sound is calculated using Lighthill’s acoustic analogy. Two formulations are used, Lighthill’s stress tensor formulation and Powell’s vortex sound formulation. A new boundary correction for Powell’s formulation is developed in order to account for the finite size of the computational domain. Low to moderate Reynolds number jets are simulated. Good agreement with known hydrodynamic results is achieved. This includes the nature of the transition process, e.g. enhanced mixing and axis switching in the elliptic jet and in some statistical results. The new boundary correction for Powell’s formulation proves to be vital in order to achieve good agreement with Lighthill’s formulation. Some success in high frequency prediction at least for the circular and elliptic jets is achieved in terms of getting the expected asymptotic behaviour. Both formulations show that the elliptic jet noise level is mildly lower than the circular jet noise level. Good to very good agreement is achieved in terms of directivities and frequency spectra with known results for the various jets.
Influence of the height of the vortex generators in the control of shock-induced separation of the boundary layers
Authors: Cohen G. S. , Motallebi F. 
Published: February 2016

AbstractExperiments have been conducted to assess the effects that sub-boundary-layer vortex generators (SBVGs) have on reducing normal shock-induced turbulent boundary-layer separation. The freestream Mach number and Reynolds number were M = 1·45 and 15·9 × 106/m, respectively. Detailed measurements of a fully developed, flat plate turbulent boundary layer were used in order to assess the performance of ten different SBVG configurations. The SBVG performance was assessed by comparing total pressure profiles measured upstream of separation and downstream of reattachment. Static pressure distributions, near surface total pressure distributions, oil flow visualisation and Schlieren photographs were also used. The effect of SBVG height was investigated. The results show the largest SBVGs with height,h= 55%δ, provided the greatest static pressure recovery and maximum mixing. However, the shock pressure rise (wave drag) was highest for this case.
A study of various energy- and exergy-based optimisation metrics for the design of high performance aircraft systems
Authors: Periannan V. , Spakovsky M. R. von , Moorhouse D. J. 
Published: February 2016

This paper shows the advantages of applying exergy-based analysis and optimisation methods to the synthesis/design and operation of aircraft systems. In particular, an Advanced Aircraft Fighter (AAF) with three subsystems: a Propulsion Subsystem (PS), an Environmental Control Subsystem (ECS), and an Airframe Subsystem – Aerodynamics (AFS-A) is used to illustrate these advantages. Thermodynamic (both energy and exergy based), aerodynamic, geometric, and physical models of the components comprising the subsystems are developed and their interactions defined. Off-design performance is considered as well and is used in the analysis and optimisation of system synthesis/design and operation as the aircraft is flown over an entire mission.An exergy-based parametric study of the PS and its components is first presented in order to show the type of detailed information on internal system losses which an exergy analysis can provide and an energy analysis by its very nature is unable to provide. This is followed by a series of constrained, system synthesis/design optimisations based on five different objective functions, which define energy-based and exergy-based measures of performance. The former involve minimising the gross takeoff weight or maximising the thrust efficiency while the latter involve minimising the rates of exergy destruction plus the rate of exergy fuel loss (with and without AFS-A losses) or maximising the thermodynamic effectiveness.A first set of optimisations involving four of the objectives (two energy-based and two exergy-based) are performed with only PS and ECS degrees of freedom. Losses for the AFS-A are not incorporated into the two exergy-based objectives. The results show that as expected all four objectives globally produce the same optimum vehicle. A second set of optimisations is then performed with AFS-A degrees of freedom and again with two energy- and exergy-based objectives. However, this time one of the exergy-based objectives incorporates AFS-A losses directly into the objective. The results are that with this latter objective, a significantly better optimum vehicle is produced. Thus, an exergy-based approach is not only able to pinpoint where the greatest inefficiencies in the system occur but appears at least in this case to produce a superior optimum vehicle as well by accounting for irreversibility losses in subsystems (e.g., the AFS-A) only indirectly tied to fuel usage.
Systematic review of the impact of emissions from aviation on current and future climate
Authors: Takeda K. , Takeda A. L. , Bryant J. , Clegg A. J. 
Published: February 2016

AbstractAviation emissions have an impact on the global climate, and this is consequently an active area of research worldwide. By adapting replicable and transparent systematic review methods from the field of evidence-based medicine, we aim to synthesise available data on the effects of aviation emissions on climate. From these data, we aim to calculate lower and upper bounds for estimates of the effect of aviation on climate in an objective manner.For the systematic review an appropriate protocol was developed and applied by two independent reviewers, to identify research that met the inclusion criteria. These included all aviation types, original research studies, climate models with aviation as a specific component, with outcomes for emissions, radiative forcing, global warming potential and/or surface temperature changes. These studies were prioritised and data extracted using a standard process. The 35 studies reviewed here reported radiative forcing, global warming potential and/or temperature changes as outcomes, allowing direct comparisons to be made.Tabulated results and a narrative commentary were provided for overall effects on climate, and the individual effects of carbon dioxide, water, contrails, cirrus clouds, ozone, nitrogen oxides, methane, soot and sulphur oxides. Lower and upper bounds for these effects, and their relative contributions compared to overall radiative forcing and surface temperature changes, have been described.This review shows that the most recent estimates for the contribution of aviation to global climate are highly dependent on the level of scientific understanding and modelling, and predicted scenarios for social and economic growth. Estimates for the future contribution of aviation to global radiative forcing in 2015 range from 5·31% to 8·04%. For 2050 the estimates have a wider spread, from 2·12% to 17·33%, the latter being for the most extreme technology and growth scenario. These global estimates should be considered within the context of uncertainties in accounting for the direct and indirect effects of different contributions. Variations between lower and upper bounds for estimates of radiative forcing are relatively low for carbon dioxide, around 131% to 800% for cirrus clouds effects, and 1,044% for soot. Advances in climate research, particularly in the area of contrail and cloud effects, has led to some revision of the 1999 IPCC estimates(1), and demonstrates that the research community is actively working to further understand the underlying science.The approaches assumptions, limitations and future work were discussed in detail. We have demonstrated how the systematic review methodology can be applied to climate science, in a replicable and transparent manner.
Experimental study of overexpanded co-flowing jets
Authors: Sharma H. , Vashishtha A. , Rathakrishnan E. , Lovaraju P. 
Published: February 2016

AbstractAn experimental investigation was carried out to find the effect of an annular co-flow jet on the primary supersonic jet from Mach 2 nozzle at different levels of overexpansion. In this study, a convergent-divergent circular nozzle of exit Mach number 2, surrounded by an annular convergent circular nozzle with an annular gap of 4·4mm was used. Nozzle pressure ratios (NPRs) 3, 4, 5, 6, 7 are investigated for overexpanded states of the primary jet and NPR 8 is investigated for almost correctly expanded state. The centreline pressure distributions were taken at all NPRs for both with and without co-flow case, to investigate the supersonic core extent and mixing activity in the jet field. In the radial direction pitot pressure at different axial locations at all NPRs for both the cases are measured to find the jet development and shadowgraph visualisation of jet structure was done to visualise the shock structure in near-field. It is found that the co-flow acts as mixing inhibitor at all levels of overexpansion for Mach 2 nozzle.
Distributed parameter control arithmetic for an axisymmetrical dual-mode scramjet
Authors: Tao C. , Daren Y. , Wen B. 
Published: February 2016

AbstractDual-mode scramjet is one of the candidates for hypersonic flight propulsion system which will be used in wide range of flight Mach numbers from 4 to 12 or higher, wherein dual-mode scramjet should be well designed to be suitable for subsonic/supersonic combustion operation according to the flight conditions. Therefore this system is required to operate in a finite number of operational modes that necessitate robust, stable, and smooth transitions between them by which selective operability of supersonic/subsonic combustion modes and efficient combustor operation in these modes may be realised. A key issue in making mode transition efficient and stable is mode transition control. The major problem in mode transition control is the handling of the various flow and combustion coupling effects of dual-mode scramjet whose physical states are spatially coupled and whose governing equations are partial differential equations. Involving these distributed parameter issues, our basic idea is using the shape control theory to study the control problems of mode transition for dual-mode scramjet with the aim of achieving the desirable design properties and increasing control reliabilities. This specific approach is motivated by the promise of novel techniques in control theory developed in recent years. Concrete control arithmetic of this approach, such as shape control model, sensitivity analysis and gradient-based optimisation procedure, are given in this paper. Simulation results for an axisymmetric, wall-injection dual-mode scramjet show the feasibility and validity of the method.
Flight mechanics of a free-wing tilt-body aircraft
Authors: Ro K. , Kamman J. W. , Barlow J. B. 
Published: February 2016

AbstractThe free-wing tilt-body aircraft refers to a vehicle configuration in which the wing, fuselage, and empennage are in a longitudinally articulated connection. This allows the main wing to freely rotate relative to the body, while the empennage, which is in the form of a long twin boom connected to the rear of the body, changes its incidence angle relative to the body in response to external commands. The principal advantages claimed for the configuration are short takeoff and landing capability, and reduced gust sensitivity. The aerodynamics of the free-wing tilt-body configuration has been previously studied, but analysis of its flight mechanics is limited. In this paper we present derivations of the flight dynamic equations of motion using multi-body dynamic modelling techniques, and combine the resulting equations of motion with experimental aerodynamic data to achieve a nonlinear mathematical model for flight simulation of a generic free-wing tilt-body vehicle. The mathematical model is suitable for the study of detailed dynamic characteristics as well as for model based control law synthesis. Key flight performance, and stability and control characteristics of a generic configuration are obtained from the mathematical model.
Experimental investigation of the aerodynamic characteristics of generic fan-in-wing configurations
Authors: Thouault N. , Breitsamter C. , Adams N. A. , Gologan C. , Seifert J. 
Published: February 2016

AbstractThis experimental investigation concentrates on the aerodynamic behaviour of a generic fan-in-wing configuration. The effects of the fan(s) on the flow circulation in a short take-off and landing or a transition flight condition without ground effect are evaluated. A wind-tunnel model has been constructed and tested to quantify the aerodynamic effects. Force measurements, surface pressure measurements, stereo-particle image velocimetry and wool tufts flow visualisation are performed. Different fan-in-wing configurations with the fans rotating in the wing plane, one fan either at the rear or front part of the wing and two fans are compared to the closed wing without fans set as reference. A fan placed near the trailing edge improves significantly the lift coefficient due to a jet flap effect on the wing lower side combined with enhanced suction on the wing upper side. The jet exiting the nozzle rolls up in a counter rotating pair of vortices affecting significantly the wing behaviour.This experimental investigation constitutes also a useful database for further CFD comparison.