bluuebunny/crossref_metadata_2025_split huggingface dataset:
Climate functions for the use in multi-disciplinary optimisation in the pre-design of supersonic business jet
Authors: Grewe V. , Stenke A. , Plohr M. , Korovkin V. D. 
Published: February 2016

AbstractMitigation of climate change is a challenge to science and society. Here, we establish a methodology, applicable in multi-disciplinary optimisation (MDO) during aircraft pre-design, allowing a minimisation of the aircraft’s potential climate impact. In this first step we consider supersonic aircraft flying at a cruise altitude between 45kfeet (~13·5km, 150hPa) and 67kfeet (~20·5km, 50hPa). The methodology is based on climate functions, which give a relationship between 4 parameters representing an aircraft/engine configuration and an expected impact on global mean near surface temperature as an indicator for the impact on climate via changes in the greenhouse gases carbon dioxide, water vapour, ozone and methane. These input parameters are cruise altitude pressure, fuel consumption, fuel flow and Mach number. The climate functions for water vapour and carbon dioxide are independent from the chosen engine, whereas the climate functions for ozone and methane depend on engine parameters describing the nitrogen oxide emissions. Ten engine configurations are taken into account, which were considered in the framework of the EU-project HISAC. An analysis of the reliability of the climate functions with respect to the simplified climate-chemistry model AirClim and a detailed analysis of the climate functions is given.
New methodology and code for Hawker 800XP aircraft stability derivatives calculation from geometrical data
Authors: Anton N. , Botez R. M. , Popescu D. 
Published: February 2016

AbstractThe new FDerivatives code was conceived and developed for calculating static and dynamic stability derivatives of an aircraft in the subsonic regime, based on its geometrical data. The code is robust and it uses geometries and flight conditions to calculate the aircraft’s stability derivatives. FDerivatives contains new algorithms and methods that have been added to DATCOM’s classical method, presented in a USAF Stability and Control DATCOM reference. The new code was written using MATLAB and has a complex structure which contains a graphical interface to facilitate the work of potential users. Results obtained with the new code were evaluated and validated with flight test data provided by CAE Inc. for the Hawker 800XP business aircraft.
Investigation of rotorcraft-pilot couplings under flight-path constraint below the minimum-power speed
Authors: Lu L. , Padfield G.D. , Jump M. 
Published: February 2016

AbstractIn some situations, closed loop control by the pilot can result in the combined pilot-aircraft system becoming marginally stable or even unstable. This can happen whether the pilot is controlling attitude or flight path. In this paper, an investigation into helicopter stability under flight-path constraint below the minimum-power speed is reported. The work provides a theoretical basis for flight path handling qualities criteria particularly for flight on the, so-called, back-side of the power curve. The research uses the theory of weakly coupled systems by partitioning the helicopter longitudinal dynamics to investigate three interacting subsystems – classically the surge mode, the phugoid mode and the heave mode. Under certain conditions, strong control of flight path or vertical speed is shown to drive the aircraft-pilot system unstable and a conflict is shown to exist between feedback gain values to guarantee stability of both the surge and the flight path motions. This conflict constitutes a potential source of adverse rotorcraft-pilot couplings. The problems are exacerbated in cases when the use of collective control is restricted. The phenomenon is explored in both ground based simulation and flight test to provide a verification of the theory.
Modelling ion propulsion plume interactions with spacecraft in formation flight
Authors: Kafafy R. , Cao Y. 
Published: February 2016

AbstractThis paper presents a simulation study of ion thruster plume effects on formation flying spacecraft. Two formation flight applications using micro-ion propulsion are considered: an L2-Halo orbit interferometer formation and a LEO micro-satellite formation. Worst case scenarios in both missions have been investigated. We focus our study on thruster configurations resulting in possible indirect plume impingement on satellites outside of the direct impingement zone. Indirect impingement which cannot be predicted except through plasma simulation or in-flight measurements might expose critical spacecraft elements such as optical sensors to a harsh contamination environment. A high-fidelity electrostatic plasma simulation code for parallel computing platforms was used in the study.In our study, we found that using miniature scale ion propulsion in both formation missions creates a very low charge-exchange plasma environment which results in tolerable contamination environment for other spacecraft in the formation.
Nonlinear transient analysis of moderately thick rectangular composite plates
Authors: Tanriöver H. , Şenoca E. 
Published: February 2016

AbstractThis paper presents an analytical-numerical methodology for the geometrically nonlinear analysis of laminated composite plates under dynamic loading. The methodology employs Galerkin technique, in which suitable polynomials are chosen as trial functions. In the solution process, Newmark’s scheme for time integration, and modified Newton-Raphson method for the solution of resulting nonlinear equations are used. In the formulation, first order shear deformation theory based on Mindlin’s hypothesis and von Kármán type geometric nonlinearity are considered. The results are compared to that of finite strips, and Chebyshev series published elsewhere. The method is found to determine closely both the displacements and the stresses. A finite element analysis has also been carried out for the validation of the results. The present method can be efficiently and easily applied for the nonlinear transient analysis of laminated composite plates with various boundary conditions.
Measurements of velocity Field in the wake of an oscillating wind turbine blade
Authors: Soltani M. R. , Mahmoudi M. 
Published: February 2016

AbstractA series of tests were carried out to study the unsteady wake behaviour behind an aerofoil which is a section of a wind-turbine blade. The model is oscillated in pitch about its quarter chord axis at various reduced frequencies, amplitudes, and mean angles-of-attack. Instantaneous and mean velocity profiles were obtained using total and static pressure at 35 vertically aligned points behind the aerofoil via two similar rakes. The rakes were located at a distance of 1·5 chord length behind the model. An estimation of the real time and average variations of the linear momentum deficit during the oscillation cycle is obtained and has been compared with the corresponding static data. The results show that oscillation amplitude and reduced frequency have pronounced effects on the wake characteristics.
Blended wing body structural concept development
Authors: Velicki A. , Thrash P. 
Published: February 2016

AbstractA lightweight robust airframe design is one of the key technological advancements necessary for the successful launch of a blended wing body aircraft. The non-circular pressure cabin dictates that substantial improvements beyond current state-of-the-art aluminium and composite structures is needed, and that improvements of this magnitude will require radically new airframe design and manufacturing practices. Such an approach is described in this paper. It is a highly integrated structural concept that is tailored and optimised to fully exploit the orthotropic nature and unique processing advantages inherent in dry carbon fibres, while also employing stitching to enable a unique damage-arrest design approach.
Improved test capabilities for cost-effective performance evaluation of airborne electronic warfare systems
Authors: Pywell M. , Midgley-Davies M. 
Published: February 2016

AbstractState of the art test capabilities are described that can enable optimised electronic warfare (EW) system development programmes for military air platforms. EW systems are key enablers of air platform survivability and the above is important as defence ministries and industry world-wide wrestle with affordability, technical and industrial challenges. The military end user needs improved capability quickly, with high availability; defence ministries want this at lowest possible cost and with minimum risk. Satisfying these requirements, while remaining in business against a background of fierce international competition and world financial crisis, is indeed challenging. Improvements are described that can enable improved technical performance and lower cost, time and risk programmes than hitherto, with emphasis on RF EW systems and the recent multi-£M upgrade to BAE Systems’ EW Test Facility, with its aircraft-sized anechoic chamber. This upgrade assures a further decade of world-class UK capability for testing manned and unmanned air platforms.
Evolution of generic flight vehicle design synthesis
Authors: Chudoba B. , Heinze W. 
Published: February 2016

AbstractWhen defining a new product like an aircraft, space access vehicle or space mission, the Advanced Projects Group evaluates the available design space and compares it with the design space required to accomplish the specified mission. As with any product development process, the general life-cycle characteristics are established first during the conceptual design (CD) phase, clearly before a design proposal can be released to the follow-on design phases such as preliminary design (PD), detail design (DD), flight test (FT), and finally operation and disposal. As a rule of thumb, it can be assumed that around 80% of the flight vehicle configuration and mission tandem are determined during the CD phase alone, which is the key phase where the initial brainstorming has to take place. Clearly, it is the responsibility of the CD team to simulate the entire life-cycle of the project from ‘cradle to grave’ where the focus is on correctness rather accuracy in order to identify the design space and offer an overall proof of design convergence. Currently, the important primary aerospace vehicle and mission design decisions at CD level are still made using extremely simple analysis and heuristics. A reason for this scenario is the difficulty in synthesising the range of individual design disciplines for both, classical and novel aerospace vehicle conceptual designs, in more than an ad hoc fashion. Although the CD segment is seen as the most important step in the product development phase due to its pre-defining function, it is the least well understood part of the entire product evolution process due to its level of abstraction. This paper presents the roadmap towards the next generation of aerospace life-cycle synthesis systems, a software and management process capable to immediately calculate cost and time implications while simultaneously linking design, manufacturing, testing, and operation. A historical review of how design has been accomplished until today is presented. The design approaches are categorised and the characteristics of today’s state-of-the-art design synthesis systems are discussed. A specification for the new class of intelligent generic design synthesis systems is presented capable of satisfying the demands imposed by the new breed of high-performance aircraft, space access vehicles, space missions, and others. Finally, the development status of the next generation aerospace vehicle design synthesis (AVDS-PrADO) simulation-based acquisition environment is presented.
Wake vortex encounters in a flight simulator
Authors: Allerton D. J. , Spence G. T. 
Published: February 2016

AbstractA real-time model of a wake vortex has been developed for an engineering flight simulator, which enables studies to be undertaken into the effects of wake vortex encounters with civil transport aircraft. A brief summary of the methods used to create a vortex model and integrate it with a real-time flight simulator is presented. Tools have been developed to determine the structural loads on an aircraft during a simulated wake vortex encounter and to visualise the airframe loads. Four wake vortex encounters were flown with different pilot recovery strategies and automatic flight controls. It is clear from analysis of these results that it is difficult for a pilot to appreciate the margin of tail loading during an encounter and a prototype training display is outlined to enable pilots to fully understand the effects of rudder inputs in recovery from these events.
The effect of gravity on a shaped sonic boom
Authors: Cain T. 
Published: February 2016

AbstractPreviously it was demonstrated that gravity is directly responsible for the attenuation of sonic booms as they propagate towards the ground, while the gradient in acoustic impedance has no effect on the wave strength. This was a significant departure from the well accepted acoustic theory and naturally led to questions concerning comparison with experiment and the implications for low boom design. This paper presents a comparison of measured ground signatures of the Northrup-Grumman Shaped Sonic Boom Demonstrator (SSBD) with a method of characteristics extrapolation from a close proximity flight measurement of static pressure under the aircraft. Comparison is also made with Whitham’s theory, extended to include gravity and the ambient temperature variation, as presented in the previous paper. The calculations are both in good agreement with the experimental ground signature. The usual equations that define the acoustic propagation (gravitational body force neglected) are transformed so that the computational algorithms of the extended Whitham theory are applicable. The transformation simplifies the acoustic model and reveals the conditions under which the errors in its prediction will be large. At the Mach number of 1.4, corresponding to the SSBD flight, the error is relatively small and the acoustic prediction is also in close agreement with the ground signature.
Mechanics and aerodynamics of perching manoeuvres in a large bird of prey
Authors: Carruthers A. C. , Thomas A. L. R. , Walker S. M. , Taylor G. K. 
Published: February 2016

AbstractThis paper reviews recent results on the mechanics and aerodynamics of perching in a large bird of prey, the Steppe Eagle Aquila nipalensis. Data collected using onboard and high-speed video cameras are used to examine gross morphing of the wing planform by the flight muscles, and smaller-scale morphing of the wing profile by aeroelastic deflection of the feathers, Carruthers et al. High-resolution still images are used to reconstruct the shape of the wing using multi-station photogrammetry, and the performance of the measured wing profile is analysed using a panel code, Carruthers et al. In bringing these lines of research together, we examine the role of aeroelastic feather deflection, and show that the key to perching in birds lies not in high-lift aerodynamics, but in the way in which the wings and tail morph to allow the bird to transition quickly from a steady glide into a deep stall.
Design support for metallic machined ribs using knowledge based engineering techniques
Authors: van der Laan T. , van Dalen F. , Vermeulen B. 
Published: February 2016

AbstractIn recent years increasingly pressure has been applied on aircraft component suppliers to reduce design lead-time and design cost of aircraft components. To achieve this reduction in lead-time and cost, advanced automation tools that automate part of the engineering process can be used. Knowledge based engineering (KBE) tools are one such automation tool type and automate part of the engineering process based on existing knowledge within a company. In this paper the development process and use of a KBE application to design machined ribs in an industrial setting is discussed. The development of the KBE tool has resulted in the standardisation of the design methodology. Furthermore it has reduced machined rib design lead-time in a project to develop a bussines jet empennage by 40%.
Modelling the flight dynamics of the hang glider
Authors: Cook M. V. , Spottiswoode M. 
Published: February 2016

AbstractThe 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.
Comparison of a grid-based CFD method and vortex dynamics predictions of low Reynolds number cylinder flows
Authors: Baranyi L. , Lewis R. I. 
Published: February 2016

AbstractComputational fluid dynamics models range from the finite difference type grid-based method to the Lagrangian style vortex cloud simulation technique for solving the Navier-Stokes equations. This paper undertakes a comparison of these two methods for the classical datum bluff body case of flow past a stationary circular cylinder at low Reynolds numbers in the range 10 to 220. Comparisons include time-history, time-mean and root-mean-square values of oscillating drag and lift coefficients, frequency of vortex shedding and related vortex street wake flow patterns. Particularly close agreement was obtained for Strouhal number versus Reynolds number, and good agreement for time-mean value of drag coefficients; comparison was also made with experimental results. Attempts are also made to calculate the skin friction and surface pressure components of the cylinder drag, revealing the significance of skin friction drag within this range and its relative insignificance above a Reynolds number of 220.
An unsteady, moving mesh CFD simulation for Harrier hot-gas ingestion control analysis
Authors: Richardson G. A. , Dawes W. N. , Savill A. M. 
Published: February 2016

Hot gas ingestion (HGI) can be a problematic feature of short take-off vertical landing (STOVL) aircraft during the descent phase of landing, or while on the ground. The hot exhaust gases from the downwards pointing nozzles can be re-ingested into the engine intakes, causing power degradation or reduced engine surge margin. The flow-fields that characterise this phenomenon are complex, with supersonic impinging jets and cross-flows creating large ground vortices and fountain up-wash flows.A flow solver has been developed to include a suitable linear mesh deformation technique for the descending aircraft configuration. The code has been applied to predict the occurrence of HGI, by simulating experimental results from a 1/15th scale model of a descending Harrier. This has enabled an understanding of the aerodynamic mechanisms that govern HGI, in terms of the near-field and far-field effects and their impact on the magnitude of temperatures at the engine intake.This paper presents three sets of CFD results. First a validation exercise shows predicted results from the twin-jet with intake in crossflow test-case. This is an unsteady Reynolds averaged Navier Stokes (URANS) solution for a static geometry (there is no moving mesh). This allows comparison with experiment. Secondly, a full descent phase URANS Spalart-Allmaras (SA) turbulence model calculation is done on an 8·5m cell mesh for half the flow domain of the Harrier model and test-rig without dams/strakes. This shows how the HGI flow mechanisms affect the engine intake temperature profiles, for the case where there are no flow control methods on the underside of the aircraft. Thirdly, the full descent phase URANS SA turbulence model calculation is done on a 22·4m cell mesh for the full flow domain of the Harrier model and test-rig, with the dam/strake geometry included in the structured mesh region.
Loss reduction on ultra high lift low-pressure turbine blades using selective roughness and wake unsteadiness
Authors: Howell R. J. , Roman K. M. 
Published: February 2016

This paper describes how it is possible to reduce the profile losses on ultra high lift low pressure (LP) turbine blade profiles with the application of selected surface roughness and wake unsteadiness. Over the past several years, an understanding of wake interactions with the suction surface boundary layer on LP turbines has allowed the design of blades with ever increasing levels of lift. Under steady flow conditions, ultra high lift profiles would have large (and possibly open) separation bubbles present on the suction side which result from the very high diffusion levels. The separation bubble losses produced by it are reduced when unsteady wake flows are present. However, LP turbine blades have now reached a level of loading and diffusion where profile losses can no longer be controlled by wake unsteadiness alone.The ultra high lift profiles investigated here were created by attaching a flap to the trailing edge of another blade in a linear cascade — the so called flap-test technique. The experimental set-up used in this investigation allows for the simulation of upstream wakes by using a moving bar system. Hotwire and hotfilm measurements were used to obtain information about the boundary-layer state on the suction surface of the blade as it evolved in time. Measurements were taken at a Reynolds numbers ranging between 100,000 and 210,000.Two types of ultra high lift profile were investigated; ultra high lift and extended ultra high lift, where the latter has 25% greater back surface diffusion as well as a 12% increase in lift compared to the former. Results revealed that distributed roughness reduced the size of the separation bubble with steady flow. When wakes were present, the distributed roughness amplified disturbances in the boundary layer allowing for more rapid wake induced transition to take place, which tended to eliminate the separation bubble under the wake. The extended ultra high lift profile generated only slightly higher losses than the original ultra high lift profile, but more importantly it generated 12% greater lift.
On different parameterisation methods to analyse spacecraft attitude manoeuvres in the presence of attitude constraints
Authors: Radice G. , Casasco M. 
Published: February 2016

AbstractThis paper analyses and compares two different attitude representations, using quaternions and modified Rodrigues parameters, in the context of the potential function method applied to autonomously control constrained attitude slew manoeuvres. This method hinges on the definition of novel Lyapunov potential functions in terms of the attitude parameters representing the current attitude, the goal attitude and any pointing constraints, which may be present. It proves to be successful in forcing the satellite to achieve the desired attitude while at the same time avoiding the pointing constraints. A linearised version of the modified Rodrigues parameterisation is also introduced and analysed. Finally advantages and drawbacks of all attitude representations are discussed.