bluuebunny/crossref_metadata_2025_split huggingface dataset:
A strategic European approach to aerodynamics research, technology and development
Authors: Dexter P.C. 
Published: July 2016

AbstractIn spite of the best intentions of many national and international funding agencies, much of the research and technology development (RTD) activity undertaken in Europe over the past few years has often been duplicating the work of others and has not resulted in an increase in capability in key areas. This is not to denigrate the work that has been undertaken — but have we done the right work? The EC-funded Thematic Network ‘Targeted Research Action in Aerospace Aerodynamics’, (TRA3), has been initiated with the broad aims of improving collaboration between existing EC- supported projects and, more importantly, attempting to put in place a long-term strategy for European aerospace aerodynamics RTD. TRA3 is, amongst other things, attempting to answer three key questions:• What are the important aerodynamic technologies?• What is the European aerospace industry’s current capability in these areas?• In which areas should Europe be investing to maintain a competi tive aerodynamics capability?The major benefit and output expected from TRA3 is the creation of a co-ordinated European aerodynamics RTD programme. The TRA3 Management Board consists of seven people who represent a cross-section of the European aerospace industry and research establishments, together with a Project Officer from the European Commission. This Management Board is tasked with formulating long-term plans for nine ‘Key Technology Areas’ that encompass all of the important aerodynamic technologies. This paper outlines the progress that has been made in meeting the very ambitious initial aims of the demanding work programme.
On (civil) aviation future(s)
Authors: Bushnell D. M. 
Published: July 2016

This is the latest in the series of invited survey articles and has been written in his own imimitable style by Dennis Bushnell, Chief Scientist at the NASA Langley Research Center. Dennis is well known for his far-sighted and often controversial views. He gave the 1998 Wilbur and Orville Wright lecture at the Royal Aeronautical Society and an edited abbreviation of that talk was published in the January 1999 issue of Aerospace International. In this paper Dr Bushnell amplifies and extends the vision of his earlier work. We arc delighted to publish his forecast for civil aviation and would welcome any comments on the projects described.John Stollery, Editor
Aeroservoelastic simulation by time-marching
Authors: Djayapertapa L. , Allen C. B. 
Published: July 2016

AbstractThe coupling of independent structural dynamic and inviscid aerodynamic models, in the time domain, is considered. The accuracy and CPU requirements of the two common approaches, namely ‘weak’ and ‘strong’ coupling procedures, are investigated. It is found that the strong coupling scheme is more accurate than the weak coupling approach, and only for large real time-steps is the strong coupling scheme more expensive. The computational method developed is used to perform transonic aeroelastic and aeroservoelastic calculations in the time domain, and used to compute stability (flutter) boundaries of 2D wing sections. A control law is implemented within the aeroelastic solver to investigate active means of flutter suppression via control surface motion. Comparisons of open and closed loop calculations show that the control law can successfully suppress the flutter and results in a significant increase in the allowable speed index in the transonic regime. The effect of structural nonlinearity, in the form of hinge axis backlash is also investigated. The effect is found to be destabilising, but the control law is shown to still alleviate the destabilising effect.
A new moving-boundary algorithm with application to SRM internal ballistics
Authors: Karimian S. M. H. , Amoli A. 
Published: July 2016

Abstract
In this paper a new moving-boundary algorithm is presented for the solution of two-dimensional flows on unstructured grids. Application of this algorithm is investigated by simulating the internal ballistics of solid rocket motors (SRM). Solution domain is discretised to a number of triangular elements using control-volume based finite-element (CVFE) method. Euler equations are integrated over the control volumes, and Roe's flux-difference scheme is used to evaluate flux vectors at the control-volume surfaces. To eliminate numerical errors due to grid movement, geometric conservation laws (GCL) are carefully implemented. The present algorithm recognises locations along the moving boundaries where the stretched elements result in a distorted grid. To avoid this, new elements are inserted through a local re-triangulation of elements in these regions. Internal ballistics of three SRMs with cylindrical grains burning from inside, are numerically simulated. Using a heat transfer model, erosive burning is included in calculation of propellant burning rate. The aftend of third SRM is tapered to demonstrate capability of present algorithm in solving problems with moving boundaries approaching each other. Very good agreement is observed between the time variations of head-end chamber pressure, obtained from the present work and the other methods.
Integrated air data sensors
Authors: Menzies M. A. 
Published: July 2016

AbstractAvionics Specialties in partnership with Honeywell has developed an integrated air data pressure sensor known as the integrated multi-function probe (IMFP). This continuously flow-aligned pressure-sensing device was developed using a multidisciplinary design approach encompassing computational fluid dynamic, (CFD), flow analysis, and experimentation. The computational investigation was performed using the finite element code, CFDesign, by Blue Ridge Numerics and consisted of pressure distribution studies for varying flows around conical sections. The application and integration of this technology to previously developed flow alignment and pressure transducing products lead to design similarity analysis saving considerable development time. Initial experimentation used to develop and refine the design and analysis consisted of laboratory bench testing, low and high-speed wind tunnel investigations, and subsonic flight-testing. Final performance verification was accomplished through data reduction and analysis of an extensive flight test program using a Lockheed Martin F-16 Fighting Falcon. The analysis, design and performance verification of this innovative pressure-sensing device was investigated for direct comparison to conventional Pitot-static performance with particular emphasis toward military fighter aircraft applications.
The world of regional aircraft — challenges and opportunities
Authors: Summerfield P. H. 
Published: July 2016

SummaryThe regional air transport industry is slowly emerging from the ravages of a prolonged structural recession. Long term survival in an industry which has traditionally traded in one of the world's most aggressive market places, will impose enormous demands upon everyone involved. Those regional aircraft manufacturers and operators who are brave enough to take advantage of emerging technologies, adjust to new processes and develop highlyskilled and motivated people will be best equipped to meet the global demands of the marketplace in an ever-changing world.The actions and achievements of Avro International Aerospace, a division of British Aerospace, with its Regional Avroliner family of aircraft provides an example through which to identify the key components in this process. The challenges facing the regional aircraft industry are identified, together with the resulting business opportunities and the significance of Government support, in order to draw appropriate conclusions with respect to the likely future of the industry.
Turbulence structure manipulation in a channel flow by outer layer devices
Authors: Iuso G. 
Published: July 2016

AbstractAn experimental study has been performed manipulating a fully developed turbulent channel flow, by means of blade manipulators known as outer layer devices (Olds). A large amount of investigation has been performed for boundary layer flow, whereas little research is available for internal flow manipulation. The influence on drag reduction for different configurations (single and tandem) and for some geometric parameters (distance from the wall and blade gap), have been analysed. Reynolds number effect has also been investigated. Some of the mechanisms involved in the skin friction reduction process are examined, in terms of time-space integral scales, Reynolds stresses and spectral analysis. Results show better efficiency for tandem configurations. These give high local skin friction reductions, up to 20%, which are strongly dependent on the manipulator distance from the wall, but have very little dependence on the blade gap and Reynolds number. Turbulence analysis displays reduced fluctuations in all three directions — as with space-time integral scales. Evidence of suppression for the large structures is also shown by spectral analysis. From a global balance it has been verified that no net drag reduction is obtained due to the additional drag introduced by the manipulators.
Airspace design: a conflict avoidance model emphasising pilot communication and perceptual capabilities
Authors: Fulton N. L. 
Published: July 2016

AbstractAirspace is identified through well defined volumes of the Earth's atmosphere. Airspace control is defined to consist of rules and procedures by which aircraft conduct their flight and by which aircraft approach and cross volume boundaries. Airspace control should optimise the flow of traffic under the constraint that no collision occurs. To date, the design of airspace control has been largely heuristic. Two fundamentally opposed philosophies and designs have evolved over the last fifty years. There has been little, if any, formal comparison of the relative performance of these designs.A new conceptual conflict-avoidance model is presented showing the need to maintain situational awareness for all conflicts. It reveals the essential requirement for communication channels in the conflict avoidance function. Human perceptual performance is related the required system response to conflict. These human factors can be mathematically related to physical parameters embodied in airspace rules and procedures. The impact of changes in airspace performance due to variations in physical parameters derived from models of the communication channels can now be measured. Use of the conflict-avoidance model presented in this paper identifies serious deficiencies in present designs and postulates that fundamental architectural changes are required to reduce safety hazards and produce designs of sufficient reliability, particularly for uncontrolled airspace. Designs based on stable and adequate communications are shown to be required and are now technologically feasible.
An Euler correction method for computing two-dimensional unsteady transonic flows
Authors: Das D. , Santhakumar S. 
Published: July 2016

AbstractAn Euler correction method is developed for unsteady, transonic inviscid flows. The strategy of this method is to treat the flow-field behind the shock as rotational flow and elsewhere as irrotational flow. The solution for the irrotational flow is obtained by solving the unsteady full-potential equation using Jameson's rotated time-marching finite-difference scheme. Clebsch's representation of velocity is followed for rotational flow. In this representation the velocities are decomposed into a potential part and a rotational part written in terms of scalar functions. The potential part is computed from the unsteady full potential equation with appropriate modification based on Clebsch's representation of velocity. The rotational part is obtained analytically from the unsteady momentum equation written in terms of Clebsch variables. This method is applied to compute the unsteady flow-field characteristics for an oscillating NACA 64A010 aerofoil. The results of the present calculation are found to be in good agreement with both Euler solution and experimental results.
Turbulence modelling for supercritical flows including examples with passive shock control
Authors: Sedaghat A. , Ackroyd J. A. D. , Wood N. J. 
Published: July 2016

AbstractThe aerodynamic performance of supercritical aerofoils at transonic speeds is strongly influenced by the shock wave-boundary-layer interaction. Passive shock control is one of the techniques used for controlling the undesirable effects of strong shock wave-boundary-layer interaction leading to extensive separation. Using passive shock control, the stall margin is increased and the onset of buffeting is delayed. Passive shock control is modelled by introducing a closed plenum chamber underneath a perforated surface at the foot of the shock wave where a combination of blowing and suction is generated. As a result, a strong normal shock wave is changed into a series of weak shock waves with lambda shape. Since the Baldwin-Lomax turbulence model has been used extensively for passive shock control modelling, which exhibits poor predictability for separated flows, an attempt has been made to modify the Reynolds normal stresses for this model so as to improve the accuracy of numerical results for flows with separation. Further modification to the Baldwin-Lomax model has been employed so that the mass transpiration effects are taken into account for the passive shock control computations. In this paper, a brief description on an implicit finite-volume TVD scheme in general coordinates is given and the details of the Balwin-Lomax turbulence model and its modifications are presented. The validated numerical results for several RAE 2822 aerofoil problems plus corresponding results for the modelled methods are presented and compared with some experimental data and other numerical results.
Combustion instability in a small liquid rocket motor
Authors: Osherov A. , Natan B. 
Published: July 2016

AbstractAn experimental investigation of high frequency combustion instability in a liquid rocket engine of 3kN thrust was conducted. The diagnostic method of detecting combustion instability was based on the measurement of the dynamic pressure following an artificial disturbance in the combustion chamber. Test data spectral analysis was performed by using the stochastic vibration data processing method. Although the engine has demonstrated an absence of tendency to spontaneous instability, insufficient stability of the original engine design was evident during tests with artificial triggers. A Helmholtz type resonator in form of partitioned cavities tuned to a few different, close frequencies was designed and installed in the combustion chamber wall to avoid spontaneous or triggered combustion instability. The experimental results from hot tests with artificial triggers confirmed the high efficiency of the applied acoustic resonator.
Aerodynamic simulation of heat shield separation test on ground
Authors: Chakraborty D. , Vasantha S. 
Published: July 2016

AbstractThe ability of a CFD technique to evaluate the performance of a heat shield separation system has been demonstrated. The evolution of the differential pressure across the heat shield surface has been estimated. The results of the analysis have been compared with the data from the separation test of the heat shield of an Indian launch vehicle. The pressure on the heat shield surface was estimated by solving the Navier Stokes equations using the Eulerian Lagrangian formulation. The results, which show good agreement with the observed results of a heat shield separation test on the ground, were found to be adequate for design purposes.
Tuning the axial singularity method for
accurate calculation of potential flow around
axisymmetric bodies
Authors: M. F. Zedan  
Published: July 2016

AbstractThe performance of axial line singularity methods has
been investigated systematically for various
solution parameters using carefully chosen test
cases. The results indicate that increasing the
number of elements and using stretched node
distribution improves the solution accuracy until
the matrix becomes near-singular. The matrix
condition number increases with these parameters as
well as with the order of intensity variation and
profile thickness. For moderate fineness ratios, the
linear methods outperform zero-order methods. The
linear doublet method performs best with control
points at the x-locations of nodes while the source
methods perform best with control points mid-way
between nodes. The doublet method has a condition
number an order of magnitude lower than the source
method and generally provides more accurate results
and handles a wider range of bodies. With
appropriate solution parameters, the method provides
excellent accuracy for bodies without slope
discontinuity. The smoothing technique proposed
recently by Hemsch has been shown to reduce the
condition number of the matrix; however it should be
used with caution. It is recommended to use it only
when the solution is highly oscillatory with a
near-singular matrix. A criterion for the optimum
value of the smoothing parameter is proposed.
A demonstration of the effect of the testing environment on unsteady aerodynamics experiments
Authors: Green R. B. , Galbraith R. A. McD. 
Published: July 2016

AbstractThe effects of windtunnel constraint during low speed unsteady aerodynamic experiments are assessed by comparing the data from two Naca 0015 models, one with a chord length of half the other. Ramp-up and ramp-down tests are considered, to distinguish between the effects of constraint upon separation and attachment. The unsteady separation process measured in terms of the normal force, pitching moment and stall vortex convection speed, is virtually unaffected by the difference in constraint between the two models, whereas the attachment process, assessed in terms of the normal force response and attachment behaviour, is sensitive to the size of the model.
A new approach to adaptive-wall windtunnel testing
Authors: Fakas E. , Bernstein L. 
Published: July 2016

SummaryA technique is described whereby experiments may be conducted on models which are geometrically similar to only part of the full scale configuration with the windtunnel walls being contoured to simulate the flow over that part. In this way, higher spatial resolutions can be achieved in a windtunnel of moderate size. The method is demonstrated by studying the effects of tip geometry on the flow over a wing of aspect ratio 15 using a half wing model of chord 500 mm projecting 1031 mm into a test section of width 1200 mm.
An investigation of dynamic stall through the application of leading edge roughness
Authors: Green R.B. , Galbraith R.A.McD. 
Published: July 2016

AbstractThe dynamic stall characteristics of a NACA 0015 performing ramp-up motions are considered. Pressure data show the development and convection of structures at the leading and trailing edges, which indicate differing degrees of what are described as leading edge and trailing edge stall mechanisms. When a transition strip is placed at the leading edge, the characteristics of leading edge stall predominate, and the growth of the structure at the trailing edge is suppressed. In addition the stall vortex convection speed is observed to alter significantly, which is interpreted as a change in the vortex origin, size, strength and trajectory.
Constrained on-board attitude control using gas jet thrusters
Authors: Radice G. , Mclnnes C. R. 
Published: July 2016

AbstractThis paper analyses a new approach utilising potential functions to autonomously control constrained attitude slew manoeuvres using gas jet thrusters. The method hinges on defining a potential function from the geometric configuration of the satellite's current attitude, the final target attitude and any pointing constraint which may be present. It will be demonstrated that complex path shaping and planning can be achieved using little computational effort. The method is mathematically validated using Lyapunov's theorem, and so can be considered for safety critical applications.
Experimental evaluation of multivariable rotor control schemes
Authors: Mullen G. J. , Brinson P. R. 
Published: July 2016

AbstractThe performance and robustness of a classical multivariable controller and one H∞ compensator are assessed on a model rotor rig. Both control schemes are subjected to sinusoidal and step input tests in the pitch and roll axes under a range of operating conditions and configurations. A brief description of the characteristics of the rotor mathematical model is provided, followed by a summary of the design assessment criteria. Following a description of the two control law design techniques, the performance of each controller is verified on the mathematical model prior to evaluation on the rotor rig. In absolute terms, there is a poor correlation between the simulated and experimental values of the design assessment criteria for both controllers. However, in relative terms, the H∞ control law achieves higher levels of damping and lower cross-couplings than the classical scheme although the measured improvements are not as substantial as predicted. In experimental frequency response tests at increasing advance ratios and various rotorspeeds, the H∞ scheme again consistently achieves the lowest levels of cross-coupling. In summary, the results show that although there are practical performance and robustness benefits to be gained by employing more complex control algorithms, model uncertainty will substantially reduce the predicted benefits.
The contribution of fatigue usage monitoring systems to life extension in safe life and damage tolerant designs
Authors: Irving P. E. , Strutt J. E. , Hudson R. A. , Allsop K. , Strathern M. 
Published: July 2016

AbstractFatigue usage monitoring systems (Fums) offer considerable potential for life extension of aircraft parts. In this work the life extension benefits of Fums is assessed by adopting a probabilistic approach. The roles of damage law type and of service usage variability is explored. It is shown by analysis that in the absence of cycle to cycle load interaction effects, load sequence has no effect on eventual life in either linear or non linear damage laws, provided that the function describing the rate of damage growth has separable variables of stress and damage. This condition includes fracture mechanics crack growth laws. Monte Carlo simulations have been conducted of fatigue life distributions in helicopter rotor components. Variability in manoeuvre damage, when summed over a large number of manoeuvres, has little effect on scatter in overall lives. A fixed manoeuvre usage spectrum will result in very small scatter in lives, whereas keeping the usage constant for each helicopter and allowing it to vary between helicopters, produces a significantly increased variability. The influence of load factors on life is also assessed. The extent of possible maintenance credits is discussed together with the use of Bayesian updating to make optimum use of both prior design data and current loads or damage information provided by Fums.