bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aeroelasticity analysis of a bird-damaged fan assembly using a large numerical model
Authors: Imregun M. , Vahdati M. 
Published: July 2016

AbstractBird strike is a major consideration when designing fans for civil aero engines. Current methods rely on impact tests and structural optimisation but it is highly desirable to have predictive numerical models to assess the aerodynamic and aeroelastic stability of bird-damaged fan assemblies. A detailed feasibility study towards such a prediction capability, consisting of a CFD solver coupled to a finite element representation of the structure, is reported in this paper. A whole-assembly model was used for both the fluid and the structural domains, an approach necessitated by the loss of cyclic symmetry due to one or more blades undergoing plastic deformation under the effect of the bird impact. It was assumed that two consecutive blades had suffered unequal amount of bird damage, the so-called heavy and medium-damaged blades.
Simulation of parallel blade–vortex interaction using a discrete vortex method
Authors: Qian L. , Vezza M. 
Published: July 2016

AbstractNumerical results are presented for two-dimensional vortex-aerofoil interaction using a grid-free discrete vortex method. The effects of the passing vortex on the surface pressure distribution and hence the aerodynamic force and moment of the aerofoil are examined in detail for a variety of interaction geometries. For some head-on interaction cases, vortex-induced local flow separation is also predicted on the aft part of the aerofoil surfaces. Extensive comparisons are made with other numerical results and the results from the Glasgow University BVI wind-tunnel test, which show good agreement.
Optimisation of air-jet vortex generators with respect to system design parameters
Authors: Bray T. P. , Garry K. P. 
Published: July 2016

AbstractA simple technique is proposed that allows the definition of the geometry and characteristics of an air-jet vortex generator to be defined, using the system requirements in practical design. Typically, the aircraft designer is concerned with the mass flow-rate and air pressure requirements of any pneumatic system for inclusion to an airframe. These parameters are not congruent with those for air-jet vortex generator aerodynamic design, and therefore, some tool is required to bridge the gap.Such a tool is proposed, based on empirical methods for the prediction of air-jet vortex generator behaviour. The technique allows the comparison of the vortex strength, and the system inputs (the jet mass flow-rate and the air-jet plenum pressure) for the air-jet, for a range of jet nozzle diameters and jet velocity ratios. Through this comparison, the optimum air-jet design can be reached for a given system input.
A case for multi-level optimisation in aeronautical design
Authors: Robinson G. M. , Keane A. J. 
Published: July 2016

AbstractThis paper discusses how the inevitable limitations of computing power available to designers has restricted adoption of optimisation as an essential design tool. It is argued that this situation will continue until optimisation algorithms are developed which utilise the range of available analysis methods in a manner more like human designers. The concept of multi-level algorithms is introduced and a case made for their adoption as the way forward. The issues to be addressed in the development of multi-level algorithms are highlighted.The paper goes on to discuss a system developed at Southampton University to act as a test bed for multi-level algorithms deployed on a realistic design task. The Southampton University multi-level wing design environment integrates drag estimation algorithms ranging from an empirical code to an Euler CFD code, covering a 150,000 fold difference in computational cost. A simple multi-level optimisation of a civil transport aircraft wing is presented.
Computations of bladerow stall inception in transonic flows
Authors: He L. , Ismael J. O. 
Published: July 2016

AbstractA three-dimensional unsteady Navier-Stokes solver has been used to simulate stall inception in a single row ten passage segment of a transonic fan, the NASA rotor-67. At subsonic flow conditions, the 3D results illustrate a rotating stall inception with short scale part-span cells rotating at around 80% rotor speed, similar to that observed in some low speed experiments. However, at a supersonic relative inflow condition, the results show that an isolated blade row tends to stall in a one-dimensional breakdown pattern without first experiencing rotating stall. At near-stall conditions, significant self-excited unsteadiness is generated by the interaction between the tip-leakage vortex and the passage shock wave. Further computations for two-dimensional configurations indicate that it is possible to have a rotating pattern of instability in transonic blade rows associated with circumferential synchronised shock oscillation.
Effect of heat transfer on periodic transonic flows
Authors: Mitchell D. A. , Cooper R. K. , Raghunathan S. 
Published: July 2016

AbstractThe effects of the model surface to free stream adiabatic temperature ratio(Tw/Tad)on periodic transonic flow over a 14% thick biconvex aerofoil are evaluated using a computational fluid dynamic approach. The analysis is based on the thin layer Navier Stokes equations with Baldwin-Lomax turbulence model. The results of computations showed that on biconves aerofoils there is a large effect of heat transfer on instantaneous pressure distributions and periodic buffet excitation level confirming some of the available experimental data. The effects observed have an implication in wind tunnel measurement of buffet associated periodic transonic flows.
Alleviation of pitch-up on delta wings using distributed porosity
Authors: Traub L. W. , Moeller B. , Galls S. F. 
Published: July 2016

AbstractAn experimental investigation was undertaken to determine the effectiveness of distributed surface porosity for the alleviation of pitch-up on a delta wing. Tests were undertaken using a 65° sweep delta wing with distributed porosity evaluated at various locations on the wing. Force balance, on and off surface flow visualisation and flow field surveys using a multi-hole probe were undertaken. The data shows that distributed porosity applied along the wing leading edge at the apex is effective in eliminating pitch-up whilst incurring a minimal performance cost. Trailing edge porosity generally degraded performance.
Control and handling qualities considerations for an advanced supersonic transport aircraft
Authors: Steer A. J. , Cook M. V. 
Published: July 2016

AbstractA future advanced supersonic transport aircraft (AST) has fundamental characteristics and problems inherent to supersonic cruise aircraft with corresponding unique control and handling characteristics.In order to optimise the aerodynamic performance across the full flight envelope a fully integrated flight and propulsion control system will be required. However, this will need to be designed from the outset within clearly defined flight control and performance guidelines.Relevant existing and AST specific handling qualities criteria will need to be developed if a successful commercial transport aircraft is to be produced.This paper begins by presenting an overview of existing supersonic transport (SST) aircraft operations and current second generation SST research activities and design considerations. This is followed by an analysis of the principal aerodynamic, dynamic and control characteristics of SST and AST aircraft and their effect on the aircraft’s handling qualities. Finally, some possible solutions to the control and handling issues are investigated, assessed and presented.
The design challenge of high altitude long endurance (Hale) unmanned aircraft
Authors: Jones R. I. 
Published: July 2016

AbstractThe requirement for an aircraft to operate in the thin atmosphere at high altitudes for long periods provides a particular challenge to all areas of aeronautical engineering. This is reflected in a range of difficulties encountered when attempting to design aircraft for this type of operation.This paper first considers the reasons for adopting an unmanned solution for high altitude long endurance (Hale) aircraft. It then indicates how the demands of Hale operations lead to problems in applying the design approach taken for more common aircraft types. Some of the work performed at the College of Aeronautics (CoA), in attempting to address the problem areas for the design process and produce initial designs for a range of Hale unmanned aircraft (UMA) types, is then reviewed. The lack of data/methods to allow the prediction of Hale UMA structure mass, engine performance at high altitudes and aerodynamic parameters for low Reynolds number operation and high aspect ratio configurations are identified as particular problems. However, initial design, based on standard approaches, has been shown to be possible, provided caution is exercised.
Development and assessment of computer methods for three-dimensional turbulent boundary layers
Authors: Wu J. , Müller U. R. 
Published: July 2016

AbstractThis paper describes the development of a finite difference method that solves the boundary-layer equations for three-dimensional compressible turbulent flows. The most prominent achievements are the employment of a Newton technique for the simultaneous solution of all governing equations, an option to choose an algebraic or ak-εeddy-viscosity turbulence model, and the flexible use of curvilinear coordinates. The method is validated by comparisons with a number of experimental and theoretical data sets of three-dimensional, compressible and incompressible, steady and unsteady boundary layers. In parallel, the performance of a three-dimensional compressible industrial integral boundary-layer technique is evaluated by comparisons with experimental test cases and with the results of the field method.
Parallel implementation of an upwind Euler solver for hovering rotor flows
Authors: Allen C. B. , Jones D. P. 
Published: July 2016

AbstractAn Euler method for computing compressible hovering rotor flows is described. The equations are solved using an upwind finite-volume method in a blade-fixed rotating co-ordinate system, so that hover is a steady problem. Transfinite interpolation, along with a periodic transformation, is used to generate grids for the periodic domain. Computation of these flows to an acceptable accuracy requires fine grids, and a long integration time for the wake to develop, resulting in excessive run times on a single processor. Hence, the method is developed as a multiblock code in a parallel environment, and various aspects of data passing and communication between processors have been considered. It is shown that a considerable increase in performance is available from the use of non-blocking and asynchronous communication. It is also demonstrated that increased performance may be available by balancing the residual levels rather than the number of cells on each processor.
Finite-state aerodynamic modelling for gust load alleviation of wing–tail configurations
Authors: Gennaretti M. , Ponzi C. 
Published: July 2016

AbstractA finite-state aerodynamics methodology is proposed for the analysis of the forces generated by a gust. To illustrate and assess the methodology, gust-response and gust-alleviation applications are included. Finite-state aerodynamics denotes a technique to approximate aerodynamic loads so as to yield an aircraft model of the type ẋ = Ax + Bu (state-space formulation). In this paper, a finite-state formulation is proposed to include the presence of a gust. The aerodynamic loads to be approximated are evaluated here by using a frequency-domain boundary-element formulation; the flow is assumed to be irrotational except for a zero-thickness vortex layer (wake). The gust-alleviation application consists of determining a control law for reducing the response to a vertical gust disturbance, as measured by the centre of mass acceleration. Two optimal-control approaches are considered for the synthesis of the control law: one uses the classical linear-quadratic regulator (LQR), whereas the second includes the additional feed-forward of the gust velocity ahead of the aircraft. Deflections of ailerons and elevators are assumed to be the control variables. Numerical results deal with responses to both a deterministic ‘1 – cosine’ gust distribution and a stochastic von Kármán spectrum. They indicate that the finite-state aerodynamic model proposed is capable of approximating, with a high level of accuracy, both the aerodynamic loads induced by the aircraft kinematics variables and those induced by the control variables, over a wide frequency range.
Shock phenomena in high speed aerodynamics: still a source of major concern
Authors: Délery J. M. 
Published: July 2016

AbstractShockwaves are present in a flow as soon as the Mach number becomes supersonic. Being viscous phenomena, Shockwaves are a source of drag which can be predominant when the Mach number is significantly higher than one. In supersonic air intakes, the production of entropy by shocks is felt as a loss in efficiency. At high Mach numbers, Shockwaves produce a considerable temperature rise leading to severe heating problems, complicated by real gas effects. The intersection - or interference - of two shocks gives rise to complex wave patterns containing slip-lines and associated shear layers whose impingement on a nearby surface can cause detrimental pressure and heat transfer loads. The impact of a Shockwave on a boundary layer is the origin of strong viscous interactions which remain a limiting factor in the design of transonic wings, supersonic air intakes, propulsive nozzles and compressor cascades. More effort is needed to improve prediction of these interactions and to devise new techniques to control such phenomena.
The effect of wing planform shape on dynamic stall
Authors: Coton F. N. , McD. Galbraith R. A. , Green R. B. 
Published: July 2016

AbstractThis paper examines the dynamic stalling of three wing planforms and characterises the main features of the stalling process in each case. The particular data were obtained during a three year research programme in the Department of Aerospace Engineering, University of Glasgow to collect high-resolution unsteady pressure data on the dynamic stalling characteristics of finite wing planforms. In this study, which was motivated by the pressing need for a greater understanding of the strongly three-dimensional effects in the tip region of helicopter rotors, the three wing planforms considered were a straight rectangular wing, a rectangular wing with swept tips and a delta wing. The initial test programme was followed by a further three years of detailed analysis and interpretation of the test data. Results from this analysis are presented in the present paper for cases in which the wings were subject to ramp motions.
Helicopter encounters with aircraft vortex wakes
Authors: Padfield G. D. , Turner G. P. 
Published: July 2016

AbstractThis paper presents the results of a study into wake vortex-related safety issues associated with simultaneous rotary and fixed-wing aircraft operations at busy airports. An analysis conducted using both simple analytic models and high fidelity FLIGHTLAB simulations has considered a helicopter located in the hover above the landing point and during approach and landing. Tip vortices from a Boeing 747 are shed and are assumed to be travelling in a horizontal plane by the time they reach the helicopter. A worst case scenario is simulated, with no vortex ageing or attenuation due to ground effect.Bothsimple and high fidelity simulations indicate that the rates of climb and descent induced by the vortex tails can be significant. When the helicopter flies through the vortex core, moderately large transient excursions in attitude occur within a few seconds. When the helicopter does not pass through or close to the core, while the flight path perturbations are still significant, the attitude response is shown to be significantly reduced. The predicted cyclic control power required to counteract the vortex-induced hub moments is about 40% of full control, compared with more than 100% for an ‘equivalent’ fixed-wing aircraft. The control power required in the vertical, collective, axis to overcome the downdraught and updraught in the vortex tails can be as high as 15–20%. While the authors have not tried to make judgements as to whether pilots would find the transients manageable, an approach to quantifying the extent of the hazard has been suggested using the failure transients criteria from the handling qualities performance standard ADS–33. Combined with analysis of the likelihood of such occurrences at particular airports, such response criteria offer a rational approach to developing safety cases for simultaneous operations.
“Putrid Boils and Sores, and Burning Wounds in the Body”: The Valorization of Health and Illness in Late Antique Manichaeism
Authors: Baker-Brian Nicholas 
Published: July 2016

Recent publications concerned with attitudes to the human body in the religion of Mani have revealed a complex spectrum of ideas. A reading of the “Manichaean body” informed by a gnostic polarity of flesh versus spirit has been largely rejected, and a more complex, ambivalent portrayal of the body, shaped by specific cosmological and theological readings of its origin and purpose, has come to light. New interpretive tools and approaches have changed perceptions of classical texts and revealed how the “subjugated, perfected [Manichaean body was] put into use in the process of salvation.” For example, rereading chapter 70 of the Coptic work theKephalaia of the Teacher, we encounter a complex lesson that betrays the Manichaeans’ understanding of the dual heritage of the human body. Here the Mani of theKephalaiainstructs his disciples about the correspondences that exist between the fleshly body and the universe and formulates them in a manner that suggests a simultaneous patterning of the two forms: “Mani says to his disciples: ‘This whole universe, above and below, reflects the pattern of the human body; as the formation of this body of flesh accords to the pattern of the universe’” (70.169.28–170.1). The organs and limbs of the body resemble specific astral structures and elements in the universe, and both body and universe are afflicted by a range of competing powers. Chapter 70 offers a melothesiac reading of these archontic powers as zodiacal signs fused with the organs, bones, and sinews of the body (cf. chapter 69). As archons they exercise a malevolent influence over the flesh. However, they are also constantly in conflict with each other, and the cause of bodily sickness lies in their “creeping, and moving within the body. . . [where] they shall beset and destroy one another. . . they shall erupt from the body of the person who will die; and make putrid boils and sores and burning wounds in the body” (70.175.12–14, 16–18). Leaving such colorful descriptions of lesions aside, chapter 70 also indicates that human beings, specifically the Manichaean elect, possess enormous potential as the ones who are able to facilitate the release of the “light” by subduing the activities of the “five camps” (i.e., the face, heart, genitalia, stomach, and ground).
3.6. AGN variability studies: an agenda for the next millenium?
Authors: Ulrich M.-H. 
Published: July 2016

Data which are obtained today can be re-acquired better and faster in the future. Their only enduring value, after they have been interpreted, is as historical markers. With electronic archiving one can envision archives covering decades, centuries and even longer periods of observations of selected objects or classes of objects. Such a data base would allow the study of phenomena with low temporal frequencies, and of rare events.First hints of such phenomena in AGN have been discovered recently: 1) The Seyfert 1s, the best studied AGN at present, exhibit flux variations on time scales ranging from hours to several years (see Ulrich et al. 1997). The faster variations (up to months) have been extensively observed, and they are best understood as being caused by magnetic flares in the corona above the central part of the accretion disk (Blandford and Payne 1982). The origin of the long term and large amplitude UV/optical flux variations (factor 20 in several years as observed in NGC4151 and F9), however, remain essentially unknown.
3.22. Star formation properties of barred galaxies
Authors: Kandalyan Rafik , Kalloghlyan Arsen 
Published: July 2016

The main results of this study can be summarized in the following:
(a)Magnitude-limited complete sample of barred galaxies was constructed. Space density of barred and unbarred galaxies at low luminosity range (M >-20) almost the same. At the high (M<-20) luminosity range about 30% of the galaxies are barred ones.(b)Bars do not have obvious influence on active nuclei. Presence or absence of bars does not related with the large scale galaxy environment.(c)Barred spirals, on average, have significantly higher relative star formation rate than that do unbarred galaxies.(d)Barred spirals exhibit tight correlations between FIR, radio and X-ray luminosities, while for unbarred spirals these luminosities do not correlated, which indicates on enhanced star formation activity in barred galaxies.(f)Group and non-group barred galaxies may differ by star formation activity.
X-Ray Observations of Galaxy-Quasar Associations
Authors: Arp H. 
Published: July 2016

Five examples of close associations of quasars with bright, low redshift galaxies have been observed in X-ray wavelengths with ROSAT. In three cases where the galaxies are detected strongly, the nuclei of the galaxies have X-ray extensions in the direction of the adjacent quasars.In all cases the active galaxies and quasars are located at the origin of apparent lines or pairs of X-ray sources, some involving filamentary X-ray connections to fainter quasars or candidate blue stellar objects. Brighter X-ray sources in these fields are found to be in excess of average survey values. The filaments and connections have measured fluxes of 1 ≲FX≲60 × 10−13erg cm−2s−1and they tend to radiate more strongly in the harder end of the 0.1-2.4 keV energy band.The most surprising result is the evidence that X-ray sources of optically diverse character are linked together in lines and extended filaments. Because of the rapid decay time of the high energy X-ray radiation, it is implied that we are observing some ongoing process possibly related to matter creation or emergence.
Background Radiation: Probes and Future Tests
Authors: Rees Martin J. 
Published: July 2016

The clearest evidence for the ‘hot big bang’ is of course the microwave background radiation. Its spectrum is now known, from the FIRAS experiment on COBE, to be a very precise black body – indeed, the deviations due to high-z activity, hot intergalactic gas, etc are smaller than many people might have expected. Also the light element abundances have remained concordant with the predictions of big bang nucleosynthesis, thereby giving us confidence in extrapolating back to when the universe was a few seconds old (see Copi, Schramm and Turner 1994 for a recent review). These developments give us grounds for greater confidence in this model than would have been warranted ten years ago. Several things could have happened which would have refuted the picture, but they haven't happened. For instance:(i)Objects could have been found where the helium abundance was far below 23 per cent.(ii)The background spectrum at millimetre wavelengths could have been weaker than a black body with temperature chosen to fit the Rayleigh-Jeans part of the spectrum.(iii)A stable neutrino might have been discovered in the mass range 100eV-1MeV.