bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrail avoidance in the aircraft design process
Authors: Noppel F. , Singh R. 
Published: February 2016

AbstractAs aviation is one of the fastest growing industrial sectors world wide, air-traffic emissions are projected to increase their stake in the contribution to global warming. According to studies, both carbon dioxide and contrails are the principal air-traffic pollutants, whereas the impact from contrails in terms of radiative forcing is possibly larger than that of all other air-traffic pollutants combined. New regulations with the objective of mitigating contrail occurrences might cause a change in the design requirements of aircraft. In light of this, a method considering contrail formation during the aircraft design process is presented in this paper. Aircraft performance and optimisation is carried out with NASA’s flight optimisation system. Combining historical meteorological data with air-traffic data enables an assessment regarding contrail formation. As an example, a particular aircraft type in terms of range, speed and payload is optimised for minimum block fuel consumption considering different altitudes. The change in contrail formation in terms of contrail-km formed is calculated. The results suggest that if aircraft of the considered class were designed for higher altitudes, contrail occurrences would diminish slightly at a non-negligible fuel burn penalty.
Trajectory optimisation of an aerobatic air race
Authors: Plas H. van der , Visser H. G. 
Published: February 2016

AbstractThis paper deals with the synthesis of optimal trajectories for aerobatic air races. A typical example of an air race event is the Red Bull Air Race World Series, where high-performance aerobatic aircraft fly a prescribed slalom course consisting of specially designed inflatable pylons, known as ‘air gates’, in the fastest possible time. The trajectory that we seek to optimise is based on such a course. The air race problem is formulated as a minimum-time optimal control problem and solved in open-loop form using a direct numerical multi-phase trajectory optimisation approach based on collocation and non-linear programming. The multiphase feature of the employed collocation algorithm is used to enable a Receding-Horizon optimisation approach, in which only a limited number of manoeuvres in sequence is considered. It is shown that the Receding-Horizon control approach provides a near-optimal solution at a significantly reduced computational cost relative to trajectory optimisation over the entire course. To avoid the path inclination singularity in the equations of motion based on Euler angles, a point-mass model formulation is used that is based on quaternions. Numerical results are presented for an Extra 300S, a purpose-designed aerobatic aircraft.
VSTOL Aircraft market analysis
Authors: Howarth D. K. 
Published: February 2016

AbstractThis paper describes the market for air vehicles that offer Very Short Take Off and Landing (VSTOL) capabilities, also known as VSTOL aircraft. A commercial VSTOL aircraft will only succeed if it provides profits to both manufacturers and airlines. Being able to operate out of shorter fields offers airlines greater flexibility and therefore provides a benefit to the airline. However, adding VSTOL performance also adds cost. Successful VSTOL aircraft designs must balance the added cost against the additional benefits VSTOL performance will provide.The first problem in any new VSTOL design is determining what field length provides the maximum benefit relative to cost. In order to be able to determine this one needs to know not only what it will cost to design and build the new aircraft, but its value to the airlines, as reflected by the demand for it and the price they are willing to pay. Only then is it possible to design the aeroplane the market wants at a sustainable price and in sufficient quantities to optimise the manufacturer’s return on investment.This paper is a comprehensive parametric analysis of helicopters and aeroplanes that shows how much the market values short field performance by determining how much airline customers have been paying for it and how the market reacts to changes in its price. The analysis simultaneously considers over 230 currently produced models of fixed wing and rotary commercial aircraft, ranging in size from a Cessna 172 to an Airbus A380 and with balanced field lengths ranging from less than 150 to over 10,500ft.The data show that a single, statistically significant demand curve exists for all of these vehicles, with prices that range across several orders of magnitude. This curve consists of several segments or sub-markets including those for regional and rotary wing aircraft. Both of those markets offer vehicles over a wide range of prices. The analysis shows that VSTOL price is a function of the balanced field length provided by the vehicles within these market segments. Comparing demand and sustained price against cost reveals particular field lengths for which it will be possible to make a profit building VSTOL aircraft.Because the sustained price for a VSTOL aircraft is a function of its field length performance, and the quantity of a model sold is a function of its price, it follows that it is possible to predict the profit potential for a given VSTOL design in advance of its development. A thorough study of potential configurations therefore offers manufacturers the ability to design VSTOL aircraft that provide the maximum possible profit while fully satisfying the requirements of their airline customers.
Wind tunnel testing of powered lift, all-wing STOL model
Authors: Collins S. W. , Westra B. W. , Lin J. C. , Jones G. S. , Zeune C. H. 
Published: February 2016

AbstractShort take-off and landing (STOL) systems can offer significant capabilities to warfighters and, for civil operators thriving on maximising efficiencies they can improve airspace use while containing noise within airport environments. In order to provide data for next generation systems, a wind tunnel test of an all-wing cruise efficient, short take-off and landing (CE STOL) configuration was conducted in the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) 14ft by 22ft Subsonic Wind Tunnel. The test’s purpose was to mature the aerodynamic aspects of an integrated powered lift system within an advanced mobility configuration capable of CE STOL. The full-span model made use of steady flap blowing and a lifting centerbody to achieve high lift coefficients. The test occurred during April through June of 2007 and included objectives for advancing the state-of-the-art of powered lift testing through gathering force and moment data, on-body pressure data, and off-body flow field measurements during automatically controlled blowing conditions. Data were obtained for variations in model configuration, angles of attack and sideslip, blowing coefficient, and height above ground. The database produced by this effort is being used to advance design techniques and computational tools for developing systems with integrated powered lift technologies.
Dependence of radiated sound frequency on vortex core dynamics in multiple vortex interactions
Authors: Zheng Z. C. , Li W. 
Published: February 2016

AbstractWith both theoretical analysis and measurement data, it has been identified previously that there exists a robust sound emission from a pair of counter-rotating aircraft wake vortices at the frequency of unsteady vortex core rotation. In a vortex system with multiple vortices, the sound emission frequency can be subjected to change because of interactions among the vortices. The behaviour of the influence, indicated by the ratio between the core size and the distance of the vortices and the underlining vortex core dynamic mechanisms, is investigated in this study. A vortex particle method is used to simulate the vortex core dynamics in two-dimensional, inviscid and incompressible flow. The flow field, in the form of vorticity, is employed as the source in the far-field acoustic calculation using a vortex sound formula. Cases of co-rotating vortices and a multiple-vortex system composed of two counter-rotating vortex pairs are studied for applications to aircraft wake vortex sound. The study shows, without vortex merging, individual frequencies can be clearly identified that are due each to core rotation (self induction) and co-rotating motion of a vortex centre around the other (mutual induction). The ratio of the core size and the distance between vortices does not seem to significantly influence the frequency of vortex core rotation. With vortex merging, a single frequency due to the merged vortex core is generated.
The leading-edge vortex and aerodynamics of insect-based flapping-wing micro air vehicles
Authors: Wilkins P. C. , Knowles K. 
Published: February 2016

AbstractThe aerodynamics of insect-like flapping are dominated by the production of a large, stable, and lift-enhancing leading-edge vortex (LEV) above the wing. In this paper the phenomenology behind the LEV is explored, the reasons for its stability are investigated, and the effects on the LEV of changing Reynolds number or angle-of-attack are studied. A predominantly-computational method has been used, validated against both existing and new experimental data. It is concluded that the LEV is stable over the entire range of Reynolds numbers investigated here and that changes in angle-of-attack do not affect the LEV’s stability. The primary motivation of the current work is to ascertain whether insect-like flapping can be successfully ‘scaled up’ to produce a flapping-wing micro air vehicle (FMAV) and the results presented here suggest that this should be the case.
Effect of aft wall slope on cavity pressure oscillations in supersonic flows
Authors: Vikramaditya N. S. , Kurian J. 
Published: February 2016

AbstractAn experimental study of supersonic flow over wall mounted cavities with different aft wall angles is carried out. Unsteady pressure measurements were made on the walls and floor of the cavity. Data analysis was performed on the experimental results using statistical methods. In the case of higher angled cavities, the presence of an upstream traveling acoustic wave could be confirmed. For lower angled cavities (60 degrees and less) where the acoustic wave could not be identified, the flow inside the cavity was more or less stable. Mode switching occurring in higher angled cavities was confirmed by spectrogram studies.
A new model for optimal TF/TA flight path design problem
Authors: Zardashti R. , Bagherian M. 
Published: February 2016

AbstractThis paper focuses on the three dimensional flight path planning for a UAV on a low altitude terrain following/terrain avoidance mission. Using an approximate grid-based discretisation scheme, we transform the continuous optimisation problem into a search problem over a finite network, and apply a variant of the shortest-path algorithm to this problem. In other words using the three dimensional terrain information, three dimensional flight path from a starting point to an end point, minimising a cost function and regarding the kinematics constraints of the UAV is calculated. A network flow model is constructed based on the digital terrain elevation data (DTED) and a layered network is obtained. The cost function for each arc is defined as the length of the arc, then a constrained shortest path algorithm which considers the kinematics and the altitude constraints of the UAV is used to obtain the best route. Moreover the important performance parameters of the UAV are discussed. Finally a new algorithm is proposed to smooth the path in order to reduce the workload of the autopilot and control system of the UAV. The numeric results are presented to verify the capability of the procedure to generate admissible route in minimum possible time in comparison to the previous procedures. So this algorithm is potentially suited for using in online systems.
Impact damage and repair of composite structures
Authors: Falzon B. G. 
Published: February 2016

AbstractThis paper gives an overview of the work carried out in a GARTEUR (Group for Aeronautical Research and Technology in Europe) program, under the chairmanship of the author, to develop and validate analytical and numerical methods to characterise real impact damage in composite structures, particularly those designed to sustain load in a postbuckled state, and to study the durability of bonded repairs. GARTEUR is an inter-governmental agreement between the seven European countries with the largest direct employment in the Aerospace industry, to mobilise scientific and technical knowledge between the member countries. A number of Action Groups have been launched, since GARTEUR’s inception in the early 1970s, to address specific technical issues of interest to the participating members. The research presented in this paper was performed under Action Group 28 with partners from ONERA, EADS-CCR (France), DLR, AIRBUS-Deutschland, EADS-M (Germany), CIRA (Italy), INTA (Spain), SICOMP, Saab, (Sweden), NLR (The Netherlands), QinetiQ, BAE Systems, Imperial College London and the University of Sheffield (United Kingdom). The Action Group tasks were divided into four Work Elements (WEs): WE1-Prediction and characterisation of impact damage, WE2-Postbuckling with delamination, WE3-Repair and WE4-Fatigue. This paper outlines the main developments and achievements within each Work Element.
A causal factors analysis of helicopter accidents in New Zealand 1996-2005 and the United Kingdom 1986-2005
Authors: Majumdar A. , Mak K. , Lettington C. , Nalder P. 
Published: February 2016

AbstractHelicopter accidents cause many fatalities, and their avoidance is a major area of work for Civil Aviation safety authorities around the World. This paper uses helicopter accident data from the United Kingdom between 1986 and 2005 for 566 accidents and from New Zealand between 1996 and 2006 for 230 accidents to analyse helicopter accidents according to five categories of causes: airworthiness failure (engine); airworthiness failure (non-engine), operational failure, maintenance failure and mixed failure (i.e. operational and airworthiness combined). Factors associated with accidents, e.g. the engine types and weights of the helicopters involved; the nature of the operations and the phase of flight of the helicopter are also analysed. Operational failures were further analysed by Human Factors Analysis and Classification Scheme (HFACS) and airworthiness failures by a logical scheme of helicopter components. The results indicate that operational failures, especially due to unsafe acts, are the major cause of accidents in both countries followed by airworthiness causes. Light single piston helicopters are by far the major group associated with accidents in both countries, with few accidents for twin turbine helicopters. The majority of accidents were in non-public operations with few in public operations and in both countries, the cruise/flight/circuit phase has the largest number of accidents. Further analyses indicated statistically significant associations: type of helicopter and the cause of accidents; type of helicopter and the phase of flight; cause of accidents and nature of flights; cause of accidents and phase of flights; training flights and inadequate supervision; landing and procedural error and cruise and attention failure.
Improved models for runway debris lofting simulations
Authors: Nguyen S. N. , Greenhalgh E. S. , Iannucci L. , Olsson R. , Curtis P. T. 
Published: February 2016

AbstractNumerical models used to simulate the lofting mechanisms of runway stones were developed to assess the threat to aircraft structures from runway debris impacts. An inflated aircraft tyre model, which was validated by comparison with experimental indentation tests, showed that over-rolling of stones under typical take-off conditions led to only modest vertical loft velocities of less than 5 m/s. Experiments using a drop weight impactor simulated a section of aircraft tyre descending upon stones. These tests demonstrated that lofting was achieved for impacts with low rubber thickness. However, for impacts with greater rubber thickness, lofting was suppressed. Using more realistic tyre geometries resulted in launches with backspin, but only horizontally along the ground in the direction of the tyre axis. The speed at which launches occurred was proportional to the rate of descent of the tyre section and would consequently determine the loft speeds due to potential asperity lofting.
Supersonic boundary-layer interactions with various micro-vortex generator geometries
Authors: Lee S. , Loth E. 
Published: February 2016

AbstractVarious types of micro-vortex generators (μVGs) are investigated for control of a supersonic turbulent boundary layer subject to an oblique shock impingement, which causes flow separation. The micro-vortex generators are embedded in the boundary layer to avoid excessive wave drag while still creating strong streamwise vortices to energise the boundary layer. Several different types of µVGs were considered including micro-ramps and micro-vanes. These were investigated computationally in a supersonic boundary layer at Mach 3 using monotone integrated large eddy simulations (MILES). The results showed that vortices generated from μVGs can partially eliminate shock induced flow separation and can continue to entrain high momentum flux for boundary-layer recovery downstream. The micro-ramps resulted in thinner downstream displacement thickness in comparison to the micro-vanes. However, the strength of the streamwise vorticity for the micro-ramps decayed faster due to dissipation especially after the shock interaction. In addition, the close spanwise distance between each vortex for the ramp geometry causes the vortex cores to move upwards from the wall due to induced upwash effects. Micro-vanes, on the other hand, yielded an increased spanwise spacing of the streamwise vortices at the point of formation. This resulted in streamwise vortices staying closer to the floor with less circulation decay, and the reduction in overall flow separation is attributed to these effects. Two hybrid concepts, named ‘thick-vane’ and ‘split-ramp’, were also studied where the former is a vane with side supports and the latter has a uniform spacing along the centreline of the baseline ramp. These geometries behaved similar to the micro-vanes in terms of the streamwise vorticity and the ability to reduce flow separation, but are more physically robust than the thin vanes.
Towards Integrated design of fluidic flight controls for a flapless aircraft
Authors: Crowther W. J. , Wilde P. I. A. , Gill K. , Michie S. M. 
Published: February 2016

AbstractFluidic flight controls enable forces and moments for flight vehicle trim and manoeuvre to be produced without use of conventional moving surface controls. This paper introduces a methodology for the design of Circulation Control (CC) and Fluidic Thrust Vectoring (FTV) as fluidic controls for roll and pitch. Work was undertaken as part of the multidisciplinary FLAVIIR project, with the goal of providing full authority fluidic flight controls sufficient for a fully flapless flight of an 80kg class demonstrator aircraft known as DEMON. The design methodology considers drag, mass, volume and pneumatic power requirements as part of the overall design cost function. It is shown that the fundamental flow physics of both CC and FTV are similar, and hence there are strong similarities to the design approach of each. Flight ready CC and FTV hardware has been designed, manufactured and ground tested. The CC system was successfully wind tunnel demonstrated on an 85% scale half model of the DEMON. The design condition of a control ΔCL of 0·1 was achieved with a blowing coefficient of 0·01, giving a useable control gain of 10. The FTV system was static tested using a micro gas turbine source. The control characteristic was ‘N’ shaped, consisting of an initial high gain response in a negative sense (gain = −30) followed by a low gain response in a positive sense (gain = +3) at higher blowing rate. CC and FTV control hardware directly contributes to around 6% to the overall mass of the flight vehicle, however provision of pneumatic power carries a significant mass penalty unless generated as part of an integrated engine bleed system.
Supersonic aerodynamics of a projectile with slot cavities
Authors: Ibrahim A. , Filippone A. 
Published: February 2016

AbstractThis paper presents the results of experimental and computational investigations on the effect of slot cavities on a supersonic projectile. Experimental work was carried out to show the effects of the slots on the drag at Mach numbers M = 1·36, 1·65, 1·83. The computational analysis was done at M = 1·36. A single configuration of the slot pattern was used with two different slot widths (0·5mm and 2·0mm). Flow features were investigated in the slotted area and at the base. The analysis presented includes the pressure distribution, the supersonic cavity flow and the effect of the slots on the overall aerodynamic drag. Unlike the case of slots at transonic speeds, the suction and blowing mechanism is not found at supersonic Mach numbers. Streamwise cavity slots cause a small base drag reduction. The reduction in total drag is modest when the width is 0·5mm. However, the experiments showed that with the wider slots (2mm) the drag actually increases at Mach numbers from 1·36 to 1·83.
Validation study for prediction of iced aerofoil aerodynamics
Authors: Marques S. , Badcock K. J. , Gooden J. H. M. , Gates S. , Maybury W. 
Published: February 2016

AbstractIce accretions can significantly change the aerodynamic performance of wings and rotor blades. Significant performance degradation can occur when ice accreations cause regions of separated flow, to predict this change implies, at a minimum, the solution of the Reynolds-Averaged Navier-Stokes equations. This paper presents validation for two generic cases involving the flow over aerofoil sections with added synthetic ice shapes. Results were obtained for two aerofoils, namely the NACA 23012 and a generic multi-element configuration. These results are compared with force and pressure coefficient measurements obtained in the NASA LTPT wind-tunnel for the NACA 23012, and force, PIV and boundary-layer measurements obtained at DNW for the multi-element case. The level of agreement is assessed in the context of industrial requirements.
Recent extensions and applications of the ‘CST’ universal parametric geometry representation method
Authors: Kulfan B. M. 
Published: February 2016

AbstractFor aerodynamic design optimisation as well as for multidisciplinary design optimisation studies, it is very desirable to limit the number of the geometric design variables. In Ref. 1, a ‘fundamental’ parametric aerofoil geometry representation method was presented. The method included the introduction of a geometric ‘class function/shape function’ transformation technique, CST, such that round nose/sharp aft end geometries as well as other classes of geometries could be represented exactly by analytic well behaved and simple mathematical functions having easily observed physical features. The CST method was shown to describe an essentially limitless design space composed entirely of analytically smooth geometries. In Ref. 2, the CST methodology was extended to more general three dimensional applications such as wing, body, ducts and nacelles. It was shown that any general 3D geometry can be represented by a distribution of fundamental shapes, and that the ‘shape function/class function’ methodology can be used to describe the fundamental shapes as well as the distributions of the fundamental shapes. A number of applications of the ‘CST’ method to nacelles, ducts, wings and bodies were presented to illustrate the versatility of this new methodology. In this paper, the CST method is extended to include geometric warping such as variable camber, simple flap, aeroelastic and flutter deflections. The use of the CST method for geometric morphing of one geometric shape into another is also shown. The use of CST analytic wings in design optimisation will also be discussed.