bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aerodynamics of an aerofoil in transonic ground effect: numerical study at full-scale Reynolds numbers
Authors: Doig G. , Barber T. J. , Neely A. J. , Myre D. D. 
Published: February 2016

AbstractThe potential positive effects of ground proximity on the aerodynamic performance of a wing or aerofoil have long been established, but at transonic speeds the formation of shock waves between the body and the ground plane would have significant consequences. A numerical study of the aerodynamics of an RAE2822 aerofoil section in ground effect flight was conducted at freestream Mach numbers from 0·5 to 0·9, at a range of ground clearances and angles of incidence. It was found that in general the aerofoil’s lifting capability was still improved with decreasing ground clearance up until the point at which a lower surface shock wave formed (most commonly at the lowest clearances). The critical Mach number for the section was reached considerably earlier in ground effect than it would be in freestream, and the buffet boundary was therefore also reached at an earlier stage. The flowfields observed were relatively sensitive to changes in any given variable, and the lower surface shock had a destabilising effect on the pitching characteristics of the wing, indicating that sudden changes in both altitude and attitude would be experienced during sustained transonic flight close to the ground plane. Since ground proximity hastens the lower surface shock formation, no gain in aerodynamic efficiency can be gained by flying in ground effect once that shock is present.
Kinematic and experimental aerodynamic characterisation of the RotaFlap – a novel flapping wing mechanism
Authors: Ania A. , Poirel D. , Potvin M.-J. 
Published: February 2016

AbstractA unique patented mechanism, termed ‘RotaFlap’, which can move its wings in a figure-eight shape kinematically similar to insects or hummingbirds, has been investigated through the design, construction, integration and testing of various prototypes. In this paper, the most recent prototype is presented whereby the RotaFlap kinematics is characterised to understand some of its most pertinent parameters. A host of variations have been identified and in this study a subset of these have been tested. A preliminary characterisation of the force production, especially the vertical lift coefficient, has been completed. It is concluded that this mechanism produces vertical lift coefficient values similar to insect and hummingbird flight for similar Reynolds numbers.
Thermomechanical behaviour of a damaged thermal protection system: experimental correlation and influence of hypersonic flow
Authors: Ng W. H. , Friedmann P. P. , Waas A. M. , McNamara J. J. 
Published: February 2016

Abstract
This paper describes a combined experimental and numerical study on damaged and undamaged space shuttle tile thermal protection system (TPS). The principal objective of the study is to determine its thermomechanical behaviour and assess the structural integrity of the TPS. The TPS tile specimens are subjected to a temperature profile corresponding to the thermal loads of the Access to Space reference vehicle. Experiments are conducted in a vacuum chamber that allows re-entry static pressure to be simulated. Temperatures on the top and bottom surfaces of the specimen, and the strains in the underlying structure are recorded. The experimental results are used to guide the development of a refined finite element model, which is subsequently used to simulate the interactions between the high speed external flow past the cavity that represents damage. Using this model, the relative effects of damage on the thermal protection capability and the induced thermal stresses are determined by comparing the response of the damaged configurations with the undamaged configuration. Damage increases the thermal loads and significantly reduces the radiation heat loss from the surface of the tile, resulting in elevated temperatures. Results indicate that damage can raise the maximum temperature in the tile to values that exceed its melting point.
Heat transfer characteristic modelling and the effect of operating conditions on re-cooled cycle for a scramjet
Authors: Bao W. , Qin J. , Zhou W. X. 
Published: February 2016

Abstract
A re-cooled cycle has been proposed for a regeneratively cooled scramjet to reduce the hydrogen fuel flow for cooling. Upon the completion of the first cooling, fuel can be used for secondary cooling by transferring the enthalpy from fuel to work. Fuel heat sink (cooling capacity) is thus repeatedly used and fuel heat sink is indirectly increased. Instead of carrying excess fuel for cooling or seeking for any new coolant, the cooling fuel flow is reduced, and fuel onboard is adequate to satisfy the cooling requirement for the whole hypersonic vehicle. A performance model considering flow and heat transfer is build. A model sensitivity study of inlet temperature and pressure reveals that, for given exterior heating condition and cooling panel size, fuel heat sink can be obviously increased at moderate inlet temperature and pressure. Simultaneously the low-temperature heat transfer deterioration and Mach number constrains can also be avoided.
On the generation of a helicopter aerodynamic database
Authors: Raffel M. , De Gregorio F. , de Groot K. , Schneider O. , Sheng W. , Gibertini G. , Seraudie A. 
Published: February 2016

AbstractThe GOAHEAD (Generation of an Advanced Helicopter Experimental Aerodynamic Database for CFD code validation) consortium was created in the frame of an EU-project in order to create an experimental database for the validation of 3D-CFD and comprehensive aeromechanics methods for the prediction of unsteady viscous flows. This included the rotor dynamics for complete helicopter configurations, i.e. main rotor – fuselage – tail rotor configurations with emphasis on viscous phenomena like flow separation and transition from laminar to turbulent flow. The wind tunnel experiments have been performed during two weeks in the DNW-LLF on a Mach-scaled model of a modern transport helicopter consisting of the main rotor, the fuselage, control surfaces and the tail rotor. For the sake of controlled boundary conditions for later CFD validation, a closed test section has been used. The measurement comprised global forces of the main rotor and the fuselage, steady and unsteady pressures, transition positions, stream lines, position of flow separation, velocity profiles at the test section inlet, velocity fields in the model wake, vortex trajectories and elastic deformations of the main and tail rotor blades.
Subsonic aerofoil design 2010
Authors: Somers D. M. 
Published: February 2016

AbstractThe state of the art as practiced by a handful of aerofoil designers is discussed. The methods used, both theoretical and experimental, are described. Aerofoil/application design integration and expansion of the design envelope to lower and higher Reynolds numbers are illustrated by examples, including the slotted, natural-laminar-flow aerofoil.
Study of jets from rectangular nozzles with square grooves
Authors: Kumar P. Arun , Verma S. B. , Elangovan S. 
Published: February 2016

AbstractAn experimental study has been carried out to understand jet flow development from plain and grooved rectangular nozzles of aspect ratio 2:1 using two-component hotwire anemometry. Grooves of square configuration (side 4mm) and length 5mm were introduced in the (i) minor-axis, (ii) major-axis and, (iii) in both minor- and major-axes directions. The equivalent diameter of the plain rectangular nozzle is 37·5mm. Studies were carried out for a nominal jet exit velocity of 20ms−1 and for Reynolds number based on equivalent diameter of 54,000. The introduction of grooves in either plane does not show any influence on the potential-core length but results in faster jet-decay thereafter. It is observed that the grooves when introduced in minor-axis direction inhibit the jet growth in that plane while promoting the jet growth along major-axis plane and hence, delays the phenomena of axis-switching. However when introduced in major-axis direction, the grooves promote jet growth along major-axis plane while inhibiting jet-growth in minor-axis plane. Cross-sectional contours of mean-velocity suggest that the grooves modify the process of overall jet development significantly in the plane in which they are introduced relative to the plain jet and hence, significantly affect the axis-switching location in each case.
Dynamics of the wing-tip vortex in the near field of a NACA 0012 aerofoil
Authors: del Pino C. , López-Alonso J.M. , Parras L. , Fernandez-Feria R. 
Published: February 2016

AbstractThe dynamics of the wing tip vortex in the near-field of a NACA 0012 aerofoil has been analysed by means of flow visualisations in a water tunnel. Different axial distances near the wing up to four chords, Reynolds numbers up to 42,000 and three angles-of-attack are studied to characterise the behaviour of the vortex meandering. The spatio-temporal vortex centre positions show distorted elliptical shapes in a (x,y)-plane. The Reynolds number has no significant influence on the axial evolution of the meandering amplitude. In addition, the flow visualisations obtained with a low speed camera are analysed by the singular value or proper orthogonal decomposition. Thus, the most energetic displacement modes are obtained. The frequency associated to these modes is computed by FFT. In all the cases studied, our results show that the most unstable mode corresponds to the azimuthal wavenumber |n| = 1 in the so-called Kelvin helical modes and the frequency is lower or close to 1Hz.
New helicopter model identification method based on flight test data
Authors: De Jesus Mota S. , Botez R. M. 
Published: February 2016

AbstractA helicopter model has been identified and validated for flight conditions defined by altitudes, speeds, loadings and centre of gravity positions. To identify the helicopter models, 2-3-1-1 multistep control inputs were performed by the pilot to excite all helicopter modes. Then, each estimated signal has to remain in tolerance margins defined by the Federal Aviation Administration. Three methods were used to observe the system outputs from its states: a fuzzy logic method, a linear method optimised with a neural network algorithm and a classical method. Because of random effects when gathering data, classical method did not give good enough results. The fuzzy logic method was not robust enough so that output plots showed peaks that could be felt by the pilot. Then, because the model could be implemented in a simulator for the pilot training, the pilot feedback is very useful in order to compare the reality with the results of the mathematical model. When the outputs are obtained from the measured state variables, the linear method gave the best results.
Wind-tunnel tests of a tilt-rotor aircraft
Authors: Gibertini G. , Auteri F. , Campanardi G. , Macchi C. , Zanotti A. , Stabellini A. 
Published: February 2016

AbstractA wide aerodynamic test campaign has been carried out on the tiltrotor aircraft ERICA at the Large Wind Tunnel of Politecnico di Milano by means of a modular 1:8 scale model in order to produce a dataset necessary to better understand the aerodynamic behaviour of the aircraft and to state its definitive design.The target of the tests was the measurement of the aerodynamic forces and moments in several different configurations and different attitudes. The test program included some conditions at very high incidence and sideslip angles that typically belong to the helicopter-mode flight envelope and measurements of forces on the tail and on the tilting wings.A large amount of data has been collected that will be very useful to refine the aircraft design. In general the aircraft aerodynamics do not present any critical problems, but further optimisation is still possible. From the viewpoint of drag in the cruise configuration, the sponsons of the landing gear seem to be worth some further design refinement since they are responsible for a 20% drag increase with respect to the pure fuselage configuration. On the contrary, the wing fairing has proved to work well when the aircraft longitudinal axis is aligned with the wind, providing just a slight drag increase.Two other interesting aspects are the quite nonlinear behaviour of the side force for the intermediate sideslip angles as well as the noticeable hysteresis in the moment coefficient at very high incidence angles.
Modification impact on aerodynamic performance of hypersonic waverider
Authors: Xiao-Qing C. , Zhong-Xi H. , Jian-Xia L. , Xian-Zhong G. 
Published: February 2016

AbstractWaverider serves as a good candidate for hypersonic vehicles. The typical waverider has sharp leading edge and no control face, which is inappropriate for practical use. This paper puts forward a method modifying the waverider, and the modification impact on the performance of waverider at hypersonic flow conditions is studied. The modification is based on blunted waverider, includes cutting the tip and introducing two control wings. The modification’s effect on aerodynamic performance is obtained and analysed through Computational Fluid Dynamics (CFD) techniques. When blunted with 2cm radius, the waverider retains its good aerodynamic performance and the heat flux at the stagnation point can be managed. Three factors of the introduced wing are argued, the fixed angle, aspect ratio and wing area. Results show that influence on the aerodynamic coefficient is slight and the vehicle retains its high lift-to-drag ratio. The main influences of the modification are the control ability and trim efficiency, which is the motivation of this work and can be adapted when designing a practical waverider.
Emission comparison of turbofan and open rotor engines under special consideration of aircraft and mission design aspects
Authors: Seitz A. , Schmitt D. , Donnerhack S. 
Published: February 2016

AbstractAn integrated parametric model involving the design of propulsion system, airframe and flight mission is presented. Based hereon, the carbon dioxide (CO2) emission characteristics of advanced direct-drive turbofan and open rotor powered aircraft are analysed against pertinent aircraft and propulsion system design parameters. In addition, initial concept-specific trend statements on nitrogen oxides (NOx) as well as propulsor noise emission characteristics are derived. The obtained results contribute to a better understanding of more appropriate aircraft design attributes for advanced system architectures.
Applying heat pipes to a novel concept aero engine: Part 1 – Design of a heat-pipe heat exchanger for an intercooled aero engine
Authors: Camilleri R. , Ogaji S. , Pilidis P. 
Published: February 2016

AbstractCivil aviation has instilled new perceptions of a smaller world, creating new opportunities for trade, exchange of cultures and travelling for leisure. However, it also brought with it an unforeseen impact on the environment. Aviation currently contributes to about 3·5% of the global warming attributed from human activities. With the forecasted rate of growth, this is expected to rise to about 15% over the next 50 years. Although it is projected that the annual improvements in aircraft fuel efficiency are of the order of 1-2%, it is suggested that the current gas turbine design is fully exploited and further improvements are difficult to achieve. A new generation of aero engine core concepts that can operate at higher thermal efficiencies and lower emissions is required. One possibility of achieving higher core efficiencies is through the use of an inter-cooled (IC) core at high overall pressure ratios (OPR). The concept engine, expected to enter into service around 2020, will make use of a conventional heat exchanger (HEX) for the intercooler. This paper seeks to introduce a heat pipe heat exchanger (HPHEX) as an alternative design of the intercooler. The proposed HPHEX design takes advantage of the convenience of the geometry of miniature heat pipes to provide a reduction in pressure losses and weight when compared to conventional HEX. The HPHEX will be made of a number of stages, each stage being made of a large number of miniature heat pipes in radial configuration, that will extend from the inter-compressor duct to the bypass split, thus eliminating any ducting to and from the intercooler. This design offers up to 32% reduction in hot pressure losses, 34% reduction in cold pressure losses and over 41% reduction in weight.
Pilot task demand load during RNAV approaches with a Cessna Citation
Authors: Heiligers M. M. , van Bennekom K. T. P. , van Tuinen T. J. , van Holten Th. , Mulder M. 
Published: February 2016

AbstractThis research aims to develop a method which predicts the task demand load as experienced by pilots while flying an area navigation (RNAV) approach. First, this will yield insight in which aspects of an approach actually influence pilot task demand load. And second, during the design of approaches this method can be used to rapidly evaluate a potential approach and to ‘optimise’ an approach with respect to pilot task demand load. During previous research, focusing on approaches flown with a B747, a list of factors that influence pilot task demand load has been obtained, as well as a method to keep pilot task demand load at an acceptable level. The method consists of seven guidelines to be adhered to during approach design. This paper shows that the list of factors and the method do not only apply to a B747 aircraft but are generally applicable to other aircraft as well. This is underpinned by results from both flight simulator tests and real flight tests with TU Delft’s Cessna Citation laboratory aircraft. Additionally, it is shown that there are no discrepancies between the list of factors influencing pilot task demand load resulting from the flight simulator tests and the list of factors resulting from the real flight tests.
Investigation of the three-dimensional flow over a 40° swept wing
Authors: Zhang S. , Jaworski A. J. , Turner J. T. , Wood N. J. 
Published: February 2016

AbstractThree-component laser Doppler anemometry (LDA) has been used to measure the complex flow distributions over the suction surface of a symmetrical 40°swept wing model at an angle of incidence of 9° and for the relatively low Reynolds number (based on the root chord) of 2·1 × 105. Emphasis was placed on the separation and reattachment of the boundary-layer flow, and the formation of vortical structures.The experimental programme now described utilised a large wind tunnel and several advanced measurement techniques to produce an unusually detailed collection of results. Thus, data are presented here for the behaviour of the three-dimensional boundary layer developing on the suction surface at positions from 30% to 90% semi-span. These results show the spatial variations of the time-averaged mean and fluctuating velocity components in three orthogonal directions, including the distributions of the normal and shear stress levels. Further analysis has enabled the time-averaged vortical structures to be identified and compared with the results of surface flow visualisation.Flow over a swept wing poses many challenges for the computational modeller. The underlying aim, here, therefore, was to produce a data archive for the validation of computer predictions. As will be shown, some of the experimental results have already been used in this way and the data base is available for use by other workers.
Aerodynamic shape optimisation of hovering rotors using compressible CFD
Authors: Allen C. B. , Rendall T. C. S. 
Published: February 2016

AbstractGeneric wrap-around shape optimisation technology is presented, and is applied to a helicopter rotor in hover, using compressible CFD as the aerodynamic model. An efficient domain element shape parameterisation method is used as the surface control and deformation method, and is linked to a radial basis function global interpolation, to provide direct transfer of domain element movements into deformations of the design surface and the CFD volume mesh. This method is independent of mesh type and size, and optimisation independence from the flow solver is achieved by obtaining sensitivity information for an advanced parallel gradient-based algorithm by finite-difference. The method is applied here to a two-bladed hovering rotor, with transonic tip speed, comparing the effects of global twist parameters and more local planform parameters. Significant torque reductions are achieved in both cases, and it is shown that using only three global twist parameters are extremely effective. Using 63 local and global parameters, large geometric changes are demonstrated, with both induced power and wave drag reduced.
Reactive route selection from pre-calculated trajectories – application to micro-UAV path planning
Authors: Hall J. , Anderson D. 
Published: February 2016

AbstractOperating micro-UAVs autonomously in complex urban areas requires that the guidance algorithms on-board are robust to changes in the operating environment. Limited endurance capability demands an optimal guidance algorithm, which will change as the environment does. All optimal path-planning routines are computationally intensive, with processor load a function of the environmental complexity. This paper presents a new algorithm, the reactive route selection algorithm, for storing a bank of optimal trajectories computed off-line and blending between these optimal trajectories as the operating environment changes. An example is presented using a mixed-integer linear program to generate the optimal trajectories.
Computational study of flowfield characteristics in cavities with stores
Authors: Khanal B. , Knowles K. , Saddington A. J. 
Published: February 2016

AbstractIn this paper, the results of computational studies on the unsteady flow features in three-dimensional empty cavities and cavities with a representative store are presented. Flow simulations with a turbulence model based on a hybrid method, which behaves as a standard Reynolds-averaged Navier-Stokes (RANS) model within the attached boundary layer and as a Large-Eddy Simulation LES sub-grid scale model in the rest of the flow (commonly known as Detached-Eddy Simulation (DES)) are used in this study. The time-mean flow study showed the presence of three-dimensional effects inside the cavities. The mean flowfield visualisation also clearly showed the presence of a pair of ‘tornado-like’ vortices in the upstream half of the cavity which merge to a single, large recirculation further downstream. Visualisation for the cavity-with-store case revealed that the mean flowfield was effectively divided into two halves with significant reduction of the spanwise flow across the cavity width. In the unsteady flow study, near-field acoustic spectra were computed for the empty cavity and cavity-with-store cases. Study of unsteady pressure spectra for the cavity-with-store case found the presence of many peaks and the corresponding mode frequencies were found to agree well with the Rossiter modes. The blockage effect of store and strut on the spanwise flow is thought to have reduced the interaction, and subsequent non-linear coupling, between the Rossiter modes. This may be the reason for the co-existence of multiple modes without the coupling among them.