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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 84 journals)
Acta Astronautica     Hybrid Journal   (207 followers)
Advances in Space Research     Full-text available via subscription   (208 followers)
Aeronautica     Open Access   (4 followers)
Aerospace     Open Access   (1 follower)
Aerospace and Electronic Systems, IEEE Transactions on     Hybrid Journal   (46 followers)
Aerospace Science and Technology     Hybrid Journal   (233 followers)
Affective Computing, IEEE Transactions on     Hybrid Journal   (6 followers)
AIAA Journal     Full-text available via subscription   (389 followers)
Air Force Magazine     Full-text available via subscription   (3 followers)
Air Medical Journal     Hybrid Journal   (2 followers)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (91 followers)
American Journal of Space Science     Open Access   (29 followers)
Artificial Satellites     Open Access   (11 followers)
Aviation     Hybrid Journal   (3 followers)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (1 follower)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (5 followers)
Aviation Week and Space Technology     Full-text available via subscription   (7 followers)
Aviation, Space, and Environmental Medicine     Full-text available via subscription   (5 followers)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (12 followers)
CEAS Aeronautical Journal     Hybrid Journal   (20 followers)
Chinese Journal of Aeronautics     Open Access   (10 followers)
Control Systems     Hybrid Journal   (18 followers)
Cosmic Research     Hybrid Journal   (2 followers)
COSPAR Colloquia Series     Full-text available via subscription  
Egyptian Journal of Remote Sensing and Space Science     Open Access   (4 followers)
Elsevier Astrodynamics Series     Full-text available via subscription   (1 follower)
Fatigue of Aircraft Structures     Open Access   (4 followers)
Frontiers in Aerospace Engineering     Open Access   (2 followers)
Gyroscopy and Navigation     Hybrid Journal   (9 followers)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (32 followers)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (8 followers)
International Journal of Aeroacoustics     Full-text available via subscription   (5 followers)
International Journal of Aerodynamics     Hybrid Journal   (11 followers)
International Journal of Aerospace Engineering     Open Access   (38 followers)
International Journal of Aerospace Innovations     Full-text available via subscription   (10 followers)
International Journal of Applied Geospatial Research     Full-text available via subscription   (4 followers)
International Journal of Aviation Management     Hybrid Journal  
International Journal of Aviation Psychology     Hybrid Journal   (4 followers)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription  
International Journal of Crashworthiness     Hybrid Journal   (5 followers)
International Journal of Flow Control     Full-text available via subscription   (1 follower)
International Journal of Hypersonics     Full-text available via subscription   (3 followers)
International Journal of Micro Air Vehicles     Full-text available via subscription   (2 followers)
International Journal of Satellite Communications Policy and Management     Hybrid Journal  
International Journal of Space Science and Engineering     Hybrid Journal   (2 followers)
International Journal of Space Structures     Full-text available via subscription   (2 followers)
International Journal of Turbo & Jet-Engines     Full-text available via subscription  
ISRN Aerospace Engineering     Open Access  
ISRN Astronomy and Astrophysics     Open Access   (11 followers)
Journal of Aerospace Computing, Information, and Communication     Full-text available via subscription   (12 followers)
Journal of Aerospace Engineering     Full-text available via subscription   (71 followers)
Journal of Aerospace Engineering & Technology     Full-text available via subscription  
Journal of Aerospace Operations     Hybrid Journal   (3 followers)
Journal of Aerospace Technology and Management     Open Access   (1 follower)
Journal of Aircraft     Full-text available via subscription   (192 followers)
Journal of Airline and Airport Management     Open Access   (2 followers)
Journal of Aviation Technology and Engineering     Open Access   (6 followers)
Journal of Guidance, Control, and Dynamics     Full-text available via subscription   (44 followers)
Journal of Konbin     Open Access  
Journal of Navigation     Hybrid Journal   (16 followers)
Journal of Propulsion and Power     Full-text available via subscription   (168 followers)
Journal of Space Weather and Space Climate     Open Access   (3 followers)
Journal of Spacecraft and Rockets     Full-text available via subscription   (243 followers)
Journal of Spatial Science     Hybrid Journal   (1 follower)
Journal of the American Helicopter Society     Full-text available via subscription   (1 follower)
Microgravity Science and Technology     Hybrid Journal  
New Space     Hybrid Journal   (2 followers)
Nonlinear Dynamics     Hybrid Journal   (5 followers)
Population Space and Place     Hybrid Journal   (1 follower)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (19 followers)
Progress in Aerospace Sciences     Full-text available via subscription   (39 followers)
Propulsion and Power Research     Open Access   (1 follower)
Recent Patents on Space Technology     Full-text available via subscription  
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (12 followers)
Space and Polity     Hybrid Journal   (2 followers)
Space Communications     Hybrid Journal   (2 followers)
Space Policy     Hybrid Journal   (15 followers)
Space Research Today     Full-text available via subscription   (24 followers)
Space Safety Magazine     Free   (3 followers)
Space Science Reviews     Hybrid Journal   (9 followers)
SpaceNews     Free   (168 followers)
Transportmetrica A : Transport Science     Hybrid Journal   (2 followers)
Вісник Національного Авіаційного Університету     Open Access   (2 followers)
Вестник УГАТУ     Open Access  
CEAS Aeronautical Journal    [22 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1869-5582
     Published by Springer-Verlag Homepage  [2187 journals]
  • Optimum number of engines for transport aircraft employing electrically
           powered distributed propulsion
    • Abstract: Abstract Realizing a significant reduction of enroute emissions with respect to greenhouse gases is one major challenge in aircraft design today. Conventional kerosene propulsion systems are going to reach their efficiency limits in near future and it will be very ambitious to fulfill the requirements for future aircraft transportation using conventional engines. Consequently, new approaches for propulsion system design and integration are required to further improve aircraft efficiency through synergy effects. In this paper, a universally electric, short-haul, medium-capacity aircraft utilizing electric motors and battery for motive power is used as datum. The focus lies on the impact of a distributed propulsion system on the aircraft design and flight performance and will not discuss the advantages and disadvantages of the used reference aircraft configuration. Initial studies were performed identifying that the critical design cases for electric motor sizing are the one-engine-inoperative (OEI) flight segments, i.e., the climb gradients required at take-off and landing as well as field length requirements. By increasing the number of installed engines (i.e., motor–fan combinations) the OEI performance requirements may be satisfied with a reduced amount of installed motor and battery system power. An integrated aircraft performance analysis is conducted to estimate the possible net benefit in terms of increased aircraft range when increasing the number of installed engines. Aerodynamic efficiency degradation is considered as well as weight impacts due to electric motor scaling and necessary system architecture modifications. The analysis shows that a 6 % increase in aircraft design range can be achieved when going from 2 to 4 installed propulsive devices.
      PubDate: 2014-01-15
       
  • A reduced-order model for the investigation of the aeroelasticity of
           circulation-controlled wings
    • Abstract: Abstract The application of active circulation control allows shortening of runways which can be significant in particular cases. The goal of the present paper is to study the influence of the circulation control on the aeroelastic behaviour of wings. For numerical analyses, a simplified computational model is presented, which allows for systematic parameter variations. The model is based on model reduction using modal analysis, so that an efficient performance of numerical studies is possible as well as the integration of the aeroelasticity into a flight dynamics model.
      PubDate: 2014-01-11
       
  • System architecture of HALAS—a helicopter slung load stabilisation
           and positioning system
    • Abstract: Abstract To support helicopter pilots during slung load operations currently a pilot assistance system called Hubschrauber-Außenlast-Assistenzsystem (HALAS) is being developed within a cooperation of the German Aerospace Centre (DLR) and iMAR Navigation GmbH. The objective of this research is the demonstration of an automatic slung load stabilisation and positioning system during the flight test with DLR’s research helicopter Active Control Technology/Flying Helicopter Simulator (ACT/FHS). The automatic slung load control system is being designed to extend the functionalities of the helicopter’s stability, control and augmentation system. The control system will be able to handle the challenges of rescue hoist operations. This means compensation of additional roll, pitch and yaw moments created by a significant distance of the load suspension point to the helicopter’s centre of gravity and the handling of a variable cable length. To measure the slung load motion, an optical-inertial sensor is being developed by iMAR Navigation GmbH. In this paper, the overall system architecture of HALAS as well as the hardware integration into the ACT/FHS is explained. The optical-inertial sensor used for the slung load dynamics measurement and estimation is described in detail. Furthermore, a first system analysis of a simulation model used for the later controller design is presented. The focus of the stability analysis is laid on variations of cable length, load mass and load suspension point position. The control law development process itself is not part of this paper but will be published later.
      PubDate: 2013-12-10
       
  • A practical biodynamic feedthrough model for helicopters
    • Abstract: Abstract Biodynamic feedthrough (BDFT) occurs when vehicle accelerations feed through the pilot’s body and cause involuntary motions of limbs, resulting in involuntary control inputs. BDFT can severely reduce ride comfort, control accuracy and, above all, safety during the operation of rotorcraft. Furthermore, BDFT can cause and sustain rotorcraft-pilot couplings. Despite many different studies conducted in past decades—both within and outside of the rotorcraft community—BDFT is still a poorly understood phenomenon. The complexities involved in BDFT have kept researchers and manufacturers in the rotorcraft domain from developing robust ways of dealing with its effects. A practical BDFT pilot model, describing the amount of involuntary control inputs as a function of accelerations, could pave the way to account for adverse BDFT effects. In the current paper, such a model is proposed. Its structure is based on the model proposed by Mayo (15th European Rotorcraft Forum, Amsterdam, pp. 81-001–81-012 1989), and its accuracy and usability are improved by incorporating insights from recently obtained experimental data. An evaluation of the model performance shows that the model describes the measured data well and that it provides a considerable improvement to the original Mayo model. Furthermore, the results indicate that the neuromuscular dynamics have an important influence on the BDFT model parameters.
      PubDate: 2013-12-01
       
  • Experimental and numerical examination of a helicopter hovering in ground
           effect
    • Abstract: Abstract This study collects experimental data of a helicopter hovering in ground effect and intends to prove the capability to compute the flow field around the measured helicopter rotor with the use of the flow solver FLOWer. Firstly, the wake trajectory of a Hughes 300C helicopter hovering in ground effect was obtained by introducing fog in the rotor disk, while visualizing the blade tip vortices with a laser light sheet and a high speed camera. Secondly, the isolated rotor of the Hughes 300C was modeled numerically and computed with the block-structured second-order flow solver FLOWer from DLR, in order to provide a computational validation for full size rotors in ground effect hover. Blade dynamics were neglected and the rotor was trimmed to the experimental thrust. It was found that the flow solver is capable of simulating the flow around a full size helicopter rotor during hover in ground effect. The wake trajectories are convected downwards slightly faster than in the experiment. The radial wake path fits well with the experimental one until high wake ages, where the numerically as well as experimentally reproduced trajectory becomes unstable. The development of the thrust value was analyzed with a Fourier transform. Disturbances due to the ground can be detected especially at higher harmonics of the blade passing frequency. For comparison, the rotor was also examined numerically out of ground effect. As expected, the oscillations are more periodic than close to the ground. An analysis of the performance data led to a benefit of 21 % due to the ground effect.
      PubDate: 2013-12-01
       
  • Helicopter miniaturized and low-cost obstacle warning system
    • Abstract: Abstract This paper reports on a novel development of a miniaturized and low-cost near-field obstacle warning system for helicopters based on an adapted electronically steerable, automotive radar. This system is intended to be used as a flight aid to enhance situational awareness and flight safety by detecting and informing the pilot about obstacles in the near vicinity of the helicopter. The activities described herein are performed in the frame of a research project partially funded by the German Federal Ministry of Economics and Technology. Between January 2010 and March 2012 the system concept was elaborated and a first prototype of the sensor system was developed and successfully tested both in ground and flight tests. This paper will describe the system concept, its design considerations and it will present first test results.
      PubDate: 2013-12-01
       
  • Effects of visual and motion cues in flight simulation of ship-borne
           helicopter operations
    • Abstract: Abstract Good visual cues are necessary in the flight simulation of ship-borne helicopter operations. Operating in a degraded visual environment cues has a negative impact on pilot workload and task performance. However, the need for motion cues in piloted flight simulation is still a widely debated issue. This paper describes a preliminary piloted flight simulation study into the effects of visual and motion cues on the operation of ship-borne helicopters and pilot workload. Unsteady CFD airwakes have been computed and integrated into the FLIGHTLAB modelling and simulation environment with a simulated rotorcraft model, configured to be representative of an SH-60B helicopter. A series of ship-deck landing and hover manoeuvres have been conducted using the University of Liverpool’s HELIFLIGHT-R motion-base flight simulator representing different visual and motion cues, for a range of ship airwakes and sea states (ship deck motions). The usable cue environment (UCE), handling quality and pilot workload ratings were assessed using visual cue ratings, handling quality rating and the Bedford workload rating scale and Deck Interface Pilot Effort Scale. This paper presents the results from simulation trials with two test pilots examining the effect of the simulation cueing on task performance and workload. Visual cues were found to have a significant impact both on the UCE ratings and pilot workload ratings. In degraded visual environments, the pilot’s ability to make corrections in attitude and translational rates was reduced. Pilots experienced higher workload in terms of compensatory control inputs to complete the same mission task as compared to operations in a good visual environment. Analysis of the pilots’ workload ratings and control activity show that motion cueing can cause differences in pilot perceived workload. For the simulation of ship-borne operations, the impacts of motion cueing are dependent on other simulation conditions, which include visual environments, airwake, sea states and ship deck motion. The effect of motion cueing on pilot workload and control activity was found to be more significant when the visual cueing was degraded. The variations in pilot workload ratings and control activities under different motion and visual cues indicate that the Ship Helicopter Operating Limits can be affected by the simulation cueing fidelity.
      PubDate: 2013-12-01
       
  • Enhancement of aircraft wake vortex decay in ground proximity
    • Abstract: Abstract Aircraft wake vortex evolution in ground proximity is investigated experimentally in a water towing tank, as well as numerically with wall-resolved large eddy simulation (LES). With these complementary instruments the enhancement of wake vortex decay by obstacles, introduced at the ground surface, is analyzed. The experimental methods include time-resolved stereo particle image velocimetry and vortex core visualization. For comparison with the experiment, the LES considers the turbulent wake of the strut, holding the towed aircraft model. Wake vortex trajectories and circulation decay are compared at different distances from the obstacle. Tracers are employed to visualize the obstacle’s effects on the vortex core, in LES and experiment. The experimentally obtained trajectories and decay characteristics are reproduced qualitatively by simulations, whereas the agreement is degraded at later times. Beyond that, the vortex dynamics, deduced from the LES results, help to understand the experimental observations. The obstacles trigger helical secondary vortex structures, propagating along the primary vortices. The observed propagation speed of the helical disturbance is fairly well predicted by the suggested simple model. It is shown that the obstacles significantly modify the vortex interaction with the ground and substantially accelerate vortex decay. Two neighboring obstacles lead to colliding disturbances that further enhance vortex decay rates.
      PubDate: 2013-11-27
       
  • Design analysis and sizing of a circulation controlled CFRP wing with
           Coandǎ flaps via CFD–CSM coupling
    • Abstract: Abstract Preliminary design tools are essential during aircraft design to make conclusions about an aircraft’s performance. Generally this process employs methods of low and medium fidelity to create comparatively fast results for a high number of parameter variations. High-fidelity methods are needed to verify theses results and to consider components in more detail. A 100 PAX commercial aircraft with short take-off and landing capabilities of 800 m with circulation controlled high-lift devices is under investigation at the Collaborative Research Centre SFB 880. In this paper, a global wing analysis with a high detail model is conducted and the results are compared with results attained with a preliminary aircraft design tool. Several detailed designs for the air feed system integration are proposed and examined regarding weight and stiffness characteristics on a representative high-lift device section model. Fluid–structure coupling is employed during all analyses to transfer aerodynamic loads and structural displacements. The aeroelastic impact of the slot stiffness on the Coandǎ effect during landing is then quantified. The attained aerodynamic performance results and structural characteristics of each configuration are compared and the advantages are discussed.
      PubDate: 2013-10-17
       
  • Evaluation of flying helicopter simulator noseboom correction coefficients
    • Abstract: Abstract The EC135 flying helicopter simulator of DLR is equipped with noseboom-mounted sensors to enable measurements relatively unperturbed by rotor downwash effects. Remaining downwash disturbances on pressure and airflow angles measurements are compensated with correction coefficients, derived with the simultaneous calibration of aircraft data system (SCADS) technique. The purpose of this paper is to evaluate the quality of correction coefficients derived using estimated wind by comparing the difference in wind estimation from three different objective functions and two different optimization routines. The results obtained from the SCADS technique are also verified with accurate wind measurements close to the helicopter flight path from position error correction tower flyby maneuvers. The results show that the lower bound of the range in which airspeed can be detected via dynamic pressure measurements has been expanded from 30 to 16.2 kt.
      PubDate: 2013-10-04
       
  • Manufacturing of CFRP specimens with controlled out-of-plane waviness
    • Abstract: Abstract In this paper, the manufacturing of carbon fibre reinforced plastic laminates with intentionally, reproducibly and mathematically defined high quality out-of-plane waviness made from unidirectional prepreg material is described. This methodology is employed to manufacture tension test specimens with included controlled out-of-plane ply waviness. The waviness ratio is A/L = 0.09, where A and L denote the wave amplitude and the wavelength, respectively. A number of quality assurance verifications is carried out on these specimens before the tension test. These verifications are to corroborate that the realised graded waviness is consistent with the theoretically defined waviness function. The manufacturing process of these specimens is described in detail. The tension test of the specimens is performed by means of a hydraulic testing device. The force–displacement curves of the tension test are plotted to analyse the material behaviours. Experimental investigations are carried out in conjunction with non-destructive 3D optical measurement methodology to identify the failure mechanisms. The results of quality assurance verifications on the specimens exhibit a perfect matching between the geometrically graded shapes and the theoretical function. Furthermore, the results of tension qualification tests show that all specimens have very similar damage behaviour and the failure events have occurred in the waviness area.
      PubDate: 2013-10-04
       
  • A contribution to the development of a full flight envelope
           quasi-nonlinear helicopter simulation
    • Abstract: Abstract Helicopter modeling is a complex task as helicopters consist of many subsystems (nacelle, rotor, engine, $\ldots)$ … ) that are described by coupled differential equations. Controller design requires a model that is accurate over a certain frequency range. Usually, system identification is used to derive the models from flight test data and the model complexity depends on the frequency range of interest. As helicopters have eigenvalues that vary depending on airspeed, system identification is performed at different operating points. Each identified linear model is then valid only in a small region around the corresponding operating point. To arrive at a model that covers the whole operational envelope of the helicopter, the individual models are stitched together. This paper describes the derivation of a quasi-nonlinear model accounting for known nonlinear terms, such as gravity, inertia or trim curves. In addition, the coefficients of the identified linear matrices are interpolated depending on airspeed. Finally, the quasi-nonlinear as well as the linear model are compared against flight test data using model validation techniques. As the quasi-nonlinear model of the Flying Helicopter Simulator is validated, it can be used for a sophisticated controller design.
      PubDate: 2013-10-02
       
  • Contribution to an improved crash design for a composite transport
           aircraft fuselage—development of a kinematics model and an
           experimental component test setup
    • Abstract: Abstract Crashworthiness research for transport aircraft fuselage structures is important particularly with regard to the increasing ratio of carbon fibre reinforced plastic (CFRP) in primary structures. Although today’s aluminium fuselage structures offer sufficient crashworthiness purely due to the ductile behaviour of metal, the brittle behaviour of a CFRP fuselage structure implicates the need for special crash devices to avoid uncontrolled failure with little energy absorption. Hence, a specific crash design has to be developed for a CFRP fuselage structure. A numerical methodology was developed to investigate potential crash concepts on fuselage section level and to design appropriate crash devices. The essential of this so-called kinematics model is the potential to define the behaviour of structural crash devices by characteristic input curves using macro elements in the frames, vertical struts and the sub-cargo structure. By varying the load–deformation characteristics of the crash devices, different crash scenarios, in the sense of alternative crash sequences, can be defined, assessed and compared to each other. Different potential crash scenarios for narrow-body fuselage structures were analysed using this modelling approach. The final output characteristic of the macro elements in the frame structure represents the basis for an experimental investigation of energy absorbing frame bending mechanisms. A test setup for four point flexural test configurations was developed to investigate such concepts on the generic frame level. The setup was used to analyse the failure behaviour of frame components made of pure CFRP as well as hybrid CFRP/titanium laminates. Four quasi-static as well as four dynamic frame bending tests were conducted to investigate the energy absorbing failure mechanisms of such hybrid frame structures.
      PubDate: 2013-09-01
       
  • The HART II international workshop: an assessment of the state of the art
           in CFD/CSD prediction
    • Abstract: Abstract Over the past decade, there have been significant advancements in the accuracy of rotor aeroelastic simulations with the application of computational fluid dynamics methods coupled with computational structural dynamics codes (CFD/CSD). The HART II international workshop database, which includes descent operating conditions with strong blade–vortex interactions (BVI), provides a unique opportunity to assess the ability of CFD/CSD to capture these physics. In addition to a baseline case with BVI, two additional cases with 3/rev higher harmonic blade root pitch control are available for comparison. The collaboration during the workshop permits assessment of structured, unstructured, and hybrid overset CFD/CSD methods from across the globe on the dynamics, aerodynamics, and wake structure. Evaluation of the plethora of CFD/CSD methods indicates that the most important numerical variables associated with most accurately capturing BVI include the use of either a two-equation RANS model or detached eddy simulation-based turbulence model and a sufficiently small time step. An appropriate trade-off between grid fidelity and spatial accuracy schemes also appears to be important for capturing BVI on the advancing side of the rotor disk. Overall, the CFD/CSD methods generally fall within the same accuracy; cost-effective hybrid Navier-Stokes/Lagrangian wake methods tend to correlate less accurately with experiment and have larger data scatter than the full CFD/CSD methods for most parameters evaluated. The importance of modeling the fuselage is observed, and other requirements are discussed.
      PubDate: 2013-08-14
       
  • Study on the initial evolution of ring-like vortices generated by MVG
    • Abstract: Abstract In this paper, the initial evolution of ring-like vortices which are found behind the MVG-controlled supersonic flow is studied. It is verified that the ring-like vortices can come from the upstream vortex structure and be generated by shear layer instability at the boundary of the momentum deficit as well. However, because of the inflow’s fully developed turbulent flow, the lower boundary layer underneath the ring-like vortex structure will influence the formation of the vortex rings a lot. Furthermore, it is also found that certain vortex structures in the lower boundary layer can be lifted up and become the ring-like vortex. The formation and development of the ring-like vortices is more complicated under the consideration of the influence of the fully developed turbulent inflow.
      PubDate: 2013-07-28
       
  • Fast simulation of noise radiation and reduction from installed pusher
           propeller aircraft
    • Abstract: Abstract The aeroacoustic phenomena characteristic of a pusher-propeller configuration and their aerodynamic causes are discussed and analysed. The configuration under study is an industrially relevant design with a wing-mounted pusher propeller, which features a close coupling of the turboshaft engines exhaust nozzles and a five-bladed propeller. The coupling of an Actuator Disc model and unsteady free wake panel method is employed for the computation of the propeller unsteady aerodynamic force in “pusher” installations. The acoustic integration formulation based on Ffowcs-Williams/Hawkings equations is used to compute the sound propagation into the far field. A detailed comparison of the results from current fast coupling method with those of high-fidelity unsteady Reynolds averaged Navier–Stokes simulation will be presented and the differences between the two approaches are discussed. Furthermore, the possible noise reduction through a redesigned engine exhaust nozzle is discussed.
      PubDate: 2013-07-28
       
  • Numerical analysis of hub and fuselage drag breakdown of a helicopter
           configuration
    • Abstract: Abstract Compared to fixed wing aircraft, the helicopter is still a challenging configuration in terms of drag evaluation and understanding. In order to reduce and optimize the drag, the interactions between all components of fuselage and rotor head have to be analyzed. Thanks to the computational resources increase, the CFD becomes an efficient tool, complementary to the wind tunnel testing, to investigate different geometries and flow conditions. In the frame of the JTI CleanSky European project, the work presented in this paper is a preliminary task before the optimization and the drag reduction. It deals with the drag prediction of the fuselage and its main rotor head by CFD. The approach used here relies on a partitioning of the computational domain into near-body structured grids and off-body Cartesian grids, based on the Chimera method. The current work includes analysis of solutions for the isolated fuselage, the isolated rotor head and the complete configuration.
      PubDate: 2013-07-27
       
  • Effect of height of microvortex generators on swept shock wave boundary
           layer interactions
    • Abstract: Abstract A numerical study to evaluate the critical height of microvortex generators in controlling swept shock wave boundary layer interactions is carried out. The planar shock wave is generated by placing a 20° sharp fin in a supersonic flow at Mach 4. The ramp and thick vane microvortex generator geometries were considered. The device heights were varied from 30 to 90 % of the incoming boundary layer thickness. The efficacy of the devices was observed to increase with increasing device height up to a height of 70 % of the incoming boundary layer thickness beyond which no further improvement was achieved.
      PubDate: 2013-06-21
       
  • Towards greener helicopters
    • Abstract: Abstract Environment protection is now considered as a key point by the population and has become a political and economical stake as related in Kyoto protocol signature which defines objectives for greenhouse effect gases reduction. Based on greenhouse effect gases like carbon dioxide (CO2) and increasing temperature, European Union has implemented an Emission Trading System to give each country emission CO2 targets and a trade tool to share tons of CO2. The European Union has fixed specific objectives to aeronautic section via the Advisory Council for Aviation Research and innovation in Europe. Helicopter community is implementing qualitative tools called environmental metrics to measure the achieved progress. Environmental acoustic metrics have been defined based on noise levels and colors, related to ICAO limitation levels and in the frame of European research project Cleansky. Similarly, environmental metrics for CO2 emission have also been defined based on fuel consumption values and colors. The more the helicopter is environment friendly, the greener the metric. In anticipation of environmental requirements strengthening, some helicopter manufacturers have launched research studies on environmental technologies like Friendcopter project to develop low acoustic level flight procedures based on HELENA computations, or engine manufacturers have invested in technological research projects to improve engine performance and environment impact. In addition, the helicopter product full life cycle is globally considered under the international standard ISO 14001 for environment management as well as human health and environment protection in comparison to REACH European regulation. The reader of the article will certainly notice that the challenge is now: “Towards greener helicopters”.
      PubDate: 2013-05-16
       
  • Virtual autoclave implementation for improved composite part quality and
           productivity
    • Abstract: Abstract State-of-the-art of advanced composite manufacturing uses autoclave devices to ensure the overall curing of the polymer resins for large complex carbon–fibre–polymer composites (CFRP) helicopter structures. A homogeneous temperature distribution on the part surfaces is the key to obtain high and constant quality parts. Local heat transfer coefficients are, therefore, important monitoring factors of autoclave technology processes. Many researchers focussed on the exothermic curing reaction inside the composites, but the surrounding temperature field (inclusive air and mould temperature field) was often neglected. Thus, a thermal uniformity at the surface of the part was often not foreseeable. Due to the 3D arrangements of the parts in the autoclave, together with the design of the tools themselves, strong turbulences and velocity differences are created inside the industrial autoclave, affecting the heat transfer mechanisms at the surface of CFRP parts. Therefore, the temperature field is non-uniform in the spatial and temporal domains. This non-uniform distribution of part and mould temperatures has an important impact on the local degree of cure and on residual stresses in the composite parts. To better understand the process and to optimise the curing cycles, virtual autoclaves have been successfully implemented by MET together with Eurocopter. The validation phase showed very good agreement between measured and simulated temperature fields. On this basis, different internal arrangements of parts for helicopter airframes have been investigated leading to the development of practical solutions to reduce the cycle time, and improve the quality of the parts. Examples of application will be presented together with industrial benefits. This simulation methodology provides Eurocopter with a strong tool for the improvement of composites part quality and productivity. The article content was presented at the Eucomas Conference on February 7, 2012 in Hamburg, Germany.
      PubDate: 2013-04-24
       
 
 
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