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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 96 journals)
Acta Astronautica     Hybrid Journal   (Followers: 228)
Advances in Aerospace Engineering     Open Access   (Followers: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 242)
Aeronautica     Open Access   (Followers: 7)
Aerospace     Open Access   (Followers: 8)
Aerospace and Electronic Systems, IEEE Transactions on     Hybrid Journal   (Followers: 98)
Aerospace Science and Technology     Hybrid Journal   (Followers: 267)
Affective Computing, IEEE Transactions on     Hybrid Journal   (Followers: 10)
AIAA Journal     Full-text available via subscription   (Followers: 482)
Air Force Magazine     Full-text available via subscription   (Followers: 4)
Air Medical Journal     Hybrid Journal   (Followers: 3)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 116)
American Journal of Space Science     Open Access   (Followers: 38)
Annual of Navigation     Open Access   (Followers: 2)
Artificial Satellites     Open Access   (Followers: 14)
ASTRA Proceedings     Open Access  
Aviation     Hybrid Journal   (Followers: 6)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 3)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 9)
Aviation Week     Full-text available via subscription   (Followers: 21)
Aviation, Space, and Environmental Medicine     Full-text available via subscription   (Followers: 6)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 20)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 25)
Chinese Journal of Aeronautics     Open Access   (Followers: 12)
Control Systems     Hybrid Journal   (Followers: 25)
Cosmic Research     Hybrid Journal   (Followers: 2)
COSPAR Colloquia Series     Full-text available via subscription   (Followers: 1)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 5)
Elsevier Astrodynamics Series     Full-text available via subscription   (Followers: 1)
Fatigue of Aircraft Structures     Open Access   (Followers: 7)
Frontiers in Aerospace Engineering     Open Access   (Followers: 5)
Frontiers in Astronomy and Space Sciences     Open Access  
Gyroscopy and Navigation     Hybrid Journal   (Followers: 117)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 46)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 11)
International Journal of Aeroacoustics     Full-text available via subscription   (Followers: 6)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 11)
International Journal of Aerospace Engineering     Open Access   (Followers: 45)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 12)
International Journal of Aerospace Sciences     Open Access   (Followers: 17)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 4)
International Journal of Aviation Management     Hybrid Journal   (Followers: 3)
International Journal of Aviation Psychology     Hybrid Journal   (Followers: 6)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 1)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 5)
International Journal of Flow Control     Full-text available via subscription   (Followers: 4)
International Journal of Hypersonics     Full-text available via subscription   (Followers: 3)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 4)
International Journal of Satellite Communications Policy and Management     Hybrid Journal  
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 2)
International Journal of Space Structures     Full-text available via subscription   (Followers: 3)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 3)
International Journal of Sustainable Aviation     Hybrid Journal  
International Journal of Turbo & Jet-Engines     Hybrid Journal   (Followers: 1)
Journal of Aeronautical Materials     Open Access   (Followers: 1)
Journal of Aeronautics & Aerospace Engineering     Open Access   (Followers: 1)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 57)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 1)
Journal of Aerospace Information Systems     Full-text available via subscription   (Followers: 1)
Journal of Aerospace Technology and Management     Open Access   (Followers: 2)
Journal of Aircraft     Full-text available via subscription   (Followers: 174)
Journal of Airline and Airport Management     Open Access   (Followers: 5)
Journal of Astrobiology & Outreach     Open Access  
Journal of Aviation Technology and Engineering     Open Access   (Followers: 8)
Journal of Guidance, Control, and Dynamics     Full-text available via subscription   (Followers: 91)
Journal of Konbin     Open Access  
Journal of Navigation     Hybrid Journal   (Followers: 112)
Journal of Propulsion and Power     Full-text available via subscription   (Followers: 172)
Journal of Space Weather and Space Climate     Open Access   (Followers: 4)
Journal of Spacecraft and Rockets     Full-text available via subscription   (Followers: 290)
Journal of Spatial Science     Hybrid Journal   (Followers: 1)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 1)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 2)
Life Sciences in Space Research     Hybrid Journal  
Microgravity Science and Technology     Hybrid Journal  
New Space     Hybrid Journal   (Followers: 2)
Nonlinear Dynamics     Hybrid Journal   (Followers: 5)
Population Space and Place     Hybrid Journal   (Followers: 2)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 6)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 28)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 52)
Propulsion and Power Research     Open Access   (Followers: 4)
Recent Patents on Space Technology     Full-text available via subscription  
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 1)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 19)
Space and Polity     Hybrid Journal   (Followers: 2)
Space Policy     Hybrid Journal   (Followers: 17)
Space Research Today     Full-text available via subscription   (Followers: 27)
Space Safety Magazine     Free   (Followers: 4)
Space Science Reviews     Hybrid Journal   (Followers: 14)
SpaceNews     Free   (Followers: 177)
Transport and Aerospace Engineering     Full-text available via subscription   (Followers: 1)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 2)
Unmanned Systems     Hybrid Journal  
Вісник Національного Авіаційного Університету     Open Access   (Followers: 1)
Вестник УГАТУ     Open Access  
Journal Cover   CEAS Aeronautical Journal
  [25 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1869-5582
   Published by Springer-Verlag Homepage  [2291 journals]
  • Compressor map computation based on 3D CFD analysis
    • Abstract: Abstract The focus of the paper is on procedures and strategies to compute high-fidelity compressor maps for aero engines based on 3D CFD. The developed automatic process starts with an operation point analysis where a convergence checker terminates the running 3D flow analysis as soon as physical quantities such as mass flow or aerodynamic blade row loss have converged. Subsequently, the corresponding compressor speed line is determined, where operation limits like surge and choke are detected by solving optimization and root search problems, respectively. Such speed lines also have to be calculated for various other shaft speeds to obtain the whole performance map. This is achieved by adjusting shaft speed and boundary conditions, where the mesh for variable stator vanes and the amount of bleed mass flow are adapted automatically according to given schedules. Finally, the developed process is applied to a 4.5-stage axial compressor to demonstrate feasibility of the proposed strategies.
      PubDate: 2015-07-25
  • Flap efficiency analysis for the SAGITTA diamond wing demonstrator
    • Abstract: Abstract The efficiency of deflected midboard flaps is investigated on a diamond wing-shaped unmanned aerial vehicle, the SAGITTA demonstrator configuration. The Reynolds-Averaged Navier-Stokes equations are applied to compute numerical results for a variety of flight conditions with varying angle of attack, sideslip angle, and midboard flap deflection. Low-speed wind tunnel conditions are regarded to compare the results to existing experimental data. The focus is particularly laid on the analysis of the aerodynamic coefficients and derivatives in both the longitudinal and the lateral motion. The occurring flow phenomena are motivated and discussed by flow field illustrations that are available from the numerical computations. The results show at small to moderate angles of attack linear flap characteristics, since the overall flow field is dominated by attached flow. With increasing angle of attack and additional sideslip angle, however, the leading-edge vortex originating from the inboard sharp leading edge and the wing tip separation region affect the midboard flap efficiency. Non-linear coupling effects become obvious, which particularly affect the roll and pitch control effectiveness.
      PubDate: 2015-07-03
  • Modeling flows in low-pressure turbine cascades at very low Reynolds
    • Abstract: Abstract This paper presents how transitional flows occurring inside low-pressure turbine cascades can be successfully simulated within a RANS framework. In particular, the emphasis will be put on cascades designed to operate at very low Reynolds numbers. Since such flows are difficult to model, a three-equation model Pacciani et al. (J Turbomach 133(3):031016, 2011), using the concept of laminar kinetic energy has been implemented into DLR in-house turbomachinery specific CFD code TRACE. The detailed implementation of the model and the first results are presented in this paper. The new model has been validated on the T106C turbine cascade. Like in the publication of Pacciani et al, short, long and open separation bubbles are well reproduced. A further assessment of the capability of the model has been carried out: two industrial relevant cascades have been computed. The first blade is an aft-loaded profile while the second blade is a front-loaded profile. For both design types, the agreement between the experiments and the computations is good at low Reynolds number. Notably, the long separation bubble found on the aft-loaded blade is well reproduced. At high values of the Reynolds number, discrepancies occur and are discussed.
      PubDate: 2015-06-01
  • Synergies between suction and blowing for active high-lift flaps
    • Abstract: Abstract The present 2-D CFD study investigates aerodynamic means for improving the power efficiency of an active high-lift system for commercial aircraft. The high-lift configuration consists of a simple-hinged active Coanda flap, a suction slot, and a flexible droop nose device. The power required to implement circulation control is provided by electrically driven compact compressors positioned along the wing behind the wingbox. The compact compressors receive air from the suction slot, which also represents an opportunity to increase the aerodynamic performance of the airfoil. The present work investigates the aerodynamic sensitivities of shape and location of the suction slot in relation to the maximum lift performance of the airfoil. The main purpose of the study is the reduction of the compressor power required to achieve a target lift coefficient. The compressor power requirements can be reduced in two ways: obtaining a high total pressure at the end of the suction duct (compressor inlet) and reducing the momentum needed by the Coanda jet to avoid flow separation from the flap. These two objectives define the guideline of the suction slot design. As a result, a jet momentum reduction of 16 % was achieved for a target lift coefficient of 5 with respect to the same configuration without suction. Furthermore, the study yielded physical insight into the aerodynamic interaction between the two active flow control devices.
      PubDate: 2015-06-01
  • Methods for simulation and analysis of hybrid electric propulsion systems
    • Abstract: Abstract Today, research performed for new aircraft propulsion concepts is driven by the requirement of achieving significant emission reductions to meet the environmental objectives of future air traffic. A current trend visible in the aviation industry shows the attempt to reduce inflight emissions as well as overall energy consumption of conventional combustion engines through electrification via electrical energy sources. With the growing interest in novel hybrid electric propulsion concepts, in the same way, a demand for conceptual design and performance simulation methods in combination with analysis capabilities rises. Based on primarily introduced and discussed hybrid electric propulsion systems, this paper presents a set of aircraft propulsion system simulation (APSS) methods which allow for an integrated simulation and consistent analysis. Particularly, methods for the modelling of electric motor and battery systems as implemented in APSS are described in detail.
      PubDate: 2015-06-01
  • Risks of linear design of joined wings: a non-linear dynamic perspective
           in the presence of follower forces
    • Abstract: Abstract Past work on Joined Wings pointed out the importance of including structural geometric non-linearities since the early stages of the design. However, the attention was mainly focused on conservative loading and several open questions needed an answer. In a effort to simulate aerodynamic-pressure-like loads, this research focuses on non-conservative follower forces. Several numerical evaluations demonstrate that follower loading exacerbates the risks of snap instability in Joined Wings. Snap type of instabilities introduce problems which do not pertain only to static responses. In fact, they are associated with the concept of bi-stable regions, with consequent risks of branch-jumping phenomena which are here shown to happen also for small vanishing perturbations and for load levels that are far from the limit one. The here studied phenomena suggest that the design process for Joined Wings has to be revisited and should focus, when stability is concerned, on the evaluation of the post-critical (if any) response: performing a non-linear analysis until the expected nominal limit load (set, for example, by the flight envelope) is reached is thus, a non-conservative approach and could lead to catastrophical consequences. Unfortunately, the above design directions may not be enough to guarantee a safe design: in this study, a case showing an isola-type of bifurcation is presented. Path-tracking techniques (i.e., arc-length family methods) could not detect such phenomena if not combined with ad hoc dynamic perturbation analyses. A further inherent property of the investigated cases is the sensitivity to parameters (e.g. the lower-to-upper-wing bending stiffness ratio): a small perturbation can produce a sudden appearance of a bi-stable region and isola type of bifurcation. This sensitiveness strongly interferes with the design process, being small deviation from the nominal properties (geometry, material, etc.) unavoidable at manufacturing level.
      PubDate: 2015-06-01
  • Simulation and validation of slat de-icing by an electromechanical system
    • Abstract: Abstract The Electro-Impulse De-Icing system is an alternative process of de-icing wing slat structures made of carbon fiber reinforced plastics or aluminum. It is especially qualified for no-bleed systems that are used in modern and future aircraft. Due to the time-dependent interactions between the induced magnetic field and the structural deformation it can be necessary to couple these physical fields in analyses. This paper presents a three-dimensional simulation as well as experiments of flat plates. The simulation is characterized by electrical and structural finite element calculations, which are two-way coupled in each time step. The current progress is based on real tests which are executed at a special test rig. A coil, which is connected to an impulse generator, is used to induce magnetic forces. Flat plates of aluminum or carbon fiber reinforced plastics (with an additional aluminum doubler) were tested at room temperature and deformation results were used to validate numerical simulations. Further research deals with the simulation of the de-icing process itself with a stress criterion for ice adhesion. Therefore, the test rig is mounted in a cooling chamber. The ice layer is produced by spraying cooled water through a nozzle with a droplet size of supercooled large droplets (SLD). The deformation progress with and without ice is analyzed at different impulse forces and ice thicknesses. The coupled finite element analysis gives the opportunity to simulate the process of de-icing in situ to the time-dependent loading of the plate by magnetic forces. Furthermore, the complex dynamic behavior of the structure can be simulated with excellent agreement to real tests.
      PubDate: 2015-06-01
  • Simulation of thermal behavior during friction stir welding process for
           predicting residual stresses
    • Abstract: Abstract Using a transient thermal finite element analysis, the thermal behavior during friction stir welding (FSW) of aluminum sheets for aerospace applications was calculated. The thermal behavior during the FSW process is of interest for all aspects of distortion engineering or microstructural interpretations for material design. In the presented approach to determine the amount of deformation caused by the thermal residual stresses only, the measured temperature history of the welding tool, the thermomechanical material properties and the thermal contact properties have to be known. Since the calculated time-dependent temperature distribution agrees very well with experimentally measured temperatures at seven different locations during a FSW experiment, it is concluded that the model accurately predicts the thermal history during welding. In addition, a first attempt to calculate the distortion, due to thermal residual stresses, is presented and compared to experimentally measured distortion. Although the calculated values of the distortion are too low compared to experimental results, the approach gives a first impression on the origin of the distortion and will be pursued in further investigations.
      PubDate: 2015-06-01
  • Multidisciplinary pre-design of supersonic aircraft
    • Abstract: Abstract Forecasts predict a strong market for supersonic travel in the business sector. It is especially appealing for high-net-worth individuals because of both, the reduction of travel time and prestige. The ecological and economic challenges that are related to supersonic flight need adequate answers in terms of technology and tools to evaluate aircraft for the described task. This paper gives a short overview on research that has been conducted in the past, followed by the presentation of the work done by the authors. The integration of methods for the evaluation of supersonic business jets in the context of aircraft conceptual design is outlined. The determination of aerodynamic coefficients and loads is done by solving the inviscid Euler equations. Furthermore the propulsion module is extended and a mission analysis tool, which is used for fuel mass estimation is briefly explained. The methods for structural analysis are detailed. At the end the verification based on a reference configuration is described.
      PubDate: 2015-06-01
  • Hybrid structures in aero engines
    • Abstract: Abstract The continuous increase in already high specific performance of aero engines and growing optimization demands require further innovation in the fields of materials and design of structures to reach the primarily aerodynamic driven goals. In general, the improvement of materials on its own cannot guarantee success but rather the combination of different materials offers the potential for increased performance and additional functionality. For using different material properties, an adapted hybrid design is necessary. Within this design outstanding material characteristics should be addressed, whilst the lower performance properties must not be critical and provoke faults. By combining different materials within hybrid structures, the feasible increase in performance is accompanied with the challenges of handling a lot more parameters for optimization. Three examples are described in this paper, showing hybrid design approaches for aero engine structures. The design principles can be transferred to similar structures by using the shown basic mechanisms. The first example covers a hybrid ring structure used for simultaneous movement of stator vanes within an axial compressor. BLISK technology with high aerodynamic efficiency and low structural damping requires an accurate positioning of the stator vanes to avoid dynamic excitation in transient surroundings during a complete flight cycle. Additionally, the weight of the structure should be reduced compared to conventional in-service structures. A second example shows a hybrid fan blade. Here it is demonstrated how titanium can be combined with carbon fibre-reinforced plastics to create an airfoil. This concept can be implemented in generating stator vanes and rotor blades for aero engines. A special surface treatment leads to a non-aging jointbetween the two materials. The third example explains the basics for an alternative hybrid rotor design. Three titanium rotor segments are joined together by brazing under vacuum conditions. During the manufacturing process, the inner areas of the rotor are accessible which offers the opportunity to integrate cavities as well as fibre reinforcement.
      PubDate: 2015-06-01
  • Influence of boundary layer transition on the flutter behavior of a
           supercritical airfoil
    • Abstract: Abstract This paper presents a flutter analysis for the supercritical CAST 10-2 airfoil in a flow with free boundary layer transition based on CFD computations with the \(\gamma \) - \(\hbox {Re}_{\theta }\) transition model. The results are compared to fully turbulent results obtained with the SST \(k\) - \(\omega \) turbulence model. Unsteady RANS computations at \(\hbox {Re}_{\rm{c}} = 2 \times 10^{6}\) are used to determine the aerodynamic derivatives. These derivatives are required to identify the flutter boundary for a 2 degree-of-freedom model by a k method. The transonic flutter boundary decreases for a flow with free boundary layer transition compared to a fully turbulent flow in the vicinity of the transonic dip. However, the flutter boundary at subsonic Mach numbers is raised for a transitional flow. In addition, the transitional frequency response is discussed: an aerodynamic resonance in connection with an instability of the transition region is observed and the possibility of a 1 degree-of-freedom flutter for transitional flows is shown.
      PubDate: 2015-06-01
  • Hybrid-electric propulsion for automotive and aviation applications
    • Abstract: Abstract In parallel with the automotive industry, hybrid-electric propulsion is becoming a viable alternative propulsion technology for the aviation sector and reveals potential advantages including fuel savings, lower pollution, and reduced noise emission. Hybrid-electric propulsion systems can take advantage of the synergy between two technologies by utilizing both internal combustion engines and electric motors together, each operating at their respective optimum conditions. However, there can also be disadvantages to hybrid propulsion. We are conducting an analysis of hybrid-electric propulsion for aircraft, which is looking at modelling systems over a range of aircraft scale, from small UAVs to inter-city airliners. To support the theoretical models, a mid-scale hybrid-electric propulsion system for a single-seat manned aircraft is being designed, built, and tested to generate data for validation and development of the simulation models. This paper draws parallels between the synergy of hybrid-electric propulsion for automotive and aviation applications, and presents an innovative theoretical approach integrating several desktop PC software packages to analyse and optimize hybrid-electric technology for aircraft. Our findings to date indicate that hybrid-electric propulsion can have a significant impact in the small- and mid-scale sectors, but only a minor impact in the large-scale sector assuming battery energy densities predicted for the next decade. Fuel savings of up to 50 and 10 % have been calculated for a microlight aircraft and inter-city airliner, respectively, over the mission profiles considered.
      PubDate: 2015-06-01
  • Characteristics of PEMFC operation in ambient- and low-pressure
           environment considering the fuel cell humidification
    • Abstract: Abstract This paper summarizes experimental results of an air-fed polymer electrolyte membrane fuel cell system HyPM XR 12 (Hydrogenics Corp.) considering fuel cell temperature, stoichiometry, and load requirement variations at ambient and low-pressure operation. The experimental work realized at a low-pressure test facility designed and assembled by the German Aerospace Center, Institute of Engineering Thermodynamics is based on an experimental design. The experimental results confirm reduced fields of fuel cell operation as well as a decreased gross stack performance and efficiency at low operating pressures (950 mbar ≥ p ≥ 600 mbar) for the defined fuel cell temperature, stoichiometry, and load requirement. In addition, indexes of the operating parameters are introduced, characterizing the fuel cell operation with regard to the gross stack performance and efficiency at ambient and low-pressure levels. The discussion of the results considers analyses of fuel cell humidification.
      PubDate: 2015-06-01
  • Effect of an active high-lift system failure during landing approaches
    • Abstract: Abstract Simulation results of the longitudinal motion of a civil twin-engine aircraft with an active high-lift system are presented. The investigated system uses the lift-increasing effect of blowing over Coandă flaps along the wing. The core elements of the nonlinear model describing the dynamic behavior of an aircraft with this specific type of active high-lift system are explained. The main focus lies on the analysis of the aircraft’s reaction to an instant symmetric total failure of such a system. Initial investigations analyze the outcome of such failures, if throttle is set to maximum and elevator is controlled, without using stabilizer or flaps. Subsequently, an investigation has been performed estimating the effect of flap reconfigurations and stabilizer adjustments. The paper also considers a temporary failure of the system due to an engine failure combined with a too low power setting of the remaining engine which has to be increased first before the restart of the blowing system. The investigated situations vary from inconvenient to unrecoverable. Recommendations for backup systems and procedure changes are made to prevent such situations. A procedural approach is analyzed and respective simulations prove the efficiency of this solution.
      PubDate: 2015-06-01
  • A systems architecting framework for optimal distributed integrated
           modular avionics architectures
    • Abstract: Abstract This work presents a novel holistic framework for Distributed Integrated Modular Avionics (DIMA) architecture design and optimization. Integrated Modular Avionics (IMA) are a standardization of avionics components. IMA is beneficial in weight and costs if the complexity of sizing, function allocation, and topology selection is mastered. In preceding publications, stand-alone models and optimization algorithms were developed, which significantly support different aspects of DIMA architecture design. This article extends, integrates, and compares all methods in a holistic framework, which enables model and algorithm-aided design of avionics architectures. Domain-specific modeling of systems software, hardware, and aircraft anatomy enables automated verification and early evaluation of architectures. Moreover, the model is the foundation for a flexible kit of eight optimization routines. For design issues in which humans likely lose the overview optimization routines are proposed. The degree of freedom in optimization ranges from function mapping over routing to a complete architecture generation. Routines for platform selection, network, and topology optimization are unique and unrivaled today. All optimization problems are solved globally optimal and a multi-objective solving algorithm calculates the best trade-off architectures for contradicting objectives, the Pareto optimum. All optimization routines are extensively tested by designing the optimal DIMA architecture for aircraft system functions in an A320-like scenario. Results show significant optimization potential of generated architectures compared to a manually designed one. The resulting architectures are analyzed and compared in performance and structure in detail.
      PubDate: 2015-05-17
  • Collaborative understanding of disciplinary correlations using a
           low-fidelity physics-based aerospace toolkit
    • Abstract: Abstract When performing aircraft design, covering all relevant physical effects and mutual interactions at a sufficient level of fidelity necessitates simultaneous consideration of a large number of disciplines. This requires methods in which teams of engineers simultaneously apply both their analysis modules and knowledge to collaboratively approach design challenges. In the current work, recent technical advancements of the German Aerospace Center (DLR) in data and workflow management are utilised to establish a toolbox containing elementary disciplinary analysis modules. This toolbox is focused on providing fast overall aircraft design capabilities. The incorporated empirical and physics-based low-fidelity modules can be used for setting up modular design workflows, tailored for the considered design cases. This enables the involved engineers to identify design trends at low computational effort. Furthermore, areas of common physical affinity are identified among the engineers, serving as basis for communication. Clear visualisation methods aid in efficiently translating knowledge between the involved engineers within the identified areas of common affinity. In later phases of the design process, the gathered knowledge serves as basis for incorporating modules of higher fidelity. Two application cases guide the present work. In the first application case, a system-of-systems approach is established by applying the elementary aircraft design toolbox to generate requirement sets for engine preliminary design. In this way, a clear synergy is established between the design of both the airframe and power plant. In the second application case, the applicability of a strut-braced wing as potential short-to-medium-range aircraft is investigated by a team of engineers. Within both application cases, methods are applied in which the involved engineers share their knowledge through a collaborative design approach.
      PubDate: 2015-04-29
  • Experimental investigation of turbulent boundary layers over transversal
           moving surfaces
    • Abstract: Abstract The influence of a spanwise traveling transversal surface wave on the near-wall flow field of turbulent boundary layers is investigated by particle-image velocimetry (PIV) and micro-particle tracking velocimetry (μ-PTV). The experimental setup consists of a flat plate equipped with an insert to generate a transversal spanwise traveling wave of an aluminum surface. PIV and μ-PTV measurements are conducted for three Reynolds numbers based on the freestream velocity and momentum thickness immediately downstream of the actuated surface Re θ  = 1200, 1660, and 2080. The transversal traveling wave is generated by a newly developed electromagnetic actuator system underneath the aluminum surface. Three amplitudes A = 0.25, 0.30, and 0.375 mm at a wave length of \(\lambda \, = \,160\,{\text{mm}}\) and a frequency of f = 81 Hz are investigated. The detailed analysis of the velocity profile shows the transversal traveling surface motion to redistribute the velocity in the viscous sublayer and in the logarithmic region of the turbulent boundary layer. The streamwise and wall-normal velocity fluctuations in the outer boundary layer are increased and the streamwise momentum in the near-wall regime is lowered. The drag reduction ratio (DR) due to the actuation is determined by the velocity gradient in the viscous sublayer. At the lowest Reynolds number the drag-reducing impact is proportional to the amplitude of the wave. That is, the higher the amplitude, the more pronounced the drag reduction resulting in a friction drag reduction up to 3.4 % compared to the non-actuated configuration.
      PubDate: 2015-04-25
  • Reduced order modelling for static and dynamic aeroelastic predictions
           with multidisciplinary approach
    • Abstract: Abstract We implement reduced order modelling techniques for aeroelastic predictions of the HIRENASD and S4T wings in order to represent CFD based high-fidelity solutions efficiently. Model reduction techniques such as non-intrusive Polynomial Chaos Expansion and Proper Orthogonal Decomposition are applied to both static and dynamic aeroelastic cases. The high-fidelity solutions are obtained by fluid structure interaction analysis using a 3D Euler unsteady aerodynamic solver and structural modal solution from a finite element solver. The model order reduction strategy is based on a multidisciplinary approach since both structural and aerodynamic input parameters are employed. The model order reduction is performed not only to represent the high-fidelity computational analyses when small variations of input parameters are considered but also to characterize the flutter responses of the S4T wing in a broad range of input values over the entire flight regime for Mach numbers between 0.60 and 1.20. The efficient aeroelastic analyses performed using the developed reduced order models agreed well with the high-fidelity computational analyses.
      PubDate: 2015-04-14
  • Model validation and analysis using feedforward control flight test data
    • Abstract: Abstract The German Aerospace Center (DLR) operates the ACT/FHS research helicopter with a full model-based control system applicable from hover to 120 knots forward flight, including take-off and landing. The feedforward controller used in this system is based on linear model inversion of identified local models. Therefore, the overall performance of the feedforward controller is highly dependent on the accuracy of the used inverted models. While several approaches exist to analyze model accuracy in time and frequency domains, a validation method for inverse models is rarely considered in the literature. In this paper, a flight test campaign that has been conducted to analyze model validity of the feedforward controller is presented and evaluated. A new model validation method using the feedforward controller to follow a reference command is discussed. Measured deviations from the commanded references are evaluated in the time domain to highlight the model subsystems that are not precisely represented by the linear models. The obtained results are compared with a validation method from system identification. Model extensions are proposed to increase the model accuracy for feedforward controller usage.
      PubDate: 2015-03-16
  • Simulation for temperature control of a military aircraft cockpit to avoid
           pilot’s thermal stress
    • Abstract: Abstract During flying, military pilots are normally subjected to a number of stresses like mild hypoxia, high accelerations, vibrations and thermal discomfort. Among all of these, thermal stress is the most predominant factor while operating in highly tropical regions. Despite the use of aircraft’s environmental control system, the temperature inside the cockpit may easily reach more than 10 °C above ambient temperature and sometimes it may even exceed 45 °C. When these extreme temperatures are coupled with high relative humidity, causes for the degradation of both mental and physical performance of the pilots are present. This situation becomes severe, especially during low altitude and high-speed operations due to aerodynamic heating of the external surfaces. Sometimes, at high altitude and low-speed operations, the cockpit temperature falls and cold stress can pose a serious problem on the health of pilots. It is necessary to protect the pilots from high thermal stress to keep them under safe thermoregulatory limits and also help them perform an intended mission. This paper develops and deploys a basic method that can be used at an early design stage of any military aircraft to analyse the environmental control system’s performance in avoiding pilot thermal stress. The method is also applicable to a design study for an enhanced environmental control system on an existing aircraft. Results present the effect of parameters including Mach number, altitude, ambient temperature, cockpit geometry, and solar radiation on cockpit thermal balance which have a direct impact on the thermal stress on pilots. A military aircraft with a cockpit volume of 1.5 m3 is considered for performing the thermal balance simulation studies. This paper also addresses the effects on engine bleed flow requirements, and corresponding air inlet temperatures to maintain the cockpit target wet bulb globe temperature of 28 °C as well as a pilot mean skin temperature target of 33 °C. These are some of the thermal stress indicators proposed by different aero-medical authorities. These requirements are to be maintained if the physiological stress and impairment of performance of the pilots are to be avoided while operating in hot and humid environments.
      PubDate: 2015-01-30
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