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  • 1.
    Ahlmark, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Trajectory Optimization for Aircraft Evasive Maneuvering2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this work has been to identify hidden parameter value patterns during evasive maneuvering for a typical jet fighter. The work has created a performance model for a fighter aircraft and this model has then been combined with a missile model to simulate an enemy attack. By doing different kinds of simulations with a certain amount of predetermined scenarios, different outcomes could be evaluated when making small changes in the maneuvers during each specific scenario. The span of parameters that conducts a flying airplane’s trajectory is vast and the evaluation of different decisions that is up on the table for a pilot in a given situation might give new insights when optimizing tactical air fighting scenarios.After evaluating different scenarios with different input values in form of different turn and climb angles etc, it was clear that small changes resulted in vast differences regarding the outcome, when being chased by the missile. By analyzing the results, it can be concluded that there are underlying patterns regarding controllable parameter values when the airplane tries to get rid of the chasing missile. For example; one section in this work describes that by keeping a straight flight path for a certain amount of seconds after a specified value of turn angle - results in survival of the attack. Keeping level flight for too many seconds however has a lethal outcome. The results seem also to follow a continuous - non-randomized - pattern. This type of detailed analysis could be used to help a pilot to optimizise the performance of the maneuver.

  • 2.
    Ambre, Rombaut
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Landing the Propellant Stage of a launcher2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To reduce the cost of launch, several aerospace companies are exploring the possibility of partly reusable launchers. In order to be reusable with minimum refurbishment cost the reusable part of the launcher has to suffer little damage and land in optimal conditions. In this paper, a guidance algorithm to achieve the return of the reusable vehicle on ground through a vertical landing is described. Different mission scenarios are taken into account and the performance of the guidance algorithm is assessed using a 6 Degrees Of Freedom simulator.

  • 3.
    Aoudia, Thomas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Aircraft Performance Monitoring on Contaminated Runways2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Operations on contaminated runways are a permanent challenge for the aviation community. Among the stakeholders, Airbus has decided to improve its knowledge by developing a fast post-processing software aiming at quickly identifying the runway state on operational recordings. First and foremost, the context of operations on contaminated runways is presented, with a particular emphasis on runway condition assessment methods. In a second part, the models embedded in this function are validated against simulation and more elaborated flight test analysis software. Then, the identification algorithm is validated by comparing its outputs to actual operational conditions. Finally, the robustness of the identification is assessed.

  • 4.
    Bangalore Gangadharacharya, Koushik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Vortex Shedding And Aerodynamic Drag On Truncated Trailing Edge Airfoil2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thesis work content is to evaluate the use of more advanced turbulence models available in the ANSYS CFX software for aerodynamic calculations. In particular for flows over airfoils with thick trailing edges, the turbulence modeling is challenging to traditional methods, as both thin boundary layers as well as an unsteady wake needs to be well represented. This is done by using the standard SST and then performing unsteady computations using the more advanced unsteady SAS-SST model to get the relevant CFD results. By comparing to tests performed at GKN and results from literature the improvement could be assessed in terms of modeling quality and computational cost. The results presented give a good contribution to how the modeling of unsteady wakes can be improved and used for design purposes.

  • 5.
    Bayle, Lucas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Energy Absorption & Improvement Of 1/3 Disc Fragment Model For Turbofan Fan Stage In The Rotor Burst Analysis2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The 1/3 disc fragment model for fan disc burst shall allow aircraft manufacturers to minimize the hazards to the aeroplane without unnecessarily constraining its design. This paper presents a finite energy approach, along with its benefit assessment on the electrical segregation height and rapid decompression rotor burst design constraints. The fan case energy absorption is estimated through the AGARD impact mechanics formula, considering its capability to withstand fan blade-off events. The results for a standardized single-aisle engine suggest 34% energy absorption, 95mm minimum electrical segregation height decrease and 83% rapid decompression maximum opening decrease. The first estimation of energy absorption shows that it is unlikely that the fan retention belt would retain the 1/3 disc fragment. Assumptions regarding material failure, ring shape effect, and blade deformation energy absorption could be refined.

  • 6.
    Blandineau, Pauline
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Wake Vortex Encounter Detection and Severity Assessment from Flight Data2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Hazards associated to Wake Vortex Encounters (WVE) are increasing with the growing traffic and the appearance of super heavy aircrafts such as the A380. The project comes with the need from airports and airlines to clearly analyze the phenomenon by detecting WVE and quantifying their strength from Flight Data Recorder data. A tool is developed with this purpose using Roll Control Ratio as severity metric. Flight data from flight simulator are used for first analyses. The obtained results are encouraging and enable proposed improvements and consideration to further work.

  • 7.
    Borglund, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Robust Aeroelastic Analysis in the Laplace Domain: The μ-p Method2007In: IFASD 2007: International Forum on Aeroelasticity and Structural Dynamics, 2007Conference paper (Other academic)
    Abstract [en]

    In this work the so-called μ-k method for robust flutter analysis is generalized to theLaplace domain. Although the generalization as such is a straightforward matter, the resultingμ-p method is far more versatile than the previous formulation. With the new method, a singlestructured singular value (or μ) evaluation can be used to determine if a certain eigenvalue p is asolution to the uncertain flutter equation or not. This result makes it possible to compute regionsof feasible eigenvalues in the complex plane, as well as extreme eigenvalues that can be used topredict damping bounds and perform robust flutter analysis. The capability to predict dampingbounds at any flight condition is a very attractive feature of the μ-p method, as flight testing israrely taken to the flutter point. This feature also makes it possible to estimate the magnitude ofthe uncertainty based on the measured frequency and/or damping of a particular mode, whichcan reduce the potential conservativeness of the robust analysis. Finally, the capabilities of thenew method is demonstrated by applying it to a low-speed wind tunnel model.

  • 8.
    Borglund, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Robust Eigenvalue Analysis Using the Structured Singular Value: The mu-p Flutter Method2008In: AIAA Journal, ISSN 0001-1452, E-ISSN 1533-385X, Vol. 46, no 11, p. 2806-2813Article in journal (Refereed)
    Abstract [en]

    This paper introduces a new technique for robust aeroelastic analysis that extends standard linear flutter analysis to take deterministic uncertainty and variation into account. The basic principle of the proposed mu-p method is to exploit structured-singular-value (or mu) analysis to investigate if the system uncertainties can make the flutter determinant zero for a given flutter eigenvalue p. This makes it possible to compute regions of feasible eigenvalues in the complex plane as well as extreme eigenvalues that can be used to predict damping bounds and perform robust flutter analysis. The capability to predict damping bounds at subcritical flight conditions is a very attractive feature of the new method, as flight testing is rarely taken to the flutter point. The A-p formulation also opens up new possibilities to bound the magnitude of the system uncertainties based on frequency and/or damping estimates from flight testing. In the final part of the paper, the mu-p framework is successfully applied to perform robust aeroelastic analysis of a low-speed wind-tunnel model.

  • 9.
    Borglund, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Upper-bound flutter speed estimation using the mu-k method2005In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 42, no 2, p. 555-557Article in journal (Refereed)
    Abstract [en]

    The use of upper-bound μ-k estimation method in the development of robust flutter analysis and flutter testing, was described. Since only the frequency-domain aerodynamic forces are required to compute μ(k), established aerodynamic methods can be used for the robust flutter analysis. A robust flutter analysis considering wing-tip aerodynamic uncertainty was developed in MATLAB® for a wind-tunnel model in low-speed airflow. The results show that the extended procedure for robust flutter analysis was successfully applied to a wind-tunnel model in low-speed airflow.

  • 10.
    Borglund, Dan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Ringertz, Ulf
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Efficient computation of robust flutter boundaries using the mu-k method2006In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 43, no 6, p. 1763-1769Article in journal (Refereed)
    Abstract [en]

    A simple and efficient algorithm for robust flutter analysis is presented. First, a general linear fractional transformation formulation of the mu-k method is provided, making it straightforward to pose the uncertain flutter equation in a form suitable for structured singular value analysis. The new formulation establishes a close connection between mu-k flutter analysis and traditional frequency-domain flutter analysis, which is used to formulate an efficient algorithm for computation of robust flutter boundaries. The proposed method is successfully applied to an F-16 sample test case with uncertain external stores aerodynamics, showing that standard tools for structural dynamics and unsteady aerodynamics can be used to perform robust flutter analysis with only modest additional modeling.

  • 11.
    Borglund, Dan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Ringertz, Ulf
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Solution of the Flutter Eigenvalue Problem with Mixed Structural/Aerodynamic Uncertainty2011In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 48, no 1, p. 343-348Article in journal (Refereed)
    Abstract [en]

    The solution of the flutter eigenvalue problem with mixed structural/aerodynamic uncertainty was examined. A delta-wing wind-tunnel model was used as a test case. The model had a simple structural design and was made of glass-fiber and carbon-fiber composite materials. It had a semispan of 0.88 m and mean chord of 0.70m and was mounted vertically in the low-speed wind tunnel L2000. The numerical analysis was based on a NASTRAN model with shell elements for the wing, mass elements for the missile, and aerodynamic panels for doublet-lattice aerodynamic loads. The relatively stiff missile was modeled as a rigid body attached to the wing tip. The nominal eigenvalue was always an interior point of the corresponding eigenvalue set. A parameter sweep taking only aerodynamic uncertainty into account was performed by solving the eigenvalue problem for a set of parameter values. The eigenvalue sets based on one patch and seven patches, respectively, showed only slight difference.

  • 12.
    Borglund, Dan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Ringertz, Ulf
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Solution of the uncertain flutter eigenvalue problem using the μ-p method2009In: IFASD 2009: International Forum on Aeroelasticity and Structural Dynamics, 2009Conference paper (Other academic)
  • 13.
    Borillo Llorca, Irene
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    CFD Analysis and Assessment of the Stability and Control of a Supersonic Business Jet2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Extensive research has been done on the aerodynamics of supersonic aircrafts, especially in the military and commercial airplanes’ field. Regarding supersonic business jets (SSBJs), two major problems have been addressed in past investigations: reducing the sonic boom and decreasing the NOx emissions. This report focuses on a di˙erent aspect, the controls and stability of this type of aircrafts. This field has not been addressed thoroughly by the di˙erent companies and universities investigating SSBJs, as most of the existing concepts are preliminary designs that have not been developed extensively. With this report I try to put my two cents in analyzing the longitudinal stability and control surfaces of three di˙erent SSBJs designs.

  • 14.
    Boschian, Julien
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Flight pro le support on simulators2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper deals with the adaptation of a flight-test tool on A350 simulators in order to support a flight profile. This adaptation has been performed by doing first, an anal- ysis of the current situation of the existing tool on old programs like the A320 or the A330. Then, several modifications on the tool have been performed in order to adapt this tool on simulators. Finally, the validation of this tool has been done by performing several tests on A350 simulators. The difficulty of this adaptation was due to the appari- tion of new state-of-the-art technologies. The main improvement concerned the signals technology that appeared from the A380. Therefore, a modification on the parameters acquisition process has been done to take into account these improvements. Finally, the implementation of this mock-up on A350 simulators consists in a feasibility study that enables simulator test engineers to automate the tests performed on simulators and to do a traceability of these tests. The realisation of this mock-up is necessary because the simulator test engineers need this tool for the end of 2012 in order to develop the A350 whereas the real evolution of this tool will be done when the real aircraft A350 will be produced in 2014.

  • 15.
    Boulangé, Gaëtan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Implementation of Transitional Laminar SeparationBubbles in a Navier-Stokes Code2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Laminar separation bubbles evolve on laminar wing at low Reynolds number.These bubbles have especially been observed on winglets or on wings with flapsor slats. They can stretch up to 30% chord, taking them into account is crucialsince their presence greatly modifies the forces acting on a wing. However, theestablishment of a model is extremely complex and many researches are stillundertaken on this subject. The aim of this work is to achieve automation ofdetecting and taking into account long bubbles in the Navier -Stokes code ofDassault Aviation named Aether. The key issue is the proper detection of thetransition position inside the bubble. This detection is possible by performing alinear stability calculation, but this method is not very robust in this case andvery costly in computation time, as conventional methods are not practicable inthe presence of separation. Finally, the chosen method uses a boundary layercode to predict the position of separation, then a criterion involving local integralquantities to determine the intermittent transition area. This method has beentested for various 2D airfoils and provided quite satisfactory results.

  • 16.
    Bouvattier, Marc-Antoine
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Unstructured mesh adaptation for turbo-machinery RANS computation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper gives an overview of the mathematical and practical tools that can be used in turbo-machinery RANS simulation to realize unstructured mesh adaptation. It first presents the concept of metric and recalls that the hessian of the physical flow properties can become, thanks to small modifications, both a metric and a upper bound of the P1 projection error. The resulting metric is then studied on a simple 2D case. In a second part, the industrial application of this concept is addressed and the tools used to overcome the turbo-machinery specificities are explained. Finally, some 2D and 3D results are presented.

  • 17.
    Brizon, Mathilde
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Solar Energy Generation Model for High Altitude Long Endurance Platforms2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    For designing and evaluating new concepts for HALE platforms, the energy provided by solar cells is a key factor. The purpose of this thesis is to model the electrical power which can be harnessed by such a platform along any flight trajectory for different aircraft designs. At first, a model of the solar irradiance received at high altitude will be performed using the solar irradiance models already existing for ground level applications as a basis. A calculation of the efficiency of the energy generation will be performed taking into account each solar panel’s position as well as shadows casted by the aircraft’s structure. The evaluated set of trajectories allows a stationary positioning of a hale platform with varying wind conditions, time of day and latitude for an exemplary aircraft configuration. The qualitative effects of specific parameter changes on the harnessed solar energy is discussed as well as the fidelity of the energy generation model results.

  • 18.
    Bååthe, Axel
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Transonic Flutter for aGeneric Fighter Configuration2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A hazardous and not fully understood aeroelastic phenomenon is the transonic dip,the decrease in flutter dynamic pressure that occurs for most aircraft configurationsin transonic flows. The difficulty of predicting this phenomenon forces aircraft manufacturersto run long and costly flight test campaigns to demonstrate flutter-free behaviourof their aircraft at transonic Mach numbers.In this project, subsonic and transonic flutter calculations for the KTH-NASA genericfighter research model have been performed and compared to existing experimentalflutter data from wind tunnel tests performed at NASA Langley in 2016. For the fluttercalculations, industry-standard linear panel methods have been used together with afinite element model from NASTRAN.Further, an alternative approach for more accurate transonic flutter predictions usingthe full-potential solver Phi has been investigated. To predict flutter using this newmethodology a simplified structural model has been used together with aerodynamicmeshes of the main wing. The purpose of the approach was to see if it was possibleto find a method that was more accurate than panel methods in the transonic regimewhilst still being suitable for use during iterative design processes.The results of this project demonstrated that industry-standard linear panel methodssignificantly over-predict the flutter boundary in the transonic regime. It was alsoseen that the flutter predictions using Phi showed potential, being close to the linearresults for the same configuration as tested in Phi. For improved transonic accuracy inPhi, an improved transonic flow finite element formulation could possibly help .Another challenge with Phi is the requirement of an explicit wake from all liftingsurfaces in the aerodynamic mesh. Therefore, a method for meshing external storeswith blunt trailing edges needs to be developed. One concept suggested in this projectis to model external stores in "2.5D", representing external stores using airfoils withsharp trailing edges.

  • 19.
    Carré, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Implementation of a large elasto-plastic strain formalism in an industrial finite element code2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis gives a brief sum up of the implementation of a large strain formulation in an existing industrial finite element code. The logarithmic strain tensor additively decomposed in an elastic and a plastic contribution was selected as a basis of this formulation. The main advantage of this formalism is that the existing plastic resolution algorithms written in the small strain formalism can be re-used. Only a pre-processing phase (construction of the logarithmic strain tensor) and a post-processing of the stress tensor is needed. This formulation, detailed in this paper was implemented in FORTRAN and integrated to the existing code. The final implementation was then validated thanks to some benchmarks with Abaqus.

  • 20.
    Constantinescu Birhala, Alexander
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Simulation and analysis of time based operations2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Dubai International Airport has set as an aim to become the leading connecting hub between Europa and Asia. As to be cope with the stresses being put on the airspace in terms of holding times, fuel efficiency and environmental impacts, an analysis has been made concerning the future technology in air traffic management: Time based Operations. This project has revealed that it is possible to maintain the current mean capacity of 29 aircraft/ hour while flying an optimal vertical descent profile. However, exceeding that capacity is not possible with the methods used in this project. The conclusion is that the only forward is Dynamic Controlled of Arrival, together with the reorganization of the entire airspace of Dubai.

  • 21.
    Corti, Fabrizio
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Viability of the overset method for geometrical sensitivity studies2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the following thesis the overset method, also called chimera or overlapping meshes, is discussed and applied toa formula race car, in order to calculate its aerodynamic map. The proposed method would allow reducing set-uptime through automation and avoided re-meshing process. a A theoretical background is presented before thediscussion of the way this kind of approach has been set-up in Star-CCM+. Results are obtained and discussedfor various car positions. Further investigations are finally suggested to further assess the viability of the method.

  • 22.
    Crété, Eloi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Far-field fan noise assessment from in-duct phased array measurements methodology2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The report hereby presents the work performed within the Acoustic design and R&T service of Safran Aircraft Engines in Vi11arnche through a six month master thesis. The service is in charge of the development of noise prediction methods, analysis of tests results, design supervision, definition of specifications. The primary purpose of the present work was to develop a method of assessing the far-field pressure of the turbofan engine without far-field measurements. The foundation of the method relying on a particular signal processing method called beamforming, a complete explanation of the so-called method was realized according to the bibliography, which detects with precision unique modes. The numerical process of the method has been entirely developed, and a law to find the relation between the in-duct and farfield directivity angles was conceived and explained. The validation of the transfer function method was started, using the measurements of a test bench in Ecole Centrale de Lyon.

  • 23.
    Donetti, Guillaume
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Improvement of Post-Processing of Wind Tunnel Data2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper deals with my master thesis done at Airbus Helicopters from the 2nd of February to the 31st of July 2015 in order to complete my studies for the Ecole Centrale de Lille and the Royal Institute of Technology as a double degree student. Airbus Helicopters is the leader on the civil helicopter market and one of the main actors on the military market. Therefore, innovative concepts are perpetually being tested to improve actual rotorcraft. During the development process of a new helicopter, wind tunnel tests are of prime interest to validate the design of different helicopter parts. In that perspective, the goal of my work is to improve the post-processing of wind tunnel data in order to statute about the efficiency of different shapes tested. This is done first by finding relevant handling qualities criteria and values for the aerodynamic coefficients, then by looking at the coefficients computed during wind tunnel tests and comparing them to the criteria to get the optimum configurations.

  • 24.
    Ebrahimi-Oskoei, Ehsan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Swarm of UAVs: Search & Rescue Operationin Chaotic Ship Wakes2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A person falling of a ship can be difficult to locate since the wake behind the ship forms achaotic field, making it extremely difficult to predict the location of the victim even if thetime when they fell overboard is known. Survivability for humans immersed at sea is verydependent on the time spent in the water, and varies significantly with sea temperature; thismakes it imperative that the victim is retrieved rapidly. Our current research is aimed atreducing this time using several UAV's searching the ships wake simultaneously, as a swarm.Since the wake is chaotic, a simulation was developed to model different random motions of avictim based on a chaotic equation. Our current research is making use of an establishedsimulator environment and developing it further to investigate how different platforms mayaffect rescue time, varying on the size of the ship, the weather conditions and whether thesearch is operated during day or night. Two different search strategies were implemented inthe developed simulator; these are Expanding Square search and Parallel search. An overallconclusion based on the results obtained is that the expanding square search tends to be amore rigid and reliable search strategy. Also the results show that for any scenario, the soughtperson is detected within minutes.

  • 25.
    Eller, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    An efficient method for time-domain low-speed aerodynamics: Theory and examples2005Report (Other academic)
  • 26.
    Eller, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Fast, Unstructured-Mesh Finite-Element Method for Nonlinear Subsonic Flow2012In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 49, no 5, p. 1471-1479Article in journal (Refereed)
    Abstract [en]

    A variable-order finite-element method for the solution of the steady nonlinear potential flow equations is presented. To achieve robustness and computational efficiency, the formulation is restricted to purely subsonic flow by means of a density Modification in sonic flow regions. A test case that triggers the activation of this modification is presented to show that the method yields pressure results that are very close to those obtained with a mature Euler solver while reducing computational cost by an order of magnitude. Linear and quadratic elements are implemented, and the substantial benefit of using higher-order elements is demonstrated by means of a mesh-convergence study, showing how the convergence of induced drag and neutral point location is improved by the use or quadratic elements. For large surface meshes, the computational cost is found to be competitive with a linearized-potential boundary-element code accelerated by panel clustering.

  • 27.
    Eller, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Flutter Equation as a Piecewise Quadratic Eigenvalue Problem2009In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 46, no 3, p. 1068-1070Article in journal (Refereed)
  • 28.
    Eller, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Friction, Freeplay and Flutter of Manually Controlled Aircraft2007In: IFASD 2007: International Forum on Aeroelasticity and Structural Dynamics, 2007Conference paper (Other academic)
    Abstract [en]

    The effect of nonlinear friction and freeplay in the control system on flut- ter is investigated for the case of light aircraft with manually operated control surfaces. A standard linear modal subspace model of the aeroelastic system is extended with nonlinear terms, so that time-domain simulations can be per- formed. Furthermore, the harmonic balance method is employed to obtain a frequency-domain formulation, which allows a convenient, though approxi- mate, computation of the stability boundary. Comparison with time-domain analyses for the case of a full aircraft configuration show that typical magni- tudes of hinge friction can stabilize oscillations with small displacement am- plitudes, while large amplitude motion remains unstable. Harmonic balance methods can be used to determine if such a behavior is present, but time- domain computations are necessary to evaluate the response of the system to a given excitation.

  • 29.
    Eller, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Non-iterative solution of the flutter eigenvalue problem using Laplace-domain aerodynamic loads.2009In: IFASD 2009, 2009Conference paper (Other academic)
    Abstract [en]

    An efficient method for the non-iterative solution of the nonlinear flutter eigenvalue problem is presented. The properties of the piecewise quadratic decomposition employed make it particularly suitable for the parallel solution of aeroelastic stability problems where interaction of rigid-body and elastic motion is of interest or where the flutter damping must be obtained with accuracy, e.g. when comparison to flutter flight testing is intended. Ad- ditionally, the method allows the use of Laplace-domain aerodynamics if available. The paper presents a realistically complex test case which exposes some of the advantages and current shortcoming of the proposed solution procedure.

  • 30.
    Eller, David
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Heinze, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Approach to Induced Drag Reduction with Experimental Evaluation2005In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 42, no 6, p. 1478-1485Article in journal (Refereed)
    Abstract [en]

    An approach to minimize the induced drag of an aeroelastic configuration by means of multiple leading- and trailing-edge control surfaces is investigated. A computational model based on a boundary-element method is constructed and drag-reducing flap settings are found by means of numerical optimization. Further, experiments with an elastic wind-tunnel model are performed in order to evaluate the numerically obtained results. Induced-drag results are obtained by analyzing lift distributions computed from optically measured local angles of attack because standard techniques proved insufficient. Results show that significant reductions of induced drag of flexible wings can be achieved by using optimal control surface settings.

  • 31.
    Eller, David
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Jansson, Natascha
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Efficient Laplace-Domain Aerodynamics for Load Analyses2013Conference paper (Refereed)
    Abstract [en]

    An existing finite-element solver for steady, non-linear subsonic flow is extended in order to treat unsteady potential flow problems in the Laplace domain. The numerical formulation makes use of unstructured meshes including explicitly modelled, triangulated wake surfaces. Meshes can contain both linear and quadratic volume and surface elements, thus allowing to favor either very fast solution times or high spatial resolution. Aeroelastic problems are dealt with by modelling moving or deforming bodies by means of transpiration boundary conditions. Deformations of the aerodynamic mesh are computed either by projection of aerodynamic mesh nodes onto the finite elements of a structural shell model, or by radial basis function interpolation suitable for beam-type structural models. In addition to simple validation cases, an application of the solver for the evaluation of gust loads on a commuter aircraft is presented. In order to evaluate the use of the method in the context of a relevant, industrial-scale load analysis, typical geometrical and structural models for a twin-turboprop aircraft in the 15t-class (e.g. Saab 340, CN-235, Dash 8, Do 328) are employed.

  • 32.
    Eller, David
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Tomac, Maximilian
    FS Dynamics Sweden AB.
    Implementation and evaluation of automated tetrahedral-prismatic mesh generation software2015In: Computer-Aided Design, ISSN 0010-4485, E-ISSN 1879-2685Article in journal (Refereed)
    Abstract [en]

    An open-source implementation of an efficient mesh generation procedure for hybrid prismatic-tetrahedral meshes intended for use in Reynolds-averaged Navier-Stokes solutions is presented. The method employed combines the established, and very fast, Delaunay-based tetrahedral mesh generator TetGen with a novel technique for the creation of a prismatic layer, where constrained global optimization of the envelope is employed. Once a well-shaped envelope is thus obtained, a semi-structured layer of pentahedral elements is extruded between wall and envelope surface. Satisfactory mesh quality is demonstrated by comparing solutions obtained using the new meshes with reference data computed on high-quality advancing-front grids. Mesh generation time is shown to be substantially smaller than with many other methods. Overall, the presented implementation is deemed a valuable tool for cases where many meshes need to be generated for routine analyses and turnaround time is critical. 

  • 33.
    Eneault, Yoann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Flow and workstations mechanisation on the Falcon fuselage equipped skin panels production line2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objectives of this study were to prepare the investment for a new facility in order to mechanise the flow and workstations on the Falcon fuselage equipped skin panels production line. This work took part of the in-production reactivity improvement (equivalent to LEAN) project within the company. 

  • 34.
    Ernst, Johannes
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Visualization of Traffic Information in Head-Mounted Displays for Helicopter Navigation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the major challenges for helicopter pilots are low level flights and landings in degraded visual environments (DVE). Without proper assistance systems, the pilots are prone to lose their situational awareness (SA) when fog, heavy precipitation, limited sunlight and stirred-up sand or snow degrades their view. In recent years, various synthetic and enhanced vision systems were de-veloped so as to assist the pilots in these demanding situations. This work enhances the existing sys-tems by proposing a concept for the visualization of traffic information in helmet-/head-mounted displays (HMD). The intuitive representation provides additional cues about the environment and decreases the pilots’ workload, especially during flights in offshore windparks or while search and rescue operations with many other vehicles operating within a small range.The thesis, which was created at Airbus Defence & Space Friedrichshafen, analyzes the strengths and weaknesses of conventional head-down cockpit displays of traffic information (CDTIs) and of a very basic head-up traffic cueing system. Based on the results of this assessment, a prototype implementation of an integrated traffic visualization concept is developed where both display types – HDD and HMD – complement each other in their roles. All traffic information is retrieved from the on-board ADS-B system, which provides data such as the position and velocity vector of ADS-B equipped vehicles in the vicinity.The main focus of the work is placed on the development of methods for de-cluttering the HMD and increasing the information content of the head-up symbology by coding important parame-ters visually. In order to create a de-cluttered representation, the high-dimensional traffic data is clustered with a derivation of DBSCAN so as to identify groups of traffic that can be visualized by a single symbol. Ellipsoidal shapes are applied to airborne traffic while rectangular forms high-light vehicles on ground. To avoid distraction to the pilot due to sudden symbology changes when clusters are merged or split up, a smooth transition visualization method is developed. For the graphical representation of important information on the HMD, a measure indicating the threat potential of an intruder is proposed. This parameter, which is derived from the classification ap-proach of the TCAS II, is visualized by the color of the traffic symbol. In analogy to the TCAS, it is faded from green via yellow to red when the time to a predicted conflict decreases.The realized functions are integrated into a flight simulator and tested with synthetic ADS-B data. Furthermore, the proposed algorithms are evaluated in terms of their effectiveness and run-time efficiency, and finally the advantages and limitations of the approach are discussed. Now, the application must be integrated into an operational synthetic vision system so as to conduct further tests.

  • 35.
    Fargette, Naïs
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Model and simulation of the AS350B1 helicopter2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The continuous progress made in computer science and mathematics has allowed simulation to take a growing place in modern engineering. It is today a strategic stake for research as well as industry. Indeed, it allows a better apprehension of many fields of study, going from physics to biology through economics to mention a few. In aeronautics, simulation might come before production to avoid any fatal error in aircraft safety, or after production as a maintenance tool. It has many purposes, but it is always a compromise between the degree of subtlety of modeling and the calculation capacity of a computer.

    This paper presents and compares two simulation codes in rotorcraft engineering. Both are used professionally by private companies. The main purpose is to enter one complete model of helicopter in both simulation software and to compare their outputs, understanding the models used in each case. The helicopter model is entered gradually, from main rotor to stabilizing back elements. Final results display the outputs of trim simulations performed on both programs.

  • 36.
    Grima, Alexander
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Aerodynamic characterisation of an experimental tilt-wing aircraft2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Computational analysis of experimental aircraft prior to test ights can be a valuable tool to estimate ight characteristics and determine areas of elevated caution. It can also provide feedback to software and model developers as to the accuracy of models used when the aircraft is ultimately own. This paper describes the aerodynamic analysis and characterisation of an experimental tilt-wing aircraft with a unique design. The paper covers what analysis is performed as well as results of these aircraft characterisations. Through this analysis a database le is created for use with NASA Design and Analysis of Rotorcraft (NDARC) tool.

  • 37.
    Hagsved, David
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Johansson, Martin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Evaluation of glider handling qualities2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis was performed with the purpose of investigate what influence different control system characteristics have on pilots' perception of handling qualities. Two gliders were investigated and compared, the JS1 [1] and the ASH26 [2]. Both are high performance gliders with similar type of configuration and aerodynamic performance, but with slightly different handling qualities. The stick force transfer functions in roll axis were calculated, the rate of angular change for a certain control input was measured and the subjective experience of the pilots were acquired through a pilot survey from flight tests. The pilots' experiences were then linked to how the gliders reacted on control input and control system design. It was found that the most important feature of the control system was control harmony, meaning that the responses in each control axis of the glider are in correspondence with each other. Also, the relationship between the stick force and response was much more important than the actual force itself.

  • 38.
    Hatcha, Charles
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Economic Analysis of Hydrogen Production from Wastewater and Wood forMunicipal Bus System2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The levelized cost of hydrogen for municipal fuel cell buses has been determined using the DOE H2A model for steam methane reforming (SMR), molten carbonate fuel cell reforming (MCFC), and wood gasification using wastewater biogas and willow wood chips as energy feedstocks. 300 kg H2/day was chosen as the design capacity.

    Greenhouse gas emissions were calculated for each for the three processes and compared to diesel bus emissions in order to assess environmental impact. The levelized cost for SMR, MCFC, and gasification is $5.12, $8.59, and $10.62, respectively. SMR provided the lowest sensitivity to feedstock price, and lowest levelized cost at various scales, with competitive cost to diesel on a cost/km basis. All three technologies provide a reduction in total greenhouse gases compared to diesel bus emissions, with MCFC providing the largest reduction. These results provide preliminary evidence that small scale distributed hydrogen production for public transportation can be relatively cost-effective and have minimal environmental impact.

  • 39.
    Heinze, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Assessment of critical fuel configurations using robust flutter analysis2006Conference paper (Refereed)
    Abstract [en]

    An approach to assess critical fuel configurations using robust flutter analysis is presented. A realistic aircraft model is considered to demonstrate how an available finite element model can be adapted to easily apply robust flutter analysis with respect to structural variations, such as fuel level variations. The study shows that standard analysis tools can be used to efficiently generate the system data that is required to perform robust flutter analysis. The μ-k method is used to compute the worst-case flutter speed and the corresponding worst-case fuel configuration is found. The main advantage of the proposed approach is that μ analysis guarantees robustness with respect to all possible fuel configurations represented by the tank model.

  • 40.
    Heinze, Sebastian
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Borglund, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    On the influence of modeshape variations in robust flutter analysis2005Report (Other academic)
  • 41.
    Heinze, Sebastian
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Ringertz, Ulf
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Borglund, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Assessment of Uncertain External Store Aerodynamics Using mu -p Flutter Analysis2009In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 46, no 3, p. 1062-1068Article in journal (Refereed)
  • 42.
    Heinze, Sebastian
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Ringertz, Ulf
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Borglund, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    On Uncertainty Modeling and Validation for External Store Aerodynamics2007In: IFASD 2007: International Forum on Aeroelasticity and Structural Dynamics, 2007Conference paper (Other academic)
  • 43.
    Huot, Rémy
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Improving the modeling of the Fenestron® in the Eurocopter Simulation Tool2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main objective of this study carried on among the Flight Mechanics and Loads department of Eurocopter Marignane was to analyze the existing model of the Fenestron named "type 2" and make a separation of the thrust created by the propeller and the one created by the shroud around it. The physics had to be brought back in this model to avoid using tuning parameters. The validity and the reliability of the modeling were then checked with flight tests, wind tunnel and CFD results analysis.

  • 44.
    Hyvärinen, Ann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Investigation of blockage correction methods forfull-scale wind tunnel testing of trucks2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this work wall interference effects, experienced during full scale wind tunnel testing of trucks, are investigatedthrough simulations. Three different truck models are used, and a number of blockage correction methods areapplied on drag results from simulations in a wind tunnel environment. These are compared with open roadreference simulations. The results indicate that the flow fields around the trucks need to be fairly similar, if thesame correction method is to be used.

  • 45.
    Höjner, Patrik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Inerts gas distribution in fighter aircraft2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 46.
    Hövelmann, Andreas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Aerodynamic investigations of noise-reducing high-lift systems for passenger transport aircraft2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This diploma thesis captures the three-dimensional implementation of noise-reducing high-liftsystems. A parametric CAD model is developed for the FNG aircraft and different high-lift configurationsare built up. In the course of research, these configurations are designed based onformerly obtained two-dimensional results of DLR’s LEISA project featuring the design of a verylong chord slat (VLCS), whose slat shape resulted in a favourable aeroacoustic behaviour at noiserelevantapproach conditions. The high-lift systems derived in this thesis differ in the spanwisevariation of the slat geometry planform as well as in the applied high-lift settings described bygap, overlap and deflection angle.The aerodynamic performance is computed via CFD RANS simulations and the results arecompared to a reference high-lift system of the FNG aircraft, which has been designed in previousstudies. The observed CFD results are further evaluated in the reference wing section of the FNGaircraft in order to display the agreement between the implemented 3D high-lift configurationsand the 2D LEISA reference data. Besides the aerodynamic performance, aeroacoustic aspects arealso considered in this diploma thesis. By means of the obtained CFD results, indirect statementsabout the success of the 3D low-noise implementation approach are made.The geometrical concordance of the derived reference wing section of the 3D CAD model isfound in general to be very high in comparison to the 2D-optimized LEISA design wing section.With regard to the observed pressure distributions of the initial four designed high-lift systemshowever, small geometry deviations are noticed to affect the obtained pressure distributions in asignificantly unintended way. The requirements of a low-noise high-lift system are thus not metfor these high-lift configurations. In the 3D implementation, the 2D-optimized slat settings haveto be modified in order to maintain the favourable aeroacoustic behaviour of the 2D considerations.Based on a reduced slat deflection angle, a further derived 3D VLCS high-lift system isobtained to match the 2D-optimized pressure distributions in the reference wing section more accurately.A significant pressure increase at the VLCS trailing edge is noticed for this configuration,which shows the noise-reducing potential of the derived VLCS device. However, the aerodynamicdegradations obtained for the designed low-noise high-lift system are found to be too high in orderto still provide improved aeroacoustic behaviour during conditions of increased approachspeed. A 3D noise-reducing high-lift system is therefore not achieved, although the 2D-optimizedLEISA pressure distributions are well captured in the reference wing section of the implemented3D high-lift system featuring modified high-lift setting parameters.

  • 47.
    Jacamon, Pauline
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Sensitivity study on Duty cycles for Actuator fatigue analysis2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During the aircraft's ight, the control surfaces that enable the aircraft to perform the required maneuvers and the actuator that control them have to withstand loads. Those loads will a ect the actuators lifetime and that is why it is very important to be able to predict their amplitude in order to make sure the actuators will last long enough and be ecient enough during the aircraft lifetime. Duty cycles are thus computed in order to compute the actuators fatigue severity and endurance criteria. The problem is that during the design of a new aircraft, duty cycles generation is very long process. The aim of this thesis it to predict the evolution of actuators fatigue with respect to design parameters in order to reduce computation time during incremental aircraft design.

  • 48.
    Jacob, Catherine
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Generic model for missile  ight dynamics simulation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Simulations are run during early design conception phase in order to have a global overview of the performances and abilities of a given product. Building the aerodynamics and control of a flying device such as a missile requires time and resources. This study focuses on the development of a simplified but accurate enough model of a controlled airframe. The purpose of such a model is to get a good estimation of the behaviour of a given missile. The model has a generic structure which allows it to be adapted to any kind of missile. Given the commanded acceleration in missile frame of reference the simplified model gives the position and the attitude of the missile. A back-to-back validation with a pre-existing model of controlled airframe is performed in order to get the most accurate one. Such a study raises several challenges when it comes to modelling the autopilot or the aerodynamics of the missile. The aerodynamics of this controlled airframe is built such asto require as few aerodynamic parameters as possible. The performances of the simplified controlled airframe meet the expectations of its designers but users have to be aware that this simplified model is limited by its structure: a first-order linear and invariant model cannot describe accurately a whole flight. Further studies on the speed and acceleration ofthe platform when ˝ring and on the controlled but non-guided flight phase can reinforce the model accuracy.

  • 49.
    Jacobsen, Marianne
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    On improving efficiency of flight using optimization2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, optimization is used to improve the performance of aircraft. The focus is on operating current generation aircraft more efficiently rather than designing new aircraft. Drag minimization and aircraft trajectory optimization is used to increase efficiency. Optimization methods are implemented and evaluated on different problem formulations.

    The first part of the thesis presents a drag minimization strategy using multiple control surfaces distributed across the span of an elastic wing. Aeroelasticity is exploited to reduce drag for a wide range of flight conditions. A method to minimize drag during a long distance flight is developed and tested in a wind tunnel environment. The method is based on continuously changing the control surface deflections to obtain a more beneficial load distribution from a drag point of view for the current flight condition. In a second study, the method is extended to include the angle of attack as a variable together with the control surface deflections in the drag minimization algorithm. Extensive wind tunnel testing demonstrates the possibility to reduce drag significantly with the presented method for a wide range of flight conditions.

    The second topic in the thesis is optimizing the aircraft trajectory. The emissions from the aircraft engine are modeled as smooth functions suitable for optimization using published certification data. These emissions are combined in different environmental indices and used as objective functions in the aircraft trajectory optimization problem. The optimization problem is formulated by discretizing the trajectory in time. The resulting large scale nonlinear optimization problem is solved using a sequential quadratic programming method. The trajectory optimization problem is first studied using a model of the Boeing 737 and the results show that the optimal trajectory depends significantly on the definition of the environmental objective function. A method to treat restricted airspace is also presented and evaluated using a model of the Swedish Air Force trainer SK60. The results show that the method for imposing airspace constraints on the flight path works well, especially when the initial point for the optimization is feasible.

     

  • 50.
    Jacobsen, Marianne
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Real time drag minimization using redundant control surfaces2006In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 10, no 7, p. 574-580Article in journal (Refereed)
    Abstract [en]

    A method for minimizing the drag of a wind tunnel model with multiple control surfaces is presented. The minimization is performed in the wind tunnel and measurements are performed in real time. Real time measurements introduce difficulties such as noise in the signals, hysteresis and problems with repeatability of the function evaluations. The lack of a numerical function to minimize therefore puts certain demands on the optimization method, and hence a derivative free method, often referred to as a generating set search method, is used. The proposed method is generalized to take both linear equality constraints as well as linear inequality constraints into account. The generating set search method is implemented in the wind tunnel and tests show that the drag can be decreased while satisfying the constraints.

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