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  • 1.
    Ahlén, Patrik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Computation of the Aerodynamic Characteristics of Propellers Using the BEMT-method Including the Condition of Stalled Flow2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The flow around a propeller is complex in nature and has to date still not been completely understood. However, since predicting the aerodynamic characteristics of propellers is an important aspect of the design of aircraft, a number of methods have been devised that by using simplifying assumptions is able to predict the aerodynamic coefficients of interest. One such is the blade element momentum theory method (BEMT-method) which have been found to give accurate results at high advance ratios. At lower advance numbers, where the flow over at least part of the propeller blade is stalled, the theory has traditionally not been found to be as accurate. This report presents a program written in Matlab that, by using the BEMT-method, is capable of predicting the aerodynamic characteristics for a given propeller in the whole operating region, i.e. including low advance ratios. The report include a derivation of the BEMT-equations, as well as a more general discussion of the aerodynamic of propellers, especially focusing on the issues that are important at low advance ratios. The report presents the results from the calculations for a two bladed propeller used on a racing plane, and discuss the issues surrounding the accuracy of the results.

    The BEMT-method have also been used for the calculation of other types of rotors and as an example of this, this report also shows how the BEMT-method can be used for predicting the aerodynamic characteristics of a wind turbine and gives an example of a computation. The result from both of the performed computations shows that the results from the BEMT-method where the blades operate with attached flow has good agreement, while when the flow is stalled the accuracy is less good. Although not numerically in agreement, the results show somewhat of a qualitative agreement.

  • 2.
    Andersson, Niklas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Flödesanalys av befuktarpad: Experiment och simulering2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is well known that the air in an aircraft cabin can be dry and uncomfortable. What is not commonly known is that the human resistants to bacteria and viruses is reduced in this dry air. For long flight the relative humidity inside an aircraft can be reduced to as low as values as 5%, sometimes even lower. This low relative humidity is very extreme and can normaly be found in some deserts. To solve this, the aircraft companies can install humidifiers and raise the relative humidity to more comfortable levels. CTT System has a product which consists of layers of glass fiber sheets which are made wet with a watering system. When the dry air flows through this wet block the water evaporates into the air. This air is then taken to selected parts of the cabin. This project was made to get a deeper understanding of this product. The goal was to investigate two dierent models to simulate the airflow through this humidifier. For this task SOLIDWORKS Flow Simulation was used. It is a commercial Fluid Dynamic solver. To validate the result from the simulation experimental testing have also been done. In the comparison between experimental data and simulated data both pressure drop over the humidifier and velocity profile close after the humidifier have been of interest. The first model is a high detailed CAD version of the humidifier. This model had high demand on mesh quality and the result was time demanding and poor. The second model was a less general model. It constist of a porous block with set properties to match the experimental data. This model had a better prospect and showed a better comparison the experimental data.

  • 3.
    Axelsson, Toni
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Investigation of the Dynamics and Modeling of a Triangular Quadrotor Configuration2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this paper the dynamics of a new type of quadrotor configuration, called Y4, is investigated. The configuration is proposed to be more energy efficient than the traditional design where four rotors are placed around the center of the aircraft frame. This by taking advantage of the benefits of a larger centered rotor in order to produce more lift. A complete mathematical model of the configuration is derived and modeled in the software Simulink. Different control laws is then developed and derived in order to control the Y4, starting with a simple PID control and then moving to non linear control methods using Lyapunov theory. The dynamics of the Y4 is then investigated by simulating different maneuvers, starting with hover and then continuing with attitude, altitude and position maneuvers. The Y4 is shown to be controllable but is less responsive than a typical quadrotor. It show more dynamics of an ordinary helicopter. The conclusion is that the Y4 might have a place in aeronautics if one prioritize power efficiency or lift power and not maneuverability, but still needs the benefits of a VTOL aircraft. However, more research regarding power optimization, design and aerodynamics needs to be done before one can say exactly how much less power the Y4 consumes compared with the standard design.

  • 4.
    Bergman, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Study of the coupled interaction between the wake’s transient behavior and pressure surfaces upstream using Detached Eddy Simulation2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aerodynamic sub-discipline of flow control has for many years been, and still is today, a very prominent subject of research. This field encompasses devices that produce a beneficial change in wall-bounded or free shear flows that may lead to, among many possibilities, reduced drag of ground vehicles and airplanes. The end result could have a substantial improved impact on fuel economy and also introduce new possible design options.

    Creo Dynamics AB recently started to venture into the field of active flow control with huge interest for the technology and its possible applications. One such application includes a system that reduces drag on ground vehicles via the use of active flow control. The system is composed of three components: actuators, controller and sensors. The work carried out in this thesis deals with a study into the sensory placement and control approach related to the system on a very conceptual level.

    According to Creo’s vision of the project the sensor shall record the pressure distribution and characteristics up-stream of the actuators. In turn the algorithm shall be capable of translating and correlating this data to the flow state downstream

    and in the wake. This data is then to be relayed to a control system producing the correct actuation response to achieve desired flow characteristics. For this system to work knowledge about the coupling between wake behavior and pressure distribution on surfaces upstream of the separated flow is necessary. This thesis is an initial investigation into the possible couplings that can be found. The scope also includes investigation of the coupling during cross-winds and gusts.

    Simulations of a simplified car geometry were carried out using the CFD package OpenFOAM and the DDES turbulence model. The initial investigation yielded promising results, showing that a link between the wake behavior and pressure distribution up-stream exists. But further work has to be carried out, as is discussed in the last chapter, before the algorithm according to Creo’s specifications can be constructed.

  • 5.
    Bergstedt, Robin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Aero-Design of Aerodynamically Lifting Struts for Intermediate Compressor Ducts2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Increasing demands on the performance and sustainability of modern turbofan engines put high requirements on each system component, and the limit of what is possible is expected to continue to extend. This thesis focuses on studies on the so-called turning struts concept which aims to shorten the compressor module of a future turbofan engine by introducing aerodynamically modified struts in the compressor mid-frame. Through CFD analysis and low-speed experimental evaluations, this concept is further developed with promising results attained in its early design stages. Important aerodynamic aspects related to this concept are highlighted, and appropriate conceptual design approaches are discussed. It was found that the length of the intermediate compressor duct could be reduced by up to 20% by eliminating the need for the last stator row in the upstream compressor, whilst providing comparable or improved performance compared to conventional designs.

  • 6.
    Berquand, Audrey
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Relative Close Navigation for Non cooperative Rendezvous2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report presents the work done in the frame of a master thesis at Airbus Defence and Space, Les Mureaux on « Relative Close Navigation for Non cooperative Rendezvous » from the 3rd of March to the 29th of August 2014.

    The master thesis subject is the implementation of an initialization algorithm based on Infrared monovision sensors into a pose estimation simulator in the frame of a Non cooperative Rendezvous.

    The pose of a satellite represents its orientation in Euler angles and its relative position to the chaser.

    The initialization algorithm chosen to be implemented is a model-based method involving a Principal Component Analysis. A target template image of size (K, L) pxls is decomposed into a feature vector of size (1, r ). The feature vector contains all the main characteristics of the image. The matching is done via a comparison between a set of feature vectors representing several known target attitudes and the feature vector of the input attitude. The computation load is higly reduced compared to a omparison between images.

    The simulations with simulated images of a basic target shape (a cube) led to accurate attitude and position estimations.The results with real Infrared images inputs give us reasons to believe that the estimations in real space conditions could be conclusive. However, the simulations were done for simplified cases, without, for instance, considering noise measurements. Further studies will have to be done to see if the initialization algorithm allows the simulator tracking algorithm to converge.

  • 7.
    Bérard, Adrien
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Method Development for Computer Aided Engineering for Aircraft Conceptual Design2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents the work done to implement new computational tools and methods dedicated to aircraft conceptual design sizing and optimization. These tools have been exercised on different aircraft concepts in order to validate them and assess their relevance and applicability to practical cases. First, a geometry construction protocol has been developed. It is indeed essential to have a geometry description that supports the derivation of all discretizations and idealizations used by the different analysis modules (aerodynamics, weights and balance, stability and control, etc.) for which an aircraft concept is evaluated. The geometry should also be intuitive to the user, general enough to describe a wide array of morphologies and suitable for optimization. All these conditions are fulfilled by an appropriate parameterization of the geometry. In addition, a tool named CADac (Computer Aided Design aircraft) has been created in order to produce automatically a closed and consistent CAD solid model of the designs under study. The produced CAD model is easily meshable and therefore high-fidelity Computational Fluid Dynamics (CFD) computations can be performed effortlessly without need for tedious and time-consuming post-CAD geometry repair.Second, an unsteady vortex-lattice method based on TORNADO has been implemented in order to enlarge to scope of flight conditions that can be analyzed. It has been validated satisfactorily for the sudden acceleration of a flat plate as well as for the static and dynamic derivatives of the Saab 105/SK 60.Finally, a methodology has been developed to compute quickly in a semi-empirical way the buffet envelope of new aircraft geometries at the conceptual stage. The parameters that demonstrate functional sensitivity to buffet onset have been identified and their relative effect quantified. The method uses a combination of simple sweep theory and fractional change theory as well as the buffet onset of a seed aircraft or a provided generic buffet onset to estimate the buffet envelope of any target geometry. The method proves to be flexible and robust enough to predict within mainly 5% (and in any case 9%) the buffet onset for a wide variety of aircrafts, from regional turboprop to long-haul wide body or high-speed business jets.This work was done within the 6th European framework project SimSAC (Simulating Stability And Control) whose task is to create a multidisciplinary simulation environment named CEASIOM (Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods), oriented toward stability and control and specially suited for aircraft conceptual design sizing and optimization.

  • 8.
    Bérard, Adrien
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Isikveren, Askin
    University of Bristol.
    Conceptual Design Prediction of the Buffet Envelope of Transport Aircraft2009In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 46, no 5, p. 1593-1606Article in journal (Refereed)
    Abstract [en]

    This paper describes a methodology that inexpensively predicts the buffet envelope of new transport airplane wing geometries at the conceptual design stage. The parameters that demonstrate a strong functional sensitivity to buffet onset were identified and their relative effect was quantified. To estimate the buffet envelope of any target aircraft geometry, the method uses fractional change transformations in consort with a generic reference buffet onset curve provided by the authors or the buffet onset of a known seed airplane. The explicit design variables required to perform buffet onset prediction are those describing the wing planform and the wingtip section. The mutually exclusive nature of the method's analytical construct provides considerable freedom in deciding the scope of free-design-variable complexity. The method has been shown to be adequately robust and flexible enough to deal with a wide variety of transport airplane designs. For the example transport airplanes considered, irrespective of aircraft morphology and en route flight phase, the relative error in prediction was found to be mostly within +/-5.0%, with occasional excursions not exceeding a +/-9.0% bandwidth. The standard error of estimate for the lift coefficient at 1.0 g buffet onset at a given Mach number was calculated to be 0.0262.

  • 9.
    Bérard, Adrien
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Isikveren, Askin
    Dept. of Aerospace Engineering, University of Bristol.
    CADac: A New Geometry Construction Tool for Aerospace Vehicle Pre-Design and Conceptual Design2008In: 26th AIAA Applied Aerodynamics Conference: Honolulu, HI: 18 August 2008 through 21 August 2008, 2008Conference paper (Refereed)
    Abstract [en]

    In view of a continuous increase of computer performance, it is nowadays feasable to use CFD (Computational Fluid Dynamics) analysis very early in the conceptual design stage, if not the pre-concept phase, of aircraft. This requires the generation of a CAD (Computer Aided Design) model suitable for CFD computations, which is a tedious and time consuming process because a disconnect exists between the geometrical definition required for a CAD model and the limited number of geometry related design parameters defined by the designer. An additional complication to this is the requirement of producing a closed and consistent CAD model suitable for problem setup of CFD computations. The CADac (CAD-aircraft) tool nils this gap by automating the generation of closed and consistent CAD models via the implementation of a parameterized approach to conceptual design. CADac enables therefore to use CFD earlier and to use tools with inter-laced fidelity at the conceptual design phase.

  • 10.
    Bérard, Adrien
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Isikveren, Askin
    Development and Implementation of Aerodynamic Analysis Methods for Aircraft Conceptual Design2007Conference paper (Other academic)
  • 11.
    Catalon, Matthieu
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Attitude Control of the Spacecraft TARANIS:Sun Acquisition Robustness2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper deals with the study of the robustness concerning the attitude control of the spacecraft TARANIS regarding disturbances on its sun acquisition sensors. Two kinds of disturbances have been studied: the masking of the sunlight by the dierent spacecraft devices as well as the sunlight reexion on their surface. This study has been performed by doing rst the sensor and observer modeling on a simulator specially designed for the study from the whole spacecraft simulator. Then the modeling of the disturbances has been achieved depending on the characteristics of the sources in terms of size, positioning, roughness and light reection. Finally a set of simulations of the acquisition and survival mode has been executed in order to evaluate the impact of the disturbances on its convergence time. The study shows that the algorithm designed to calculate the spacecraft attitude from the solar sensors data set is robust concerning these disturbances with the actual design of the satellite, but also shows limits concerning the size and positioning of its devices.

  • 12.
    Cavagna, L.
    et al.
    Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano.
    Riccobene, L.
    Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano.
    Ricci, S.
    Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano.
    Bérard, Adrien
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    A Fast MDO tool for Aeroelastic Optimization in Aircraft Conceptual Design2008Conference paper (Other academic)
    Abstract [en]

    This paper presents a design tool based on computational methods for the aero-structural analysis and optimization of aircraft layouts at the conceptual design stage. The whole methodology is based upon the integration of geometry construction, aerodynamic and structural analysis codes that combine depictive, computational, analytical, and semiempirical methods, validated in an aircraft design environment. The two primary modules are presented: CADac (Computer Aided Design Aircraft) for parametric geometry handling and NeoCASS (Next generation Conceptual Aero-Structural Sizing Suite) for structural sizing and numerical aeroelastic analysis. The aero-structural numerical kernel enables the creation of efficient low-order, high fidelity models which makes particularly suitable to be succesfully used within an MDO framework to drive the optimization tool into the most appropriate direction. Indeed, solving adverse aeroelastic issues like divergence, control surfaces reversal, flutter, increased drag at cruise speed due to structural deformability may require considerable changes in the structural design, limitations in flight envelope or weight penalties. The late discovery of this type of issues may result in significant cost increases and, in some cases, it may even require to actually close the project. In order to overcome the insurgence of these issues, the influence of deformability on flight and handling performances, on structural weight and on design costs needs to be taken into account as early as possible in the design process.

  • 13.
    Chatelier, Adrien
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Toward the study of combustion instabilities in aircraft engines2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The prediction of combustion instabilities is crucial for aircraft engines manufacturers to ensure the reliability and the life span of their engines. To study these phenomena, numerical simulations are more and more often performed. They o er advantages: a wide range of parameters is available, they are safe and inexpensive compared to experiments.

    This work presents a rst step in the general study of combustion instabilities. Firstly, several tools for acoustics and combustion are validated. The tests are performed on simple cases which have reference solutions from analytical resolution or measurements, such as one dimensional ames for combustion and rectangular duct for acoustics. The parameters of these cases are close to the more complex ones. Then, the dynamics of a laminar ame are studied. Finally, a laboratory scale conguration is explored. Kinetics for a methane-air mixture are validated as well as the TFLES model for combustion. The AVSP code for acoustics correctly determines the eigenmodes of a simple conguration.

    The TFLES model on a pulsed ame has a signicant impact on its dynamics, depending on the thickening factor and the model used. An unstable mode is found for reacting RANS computations of a laboratory scale conguration. An unstable mode is also predicted by AVSP computations with an active ame model. Even if further work is needed to develop these tools, the rst results indicate that they can quickly yield predictions about combustion instabilities.

  • 14.
    Colo, Ludovic
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Study of Various Methods for Modeling Gust Penetration2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Gust load computations are one of the various load cases computations required by the regulation in order to get an aircraft certified. These loads can even be the ones which have to be used for the structural sizing of the vertical and horizontal tail or the main wing of the aircraft. Three numerical methods to model penetration into a cylindrical gust are presented and their results are compared in terms of loads prediction on the structure. The influence of model parameters is studied and some general thoughts about delay and penetration are gathered. It is shown that the spatial discretization of the phenomenon does not need to be fine to yield accurate results and that different treatments of aerodynamic interactions between the subparts of an aircraft might bring rather large discrepancies in the results. In order to evaluate whether these numerical methods predict realistic loads, a comparison between experimental data and numerical computations on a simple wing profile is performed.

  • 15.
    Cöllen, Liana
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Standardized Geometry Formats for AircraftConceptual Design and Physics-basedAerodynamics and Structural Analyses2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 16.
    Da Ronch, A.
    et al.
    Department of Engineering, University of Liverpool, UK.
    McFarlane, C.
    Department of Aerospace Engineering, Bristol University, UK.
    Oppelstrup, Jesper
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.
    Zhang, Mengmeng
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Benchmarking CEASIO software to predict flight control and flying qualities of the B-7472010In: 27th International Congress of the Aeronautical Sciences, ICAS 2010, 2010Conference paper (Refereed)
  • 17.
    Dahan, Jeremy
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Futrzynski, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Aero-acoustic source analysis of landing gear noise via dynamic mode decomposition2014In: 21st International Congress on Sound and Vibration, ICSV21: / [ed] Malcolm J. Crocker, Marek Pawelczyk, Jing Tian, 2014, Vol. 2, p. 1245-1252Conference paper (Refereed)
    Abstract [en]

    In this paper, we apply dynamic mode decomposition (DMD) on time accurate simulationsof the pressure distribution on a realistic full-scale noselanding gear configuration in order toidentify noise generating structures on landing gear surfaces. The simulated pressure data isobtained from DES simulations using the commercial software STAR-CCM+ by CD-adapco.The dynamics of the surface pressure on a tyre are discussed and the DMD modes are com-puted from instantaneous pressure snapshots. The far-fieldnoise is determined via the FfowcsWilliams-Hawkings analogy, where a given frequency band source term can be reconstructedby choosing an appropriate number of DMD modes.

  • 18.
    Ekelöw, Jakob
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Design and manufacturing of thin composite tape springs2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A manufacturing method for tape springs in a deployment system for a nano satellite was developed. The system relies on composite tape springs for deployment force and post deployment structural integrity, and has been proposed and used in several previous nano satellites. The tape spring was made of preimpregnated glass fiber weave. Initial test verifying the tape springs functions have been made and proven successful. The tape springs have also been tested in an engineering model of the satellite and are able to perform an adequate deployment.

    Further tests, especially long time storage are needed the tape spring solution for the deployment system looks promising.

  • 19. Eliasson, P.
    et al.
    Vos, J. B.
    Da Ronch, A.
    Zhang, Mengmeng
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Virtual aircraft design of transcruiser - Computing break points in pitch moment curve2010In: 28th AIAA Applied Aerodynamics Conference, 2010, p. 2010-4366-Conference paper (Refereed)
    Abstract [en]

    The SimSAC project has developed the design software CEASIOM, a framework tool that integrates discipline-specific tools like CAD & grid generation, CFD, stability & control analysis etc. for the purpose of aircraft conceptual design. Significant features developed and integrated in CEASIOM are geometry, aerodynamics, flight dynamics and aeroelasticity modules. The design begins with a design specification and uses conventional design methods to prescribe a baseline configuration. Then CEASIOM improves upon this baseline by analyzing its flying and handling qualities. This paper reports on the Transonic cruiser TCR from baseline design to Tier-I design. The baseline T-tail design is based on the design specification, which is a fairly non-complicated one with the exception for the design cruise speed of Mach 0.97. The flight dynamical analysis in CEASIOM of this configuration showed that trimming the aircraft required too large deflections in the design point so a new approach with a canard configuration was designed. A model of this configuration was built and tested in wind tunnel. The paper focuses on the validation of computational tools of different fidelity, from Tier I to Tier II RANS solvers, with test data to get a range of fidelity of the tools. The results showed that Tier I methods fail to reproduce experimental pitch moment already at moderate angles of attack. Euler methods give reasonably accurate predictions but only RANS offers good overall experimental agreement for all angles attack, in particular at higher angles where the flow starts to separate.

  • 20.
    Favre, Tristan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Aerodynamics simulations of ground vehicles in unsteady crosswind2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ground vehicles, both on roads or on rail, are sensitive to crosswinds and the handling, travelling speeds or in some cases, safety can be affected. Full modelling of the crosswind stability of a vehicle is a demanding task as the nature of the disturbance, the wind gust, is complex and the aerodynamics, vehicle dynamics and driver reactions interact with each other. 

    One of the objectives of this thesis, is to assess the aerodynamic response of simplified ground vehicles under sudden strong crosswind disturbances by using an advanced turbulence model. In the aerodynamic simulations, time-dependant boundary data have been used to introduce a deterministic wind gust model into the computational domain. 

    This thesis covers the implementation of such gust models into Detached-Eddy Simulations (DES) and assesses the overall accuracy. Different type of grids, numerical setups and refinements are considered. Although the overall use of DES is seen suitable, further investigations can be foreseen on more challenging geometries. 

    Two families of vehicle models have been studied. The first one, a box-like geometry, has been used to characterize the influence of the radius of curvature and benefited from unsteady experimental data for comparison. The second one, the Windsor model, has been used to understand the impact of the different rear designs. Noticeably, the different geometries tested have exhibited strong transients in the loads that can not be represented in pure steady crosswind conditions.

    The static coupling between aerodynamics and vehicle dynamics simulations enhances the comparisons of the aerodynamic designs. Also, it shows that the motion of the centre of pressure with respect the locations of the centre of gravity and the neutral steer point, is of prime interest to design vehicles that are less crosswind sensitive. Recommendations on the future work on crosswind sensitivity for ground vehicles are proposed at the end of this thesis.

  • 21.
    Favre, Tristan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Numerical Investigation of Unsteady Crosswind Aerodynamics for Ground Vehicles2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ground vehicles are subjected to crosswind from various origins such as weather, topography of the ambient environment (land, forest, tunnels, high bushes...) or surrounding traffic. The trend of lowering the weight of vehicles imposes a stronger need for understanding the coupling between crosswind stability, the vehicle external shape and the dynamic properties. Means for reducing fuel consumption of ground vehicles can also conflict with the handling and dynamic characteristics of the vehicle. Streamlined design of vehicle shapes to lower the drag can be a good example of this dilemma. If care is not taken, the streamlined shape can lead to an increase in yaw moment under crosswind conditions which results in a poor handling.

    The development of numerical methods provides efficient tools to investigate these complex phenomena that are difficult to reproduce experimentally. Time accurate and scale resolving methods, like Detached-Eddy Simulations (DES), are particularly of interest, since they allow a better description of unsteady flows than standard Reynolds Average Navier-Stokes (RANS) models. Moreover, due to the constant increase in computational resources, this type of simulations complies more and more with industrial interests and design cycles.

    In this thesis, the possibilities offered by DES to simulate unsteady crosswind aerodynamics of simple vehicle models in an industrial framework are explored. A large part of the work is devoted to the grid design, which is especially crucial for truthful results from DES. Additional concerns in simulations of unsteady crosswind aerodynamics are highlighted, especially for the resolution of the wind-gust boundary layer profiles. Finally, the transient behaviour of the aerodynamic loads and the flow structures are analyzed for several types of vehicles. The results simulated with DES are promising and the overall agreement with the experimental data available is good, which illustrates a certain reliability in the simulations. In addition, the simulations show that the force coefficients exhibit highly transient behaviour under gusty conditions.

  • 22.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics.
    An Assessment of Detached-Eddy Simulations of Unsteady Crosswind Aerodynamics of Road Vehicle2011In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 87, no 1, p. 133-163Article in journal (Refereed)
    Abstract [en]

    An extensive study of the mesh requirements when simulating unsteady crosswind aerodynamics for industrial applications is conducted and reported in this article. Detached-Eddy Simulations (DES) of a simple car geometry under headwind, steady crosswind and time-dependent wind gust are analysed for different meshes and flow cases using a commercial software, STAR-CD. The typical Reynolds number of the cases studied is 2.0x106 based on the vehicle length. Mesh requirements for capturing the time development of the flow structures during a gust is provided. While respecting these requirements, the aerodynamic coefficients can be reliably calculated. Using turbulence methods like DES in order to resolve the flow scales provides a significant insight for designing a ground vehicle and, due to the reasonable computational times involved, can be incorporated in a design process in a near future.

  • 23.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Detached-Eddy Simulations of the Effects of Different Wind Gust Models on the Unsteady Aerodynamics of Road Vehicles2010In: ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels (FEDSM2010), 2010, p. 2605-2614Conference paper (Refereed)
    Abstract [en]

    Therelative flexibility of nowadays simulation techniques offers an alternative wayto experiments in order to investigate unsteady crosswind aerodynamics inan industrial framework. In this study, time-accurate simulations, Detached-Eddy Simulations(DES), are used to simulate the flow around a simplevehicle shape, the so-called Windsor model. The ReL of thecorresponding flow case is 2.0 · 106. The influence ofdifferent deterministic models of wind gusts on the aerodynamic loadsand moments are studied. The wind gusts are varied inthe stream-wise and the vertical direction. The magnitude of thegusts models corresponds to a yaw angle of 20°. Theaerodynamic loads calculated show a large excess of drag coupledwith a reduction of the pitch moment. In addition, althoughthe side force has a smooth variation in the gust,overshoots up to 18% higher than the steady value ofyaw moment are also observed.

  • 24.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Effects of Deterministic Wind Gusts on Unsteady Crosswind Aerodynamics of Road Vehicles2009Report (Other academic)
    Abstract [en]

    The relative flexibility of nowadays numerical methods offers an alternative way to experiments in order to investigate unsteady crosswind aerodynamics in an industrial framework. In this study, time accurate methods such as Detached-Eddy Simulations (DES) are used to simulate the flow. A simple vehicle shape, the so-called Windsor model, is chosen for the model. The ReL of the corresponding flow case is 2.0x106. Then, different deterministic models of wind gusts that are varied in the streamwise and the vertical direction are tested. The magnitude of the gusts models corresponds to a yaw angle of 20o. The aerodynamic loads calculated show a large excess of drag coupled with a reduction of the pitch moment. Although the side force has a smooth variation in the gust, overshoots up to 18% higher than the steady value of yaw moment are also observed.

  • 25.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Numerical study of design alterations affecting the crosswind characteristics of a generic road vehicle model2010In: Eighth World MIRA International Vehicle Aerodynamics Conference, 2010Conference paper (Refereed)
  • 26.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics.
    Unsteady mechanisms in crosswind aerodynamics for ground vehicles2011Report (Other academic)
  • 27.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Diedrichs, B.
    Numerical Investigation of Unsteady Crosswind Vehicle Aerodynamics using Time-Dependent Inflow Conditions2008In: Seventh World MIRA International Vehicle Aerodynamics Conference, 2008Conference paper (Refereed)
    Abstract [en]

    Transient disturbances concerning ground vehicles are not only due to rail or road irregularities but are also caused by unsteady ambient wind conditions. This study presents a numerical investigation of unsteady crosswind aerodynamics by using the commercial software STAR-CD from CD-Adapco. The unsteadiness of the aerodynamics is introduced through time-dependent inflow boundary conditions that describe a jet flow according to Schlichting [1]. The purpose of this study is to explore the validity of the commonly used numerical methods (URANS and DES) for the current crosswind application. To this end, simplified vehicle geometries are utilized, for which the experimental results of Chadwick et al. [2] are used as reference data.

  • 28.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Elofsson, Per
    Scania.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics.
    Detached-Eddy simulations of simplified vehicles in steady and unsteady crosswindArticle in journal (Other academic)
  • 29.
    Favre, Tristan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Jarlmark Näfver, Jonas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics.
    Static coupling between detached-eddy simulations and vehicle dynamic simulation of a generic road vehicle model in unsteady crosswind with different rear configurationsArticle in journal (Other academic)
  • 30.
    Foresto, Paul
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    A Global Approach for Fan Flutter Identication2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to progress in CFD (Computational Fluid Dynamics), it is now possible to compute and analyzesteady ow and phenomena for turbomachine design. Unsteady instability predictions are important tocertify that a turbomachine will not encounter high vibration levels in operation. Flutter is one of the mostcommon fan instabilities. Thus, the fan design is bound to respect a given Flutter Margin. It guaranteesa certain operation envelope for the engine and its fan, refered as operability. The operation envelope ofan engine is dened in the fan map mass ow rate - pressure ratio as the space in which the engine can berun in during operation. The fan map is made of isovelocities. An isovelocity is a line described by varyingmass ow rate and keeping constant the rotational speed. This domain is bounded by phenomena such asrotating stall, surge, utter, etc which are hazardous for engine mechanical integrity. Fig. 1 highlights howan operating envelope is bounded. When operation envelope is too small, the fan blade geometry needsto be modied to improve its utter behavior and therefore increase the size of the envelope. Eciency,pressure ratio and operability can be strongly impacted by the changes made. Therefore design parametersinuencing utter must be precisely spotted. This can be done if mechanisms which trigger utter are wellunderstood. Thus the blade can be reshaped to lower the contribution of a given phenomenon. However,when a phenomenon is identied, one should quantify its contribution to the globally stable or unstablebehavior. In fact, to reduce the geometrical changes and therefore consequences on operability, one shouldact on the most critical phenomenon.The study has been performed on a single fan blade with dierent congurations of back pressure androtational speed. Consequently, two kinds of utter are investigated : stall utter and transonic utter. Therst one occurs at low rotational speed. It corresponds to zone 1 in Fig. 1. It is commonly driven by owseparation. As described in,1 separation on the suction side of a blade can be responsible for utter. Article1shows that unsteady pressure and blade motion are out of phase in the separated zone. Furthermore, studiesin2 reveal that traveling Mach waves on the blade surface can destabilize it. It depends on the phase betweenthe waves and the blade motion. Acoustic interference is also studied in.1 Transonic utter occurs at higherrotational speed when the blade is shocked. It corresponds to zone 2 in Fig. 1. There are two main sourcesthat destabilize the blade: interaction between the shock waves and the boundary layer and the shock waveoscillation as presented in.3 That study divides the prole into four parts. Each part corresponds to a givenmechanism: supersonic part (stabilizing), shocked part (both stabilizing and destabilizing if the shock wavesoscillates), downstream the shock (destabilizing due to separation) on the suction side and the pressure side(stabilizing).The objective of this paper is not only to identify mechanisms responsible for utter at low and high rotationalspeed but also to follow their evolution along an isovelocity. A global approach from the mechanismsidentication to the quantication of the phenomenon is then described.The critical mechanisms responsiblefor fan blade utter for a given conguration can be pointed out.

  • 31. Frink, N. T.
    et al.
    Tomac, Maximillian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Collaborative study of incipient separation on 53°-swept diamond wing2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219Article in journal (Refereed)
    Abstract [en]

    A systematic analysis of incipient separation and subsequent vortex formation from moderately-swept blunt leading edges is presented for a 53°-swept diamond wing. This work contributes to a collective body of knowledge generated within the multinational NATO/STO AVT-183 Task Group titled "Reliable Prediction of Separated Flow Onset and Progression for Air and Sea Vehicles". Details of vortex formation are inferred from numerical solutions of two flow solvers after establishing a good correlation of the global flow field and surface pressure distributions with those from wind tunnel measurements. From this, significant and sometimes surprising insights into the nature of incipient separation and part-span vortex formation are derived from the wealth of information available in the computational solutions.

  • 32. Ghoreyshi, M.
    et al.
    Badcock, K. J.
    Da Ronch, A.
    Vallespin, D.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Automated CFD Analysis for the Investigation of Flight Handling Qualities2011In: Mathematical Modelling of Natural Phenomena, ISSN 0973-5348, E-ISSN 1760-6101, Vol. 6, no 3, p. 166-188Article in journal (Refereed)
    Abstract [en]

    Physics based simulation is widely seen as a way of increasing the information about aircraft designs earlier in their definition, thus helping with the avoidance of unanticipated problems as the design is refined. This paper reports on an effort to assess the automated use of computational fluid dynamics level aerodynamics for the development of tables for flight dynamics analysis at the conceptual stage. These tables are then used to calculate handling qualities measures. The methodological questions addressed are a) geometry and mesh treatment for automated analysis from a high level conceptual aircraft description and b) sampling and data fusion to allow the timely calculation of large data tables. The test case used to illustrate the approaches is based on a refined design passenger jet wind tunnel model. This model is reduced to a conceptual description, and the ability of this geometry to allow calculations relevant to the final design to be drawn is then examined. Data tables are then generated and handling qualities calculated.

  • 33. Ghoreyshi, M.
    et al.
    Da Ronch, A.
    Badcock, K. J.
    Dees, J.
    Bérard, Adrien
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Aerodynamic modelling for flight dynamics analysis of conceptual aircraft designs2009In: 27th AIAA Applied Aerodynamics Conference, 2009Conference paper (Refereed)
    Abstract [en]

    Physics based simulation in conceptual design is widely seen as a way of increasing the information about designs, thus helping with the avoidance of unanticipated problems as the design is refined. This paper reports on an effort to assess the use of CFD level aerodynamics for the development of tables for flight dynamics analysis at the conceptual stage. A number of aerodynamic data sources are used with sampling and data fusion to allow the efficient generation of the tables. A refined design passenger jet wind tunnel model is used as a test case, and three simplified conceptual versions of this geometry are generated. The influence of geometry approximations and modelling influences are evaluated to assess the usefulness of CFD for this application. Finally, the aerodynamic differences are assessed in terms of basic longitudinal flight dynamics analysis.

  • 34.
    Goetzendorf-Grabowski, Tomas
    et al.
    Institute of Aeronautics & Applied Mechanics, Aircraft Design Department, Warsaw University of Technology, 00-665 Warsaw, Poland.
    Vosy, J.B.
    Sanchiz, S.
    Molitor, Paul
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Tomac, Maximilian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Coupling Adaptive-Fidelity CFD with S&C Analysis to Predict Flying Qualities2009In: 27th AIAA Applied Aerodynamics Conference, 2009Conference paper (Refereed)
    Abstract [en]

    CEASIOM, the Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods, is a framework tool that integrates discipline-specific tools for conceptual design. At this early stage of the design it is very useful to be able to predict the °ying and handling qualities of this design. In order to do this, the aerodynamic database needs to be computed for the configuration being studied which then has to be coupled to the stability and control tools to carry out the analysis. This paper describes how the adaptive-fidelity CFD module of CEASIOM computes the aerodynamic dataset of an air craft configuration, and how that dataset is analyzed by the SDSA module to determine the °ying qualities of the aircraft. These predicted °ying qualities are then compared with the °ight-test data of the Ranger 2000 trainer aircraft in order to verify the goodness of the overall approach.

  • 35.
    Grimaldi, Guillaume
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    CFD Validation of the Engine Air Intake wind tests2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main objective of this study carried on within the Aerodynamics department of Airbus Helicopters Marignane was to validate the Engine Air Intake tests with a CFD model of the helicopter including the whole wind tunnel building. The quantities which have been validated were aerodynamic criteria presented in the below parts. This study was done in order to improve the method and tools of the Airbus Helicopters Aerodynamic Department. The modeling has been improved during this study in order to make the computations results closer to the wind tunnel tests results.

  • 36.
    Guillard, Victor
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Study of the Fan Forced Response due to Crosswind2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Structures of an aircraft engine are not completely rigid. Therefore when they are subjected to aerodynamic loading, those structures will deform elastically and their shape will change, especially fan blades because of their size. Those elastic deformations and change in load can, depending on structural and flow characteristics, lead to stability problems and cause an excessive fatigue of the structure decreasing its lifetime or in the worst case, break the structure. Consequently it is necessary to study the engine response to aerodynamic loads to design it to prevent those problems and to simplify the certification.

    A way to do it is to use Computational Fluid Dynamics (CFD) calculations to predict behaviors and better explain phenomena. Today, the trend for turbofans in order to decrease their fuel consumption is to increase their bypass ratio so their fan diameter as well and consequently increase potential elastic deformations, and to shorten the length of the engine air intake to decrease the engine mass but therefore the flow homogeneity also. In these conditions, the crosswind has an increasing impact on turbofan engines because it can create instabilities on the fan blades. Therefore it is important to develop a method to predict the fan behavior under crosswind with a numerical simulation. The present study thus aims to develop a robust and accurate methodology which from a given crosswind speed predicts the displacement of a fan blade to characterize the fan forced response under crosswind.

    Computations will be made on a high-bypass turbofan engine where such phenomena can occur and which was tested. Thus computed results will be compared to test results.

  • 37.
    Guillou, Florian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    CFD Study of the Flow around a High-Speed Train2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This document is a report summering the master thesis work dealing with the Computational Fluid Dynamic (CFD) study of the flow around a high-speed train. The model is a scaled 1:50 generic train with two cars, one inter-car gap and simplified bogies. A platform is set on the side of the train since one of the aim of the study is to look at the consequences of the phenomena in the wake on people or objects standing on the platform. The slipstream is one of this phenomena, it is due to the fact that the viscous air is dragged when the train is passing. If too strong, it can move or destabilize people or objects on the platform.

    In addition of the slipstream study, a velocity profile study, a drag and lift coefficients analyze as well as a Q-factor study and a frequency study have been realized. Some results of these different studies are compared with the ones obtained on the same model with a Delayed Detached Eddy Simulation (DDES).

    Since the flow is turbulent, for those different studies, the flow has been simulated with a Reynolds Averaged Navier-Stokes equation model (RANS) which is the k-ω SST model for the turbulence.

    The study of the slipstream allowed to calculate the Technical Specification for Interoperability (TSI) which must not be higher that the European Union requirement set at 15.5 m/s, the result obtained is 8.1 m/s which is then lower than the limit.

    The velocity profile shows similarities with the DDES results even though it is less detailed. The same conclusion is done for the Q-plot where is clearly visible the two counter-rotating vortices in the wake.

    Finally, a Fast Fourier Transform algorithm has been applied to instantaneous velocity results in the wake of the train in order to get the frequency of the aerodynamic phenomena in that wake. The main frequency is 25 Hz and corresponds to a Strouhal number of 0.1, quite closed to the results obtained with DDES which is 0.085.

    The results of the RANS and DDES are reasonably similar and by regarding at the large difference between the cell numbers (respectively 8 500 000 and 20 000 000) it can be conclude that in some ways the RANS model can be preferred at the DDES to save time for the computation but it does not contain the small scales resolved by the DDES.

  • 38.
    Guter, Nathaniel
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Madorski, Roman
    Chalmers.
    The Vigor Wave Energy Converter: Prototype design and initiation procedures2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Vigor Wave Energy AB is one of several companies on the swedish west coast, focusing their work on developing new ocean energy harvesting devices being able to provide the society with sustainable power sources. Vigor's device was invented by Daniel Ehrnberg and works on the principle of transporting water and air batches through a hose to an enclosed turbine creating an increase in pressure, driving the turbine and thereby creating energy. The work presented in this report describes how a prototype of the device is designed and how to start it up and run it. The minimum underpressure required to initiate the system was found to be of 13 kPa, accelerating the water inside the hose to a desired velocity of 3.5 m/s. The energy generated by this prototype was previously estimated to 3 kW.

  • 39.
    Gómez González, Victor
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Izquierdo Collado, Emilio José
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    The Cormoran project: a new concept in commercial aircraft design2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper presents a new revolutionary design in commercial aircraft: the conven-tional vertical and horizontal tails are not present as generally known, and their contri-bution to the manoeuvering of the aircraft, namely the presence of the rudder and theelevators, is achieved by locating them at the wingtips and in the canard, respectively.Substituting the horizontal tail with the canard, the possibility of dividing the fuel be-tween the wing (where it is located conventionally) and the canard allows the pilot tochange the center of gravity during the ight with more freedom, while the eect of theelevators continues present. Locating the vertical stabilizers at the wingtips combinesthe eect of the vertical stabilizer and the winglet all in one, with the corresponding lostof weight. In this sense, the aerodynamic, stability and aeroelastic characteristics of anaircraft such as the one described have been analyzed using dierent modules belongingto CEASIOM program, and the results are very encouraging, showing that it is reallyfeasible to change the current concept of the commercial aircraft without penalizing theperformance.

  • 40.
    Hammar, Johan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    A Wave Expansion Method for Aeroacoustic Propagation2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Although it is possible to directly solve an entire flow-acoustics problem in one computation, this approach remains prohibitively large in terms of the computational resource required for most practical applications. Aeroacoustic problems are therefore usually split into two parts; one consisting of the source computation and one of the source propagation. Although both these parts entail great challenges on the computational method, in terms of accuracy and efficiency, it is still better than the direct solution alternative. The source usually consists of highly turbulent flows, which for most cases will need to be, at least partly, resolved. Then, acoustic waves generated by these sources often have to be propagated for long distances compared to the wavelength and might be subjected to scattering by solid objects or convective effects by the flow. Numerical methods used solve these problems therefore have to possess low dispersion and dissipation error qualities for the solution to be accurate and resource efficient.

    The wave expansion method (WEM) is an efficient discretization technique, which is used for wave propagation problems. The method uses fundamental solutions to the wave operator in the discretization procedure and will thus produce accurate results at two to three points per wavelength. This thesis presents a method that uses the WEM in an aeroacoustic context. Addressing the propagation of acoustic waves and transfer of sources from flow to acoustic simulations. The proposed computational procedure is applied to a co-rotating vortex pair and a cylinder in cross-flow. Overall, the computed results agree well with analytical solutions.

    Although the WEM is efficient in terms of the spatial discretization, the procedure requires that a Moore-Penrose pseudo-inverse is evaluated at each unique node-neighbour stencil in the grid. This evaluation significantly slows the procedure. In this thesis, a method with a regular grid is explored to speed-up this process.

  • 41.
    Hammar, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Assembly speed-up for the wave expansion method using a uniform background meshManuscript (preprint) (Other academic)
  • 42.
    Houlet, Anne-flore
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Simulations and improvement of ventilation pipes and holds of the Falcon 7X and later with StarCCM+2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 43. Irving, J. P.
    et al.
    Vicroy, D. D.
    Farcy, D.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Development of an aerodynamic simulation model of a generic configuration for S&C analyses2014In: 32nd AIAA Applied Aerodynamics Conference, 2014Conference paper (Refereed)
    Abstract [en]

    The development of an aerodynamic simulation model for the inclusion in an open-loop Stability & Control model is presented. The model, based on a generic UCAV configuration, is derived from data gathered during a number of experimental campaigns conducted using various test models and facilities, and covers the full subsonic flight regime. The model includes uncertainties in key model parameters to yield an expected range of model outputs for any given condition.

  • 44.
    Jiràsek, Adam
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Libm3l and lsipdx-utilities for inter-process data transfer and synchronization2014In: 52nd Aerospace Sciences Meeting, American Institute of Aeronautics and Astronautics, 2014Conference paper (Refereed)
    Abstract [en]

    This paper describes two Open Source Software libraries which are currently under development-libm3l and lsipdx. The libm3l library is a utility enabling storage of the basic data types in a linked list and their transfer through the TCP/IP socket. The linked list can be transferred as a whole or just its part. The second utility, the lsipdx library, is a utility which enables transfer of the data among a number of processes and their synchronization. The libraries are therefore suitable candidate for data exchange and synchronization of a number of solvers in the multidisciplinary analysis. Both libraries are written in the ANSI-C programming language and are available to the public under GNU Lesser GPL, LGPL, license through the github site.

  • 45.
    Johansson, Christopher
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Optimization of wall parameters using CFD2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Computational Fluid Dynamics (CFD) is commonly used to calculate the pressure drop

    in systems with internal ow. To get accurate results the physics of the ow must be well

    dened together with the right material parameters of the considered geometry. The mate-

    rial parameter considered in this report is the wall roughness, or sand-grain roughness, and

    during the thesis work it has been investigated how dierent wall roughnesses aects the

    pressure drop. It has also been investigated how to set up a CFD simulation to accurately

    calculate the pressure drop. When setting up a simulation, a good mesh is essential to get

    accurate results, while using a turbulence model and wall function that is correct for the

    geometry and physics involved. Pressure drop measurements and the corresponding CAD

    geometries were available at the start of the thesis work. The simulations were adapted to

    these to nd the sand-grain roughness for the dierent materials. The main conclusions

    is that the pressure drop can be accurately calculated when the sand-grain roughness is

    known and the CFD simulation is well dened. It was found from the mesh sensitivity

    study that it is essential that the rst cell size is at least twice the size of the sand-grain

    roughness and that at least two cell layers are used to resolve the turbulent boundary layer.

  • 46.
    Kenny, Hedlund
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Wing-, cube- and aeroelastic simulations inUnicorn2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 47.
    Lejeune, Sébastien
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    AIR QUALITY STUDY OF THE PUNARUU TERMAL POWER PLANT, TAHITI AND RENWABLE ENERGIES SUPERVISION2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Tahitian company ‘Electricité de Tahiti’operates two out of eight power groups named G7P and G8P equipped with SCR units to limit the pollution of these groups.The real impact of these units is to be assessed. By using an atmospheric dispersion model called AERMOD,it is shown that the results are very similar with and without the SCR units, as the heights of the chimneys and the wind profile of the valley induce a good dispersion of the fumes for these two groups.

  • 48.
    Martignac, Patrick
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Management of the risks linked to the trial installation of new insulation blankets for single-aisle aircraft2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this diploma thesis is to perform a complete risk assessment of an insulation blanket’s trial installation for an Airbus A320 aircraft. Technical and functional requirements have been described in order to understand the changes operated on the blanket. Through the study of non-conformities and graphs depicting deliverables versus time, quality issues and time delays are tracked in the best possible way in order to identify risks. Appropriate risk tables and matrix were chosen as a frame for this assessment. Risks associated with the trial installation of the new insulation blankets were then assessed, prioritized according to their criticality and placed automatically on a risk matrix using a VBA program. Mitigationactions were finally proposed and validated to achieve the main objective of this risk assessment: to annul the occurrence and to decline the impact of all potential unforeseen turns of event described in this report.

  • 49.
    Mata Bueso, Enrique
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Unsteady Aerodynamic Vortex Lattice of Moving Aircraft2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is aim of this thesis to develop a potential ow solver for unsteady aerodynamics in MATLAB environment. In order to achieve this target a vortex lattice method based has been developed. The validation of this program involves two dierent stages. Initially, it is compared with classical experiments and a well tested code. In a second step, the program is compared with wind tunnel experiments for two dierent aircraft's con gurations, classical and with canard. In the end it will be demonstrated that the present method achieves good agreement in both stages.

  • 50. Mendenhall, M.R.
    et al.
    Perkins, S.C.
    Tomac, Maximilian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Nangia, Raj K.
    Nangia Aero Research Associates.
    Comparing and benchmarking engineering methods for the prediction of X-31 aerodynamics2012In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 20, no 1, p. 12-20Article in journal (Refereed)
    Abstract [en]

    A number of useful engineering methods are available for fast and economic estimates of the aerodynamic characteristics of complex flight vehicles. This article investigates the application of three specific engineering methods to the X-31 fighter configuration, and CFD, wind tunnel, and flight test data are used for comparison and evaluation purposes. The emphasis is on static longitudinal stability aspects up to high angles of attack; however, selected asymmetric and unsteady effects are considered. Results from the engineering methods are in good agreement with experiment and CFD for angles of attack up to 15° for most cases and higher angles for some cases. Results for pitching moment are in good agreement with CFD, but many of the nonlinear characteristics of the airplane are not predicted by the engineering methods. The quality of the longitudinal stability results is discussed in terms of the prediction of the center of pressure on the vehicle. The results provide improved understanding of the continued usefulness of engineering methods as an analysis tool during the design phase and into the flight test diagnostic phase of a new aircraft.

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