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Effects of a Bell-Shaped Lift Distribution on an Oblique Flying Wing and its Impact on Aerodynamic PerformanceDeslich, Joshua 22 June 2020 (has links)
No description available.
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Aerodynamic optimization of Formula Student wishbonesWallberg, Felix January 2024 (has links)
This thesis investigates an aerodynamic optimization of front lower wishbones on a FormulaStudent car using CFD simulations and windtunnel testing. The aim of the study is to de-termine weather a geometric optimization of wishbones is feasable and could enhance theaerodynamic performance of the vehicle.Siemens Star-CCM+ is utilized for the CFD simulations with focus on iterative design im-provments to optimize the initial generic airfoil shape. The CFD model is based on the modelprovided by KTH Formula Student. The model was also developed further in the initial stagesof the study. Turbulance transition model was investigated as well as the turbulance model toaccurately capture the near wall flow dynamics.In order to validate the results from the CFD model a set of windtunnel tests where doneinvolving a 13 scale model of the vehicle at various yaw angles.Some key findings from the analysis indicate that significant changes in the aerodynamicalcharacteristics can be made by making relatively small changes to the geometry of the vehicle.An increase of 2,1% was achieved which closely correlate to the accuired data which indic-ated a 2,2% increase.The optimization process highlighted the importance of developing CFD optimization tech-niques as they can make large contributions to the aerodynamic characteristics of vehicles.This can be used in order to increase the performance of of vehicles in motorsport or reducedrag in everyday vehicles to reduce the energy consumtion.
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Modélisation des fluctuations de la pression pariétale d'une couche limite turbulente pour des applications en vibro-acoustique / Modeling of the wall pressure fluctuations of a turbulent boundary layer for vibro-acoustic applicationsMorilhat, Sylvain 14 December 2018 (has links)
Une couche limite turbulente se développant le long d’une paroi présente des fluctuationsde vitesses et de pression importantes. Si la paroi du profil est suffisammentsouple, les fluctuations de pression pariétale peuvent la faire rentrer en vibration cequi induit un rayonnement acoustique de chaque côté de la paroi. Ce scenario estl’un des mécanismes de génération de bruit interne dans les aéronefs. Le but de cettethèse est de proposer un modèle de reconstruction des fluctuations de pression pariétaleafin de prévoir in fine le bruit rayonné. Plutôt que de reposer sur une approchesemi-empirique, les modèles développés dans cette thèse se basent sur la résolutionanalytique de l’équation de Poisson liant les fluctuations de pression aux fluctuationsde vitesses. Ces dernières sont modélisées par exemple à l’aide des profils moyensde la couche limite obtenus grâce à un calcul RANS. La résolution de l’équation dePoisson dans ce contexte a déjà été entreprise en particulier par Lysak et Aupoixet leurs travaux sont le point de départ de cette thèse. Cependant, leur modèle nedonne qu’une description temporelle des fluctuations de pression pariétale alors queles aspects spatiaux sont nécessaires pour une application vibro-acoustique. L’apportde cette thèse consiste donc en une modification de leur modèle afin de palliercette difficulté. En parallèle de ces travaux de modélisation, une expérience de validationen soufflerie a été élaborée et mise en place. Les fluctuations de vitesses ontété mesurées par vélocimétrie laser tandis que les fluctuations de pression pariétaleont été mesurées à l’aide de micro-tiges mobiles. Le modèle initialement développéà été affiné à l’aide de ces mesures. En particulier, une description anisotrope desfluctuations de vitesses a été développée, ce qui est plus cohérent pour un écoulementcisaillé que la description homogène isotrope utilisée jusqu’alors. Les modèlesdéveloppés ont un large recoupement avec le modèle semi-empirique de Corcos quiest la référence utilisée pour les applications en vibro-acoustique. Cependant, desdifférences comportementales importantes aux hautes et basses fréquences ont étémises en évidence. Le modèle de Corcos peut donc être remis en question pour cesplages fréquentielles. Ces résultats théoriques doivent néanmoins être confortés pardes mesures. / Large pressure and velocity fluctuations are present inside a turbulent boundarylayer developing along a wall. A non-rigid wall can be excited by the wall pressurefluctuations and thus acoustic radiations will be emitted above and bellow the wall.This scenario is one the mechanism of intern noise generation inside aircraft. Theaim of this thesis is to elaborate a turbulent wall pressure fluctuations model inorder to compute the noise radiated by the vibrating wall at the end. Modelsdeveloped during this thesis do not rely on an semi-empirical approach as they arebased on the analytical resolution of Poisson’s equation relating pressure and velocityfluctuations. This kind of approach has already been used by Lysak and Aupoix andtheir work was the starting point of this thesis. However, their model only gives atemporal description of the wall pressure fluctuations while a temporal and spatialdescription is needed for vibro-acoustics application. The major contribution of thisthesis is to modify their model in order to overcome this incapacity. In parallelto this theoretical modelling, a wind-tunnel experimental campaign dedicated tovalidation was designed and implemented. Velocity fluctuations were measured usingLaser Doppler Velocimetry while wall pressure fluctuations were measured usingmobile wall-mounted microphones. The initial model was improved using thesemeasurements. In particular, an anisotropic description of the velocity fluctuationswas developed which is more consistent for a sheared flow than the homogeneous andisotropic description used by Lysak and Aupoix. For a large frequency range, thefinal model behaves similarly to Corcos’ model which is the most used reference forvibro-acoustics applications. However, large differences were highlighted for low andhigh frequencies. Therefore the validity of Corcos’ model is questionable for thesefrequency range. These theoretical results must still be confirmed by experimentaldata.
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Produktutveckling av lättviktsvindskydd : En jämförelsestudie inriktad på Trangias stormkökAirikka, Marcus January 2023 (has links)
Trangia är ett varumärke som har utvecklat stormkök sen år 1925. I dagens portfolio har de inga alternativ för lättviktsvandrare, däremot utvecklar de ett nytt kärl idag som skall passa denna målgrupp. Syftet med rapporten är att ta reda på hur ett nytt vindskydd kan se ut till detta kärl och utveckla ett slutkoncept. Detta har gjorts genom att göra en undersökning på Trangia 27–1 UL, Optimus Elektra FE och ett fristående vindskydd i aluminiumfolie. Det har tagits fram prototyper vars effektivitet har testats i en vindtunnel både utan vind och med vind (5–6 m/s). För att kunna utföra dessa tester konstruerades det en vindtunnel för projektet. För att bevara Trangias designspråk har det även utförts semistrukturerade intervjuer mot Trangias personal. Slutkonceptet togs fram genom att följa en traditionell produktutvecklingsprocess. Resultatet visar på att Trangia 27–1 UL var det effektivaste köket av de testade. I vindtunneltestet hade stormkökets koktid ökat med 9,83% med kontra utan vind. Den semistrukturerade intervjun visade på att Trangias produkters designspråk ansågs vara mjuka, robusta och simpla. För att kunna utföra dessa tester konstruerades det en vindtunnel för projektet Slutsatsen i rapporten visar på att ett cylindriskt vindskydd med en tillräckligt stor ventilation är effektivast under vindbelastning. Den bör kunna packas ned och vara simpel att montera upp. För att bevara Trangias designuttryck bör vindskyddet ha mjuka kanter och kännas tålig. Det behövs däremot utföras ytterligare studier för att kunna göra noggrannare analyser på vindskyddet / Trangia is a brand that has been developing camping stoves since year 1925. In today's portfolio, they have no options for lightweight hikers, however, they are developing a new concept that they believe will suit this target group. The purpose of this report is to find out how a new windshield can look like for Trangias new product and develop a final concept. This has been done by examining the existing products: Trangia 27–1 UL, Optimus Elektra FE and a stand-alone aluminium foil windshield. Prototypes have been developed whose effectiveness have been tested in a wind tunnel, both without and with wind (5–6 m/s).A wind tunnel was constructed for the project in order to carry out these tests. To preserve Trangia's current design, semi-structured interviews have also been performed towards Trangia's staff. The final concept was developed by following a traditional product development.The result shows that the Trangia 27–1 UL was the most efficient kitchen of those tested. In the wind tunnel test, the cooking time of this camping stove had increased by 9.83% with wind, compared to without. The semi-structured interview showed that the design of Trangia's products was soft, robust, and simple.In conclusion, the report shows that a cylindrical wind shield with a sufficiently large ventilation is most efficient during wind load. The product should be able to be packed down and be simple to assemble. On the other hand, further studies are needed to be able to make thorough analyses of the wind shelter. / <p>2023-06-07</p>
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Effects of Bt transgenes on herbivorous insect-parasitoid interactions / Einfluss der transgenen Bt-Pflanzen auf Herbivor-Parasitoid-InteraktionenSteinbrecher, Isolde 16 July 2004 (has links)
No description available.
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