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An aircraft is exposed for a certain risk during warhead deployment. If the distance is too short between the aircraftand warhead during burst, fragments may hit the aircraft with fatal consequences. The warhead consists not onlyof fragments created during burst but also parts to attach it to the aircraft such as mounting plates and fasteningloops. These parts have a significantly larger mass than natural fragments and may travel far during trajectory.The problem for a potential hit of fragment on a fighter jet after its warhead has detonated has been presentsince several decades. It is of interest to analyse the problem to effectively reduce the warheads arming time andthe aircraft’s altitude during warhead deployment. The complexity consists of how the mounting plates and fas-tening loops behave during trajectory, which may affect the travelled distance if they rotate or tumble. Attemptsto solve this problem for the Gripen fighter jet has been made by Staffan Harling at FOI which this thesis is asubsequent work. This thesis treats a risk perspective analyse of the distance between the aircraft and warhead named range safetydistance. Travelled distances for fragments are calculated with variation in velocity, drag coefficient and ejectionangle to analyse the problem to a wider extent. The conclusion states that the time from warhead deployed until it burst should be at least seven seconds. Genericdata has been used in this master thesis due to classified information concerning real cases. Focus has been onthe method and to develop a Matlab code that hopefully can be used to estimate range safety distances from aappropriate risk perspective. Vid bombfällning är ett flygplan särskilt utsatt för risk. Om avståndet mellan flygplan och fälld stridsdel är relativtsett för kort vid bombens brisad, finns risk att splitter träffar flygplanet med potentiella förödande konsekvenser.Stridsdelen består förutom splitter som skapas vid brisad också utav en fästanordning bestående av fästplatta samtlyftögla i dubbel uppsättning. Dessa har en signifikant större massa vilket troligtvis gör att de flyger längre vidutkastning efter bombbrisad. Problemet med vådabekämpning av eget flygplan har kvarstått under flera decennier och utgör en frågeställningintressant att besvara både i övningssyfte och under skarp insats. Syftet är att kunna minimera armeringstidenoch därigenom även flygplanets flyghöjd vid fällning. Komplexiteten utgörs av att lyftöglan och fästplattan har ettsvåranalyserat beteende under sin färdade bana, då de både kan rotera och tumla. Denna avhandling behandlar ett riskperspektiv som analyserar avståndet mellan flygplan och stridsdel. Den färdadesträckan för splitter är beräknat med variation i hastighet, luftmotståndskoefficient samt utkastningsvinklar för attundersöka problemet i ett större perspektiv. Som slutsats erhålls att armeringstiden bör vara sju sekunder. Detta resultat är uteslutande beroende av dengeneriska data som använts då relevant information oftast är hemlig. Fokus har därför legat på att utveckla enmetod med tillhörande Matlabkod som förhoppningsvis kan användas för att beräkna ett säkerhetsavstånd utifrånett lämpligt riskperspektiv.

This study was performed to investigate aerodynamic characteristics of the 37.5% scaled­ down Green Raven MK18 airframe, to evaluate boundary corrections method, and to investigate on support interference. A wind tunnel test was originally planned on June 2021 at a Large­Low­Speed Wind Tunnel at University of Bristol; however, due to COVID­19 travel restrictions, the test has been postponed to November 2021. In or­der to supplement the work and data directly required for the test, computational fluid dynamics (CFD) investigations were performed in free air and in wind tunnel condi­tions, both with and without support interference, at a Reynolds number of 7E+05. The simulations utilized an incompressible Reynolds-­Averaged­-Navier.­Stokes equa­tion accompanied with k − ω SST for turbulent modelling. Corrections factors were obtained to compensate for wall interference, and results indicate a satisfactory agree­ment between free ­air and wind­ tunnel corrected data for wall interference. The sup­ port structure interferes with the aerodynamic loads produced by the model. Lift and drag decrease, and pitching moment increases compared to WT without support structure condition. Denna studie utfördes för att undersöka aerodynamiska egenskaper hos det nedskalade Green Raven MK18­flygplanet för 37.5%, för att utvärdera gränskorrigeringsmetoden och för att undersöka stödinterferens. Ett vindtunneltest planerades ursprungligen i juni 2021 vid en stor­låghastighets vindtunnel vid University of Bristol. Men på grund av resebegränsningar för covid­19 har testet skjutits upp till november 2021. För att komplettera det arbete och de data som direkt krävs för testet, utfördes CFD under­ sökningar (Computational Fluid Dynamics) i fri luft och i vindtunnelförhållanden, både med och utan supportinterferens, med ett Reynolds­tal på 7E+05. Simuleringarna använde en inkompressibel Reynolds­Averaged­Navier­Stokes­ekvation tillsammans med k − ω SST för turbulent modellering. Korrigeringsfaktorer erhölls för att kom­ pensera för väggstörningar, och resultaten tyder på en tillfredsställande överensstäm­ melse mellan frilufts­ och vindtunnelkorrigerade data för väggstörningar. Stödstruk­ turen stör de aerodynamiska belastningar som modellen producerar. Lyft och drag minskar och stigningsmomentet ökar jämfört med WT utan stödstruktur.

The transient incoming flow a compact car experiences whilst driving 10 m – 100 m behind a heavy vehicle on a runway has been characterised. The incoming flow was measured using a 2D array of 11 five-hole probes mounted 1 m in front of an operational, full-scale compact car. Additionally, 188 surface pressure taps were used to measure the effect of the incoming flow conditions on the compact car. The experiments were performed under ideal conditions on a 2.9 km long runway in Fasberg near the DLR in Trauen, Germany.

Aerodynamic interactions of fragments of meteoroids and space debris during atmospheric entry influence the flight trajectories of the fragments and their strewn field on the Earth’s surface as well as the meteoroids’ airburst altitude and energy deposition rate in the atmosphere and thus the resulting ground damage. For the design of experiments in the Hypersonic Wind Tunnel H2K of DLR, German Aerospace Center in Cologne to investigate the interaction phenomena, a method is developed to estimate the forces on two interacting bodies in supersonic and hypersonic flows, which is more accurate than existing analytical and semi-analytical methods and more efficient than numerical simulations regarding the computational effort. It is based on the superposition of flowfields taken from a database of numerical simulations of a single body for a range of Mach numbers. Furthermore, three-dimensional computations of configurations of interacting bodies are carried out by NASA Ames Research Center. Results obtained with the superposition method are compared to the simulations by NASA and to results of computations that can be found in the literature. The results from the method show good agreement with the computations.

Central targets for jet engine research activities comprise the evaluation of improved engine components and the assessment of novel engine concepts for enhanced overall engine performance in order to reduce the fuel consumption and emissions of future aircraft. Since CO2 emissions are directly related to engine fuel burn, a reduction in fuel consumption leads to lower CO2 emissions. Therefore improvements in engine technologies are still significant and a multi-disciplinary pre-design approach is essential in order to address all requirements and constraints associated with different engine concepts. Furthermore, an increase in effectiveness of the preliminary design process helps reduce the immense costs of the overall engine development. Within the DLR project PEGASUS (Preliminary Gas Turbine Assessment and Sizing) a multi-disciplinary pre-design and assessment competence of the DLR regarding aero engines and gas turbines was established. The application of modern preliminary design methods allows for the construction and evaluation of innovative next generation engine concepts. The purpose of this paper is to present the developed multi-disciplinary pre-design process and its application to three aero engine models. First, a state of the art twin spool mixed flow turbofan engine model is created for validation purposes. The second and third engine models investigated comprise future engine concepts: a Counter Rotating Open Rotor and an Ultra High Bypass Turbofan. The turbofan used for validation is based on publicly available reference data from manufacturing and emission certification. At first the identified interfaces and constraints of the entire pre-design process are presented. An important factor of complexity in this highly iterative procedure is the intricate data flow, as well as the extensive amount of data transferred between all involved disciplines and among the different fidelity levels applied within the smoothly connected design phases. To cope with the inherent complexity data modeling techniques have been applied to explicitly determine the required data structures of those complex systems. The resulting data model characterizing the components of a gas turbine and their relationships in the design process is presented in detail. Based on the established data model the entire engine pre-design process is presented. Starting with the definition of a flight mission scenario and the resulting top level engine requirements thermodynamic engine performance models are developed. By means of these thermodynamic models, a detailed engine component pre-design is conducted. The aerodynamic and structural design of the engine components are executed using a stepwise increase in level of detail and are continuously evaluated in the context of the overall engine system.

This paper presents the results of force measurements on a tandem configuration (platoon) of two train models (Type: Next Generation Train) at varying distances in heading direction in the water towing tank at the German Aerospace Center Gottingen (DLR). The trains had no mechanical connection to represent the occurring situation of virtual coupling. The experiments were conducted at a Reynolds number of 240,000 at 4 m/s. A ground plate was used to account for under floor effects. The gap distance was varied between 1.2% and 59.5% of the single train length. In comparison to a single vehicle, drag reductions of up to 30.4% were observed for the trailing vehicle at all distances. For the leading train reduced resistances at distances ≤12% were found. The combined drag of two vehicles is up to 16% less than the resistance of two single trains. With Particle Image Velocimetry (PIV) a strong interaction between both trains is observed at closest distance (1.2%). An area of reduced relative velocity and thus reduced stagnation pressure in front of the second train is found to be the reason for a smaller drag. At wider gaps (35.7% and 47.6%) a beneficial development of vorticity behind the first train is found to be the cause of a reduced drag value on the trailing vehicle.

Over the last decade numerous experimental and numerical studies have been conducted by DLR together with partners regarding the maturation of active flow separation control technologies at low speed high-lift conditions. The DLR-F15 high-lift airfoil has been established as a common test bed for such kind of investigations within the German national framework and in the scope of European Research. The present paper highlights major results of this research regarding flow separation suppression by means of pulsed blowing.

Navier-Stokes calculations on hybrid grids using the TAU software of the MEGAFLOW project are performed to compute engine installation drag for the DLR, German Aerospace Research Center, F6 transport aircraft configuration at cruise flight conditions with conventional and with very-high-bypass-ratio nacelles at three and two different locations, respectively. The results are verified by a comparison with experimental data from different wind-tunnel campaigns carried out with Office National d'Etudes et de Recherches Aerospatiales. Numerical discretization errors are reduced by several steps of grid adaptation, resulting in grid densities up to 8.4 x 10 6 nodes. It is demonstrated that the installation drag of the different configurations, which vary only a few drag counts (10 -4 ), can be computed consistently, although the total drag forces are predicted lower than results of experiments. Successive grid refinement leads to a decrease of the differences between calculated and measured installation drag