06 Fakultät Luft- und Raumfahrttechnik und Geodäsie

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7

Browse

Start date: 2020Author: search.filters.author.Lutz, ThorstenAuthor: search.filters.author.Krämer, EwaldInstitute: search.filters.UBSInstitut.Fakultätsübergreifend / Sonstige Einrichtung

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Reynolds number and wind tunnel wall effects on the flow field around a generic UHBR engine high-lift configuration
    (2020) Ullah, Junaid; Prachař, Aleš; Šmíd, Miroslav; Seifert, Avraham; Soudakov, Vitaly; Lutz, Thorsten; Krämer, Ewald
    RANS simulations of a generic ultra-high bypass ratio engine high-lift configuration were conducted in three different environments. The purpose of this study is to assess small scale tests in an atmospheric closed test section wind tunnel regarding transferability to large scale tests in an open-jet wind tunnel. Special emphasis was placed on the flow field in the separation prone region downstream from the extended slat cut-out. Validation with wind tunnel test data shows an adequate agreement with CFD results. The cross-comparison of the three sets of simulations allowed to identify the effects of the Reynolds number and the wind tunnel walls on the flow field separately. The simulations reveal significant blockage effects and corner flow separation induced by the test section walls. By comparison, the Reynolds number effects are negligible. A decrease of the incidence angle for the small scale model allows to successfully reproduce the flow field of the large scale model despite severe wind tunnel wall effects.
  • Thumbnail Image
    ItemOpen Access
    Assessment of low‐frequency aeroacoustic emissions of a wind turbine under rapidly changing wind conditions based on an aero‐servo‐elastic CFD simulation
    (2023) Wenz, Florian; Maas, Oliver; Arnold, Matthias; Lutz, Thorsten; Krämer, Ewald
    A meteorologically challenging situation that represents a demanding control task (rotational speed, pitch and yaw) for a wind turbine is presented and its implementation in a simulation is described. A high-fidelity numerical process chain, consisting of the computational fluid dynamics (CFD) solver FLOWer, the multi-body system (MBS) software SIMPACK and the Ffowcs Williams-Hawkings code ACCO, is used. With it, the aerodynamic, servoelastic and aeroacoustic (<20 Hz) behaviour of a generic wind turbine during a meteorological event with strong and rapid changes in wind speed and direction is investigated. A precursor simulation with the meteorological model system PALM is deployed to generate realistic inflow data. The simulated strong controller response of the wind turbine and the resulting aeroelastic behaviour are analysed. Finally, the low-frequency sound emissions are evaluated and the influence of the different operating and flow parameters during the variable inflow is assessed. It is observed that the wind speed and, linked to it, the rotational speed as well as the turbulence intensity are the main influencing factors for the emitted low-frequency sound power of the wind turbine. Yawed inflow, on the other hand, has little effect unless it changes the operational mode to load reduction, resulting in a swap of the main emitter from the blades to the tower.
  • Thumbnail Image
    ItemOpen Access
    Aerodynamic interactions between distributed propellers and the wing of an electric commuter aircraft at cruise conditions
    (2024) Schollenberger, Michael; Kirsch, Bastian; Lutz, Thorsten; Krämer, Ewald; Friedrichs, Jens
    Beneficial interactions that occur between propellers and the wing can be used to increase the overall efficiency of an aircraft in cruise flight. Different concepts with such interacting propellers are distributed propulsion (DP) and wingtip mounted propellers (WTP). For DP, a full distribution over the entire span can be distinguished from a partial distribution, concentrating the propellers at the wing tip area. The paper focuses on the energy efficiency in cruise flight as a result of the interactions and provides a general comparison of the concepts (WTP, full and partial DP) with a Beechcraft 1900D commuter aircraft as a reference. Parametric CFD studies varying the number and the position of the propellers are performed with a half-wing model. The simulations are performed with the second-order finite-volume flow solver TAU, developed by the German Aerospace Center (DLR), employing Reynolds-averaged Navier-Stokes (RANS) equations. The propellers are modeled using an Actuator Disk (ACD). An algorithm is used to reach cruise condition by iteratively adjusting the propeller rotational speed and the wing angle of attack. The CFD results are analyzed and evaluated with respect to the overall efficiency including the aerodynamic efficiency of the wing as well as the propulsive efficiency of the propellers. The parameter study shows that in cruise flight partial DP is more efficient than a full DP. The pure WTP configuration was found as the optimum of the propeller distribution along the wing, resulting in a saving of required power of 5.6%, relative to the reference configuration.