06 Fakultät Luft- und Raumfahrttechnik und Geodäsie

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

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

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Now showing 1 - 3 of 3
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    Aerodynamic and acoustic simulations of thick flatback airfoils employing high order DES methods
    (2022) Bangga, Galih; Seel, Ferdinand; Lutz, Thorsten; Kühn, Timo
    The results of high fidelity aerodynamic and acoustic computations of thick flatback airfoils are reported in the present paper. The studies are conducted on a flatback airfoil having a relative thickness of 30% with the blunt trailing edge thickness of 10% relative to chord. Delayed Detached-Eddy Simulation (DDES) approaches in combination with high order (5th) flux discretization WENO (Weighted Essentially Non-Oscillatory) and Riemann solver are employed. Two variants of the DES length scale calculation methods are compared. The results are validated against experimental data with good accuracy. The studies provide guideline on the mesh and turbulence modeling selection for flatback airfoil simulations. The results indicate that the wake breakdown is strongly influenced by the spanwise resolution of the mesh, which directly contributes to the prediction accuracy especially for drag force and noise emission. The Reynolds normal stress and the Reynolds stress component have the largest contributions on the mixing process, while the contribution of the component is minimal. Proper orthogonal decomposition is further performed to gain deeper insights into the wake characteristics.
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    Utilizing high fidelity data into engineering model calculations for accurate wind turbine performance and load assessments under design load cases
    (2022) Bangga, Galih; Parkinson, Steven; Lutz, Thorsten
    Wind turbines often have lower performance and experience higher loading in real operation compared to the original design performance. The reasons stem from the influences of complex atmospheric turbulence, blade contamination, surface imperfection and airfoil-shape changes. Engineering models used for designing wind turbines are limited to information derived from blade sectional datasets, while details on the three-dimensional blade characteristics are not captured. In these studies, a dedicated strategy to improve the prediction accuracy of engineering model calculations will be presented. The main aim is to present an elaborated effort to obtain a better estimate of the turbine loads in realistic operating conditions. The present studies are carried out by carefully utilizing data from high fidelity Computational Fluid Dynamics (CFD) computations into Blade Element Momentum (BEM) and Vortexline methods. The results are in a good agreement with detailed field measurement data of a 2.3 MW turbine. The studies are further extended to a large turbine having a rated power of 10 MW to provide an overview of its suitability for large turbines. Finally, calculations of the wind turbine under a realistic IEC design load case are demonstrated. The studies highlight important considerations for engineering modeling using BEM and Vortexline methods.
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    An improved second-order dynamic stall model for wind turbine airfoils
    (2020) Bangga, Galih; Lutz, Thorsten; Arnold, Matthias
    Robust and accurate dynamic stall modeling remains one of the most difficult tasks in wind turbine load calculations despite its long research effort in the past. In the present paper, a new second-order dynamic stall model is developed with the main aim to model the higher harmonics of the vortex shedding while retaining its robustness for various flow conditions and airfoils. Comprehensive investigations and tests are performed at various flow conditions. The occurring physical characteristics for each case are discussed and evaluated in the present studies. The improved model is also tested on four different airfoils with different relative thicknesses.The validation against measurement data demonstrates that the improved model is able to reproduce the dynamic polar accurately without airfoil-specific parameter calibration for each investigated flow condition and airfoil.This can deliver further benefits to industrial applications where experimental/reference data for calibrating the model are not always available.