07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/8

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Publication Type: search.filters.UBSTyp.ZeitschriftenartikelAuthor: search.filters.author.Stoll, Daniel

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    Aerodynamics of high-speed trains with respect to ground simulation
    (2022) Weidner, Dennis; Stoll, Daniel; Kuthada, Timo; Wagner, Andreas
    Wind tunnel testing is commonly used to assess and optimize the aerodynamic characteristics of high-speed trains. The train model is usually mounted above a static ground plane, but a moving ground is necessary for the correct representation of the relative motion between train and ground. This study focuses on the effect of the applied ground simulation on the aerodynamics of a high-speed train. Wind tunnel tests using a stationary and a moving ground were carried out using a 1:20 scale model of a high-speed train’s first car. Numerical simulations for two moving ground configurations are created, and the simulation setup is validated using surface pressure measurements from the wind tunnel tests. It is shown that the ground simulation has a significant effect on the drag in the considered yaw angle range. Additionally, the change in drag due to bogie fairings is evaluated and an impact of the applied ground simulation on the drag reduction is observed. The drag reduction of front and rear bogie fairings is valued similarly using a static ground, however on a moving ground the drag reduction of front bogie fairings is significantly increased. Good agreement between simulations and experiments is achieved.
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    Experimental and numerical investigation of the aerodynamic ventilation drag of heavy-duty vehicle wheels
    (2023) Peiró Frasquet, Carlos; Stoll, Daniel; Kuthada, Timo; Wagner, Andreas
    Due to current EU regulations, constant-speed testing on test tracks is used for aerodynamic certification of heavy-duty vehicles (HDV). However, the aerodynamic development of HDVs is performed using wind tunnels and computational fluid dynamics (CFD). Both techniques commonly neglect the rotational aerodynamic losses of the wheels-the so-called ventilation drag-that are present when driving on the road. This is due to the fact that there is no full-scale wind tunnel for this type of vehicle with a suitable belt system for the simulation of the wheel rotation. Furthermore, the ventilation drag of HDV wheels has been neglected in CFD due to their almost completely closed rim design. These constraints lead to an underprediction of the aerodynamic forces in comparison to the results under on-road conditions when performing constant-speed tests. In order to investigate the ventilation drag of HDV wheels, measurements were carried out on a 1:4.5 scale generic tractor-trailer model in the Model Scale Wind Tunnel of the University of Stuttgart. The measured aerodynamic forces as well as the measured flow field data provide the basis for the definition and validation of a procedure for analyzing the ventilation drag in CFD. Accordingly, the ventilation drag of a full scale HDV was investigated in CFD. The results show that the tire treading and rim geometry have a significant influence on ventilation drag that contributes to the total aerodynamic drag of the HDV. The present work shows that the ventilation drag has a relevant impact on the total aerodynamic drag of HDVs and should therefore not be neglected. The presented CFD approach thus allows to assess the aerodynamic drag under real on-road conditions in an early stage of the vehicle development.