This paper has presented a brief account of the development of the trapped vortex concept through which the major benefits are demonstrated. By considering road cars, racing cars, tractor trailer trucks and high speed trains, it is shown that ground vehicles present favourable platforms for the application of trapped vortices to improve their performance, in terms of reduction of pressure drag and flow unsteadiness, increased downforce, control of hysteresis, crosswind stability, reduction of unsteady loads, and alleviating slipstream effects. Whenever large scale flow separation occurs from the surfaces of ground vehicles, actively controlled trapped vortices can improve aerodynamic performance. However, given the variety of flow scenarios with ground vehicles and their different purposes, trapped vortices alone cannot solve all aerodynamic problems. The technique can be used in conjunction with other methods such as back face suction and blowing, shape optimisation, and vortex generators. There will be a need to compare, at least qualitatively, the effectiveness of trapped vortices with existing means of aerodynamic flow control on ground vehicles. In order to energise and sustain trapped vortices, the opportunity to use exhaust engine flows should be explored. Only specific areas around a ground vehicle, e.g. excluding upper body surfaces, can be targeted for implementation of trapped vortices, One advantage of actively controlled trapped vortices is their minimum effect on the design of the vehicle, especially when implemented underneath the body. Because active flow control (e.g. unsteady suction) and flows around ground vehicles are both unsteady, there is a need to use unsteady techniques (e.g. URANS, LES, PANS, or DES) with trapped vortex flows. Since trapped vortices reduce vortex shedding and unsteadiness, this presents opportunities for researching the aero acoustics of high lift aerofoils with vortex trapping capabilities. For high speed trains, implementing the concept to reduce the effects of strong pressure pulses at tunnel exits could be explored. The role of quick and robust shape optimisation methods, such as the adjoint methods, would be vital in exploring optimum cavity profiles that achieve stabilisation with minimum energy. There remain open questions on the type of flow conditions under which the trapped vortex is beneficial depending on the geometry, vortex size, vortex strength, and stability with respect to large scale vortex shedding. A serious consideration for system identification techniques based on trapped vortices should be investigated. Implementation of trapped vortices should begin with simplified geometries to allow quick assessment of the concept. It would be important to accurately simulate a moving ground with an atmospheric boundary layer (ABL) as this latter is known to become skewed in crosswinds. The ability to visualise the flow for control of trapped vortices e.g. using the elevated ground method, would be important. Whatever the application of trapped vortices is, the issue of vortex stabilisation remains central to the successful implementation of the concept on ground vehicles.


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    Titel :

    On the applicability of trapped vortices to ground vehicles


    Beteiligte:
    Bouferrouk, A. (Autor:in)


    Erscheinungsdatum :

    2014


    Format / Umfang :

    11 Seiten, Bilder, Tabellen, 29 Quellen




    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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