AbstractVortex breakdown is of primary importance in many situations met in aeronautical as well as extra-aeronautical applications. During the past 40 years, this problem has been the subject of a large number of investigations, both in the experimental and theoretical domains. This article presents an overview of some of the results obtained by these studies. Carefully executed visualizations and velocity measurements have allowed a clear description of the field associated with breakdown. These experiments executed in a vortex tube, where the vortex is confined, or in arrangements where it is free, show that the existence of a stagnation point forming on the centre-line of the vortical structure is a distinctive feature of breakdown. Different types of breakdown (spiral and bubble types) seem to exist, however this point is subject to controversy. At the same time, the vortex undergoes a brutal dilatation with the generation of large scale fluctuations. Similar features are observed when the breakdown occurs over a delta wing. The two main parameters influencing the phenomenon are the adverse pressure gradient to which the vortex is submitted and its swirl intensity which cannot go beyond a critical value. The most popular theories for vortex breakdown belong to four main classes: the quasi-cylindrical approach and analogy to boundary layer separation, solution of the axisymmetric Navier-Stokes equations, the concept of the critical state and hydrodynamic instabilities. More advanced models, based on the bifurcation theory or using a direct numerical simulation of the problem have also been developed. In most cases, the obtained results are in good agreement with experimental observations, but the predictive capability of these theories is still limited.


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    Title :

    Aspects of vortex breakdown


    Contributors:

    Publication date :

    1993-04-24


    Size :

    59 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English



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