In the current work, important findings affecting the practical implementation of the DES (Detached-Eddy Simulation)-technique have emerged. Firstly, it has been shown that, contrary to expectation, a sensitivity to the choice of background model exists in DES, and that the level of this sensitivity is higher for coarser grid resolutions. A feasible mechanism, based on the occurrence of RANS-mode zones outside of the attached boundary layer, has been proposed as an explanation for this. The evidence so-far accumulated does not however suggest that more elaborate RANS models make better DES background models. A second finding of the presented work is that the level to which the grid outside the boundary layer satisfies the requirements of LES (Large Eddy Simulation) resolution is of a lesser importance. From consideration of the results of the initial three O-grids (c, m and f), it might appear as if grid refinement delivers higher quality results in DES. Unfortunately, from the present study it is not possible to say whether further refinement would result in an over-prediction of the force coefficients. This is because the vf grid has an entirely different topology and fineness distribution, and as such does not constitute the next step in a systematic grid refinement study. It has been shown that the solution is highly sensitive to the fineness distribution, a finding which corresponds with experience from LES. In order to establish whether the over-prediction of the force coefficients is due to the grid refinement in itself, or rather due its uneven distribution (or a mixture of the two), a new grid has been constructed This takes as its basis the f grid topology and distribution, whereby the number of points is doubled in each index direction. Calculations on this grid are underway.


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    Title :

    Turbulence modelling in application to the vortex shedding of stalled airfoils


    Additional title:

    Turbulenzmodellierung in Anwendung auf die Wirbelablösung an überzogenen Tragflügeln


    Contributors:
    Mockett, C. (author) / Bunge, U. (author) / Thiele, F. (author)


    Publication date :

    2005


    Size :

    10 Seiten, 7 Bilder, 2 Tabellen, 14 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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