AbstractA numerical study is conducted to investigate the effects of the inflow Knudsen number (Kn) on hypersonic chemical nonequilibrium rarefied flows using the unstructured direct simulation Monte-Carlo (DSMC) method, and an empirical formula for fast prediction of flow-field structure for different values of Kn is proposed and verified. First, the flow around a vertical plate is analyzed at a free-stream velocity of 7,500  m/s using a perfect-gas model with inflow Kn values ranging from 0.035 to 13.36. Through analysis of the flow-field characteristics with varying Kn values, a linear expansion law of flow-field versus the square root of Kn is discovered and an empirical formula based on least-squares fitting is developed for fast prediction of the flow structure at different values of Kn. Further, the effects of chemical nonequilibrium on hypersonic rarefied flow-field structure are investigated to verify the applicability of the empirical formula. Finally, cases of the cylinder flow are simulated in the regimes from continuum flow to free-molecular flow using a five-species chemical reaction model. The flow-field characteristics with varying Kn values, with the chemical nonequilibrium model, agrees well with those for perfect-gas conditions. It is shown that the empirical formula is also suitable for the use of flow with chemical reactions. The shock position in a continuum-flow case predicted by the empirical method agrees well with data from the literature. The applicability and accuracy of this method over a wide range of Kn have been verified.


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    Titel :

    Prediction of Chemical Nonequilibrium Flow Structure at Different Free-Stream Knudsen Numbers


    Beteiligte:

    Erschienen in:

    Erscheinungsdatum :

    2016




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch



    Klassifikation :

    BKL:    55.50 Luftfahrzeugtechnik / 51.40 Werkstoffe für bestimmte Anwendungsgebiete / 55.60 Raumfahrttechnik
    Lokalklassifikation TIB:    770/7040