A numerical study is conducted to investigate the effects of the inflow Knudsen number ( K n ) 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 K n 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 K n values ranging from 0.035 to 13.36. Through analysis of the flow-field characteristics with varying K n values, a linear expansion law of flow-field versus the square root of K n is discovered and an empirical formula based on least-squares fitting is developed for fast prediction of the flow structure at different values of K n . 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 K n 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 K n have been verified.


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    Title :

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


    Contributors:
    He, Tao (author) / Wang, Jiang-Feng (author)

    Published in:

    Publication date :

    2016-05-06




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    Unknown