Mixing of Transverse Jets and Wall Jets in Supersonic Flow

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A critical review of the available high speed mixing experimental database is presented. Experiments of concern involve measurements of species concentration downstream of sonic or supersonic injection of a light gas into a supersonic air stream. Several classes of injection are considered including transverse jets, wall slots, and some hybrid cases. The review is made difficult by the sparseness of the current database. Mixing data is summarized primarily in the form of the downstream decay of the maximum concentration. Most of the data in the far field can be fitted to a. power law curve with the exponent giving an indication of the rate of mixing. The resulting plot of the experiments presented provides a basis for preliminary comparison of high speed injection concepts. Spacing of jets below a critical value can reduce the rate of mixing by a factor ot two. Initial mixing for transverse jets is strongly dependent on the dynamic pressure ratio. The farfield mixing rate for wall slot injectors is found to be comparable to that for arrays of transverse jets, not slow as has been believed. As a crude estimate, it is shown that all the data for all the configurations falls into a band with a decay rate of about.T0,8. The need for more high quality experiments for high speed mixing in support of such difficult problems as supersonic combustion is apparent. The need for careful sampling probe design is emphasized. Finally, the state of analyses for these flows is discussed. A new analysis for arrays of transverse jets is presented.