Aiaa-2004-0919 Mean Flow of Multistream Rectangular Jets under Normal and Mixing Enhancement Conditions

Flow exiting a convergent-divergent nozzle operated at o -design conditions exhibits an instability that causes mixing enhancement in the ow itself and can destabilize an adjacent ow. The latter property enables mixing enhancement of an arbitrary jet via parallel injection of a secondary gas ow. In this study we investigated the e ect of mixing enhancement using secondary parallel injection (MESPI) on the mean ow eld of rectangular (2D) jets. The mean velocity eld was surveyed using an array of Pitot probes. The primary jet was supersonic and the secondary (co ow) jets were high-subsonic. Comparisons were made between MESPI and normal jets for a variety of nozzle arrangements. The most promising con guration utilized co ow on one side only of the primary jet. The bypass ratio was 0.24 and the estimated thrust loss was around 1%. The potential core length was reduced by 60% and the volume ow rate in the mideld of the jet increased by about 30%. The cross section of the jet evolved rapidly from rectangular to elliptical with axisswitching. Correlation of the mixing rates of all the jets shows that mixing enhancement is sensitive to the area ratio of the secondary nozzle and the recession of the secondary nozzle relative to the primary nozzle. The bypass ratio appears to play minor role.