Transverse Injection from Circular and Elliptic Nozzles into a Supersonic Crossflow

Abstract

An investigation of sonictransverse injection from circular and elliptic nozzles into a supersoniccrosse ow using planar Rayleigh/Mie scattering is reported. Instantaneous images allow examination of the structural details, whereas ensemble-averaged images provide transverse penetration and lateral spread data for each jet. Standard deviation images produce information regarding the large-scale mixing/entrainment and reveal the mixing zones. Results show a highly three-dimensional near-e eld interaction dominated by shear-layer eddies and a counterrotating vortex pair. Ensemble-averaged results show that the elliptic jet spreads more rapidly in the lateral direction than the circular jet, cone rming that an axis-switching phenomenon is present. Near-e eld transverse penetration data collapse well with low-speed scaling conventions; however, the jet produced by the elliptic nozzle suffersa20%reductioninpenetrationcomparedto thecircularjet.Compressibilityleveldoesnotplaya signie cant roleintheaveragepenetrationorspreadofthesejets,althoughitstronglyaffectsthemixing/entrainmentandlargescale structure. Analysis of mixing potential from the standard deviation images indicates that the low and high convective Mach number Mc injection cases are signie cantly different; low Mc injection yields better large-scale mixing potential than high Mc injection regardless of the injector geometry.