Session Hj - Shocks, Combustion & Hypersonic Flows.
ORAL session, Tuesday, November 25
310, Moscone Center
The changes in the structure and mixing of a turbulent jet due to the passage of a normal shock wave were examined experimentally. An axisymmetric jet (1.1 mm i.d.) of pure air, helium, or carbon dioxide was centered along the axis of an air shock tube 5 x 5 cm square in cross section. The shock propagation was in the same direction as the jet flow. Planar Mie scattering imaging using pulsed laser illumination was performed over a downstream distance of roughly 60 jet diameters by seeding the jet with mineral oil smoke. For the air jet, there was little change in the spatial probability density function (pdf) of the mixed fluid, indicating little increase in mixing due to the shock/jet interaction. For the helium jet, there was a distinct shift in the pdf towards lower concentrations (more mixing) with shock passage. The images for the helium jet with shock interaction also showed a marked change in turbulent structure, leading to large-scale vortical structure not apparent for the case of the air jet. The carbon dioxide jet exhibited less mixing enhancement than the helium jet, and no marked changes in structure compared with the air jet.