MIXING CHARACTERISTICS OF COMPRESSIBLE VORTEX RINGS INTERACTING WITH NORMAL SHOCK-WAVES

The instability mechanisms and mixing enhancement arising from the int eraction of a compressible vortex ring with a normal shock wave were s tudied in a colinear, dual-shock tube. This flow geometry simulates fe atures of the interaction of a shock wave with a jet containing stream wise vorticity, a configuration of significant interest for supersonic combustion applications. Flow visualization and quantitative concentr ation measurements were performed by planar laser Rayleigh scattering. For a given primary shock strength, interfacial instability is more e vident in a weak vortex ring than in a stronger vortex ring. In all ca ses, the identity of the vortex ring is lost after a sufficiently long time of interaction. The probability density function of the mixed fl uid changes rapidly from a bimodal distribution to a single peak upon processing by a shock wave. The most probable concentration decreases with time, indicating a rapid increase in mixing and dilution of the v ortex fluid. The mixing enhancement is most rapid for the case of a st rong vortex ring interacting with a strong shock wave, somewhat slower for a weak vortex ring and a strong shock wave, and significantly slo wer for the case of a strong vortex ring and a weaker shock wave. Thes e observations are consistent with the earlier numerical predictions.