Effects of Sinusoidal Excitation on Transverse Jet Dynamics, Structure, and Mixing

• Published in: AIAA journal 2020-09, Vol.58 (9), p.3889-3901
• Main Authors: Shoji, Takeshi, Harris, Elijah W, Besnard, Andrea, Karagozian, Ann R
• Format: Article
• Language: English
• Subjects: Acetone; Cross flow; Cross-sections; Dynamic structural analysis; Excitation; Fluid dynamics; Fluid flow; Molecular structure; Planar laser induced fluorescence; Reynolds number; Shear layers
• ISSN: 0001-1452; 1533-385X
• DOI: 10.2514/1.J059295

This experimental study explored the effects of axisymmetric sinusoidal excitation on structural and mixing characteristics in the equidensity jet in crossflow (JICF). Planar laser-induced fluorescence imaging of acetone seeded in the jet fluid was used in this quantification, where the jet Reynolds number was fixed at Rej=2300 and crossflow velocity was varied. Jet-to-crossflow momentum-flux ratios J ranged from J=61, with a convectively unstable upstream shear layer (USL) in the absence of forcing, to J=7, with a globally unstable USL. Sinusoidal excitation had a relatively significant influence on the convectively unstable JICF at larger J values, especially when the USL was locked-in to the forcing frequency, causing the jet cross section to become more symmetric and causing molecular mixing, quantified in both centerplane and cross-sectional planes, to improve. For a globally unstable JICF, only sinusoidal forcing corresponding to clear lock-in conditions, close to the fundamental shear-layer frequency and/or at very high amplitudes, affected jet structure, with somewhat moderate improvements in molecular mixing. Typically, excitation conditions creating enhanced jet penetration and spread did not correlate directly with improved molecular mixing; there was a stronger correlation of improved mixing with creation of a more symmetric jet cross section, in some cases with a counter-rotating vortex pair structure.