Control of a jet-in-cross-flow by periodically oscillating tabs

• Published in: Physics of fluids (1994) 2012-05, Vol.24 (5), p.055107-055107-15
• Main Authors: Zaman, K. B. M. Q., Milanovic, I.
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Flow control; Fluid dynamics; Fundamental areas of phenomenology (including applications); Instrumentation for fluid dynamics; Physics
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.4719150

A technique for active control of a jet-in-cross-flow (JICF) is explored in this study. Two triangular tabs are placed at the 90° and 270° edges of the jet orifice, relative to the direction of the cross-flow. An asymmetry in the placement of the two tabs is reversed periodically. This causes a profound oscillation of the flow field that persists as far downstream as permitted by the measurements in the facility (100 orifice diameters). Parametric dependence of the unsteadiness and its impact on the flow field is investigated. It is found that the effect becomes more pronounced with increasing value of the momentum flux ratio ( J ) while there is little or no effect in the range, J < 15. The effective frequencies of oscillation are low - more than an order of magnitude lower than that found with oscillatory blowing technique in previous studies. Flow visualization indicates that the oscillation has no impact on the "wake vortices". The kidney-shaped cross section of the JICF is seen to tilt side-to-side periodically. The flow mechanism apparently involves a direct perturbation of the counter-rotating streamwise vortex pair of the flow.