A direct numerical simulation of a square jet ejected transversely into a laminar boundary layer was performed at a jet-to-main-flow velocity ratio of 9.78 and a jet Reynolds number of 6330. The jet consisted of a single pulse with a duration equal to the time required for the jet fluid to travel 173 jet widths. A strongly-favorable streamwise pressure gradient was applied to the flat-plate flow and produced a freestream acceleration that is above the typical threshold required for relaminarization. The results of the simulation illustrate the effect of the favorable streamwise pressure gradient on the flowfield created by the transverse jet. The upwind shear layer of the jet is unstable to a Kelvin-Helmholtz-like instability and rolls-up into discrete shear-layer vortices. Vorticity from the jet shear layer accumulates near the corners of the jet and produces vertically-oriented vortex pairs near the upwind and downwind corners of the jet. The upwind pair couples with the shear-layer vortices to produce large, counter-rotating vortices in the freestream, while the downwind pair is unstable, and periodically produces hairpin-like vortices in the mainflow boundary layer and elongated, downwards-oriented vortices in the freestream behind the jet. The departure of the jet flowfield from that typically observed in transverse jets illustrates the effect of the favorable streamwise pressure-gradient on the flowfield created by the jet.

Additional Metadata
Persistent URL dx.doi.org/10.1007/s10494-012-9406-z
Conference 7th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2011
Citation
Brinkerhoff, J.R. (Joshua R.), & Yaras, M. (2011). Direct numerical simulation of a square jet ejected transversely into an accelerating, laminar main flow. In 7th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2011. doi:10.1007/s10494-012-9406-z