Wake Vortices in Jets in Crossflow

Among the different vortical structures present in the canonical jet in crossflow flow field, the wake vortices are probably the least understood. The available experimental data suggests that these structures are formed by the separation of the crossflow boundary layer due to the adverse pressure gradient from the blockage provided by the jet core and due to the vertical lift generated by the counter rotating vortex pairs (CVP) [1–5]. Through this work, we hope to address the relative importance of these different formation mechanisms by performing high fidelity large eddy simulations of a non-reacting uniform density jet in crossflow flow field for a range of velocity ratios (R) at a fixed crossflow Reynolds number. These conditions are identified to mimic the experiments of Fric and Roshko [1] who observed distinct wake vortices behavior at different R values. We aim to investigate the dynamics of wake vortices at these conditions and characterize the correlations between the strength and growth rates of the vortices with the lift generation from the CVPs and the blockage provided by the jet fluid. This is done by systematically suppressing the CVP structure strength in the jet in crossflow flow field while keeping the jet penetration/blockage fixed.

[1] Fric, T. F., and Roshko, A., “Vortical Structure in the Wake of a Transverse Jet,” Journal of Fluid Mechanics, Vol. 279, 1994, pp. 1–47. https://doi.org/10.1017/S0022112094003800

[2] Kelso, R. M., Lim, T. T., and Perry, A. E., “An Experimental Study of Round Jets in Cross-Flow,” Journal of Fluid Mechanics, Vol. 306, 1996, pp. 111–144. https://doi.org/10.1017/S0022112096001255

[3] SMITH, S. H., and MUNGAL, M. G., “Mixing, Structure and Scaling of the Jet in Crossflow,” Journal of Fluid Mechanics, Vol. 357, 1998, pp. 83–122. https://doi.org/DOI: 10.1017/S0022112097007891

[4] Lozano, A., Smith, S. H., Mungal, M. G., and Hanson, R. K., “Concentration Measurements in a Transverse Jet by Planar Laser-Induced Fluorescence of Acetone,” AIAA Journal, Vol. 32, No. 1, 1994, pp. 218–221. https://doi.org/10.2514/3.11974

[5] Kelso, R. M., and Smits, A. J., “Unsteady Wake Structures in Transverse Jets,” 1993.