Wall-Bound Streamwise Vortices Formed by Embedded Jets in a Turbulent Boundary Layer

The interactions of a pair of adjacent rectangular wall jets having the same orifice with the inner layer of a flat plate turbulent boundary layer are investigated in wind tunnel experiments in which the characteristic length scales of the yawed jets’ orifices are an order of magnitude smaller than the boundary layer thickness. In the present investigations, specific emphasis is placed on the effects of the primary and relative jet yaw angles within the range 45 <  < 75 and on their relative mass flow coefficients 0.1 < Cq < 0.25. It is shown that while the interactions of each wall jet with the embedding boundary layer results in the formation of a surface-bound, single-sign vortex, the streamwise evolution of the vortex pair depends on the spanwise positions of the yawed jets relative to the direction of the free stream. The spanwise interactions of the jet-induced vortices are strongly dependent on the jets relative yaw angles, resulting in varied topologies that range from a fully coalesced single vortex to a pair of weakly interacting vortices. It is also shown that the interaction of the two jets can lead to a nearly uniform spanwise momentum flux recovery that within the present parameter range is up to 50% of the boundary layer momentum flux deficit at 100 equivalent orifice diameters downstream from the jets’ orifices, and that the net momentum flux gain varies linearly with the relative jets Cq.