Evolution of Streamwise Vortices Formed by an Inclined, Yawed Round Surface Jet within a Turbulent Boundary Layer*

The interaction of a round surface jet with a flat plate turbulent boundary layer [Rex = O(10⁶)] in a uniform stream is investigated in wind tunnel experiments.  The jet whose diameter d is an order of magnitude smaller than the local characteristic boundary layer thickness issues at a range of prescribed pitch and yaw angles relative to the free stream.  Of specific interest are spanwise distributions of cross stream momentum flux relative to the baseline boundary layer and the evolution of uneven counter-rotating axial vortex pairs that are induced by the shear between the cross flow and the jet.  It is shown that momentum flux increment through streamwise-normal planes 75d downstream of the jet’s orifice relative to the baseline boundary layer decreases monotonically with yaw angle, and can even evolve into a slight momentum deficit.  While the axial vortex on the straboard side of the yawed jet becomes weaker with increasing yaw angle as the leeward side vortex intensifies it nevertheless persists downstream and can be detected even at 50d.  The dominant axial vortex intensifies (as measured by its circulation) with increasing yaw and lower pitch angles and often spawns a secondary axial vortex of opposite sense near the surface.