These photographs show the vortex structures that result from the interaction of vortices that are shed from a 2D bluff body and those shed from a slot jet. The slot jet (3 mm x 150 mm) is located in the center of the rectangular face of the bluff body (15 mm x 240 mm). The photographs are positioned so that the velocity of the slot jet increases from left to right. In the first three photographs starting from the left, the velocity of the jet is smaller than the velocity of the flow around the bluff-body. In the fourth picture, the shear layer velocities of the jet and bluff body are nearly equal and a wavy structure is observed. At higher velocities, as noted by the 5th and 6th photographs, the vortex structures from the jet dominate the flow field. This is noted by the change in the direction of rotation of the vortices.

The flow is visualized by the Reactive Mie Scattering (RMS) technique in which Mie scattering is observed from micron size TiO2 particles that are formed by the spontaneous reaction of TiCl4 vapor in the slot jet air with the water in the annulus air. The technique has been shown to be more effective than smoke because it highlights the streamlines where molecular mixing is taking place. The photographs were taken in the 15ns firing of a YAG laser used to form the light sheet.

For an averaged air jet velocity of 18.5 cm/s, the alternating vortex structures shed from the 2D bluff body are evident after about 5 bluff-body widths downstream. As the jet velocity increases, the wake from the bluff body is significantly modified.