Interaction of a Two-Dimensional Bluff Body and Incompressible Jet and Annulus Flows

A particular interaction of bluff body and jet flows was studied using two dimensional slot jet aspect ratio 50 surrounded by a two dimensional bluff body. The coflowing system used air in the annulus and nitrogen in the jet. Flow visualization identified flow patterns containing large vortex structures were observed as jet velocities changed. Laser Doppler Anenometry measurements of instantaneous velocities were examined to characterize the flowfield details, and high speed movies provided qualitative insight into flow dynamics. The concept of jet and annulus fields is introduced. The jet field is the region above the bluff body that extends six or seven slot widths downstream, and the annulus field is the region above the jet field. The annulus flow dictates the flowfield dynamics in the annulus field up to jet-to- annulus velocity ratios of 1.45. The jet is responsible for the formation of the large-scale structures and dominates the flow in the jet field. Jet domination of the entire flowfield is seen at velocity ratios of 1.45 and above. Mie scattering was used to determine shedding frequencies of the large structures. Strouhal number based on jet velocity and slot which was a constant. 0.098.