The near field of a confined coaxial square jet configuration has been investigated using a two-component laser Doppler anemometer. Measurements at velocity ratios (? u = U o/U i) 0.5, 1.0, and 2.0 with a fixed mean velocity (0.7 m/s) for the inner stream were obtained. Reynolds numbers based on the average velocity of the two coflowing streams UM and the jet equivalent diameter D e were ranged from 1.53 × 10 4 to 4.2 × 10 4. The streamwise vortices generated at the corners of the inner square nozzles had affected the downstream flow development considerably. The spreading rate at ? u = 0.5 was found to be the highest among the three cases investigated and that for respective cases were also higher than their circular counterparts under similar flow conditions. Self-similarity can be attained and is in the order of ? u = 0.5, 1.0, and 2.0. The difference can be attributed to the relative strength as well as the sense of rotation for the corner streamwise vortices generated by the inner jet. The downstream developments for various velocity components are presented. Finally, the flow structure at different velocity ratios will be briefly discussed via inviscid vortex dynamics.
|Number of pages||8|
|Publication status||Published - 1 May 2004|
ASJC Scopus subject areas
- Aerospace Engineering