Spreading rate and reattachment of coaxial jets of high mean-velocity ratio

The flow characteristics of coaxial jets at five high mean-velocity ratios are investigated. Results show that the spreading rate in the mixing regions of the coaxial jets of high mean-velocity ratio depends on the zone where it is located. The rates in the outer mixing region of the initial merging zone and in the fully merged zone are the same and slightly higher than those in the intermediate merging zone, and these rates are independent of the mean-velocity ratio. On the other hand, the spreading rate of the inner mixing region depends greatly on the mean-velocity ratio, and it is found to approach that of a single jet. In addition, reattachment of the outer high velocity flow at the central axis also depends on the mean-velocity ratio, though to a lesser extent.