Abstract
Round jets impinging at a counter or a right angle are investigated by the three-dimensional vortex blob method. When the jets impinge at a counter angle, the circular shear layers roll-up into vortex rings that impinge successively in the following manner: As a vortex ring from each jet approach, each ring is stretched in the radial direction by the velocity induced by the counter part. Some distinct clumps are generated in the circumferential direction, growing into azimuthal waves by the symmetrical instability. This predicted mechanism is in good agreement with the experimental observation. On the other hand, when the jets impinge at a right angle, a new vortex ring is generated in the direction of the movement after the impingement. Thus, the vortex structure grows rapidly in this direction. The energy dissipation takes place actively in these vortex-reconnecting regions. It is also found that the velocity distribution normal to the impingement plane takes a Gaussian distribution.
