Near-field character of a jet discharged through a wall at 30 deg toa mainstream

Measurements are reported of the flow created by the injection of a circular jet at 30° through a plane wall, past which an external stream is flowing. Attention has been focused on the region immediately surrounding the injection hole, which has received slight attention in earlier studies. The data include profiles of streamwise velocity and distributions of static pressure and film-cooling effectiveness on the surface, for ratios of average injection velocity: freestream velocity M of 0.1, 0.2, 0.5,1.0, and 1.5. Flow visualization photographs also are presented. Two modes of behavior are observed, according to the magnitude of M. For values of 0.3 and less, the injected jet remains attached to the surface, provoking considerable pressure and velocity disturbances, and giving rise to increasing effectiveness as M is increased. At values of M of 0.5 and above, the jet lifts off the surface, allowing penetration of the mainstream fluid beneath it. As a consequence, the effectiveness now diminishes as M is augmented, as are the surface pressure disturbances, and a complex flow structure is produced. Maximum effectiveness and coverage is observed when M is about 0.5, in conformity with earlier studies.