Development of the Large-Scale Structures in the Intermediate Region of the Three-Dimensional Wall Jet

The development of the large-scale structures in the intermediate region of the three-dimensional wall jet was examined using measurements of the mean streamwise vorticity and the two-point, two-time correlations of the streamwise fluctuating velocity in the vertical and lateral directions. It was found that a dominant large-scale double horse-shoe structure persisted to 40 diameters downstream of the jet exit. It was also found that the structure continued to evolve throughout the intermediate field. In particular, the inner horse-shoe vortex was induced toward the wall, while the position of the outer horseshoe vortex relative to the half-width moved toward the centerline. The inclination of this structure relative to the wall also increased as the flow evolved downstream. These changes in the structure combined to cause the lateral spread rate of the jet to aprroximately double in the intermediate field.