The Role of the Large-Scale Structures in Turbulent Wall Jets

The development of the large-scale turbulent structures is experimentally investigated in both impinging jets and three-dimensional wall jets. An azimuthal decomposition of the fluctuating wall pressure in the impinging jet revealed the presence of large-scale ring structures; however, these ring structures did not appear to impact the wall concentrically. The development of three-dimensional wall jets exiting rectangular channels with aspect-ratios from 1 to 8 was investigated using the turbulent velocity and measurements of the fluctuating wall pressure. The development was found to be delayed by increasing the channel aspect-ratio, but the length-scales in the different jets could be collapsed by scaling the streamwise coordinate by the square root of the channel cross-sectional area and normalizing by the size of the channel. Pressure-velocity correlations indicate that the large-scale structures in these flows are strongly asymmetric.