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

The development of the large-scale turbulentstructures is experimentally investigated in bothimpinging jets and three-dimensional wall jets. Anazimuthal decomposition of the fluctuating wallpressure in the impinging jet revealed the presenceof large-scale ring structures; however these ringstructures did not appear to impact the wallconcentrically. Thedevelopmentof three-dimensional wall jets exiting rectangularchannels with aspect-ratios from 1 to 8 wasinvestigated using the turbulent velocity andmeasurements of the fluctuating wall pressure. Thedevelopment was found to be delayed by increasing thechannel aspect-ratio but the length-scales in thedifferent jets could be collapsed by scaling thestreamwise coordinate by the square root of thechannel cross-sectional area and normalizing by thesize of the channel. Pressure-velocity correlationsindicate that the large-scale structures in theseflows are strongly asymmetric.