A wavelet-based vector multiresolution technique was developed and applied to a high-resolution stereoscopic particle image velocimetry system for studying the three-dimensional multiscale structure features of the lobed jet mixing flow. The instantaneous three-dimensional velocity vectors were successfully decomposed into large- and small-scale velocity fields, and existence of very strong multiscale turbulent structures were confirmed in the near field of the lobed jet. Within the central scale range of 16 mm, the instantaneous pairs of large-scale streamwise and horseshoe vortices can be clearly observed around the lobe peak regions and lobe troughs, respectively, and begin to breakdown and spread outward at downstream. The stronger small-scale streamwise vortices were found in the lobe regions, which first spread outward along the lobes and then develop to the whole measured flowfield. These small-scale streamwise vortices also play an important role in the enhance mixing process. The stronger alternate positive and negative peaks of small-scale axial velocity component, which appear at the trailing edge of the lobed nozzle in the near field, indicate the existence of the Kelvin-Helmholtz or normal vortices. References: 20
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