Investigation of a turbulent spot using

Kurzfassung

Stereoscopic and Multi-plane PIV measurements on artificially excited turbulent spots in a flat plate boundary layer have been performed. The investigation was focused on the substructures and the development of the spot. Instantaneous velocity vector fields have been examined in order to quantify the local and global dynamics of the structures leading into fully turbulent flow. A statistical analysis of the spot flow field has been carried out from the measurements consisting of calculations of ensemble averages, rms-fields, Galilean accelerations, probability density functions and space-time-correlations of the velocity fluctuations, the Reynolds stresses of all four quadrants and the y-component of the vorticity. The dominant substructures have been identified as relative ordered hairpin-like vortices and wall near streaks. This model enables an explanation for the growth of the spot in both stream-wise and span-wise directions and the self-similar arrowhead shape.