Explortion of the linear disturbance modes in a wall-bounded turbulent shear flow and bridging the gap between their structures and the turbulent statistics

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In this study, artificial pulse jet disturbance from to a wall surface is introduced to a flat-plate turbulent boundary layer using a small speaker and development of the disturbancewas investigated using hot wire anemometry. The velocity signals were ensemble-averaged with phase of the initial disturbance. This averaging enables extraction of disturbance components related to the artificial disturbance. The result shows that their disturbance structure does not depend on strength of the initial disturbance and that amplitude of these disturbances are proportional to that of the initial disturbance. This is evidence that there exist linear disturbances in a turbulent boundary layer. This linear disturbance would be greatly utilized in analysis and prediction of turbulence statistics in not only the turbulent jet but also wide-ranging turbulent shear flows.