Experimental Investigation Of Coherent Structures Influenced By Periodic Blow-Suction Disturbance In Turbulent Boundary Layer

In this paper, the technique of constant temperature anemometry, together with double-hot-wire-sensor probe, is used to carry out experimental study on the turbulent boundary layer, which is controlled by periodic blow-suction disturbance in the low turbulent level wind channel. In the experiment, time sequence of longitudinal velocity component and normal velocity component within and without different periodic blow-suction disturbance, along different normal positions in a flat-plate turbulent boundary layer has been finely measured by IFA300 constant temperature anemometer with resolution higher than Kolmogorov scale. The scales of multi-scale eddy structures are determined by self-correlation function. It is represented that the coherent structures and intermittency are identified by multi-scale flatness factor based on locally averaged velocity structure functions. Phased-average waveforms for longitudinal and normal fluctuation velocity, as well as Reynolds stress of multi-scale coherent eddy structures in turbulent boundary layer are extracted by this conditional sampling technique. The dynamic course of multi-scale coherent eddy structures'bursting is studied.A periodic blowing/suction disturbance forcing, issued from a 5mm thin latitudinal slot of the flat, is introduced to alter multi-scale ingredients of coherent eddy structure and their energy distribution in turbulent boundary layer, what is more, to research the influence of periodic blowing/suction disturbance forcing on the multi-scale coherent structures in flat boundary layer. It is found that within periodic suction disturbance forcing, both the intensity and energy of coherent structures increase, moreover coherent structures at each scales are detected, in view of the changes of conditional phase-averaged waveforms for longitudinal and normal fluctuation velocity of multi-scale coherent eddy structures.