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

In this paper, the measurement technique of constant temperatureanemometry, together with double-hot-wire-sensor probe, is used to carryout experimental study on the turbulent boundary layer, which iscontrolled by periodic blow-suction disturbance in the low turbulent levelwind channel. In the present experiment, time sequence of longitudinalvelocity component and normal velocity component within and withoutdifferent periodic blow-suction disturbance, along different normalpositions in a flat-plate turbulent boundary layer has been finelymeasured by IFA300 constant temperature anemometer with highresolution.It is employed that the coherent structures and intermittency are identifiedby multi-scale flatness factor based on locally averaged velocity structurefunctions. Phased-average waveforms for longitudinal and normalfluctuation velocity, as well as Reynolds stress of multi-scale coherenteddy structures in turbulent boundary layer are extracted by thisconditional sampling technique. It is determined the phase relationshipbetween the three. The dynamic course of multi-scale coherent eddystructures' bursting is studied.A periodic blowing/suction disturbance forcing, issued from a 5mm thinlatitudinal slot of the flat, is introduced to alter multi-scale ingredients ofcoherent eddy structure and their energy distribution in turbulentboundary layer, what is more, to research the influence of periodicblowing/suction disturbance forcing on the multi-scale coherentstructures in flat boundary layer. It is found that within periodic suctiondisturbance forcing, both the intensity and energy of coherent structuresincrease, moreover coherent structures at each scales are detected. In themeanwhile, the flow filed, in which a 16Hz blowing/suction disturbanceforcing influences, is determined.