Measuremental Investigation Of Multi-scale Coherent Structure In Turbulent Boundary Layer With Hotwire Anemometry

In this paper, the experimental measurement investigation is carried out in aturbulent boundary layer with hot-wire anemometry and several kinds of hot-wireprobes. Time sequence of longitudinal, normal and spanwise velocity component atdifferent vertical locations across a turbulent boundary layer under different Reynoldsnumbers has been finely measured by IFA300constant temperature anemometer withTSI-1211-T1.5、TSI-1240-T1.5、TSI-1243-T1.5types probes.Skin friction velocities, skin friction shear stress and skin friction coefficients overturbulent boundary layer are measured according to the relationship of the logarithmiclaw of mean velocity profile and skin friction velocity, fluid viscosity coefficient etc.，inner scale physics quantities the relationship of skin friction velocity and skin frictionshear stress. The variations of statistic mean characteristic profiles, such as meanvelocity, turbulent intensity, Reynolds stress, skew factor, flatness factor normalizedby inner viscous units in turbulent boundary layer, are investigated versus Reynoldsnumbers. The universality of mean flow field parameter normalized by inner viscousunits is investigated versus Reynolds numbers for turbulent boundary layer.On the basis of theory and methodology of turbulence local average, the conceptof coarse-grained local averaged velocity structure functions is put forward todescribe the relative motions and deformation between the two neighboring eddystructures with a definite resolution and scale. The equivalence between wavelettransform with asymmetric wavelet and velocity local averaged structure function isverified for turbulence instantaneous velocity signals.The detection criteria for multi-scale coherent structures eduction in turbulentboundary layer is put forward by employing wavelet coefficient intermittent factorand flatness factor of instantaneous longitudinal fluctuating velocity as a detectingindex. The conditional phase-averaged eigen-waveform for streamwise, normal andspanwise velocity component, as well as Reynolds stress in turbulent boundary layerare extracted. The scale-similarity of dynamical evolution process for multi-scalecoherent structure is analyzed. The phase relationship among longitudinal velocity,normal velocity and spanwise velocity, as well as its influence on the phased averagedwaveform of Reynolds stress, is analyzed. The amplitude variations of longitudinal velocity, normal velocity, spanwisevelocity and Reynolds stress for multi-scale coherent structure across turbulentboundary layer is investigated. The scale-correlations between coherent structurefluctuating velocity signals are analyzed with correlation function method.Extended self-similarity scaling law is calculated with turbulence local averagedvelocity structure function before and after multi-scale coherent structures areextracted. The influence of multi-scale coherent structures on turbulenceintermittency and ESS singular scaling law is investigated.