Space-time correlations from a 143 hot-wire rake in a high Reynolds number turbulent boundary layer

Two-point cross-correlations in a high Reynolds number turbulent boundary layer are presented (Re_θ =19,100). The results are based on wind tunnel measurements performed using a hot-wire rake of 143 single wire probes sampled simultaneously. The wind tunnel is 20 m long and provides a boundary layer thickness of approximately 30 cm. Size of the record length and domain covered by the hot-wire rake show two-point cross-correlations present almost everywhere in the entire boundary layer. The elongated structures are found to be very long especially from the beginning of the log-layer to the lower parts of the outer boundary layer. Footprints of these long elongated structures are even visible in the very intermittent regions of turbulent boundary layer very close to the freestream. The correlation contours also show the interaction between the intermittent region of turbulent boundary layer very close to the freestream and the very near wall region. Details of the experimental set-up are given and a new in situ calibration method in the turbulent flows for hot-wire rakes of many probes is briefly described.