TURBULENT-FLOW AROUND A BLUFF RECTANGULAR PLATE .1. EXPERIMENTAL INVESTIGATION

Measurements are reported for the separated reattaching flow around a long rectangular plate placed at zero incidence in a low-turbulence stream. This laboratory configuration, chosen for its geometric simplicity, exhibits all of the important features of two-dimensional flow separation with reattachment. Conventional hotwire anemometry, pulsed-wire anemometry and pulsed-wire surface shear stress probes were used to measure the mean and fluctuating flow field at a Reynolds number, based on plate thickness, of 5 x 10(4). The separated shear layer appears to behave like a conventional mixing layer over the first half of the separation bubble, where it exhibits an approximately constant growth rate and a linear variation of characteristic frequencies and integral timescales. The characteristics of the shear layer in the second half of the bubble are radically altered by the unsteady reattachment process. Much higher turbulent intensities and lower growth rates are encountered there, and, in agreement with other reattaching flow studies, a low frequency motion can be detected.