| An experimental investigation of a shear layer using particle image velocimetry (PIV) to acquire instantaneous realizations of the flow field was conducted. Detailed PIV data were acquired across the primary flow inlet region as well as over a large downstream domain. The instantaneous flow field observations were used to create ensemble flow field statistics. The initial momentum thickness was thetao = 1.11 mm. The mean inlet velocity of the primary flow was Uo,x=0 = 4.51m/s. The Reynolds number, based on these scales, was Rethetao = 321. Boundary layer results nominally agreed with the Blasius solution at x=0.; The experimental facility's spatial constraints created a large scale recirculating flow. The primary flow velocity was U o = 4.6m/s in the downstream data region: 495 < x/thetao < 567. The growth rate of the downstream shear layer, within the range of u/Uo=0.13 to 1.0, was dtheta/dx = 0.032. This growth rate is indicative of a single stream shear layer.; A topological 'collapsed sphere' surface was used to analyze across the single stream shear layer region over the downstream range noted above. Singular points (nodes and saddles) were identified in the instantaneous velocity fields. Large scale coherent motions were identified in a convection speed reference frame. The subset of these motions, which could be fully characterized, exhibited the following quantities: (i) mean location of a coherent motion center: u/Uo=0.66 isotach, (ii) size of the average motion &angl0;Lq x&angr0;=3.34 where L2 is the area bounded by the circulation contour, (iii) strength of the spatially averaged motion &angl0;w&d1; Zq&parl0;518qo&parr0; U&d1;o&angr0;=- 20.4. |
