| A low Reynolds number, zero pressure gradient, incompressible turbulent boundary layer was investigated using a volumetric imaging technique. The boundary layer had a Reynolds number based on momentum thickness, Re;The relationship between outer large-scale structure and the low-speed streaks in the near-wall region was examined by resampling the data volumes along x-y planes. The ejection of brightly-dyed fluid packets from the near-wall region was observed to be spatially organized, and related to the passage of the large-scale scalar structures in the outer portion of the boundary layer.;The volumetric scalar data set was compared to the numerical simulation of the passive scalar field in a turbulent boundary layer, carried out by Prof. P. K. Yeung (currently at the Georgia Institute of Technology) and Prof. T. Brasseur at the Pennsylvania State University. Detailed volumetric analysis of the volumetric scalar and enstrophy field showed a high degree of correspondence between the experiment and computation. The comparison reinforced confidence in both the experimental methods used here and the incorporation of scalar sources into numerically simulated flows.;The primary data set was analyzed using both qualitative and quantitative image processing techniques in order to investigate the role of coherent structure in the turbulent boundary layer. Large-scale coherent structures were identified using ray-traced, anaglyph stereoscopic visualizations of the fifty volumes. Examination of the stereograms revealed large-scale organization of the scalar structure in the outer portion of the boundary layer. Scalar structures were observed to lie along lines in the x-z plane, inclined to the x-direction in the range... |
