Multidimensional Structure of Wall Bounded Turbulence-Continuation

摘要

Broad goals of the work were to study the structure of the turbulent wall layer using modern particle image velocimetry techniques to measure instantaneous velocity fields and to interpret the structure. Earlier work (C. D. Meinhart, Ph.D. Thesis. Univ. Illinois, 1994) supported by ONR had suggested that low momentum regions are created in wall turbulence by the alignment of hairpin vortices, but the field of view of this work was not wide enough to see entire groups of vortices and the patterns in which they formed. Experiments were conducted in boundary layer using wide-angle PIV measurements that gave views of structure that had not been attainable before. They show that the hairpins definitely occur in packets that grow more or less linearly at an angle of 12 +/- 6 degrees with respect to the wall. Packets contain up to 12 hairpins were observed.