Turbulent Boundary Layer Inner-Outer Interactions

摘要

A summary of work performed to study the interactions between the inner and outerregions of a turbulent boundary layer is presented. The interactions were studied by observing the response of the boundary layer to different perturbations. The inner region was modified by adding surface roughness, and the outer region suppressed using LEBU's. Velocity measurements were made with a three component LDV, a scanning LDV, and an X-type hot-film probe. The scanning LDV was developed to obtain continuous time history measurements of instantaneous velocity profiles down to y+ = 10. Details of the structure of bursts, sweeps, and shear layers over smooth and rough walls were determined using conditional sampling with simultaneous measurements from a detector probe and a mapping probe. This allowed the mapping of the complete three-dimensional structure of the three-component velocity field for these structures. Both single point detection, using quadrant and VITA techniques, and a unique spatially coherent structure detection technique were used. The spatial detection technique developed in this project takes advantage of the two-dimensional velocity field information obtained from the scanning LDV. Scanning laser doppler velocimeter, Burst, Sweep, Shear layer large scale structure, Conditional sampling, Rough wall, LEBU Device, Convection velocity, Spatial detection, Two and three dimensional mapping.