Theoretical and experimental investigation of coherent structure in the turbulent boundary layer

This project combines both experimental video flow visualization studies and theoretical investigations of a series of phenomenological and theoretical models based upon the three dimensional details of convected, coherent structural elements of a turbulent flow as it interacts with a solid surface. The experimental program has considered a range of sub-problems including high Reynolds Number (4 million) turbulent flows, the effect of surface modification on low-speed streak formation, and the effect of vortex loop interaction with a solid boundary. To augment the visualization pictures, a computerized video-digitizing system has been implemented. Results show promise for obtaining quantitative data from low visualization pictures. The specific thrust of the theoretical studies has been focussed on three areas: how two and three dimensional vortex structures interact with wall boundary layers, the development of a new type of prediction method for two dimensional turbulent boundary-layer flows, and improvement in numerical techniques for solving parabolic, boundary-layer equations.