Measurements of structure angle in a supersonic turbulent boundary layer with zero and adverse pressure gradients are presented. Conditionally sampled measurements of u, v, and uv are presented along with quadrant analysis of the turbulent fluctuations. The latter suggests ambiguities associated with the interpretation of VITA measurements. Preliminary results of experiments on artificially generated hairpin vortices are also discussed. Measurements indicate a high degree of similarity between the signatures of these hairpin structures and ensemble averaged events in the turbulent boundary layer. Keywords: Turbulence, Boundary layer, Supersonic Flow.

This three-year contract originally had two tasks: to investigate the structure of flat plate supersonic turbulent boundary layers (Task A), and to investigate longitudinal curvature effects in turbulent boundary layers (Task B). As a result of the work performed under these task headings, we identified a need to study the structure of simple, wall-bounded vortex loops. This investigation (Task C) commenced in the third year, and we feel that it has made a major contribution to our understanding of the ensemble-averaged structure of low and high speed turbulent boundary layers. The progress reported here is that achieved in completing these three tasks. Keywords: Turbulent flow; Eddies(Fluid mechanics); Flow visualization.

A good understanding of turbulent compressible flows is essential to the design and operation of high-speed vehicles. Such flows occur, for example, in the external flow over the surfaces of supersonic aircraft, and in the internal flow through the engines. Our ability to predict the aerodynamic lift, drag, propulsion and maneuverability of high-speed vehicles is crucially dependent on our knowledge of turbulent shear layers, and our understanding of their behavior in the presence of shock waves and regions of changing pressure. Turbulent Shear Layers in Supersonic Flow provides a comprehensive introduction to the field, and helps provide a basis for future work in this area. Wherever possible we use the available experimental work, and the results from numerical simulations to illustrate and develop a physical understanding of turbulent compressible flows.