Study of the compressible flow in a diffusing S-duct

Attention is given to aerodynamic data for compressible flow through a representative S-duct configuration. Measurements of the 3D velocity field, total pressures, and static pressures were obtained in five cross-sectional planes. Surface static pressure and surface flow visualization data were also acquired. All reported tests were conducted with an inlet centerline Mach number of 0.6. The Reynolds number, based on the inlet centerline velocity and duct inlet diameter, was 2.6 x 10 exp 6. It is shown that a region of streamwise flow separation occurred within the duct. Measurements indicate that the duct curvature induced strong pressure-driven secondary flows. The crossflows evolved into counterrotating vortices. These vortices convected low momentum fluid of the boundary layer toward the center of the duct, degrading both the uniformity and magnitude of the total pressure profile. (AIAA)