Effect of Computational Method on Discrete Roughness Correlations for Shuttle Orbiter

A reanalysis of discrete roughness boundary-layer transition data using a consistent computational method for comparison to other published results has been completed. The primary objective of this effort was to investigate the influence of the computational approach on the resulting transition correlation. The experimental results were previously obtained on Space Shuttle Orbiter models in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. The phosphor thermography system was used to monitor the status of the boundary layer via global heat- transfer images of the orbiter windward surface. The existing roughness transition database included a variation in the size and location of discrete roughness trips along the centerline of 0.0075-scale models at an angle of attack of 40 deg. Various correlative approaches were attempted, with the roughness transition correlations based on edge properties providing the most reliable results. When a consistent computational method is used to compute edge conditions, transition data sets for different moderately blunt configurations at several angles of attack are shown to collapse to a well-behaved correlation. The shuttle experimental dataset presented herein, therefore, can be used to calibrate the preferred computational method of the end user for use in the future designs of the next-generation space access vehicles.