Previous experiments performed on a sub-scale BOLT model in the Purdue University Boeing/AFOSR Mach-6 Quiet Tunnel showed asymmetric transition on the measurement surface due to a misalignment of the nosetip with the model frustum. These results motivated a test campaign to determine the effect of forward and rearward facing steps with a more controlled step height, and to define the allowable size of steps for the final flight vehicle. Eight different nosetips were fabricated to create forward and rearward facing steps with heights of 0.003, 0.006, 0.010, and 0.020 inches on the leading edge at the nosetip-frustum junction. Wind tunnel tests were performed at α = 0° and 4 and β = 4°, and the location of transition onset was measured. Using the information from the experiments coupled with computational simulations, transition correlations were developed to aid in sizing the flight-vehicle joint-step heights and the step height for the secondary-side flight experiment.
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