Hypersonic Boundary-Layer Transition Experiments in the Boeing/AFOSR Mach-6 Quiet Tunnel

This paper reports progress from six different projects studying hypersonic boundarylayer transition. Efforts to measure instabilities in the wake of an isolated roughness element in the laminar nozzle-wall boundary layer of the BAM6QT are on-going. A new set of instabilities have been measured when the roughness is at a height that causes incipient transition within the measurement range. The second project tested a method of calibrating temperature-sensitive paints using Schmidt-Boelter heat transfer gauges. A 7-deg half-angle cone was tested at 0-deg angle of attack and the heat transfer compared well with theory. A forward-facing cavity was used to identify the critical depth where self-sustaining oscillations begin. This was found to be about 1.2 cavity diameters. A shock tube is being constructed at Purdue to calibrate PCB-132 sensors. The tube will create clean, weak shocks of a magnitude similar to a second-mode wave in a wind tunnel, allowing accurate calibrations for instability measurements. A flared cone was tested in the BAM6QT, and showed natural transition under fully quiet flow. The streamwise vortices visible on the surface of the cone were found to be body fixed. A blunt 3-deg half-angle cone was tested with various distributed and isolated roughness elements.