Development of Diamond Roughness Elements for Boundary-Layer Transition Experiments in Mach-6 Quiet Flow

The Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) at Purdue was used to refine diamond trips for a parametric investigation of the effect of trip height on boundary-layer transition on a 10° half-angle cone with a nominally sharp nosetip. Building off of earlier testing in the BAM6QT, micro-precision 3D printed trips were tested as well as conventionally machined trips. Experiments were conducted at 0° angle of attack (AoA) at different freestream unit Reynolds numbers in quiet, low-noise flow. Infrared thermography and PCB pressure sensors were used to record the state of the boundary layer and observe transition behavior. The trips were then characterized thoroughly with a Zygo Zegage 3D optical profilometer in an effort to identify how imperfections in the trips affect the data.