Transition Research with Temperature-Sensitive Paints in the Boeing/AFOSR Mach-6 Quiet Tunnel

Abstract

Abstract : The Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) is used for the study of noise effects on transition. A 12-inch ball valve was installed in the BAM6QT in April 2011, replacing a slow gate valve. This ball valve allows the tunnel to run without the use of diaphragms, though experiments are still typically run with the double burst diaphragm system. Four projects in the BAM6QT are also described in this paper. The first 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 compared to theory. The second project tested two von Karman ogive models. On the 7.62-cm- diameter ogive model at 0-deg angle of attack, the flow remained laminar for a smooth nosetip, a nosetip with a two-dimensional roughness strip, and a nosetip with distributed roughness. Isolated roughness elements larger than 51 m cause transition on this model at higher Reynolds numbers. A smaller 5.08-cm-diameter ogive model was constructed to allow the model to start at 2-deg angle of attack and to prevent a reflected bow shock from impinging on the model. Transition occurred on the lee ray on the smaller model. Forward-facing and aft-facing steps on the model nosetip did not appear to affect transition. Third, a 3-m circular-arc flared cone was run in different axial positions in the tunnel to determine if there was an effect. Sensors were also installed aft of the model to try to measure noise levels with an installed model in an attempt to show that transition occurs on the cone in fully quiet flow. For the last project, roughness dots were added to the same flared cone in an attempt to change vortex spacing. The flared cone remains a subject for future research.