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

摘要

This grant was redirected to focus on the search for high-Reynolds- number quiet flow in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue. Quiet flow with freestream noise levels comparable to flight requires maintaining laminar nozzle-wall boundary layers; this becomes increasingly difficult, and increasingly useful, as the Reynolds number increases. After nearly five years of shakedown, quiet flow was finally achieved to a freestream unit Reynolds number of 2.8 million per foot, in early 2006. Although this is 90% of the prefabrication design value, it is achieved only intermittently. The masimum feasible quiet-flow Reynolds number remains to be determined, along with the conditions for achieving it reliably. Nevertheless, the facility is presently the only hypersonic quiet tunnel, anywhere in the world, and affordable operating costs have been maintained.