The Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University
Tunnel has a 9.5-inch exit diameter, runs for about 10-sec. about once an hour for about $10/shot. Uses Ludwieg tube concept. Designed to achieve laminar nozzle-wall boundary layers for study of laminar-turbulent transition processes under low-noise conditions comparable to flight. See, for example, AIAA Paper 2002-0302, January 2002.
Built during 1995-2001 with major funding from the Boeing Company and The Air Force Office of Scientific Research. Additional funding from the Ballistic Missile Defense Organization, Sandia National Laboratory, and a gift in memory of Kenneth Hobbie.
Watch this video of Assistant Professor Joseph Jewell, touring the Boeing/AFOSR Mach-6 Quiet Tunnel