AIAA Journal, cilt.46, sa.7, ss.1757-1763, 2008 (SCI-Expanded)
Nearly all hypersonic tunnels have turbulent nozzle-wall boundary layers that radiate acoustic noise, generating high freestream noise levels that are an order of magnitude above flight levels. A new Mach-6 quiet tunnel has been developed to provide quiet flow at high Reynolds number with low noise levels, comparable with flight. Laminar nozzle-wall boundary layers and the resulting quiet flow have now been achieved to high Reynolds numbers of 3.5 × 106/ft (11 × 106/m), after five years of shakedown. The Mach-6 quiet tunnel is the first operational hypersonic quiet tunnel with low operating costs and good optical access.