Quiet-flow Ludwieg tube for hypersonic transition research

Abstract

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 x 10(6)/ft (11 x 10(6)/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.