Hypersonic Transition Testing in Wind Tunnels

Abstract

Historically, the wind tunnel has been the major source of boundary-layer transition information. Often these wind tunnel data have become the primary data base used to develop transition correlations and to establish transition criteria for flight. During the late 1950’s and the 1960’s, the identification and understanding of wind tunnel freestream disturbances provided an explanation for wind tunnel transition Reynolds numbers being smaller than flight transition Reynolds numbers.A quiet wind tunnel (freestream dusturbance amplitudes reduced to a small value) was proposed a a way of obtaining wind tunnel transition Reynolds numbers which would be comparable in magnitude to flight values. The purpose of this paper is to discuss the position that one should not expect a transition Reynolds number obtained in any wind tunnel, conventional or quiet, to be directly relatable to flight.