Supersonic jet screech: Half-century from Powell to the present

Under certain conditions, shock-containing jets produce an intense tone ref erred to as screech. Screech was discovered about half a century ago by Ala n Powell in England. Here I recount developments in supersonic jet screech - from Powell's first observation in 1951 to now. During this period more t han 200 papers have been published - many offering only incremental advance s. This paper provides a concise screech resource including a historical pe rspective, a summary of recent developments and a critical assessment of th e state of the art. Topics include modulation of instability waves by shock s, shock-cell models and screech frequency prediction models, unsteady shoc k motions and clues about their role in shock noise generation. also. detai led nearfield measurements and computer simulation methods now available ar e discussed. However, despite the advances, screech amplitude prediction re mains an elusive but increasingly important goal not only due to concerns a bout sonic fatigue failure of aircraft structures but because knowledge gai ned by the study of screech can be applied to a variety of resonant flow si tuations, including jet impingement, cavity resonance, and closed-loop acti ve flow control. (C) 1999 Academic Press.