Experiments characterizing nonlinear shear layer dynamics in a supersonic rectangular jet undergoing screech

Abstract

Jet screech is the result of a resonant aeroacoustic feedback loop. In modern high-performance aircraft jet screech has given rise to in-flight sonic fatigue failure of nozzle components. For this reason, jet screech has been the focus of numerous investigations. However, the prediction of screech amplitude has been a very elusive goal. A primary objective of the work to be reported is to experimentally characterize the nonlinear instability wave development in the shear layer of a rectangular supersonic jet undergoing screech. Hot-film probes are used to measure the instability wave development in the jet shear layers along a constant Mach number ray. Higher-order polyspectral techniques are employed to determine resonant nonlinear phase locking between multiple instability modes. A detailed comparison of the “inner loop” hot-film measurements with “outer loop” acoustic measurements is made. Such a comparison reveals the importance of incorporating nonlinear effects into a jet screech amplitude prediction method.