The screeching jet, seen from all sides

Abstract

Shock-containing supersonic jets undergoing resonance processes are challenging from both a measurement and simulation perspective. These jets are host to a broad range of complex fluid phenomena: intense acoustic waves, turbulence, wavepackets and strong shock waves. Strong shocks present a challenge to both the experimental and numerical researcher. In the paper of Léon et al. (J. Fluid Mech., vol. 947, 2022, A36), a novel optical technique based on multi-axis digital holographic interferometry is applied to the study of a highly underexpanded screeching jet, producing density measurements of unprecedented clarity and resolution. Where prior studies have been restricted to extrapolating the three-dimensional field from two-dimensional slices or projections, in this work the authors directly measure the three-dimensional helical structure of the wavepacket associated with jet screech.