On the unsteady dynamics of partially shrouded compressible jets

• Published in: arXiv.org
• Main Authors: Nanda, Soumya R, Karthick, S K, Krishna, T V, A De, S Mohammed Ibrahim
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 20.09.2021
• Subjects: Acoustic noise; Compressibility; Far fields; Flapping; Flow separation; Noise; Nozzles; Physics - Fluid Dynamics; Pressure ratio; Separation; Shear layers
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2102.07096

We experimentally investigate a partially shrouded sonic jet (a sonic free-jet shielded by a solid wall-extension on one side) exiting from a planar nozzle at two different nozzle pressure ratio (\(\zeta=4\) and \(5\)). We experimentally show that the inherent jet unsteadiness from the shock-induced flow separation on the wall and the emitted noise in the far-field is strongly coupled through a series of experiments like high-speed schlieren, wall-static pressure, unsteady pressure spectra, and microphone measurements. The partially shrouded jet's lateral free expansion is also identified to be complicated, three-dimensional, and the produced noise is directional. The emitted acoustic pulses from the flapping-jet, the radiated noise from the shock-induced separation on the wall, and the shock-shear layer interaction on the other side of the wall are responsible for the generated acoustic disturbances. The non-uniform aeroacoustic forcing on the top and bottom portion of the partially wall-bounded jet shear layer leads to a self-sustained jet oscillation and a discrete sound emission. The vital features are identified through the proper orthogonal decomposition of high-speed schlieren images and supplemented by other measurements.