“Scale-specific Intermittency and Spatio-temporal Correlations in a Supersonic Jet”


Publication Type:
Conference
Authors:
Co-Authors:
L. Agostini and D. Gaitonde
Year Published:
2016
Abstract:
Nearfield intermittency and spatio-temporal correlations of a Mach 1.3 cold jet are analyzed to highlight the filtering and directivity of turbulence scales. The intermittent wavepackets at the end of the potential core are found to occur primarily between St = 0.5 and St = 1 from the Hilbert Spectrum and the spec-trogram. The component scales of centerline turbulent and nearfield signals are extracted through Empirical Mode Decomposition which provides narrow band signals for each pertinent range of frequencies. Scale specific causality analysis identifies well demarcated source regions along the jet axis for each band of frequencies along upstream, sideline and downstream directions. 2D spatio-temporal correlations identify components at St = 1.5 from the core collapse location to correlate well with the shear layer dynamics and they are identifiable with the sideline radiation. Components responsible for the highly directional downstream radiation patterns as well as axially propagating hydrodynamic features are also differentiated. Timescale analysis clearly demar-cates the nearfield regions with the lowest, intermediate and largest scales. The fundamental filtering property of the jet is examined by tracking " native " perturbations obtained through Synchronized Dual LES. Turbulence is found to modulate the propagated signal reaching a location so as to impart characteristics similar to the signal native to that corresponding location.
Conference Name:
54th AIAA Aerospace Sciences Meeting
Conference Location:
San Diego, California
Other Numbers:
Refereed Designation:
Date Published:
1/2/2016