Coherent Structures in Jet Turbulence and Noise

Experimental results of pressure cross-spectra in model jets indicate that large-scale coherent structures do persist at higher Mach numbers up to 0.8 in the relevant range of Strouhat numbers between 0.1 and 2.0. If the pressure field is Fourier-analy zed circumferentially, the lower-order components are seen to dominate. This, along with the high acoustic efficiency of these components, suggests a numerical calculation procedure for the radiated far-field, which is based on Lighthill's wave equation approach with a linearized pressure source function, strongly weighted by axial and radial interference functions.

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