SUPERSONIC JET NOISE REDUCTION USING FLUIDICS, MECHANICAL CHEVRONS AND FLUIDICALLY ENHANCED CHEVRONS

This paper presents observations and simulations of the impact of several technologies on modifying the flow field and acoustic emissions from supersonic jets from nozzles typical of those used on military aircraft. The flowfield is measured experimentally by shadowgraph and particle image velocimetry (Pry). The acoustics are characterized by near and far-field microphone measurements. The flow and near-field pressures are simulated by monotonically integrated large-eddy simulation (MILES). Use of unstructured grids allows accurate modeling of the nozzle geometry. The nozzle geometries used in this research are representative of practical engine nozzles. The emphasis of the work is on "off-design" or non-ideally expanded flow conditions. The technologies applied to these nozzles include chevrons, fluidic injection and fluidically enhanced chevrons. The fluidic injection geometry and fluidic enhancement geometry follow the approach found successful for subsonic jets by Alkislar, Krothapalli & Butler [1] employing jets pitched 60 degrees into the flow, impinging on the shear layer just past the tips of the chevrons, or in the same axial position when injection is without chevrons.