Mixing enhancement by and noise characteristics of streamwise vortices in air jet

Streamwise vortices are generated in the exit of a Mach-0.6 rectangular air jet by half-delta wings at various angles of attack. They entrain close to 50% more mass by 3.7 jet diameters and reduce the downstream jet noise at 23 diameters away from the jet nozzle by up to 3 dB. The mixing improvement and jet noise characteristics are both strong functions of the strength and relative position of the vortices. Mass entrainment measurements were measured quantitatively with local pitot-static pressure measurements and through image analysis. The image analysis also gave average spatial information about the mass entrainment through scalar transport

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