Due to steadily-increasing pressure from the public and from air-traffic regulators, aircraft and engine manufacturers are aggressively researching methods for reducing the level of noise of aircraft during landing and take-off. Generally, exhaust noise reduction is achieved by mixing the high-speed exhaust stream with the lower-speed bypass stream exiting the engine. A lobed mixer enhances this mixing (thereby reducing the noise) by shaping the circular exhaust nozzle with axisymmetric lobed protuberances, referred to as a “lobed mixer”. Through a series of high-fidelity computational simulations and experiments, we identify the instabilities present in the flow and how their mutual interaction enhances the mixing process. The results are novel and represent a significant step forwards in understanding the fundamental processes occurring in a lobed mixer.
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