Experimental investigations of aerodynamic and acoustic characteristics of by-pass jets issuing from nozzles with lobed mixers are carried out. It is shown that mixing chamber length variations affect substantially the flow parameters in the nozzle exit section and the acoustic characteristics of the near soundfield of the jet. In particular, it is found that at definite mixing chamber lengths a system of small-scale high-speed jets is realized in the nozzle exit section. These jets propagate in a cocurrent flow and this leads to jet mixing intensification and to jet noise reduction at low frequencies with noise level increase at high frequencies.
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