The aeroacoustic characteristics of an over-expanded annular aerospike nozzle have been studied. The overall sound pressure levels of the aerospike nozzle are compared with the levels obtained from a convergent divergent nozzle for a given pressure ratio of 2.57 for the over-expanded condition. It is observed that the over-expanded annular aerospike nozzle generates screech tones at this NPR and in general shows higher OASPL levels than the over-expanded convergent-divergent nozzle at peak

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... tion direction. Nomenclature θ = Polar angle relative to the jet inlet axis P a = ambient Pressure, 13.27psi P o = Stagnation Pressure P ref = Reference pressure for SPL (=20µ Pascal) NPR = Nozzle Pressure Ratio, (P o /P a ) T a = Ambient Temperature, 293K OASPL = Overall Sound Pressure Level, dB