Linear analysis of jet-engine core noise using a hybrid modeling approach

As further reductions in aircraft engine noise are realized, the relative importance of reducing engine core noise increases. In this work, a representative engine flow path is studied to examine the mechanisms by which direct and indirect core noise propagate through the engine and affect the farfield noise emerging from the exhaust. The flowpath consists of a model gas turbine combustor, a single-stage turbine, a converging nozzle, a near field jet, and far-field acoustic radiation. A combination of high-fidelity and low-order simulation techniques are used to represent the development and propagation of disturbances through the flowpath. Particular detail is provided for a direct noise calculation of the combustion chamber, as well as an LES calculation of the nozzle and its associated near-field jet. A simple one-way coupling procedure is employed for propagating disturbances from one stage of the calculation to the next, and early results showing the increase in farfield jet noise due to upstream core noise effects are presented. Future work will include higher fidelity representations of the turbine stage, a more refined approach to the coupling procedure, and attempts to distinguish the effects of direct and indirect core noise on the farfield acoustic radiation.