A robust numerical approach for the prediction of turbofan engine noise

Abstract

Noise from aircraft jet engines remains a dominant sound source in takeoff conditions. Government regulations and community noise criteria are getting more stringent, creating significant challenges for aircraft manufacturers to meet noise requirements. The increased costs of experimental studies as well as access to powerful computers have given new motivation for computational studies. In this paper, an efficient and robust numerical scheme, namely the Lattice Boltzmann Method, was used to simulate the sound created by typical internal mixing nozzles with forced mixers. The simulation captured the time-resolved flow characteristics and large scale turbulent structures. The sub grid scales were modeled using the renormalization group (RNG) forms of the k-ε equations. Two cold flow test cases, conducted by NASA, were selected for computational setup and validation purposes. The far field sound was predicted using a surface integral method. The Near-field simulation results such as the internal velocity profiles as well as far-field sound were qualitatively in agreement with experimental results. The far-field sound analysis suggested significant low-frequency noise reduction for the lobed mixers, as well as significant reduction in overall sound pressure levels (OASPL) in comparison with the confluent nozzle configurations.