Seminar: Modeling of Noise Reduction in Multistream Jets

Engine architectures for future subsonic and supersonic aircraft include multistream, three-dimensional exhaust nozzles.  Reshaping of the outer streams can lead to significant noise reduction in particular azimuthal directions.  This motivates the development of predictive tools that can assess the impact of such nozzle configurations on jet noise, with fast turnaround time and moderate computational cost.   The seminar will discuss the development of Reynolds-Averaged Navier-Stokes (RANS)-based methods for the modeling of noise reduction in three-stream jets featuring asymmetric nozzles for the tertiary (outer) stream.  The connection between the acoustic and RANS fields is made through a Lighthill-based acoustic analogy, with emphasis on the sound emitted by large-scale turbulent structures.  Of special interest is the modeling of the space-time correlation so that the azimuthal directivity of the emitted sound can be reproduced.   Preliminary comparisons between the modeled and experimental jet noise spectra will be presented.

About the Speaker

Dimitri Papamoschou is a professor of mechanical and aerospace engineering in the Henry Samueli School of Engineering, University of California, Irvine. He received his Ph.D. in aeronautics from the California Institute of Technology in 1987 and joined UC Irvine in 1988. His doctoral thesis work illuminated the effect of compressibility on the turbulent shear layer growth rate under a variety of freestream conditions. At UC Irvine, he continued to investigate compressible turbulent flows, with impacts on high-speed mixing and noise generation. In the mid-1990s, he became involved in jet aeroacoustics, building unique multistream facilities for the study of jet noise. He showed the potential for noise reduction by asymmetric distortion of the jet velocity field, a concept that has led to several patents and investigations at NASA and industry. Dr. Papamoschou has also investigated flow instabilities arising from shock-induced inside nozzles, a phenomenon with mixing-enhancement applications. Additional research interests include advanced microphone phased-array implementations for detection and modeling of jet noise sources and shielding of jet noise from aircraft surfaces. He served as department chair, associate dean, and interim dean in the Henry Samueli School of Engineering.  He is a Fellow of the AIAA and serves as an associate editor for the AIAA Journal.

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