ME-BEAR Seminar Presents Dr. Charles E. Tinney

"Cumulative nonlinear distortion of acoustic waves produced by high-speed jet flows"

In supersonic jets, an extended line of distributed sources act in compliance to generate and propagate noise in a complex manner to an observer far away from the jet. Nonlinear distortion of the acoustic waveform is often considered a prerequisite to understanding this propagation process. This is driven by one's capture of 'shock-type' structures or so called 'N-wave' type signatures in the pressure waveform, which are generally attributed to nonlinear wave steepening. Likewise, imperfect collapse of the spectra between an observer signal and a prediction, formed from a linear rescaling of the closer signal (using 1/r2 dependence), is also believed to be caused by nonlinear distortion. Unfortunately, these observations are most often made using measurements acquired in a range-restricted environment where changes to the waveform, due to cumulative nonlinear distortion, are too small to be accurately quantified, and/or without prior knowledge of the sound propagation path. The current work aims to fill this gap by exploring the acoustic field produced by an unheated, perfectly expanded, Mach 3 jet in a laboratory-scale environment. This talk focuses on a time-averaged approach to understanding the degree of non-linearity in the acoustic waveform at several far-field observer positions. Various "off-the-shelf" indicators are explored including a new model for predicting the presence (or lack there of) of cumulative non-linear waveform distortions in the signal.

BIOGRAPHICAL SKETCH
Dr. Tinney is an Assistant Professor in the Aerospace Engineering and Engineering Mechanics Department at the University of Texas at Austin. He has concentrated interests in designing novel experiments capable of fostering the development of low-dimensional and dynamical system models of turbulent flows. Dr. Tinney's background has covered a broad spectrum of research initiatives including airfoil separation and control, subsonic and supersonic jet noise, vortex dynamics, turbulent boundary layer flows and shock wave boundary layer interaction. He joined the Cockrell School of Engineering in the Fall of 2008 after serving as a Visiting Assistant Professor at the University of Florida and spending over two years at the Laboratoire d'Etudes Aerodynamique as a post-doctoral fellow with the Centre National de la Recherche Scientifique. He is a senior member of the American Institute of Aeronautics and Astronautics and a member of the American Physical Society and American Helicopter Society.