Study of High-speed Subsonic Jets using Proper Orthogonal Decomposition
type: CreativeWork
description: The primary objective of this thesis is to advance Proper Orthogonal Decomposition (POD) methods to quantify similarities and differences between the turbulent structures in the mixing layer of transonic jets issued through baseline axisymmetric conical nozzle and ones with chevrons. The analysis is done using flow velocity data obtained through Particle Image Velocimetry (PIV). Two chevron nozzles with penetration levels at 2% and 4% are used. The mean velocity and TKE results show that chevrons reduce the potential core length, increase the jet spread, increase TKE levels immediately after the nozzle exit, and reduce TKE levels downstream. POD is used to further quantify these results. First 35 converged POD modes are investigated since these modes comprise of the majority of the large scale structures. The similarities and differences between the POD modes from different data sets vary along the jet. The study of the POD modes along the jet showed the growth of the structures in both size and strength in the downstream direction. The growth rates of the modes are suppressed by the chevrons and high penetration chevrons are more effective. This trend is also noticed in the energy distribution study among the modes. Despite having both the axial and radial modes energized by the chevrons near the nozzle, the stabilization of the modes resulted in lower energy contents in the downstream regions. Projection of the PIV images from the chevron configurations onto the baseline POD modes showed that both near the nozzle and downstream the highest energy containing baseline modes are attenuated by the chevrons, but the radial modes in the near-nozzle region. A metric used in order to quantify the similarities among the mode shapes between different flow data sets showed that in the near nozzle region the correlation between the modes corresponding to the chevron nozzles and baseline nozzle is very low due to the increased mixing. Correlation increases as the flow moves do…
abstract: The primary objective of this thesis is to advance Proper Orthogonal Decomposition (POD) methods to quantify similarities and differences between the turbulent structures in the mixing layer of transonic jets issued through baseline axisymmetric conical nozzle and ones with chevrons. The analysis is done using flow velocity data obtained through Particle Image Velocimetry (PIV). Two chevron nozzles with penetration levels at 2% and 4% are used. The mean velocity and TKE results show that chevrons reduce the potential core length, increase the jet spread, increase TKE levels immediately after the nozzle exit, and reduce TKE levels downstream. POD is used to further quantify these results. First 35 converged POD modes are investigated since these modes comprise of the majority of the large scale structures. The similarities and differences between the POD modes from different data sets vary along the jet. The study of the POD modes along the jet showed the growth of the structures in both size and strength in the downstream direction. The growth rates of the modes are suppressed by the chevrons and high penetration chevrons are more effective. This trend is also noticed in the energy distribution study among the modes. Despite having both the axial and radial modes energized by the chevrons near the nozzle, the stabilization of the modes resulted in lower energy contents in the downstream regions. Projection of the PIV images from the chevron configurations onto the baseline POD modes showed that both near the nozzle and downstream the highest energy containing baseline modes are attenuated by the chevrons, but the radial modes in the near-nozzle region. A metric used in order to quantify the similarities among the mode shapes between different flow data sets showed that in the near nozzle region the correlation between the modes corresponding to the chevron nozzles and baseline nozzle is very low due to the increased mixing. Correlation increases as the flow moves do…
author: Malla, Bhupatindra
language: English
keywords: Aerospace Materials, Proper Orthogonal Decomposition, Jet Shear Layer, Turbulent Kinetic Energy, Coherent Structures, Transonic Jet, Jet Noise
date published: 2012
date modified: 2026-07-24T03:36:23Z
provider: OhioLINK
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cincinnati