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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 37 for “"supersonic jet"”.
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The reduction of supersonic jet noise using pulsed microjet injection
… thesis is concerned with the active control of supersonic jet noise using pulsed microjet injection at the nozzle exit. Experimental investigations were carried out using this control method on an ideally expanded Mach 1.8 jet operating at 900, 1300 and 1700'F. Six Bosch fuel injectors were …
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Aeroacoustics of Supersonic Jet Interacting with Solid Surfaces and its Suppression
<p>The noise generated by supersonic jet is of primary interest in the high-speed flight. In several flight conditions jet exhaust of the propulsion system interacts with solid surfaces. For example, jet impingement on ground for a rocket lift-off, or interactions influenced by the integration of …
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Coalescence of nonlinear acoustic waves, with application to supersonic jet noise
… and crackle close to a lab-scale, Mach 3 jet flow in prior studies, which contradicted theoretical predictions for that jet. A numerical model based on the Khokhlov–Zabolotskaya–Kuznetsov (KZK) nonlinear wave equation is developed to demonstrate that coalescence leads to increased waveform …
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Investigating the Structures of Turbulence in a Multi-stream, Rectangular, Supersonic Jet
<p>Supersonic flight has become a standard for military aircraft, and is being seriously reconsidered for commercial applications. Engine technologies, enabling increased mission capabilities and vehicle performance, have evolved nozzles into complex geometries with intricate flow features. These …
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Supersonic jet spectroscopy of synthetic foldamers, multichromophores, and their water containing clusters
… are possible through the utilization of a supersonic jet expansion to collisionally cool molecules into their vibrational zero-point levels, collapsing the distribution of conformational isomers to the lowest-energy minima on the potential energy surface. This collisional cooling afforded …
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Stability, LES, and Resolvent Analysis of Thermally Non-uniform Supersonic Jet Noise
… investigates noise generation and dispersion in supersonic jets and focuses on the fluid-dynamic regime typical of high-performance turbojet and turbofan engines. The goal of my research is to understand how dispersion and propagation of wavepackets can be modified by noise reduction strategies …
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The Linearized Euler Equations for Predicting Supersonic Jet Noise of a Rectangular Jet Using OpenFOAM
… utilized to predict the acoustics of a heated supersonic rectangular jet. The rectangular jet (RJET) results were compared against experimental data.</p> <p>The results from this work show that OpenFOAM can be used as an effective platform to develop CAA specific solvers. The leeFoam solver …
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Modern Methods in Machine Learning as Applied to the Study of a Complex Supersonic Jet Flow
… stealth performance. The associated turbulent jet physics and the aeroacoustic phenomena have been studied thoroughly over the past 80 years; however, the complex non-linear interactions between multiple merging canonical flows are not well understood. In this study, we seek to gain a better …
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Development of Automatic CFD Grid Generation for the Design of the Preliminary Wing Sweep Schedule for the Gulfstream Quiet Supersonic Jet
… wing sweep schedule for the Gulfstream Quiet Supersonic Jet (wing and body) was investigated using CFD analysis methods. The use of automating the gridding procedure allowed for numerous cases to be investigated. The examination of the drag polar for different Mach cases indicated the optimum …
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Turbulence Statistics and Eddy Convection in Heated Supersonic Jets
Supersonic hot jet noise causes significant hearing impairment to the military workforce and results in substantial cost for medical care and treatment. Detailed insight into the turbulence structure of high-speed jets is central to understanding and controlling jet noise. For this purpose a new …
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Asymmetries in extragalactic radio sources
… dimensional hydrodynamics of extragalactic radio jets. This entailed putting together a large number of numerical tools before such simulations could be performed. The thesis was structured to be a set of papers, each addressing a computational or astrophysical issue that was important in …
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The Effect of Thermal Non-Uniformity on Coherent Structures in Supersonic Free Jets
Supersonic jet exhaust plumes produce noise in jet engines, which has been a problem in the aerospace field. Researchers are working on ways to reduce this turbulent mixing noise, with little modification to the engine and nozzle. Prior work has shown that total temperature non-uniformity is a …
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Development of Specialized Laser Doppler Velocimeters for High Resolution Flow Profile and Turbulence Spectral Measurements
… motion and evolution of coherent structures in supersonic jet flows and how that relates to the intense noise the flows generate. As a preliminary study to experimentally address these relationships, novel non-intrusive measurements using two-component laser Doppler velocimetry (LDV) have been …
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Assessment of Turbulence Modelling for Compressibility Effects in Ejector Ramjet Applications
… compressibility effects for a confined supersonic jet, a key component of the Atlantis Intake System ejector ramjet. The third-party OpenFOAM compressible flow solver, pimpleCentralFOAM, is used to simulate a Mach 1.25 axisymmetric jet discharging inside a mixing tube and is compared …
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Active noise control in supersonic impinging jets using pulsed microjets : actuator design, reduced-order modeling
… years, it has been demonstrated that direct microjet injection into the shear layer of the main jet disrupts the feedback loop inherent in high speed impinging jet flows, thereby significantly reduces the adverse effects. The amount of noise reduced by microjet actuation is known to be dependent …
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A Preliminary Study of Acoustic Prediction Technology Based on Detached Eddy Simulations for Supersonic Jets Impinging on Flat Plates
… of an existing industry tool to study supersonic jets impinging on at plates is shown. This industry tool is the commercially available CFD package ANSYS FLUENT. The supersonic jet studied is perfectly expanded with a Mach number of 1.5, and it impinges on a flat surface 4 nozzle throat …
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Spatiotemporally-Resolved Velocimetry for the Study of Large-Scale Turbulence in Supersonic Jets
The noise emitted from tactical supersonic aircraft presents a dangerous risk of noise-induced hearing loss for personnel who work near these jets. Although jet noise has many interacting features, large-scale turbulent structures are believed to dominate the noise produced by heated supersonic …
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Intersystem crossing in acetylene : a mechanistic study
… states were studied using a second-generation, supersonic jet molecular beam machine with a multispectral capability. Surface Electron Ejection (SEELEM), Ultraviolet Laser Induced Fluorescence (UV-LIF), and Infrared Laser Induced Fluorescence (IR-LIF) spectra were acquired simultaneously …
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TIME-CONSERVATIVE FINITE-VOLUME METHOD WITH LARGE-EDDY SIMULATION FOR COMPUTATIONAL AEROACOUSTICS
… the broadband shock-associated noise of a planar supersonic jet. The second-order time-conservative finite-volume method can solve practically relevant aeroacoustic problems with high-fidelity which is an exception to the conventional second-order schemes commonly regarded as inadequate for …
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Quantification of the Depth-of-Field in a Self-Aligned Focusing Schlieren System
… schlieren imaging is applied to an overexpanded supersonic jet to demonstrate how schlieren image intensity can be related to ray displacement, angular deflection, refractive index gradient, and density. The reconstructed mean density fields capture the expected shock-cell structure and agree …
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