Global ETD Search
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 20 for “"Instability Mechanism"”.
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A low-frequency instability mechanism in a coaxial dump combustor
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982.
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Combustion Instability Mechanism of a Reacting Jet in Cross Flow at Gas Turbine Operating Conditions
… vibrations. This study focuses on identifying a mechanism of combustion instability of a reacting jet in cross flow, a flow feature that is widely used in the design of gas turbine combustion systems. Experimental results from a related study are used to validate and complement three numerical …
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Computer aided floating zone growth of Germanium-Silicon crystals in a resistance heated multi-zone furnace
… <br>zone could be qualitatively explained. The instability mechanism <br>of thermocapillary convection in a low Pr floating zone could be <br>attributed to the interaction of buoyancy convection and surface <br>flows. The direct numerical simulations were based on a full zone <br>model.
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InGaAs MOSFETs for logic and RF applications : reliability, scalability and transport studies
… MOSFET technology. First, it identifies a new instability mechanism in self-aligned InGaAs MOSFETs caused by fluorine migration and passivation of Si dopants in n-InAlAs. This problem is successfully mitigated by eliminating n-InAlAs from the device structure. The new device design achieves …
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Directional growth of wind generated waves
… of wave models, it uses a point spectral growth mechanism, i.e., it applies the energy balance equation in a directionally integrated form. The directionality of its growth is obtained from an assumed spreading function on the wind direction. In this study, the energy balance equation is applied …
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Numerical Study of the Stability of Embedded Supersonic Compressor Stages
… of the investigation was to determine the flow instability mechanism of the UEET compressor and its relation to the rotor shock structure in the relative velocity reference frame. The computational study was conducted with the NASA code ADPAC , utilizing the mixing-plane assumption for the …
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Large Eddy Simulation and Analysis of Shear Flows in Complex Geometries
… Kelvin-Helmholtz is identified as primary instability mechanism and observed as global mode at a specific parameter. Mechanism of global mode synchronization over distinct spatial location is studied. In the second part, the flow physics of film cooling flows is analysed. The origin, …
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The Effects of Variable Parameters on the Behavior of Initial Wind Waves
<p>The generation mechanism of short wind waves is generally thought to be a viscous instability at the air-sea interface. The short, regular waves arising from a sudden wind on a still water surface have a dispersion relation which is characteristic of gravity-capillary waves. The effects of …
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Developmental models with cell surface receptor densities defining morphological position
… with ordinary differential equations. Two mechanisms of pattern formation: diffusion driven instability and hysteresis-driven mechanism are studied and their possibilities and constraints in explanation of different aspects of pattern formation and regulation are demonstrated. …
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Generalized Navier-Stokes equations for active turbulence
… accounting for active stresses through a linear instability mechanism, in contrast to externally driven classical turbulence. This minimal model can reproduce experimentally observed velocity statistics and is analytically tractable in planar and curved geometry. Exact stationary bulk solutions …
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Numerical studies of the flow around an airfoil at low Reynolds number
… flow field is performed, however no absolute instability is observed that could explain the presence of self sustaining turbulence. A series of simplified DNS are presented that illustrate a three-dimensional in-stability of the two-dimensional vortex shedding that occurs naturally. The …
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Large eddy simulation of turbulent vortices and mixing layers
… in a very complex flow field. The inflectional instability mechanism of the axial velocity deficit amplifies the initial disturbances and results in the generation of large-scale turbulent structures. These structures appear as branches sprouting out of the vortex core. The breakdown of these …
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Modeling wind forcing in phase resolving simulation of nonlinear wind waves
… spectral components of the wave field. The mechanism of wind forcing is assumed to be primarily form drag acting on the surface through wave-induced distribution of normal stress. The mechanism is parameterized in terms of wave age and its magnitude is adjusted by the observed growth rates. …
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Triadic Resonance Instability in finite-width internal gravity wave beams
… wave beam becoming unstable to Triadic Resonance Instability (TRI). To date, most theoretical work examines the instability in the context of monochromatic plane waves. In the ocean, however, waves seldom take this form, rather they manifest as beams that span the wavenumber spectra. With an aim …
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Effect of suction and cooling on the stability of subsonic and supersonic boundary layers
… show that, whereas cooling decreases the viscous instability, it increases the shear-layer instability and hence it increases the growth rates in the separation region. The coexistence of more than one instability mechanism makes a certain degree of wall cooling most effective. For the Mach …
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Numerical modelling of low temperature plasma
… Three different situations are investigated: an instability in electronegative plasmas; electron avalanches during plasma initiation; and a phenomenon called the Critical Ionisation Velocity interaction. Industrial plasma discharges with electronegative gases are found to be unstable in certain …
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Investigation of Threshold Voltage Instability in Normally Off GaN on Si HEMT
… transition layers. However, threshold voltage instability exists as a key reliability issue which is not well understood. In this thesis, we investigate on threshold voltage instability of normally off 600-650V p-GaN AlGaN/GaN on Si HEMT. This thesis aims to advance the physical understanding …
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Parametric subharmonic instability of internal gravity wave beams
… In this context, it is of interest to understand mechanisms by which internal wave beams become unstable and eventually breakdown, thereby contributing to mixing. A possible instability mechanism is via resonant triad interactions that amplify short-scale perturbations with frequency equal to one …
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Phenomena, mechanism, and prediction of flashing instability investigated by experiments, analytical modeling, and numerical simulation
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-12-04 without embargo terms
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Observations of turbulence, internal waves and background flows : an inquiry into the relationships between scales of motion
… held to result from the occurrence of shear instability in regions where the Richardson number is locally supercritical (i.e. Ri ≤ 1/4), permitting the growth of small-scale waves which break and result in turbulent mixing. The occurrence of shear instability results from the local …