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 22 for “"flow instability"”.
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Gas lift optimization and flow instability
… method can be affected by two-phase (gas-liquid) flow instability within the production tubing, which results in a reduction in the total oil recovered. There are three main flow instabilities caused by, the density wave oscillation, the casing heading pressure and the flow perturbation within the …
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Ventilation, stratification and flow instability driven by vertically distributed buoyancy sources
… thesis consists of three different projects on flows driven by vertically distributed buoyancy sources. Following a storyline, the three serial problems have inherent connections. In the first project, a theoretical model is developed for the steady multi-layered flow induced by a plane …
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A study of defect formation due to flow instability during mold filling in lost foam casting
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
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Fluids Viscosity Effect on Non-Isothermal Buoyancy-Driven Exchange Flow in Inclined Pipes
Buoyancy-driven exchange flow is studied experimentally for different Atwood numbers, inclination angles and fluid pairs. The density difference drives the flow, that is achieved through added salinity for isothermal case and temperature difference for the non-isothermal case. Detailed benchmarking …
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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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Makassar Strait Intraseasonal Variability
… Strait, the primary pathway for Pacific water flow into the Indian Ocean and a waveguide for transmitting subinertial energy from the tropical Indian Ocean to Indonesian seas, is investigated, using the 2004-2006 International Nusantara Stratification and Transport (INSTANT) observations. The …
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Near-wall turbulence in the transitionally rough regime
… model how roughness increases drag in turbulent flows. This work focuses on the transitionally rough regime, where roughness is large enough to have an impact on drag but the rough regime is not fully developed. By restricting ourselves to this regime, we can investigate the changes produced in …
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Shape Optimisation for Hydrodynamic Stability and its Application to Cyclone Separators
… applications it is desirable to have a steady flow field that is stable to perturbations. This can be described through a global stability analysis. This is an eigenvalue problem which gives a series of mode shapes (the eigenfunctions) and their growth rates and frequencies (the eigenvalues). …
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Thermal hydraulic limits analysis for the MIT Research Reactor low enrichment uranium core conversion using statistical propagation of parametric uncertainties
… temperature of 60 'C, and primary coolant flow rate of 1800 gpm, compared to 8.3 MW obtained from the analytical method using the EHCFs with same operating conditions. The same methodology was also used to calculate the safety limit (SL) to ensure that adequate safety margin exists between …
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Numerical Investigation of Tonal Noise on a Transitional Airfoil under Varying Conditions
… <p>Our results indicate that the growth of instability waves in the flow-separation region is a necessary condition for the generation of tones, but the selected tonal frequencies are governed not only by vortex shedding, but also through a feed-back loop that is determined, in addition to …
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Remote Detection of Surging Glaciers Across High Mountain Asia
… the idea that surging occurs along a spectrum of flow instability, validating earlier surge studies. The synoptic nature of this study provides a degree of representation of the surge phenomenon not attainable by smaller-scale studies. The results highlight the necessity to update the RGI, and the …
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Rheological properties, stochastic characteristics, and second law violations of atomic fluids in Couette flow
… theories adapted to atomic fluids such as flow stability. Building on these models, we aim to understand the transitions to turbulence and flow instability in atomic fluids. Via the Poincaré inequality, we generalize a classical continuum methodology to atomic fluids and obtain a fluid …
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Transition between Flow Regimes in Porous Media Using Magnetic Resonance Velocimetry: From Laminar to Turbulent
… to investigate the transition between different flow regimes in porous media. The complete transition spectrum of single-phase flow, from creeping flow to inertial, unsteady laminar, and turbulent flow regimes, was examined in sphere packings. Further understanding of the fundamental fluid …
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Flow-Mediated Interaction Between a Vibrating and an Elastically-Mounted Cylinder
… the solid-solid contact does not occur. The flows corresponding to regimes A, A*, C, E, F and G as classified by Tatsuno and Bearman (1990) are investigated. In all these regimes, harmonic frequency components in the response of the passive cylinder are found to persist in all regimes, …
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On vortex rings impacting a sharply-stratified interface
… and modelling techniques to understand the flow instability and subsequent mixing induced by the impinging vortex ring. Our findings demonstrate that there exists a critical Richardson number, corresponding to a mixing transition, beyond which the mixing efficiency is constant. Using a novel …
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Dynamically induced uncertainty in stratified turbulent mixing models
… in a wide range of environmental and industrial flows. On both global and regional scales in the ocean, it is necessary to model small-scale turbulent processes and the way in which they enhance mixing in order to form an accurate picture of the vertical transport of heat, nutrients and …
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Numerical lnvestigation of Disturbance Environments in Low Pressure Turbines
… transition is simulated for the vortex-induced instability. The effect of the convection speed and strength of the vortex are discussed and the paths of transition adopted are distinguished. At low disturbance levels, the transition to turbulence is primarily due to the breakdown of …
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Linking Rheological and Processing Behavior to Molecular Structure in Sparsely-Branched Polyethylenes Using Constitutive Relationships
… using the Pom-pom constitutive relationship. A flow instability known as ductile failure in extensional flow required the development a novel technique known as encapsulation in order to carry out shear-free rheological characterization. Ductile failure prevents the rheological measurement of …
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Aplicaciones de la hidrodinámica suavizada de las partículas al estudio de fenómenos hidráulicos
… with special attention to free-surface turbulent flow and different theoretical formulations of the turbulent closure. Then, SPH method basis are described. As well Navier-Stockes and turbulent closure equations are showed in SPH form. The methodology following to validate the model is presented …
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