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 26 for “"hydrodynamic instability"”.
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A-C magneto hydrodynamic instability.
Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
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Hydrodynamic Instability of Fluid Flow Through Homogeneous Porous Media
To examine mechanisms for the production of large-amplitude, steady disturbances at elevated Reynolds number, the effective porosity of the medium is reconsidered. Experimental results and detailed microscale flow simulations indicate that significant regions of flow separation exist around and …
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Nonlinear hydrodynamic instability and turbulence in eccentric astrophysical discs
The nonlinear evolution of the parametric instability of inertial waves inherent to eccentric discs is studied by way of a new local numerical model. Mode coupling of tidal deformation with the disc eccentricity is known to produce exponentially growing eccentricities at mean-motion resonances, …
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Mixing with complex patterns : from the impact of miscible viscous fingering to the effects of motile bacteria
… are commonplace. Viscous fingering is a hydrodynamic instability that occurs when a less viscous fluid displaces a more viscous one. Instead of progressing as a uniform front, the displacing fluid forms fingers that vary in size and shape to form complex patterns. The interface created …
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Global stability and control of swirling jets and flames
… structures that arise due to self-sustained hydrodynamic oscillations, also known as global hydrodynamic instability. Direct numerical simulation (DNS) of the Navier--Stokes equations in the low Mach number limit is used to obtain a steady base flow, and the most unstable direct and adjoint …
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Macro-scale investigation of high speed gas bearings for MEMS devices
… is introduced along with the traditional hydrodynamic regime. The new hybrid mode is exploited to implement a novel in-situ rotor balancing scheme which enables hydrodynamic operation. Analysis for both modes of operation is presented along with experimental results. A high-order, …
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Coupling Computationally Expensive Radiative Hydrodynamic Simulations with Machine Learning for Graded Inner Shell Design Optimization in Double Shell Capsules
… physics simulations, such as in the radiation-hydrodynamics code xRAGE, are computationally expensive, limiting the design process and ability to find an optimal design. Machine learning provides a mechanism to leverage expensive simulation data and alleviate limitations on computational time …
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Bosonic Quantum Hall States from Rapidly Rotating Bose-Einstein Condensates
… where there are not distinct flat bands, the hydrodynamic instability of the condensate to a patterned density distribution is observed. Microscopically, the instability to pattern formation results from the synthetic magnetic field induced minimum in the collective excitation spectrum …
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Understanding the evolution of miscible viscous fingering patterns
Viscous fingering, the hydrodynamic instability that occurs when a lower viscosity fluid displaces a higher viscosity fluid, creates complex patterns in porous media flows. Fundamental facets of the displacement process, such as volumetric sweep and mixing efficiency, depend strongly on the type of …
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Instabilities of an eastern boundary current with and without large-scale flow influence
Eastern oceanic boundary currents are subject to hydrodynamic instability, generate small scale features that are visible in satellite images and may radiate westward into the interior, where they can be modified by the large-scale circulations. This thesis studies the stability of an eastern …
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Flow through porous media : from mixing of fluids to triggering of earthquakes
… We show that miscible viscous fingering-the hydrodynamic instability that arises when a less viscous fluid displaces the more viscous one-can be employed as an agent for enhanced mixing in porous media flows. Based on results from high-resolution numerical simulations, we derive a macroscopic …
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Instabilities of an eastern boundary current with and without Large-scale Flow Influence
Eastern oceanic boundary currents are subject to hydrodynamic instability, generate small scale features that are visible in satellite images and may radiate westward into the interior, where they can be modified by the large-scale circulations. This thesis studies the stability of an eastern …
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On the stability of plane viscoelastic shear flows in the limit of infinite Weissenberg and Reynolds numbers
Elastic effects on the hydrodynamic instability of inviscid parallel shear flows are investigated through a linear stability analysis. We focus on the upper convected Maxwell model in the limit of infinite Weissenberg and Reynolds numbers. Specifically, we study the effects of elasticity on the …
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Instability of Oscillatory Flow in Ducts and Applications to Solid -Propellant Rocket Aeroacoustics
… as a mechanism of high-amplitude acoustic instability in solid propellant rockets, wherein finite amplitude acoustic motions can produce near-surface turbulence and lead to an enhanced propellant burning rate that couples with the chamber acoustics. Prediction of the threshold acoustic …
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Pharmaceutical crystallization design using micromixers, multiphase flow, and controlled dynamic operations
… combined with an air flow to induce a multiphase hydrodynamic instability that spontaneously generates slugs where the crystals continue to grow. These slugs are well-mixed without having the mixing blades in traditional crystallizer designs that induce undesirable uncontrolled crystallization …
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Sediment Heterogeneity and Sand Production in Gas Hydrate Extraction: Daini-Atsumi Knoll, Nankai Trough, Japan
… thought to be the result of mechanical and hydrodynamic instability, however it appears the failure mechanism is not the same for all reservoirs and the location of reservoir porosity and pressure on the normal compression line for sands could be a controlling factor. Sand production in …
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Multiphase flow in porous media with phase transitions : from CO₂ sequestration to gas hydrate systems
… role that chemical speciation plays in this hydrodynamics-reaction coupled process. We then study hydrodynamic and thermodynamic processes pertaining to a gas hydrate system under changing temperature and pressure conditions. The framework for our analysis is that of phase-field modeling of …
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Control configured design for smooth, highly-maneuverable, underwater vehicles
… Planar control is complicated by the presence of hydrodynamic instability. A dynamic control system that augments stability and achieves high maneuverability is outlined and implemented. A nonlinear hydrodynamic model is formulated, and its linearized dynamics are analyzed to attain insights into …
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Theoretical and Computational Analyses on Transition and Turbulence in Purely Oscillating Pipe Flow
<p>The hydrodynamic instability of purely oscillating pipe flows is investigated in terms of the quasi-steady formulation assuming the temporal changes of the laminar base flow relative to disturbances are slow. A simple model equation is introduced to compare the exact solution of the current …
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Hydrodynamic stability of a premixed flame subjected to transverse shear
… of engineering devices. The primary intrinsic instability of premixed combustion is caused by thermal gas-expansion, known as the hydrodynamic or the Darrieus-Landau (DL) instability. Consequently, a premixed flame is susceptible to disturbances. The flame tends to develop a wrinkled or …
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