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 21 for “"periodic flow"”.
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A time-spectral hybridizable discontinuous Galerkin method for periodic flow problems
Numerical simulations of time-periodic flows are an essential design tool for a wide range of engineered systems, including jet engines, wind turbines and flapping wings. Conventional solvers for time-periodic flows are limited in accuracy and efficiency by the low-order Finite Volume and …
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An Experimental Investigation of Thermal Boundary Layer Structure and Heat Transfer in Oscillating Flows Using CARS Spectroscopy and Cold -Wire Anemometry
… of a thermal boundary layer in the oscillating flow. The cold-wire technique provides for increased data acquisition rates relative to CARS, at the expense of an ambiguous, systematic error associated with the intrusive nature of the probe. The cold-wire technique is used to investigate …
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An experimental study of unsteady separation in a two-dimensional flow
An experimental study of flow separation in an incompressible two-dimensional unsteady flow was undertaken with the aim of validating recently developed flow separation criteria, which are based on kinematic principles. Specifically, the so-called rotor-oscillator arrangement was utilized to …
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Resposta dinâmica e estabilidade de tubos com escoamento interno
… quotient is used to study the influence of flow velocity on the eigenvalues behaviour, and theoretical estimates for the stability of the equilibrium position are obtained. It is shown that, for a periodic flow velocity, parametric resonance occurs and the boundaries of these instability …
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Investigation of velocity gradient as driving force of flow pulsation in fuel assemblies
The presence of quasi-periodic flow pulsations in fuel assemblies has been observed since the 1960's but is still not fully understood. Current design and licensing practices for nuclear reactor fuel mostly rely on 1-dimensional subchannel simulation tools, which might not accurately predict the …
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Chaos Control of an Open Shear Flow: A Novel Control Strategy and its Experimental Demonstration in an Axisymmetric Jet
… jet, housed in a low-noise anechoic chamber. Periodic flow states involving various sequences of vortex ring formation and their pairings were achieved using open-loop and closed-loop control. In contrast to conventional, linear, control approaches that use brute-force high-amplitude …
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Conceptual Design and Instrumentation Study for a 2-D, Linear, Wet Steam Turbine Cascade Facility
… and the challenges associated with achieving periodic flow in this facility are investigated.
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Accumulation of Lead by Biofilms in Drinking Water Distribution Systems
… lead source pipe and various pipe materials with periodic flow and stagnation conditions of a typical household to create, characterize, and determine lead accumulation capabilities of biofilms within the water pipes. Biofilms developed in all pipe materials with an overall range of 1.44×103 to …
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Exploring and Envisioning Periodic Laminar Flow Around a Cylinder
It is well known that for small Reynolds numbers, flow around a cylinder is laminar and stable. For larger Reynolds numbers, although the flow regime remains laminar, the formation of complex periodic structures appear downstream. The cyclic nature of this periodic flow is well characterized by the …
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Advancing Exhaust Flow Uniformity, Operational Stability, and Total Pressure Gain of Rotating Detonation Engines for Successful Turbine Integration
… a shock-laden, highly unsteady exhaust flow field that differs substantially from steady, subsonic flow required at the turbine inlet.This dissertation aims to develop novel RDC designs with tailored inlet and exit geometries for successful turbine integration. Firstly, RDC exit was …
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The Acoustics of Cerebral Aneurysms
… geometry, we identify that self-excited flow oscillations can generate sound at a distinct frequency. Periodic flow fluctuations have been observed in aneurysms by various studies. However, the potential of flow oscillations to cause aneurysm wall vibrations (hence sound) had not yet been …
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An analytical and experimental investigation of the hydraulic transport of high concentration mixed regime slurries
… The inputs to the model are mean mixture flow rate, delivered. concentration and the particle and pipeline characteristics.. In order to calculate in situ concentration, the concentration distribution is found by using a diffusion model. A logarithmic velocity distribution is also required …
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Modal Response of a Transonic Fan Blade to Periodic Inlet Pressure Distortion
… in gas turbine engines when the incoming airflow is partially blocked or disturbed. Distorted inlet conditions can have varying effects on engine performance and engine life. Short-term effects are often in the form of performance degradation where the distorted airflow causes a loss in …
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Numerical Investigation of the Wake of a Rectangular Wing
… In the near wake of a rectangular wing the flow field consists of a spiraling wake that winds around a pair of vortex cores. The study of the turbulence structure and life of wing tip vortices is of great importance to air traffic control in congested airports. In this dissertation a …
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Investigation et modélisation des tensions circonférentielles en simulation méridienne
… turbomachines. That explains why throughflow simulation is still widely used at industrial scale. The main limitation of throughflow is however the need for empirical models to reproduce blade-flow interactions and major 3D flow features. As an alternative, Adamczyk (1984) proposed three …
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Studies on secondary instabilities
… in understanding early stages of transitional flows have been achieved by studying secondary instabilities in selected prototype flows. These secondary instabilities can be modeled as parametric instabilities of the nearly periodic flow that consists of the prototype velocity profile and a …
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Unsteady Turbulence Interaction in a Tip Leakage Flow Downstream of a Simulated Axial Compressor Rotor
The unsteady behavior of a tip leakage flow downstream of a simulated axial compressor rotor has been studied. The Virginia Tech low speed linear cascade wind tunnel was adapted to model the unsteady tip leakage flow produced by a rotor operating in the vortical wakes of a set of stator vanes. The …
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Numerical, field and laboratory studies of three-dimensional flow structures at river channel confluences
… controls on and the nature of three-dimensional flow structures at river channel confluences. Previous work has shown that junction angle is an important control on the flow patterns at channel junctions since it affects the degree of curvature of flow from each tributary and sets up secondary …
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An Experimental Investigation of Unsteady Surface Pressure on Single and Multiple Airfoils
… surface pressure on airfoils encountering flow disturbances. Analysis of measurements made on an airfoil immersed in turbulence and comparisons with inviscid theory are presented with the goal of determining the effect of angle of attack on an airfoils inviscid response. Unsteady …
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Modeling of three-dimensional viscoelastic flows with free surfaces using a finite element method
… isothermal, incompressible, creeping flow of a Giesekus fluid with free surfaces at infinite capillary number. The code is an extension of the parallel methods developed by Caola et al. from two- to three-dimensional flows, a restructured and improved version of the three-dimensional …
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