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 35 for “"Flow Reversal"”.
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Flow Reversal Events Increase the Abundance of Nontroglobitic Fish in the Subterranean Rivers of Mammoth Cave National Park, Kentucky
… to be significantly higher following high water flow reversal events indicating that most individuals are accidentally washed into the cave environment. These fish likely influence energy flow in the cave ecosystem. Flow reversal is dependent on a dynamic between river stage and local ground …
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Impact of combined sewer overflows on hydrodynamics and sediment transport during flow reversal events in Chicago area waterway system
The student, Chieh Ying Chen, submitted this Thesis for approval on 2018-04-18 at 15:28.
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Characterisation and simulation of bidirectional multiphase flow in tubes
The bidirectional flow reversal phenomenon results in liquid accumulation, causes significant increase in pressure drop and therefore, the pumping power. In pipelines, this poses significant problem due to the presence of slug to churn, especially in producing gas wells. To understand the …
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Periodic reverse flow in microchannel evaporators
Periodic flow reversal which is associated with boiling instabilities is a very commonly seen phenomenon in small scale heat removal applications, for instance, microchannel heat sinks for cooling of electronics. Due to the industry’s strict requirement for thermal stability, previous research on …
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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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Unsteady incompressible viscous flow past stationary, pitching or oscillating airfoil leading edges
… fundamental mechanisms governing the unsteady flow past airfoil leading edges. The approach taken is to study the leading edge in isolation and to use the semi-infinite parabola as a model for the leading-edges of conventional airfoils. Numerical solution methods were developed and implemented …
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Turbulence and Sound Generated by a Rotor Operating Near a Wall
… conditions and yaw angles with respect to the inflow. At the highest thrust condition a strong flow reversal in the wall-rotor tip gap was observed. Average velocity fields filtered by the angular position of the rotor show that the flow reversal is fed by jets of fluid that tend to form below …
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Analysis of reverse flow restriction device to prevent fuel dryout during loss of coolant and instability accidents of boiling water reactors
… The method is based on a device called Reverse Flow Restriction Device (RFRD) and its purpose is to allow the flow in the forward direction, but prevent the flow in reverse direction which occurs in multiple accident scenarios. In this thesis, detailed TRACE/PARCS simulations have been used to …
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Noise from a Rotor Ingesting Inhomogeneous Turbulence
… partially embedded in a boundary layer. The inflow distortion effect on the rotor angle of attack distribution was determined directly from the on-blade measurements, and was found to minimally affect the angle of attack at the blade tips and lower the angle attack in the rotor disk plane as …
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Wake deceleration of a racecar multielement airfoil in ground effect
… downforce as a result of the interaction between flows around adjacent elements, there may exist off-the-surface flow reversal, commonly known as wake bursting, causing an adverse effect on the downforce generated. Since the phenomenon of off-the-surface flow reversal occurs as a result of …
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Using a Sliding Plate Rheometer to Obtain Material Parameters for Simulating Long Fiber Orientation in Injection Molded Composites
… fiber lengths subjected to transient shear flow. Fiber orientation was measured in conjunction with shear stress to determine the relationship between stress and fiber orientation. Using a compression molding sample preparation procedure, the transient shear stress response was measured for …
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Dispersion of fine particles by wave-induced mass transport near a circular island
… motion, we describe the boundary-layer flow field U0i near that cylinder. The flow field is then used to calculate the modified convective velocities Ui and symmetric dispersivities Dij. Through our calculations we have demonstrated convective flow reversal for both large and very small …
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Aerodynamic modeling of a 2-dimensional airfoil with a covert-inspired deployable flap using a discrete vortex method
… feather called the covert feather to correct for flow reversal over their wings during high-angle-of-attack maneuvers, thereby delaying the onset of stall. The overall research goal is to extend the understanding of the covert feather's role during flight in nature and learn from it to increase …
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A Mechanistic Model for Flooding in Vertical Tubes
In a counter-current two-phase flow system, flooding can be defined as the onset of flow reversal of the liquid component which results in an upward co-current flow. Flooding in the surge line of pressurized water reactors poses a significant technical challenge in the analysis of several …
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Induced-charge electrokinetics at large voltages
… behavior of colloidal particles, high-frequency flow reversal in microfluidic ACEO pumps, and concentration dependence of electrokinetic slip. Theoretical developments would help not only in exploiting poorly understood effects favorably, but also in building more efficient microfluidics devices. …
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Pressure transients in a ruptured gas pipeline with friction and thermal effects included
… By assuming one-dimensional homogeneous gas flow and neglecting minor losses and changes in cross-sectional area of the pipe, three simultaneous non-linear partial differential equations were derived from first principles which mathematically model pressure transients in a non-perfect gas. A …
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Design and aerodynamic analysis of an airfoil with a bioinspired leading edge device for stall mitigation at low Reynolds number operation
… of the BL at post stall angle of attacks delays flow reversal and separation and decreases associated drag. Results show that as alula deflection ratio increases, the lift coefficient Cl also increase. At post stall angles of attack, the wake velocity deficit zone is shown to reduce in size when …
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Some unsteady features of turbulent boundary layers
… was investigated. Phase ensemble-averaged flow characteristics of a large amplitude periodic unsteady turbulent boundary layer was also investigated at a reduced frequency k = 0.61 based on the length of the converging and diverging test section with amplitude to mean velocity ratio of 0.8. …
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L1 Adaptive Control of Uncertain Nonlinear Systems with Dynamic Constraints: As Applied to Commercial Aircraft Engines
… unable to work against incoming air resulting in flow reversal, must be avoided. To decrease the chances of entering into surge or stall, control systems are developed to control stall margin, which are percentage estimates of the probability that an engine will enter surge or stall. Overall, the …
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