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 19 of 19 for “"wall roughness"”.
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NUMERICAL ANALYSIS OF TURBULENT GAS-SOLID FLOWS IN A ROUGH HORIZONTAL CHANNEL USING THE EULERIAN TWO-FLUID MODEL
… The current dissertation explores the effects of wall roughness on the particle-phase properties of a turbulent gas-solid flow in a horizontal channel. An in-house numerical code is modified to simulate a fully developed turbulent gas-solid flow; the numerical code is based on the two-fluid …
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Open channel turbulent boundary layers and wall jets on rough surfaces
… by the turbulence structure in the near-wall region. Although many flows of practical interest occur on rough surfaces, our understanding and ability to predict rough wall turbulent flows lags far behind the corresponding technology for smooth surfaces. This provides reasonable grounds …
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An experimental investigation of the effects of inlet geometry on the performance of a bistable fluid amplifier
… parameters (external operating conditions, wall roughness, setback, and other geometric variables) on the amplifier performance were studied. The results are compared with typical commercial bistable fluid amplifiers. When the flow entered the power nozzle from a right angle bend, a bias in …
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Experimental Investigation of Turbulent Flows at Smooth and Rough Wall-Cylinder Junctions
… the interaction between a fluid moving over a wall with an obstacle mounted on the same surface. Understanding the physics of such flows is of great interest to engineers responsible for the design of systems consisting of wall-body junctions. From aerodynamics to turbomachinery and electronics …
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Pneumatic conveying in the dense and dilute phase
… like particle size, conveying velocity, pipe wall roughness etc, is a complex one. Computational fluid dynamics (CFD) was being used to investigate the relationship between these parameters, as well as observe the flow patterns that result. Two computational models were used, one with an …
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Roughness Effects on Super Structures in Turbulent Boundary Layer Flows
This study investigates the influence of wall roughness on large-scale structures within turbulent boundary layers, using wall-parallel stereoscopic Particle Image Velocimetry (PIV) at a Reynolds number of 1.3 × 106m−1. The data was collected at a distance of = 2.8 from the wall under adverse = …
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Sensitivity Analysis of Partial Differential Equations With Applications to Fluid Flow
… of equilibria. We also demonstrate that small wall roughness can lead to transition by causing the linearized system to become unstable. Sensitivity methods are used to obtain important information about the disturbed problem and to illustrate that it is possible to have a precursor to predict …
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Acoustic monitoring of hydraulic resistance in partially full pipes.
Hydraulic losses in sewer pipes are caused by wall roughness, blockages and in-pipe sedimentation. Hydraulic resistance is a key parameter that is used to account for the hydraulic energy losses and predict the sewer system propensity to flood. Unfortunately, there are no objective methods to …
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Device integration for silicon microphotonic platforms
… strip waveguide and is due to improved side-wall roughness. The TM mode of a single mode polySi strip waveguide with a 1:2.5 aspect ratio exhibited, surprisingly, smaller loss than the TE mode. Further, analysis shows that high index contrast waveguides are more sensitive to polarization …
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ΒΕΛΤΙΩΜΕΝΗ ΜΕΘΟΔΟΣ ΑΝΑΛΥΣΗΣ ΤΗΣ ΠΟΡΩΔΟΥΣ ΔΟΜΗΣ ΔΙΑΠΕΡΑΤΩΝ ΣΤΕΡΕΩΝ: ΕΦΑΡΜΟΓΗ ΣΕ ΕΛΛΗΝΙΚΑ ΠΕΤΡΕΛΑΙΟΦΟΡΑ ΠΕΤΡΩΜΑΤΑ
… THROAT SIZES AND CHAMBER SIZES AND THE PORE WALL ROUGHNESS) ON THE FORM AND THE DEGREE OF HYSTERESISOF THEORETICAL CAPILLARY PRESSURE CURVES IS INVESTIGATED. THE RELIABILITY OF THE SIMULATOR IS EVALUATED WITH RESPECT TO THE QUALITATIVE PREDICTION OF THE CAPILLARY BEHAVIOUR OF GREEK …
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Radar Imaging Applications for Mining and Landmine Detection
… collapse hazards. GPR data were acquired on the wall of a pillar in an underground mine. Strong radar reflections in the field data correlate with fractures and a cave exposed on the pillar walls. Pillar wall roughness was included in migration, a wavefield imaging algorithm, to quantitatively …
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Energetics of Turbulence Explains Physical Transport Processes in the Environment
… interactions between turbulent eddies and bed roughness. The result is a mathematical derivation of a modified Nikuradse curve that links the friction factor to Reynolds number and wall roughness.</p><p>Chapter 3 extends the co-spectral budget model to link the incipient motion of sediments to …
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Migration of an intruder particle in a boundary driven shear flow
… is induced by allowing the upper and lower bumpy walls to move with the same constant speed in opposite directions. The wall particles are in square arrangements and have the same size as the regular flow particles. The typical transport properties of this flow are characterized by the depth …
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Geometry-Aware Modeling of Rough-Wall Turbulence Using Reynolds-Averaged Navier-Stokes (RANS) Frameworks
Turbulent flow over rough walls is widespread in engineering systems and plays a critical role in drag prediction, energy efficiency, and transport processes in internal and external flows. Despite extensive research, the representation of roughness effects in Reynolds-Averaged Navier–Stokes (RANS) …
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Axial behavior of drilled shafts in soft rock
… a database of measured in situ values of socket wall roughness height. A predictive model is proposed for the peak shear strength for the side resistance of drilled shafts in soft rock. The back-calculated shear stress-shear displacement (t-z) relationships from drilled shaft load tests are used …
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The taiji and infinity-loop microresonators: examples of non-hermitian photonic systems
… mainly due to the waveguide surface-wall roughness, on the microresonators is also studied. This phenomenon induces simultaneous excitation of the clockwise and counterclockwise modes, leading to eigenvalue splitting. This splitting makes the use of typical quality factor estimation …
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Probabilistic models for drug dissolution
… of dissolving components, development of wall-roughness at the solid-liquid interface, diffusion through occlusions and pores and moving concentration boundary layers were examined and directly accounted for in the model. As a result, new models have been developed for: i) matrix soluble …
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Science of Nanofluidics and Energy Conversion
… dependent of temperature of liquid molecules and wall morphology of nanopores. Using MD simulations, the effects of temperature and wall roughness on the transport resistance of water molecules inside nanopores are investigated in Chapter 3. The effective shear stress and nominal viscosity that …
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Normalization of Roughness Noise on the Near-Field Wall Pressure Spectrum
Roughness noise can be a significant contributor of sound in low Mach number, high Reynolds number flows. Only a small amount of experimental research has been conducted to analyze roughness noise because of its often low energy levels that are hard to isolate even in a laboratory setting. This …