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 30 for “"Hele-Shaw"”.
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Bubble scavenging in Hele-Shaw cell
… carried out for bubble scavenging in a gap, or Hele-Shaw cell, for various gap distances. A novel approach was developed to measure the particles collected by a single bubble by allowing the bubbles to pop and transport these particles to a glass plate where they can be counted. The experiments …
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Viscous Fingering Instability of Complex Fluids in a Radial Hele-Shaw Cell
… involving complex fluids in a radial Hele-Shaw is investigated. Many fluids in our lives such as shaving foams, glues, flour-water dough, mayonnaise, and paints are complex fluids which exhibit multiple non-Newtonian properties simultaneously such as shear-thinning or shear-thickening, …
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Reduced-dimension model for the Rayleigh-Taylor instability in a Hele-Shaw cell
In this thesis we present a reduced-dimension model for the density-driven hydrodynamic Rayleigh-Taylor instability. We motivate the project with experimental findings of a little-understood stabilizing effect of geometry and deviations of measured instability wavelength from theoretical …
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Ferrofluid dynamics in a Hele-Shaw cell simultaneously stressed by DC and rotating magnetic fields
… in biomedicine. Careful measurements in Hele-Shaw cells with simultaneous perpendicular DC and in-plane rotating magnetic fields have shown that ferrofluid drop spiral patterns rotate in the same direction as the rotating magnetic field, independent of the polarity of the perpendicular DC …
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Numerical simulation of the plastics injection moulding process
The Hele-Shaw formulation is widely used for the simulation of the injection moulding process. The influence of the Hele-Shaw approximations is, however, unknown. A two-dimensional numerical model based on the Hele-Shaw formulation, and a model based on the Navier-Stokes equations without the …
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Mechanics of seed-grown planar chemical gardens
… gardens studied in confined geometries -- Hele-Shaw cells and microfluidic chips -- is presented. Studies in these geometries have been classified into three approaches: seed-growth in Hele-Shaw cells, injection-growth in Hele-Shaw cells, and co-injection-growth in microfluidic chips. Over …
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Viscous fingering instabilities and gravity currents.–—
… fluid either in a porous medium or in a Hele-Shaw cell, which is commonly referred to as the Saffman–Taylor instability. There are three related problems studied in this thesis: a single-layer viscous gravity current spreading from a point source over a rigid surface, radial spreading of …
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Numerical detection of complex singularities in two and three dimensions
… instability, Rayleigh-Taylor instability, and Hele-Shaw flow. In this thesis, we present a new method for the numerical analysis of complex singularities in solutions to partial differential equations. In the method, we analyze the decay of Fourier coefficients using a numerical form fit to …
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Mixing with complex patterns : from the impact of miscible viscous fingering to the effects of motile bacteria
… viscous fingering has on mixing. We use a radial Hele-Shaw cell as an analog of radial flows in porous media, and high-resolution fluorescent imaging, to measure the temporal and spatial evolution of the mixing zone. We identify distinct regimes in both the interface length and average thickness …
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Ferrofluid surface and volume flows in uniform rotating magnetic fields
… surface driven flows, spin-up flows, and Hele-Shaw cell flows and instabilities. To characterize the water-based and oil-based ferrofluids used in experiments, measurements were made of the magnetization curve, surface tension, viscosity, density, and the speed of sound. Extensive …
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Self-assembled Precipitation Membranes and the Implications for Natural Sciences
… where flow is forced by a pump and others in a Hele-Shaw cell where the flow is driven by the membrane itself. In the first, with externally forced flow, the growth of a wavy precipitate membrane is observed. We establish that its growth is controlled by transverse diffusion and dispersion of …
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Dynamics of confined chemical gardens and implications for submarine methane hydrates
… contact with solutions such as sodium silicate. Hele-Shaw cells, quasi-two-dimensional micro reactors, can be used to reduce the complexity of the system: osmosis is removed when performed with injection, and buoyancy if placed horizontally; the results are thus only dependent on the relationship …
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Nanoparticle Transport Through Fractures And Heterogeneous Porous Media
… in laboratory apparatus with different geometry (Hele-Shaw fracture cell, Rectangular and Cylindrical Beadpack columns). The Interpretation required models that take into account the flow in the halo as well as the core and, which also include dispersion. All experiments could be interpreted in a …
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A Numerical Scheme for Mullins-Sekerka Flow in Three Space Dimensions
… Mullins-Sekerka problem, also called two-sided Hele-Shaw flow, arises in modeling a binary material with two stable concentration phases. A coarsening process occurs, and large particles grow while smaller particles eventually dissolve. Single particles become spherical. This process is …
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Optimal design and analysis for polymer extrusion and molding
… for the pressure field which are formed via the Hele-Shaw flow analysis and Galerkin finite element method. The pressure induced velocity field is then used to derive a hyperbolic differential equation which evaluates the material residence time in the polymer melt. This hyperbolic equation lacks …
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Elongated microswimmers: influence of hydrodynamics
… rods both in the bulk fluid as well as in the Hele-Shaw geometry, i.e., in narrow confinement between two parallel plates. Using hydrodynamic multipole expansions, we categorize the different multipole contributions created by neutral, and pusher squirmer rods in the bulk fluid as well as in …
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Experimental Investigations on Flow and Mass Transport in Stressed Rough Fractures
… thesis I introduce a novel pressure-controlled Hele-Shaw cell to investigate different physical processes in rough fractures using 3D-printed rock analogs. This system can measure high-resolution fracture aperture and tracer concentration maps under relevant field stress conditions. Using a …
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Moving contact lines, wetting transitions and interfacial instabilities in confined environments
… less wetting and more viscous liquid in a radial Hele-Shaw cell (two plates separated by a small gap). We show that the wetting liquid invades the cell in the form of a thin-film front, which becomes unstable and leads to a viscous fingering pattern. To gain an understanding of the front dynamics, …
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Improvement in Orientation Predictions of High-Aspect Ratio Particles in Injection Mold Filling Simulations
… the other hand, orientation predictions with the Hele-Shaw flow approximation showed significant over-predictions in the frontal region. With model parameters determined from fitting to rheological data, coupling did not show any significant improvements. However, with the use of a smaller value …
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Magnetic fluid flow phenomena in DC and rotating magnetic fields
… two glass plates separated by a small gap (Hele-Shaw cell) and excited by an applied uniform rotating magnetic field first and then a DC axial magnetic field, a phase like transition occurs that transforms the ferrofluid drop from a continuous phase to a discrete phase. Considering the …
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