Thesis (M.S.)--Ohio University, August, 2004. / Includes bibliographical references (p. 120-124)

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Ari Glezer; Committee Member: Bojan Vukasinovic; Committee Member: Mark Costello. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 120-124)

Made available in DSpace on 2014-10-09T12:50:37Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:58Z (GMT). No. of bitstreams: 1 00694.pdf: 1855025 bytes, checksum: 6c25433cbddf2c8d170f6f4df0705156 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Fisica, Universidade de Sao Paulo - IF/USP

Made available in DSpace on 2014-10-09T12:50:37Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:58Z (GMT). No. of bitstreams: 1 00694.pdf: 1855025 bytes, checksum: 6c25433cbddf2c8d170f6f4df0705156 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Fisica, Universidade de Sao Paulo - IF/USP

It is widely recognized that topographically-driven groundwater flow can perturb conductive thermal regimes. High-relief topography amplifies the impact of factors controlling groundwater flow and advective heat transfer. A finite element method is developed to model the influence of geology, climate, surface topography and regional heat flux on steady groundwater flow and heat transfer. Because fluid viscosity (hence fluid flux) depends upon temperature, groundwater flow is influenced by the regional heat flux. As a consequence, isothermal approaches to modeling deep groundwater flow in mountains may be inappropriate. Using a free-surface approach, the water table is represented as an internal characteristic of the groundwater flow system, rather than the upper boundary for fluid flow. Thick unsaturated zones are expected in high-permeability terrain (greater than 10⁻¹⁵ m²) with arid climate, or where groundwater recharge is restricted by extensive alpine glaciers. Only vertical fluid flow is assumed to occur in the unsaturated zone, therefore, heat transfer above the water table is represented by one-dimensional advection and two-dimensional conduction. Simulation results indicate that water table elevations are highly sensitive to changes in the controlling factors, but have little impact on the thermal regime. Conductive thermal regimes are predicted in low-permeability terrain (less than 10⁻¹⁸ m²) or in high-permeability terrain with arid climate (recharge rates less than 10⁻¹¹ m/sec). Strong advective heat transfer masks the regional heat flux when permeability exceeds 10⁻¹⁶ m² in terrain with relief of 2 km over a horizontal distance of 6 km. Less than one percent of typical mean annual precipitation is transmitted through deep groundwater flow systems under these conditions. Asymmetric surface topography complicates efforts to interpret chemical and thermal data collected near the valley floor. Fracture zones outcropping at the valley floor can capture a large percentage of groundwater flowing through the system and a significant percentage of the basal heat flux. Maximum spring temperatures are indicated when bulk permeability is between 10⁻¹⁷ m² and 10⁻¹⁵ m². Outside this range, spring temperatures approach ambient air temperature. Topographically driven groundwater flow can distort and obliterate free-convection cells that might otherwise develop within a mountain massif. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Thesis (Ph. D. - Hydrology and Water Resources)--University of Arizona, 1983. / Includes bibliographical references (leaves 194-200).

No description available.

The primary aim of this thesis is to investigate the transition between different flow regimes in porous media. The complete transition spectrum of single-phase flow, from creeping flow to inertial, unsteady laminar, and turbulent flow regimes, was examined in sphere packings. Further understanding of the fundamental fluid dynamics was derived based on the pore-scale flow visualisation using magnetic resonance velocimetry (MRV). Spiral imaging was selected as the ultrafast imaging protocol to probe the transient phenomena, and the acquisition was further accelerated by combining subsampling and compressed sensing reconstruction. In a random sphere packing column with column-to-diameter ratio of 3.44, the inertial effect and the onset of unsteady regime were examined with respect to the principal flow characteristics: the inertial core/channeling, backflow, and helical vortices. Helical vortices have been observed experimentally in a random packing for the first time, and the analogy between the swirling flow and helical vortices provides insight into the design and operation of packed bed reactors. Another new observation is that the transition to the unsteady regime is a highly heterogeneous process, where the evolution of the flow instability depends on the pore geometry. Moreover, pixelwise validation was achieved between the experimental and simulation results on three-dimensional velocity fields in the inertial regime; this is enabled by an image-based meshing pipeline, which reproduces the geometry of the random packing in MRV for the numerical simulation. The unsteady regimes were further investigated using a regular sphere packing, the simple cubic packing (SCP). The spectral analysis, in both the random and regular packing, revealed a route to chaos from the steady to periodic, quasi-periodic, and chaotic dynamics, which was only predicted numerically before. During the transition to turbulence, the coherent structures were extracted using proper orthogonal decomposition (POD), which yields a coherent picture regarding the turbulent dynamics, when combined with the skewness, flatness, and quadrant analysis. Furthermore, it was found that the macroscopic properties converged at lower Reynolds number than the microscopic features. In conclusion, the opportunity to measure flow fields at high spatial and temporal resolution will play an increasingly significant role in the advancement of fundamental fluid dynamics. In this thesis, MRV is used, which is particularly advantageous for non-invasive measurements in opaque systems. This thesis provides the experimental and analysis toolkits for such studies and has demonstrated the contribution to characterising and understanding different flow regimes in porous media.

No description available.