In this thesis, turbulent forced convective heat transfer downstream of blockages with elongated holes in a rectangular channel was studied. The rectangular channel has a width-to-height ratio of 12:1. The blockages have the same cross section as that of the channel. The diameter of all elongated holes of the blockages is three quarters of the channel height. The blockages are classified into two different types with two different hole-to-blockage area ratios (ratio of total crosssectional area of holes to cross-sectional surface area of the blockage) of 0.5 or 0.6. For each hole-to-blockage area ratio, the blockages are again subdivided into three different cases using three different aspect ratios (hole-width-to-height ratio) which are determined by the number of holes four, six, and eight holes per blockage. Experiments for total six different cases of blockages were performed under a uniform wall temperature condition (50C). The experiments were conducted at three different Reynolds numbers of about 7,000, 12,000, and 17,000, respectively. Three copper plate heaters with twenty one embedded thermocouples were used to measure the average heat transfer on the surface of channel walls between two consecutive blockages. Results from this study showed that the blockages with elongated holes enhance the average heat transfer by up to 5.06 and 4.08 times that by fully developed turbulent flow through a smooth channel at the same Reynolds numbers for small and large holeto- blockage area ratios, respectively. The friction factor ratios for small and large holeto- blockage area ratios of the blockages reached 345 and 89 times, respectively, that by fully developed turbulent flow through a smooth channel at the same Reynolds numbers. TP (Thermal Performance) values varied from 0.65 to 1.11 depending on cases. According to the results, Case L-2, which has six elongated holes and hole-toblockage area ratio of 0.6, is the best option from the TP point of view. But Case S-2, which also had six elongated holes and hole-to-blockage area ratio of 0.5, can be an alternative when more weight should be put on the heat transfer enhancement than TP value.

An increase in the amount of lightning and rainfall over the Houston area, compared to the surrounding rural areas, has been well documented in previous studies. The placement of a Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) in the Houston area during the summer season of 2005 presented a unique opportunity to investigate the role of boundary-layer convergence in modulating convective frequency and intensity and, thereby, likely causing the rainfall and lightning anomalies. The role of the urban heat island (UHI) and the sea-breeze, as a source of low-level convergence leading to enhanced convection over Houston, was examined. Hourly average dual-Doppler wind and convergence maps were created on 1 X 1 km grids for an eleven-week period. By using these images along with average lightning, rainfall, and reflectivity for a large Houston-centered domain, it was possible to discern a correlation between low-level convergence and convection. Also, past findings of enhancement in lightning and rainfall over Houston and downwind of Houston were validated. High convergence levels for the Houston area in the mid-morning were followed closely by a peak in convection in the early afternoon. The enhancement of rainfall and lightning over and downwind of downtown was found to be primarily from a large increase in frequency of deep convective events when compared to the surrounding domain. Also, it was found that UHI, rather than sea-breeze, was likely the primary causative mechanism in the development of convection over the Houston area because of the lack of deep convection in areas equally affected by the sea-breeze and the timing of the convection compared to time of peak sea-breeze. An area of weaker enhancement south of Houston, not discussed in previous studies, was found to be present, possibly from the interactions between the bay-breeze off of the Galveston Bay and the seabreeze.

Thesis (Ph.D.) -- University of Texas at Arlington, 2008.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 105-110).

Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Henry E. Fuelberg, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Mar. 1, 2004). Includes bibliographical references.

Mantle convection is the principal control on the thermal and geological evolution of the earth, including the motion of the tectonic plates, which in turn influences earthquakes, tsunamis, and volcanic eruptions. This system is governed by the equations for balance of mass, momentum, and energy for a viscous incompressible non-Newtonian fluid. Taking present-day temperatures as given, the time dependence can be neglected, eliminating the energy equation. In this case, the physics of the mantle are modeled by the Stokes equation with nonlinear rheology (the so-called forward problem). This dissertation focuses on solving the mantle convection inverse problem governed by the nonlinear Stokes forward problem with full nonlinear rheology, with an infinite-dimensional adjoint-based inversion method. The need for inverse methods in the study of mantle convection stems from the fact that the constitutive parameters are subject to uncertainty. Inversion for nonlinear rheology parameters presents considerable difficulties, which are explored in this dissertation. A spectral analysis of the Hessian operator is performed to investigate the ill-posedness of the inverse problem. The general form of the numerical eigenvalues is found to agree with that of the theoretically-derived ones (based on a model 1D Stokes problem), both of which collapse rapidly to zero, suggesting a high degree of ill-posedness. This motivates the use in this thesis of regularizations that are of Tikhonov type (favoring smooth viscosity) and total variation type (favoring piecewise-smooth viscosity). In addition, the eigenfunctions of the Hessian indicate that increasingly smaller length scales of viscosity are increasingly less observable, and that resolution decays with depth. The wide range of spatial scales of interest (varying from 1 km scale associated with plate boundaries to 10⁴ km global scales) prompts the use of adaptive mesh refinement in a parallel framework. The results show that both higher levels of nonlinearity and larger orders of magnitude of variation in the viscosity cause the inverse problem to be more ill-conditioned, increasing the difficulty of solving the inverse problem. Despite the severe ill-posedness of the inverse problem, stemming from the small number of observations compared to large number of degrees of freedom of the viscosity parameters, with the correct regularization weight and the right type of regularization, it is possible to reasonably infer information about the viscosity of the mantle, particularly in shallow regions. A number of 2D and 3D inversions are shown to demonstrate these capabilities. / text

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A series of steady-state water condensation experiments were conducted to determine the effects of Marangoni convection on the condensation flux. The interface was flat so that the results of the interfacial temperature discontinuities could be compared to past condensation experiments conducted under similar experimental conditions using a spherical interface. Two experimental methods were used. Method 1 was to vary the temperature in the cooling pipes (Tcp ) with the position of the interface relative to the cooling pipes fixed. Method 2 was to vary the position of the interface while Tcp was held constant. The interfacial temperature discontinuities in this study were approximately 2.3-9 times smaller in magnitude, than those measured using a spherical liquid-vapour interface. The experimental results showed that the condensation flux increased as thermocapillary convection increased (increase in interfacial temperature gradients and speed). This increase resulted in a 1.37-12.5 times enhancement in the condensation flux of pure water.