The objective of this study is to investigate the effect of Atlantic meridional overturning circulation (AMOC) changes on tropical coupled ocean-atmosphere system via oceanic and atmospheric processes. A suite of numerical simulations have been conducted and the results show that both oceanic and atmospheric circulation changes induced by AMOC changes can have a profound impact on tropical sea surface temperature (SST) and sea surface salinity (SSS) conditions, but their dominance varies in different parts of the tropical oceans. The oceanic process has a dominant control on SST and SSS response to AMOC changes in the South Tropical Atlantic, while the atmospheric teleconnection is mainly responsible for SST and SSS changes over the North Tropical Atlantic and Pacific Oceans during the period of reduced AMOC. The finding has significant implication for the interpretation of the paleotemperature reconstructions over the southern Caribbean and the western Tropical Atlantic regions during the Younger Dryas. It suggests that the strong spatial inhomogeneity of the SST change revealed by the proxy records in these regions may be attributed to the competing oceanic and atmospheric processes that dominate the SST response. Similar mechanisms may also explain the reconstructed paleo-salinity change in the tropical Atlantic, which shows a basin-wide increase in SSS during the Younger Dryas, according to recent paleo climate studies. Finally, we show that atmospheric teleconnection induced by the surface cooling of the North Atlantic and the North Pacific in response to a weakened AMOC, is a leading physical mechanism that dictates the behavior of El Nino/Southern Oscillation (ENSO) response to AMOC changes. However, depending on its origin, the atmospheric teleconnection can affect ENSO variability in different ways. The atmospheric process associated with the North Atlantic cooling tends to enhance El Nino occurrence with a deepened mean thermocline depth in the eastern Pacific, whereas the atmospheric process associated with the North Pacific cooling tends to produce more La Nina events with a reduced mean thermocline depth in the eastern Pacific. Preliminary analysis suggests that the change in ENSO characteristics is associated with the change in internal atmospheric variability caused by the surface cooling in the North Atlantic and North Pacific. Complex nature of the underlying dynamics concerning the effect of the AMOC on ENSO calls for further investigation into this problem.

Carbonates invariably have small (micron) to large (centimeter) scale heterogeneities in flow properties that may cause the effects of injected acids to differ greatly from what is predicted by a model based on a homogenous formation. To the best of our knowledge, there are neither theoretical nor experimental studies on the effect of large scale heterogeneities (vugs) on matrix acidizing. The abundance of carbonate reservoirs (60% of the world?s oil reserves) and the lack of a detailed study on the effect of multi-scale heterogeneities in carbonate acidizing are the main motivations behind this study. In this work, we first present a methodology to characterize the carbonate cores prior to the core-flood acidizing experiments. Our approach consists of characterization of the fine-scale (millimeter) heterogeneities using computerized tomography (CT) and geostatistics, and the larger-scale (millimeter to centimeter) heterogeneities using connected component labeling algorithm and numerical simulation. In order to understand the connectivity of vugs and thus their contribution to flow, a well-known 2D visualization algorithm, connected component labeling (CCL), was implemented in 3D domain. Another tool used in this study to understand the connectivity of the vugs and its effect on fluid flow is numerical simulation. A 3D finite difference numerical model is developed based on Darcy-Brinkman formulation (DBF). Using the developed simulator a flow-based inversion approach is implemented to understand the connectivity of the vugs in the samples studied. After multi-scale characterization of the cores, acid core-flood experiments are conducted. Cores measuring four inches in diameter by twenty inches in length are used to decrease the geometry effects on the wormhole path. The post acid injection porosity distribution and wormhole paths are visualized after the experiments. The experimental results demonstrate that acid follows not only the high permeability paths but also the spatially correlated ones. While the connectivity between the vugs, total amount of vuggy pore space and size of the cores are the predominant factors, spatial correlation of the petro-physical properties has less pronounced effect on wormhole propagation in acidiziation of carbonates. The fact that acid channeled through the vugular cores, following the path of the vug system, was underlined with computerized tomography scans of the cores before and after acid injection. This observation proposes that local pressure drops created by vugs are more dominant in determining the wormhole flow path than the chemical reactions occurring at the pore level. Following this idea, we present a modeling study in order to understand flow in porous media in the presence of vugs. Use of coupled Darcy and Stokes flow principles, known as Darcy-Brinkman formulation (DBF), underpins the proposed approach. Several synthetic simulation scenarios are created to study the effect of vugs on flow and transport. The results demonstrate that total injection volume to breakthrough is affected by spatial distribution, amount and connectivity of vuggy pore space. An interesting finding is that although the presence and amount of vugs does not change the effective permeability of the formation, it could highly effect fluid diversion. We think this is a very important observation for designing of multi layer stimulation.

The charge-carriers of the organic layers are one of the dominant factors to influence the performance of OLEDs. Thus, it is very important to study and understand the charge transporting behaviors in the organic layers of OLED. However, the organic materials show usually to have very high resistivity and very low carrier mobility, and then using general modeling techniques suitable for common semiconductors cannot conveniently simulate that. First, a transporting model of the bilayer organic OLED are proposed in this dissertation, in which model were based on the current-voltage characteristics simulation proposed by Lampert and the continuous equation of current transport. The model contains a description of ohmic contacts, thermal emission and tunneling injection, space charge effects, trap effect, field dependent mobility and recombination processes. In addition, the method of Monte Carlo is a computational technique by using random numbers to compute an approximation to something whose exact value is difficult or impossible to compute, and that is used to simulate the bilayer organic OLED. In this study, a numerical model proposed is successfully applied to describe the characteristics of the bilayer organic light-emitting diode. The model is satisfyingly demonstrated not only for applying to simulate several bilayer devices (1-Naphdata/Alq3¡BTPD/Alq3) reported but also for some devices obtained in our results. Finally, it can be extended to optimize the analysis and fabrication of bilayer devices.

Remediation of DNAPL contaminated sites in fractured rock has proven to be very difficult. No current technology can be used to remediate such sites in a timely and economic manner due to the inherent heterogeneity of fractured rock and back diffusion of contaminants stored in the rock matrix. This study was conducted in order to evaluate the viability of biostimulation of native biofilm as a means to control flow and back diffusion at fractured rock sites. A field trial was conducted at an uncontaminated site in southern Ontario. The site is underlain by dolomites of the Lockport formation. Three major fracture zones have been identified in the study area. Two closely spaced (5.04 m) boreholes were used to isolate a fracture zone at a depth of 17 m with straddle packers. These boreholes were used to create an injection-withdrawal system with recirculation, which was used for tracer injection in order to load the rock matrix with a conservative dye tracer and to inject nutrients for 21 days in order to stimulate the growth of biofilm in the fracture. Evaluation of the ability of the biofilm to control flow through the fracture was conducted through pulse interference tests. Pulse interference tests were conducted before and after the injection of nutrients. The results from the pulse interference tests showed a maximum 65% reduction in transmissivity, which is equivalent to a 28% reduction in fracture aperture shortly after the cessation of biostimulation. In order to investigate the effect of the biofilm stimulation on matrix diffusion the rock matrix was loaded with Lissamine, a conservative fluorescent dye tracer prior to biostimulation and its concentration was monitored at injection and withdrawal wells. The effect that biostimulation had on matrix diffusion was determined by comparing field concentration measurements with a model that simulates a system unaffected by biofilm stimulation. The biostimulation lowered the concentration of tracer attributable to back diffusion at the withdrawal well by about 20% for approximately 30 days following the cessation of biostimulation. It is also thought that large amounts of tracer might have been trapped in the biofilm as it formed and was then released back into the fracture as the biofilm deteriorated. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-08-11 19:27:44.232

The experimental investigation in this report was conducted both as indicator of the problems in McCormacks bay, and also as a base for the calibration of a numerical model of the hydraulic characteristics of the bay. There are some issues of public concern associated with the bay at the present time. These are related to dominant algae populations and their related problems, and the desire to preserve the existing bay as a healthy marine environment. Numerical models can be a useful tool to test various management options. A component of this study involved the calibration of a numerical model which described the response of the bay to tidal functions in the estuary. Calibration was achieved using data from measurements taken on the eighteenth of December 1996. The model was based specifically around the main central culvert running under the causeway. The model showed that an increase in the depth of this culvert would increase the range of water levels in the bay by up to 23%. This is significant and would increase the tidal exchange in the bay, thereby promoting circulation.

No / Free surface flows of practical relevance in many engineering problems are almost always turbulent. In this paper, a numerical model to compute the free surface flow with turbulent effects is presented. The shallow water equations together with a k-ε turbulent model are discretized and simulated using a MUSCL-HANCOCK finite volume scheme. The proposed 2D k-ε shallow water model calculates the depth-averaged quantities such as water depth and velocity profile. The depth-averaged turbulent viscous stresses are determined from the depthaveraged version of a traditional 3D k-ε turbulent model. The numerical model is applied to a flow within channels that contain full depth obstructions. The k-ε turbulent model results are compared with existing Direct Numerical Simulations (DNS) predictions and show a high level of accuracy.

The motivation of this study is to understand the seismic anisotropy observations from various subduction regions of the world. In subduction zone backarcs both trench-parallel and trench-normal seismic anisotropy, or fast wave polarization direction of shear wave, are observed. In the mantle the general assumption is that seismic anisotropy is caused by Lattice Preferred Orientation (LPO) of olivine minerals and that the direction of anisotropy is an indicator of the direction of mantle flow. The complex pattern of seismic anisotropy observations suggests that the flow geometry in the vicinity of subduction zones differs at different subduction zones with some subduction zones having trench perpendicular flow, consistent with corner flow in the mantle wedge while other subduction zones have trench parallel flow, consistent with a mode of flow where material from the mantle wedge flows around the edges of the slab. It should be noted that the direction of LPO orientation can also be modified by the presence or absence of water, pressure, and temperature in the mantle and that it is possible that the difference in anisotropy observations reflects a difference in water content or thermal structure of back arcs. The aim of this study is to test whether the flow geometry of mantle in numerical subduction calculations can influence the direction of seismic anisotropy and if we parameters that control the pattern of flow can be identified. In this study we explicitly assume that seismic anisotropy occurs only due to plastic and dynamic re-crystallization of mantle mineral forming LPO. To approach the problem two different models are formulated. In one of the models the trench evolves self-consistently, with no prescribed artificial zones of weakness. The self-consistent model has a sticky-air layer at the top of the model domain that mimics a "free-surface." The other model has the same initial conditions but a trench-migration velocity boundary condition is imposed to the model. The mantle flow pattern for the self-consistent model is consistent with the 2D corner flow with no flow around the trench and no trench migration. However when the trench-migration velocity boundary condition is imposed, 3D flow around the mantle is observed. The stress field from these simulations are used to calculated instantaneous strain axis directions which correlate with LPO directions. The LPO orientations are measured from the models showing that the seismic-anisotropy direction is primarily trench-perpendicular for both models. Because the models have different flow patterns, the trench-perpendicular anisotropy alignment that is calculated for both the models is a bit puzzling. It could be that factors such as high temperature and non-linear rheology cause the LPO direction to align trench perpendicular in both the cases. It can also be possible that the 3D vertical flow is not strong enough to cause change in orientation of the LPO direction. From the present study it can be concluded that by looking at the LPO direction nature of mantle flow might not be predicted. This suggests that in addition to flow direction other factors such as the presence of water in mantle wedge, pressure, and high temperature due to viscous coupling modify the seismic anisotropy directions. / Master of Science

Storm surges induced by tropical cyclones have been ravaging coastal communities worldwide, where a growing number of people reside. Tremendous life and economic losses are caused by tropical cyclones, contributing to more than half of the damages induced by natural hazards. To improve the resilience of coastal communities to surge hazards, it is of great importance to provide reliable and efficient real time forecasts of the spatiotemporal evolution of storm surge, as well as reliable predictions of the probabilistic surge hazards under future conditions. Three specific goals are addressed in this work. Studies on characterization and prediction of surge before a hurricane landfall show that a dimensionless relationship between intensity scaled surge magnitude and wind-duration scaled surge timing may effectively be used for rapid and reliable forerunner surge forecasting. Investigation of how probabilistic surge hazard changes with sea level rise (SLR) shows that the probabilistic surge with SLR can be 1.0 m larger, while different individual storm's surge with the same magnitude can be 1.5 m larger or 0.1 m smaller, indicating the importance of not relying on results from a limited number of storm surge events to assess the probabilistic surge hazard change to SLR. Finally, studying the temporal evolution of coastal flooding changes with SLR shows forerunner surge responds differently to SLR than peak surge, and that storm forward speed is a key factor determining the forerunner-SLR response. / Ph. D.

There is a growing need to improve the understanding of the behaviour of infrastructure in permafrost regions. Permafrost affects nearly half of the land surface in Canada, especially in the north. Further development of natural resources in northern Canada will provide socio-economic benefits to the region and its residents. Linear infrastructure, such as highways, is an important part of that development. The integrity of infrastructure in northern regions is negatively impacted by thawing and degradation of the underlying permafrost initiated by changes in both air and ground temperatures. Subsequent deformations due to settlement and lateral spreading can lead to potentially hazardous driving on highways. The author’s research focused on a section of highway embankment on Provincial Road (PR) 391 located 18 km north of Thompson, Manitoba. The purpose of the research was to further understanding of the thermal and deformation behaviour of an embankment subjected to degrading permafrost conditions. The author’s research consisted of laboratory testing, instrumentation installation, data monitoring, and numerical modelling. Laboratory tests on four-inch (101.6 mm) diameter Shelby tube samples characterized the soil at the site. Data were collected remotely via satellite, and included ground temperatures, pore water pressures, and displacements both laterally and vertically. Ground temperatures indicated a frost bulb, a region of frozen ground, under the embankment. Thermal models using TEMP/W simulated the current ground thermal regime and projections of future thermal behaviour of the embankment. Deformation numerical models using SIGMA/W incorporated changes in the size of the frost bulb over a freeze-thaw cycle to simulate the deformation behaviour of the embankment. The numerical models were compared with the collected data.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In this article, a comparative analysis is performed between one-dimensional (HEC-RAS) and two-dimensional (IBER) models, in the evaluation of total scour in the pillars and abutments of a bridge. The case study is the Huallaga bridge, located in the San Martín region, Peru.Based on the geomorphological, hydrological and hydraulic data of the study area and after carrying out an analysis of the different equations for local, general scour; Numerical modeling was performed on the HEC-RAS and IBER software in order to calculate the depths of the scour.The following results were obtained: That in the local scour calculations, the scour depths were less with the 2D software, compared to the values obtained in the 1D software; while in general scour calculations, we obtain greater depths when modeling with 2D software, compared to the values obtained in 1D software