Thesis (M.Sc. (Civil Engineering)--University of the Witwatersrand, Faculty of Engineering, 1992.

The study addresses the coating selection for a proposed placement of a hydroturbine into the Gulf Stream. The turbine will generate energy in a similar manner to a wind turbine. The effects of biofouling and corrosion in the current project are assessed. A review of different types of traditional paint coatings is given, as well as the option for a copper-nickel alloy. Testing that should be undertaken for the coating selection is described in detail. Coating considerations are offered and discussed. Design considerations and modifications are also offered. / by Andrew Spicer Bak. / Vita. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Arid regions tend to take careful measures to ensure water supplies are secured to consumers, to help provide the basis for further development. The distribution network is the most expensive part of the water supply infrastructure and it must maintain performance during unexpected incidents. Many aspects of performance have previously been discussed separately, including reliability, vulnerability, flexibility and resilience. This study aimed to develop a framework to bring together these aspects as found in the literature and industry practice, and bridge the gap between them. Semi-structured interviews with water industry experts were used to examine the presence and understanding of robustness factors. Thematic analysis was applied to investigate these and inform a conceptual framework including the component and topological levels. Robustness was described by incorporating network reliability and resiliency. The research focused on resiliency as a network-level concept derived from flexibility and vulnerability. To utilise this new framework, the study explored graph theory to formulate metrics for flexibility and vulnerability that combine network topology and hydraulics. The flexibility metric combines hydraulic edge betweenness centrality, representing hydraulic connectivity, and hydraulic edge load, measuring utilised capacity. Vulnerability captures the impact of failures on the ability of the network to supply consumers, and their sensitivity to disruptions, by utilising node characteristics, such as demand, population and alternative supplies. These measures together cover both edge (pipe) centric and node (demand) centric perspectives. The resiliency assessment was applied to several literature benchmark networks prior to using a real case network. The results show the benefits of combining hydraulics with topology in robustness analysis. The assessment helps to identify components or sections of importance for future expansion plans or maintenance purposes. The study provides a novel viewpoint overarching the gap between literature and practice, incorporating different critical factors for robust performance.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Microfiche copy available in Archives and Engineering. / Bibliography: p.163-164. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Lee Wing Ho. / M.S.

No description available.

This work addresses the poroelastic effect on the processes involved in hydraulic fracturing and post-fracture production using a finite element based fully coupled poroelastic model which includes a triple system of wellbore-fracture-reservoir. A novel numerical procedure for modeling hydraulic fracture propagation in a poroelastic medium is introduced. The model directly takes into account the interaction of wellbore, hydraulic fracture and reservoir in a fully coupled manner. This allows realistic simulation of near fracture phenomena such as back stress and leak-off. In addition, fluid leak-off is numerically modeled based on the concept of fluid flow in porous media using a new technique for evaluating local pressure gradient. Besides, the model is capable of accommodating the zone of reduced pressure (including intermediate and fluid lag zones) at the fracture front so as to capture the behavior of fracture tip region more realistically. A fully coupled poroelastic model for gas reservoirs has been also developed using an innovative numerical technique. From the results of this study it has been found that fracture propagation pressure is higher in poroelastic media compared to that of elastic media. Also high formation permeability (in the direction normal to the hydraulic fracture) and large difference between minimum horizontal stress (in case of it being the smallest principal stress) and reservoir pressure reduce the rate of fracture growth. Besides, high pumping rate is more beneficial in elongating a hydraulic fracture whereas high viscous fracturing fluid is advantageous in widening a hydraulic fracture. It has been also shown that rock deformation, permeability anisotropy and modulus of elasticity can have a significant effect on fluid flow in a hydraulically fractured reservoir. Furthermore, it has been shown that long stress reversal time window and large size of stress reversal region can be caused by high initial pressure differential (i.e. the difference between flowing bottomhole pressure and reservoir pressure), low initial differential stress (i.e. the difference between maximum and minimum horizontal stresses) and low formation permeability in tight gas reservoirs. By taking advantage of production induced change in stress state of a reservoir, this study has also shown that a refracture treatment, if carried out in an optimal time window, can lead to higher economic gain. Besides, analysis of stress reversal region has depicted that a small region with high stress concentration in the vicinity of the wellbore could impede refracture from initiating at the desired place. Moreover, re-pressurization of the wellbore can result in further propagation of the initial fracture before initiation or during propagation of the secondary fracture.

<p>Coal provides for 77% of South Africa&rsquo / s primary energy needs and is therefore a major resource that supports the socio-economic needs of South African citizens. Power stations are the major consumers of coal in South Africa and produces electricity from burned coal. The burning of coal produces a large volume of ash that is disposed in the form of ash dump systems. The ash&nbsp / dump system is treated with high salinity process water from the power station for dust suppression. The process water contains salts due to evaporation processes from the recirculation&nbsp / &nbsp / of&nbsp / water in the cooling water system. Various studies to evaluate the sustainability of the ash dump system as a sustainable salt sink were therefore conducted. This study aimed to develop a conceptual model for the ash dump system by evaluating the movement of the process water trough the ash dump and the impacts it might have on the underlying weathered dolerite aquifer. This was achieved by evaluating the hydraulic and transport properties of the ash dump system. An initial site conceptual model was first established prior to the application of the hydraulic&nbsp / and transport methods. The initial conceptual model was based on the literature, previous reports and an initial site walk over. Known and tested hydraulic and transport methods were applied&nbsp / n bo.th field and laboratory scale for the saturated part of the ash dump system. The laboratory experiments comprised of column and core experiments. These methods assisted in&nbsp / parameter estimation of hydraulic and transport properties and also assisted in the planning of the field experiments. The field experiments were conducted in the form of slug tests, tracer&nbsp / dilution and natural gradient divergent tracer test experiments. The combined laboratory and field experiments provided statistically significant values that were then used as inputs into the&nbsp / conceptual model. Field experiments were also applied to a surrogate aquifer that represented the underlying shallow weathered dolerite aquifer of the ash dump system. The components of&nbsp / the updated conceptual model identified and investigated include the physical environment, the calculated hydraulic and transport properties.The ash dump can be conceptualized as a 20 to&nbsp / &nbsp / 30 meter high heap of consolidated clay size ash&nbsp / particles built on top of an underlying shallow weathered dolerite aquifer. The ash dup is directly connected to the underlying weathered&nbsp / dolerite aquifer. The saline water within the saturated zone has the ability to move through the ash dump system with hydraulic conductivities ranging between 10-1-10- 2 m/day, with flow&nbsp / velocities of 7-8m/day and effective porosities of 1%-2%. The hydraulic properties of the ash dump are, amongst others, controlled by the ash geology, contact time of the process water with the&nbsp / sh and show a significant reduction in hydraulic conductivity over time, before reaching a steady state. The transport properties are controlled by advection and spreading in available&nbsp / pathways. Results for the surrogate underlying fractured rock aquifer show flow velocities of 31m/day and an effective porosity of 1%.This suggests that the underlying weathered dolerite&nbsp / aquifer is vulnerable to process water contamination from the ash dump system. The study illustrates the importance of a site conceptual model before the application of investigative&nbsp / methods. Hence having a site conceptual model provides an excellent platform for hydraulic and transport estimation. The development of a site conceptual model enhanced the&nbsp / understanding of flow and transport movement of the processed&nbsp / water trough the ash dump, it also assisted as a beneficial tool to enhance ash dump management.</p>

A patterned, partially-treed, fen in the mid-boreal region of central Saskatchewan was the site of renewed hydrological research from 2002 to 2004. Hydraulic conductivity, transmissivity, and storativity were determined through use of a surface loading test, pumping tests, and an enclosed field drainage test. None of these field tests have been previously described in the literature as having been used in peat environments. The combined results of field and laboratory drainage tests were used to obtain a general storativity with water table depth relationship in the upper peat layer. The hydraulic conductivity, measured with slug tests, the loading test, and pumping tests, is high near the surface, declining greatly with depth. These previously untested field methods have the advantage of representing volumes of peat from tenths of a meter to cubic meters. </p>Characterization of the hydrology of the peatland involved year round observations of water table, piezometric head, peat surface elevations, frost depth and peat temperatures. Fluctuations of the water table, and soil moisture changes produce changes in effective stress that lead to volume change in the highly compressible peat. This is particularly important for sites with thick peat deposits. Independent compressibility estimates were as high as 10-5 N/m2 in the upper peat. At three fen sites, changes in peat thickness were estimated from monthly estimates of effective stress change, using year round hydrological observations, and compared to measured annual peat thickness changes. Water table changes causing soil moisture changes, and freeze-thaw processes, explained the majority of peat surface movements.

A patterned, partially-treed, fen in the mid-boreal region of central Saskatchewan was the site of renewed hydrological research from 2002 to 2004. Hydraulic conductivity, transmissivity, and storativity were determined through use of a surface loading test, pumping tests, and an enclosed field drainage test. None of these field tests have been previously described in the literature as having been used in peat environments. The combined results of field and laboratory drainage tests were used to obtain a general storativity with water table depth relationship in the upper peat layer. The hydraulic conductivity, measured with slug tests, the loading test, and pumping tests, is high near the surface, declining greatly with depth. These previously untested field methods have the advantage of representing volumes of peat from tenths of a meter to cubic meters. </p>Characterization of the hydrology of the peatland involved year round observations of water table, piezometric head, peat surface elevations, frost depth and peat temperatures. Fluctuations of the water table, and soil moisture changes produce changes in effective stress that lead to volume change in the highly compressible peat. This is particularly important for sites with thick peat deposits. Independent compressibility estimates were as high as 10-5 N/m2 in the upper peat. At three fen sites, changes in peat thickness were estimated from monthly estimates of effective stress change, using year round hydrological observations, and compared to measured annual peat thickness changes. Water table changes causing soil moisture changes, and freeze-thaw processes, explained the majority of peat surface movements.