The thesis deals with the problem of friction during rapid transient 1-D flows in a pipe caused by water hammers. The evolution of the wall shear stress is interpreted in terms of two steps. The first step is the dramatic change of the wall shear stress during the passage of the pressure wave; the corresponding new value of the shear stress is much greater than the value predicted in steady-state. The second step, which begins after the passage of the pressure wave, is a relaxation process; here the shear stress decreases, tending to the new steady-state value corresponding to the new average velocity. The Extended Irreversible Thermodynamics theory is proposed as a tool to model the wall shear stress during the relaxation process. The Friction Relaxation Model presented in this thesis describes both steps of the evolution of the wall shear stress during water hammers, and therefore it enables to take into account the information about the velocity gradient at the wall, which is otherwise not available in 1D modelling.

It is widely known in oil industry that changes in fluid flow conditions such as water breakthrough or unsteady flow due to well shut-in can lead to sand destabilization, with a possible consequent sand production. In this research, different flow situations are incorporated into stress and stability analysis for the region around a wellbore producing oil from weak or unconsolidated sands, and the analyses involve strength weakening, stress redistribution, and decrease of rock stiffness. Two main mechanisms, chemical reactions of rock with formation water and variations of rock capillary strength, are identified and analyzed to study strength weakening after water breakthrough, both qualitatively and quantitatively. Using theories from particle mechanics, rock mechanics, and interfacial science, four novel capillarity models are developed and verified to analytically capture the physical behaviors of capillary strength at the grain scale. Based on model calculations, significantly better understanding of strength behavior in two-phase fluid environments is achieved. Based on a simplified model that can conservatively but efficiently quantify capillary strength with only two input parameters (i. e. particle radius and water saturation), a verified new method that physically calculates pore pressure in a multiphase environment, and a coupled poro-inelastic stress model, the redistributions of effective stresses with water saturation around a wellbore are solved. In terms of stress changes and growth of a plastic radius defining shear-failure zone, the effects of different stability factors, including capillarity through water-oil menisci, pore pressure changes due to the variations of fluid relative permeabilities, and loss of strength through chemical reactions of water-sensitive cementation materials, are quantified and compared in order to clarify when and how they contribute to sand production after water breakthrough. The nonlinearities of rock elastic properties in stressed and biphasic fluid environments is analytically addressed, based on an improved nonlinear theory that considers both a failure-based mechanism and a confining-stress-based mechanism, the strength model, and the coupled stress model. The calculations demonstrate the redistributions of stress-dependent rock stiffness around a wellbore and its evolution with increase of water saturation, clarify the relative importance of each mechanism in reducing rock stiffness, and fundamentally explain why current predictive technologies are invalid when water appears in a flowing wellbore. To quantify the effect of well shut-down on rock stability, the redistributions of fluid pressure in reservoir are analytically solved and coupled with the stress model, while the water hammer equations provide a boundary condition for the bottom-hole pressure. This approach allows direct solution of the relationships among fluid properties, rock properties and production parameters, within the context of rock stability. The proposed new approaches and models can be applied to evaluate sand production risk in multiphase and unsteady fluid flow environment. They can also serve as points of departure to develop more sophisticated models, or to develop more useful constitutive laws for numerical solutions.

It is widely known in oil industry that changes in fluid flow conditions such as water breakthrough or unsteady flow due to well shut-in can lead to sand destabilization, with a possible consequent sand production. In this research, different flow situations are incorporated into stress and stability analysis for the region around a wellbore producing oil from weak or unconsolidated sands, and the analyses involve strength weakening, stress redistribution, and decrease of rock stiffness. Two main mechanisms, chemical reactions of rock with formation water and variations of rock capillary strength, are identified and analyzed to study strength weakening after water breakthrough, both qualitatively and quantitatively. Using theories from particle mechanics, rock mechanics, and interfacial science, four novel capillarity models are developed and verified to analytically capture the physical behaviors of capillary strength at the grain scale. Based on model calculations, significantly better understanding of strength behavior in two-phase fluid environments is achieved. Based on a simplified model that can conservatively but efficiently quantify capillary strength with only two input parameters (i. e. particle radius and water saturation), a verified new method that physically calculates pore pressure in a multiphase environment, and a coupled poro-inelastic stress model, the redistributions of effective stresses with water saturation around a wellbore are solved. In terms of stress changes and growth of a plastic radius defining shear-failure zone, the effects of different stability factors, including capillarity through water-oil menisci, pore pressure changes due to the variations of fluid relative permeabilities, and loss of strength through chemical reactions of water-sensitive cementation materials, are quantified and compared in order to clarify when and how they contribute to sand production after water breakthrough. The nonlinearities of rock elastic properties in stressed and biphasic fluid environments is analytically addressed, based on an improved nonlinear theory that considers both a failure-based mechanism and a confining-stress-based mechanism, the strength model, and the coupled stress model. The calculations demonstrate the redistributions of stress-dependent rock stiffness around a wellbore and its evolution with increase of water saturation, clarify the relative importance of each mechanism in reducing rock stiffness, and fundamentally explain why current predictive technologies are invalid when water appears in a flowing wellbore. To quantify the effect of well shut-down on rock stability, the redistributions of fluid pressure in reservoir are analytically solved and coupled with the stress model, while the water hammer equations provide a boundary condition for the bottom-hole pressure. This approach allows direct solution of the relationships among fluid properties, rock properties and production parameters, within the context of rock stability. The proposed new approaches and models can be applied to evaluate sand production risk in multiphase and unsteady fluid flow environment. They can also serve as points of departure to develop more sophisticated models, or to develop more useful constitutive laws for numerical solutions.

&Ccedil / amlidere Dam supplies significant portion of the potable water demand of the City of Ankara. Consequently, it is very important that the pipelines extending over 60 km between the dam and the treatment plant at Ivedik operate continuously. At present, two composite parallel lines are in operation and construction of a third line is considered for the future. It is the aim of this study to investigate the water hammer problems to be expected under various scenarios and also suggest the safe operation conditions for the system. Water hammer analyses of the pipeline are carried out by computer software named HAMMER. This software employs the Method of Characteristics (MoC) which is a widely used mathematical procedure in solving the non-linear differential equations caused by unsteady flow. Within this theses work, existing tunnels, prestressed concrete and steel pipes, third steel pipeline which is planned to be constructed in the future and existing, and future-planned valves are modeled and calibration of the model is implemented. A plenty of scenarios and valve closure principles are constituted in order to specify steady-state conditions and additional water hammer pressures generated by several excitations through the pipeline. Results of these scenarios are compared with previous works conducted on the pipeline system and the most unfavorable ones among those are determined. Then, appropriate closure durations are identified and suggested for pipe fracture safety valves and the flow control valves at Ivedik in order not to cause excessive pressures in the system.

Hammer Film Production’s brand of melodramatic Gothic Horror reinvented horror cinema in 1957. Despite bringing tremendous financial success throughout the 1950s and 1960s, Hammer’s Gothic had run its course by the early 1970s and cinematic production ceased altogether by 1975. After establishing multiple iterations of a markedly recognizable house style, it is generally agreed that Hammer failed to adapt to the demands of a changing marketplace. This thesis investigates the circumstances surrounding Hammer’s demise by conducting neoformal analysis of case study films and examining how they were affected by cultural, historical, and industrial factors. Looking to Hammer’s films themselves helps determine to what extent they were responsible for Hammer’s misfortune and why. This thesis demonstrates how Hammer’s own production setup and early genre success contributed to the studio’s eventual downfall and the outside factors that underscored this process. I argue that Hammer did experiment with house formula but the studio’s attempts to renegotiate the 1970s horror landscape were unsuccessful because of changing audience demographics, an industry in transition, and Hammer’s own perceived corporate identity. / text

A pressure transient is generated when a sudden change in injection rate occurs due to a valve closure or injector shutdown. This pressure transient, referred to as a water hammer, travels down the wellbore, is reflected back and induces a series of pressure pulses on the sand face. This study presents a semi-analytical model to simulate the magnitude, frequency and duration of water hammer in wellbores. An impedance model has been suggested that can describe the interface, between the wellbore and the formation. Pressure transients measured in five wells in an offshore field are history matched to validate the model. It is shown that the amplitude of the pressure waves may be up to an order of magnitude smaller at the sand face when compared with surface measurements. Finally, a model has been proposed to estimate fracture dimensions from water hammer data. / text

NBG–18 graphite is developed by SGL Carbon for the Pebble Bed Modular Reactor Company (PBMR), and is used as the preferred material for the internal graphite core structures of a high–temperature gas–cooled nuclear reactor (HTR). The NBG–18 graphite is manufactured using pitch coke, and is vibrationally molded. To assess the structural behaviour of graphite many destructive techniques have been performed in the past. Though the destructive techniques are easy and in some cases relative inexpensive to perform, these methods lead to waste material and require cumbersome time consuming sample preparations. To overcome this problem numerous non–destructive testing techniques are available such as sonic resonance, resonant inspection, ultrasonic testing, low and multifrequency Eddy current analysis, acoustic emission and impulse excitation techniques. The Hammer Impulse Excitation technique was used as a method in predicting the fatigue life of NBG–18 graphite by focussing on the application of modal frequency analysis of determined natural frequencies. Moreover, the typical fatigue characteristics of NBG–18 graphite were determined across a comprehensive set of load ranges. In order to be able to correlate modal frequency parameters with fatigue life, suitable uniaxial fatigue test specimen geometry needed to be obtained. The uniaxial fatigue test specimens were manufactured from two NBG–18 graphite sample blocks. The relationship between natural frequencies of uniaxial test specimens, fatigue life, sample positioning and sample orientation was investigated for different principle stress ratios. Load ratios R = –oo and R = +2 tested proved to show the highest r–values for the Pearson correlation coefficients investigated. However, there was no significant trend found between the natural frequency and the fatigue life. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

NBG–18 graphite is developed by SGL Carbon for the Pebble Bed Modular Reactor Company (PBMR), and is used as the preferred material for the internal graphite core structures of a high–temperature gas–cooled nuclear reactor (HTR). The NBG–18 graphite is manufactured using pitch coke, and is vibrationally molded. To assess the structural behaviour of graphite many destructive techniques have been performed in the past. Though the destructive techniques are easy and in some cases relative inexpensive to perform, these methods lead to waste material and require cumbersome time consuming sample preparations. To overcome this problem numerous non–destructive testing techniques are available such as sonic resonance, resonant inspection, ultrasonic testing, low and multifrequency Eddy current analysis, acoustic emission and impulse excitation techniques. The Hammer Impulse Excitation technique was used as a method in predicting the fatigue life of NBG–18 graphite by focussing on the application of modal frequency analysis of determined natural frequencies. Moreover, the typical fatigue characteristics of NBG–18 graphite were determined across a comprehensive set of load ranges. In order to be able to correlate modal frequency parameters with fatigue life, suitable uniaxial fatigue test specimen geometry needed to be obtained. The uniaxial fatigue test specimens were manufactured from two NBG–18 graphite sample blocks. The relationship between natural frequencies of uniaxial test specimens, fatigue life, sample positioning and sample orientation was investigated for different principle stress ratios. Load ratios R = –oo and R = +2 tested proved to show the highest r–values for the Pearson correlation coefficients investigated. However, there was no significant trend found between the natural frequency and the fatigue life. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

Thesis (M.A.)--Carleton University, 2002. / Includes bibliographical references (p. 122-129). Also available in electronic format on the Internet.

Submitted by MARCOS JORGE ASSUMPÇÃO SCHIMIDT null (mschimidt@sabesp.com.br) on 2016-06-27T21:35:16Z No. of bitstreams: 1 DISSERTAÇÃO CD.pdf: 10677692 bytes, checksum: 787b589f9accd5975edca6f4b2bb6868 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-06-29T14:13:24Z (GMT) No. of bitstreams: 1 schimidt_mja_me_bot.pdf: 10677692 bytes, checksum: 787b589f9accd5975edca6f4b2bb6868 (MD5) / Made available in DSpace on 2016-06-29T14:13:24Z (GMT). No. of bitstreams: 1 schimidt_mja_me_bot.pdf: 10677692 bytes, checksum: 787b589f9accd5975edca6f4b2bb6868 (MD5) Previous issue date: 2016-05-02 / O abastecimento público é um dos grandes desafios das autoridades em prover a sociedade com água de qualidade e em quantidade. O aumento da demanda por este recurso natural exige projetos de captação e transporte cada vez maiores e mais complexos. Um projeto hidráulico deve ser concebido para operar sob condições normais de escoamento e também sob condições extremas, causadas por agentes externos que possam gerar pressões muito maiores ou muito menores às condições ideais de funcionamento. Este trabalho teve por objetivos definir o desenho de bombeamento público para o abastecimento da cidade de Torrinha, município do Estado de São Paulo; determinar qual alternativa de combinação de tubulações é a melhor solução hidráulica e econômica; e verificar a necessidade e definir a proteção contra transiente hidráulico. Utilizou-se o programa Allievi para realizar as cinco simulações propostas: Simulação 1 (S1): regime permanente; Simulação 2 (S2): linha com tubos de ferro fundido sem proteção; Simulação 3 (S3): linha com tubos de PVC-O sem proteção; Simulação 4 (S4): linha com tubos de PVC-O com proteção; Simulação 5 (S5): linha com tubos de ferro fundido e de PVC-12 DeFoFo com proteção. A partir dos resultados concluiu-se que na simulação 5 obteve-se a melhor opção econômica e hidráulica, consistindo em construir a linha com os primeiros 3391,79 metros de tubos de ferro fundido, ponta bolsa, K7 e 3297,33 metros restantes com tubos de PVC 12 DeFoFo; e a utilização do dispositivo RHO com bexiga de 1,5 m³ de capacidade para proteção contra transiente hidráulico. As simulações S2 e S3 evidenciaram um ganho de rendimento do grupo motobomba e a opção S1 é a que mostrou a melhor combinação vazão-altura. / Provide good quality water besides following the public demand is one of the biggest challenges faced for the authorities these days, the increasing demand for this natural resource requires larger and more complexes abduction systems and distribution networks. Moreover, hydraulics projects should be projected to work at normal flow conditions but also at extreme conditions caused by external agents whom can produce much bigger or much lower pressures comparing with a ideal operation condition. The current research aim to define a pumping project for the public supply of the city of Torrinhas in estate of São Paulo, establishing the most efficient combination of pipelines to attend the economic and hydraulics necessities, besides define the necessity and the protection against the hydraulics transient. The research was conducted using the Allievi software to simulate five proposed settings: Simulation 1 (S1): Steady state; Simulation 2 (S2): Pipeline with cast iron pipes without protection; Simulation 3 (S3): Pipeline with PVC-O pipes without protection; Simulation 4 (S4): pipeline with PVC-O pipes with protection; Simulation 5 (S5): pipeline with cast iron and PVC-12 DeFoFo pipes with protection. Therefore, with the present results was possible to conclude that the best economic and hydraulic option is to use cast iron hub pipes K7 in the first 3391.79 meters, and use PVC 12 DeFoFo pipes in the others 3297.33 meters, and also the utilization of the Balloon Hydro pneumatic Accumulator device with 1,5m³ of capability to guard the system against the hydraulic transient. The settings S2 and S3 showed gains in the pump group yield while the setting S1 had the best relation between flow rate and elevation.