Computational fluid dynamics (CFD) modelling of critical velocity for sand transport flow regimes in multiphase pipe bends.

The production and transportation of hydrocarbon fluids in multiphase pipelines could be severely hindered by particulate solids deposit - such as the sand particles that can accompany hydrocarbon production. Knowledge of the flow characteristics of solid particles in fluids when transported in pipelines is important, in order to accurately predict solid particle deposition in pipelines. This thesis presents the development of a three-dimensional (3D) computational fluid dynamics (CFD) modelling technique for the prediction of liquid-solids multiphase flow in pipes, with special emphasis on the flow in V-inclined pipe bends. The Euler-Euler (two-fluid) multiphase modelling methodology has been adopted, and the multiphase model equations and closure models describing the liquid-solids flow have been implemented and calculated using the finite volume method in a CFD code software. The liquid phase turbulence has been modelled using a two-equation k - epsilon turbulence model, which contains additional terms to account for the effects of the solid-particles phase on the multiphase turbulence structure. The developed CFD numerical framework has been verified for the relevant forces and all the possible interaction mechanisms of the liquid-solids multiphase flow by investigating four different numerical frameworks, in order to determine the optimum numerical framework that both captures the underlying physics and that also covers the interaction mechanisms leading to sand deposition, and the range of sand transport flow regimes in pipes. The flow of liquid-sand in pipe has been studied extensively, and the numerical results of sand concentration distribution across pipe and other flow properties are in good agreement with published experimental data on validation. The numerical framework has been employed to investigate the multiphase flow in V-inclined pipe bends of ± 4 to 6 degrees, seemingly small inclined bend angles. The predicted results - including the sand segregation, deposition velocity and flow turbulence modulation in the pipe bend - show that the seemingly small pipe bends have a significant effect on the flow, which is different to that of horizontal pipes. The pipe bend causes an abrupt local change in the multiphase flow characteristic and formation of stationary sand deposits in the pipe at a relatively high flow velocity. The threshold velocity to keep sand entrained in liquid in pipe bends is significantly higher than that required for flow horizontal pipes. A critical implication of this is that the correlations for predicting sand deposition in pipelines must account for the effect of pipe bend on flow characteristics in order to provide accurate predictions of the critical sand transport velocity (MTV) in subsea petroleum flowlines, where V-inclined pipe bends are inevitable due to seabed topology

Investigation of sand transport in an undulated pipe using computational fluid dynamics.

A CFD model has been implemented to investigate the effects the pipe undulation on sand transport. Of particular interest of the present study is the sand deposition in small angled V-inclined bend relevant to oil and gas subsea flowlines where sand deposition could be a major problem. The model used is the two-fluid Eulerian-Eulerian model with the granular temperature to tackle the solid phase properties. A number of sub-models for tackling solid-fluid and fluid-fluid interaction has been incorporated in the modelling frame work to capture the transition of flow regimes. The simulation results show that the seemingly small angled V-inclined has significant impact on sand disposition compared to the horizontal section. Sand is deposited at the downstream section of the V-inclined pipe at much higher velocities compared to the minimum transport velocity of the horizontal pipe

Water Supply and Sanitation Challenges in an Urban Setting: A Case Study

Access to clean water, good sanitation services and improved hygiene practices enhance sound health, boost socio-cultural development, and promote economic balance. This study is focused on investigating and identifying the state of water, sanitation and hygiene practices in an urban setting, and proffer solutions to the probable challenges associated with it. Five Local Government areas (LGAs) of Lagos State were selected for this study. The survey involved the use of structured questionnaires administered to randomly selected residents from the LGAs. The Statistical Package for Social Sciences (SPSS) software application and descriptive statistics were used for data analysis. The study reveals that access to water and proper sanitation is insufficient and its services is at high cost to many of the residents who live below the poverty line of less than $2 per day. The supply of water from the water corporation to the local government is not sufficient thereby making many to rely on commercial and private boreholes which often time is expensive. The result also shows that indifferent attitude characterizes poor sanitation which is basically associated with poor maintenance, indiscriminate dumping of refuse in drains and ineffective drainage systems. It is therefore important that sustained cooperation be developed among key actors in order to reduce cost of gaining access to potable water. There should also be continuous sensitization and enlightenment campaigns to the public on the dangers of environmental neglect

Computational fluid dynamic analysis of sand erosion in 90 degree sharp bend geometry.

The prediction of erosion damage due to sand presence during hydrocarbon production is a major threat to the integrity of the production facilities. Sand production from oil and gas reservoirs can cause a significant damage to different pipeline components, and as a consequence, may lead to unwanted maintenance costs and potential environmental damage. In this work, a computational fluid dynamics (CFD) model was developed to investigate how altering flow conditions, pipe geometry and solid particle variables might affect the sand erosion rates at pipe bends. The model was first validated against particle tracks and erosion profiles presented by a published research with reasonable agreement. Erosion rate was found to decrease as the pipe diameter was increased with significant reductions observed when the pipe diameter was increased by the smallest degree (i.e. from 4 to 6). Increasing the bend radii of 1.5D, 3D and 5D also resulted in a gradual decrease in maximum erosion rate observed in each test case respectively. However, it was observed that the surface area damaged by erosion increased as the bend radius was increased. It was found also that increasing particle size results in significantly larger erosion rates with different erosion scarring associated with each particle size. Moreover, no direct correlation was observed between increasing the carrier fluid density and the erosion rate. . However, much larger magnitudes of erosion were observed when gas (low density) was the carrier fluid when compared to oil and water individually. Besides, as expected, erosion rate was found to increase significantly with increase in flow velocity. The final tests conducted were carried out when the distance between two bends in series was increased from 2.5D to 5D and then to 7.5D. Interestingly, erosion was found to increase as the distance between the bends was increased

Water Supply and Sanitation Challenges in an Urban Setting: A Case Study

Access to clean water, good sanitation services and improved hygiene practices enhance sound health, boost socio-cultural development, and promote economic balance. This study is focused on investigating and identifying the state of water, sanitation and hygiene practices in an urban setting, and proffer solutions to the probable challenges associated with it. Five Local Government areas (LGAs) of Lagos State were selected for this study. The survey involved the use of structured questionnaires administered to randomly selected residents from the LGAs. The Statistical Package for Social Sciences (SPSS) software application and descriptive statistics were used for data analysis. The study reveals that access to water and proper sanitation is insufficient and its services is at high cost to many of the residents who live below the poverty line of less than $2 per day. The supply of water from the water corporation to the local government is not sufficient thereby making many to rely on commercial and private boreholes which often time is expensive. The result also shows that indifferent attitude characterizes poor sanitation which is basically associated with poor maintenance, indiscriminate dumping of refuse in drains and ineffective drainage systems. It is therefore important that sustained cooperation be developed among key actors in order to reduce cost of gaining access to potable water. There should also be continuous sensitization and enlightenment campaigns to the public on the dangers of environmental neglect