The effects of bubbles on a jet issued below and parallel to a free surface are experimentally studied. The jet under study is isothermal and in fresh water, with air injectors that allow variation of the inlet air volume fraction for 0% to 13%. Measurements of the jet exit conditions, water velocity, water entrainment, Reynolds stresses and surface currents have been performed using LDV, PIV and surface PIV. Air volume fraction, bubble velocity, chord length and free surface elevation and RMS have been obtained using local phase detection probes. Visualization was performed using laser-induced fluorescence. Measurements show that water entrainment decreases up to 22% with the presence of bubbles, but surface current strength increases up to 60% with 0.4 l/min of air injection. The mean free surface elevation and turbulent fluctuation significantly increase with the injection of air. The water normal Reynolds stresses are damped by the presence of bubbles in the bulk of the liquid, but very close to the free surface the effect is reversed and the normal Reynolds stresses increase slightly for the bubbly flow. Flow visualizations show that the two-phase jet is lifted with the presence of bubbles and attaches to the free surface sooner. Significant bubble coalescence is observed, leading to an increase of 20% in mean bubble size as the jet develops. The coalescence near the free surface is particularly strong, due to the time it takes the bubbles to pierce the free surface, resulting in a considerable increase in the local air volume fraction.

The development of a cost-effective multiphase flow meter to determine the individual phase flow rates of oil, water and gas was investigated through the exploitation of a single clamp-on gamma densitometer and signal processing techniques. A fast-sampling (250 Hz) gamma densitometer was installed at the top of the 10.5 m high, 108.2 mm internal diameter, stainless steel catenary riser in the Cranfield University multiphase flow test facility. Gamma radiation attenuation data was collected for two photon energy ranges of the caesium-137 radioisotope based densitometer for a range of air, water and oil flow mixtures, spanning the facility’s delivery range. Signal analysis of the gamma densitometer data revealed the presence of quasi-periodic waveforms in the time-varying multiphase flow densities and discriminatory correlations between statistical features of the gamma count data and key multiphase flow parameters. The development of a mechanistic approach to infer the multiphase flow rates from the gamma attenuation information was investigated. A model for the determination of the individual phase flow rates was proposed based on the gamma attenuation levels; while quasi-periodic waveforms identified in the multiphase fluid density were observed to exhibit a strong correlation with the gas and liquid superficial phase velocity parameters at fixed water cuts. Analysis of the use of pattern recognition techniques to correlate the gamma densitometer data with the individual phase superficial velocities and the water cut was undertaken. Two neural network models were developed for comparison: a single multilayer-perceptron and a multilayer hierarchical flow regime dependent model. The pattern recognition systems were trained to map the temporal fluctuations in the multiphase mixture density with the individual phase flow rates using statistical features extracted from the gamma count signals as their inputs. Initial results yielded individual phase flow rate predictions to within ±10% based on flow regime specific correlations.

Supersaturated water injection (SWI) is a novel remediation technology which is able to remove entrapped residual NAPLs from saturated porous media by both volatilization (partitioning of volatile contaminants into the gas phase) and mobilization (displacement of isolated NAPL residuals by gas clusters). The character of gas saturation evolution in-situ in saturated porous media during SWI results in high sweep efficiency. This work focuses on studying the recovery of entrapped residual NAPL by the mobilization mechanism during SWI, thus low-volatility NAPL residuals, kerosene and a kerosene-hexadecane mixture, are used as contaminants. A series of SWI recovery experiments are conducted to investigate the influence of grain size, low-permeability layering, and physical properties of the contaminants on the recovery behavior. For columns contaminated with kerosene, the residual saturation can be reduced to around 4% from an initial value of 16%, and over 70% of the residual kerosene is recovered by a combination of mobilization and volatilization in homogeneous sand packs. For columns contaminated with a kerosene-hexadecane mixture, the final residual saturation is 7.4% and the final NAPL recovery is lower than that in kerosene columns. Grain size has little influence on NAPL recovery, but low permeability layering has a significantly negative influence. Experiments designed to compare SWI to sparging, and water-gas co-injection showed that water-gas co-injection was able to effectively recovery residual NAPLs albeit not as efficiently as SWI, while steady gas sparging is completely ineffective at recovering residual NAPL by mobilization. Based on these experimental observations, a conceptual model, involving double displacements and NAPL bank formation, is purposed to explain the experimental observations.

Water-in-oil (W/O) emulsions consist of water droplets dispersed in continuous oil phase. They are encountered at various stages of oil production. The oil produced from an oil-well usually carries a significant amount of water in the form of droplets. In enhanced oil recovery techniques involving the injection of polymer solution, the aqueous phase of the water-in-oil emulsions produced from the oil well consists of polymeric additive. A good understanding of the flow behavior of emulsions in pipelines is essential for the design and operation of oil production-gathering facilities and emulsion pipelines. A number of studies have been reported on simultaneous flow of oil and water in pipelines. However, the studies reported in the literature are mainly focused on either oil-water flow patterns and separated flows (annular and stratified flow of oil and water phases) or oil-in-water (O/W) emulsion flows. The pipeline flow of water-in-oil (W/O) emulsions has received less attention. Also, little work has been carried out on the effect of additives such as polymer. In this study, new experimental results are presented on the pipeline flow behavior of water-in-oil (W/O) emulsions, with and without the presence of polymeric additive in the aqueous phase. The emulsions were prepared from three different oils, namely EDM-244, EDM-Monarch, and Shell Pella of different viscosities (2.5 mPa.s for EDM-244, 6 mPa.s for EDM-Monarch, and 5.4 mPa.s for Shell Pella, at 25 0C). The water-in-oil emulsions prepared from EDM-244 and EDM-Monarch (without any polymeric additive in the dispersed aqueous phase) exhibited drag reduction behavior in turbulent flow. The turbulent friction factor data of the emulsions fell well below the standard Blasius equation for smooth pipes. The water-in-oil emulsions prepared from EDM-244 exhibited stronger drag reduction as compared with the EDM-Monarch emulsions. The Shell Pella emulsions (w/o type) did not exhibit any drag reduction in turbulent flow; the friction factor data followed the Blasius equation. The Shell Pella emulsions were more stable than the EDM-244 and EDM-Monarch emulsions. When left unstirred, the EDM-244 and EDM-Monarch emulsions quickly coalesced into separate oil and water phases whereas the Shell Pella emulsions took significantly longer time to separate into oil and water phases. The Shell Pella oil emulsions were also milkier than the EDM emulsions. The addition of polymer to the dispersed aqueous phase of water-in-oil emulsions had a significant effect on the turbulent drag reduction behavior. Emulsions were less drag reducing when polymer was present in the aqueous droplets. The effect of surfactant on the pipeline flow behavior of water/oil emulsions was also investigated. The surfactant-stabilized water-in-oil emulsions followed the single phase flow behavior. The presence of surfactant in the emulsions caused the dispersed droplets to become significantly smaller. It is believed that the droplets were smaller than the scale of turbulence when surfactant was present and consequently no drag reduction was observed.

Supersaturated water injection (SWI) is a novel remediation technology which is able to remove entrapped residual NAPLs from saturated porous media by both volatilization (partitioning of volatile contaminants into the gas phase) and mobilization (displacement of isolated NAPL residuals by gas clusters). The character of gas saturation evolution in-situ in saturated porous media during SWI results in high sweep efficiency. This work focuses on studying the recovery of entrapped residual NAPL by the mobilization mechanism during SWI, thus low-volatility NAPL residuals, kerosene and a kerosene-hexadecane mixture, are used as contaminants. A series of SWI recovery experiments are conducted to investigate the influence of grain size, low-permeability layering, and physical properties of the contaminants on the recovery behavior. For columns contaminated with kerosene, the residual saturation can be reduced to around 4% from an initial value of 16%, and over 70% of the residual kerosene is recovered by a combination of mobilization and volatilization in homogeneous sand packs. For columns contaminated with a kerosene-hexadecane mixture, the final residual saturation is 7.4% and the final NAPL recovery is lower than that in kerosene columns. Grain size has little influence on NAPL recovery, but low permeability layering has a significantly negative influence. Experiments designed to compare SWI to sparging, and water-gas co-injection showed that water-gas co-injection was able to effectively recovery residual NAPLs albeit not as efficiently as SWI, while steady gas sparging is completely ineffective at recovering residual NAPL by mobilization. Based on these experimental observations, a conceptual model, involving double displacements and NAPL bank formation, is purposed to explain the experimental observations.

Water-in-oil (W/O) emulsions consist of water droplets dispersed in continuous oil phase. They are encountered at various stages of oil production. The oil produced from an oil-well usually carries a significant amount of water in the form of droplets. In enhanced oil recovery techniques involving the injection of polymer solution, the aqueous phase of the water-in-oil emulsions produced from the oil well consists of polymeric additive. A good understanding of the flow behavior of emulsions in pipelines is essential for the design and operation of oil production-gathering facilities and emulsion pipelines. A number of studies have been reported on simultaneous flow of oil and water in pipelines. However, the studies reported in the literature are mainly focused on either oil-water flow patterns and separated flows (annular and stratified flow of oil and water phases) or oil-in-water (O/W) emulsion flows. The pipeline flow of water-in-oil (W/O) emulsions has received less attention. Also, little work has been carried out on the effect of additives such as polymer. In this study, new experimental results are presented on the pipeline flow behavior of water-in-oil (W/O) emulsions, with and without the presence of polymeric additive in the aqueous phase. The emulsions were prepared from three different oils, namely EDM-244, EDM-Monarch, and Shell Pella of different viscosities (2.5 mPa.s for EDM-244, 6 mPa.s for EDM-Monarch, and 5.4 mPa.s for Shell Pella, at 25 0C). The water-in-oil emulsions prepared from EDM-244 and EDM-Monarch (without any polymeric additive in the dispersed aqueous phase) exhibited drag reduction behavior in turbulent flow. The turbulent friction factor data of the emulsions fell well below the standard Blasius equation for smooth pipes. The water-in-oil emulsions prepared from EDM-244 exhibited stronger drag reduction as compared with the EDM-Monarch emulsions. The Shell Pella emulsions (w/o type) did not exhibit any drag reduction in turbulent flow; the friction factor data followed the Blasius equation. The Shell Pella emulsions were more stable than the EDM-244 and EDM-Monarch emulsions. When left unstirred, the EDM-244 and EDM-Monarch emulsions quickly coalesced into separate oil and water phases whereas the Shell Pella emulsions took significantly longer time to separate into oil and water phases. The Shell Pella oil emulsions were also milkier than the EDM emulsions. The addition of polymer to the dispersed aqueous phase of water-in-oil emulsions had a significant effect on the turbulent drag reduction behavior. Emulsions were less drag reducing when polymer was present in the aqueous droplets. The effect of surfactant on the pipeline flow behavior of water/oil emulsions was also investigated. The surfactant-stabilized water-in-oil emulsions followed the single phase flow behavior. The presence of surfactant in the emulsions caused the dispersed droplets to become significantly smaller. It is believed that the droplets were smaller than the scale of turbulence when surfactant was present and consequently no drag reduction was observed.

In this thesis, a reduced order model (ROM) based on the proper orthogonal decomposition (POD) for the transport phenomena in fluidized beds has been developed. The reduced order model is tested first on a gas-only flow. Two different strategies and implementations are described for this case. Next, a ROM for a two-dimensional gas-solids fluidized bed is presented. A ROM is developed for a range of diameters of the solids particles. The reconstructed solution is calculated and compared against the full order solution. The differences between the ROM and the full order solution are smaller than 3.2% if the diameters of the solids particles are in the range of diameters used for POD database generation. Otherwise, the errors increase up to 10% for the cases presented herein. The computational time of the ROM varied between 25% and 33% of the computational time of the full order solution. The computational speed-up depended on the complexity of the transport phenomena, ROM methodology and reconstruction error. In this thesis, we also investigated the accuracy of the reduced order model based on the POD. When analyzing the accuracy, we used two simple sets of governing partial differential equations: a non-homogeneous Burgers' equation and a system of two coupled Burgers' equations.

The development of a cost-effective multiphase flow meter to determine the individual phase flow rates of oil, water and gas was investigated through the exploitation of a single clamp-on gamma densitometer and signal processing techniques. A fast-sampling (250 Hz) gamma densitometer was installed at the top of the 10.5 m high, 108.2 mm internal diameter, stainless steel catenary riser in the Cranfield University multiphase flow test facility. Gamma radiation attenuation data was collected for two photon energy ranges of the caesium-137 radioisotope based densitometer for a range of air, water and oil flow mixtures, spanning the facility’s delivery range. Signal analysis of the gamma densitometer data revealed the presence of quasi-periodic waveforms in the time-varying multiphase flow densities and discriminatory correlations between statistical features of the gamma count data and key multiphase flow parameters. The development of a mechanistic approach to infer the multiphase flow rates from the gamma attenuation information was investigated. A model for the determination of the individual phase flow rates was proposed based on the gamma attenuation levels; while quasi-periodic waveforms identified in the multiphase fluid density were observed to exhibit a strong correlation with the gas and liquid superficial phase velocity parameters at fixed water cuts. Analysis of the use of pattern recognition techniques to correlate the gamma densitometer data with the individual phase superficial velocities and the water cut was undertaken. Two neural network models were developed for comparison: a single multilayer-perceptron and a multilayer hierarchical flow regime dependent model. The pattern recognition systems were trained to map the temporal fluctuations in the multiphase mixture density with the individual phase flow rates using statistical features extracted from the gamma count signals as their inputs. Initial results yielded individual phase flow rate predictions to within ±10% based on flow regime specific correlations.

Geological carbon dioxide (CO₂) capture and storage in geological formations has the potential to reduce anthropogenic emissions. The viability of technology depends on the long-term security of the geological CO₂ storage. Dissolution of CO₂ into the brine, resulting in stable stratification, has been identified as the key to long-term storage security. The dissolution rate determined by convection in the brine is driven by the increase of brine density with CO₂ saturation. Here we present a new analog laboratory experiment system to characterize convective dissolution in homogeneous porous medium. By understanding the relationship between dissolution and the Rayleigh number in homogeneous porous media, we can evaluate if convective dissolution occurs in the field and, in turn, to estimate the security of geological CO₂ storage fields. The large experimental assembly will allow us to quantify the relationship between convective dynamics and the Rayleigh number of the system, which could be essential to trapping process at Bravo Dome. A series of pictures with high resolution are taken to show the existence and movement of fingers of analog fluid. Also, these pictures are processed, clearly showed the concentration of analog fluid, which is essential to analyze the convective dissolution in detail. We measured the reduction in the convective flux due to hydraulic dispersion effect compared to that in homogeneous media, to determine if convective dissolution is an important trapping process at Bravo Dome. / text

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