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In the flow distribution section of a paper machine, known as the head box, water is injected into the fiber suspension (stock) flow through a tee-mixer for more uniform production. This dilution process has two important requirements that must be fulfilled: (1) sufficient mixing so that the dilution flow spreads across the suspension flow and (2) that the injection flow rate not be so large to significantly alter the local head box flow rate. The objective of this research was to find a combination of velocity ratio and tee mixer geometry that lead to the injection flow being well mixed into the stock flow, but at the same time, the injection should not cause the total flow rate to change by more than 1%. Velocity ratios of 0.25, 0.75, 1.33, 1.5 and 2.25 were examined for four different cases of tee mixer geometries using the CFD software Fluent. Two of the cases had added contractions located near the injection point, while the other two cases had a more standard geometry with no added complexities. The pressure drop across the injection point was also measured. Mixing was qualitatively measured by simulating the injection of a passive tracer into the dilution flow. All of the results indicated that the case where the contraction was located after the injection showed the most promising results with quality mixing and lower flow rates. The cases without added contractions showed poor mixing for lower velocity ratios, and for higher velocity ratios, the flow rates were too large. The cases with contractions showed similar mixing, but the outlet flow rates produced were lower when the contraction was located after the injection instead of before it. A velocity ratio of 0.25-0.75 for the mixers with contractions produced acceptable flow rates and sufficient mixing. The simulations also showed that the static pressure for the contraction cases were nearly identical throughout the majority of the pipe. For both contraction cases the pressure drop across the injection increased with increasing injection flow rate. When the contraction was located before the injection, a pressure drop of 16% was calculated. A pressure drop of 18% to 20% across the injection resulted when the contraction was located after the injection.

Richtmyer-Meshkov instability is studied in shock tube experiments with an Atwood number of 0.7. The interface is formed in a vertical shock tube using opposed gas flows, and three-dimensional random initial interface perturbations are generated by the vertical oscillation of gas column producing Faraday waves. Planar Laser Mie scattering is used for flow visualization and for measurements of the mixing process. Experimental image sequences are recorded at 6 kHz frequency and processed to obtain the time dependent variation of the integral mixing layer width. Measurements of the mixing layer width are compared with Mikaelian's [1] model in order to extract the growth exponent. where a fairly wide range of values is found varying from theta approximate to 0.2 to 0.6.

The flow distribution in the primary circuit of the pressurized water reactor was studied with experiments and Computational Fluid Dynamics (CFD) simulations. The main focus was on the flow field and mixing in the downcomer of the pressure vessel: how the different factors like the orientation of operating loops, the total loop flow rate and the asymmetry of the loop flow rates affect the outcome. In addition to the flow field studies the overall applicability of CFD methods for primary circuit thermal-hydraulic analysis was evaluated based on the CFD simulations of the mixing experiments of the ROCOM (Rossendorf Coolant Mixing Model) test facility and the mixing experiments of the Paks NPP. The experimental part of the work in work package 3 included series of steady state mixing experiments with the ROCOM test facility and the publication of results of Paks VVER-440 NPP thermal mixing experiments. The ROCOM test facility models a 4-loop KONVOI type reactor. In the steady-state mixing experiments the velocity field in the downcomer was measured using laser Doppler anemometry and the concentration of the tracer solution fed from one loop was measured at the downcomer and at the core inlet plane. The varied parameters were the number and orientation of the operating loops, the total flow rate and the (asymmetric) flow rate of individual loops. The Paks NPP thermal mixing experiments took place during commissioning tests of replaced steam generator safety valves in 1987-1989. It was assumed that in the reactor vessels of Paks VVER-440 NPP equipped with six loops the mixing of the coolant is not ideal. For the realistic determination of the active core inlet temperature field for the transients and accidents associated with different level temperature asymmetry a set of mixing factors were determined. Based on data from the online core monitoring system and a separate mathematical model the mixing factors for loop flows at the core inlet were determined. In the numerical simulation part of the work package 3 the detailed measurements of ROCOM tests were used for the validation of CFD methods for primary circuit studies. The selected steady state mixing experiments were simulated with CFD codes CFX-4, CFX-5 and FLUENT. The velocity field in the downcomer and the mixing of the scalar were compared between CFD simulations and experiments. The CFD simulations of full scale PWR included the simulation of Paks VVER-440 mixing experiment and the simulation of Loviisa VVER-440 downcomer flow field. In the simulations of Paks experiments the experimental and simulated concentration field at the core inlet were compared and conclusions made concerning the results overall and the VVER-440 specific geometry modelling aspects like how to model the perforated elliptic bottom plate and what is the effect of the cold leg bends to the flow field entering to the downcomer. With Loviisa simulations the qualitative comparison was made against the original commissioning experiments but the emphasis was on the CFD method validation and testing. The overall conclusion concerning the CFD modelling of the flow field and mixing in the PWR primary circuit could be that the current computation capacity and physical models also in commercial codes is beginning to be sufficient for simulations giving reliable and useful results for many real primary circuit applications. However the misuse of CFD methods is easy, and the general as well as the nuclear power specific modelling guidelines should be followed when the CFD simulations are made.

The flow distribution in the primary circuit of the pressurized water reactor was studied with experiments and Computational Fluid Dynamics (CFD) simulations. The main focus was on the flow field and mixing in the downcomer of the pressure vessel: how the different factors like the orientation of operating loops, the total loop flow rate and the asymmetry of the loop flow rates affect the outcome. In addition to the flow field studies the overall applicability of CFD methods for primary circuit thermal-hydraulic analysis was evaluated based on the CFD simulations of the mixing experiments of the ROCOM (Rossendorf Coolant Mixing Model) test facility and the mixing experiments of the Paks NPP. The experimental part of the work in work package 3 included series of steady state mixing experiments with the ROCOM test facility and the publication of results of Paks VVER-440 NPP thermal mixing experiments. The ROCOM test facility models a 4-loop KONVOI type reactor. In the steady-state mixing experiments the velocity field in the downcomer was measured using laser Doppler anemometry and the concentration of the tracer solution fed from one loop was measured at the downcomer and at the core inlet plane. The varied parameters were the number and orientation of the operating loops, the total flow rate and the (asymmetric) flow rate of individual loops. The Paks NPP thermal mixing experiments took place during commissioning tests of replaced steam generator safety valves in 1987-1989. It was assumed that in the reactor vessels of Paks VVER-440 NPP equipped with six loops the mixing of the coolant is not ideal. For the realistic determination of the active core inlet temperature field for the transients and accidents associated with different level temperature asymmetry a set of mixing factors were determined. Based on data from the online core monitoring system and a separate mathematical model the mixing factors for loop flows at the core inlet were determined. In the numerical simulation part of the work package 3 the detailed measurements of ROCOM tests were used for the validation of CFD methods for primary circuit studies. The selected steady state mixing experiments were simulated with CFD codes CFX-4, CFX-5 and FLUENT. The velocity field in the downcomer and the mixing of the scalar were compared between CFD simulations and experiments. The CFD simulations of full scale PWR included the simulation of Paks VVER-440 mixing experiment and the simulation of Loviisa VVER-440 downcomer flow field. In the simulations of Paks experiments the experimental and simulated concentration field at the core inlet were compared and conclusions made concerning the results overall and the VVER-440 specific geometry modelling aspects like how to model the perforated elliptic bottom plate and what is the effect of the cold leg bends to the flow field entering to the downcomer. With Loviisa simulations the qualitative comparison was made against the original commissioning experiments but the emphasis was on the CFD method validation and testing. The overall conclusion concerning the CFD modelling of the flow field and mixing in the PWR primary circuit could be that the current computation capacity and physical models also in commercial codes is beginning to be sufficient for simulations giving reliable and useful results for many real primary circuit applications. However the misuse of CFD methods is easy, and the general as well as the nuclear power specific modelling guidelines should be followed when the CFD simulations are made.

<div>Global warming is considered to result from excessive emission of CO₂ caused by human activity. The security of long term CO₂ capture and sequestration on the subsurface depends on the integrity of caprocks. Natural and engineered subsurface activities can generate fractures in caprocks that can lead to CO₂ leakage. Reactive fluids that flow through a fracture may seal a fracture through mineral precipitation or open a fracture through dissolution. It is extremely useful to CO₂ storage to understand the behavior of reactive fluids that generates mineral precipitation that can seal a fracture. Experiments on non-reactive and reactive fluid mixing were performed to explore gravity-driven chemical dynamics that control the mixing and spatial distribution of mineral precipitates. Fracture inclination, fracture apertures, fluid pumping rates, and density contrasts between fluids were studied for their effects on fluid mixing. From non-reactive fluid mixing experiments, a less dense fluid was found to be confined to a narrow path (runlet) by the denser fluid under the influence of gravity. Fracture inclination angle affected the shape of the less dense fluid runlet. As the angle of inclination decreased, the area of the less dense runlet increased. Improved mixing and a potentially larger area of precipitation formation will occur during reactive fluid mixing when the fracture plane is perpendicular to gravity. Fracture aperture affected the time evolution of the mixing of the fluids, while pumping rate affected fluid mixing by controlling the relative velocities between the two fluids. The fact that the spatial distribution of the two fluids, instead of the fracture roughness, dominated the fluid mixing sheds light on the potential behaviors of reactive fluids mixing in fractures. The location for the majority of precipitation formation and the transport of precipitates can be accordingly predicted from knowledge of the properties of the two reactive fluids and the orientation of the fracture.</div><div>From a small study on wave propagation across fractures with precipitates, simulation results showed that the impedance difference between the matrix material and the precipitate affects the transmitted signal amplitude. Both the aperture and fraction of aperture filled with precipitates affect signal amplitude.</div><div><br></div>

Análises estruturais, petrográficas e de inclusões fluidas são apresentadas para os veios quartzo auríferos da mina Morro do Ouro, Cinturão Ribeira, sudeste do Brasil. A mineralização de ouro em veios de quartzo está hospedada em rochas metassedimentares de baixo grau metamórfico de idade calimiana, que também apresenta uma mineralização aurífera singenética. Dois sistemas de veios de quartzo auríferos estão presentes: (i) veios NW extensionais subverticais e (ii) veios NE subverticais paralelos ao plano axial da dobras apertadas. Os veios mineralizados são adjacentes a uma falha principal de alto ângulo, cujas relações estruturais indicam orientação desfavorável para reativação friccional. Os veios NW apresentam inclusões fluidas dos sistemas \'CO IND.2\'-\'CH IND.4\' e H2O-CO2-\'CH IND.4\'-NaCl-\'CaCl IND.2\' com salinidades variáveis (4 a 52% em peso NaCl equivalente), que apresentam evidências de aprisionamento envolvendo os processos de imiscibilidade de fluidos e mistura de fluidos com composições contrastantes. Os veios NE apresentam inclusões fluidas do sistema H2O-CO2-\'CH IND.4\'-\'N IND.2\'-NaCl-\'CaCl IND.2\' com salinidades variáveis (5 a 45% em peso NaCl equivalente). O aprisionamento dos fluidos ocorreu em temperaturas entre 225 e 240°C para os veios NW, e aproximadamente 208°C para os veios NE, envolvendo processos de imiscibilidade e mistura de fluidos de composições distintas. Os veios extensionais NW foram formados sob flutuação de pressão com valores litostáticos a supralitostáticos (125-240 MPa) durante o estágio de fraturamento pré-sismico. Os veios subverticais NE precipitaram dominantemente sob condições de pressão próximas a valores hidrostáticos (10-70 MPa), posteriormente à redistribuição de fluidos de diferentes reservatórios ao longo da zona de ruptura sísmica. Os fluidos hidrotermais foram provavelmente enriquecidos em ouro devido à interação com as rochas encaixantes e a precipitação do minério é atribuída a mudanças nas propriedades físico-químicas em resposta à imiscibilidade de fluidos aliada à mistura de fluidos com salinidades fortemente contrastantes. Estes processos ocorreram como consequência de flutuações cíclicas na pressão de fluidos, bem como de variações no regime de esforços tectônicos associados a episódios de atividade sísmica em zonas de falha. / Fluid inclusion, petrographic and structural analyses are presented for auriferous veins from the Morro do Ouro Mine, Ribeira Belt, southeastern Brazil. The vein-type Au mineralization at the mine is restricted to structurally-controlled domains in a low-grade Calymmian metassedimentary sequence that host also syngenetic Au mineralization. Two auriferous quartz vein systems are present: (i) NW-trending subvertical extensional veins and (ii) ENE-trending subvertical veins parallel to the axial surface of tight folds. The mineralized veins are adjacent to a major dextral transcurrent fault zone and their structural relationships indicate that this fault is severely misoriented for frictional reactivation. The NW-trending veins present a fluid inclusion assemblage dominated by CO2-\'CH IND.4\' inclusions and H2O-CO2-\'CH IND.4\'-\'N IND.2\'-NaCl-\'CaCl IND.2\' inclusions of highly contrasting salinities (4 to 52 wt. % NaCl equivalent) and the NE-trending veins present fluid inclusion assemblage dominated by H2O-CO2-\'CH IND.4\'-\'N IND.2\'-NaCl-\'CaCl IND.2\' inclusions of contrasting salinities (4 to 45 wt. % NaCl equivalent). The entrapment of fluids occurred at temperatures between 225 and 240ºC in NW-trending veins and approximately 208ºC in NE-trending veins, involving processes of fluid immiscibility and mixing between fluids of contrasting compositions. NW-trending extensional veins were formed dominantly under pressure fluctuating between near-lithostatic to strongly supralithostatic values (125-240 MPa) during pre-seismic failure stages. ENE-trending veins precipitated dominantly under near-hydrostatic pressure conditions (10-70 MPa), following discharge of fluids from different reservoirs along the ruptured zone after earthquake rupture stages. The hydrothermal fluids were probably enriched in gold through interaction with the host rocks and its precipitation is attributed to changes of physicochemical properties due to fluid immiscibility and mixing between fluids of highly contrasting salinites, as a consequence of cyclic fluctuations in the values of fluid pressure and tectonic stresses accompanying episodes of seismogenic fault activity.

Análises estruturais, petrográficas e de inclusões fluidas são apresentadas para os veios quartzo auríferos da mina Morro do Ouro, Cinturão Ribeira, sudeste do Brasil. A mineralização de ouro em veios de quartzo está hospedada em rochas metassedimentares de baixo grau metamórfico de idade calimiana, que também apresenta uma mineralização aurífera singenética. Dois sistemas de veios de quartzo auríferos estão presentes: (i) veios NW extensionais subverticais e (ii) veios NE subverticais paralelos ao plano axial da dobras apertadas. Os veios mineralizados são adjacentes a uma falha principal de alto ângulo, cujas relações estruturais indicam orientação desfavorável para reativação friccional. Os veios NW apresentam inclusões fluidas dos sistemas \'CO IND.2\'-\'CH IND.4\' e H2O-CO2-\'CH IND.4\'-NaCl-\'CaCl IND.2\' com salinidades variáveis (4 a 52% em peso NaCl equivalente), que apresentam evidências de aprisionamento envolvendo os processos de imiscibilidade de fluidos e mistura de fluidos com composições contrastantes. Os veios NE apresentam inclusões fluidas do sistema H2O-CO2-\'CH IND.4\'-\'N IND.2\'-NaCl-\'CaCl IND.2\' com salinidades variáveis (5 a 45% em peso NaCl equivalente). O aprisionamento dos fluidos ocorreu em temperaturas entre 225 e 240°C para os veios NW, e aproximadamente 208°C para os veios NE, envolvendo processos de imiscibilidade e mistura de fluidos de composições distintas. Os veios extensionais NW foram formados sob flutuação de pressão com valores litostáticos a supralitostáticos (125-240 MPa) durante o estágio de fraturamento pré-sismico. Os veios subverticais NE precipitaram dominantemente sob condições de pressão próximas a valores hidrostáticos (10-70 MPa), posteriormente à redistribuição de fluidos de diferentes reservatórios ao longo da zona de ruptura sísmica. Os fluidos hidrotermais foram provavelmente enriquecidos em ouro devido à interação com as rochas encaixantes e a precipitação do minério é atribuída a mudanças nas propriedades físico-químicas em resposta à imiscibilidade de fluidos aliada à mistura de fluidos com salinidades fortemente contrastantes. Estes processos ocorreram como consequência de flutuações cíclicas na pressão de fluidos, bem como de variações no regime de esforços tectônicos associados a episódios de atividade sísmica em zonas de falha. / Fluid inclusion, petrographic and structural analyses are presented for auriferous veins from the Morro do Ouro Mine, Ribeira Belt, southeastern Brazil. The vein-type Au mineralization at the mine is restricted to structurally-controlled domains in a low-grade Calymmian metassedimentary sequence that host also syngenetic Au mineralization. Two auriferous quartz vein systems are present: (i) NW-trending subvertical extensional veins and (ii) ENE-trending subvertical veins parallel to the axial surface of tight folds. The mineralized veins are adjacent to a major dextral transcurrent fault zone and their structural relationships indicate that this fault is severely misoriented for frictional reactivation. The NW-trending veins present a fluid inclusion assemblage dominated by CO2-\'CH IND.4\' inclusions and H2O-CO2-\'CH IND.4\'-\'N IND.2\'-NaCl-\'CaCl IND.2\' inclusions of highly contrasting salinities (4 to 52 wt. % NaCl equivalent) and the NE-trending veins present fluid inclusion assemblage dominated by H2O-CO2-\'CH IND.4\'-\'N IND.2\'-NaCl-\'CaCl IND.2\' inclusions of contrasting salinities (4 to 45 wt. % NaCl equivalent). The entrapment of fluids occurred at temperatures between 225 and 240ºC in NW-trending veins and approximately 208ºC in NE-trending veins, involving processes of fluid immiscibility and mixing between fluids of contrasting compositions. NW-trending extensional veins were formed dominantly under pressure fluctuating between near-lithostatic to strongly supralithostatic values (125-240 MPa) during pre-seismic failure stages. ENE-trending veins precipitated dominantly under near-hydrostatic pressure conditions (10-70 MPa), following discharge of fluids from different reservoirs along the ruptured zone after earthquake rupture stages. The hydrothermal fluids were probably enriched in gold through interaction with the host rocks and its precipitation is attributed to changes of physicochemical properties due to fluid immiscibility and mixing between fluids of highly contrasting salinites, as a consequence of cyclic fluctuations in the values of fluid pressure and tectonic stresses accompanying episodes of seismogenic fault activity.

No description available.