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Additive manufacturing enables the production of complex multi-material geometries and bulk metallic glass parts beyond their critical casting thickness. The local modification of structure, composition, and properties is explored in this thesis with the aim to design novel composite materials and functional gradients. The present work contributes to the process understanding required to produce bulk metallic glass composites in the laser powder bed fusion process. The investigated material systems include zirconium and iron based metallic glasses, metallic glass - nitride composites, as well as laser nitriding of titanium. The onset of devitrification of metallic glasses due to the processing or post-processing heat treatments induces the formation of nanoscale clusters. Features of > 1 nm can be detected and reliably distinguished from random fluctuations by atom probe tomography. The progression of crystallisation depends on the oxygen content of the samples and the applied heating or cooling rates. In-depth understanding of the crystallisation processes can be used to optimise both compositions and processing conditions. The process atmosphere contains reactive species such as oxygen or nitrogen, which can be incorporated during different stages of processing by surface oxidation of the powder or substrate pieces as well as by reactions with the gas during processing. While an inert gas atmosphere with a low residual oxygen content is sufficient to hinder reactions with residual oxygen, a nitrogen atmosphere can be used for local laser nitriding and, thus, the fabrication of metallic glass – ceramic composites. Due to the decompositions of nitrides formed in the preceding process steps and the tendency of a metallic glass matrix to crystallise, which limits the processing conditions, the incorporation of nitrogen is restricted to the first few hundred nm from the surface for a Zr-based amorphous alloy. In titanium, as a crystalline example, nitrogen is incorp

Additive manufacturing enables the production of complex multi-material geometries and bulk metallic glass parts beyond their critical casting thickness. The local modification of structure, composition, and properties is explored in this thesis with the aim to design novel composite materials and functional gradients. The present work contributes to the process understanding required to produce bulk metallic glass composites in the laser powder bed fusion process. The investigated material systems include zirconium and iron based metallic glasses, metallic glass - nitride composites, as well as laser nitriding of titanium. The onset of devitrification of metallic glasses due to the processing or post-processing heat treatments induces the formation of nanoscale clusters. Features of > 1 nm can be detected and reliably distinguished from random fluctuations by atom probe tomography. The progression of crystallisation depends on the oxygen content of the samples and the applied heating or cooling rates. In-depth understanding of the crystallisation processes can be used to optimise both compositions and processing conditions. The process atmosphere contains reactive species such as oxygen or nitrogen, which can be incorporated during different stages of processing by surface oxidation of the powder or substrate pieces as well as by reactions with the gas during processing. While an inert gas atmosphere with a low residual oxygen content is sufficient to hinder reactions with residual oxygen, a nitrogen atmosphere can be used for local laser nitriding and, thus, the fabrication of metallic glass – ceramic composites. Due to the decompositions of nitrides formed in the preceding process steps and the tendency of a metallic glass matrix to crystallise, which limits the processing conditions, the incorporation of nitrogen is restricted to the first few hundred nm from the surface for a Zr-based amorphous alloy. In titanium, as a crystalline example, nitrogen is incorp

Additive manufacturing enables the production of complex multi-material geometries and bulk metallic glass parts beyond their critical casting thickness. The local modification of structure, composition, and properties is explored in this thesis with the aim to design novel composite materials and functional gradients. The present work contributes to the process understanding required to produce bulk metallic glass composites in the laser powder bed fusion process. The investigated material systems include zirconium and iron based metallic glasses, metallic glass - nitride composites, as well as laser nitriding of titanium. The onset of devitrification of metallic glasses due to the processing or post-processing heat treatments induces the formation of nanoscale clusters. Features of > 1 nm can be detected and reliably distinguished from random fluctuations by atom probe tomography. The progression of crystallisation depends on the oxygen content of the samples and the applied heating or cooling rates. In-depth understanding of the crystallisation processes can be used to optimise both compositions and processing conditions. The process atmosphere contains reactive species such as oxygen or nitrogen, which can be incorporated during different stages of processing by surface oxidation of the powder or substrate pieces as well as by reactions with the gas during processing. While an inert gas atmosphere with a low residual oxygen content is sufficient to hinder reactions with residual oxygen, a nitrogen atmosphere can be used for local laser nitriding and, thus, the fabrication of metallic glass – ceramic composites. Due to the decompositions of nitrides formed in the preceding process steps and the tendency of a metallic glass matrix to crystallise, which limits the processing conditions, the incorporation of nitrogen is restricted to the first few hundred nm from the surface for a Zr-based amorphous alloy. In titanium, as a crystalline example, nitrogen is incorp

Additive manufacturing enables the production of complex multi-material geometries and bulk metallic glass parts beyond their critical casting thickness. The local modification of structure, composition, and properties is explored in this thesis with the aim to design novel composite materials and functional gradients. The present work contributes to the process understanding required to produce bulk metallic glass composites in the laser powder bed fusion process. The investigated material systems include zirconium and iron based metallic glasses, metallic glass - nitride composites, as well as laser nitriding of titanium. The onset of devitrification of metallic glasses due to the processing or post-processing heat treatments induces the formation of nanoscale clusters. Features of > 1 nm can be detected and reliably distinguished from random fluctuations by atom probe tomography. The progression of crystallisation depends on the oxygen content of the samples and the applied heating or cooling rates. In-depth understanding of the crystallisation processes can be used to optimise both compositions and processing conditions. The process atmosphere contains reactive species such as oxygen or nitrogen, which can be incorporated during different stages of processing by surface oxidation of the powder or substrate pieces as well as by reactions with the gas during processing. While an inert gas atmosphere with a low residual oxygen content is sufficient to hinder reactions with residual oxygen, a nitrogen atmosphere can be used for local laser nitriding and, thus, the fabrication of metallic glass – ceramic composites. Due to the decompositions of nitrides formed in the preceding process steps and the tendency of a metallic glass matrix to crystallise, which limits the processing conditions, the incorporation of nitrogen is restricted to the first few hundred nm from the surface for a Zr-based amorphous alloy. In titanium, as a crystalline example, nitrogen is incorp

Additive manufacturing enables the production of complex multi-material geometries and bulk metallic glass parts beyond their critical casting thickness. The local modification of structure, composition, and properties is explored in this thesis with the aim to design novel composite materials and functional gradients. The present work contributes to the process understanding required to produce bulk metallic glass composites in the laser powder bed fusion process. The investigated material systems include zirconium and iron based metallic glasses, metallic glass - nitride composites, as well as laser nitriding of titanium. The onset of devitrification of metallic glasses due to the processing or post-processing heat treatments induces the formation of nanoscale clusters. Features of > 1 nm can be detected and reliably distinguished from random fluctuations by atom probe tomography. The progression of crystallisation depends on the oxygen content of the samples and the applied heating or cooling rates. In-depth understanding of the crystallisation processes can be used to optimise both compositions and processing conditions. The process atmosphere contains reactive species such as oxygen or nitrogen, which can be incorporated during different stages of processing by surface oxidation of the powder or substrate pieces as well as by reactions with the gas during processing. While an inert gas atmosphere with a low residual oxygen content is sufficient to hinder reactions with residual oxygen, a nitrogen atmosphere can be used for local laser nitriding and, thus, the fabrication of metallic glass – ceramic composites. Due to the decompositions of nitrides formed in the preceding process steps and the tendency of a metallic glass matrix to crystallise, which limits the processing conditions, the incorporation of nitrogen is restricted to the first few hundred nm from the surface for a Zr-based amorphous alloy. In titanium, as a crystalline example, nitrogen is incorp

A theory of stable dendrite growth in an undercooled binary melt is developed for the case of intense convection. Conductive heat and mass transfer boundary conditions are replaced by convective conditions, where the flux of heat (or solute) is proportional to the temperature or concentration difference between the surface of the dendrite and far from it. The marginal mode of perturbation wavelengths is calculated using the linear morphological stability analysis. Combining this analysis with the solvability theory, we have derived a selection criterion that represents the first condition to define a combination of dendrite tip velocity and tip diameter. The second condition—the undercooling balance—is derived for intense convection. The theory under consideration determines the dendrite tip velocity and tip diameter for low undercooling. This convective theory is combined with the classical theory of dendritic growth (conductive boundary conditions), which is valid for moderate and high undercooling. Thus, the entire range of melt undercooling is covered. Our results are in good agreement with experiments on Al–Ge crystallization. © 2021 The Authors. Mathematical Methods in the Applied Sciences published by John Wiley & Sons Ltd.

Buoyancy-driven airflow that included two isothermal inner plates established in a vented cavity is investigated numerically. The thermally optimum wall-to-wall spacing of the immersed channel, as well as its dependence with respect to the relevant governing parameters, are determined. Results are presented as a function of the aspect ratio b/H for a wide range of Rayleigh numbers Ra_H. A logarithmic correlation for the optimum (b/H)opt as a function of Ra_H is presented. In addition, since the outlined configuration might be subject to intense heating conditions, the influence of considering variable thermophysical properties is also included in the analysis. In fact, an appreciable influence of the variation of properties on (b/H)opt is also detected for a representative value of Ra_H = 10^9. Obtained results can be directly applied to the optimization of electronic equipment cooling, or even to thermal passive devices in buildings.

Formation of bubbles in water inside an annulus pipe in a flow boiling regime was experimentally investigated. The effect of various variables, such as total dissolved solid materials (TDS) in terms of mass fraction, flow rate of water, and applied heat flux (HF) on the heat transfer coefficient (HTC) and bubble behavior of water, was experimentally investigated. A regression formula was fitted to estimate the average bubble diameter at various TDS values, with accuracy of <4.1% up to heat flux of 90 kW/m2. Results show that the presence of TDS materials can increase the contact angle of bubble and bubble diameter, and also promotes the HTC value of the system. However, flow rate of water suppressed bubble generation, and increased the heat transfer coefficient due to the renewal of the thermal boundary layer around the boiling surface. Likewise, it was identified that forced convective and nucleate boiling heat transfer mechanisms contribute to the flow of boiling water, and heat flux is a key parameter in determining the mechanism of heat transfer. In the present study, heat flux of 15 kW/m2 at 50 °C was the heat flux in which onset of nucleate boiling was identified inside the annulus pipe. The contact angle of water at TDS values of 300 mg/L and 1200 mg/L was 74° and 124°, respectively, showing the improvement in heat transfer characteristics of water due to the presence of TDS materials.

Geological storage of carbon dioxide (CO2) in deep saline aquifers mitigates atmospheric release of greenhouse gases. To estimate storage capacity and evaluate storage safety, knowledge of the trapping mechanisms that retain CO2 within geological formations, and the factors affecting these is fundamental. The objective of this thesis is to study residual and solubility trapping mechanisms (the latter enhanced by density-driven convective mixing), specifically in regard to their dependency on aquifer characteristics, and to investigate and develop methods for quantification of CO2 trapping in the field. The work includes implementation of existing numerical simulators and inverse modeling, as well as the development of new models and experimental methods for the study and quantification of CO2 trapping. A comparison of well-test designs in regard to their abilities to estimate the in-situ residual gas saturation (that determines the residual trapping of CO2) is presented, as well as a novel indicator-tracer approach to obtain residual gas saturation conditions in a formation. The results can aid in the planning of well-tests for estimation of trapping potential during site characterization. Pore-network modeling simulations were conducted to study the effects of co-contaminant sulphur dioxide and formation thermodynamic and salinity conditions on residual CO2 trapping. Furthermore, an analysis tool was developed and used to study the prerequisites for density-driven instability and convective mixing over broad geological storage conditions, including the relative influences of formation characteristics on factors controlling the convective process. The results show which conditions favour or disfavour residual and solubility trapping, knowledge useful for long-term predictions of the fate of injected CO2, and safety assessments during site selection. An optical experimental method, the refractive-light-transmission (RLT) technique, and an analogue system design were

Geological storage of carbon dioxide (CO2) in deep saline aquifers mitigates atmospheric release of greenhouse gases. To estimate storage capacity and evaluate storage safety, knowledge of the trapping mechanisms that retain CO2 within geological formations, and the factors affecting these is fundamental. The objective of this thesis is to study residual and solubility trapping mechanisms (the latter enhanced by density-driven convective mixing), specifically in regard to their dependency on aquifer characteristics, and to investigate and develop methods for quantification of CO2 trapping in the field. The work includes implementation of existing numerical simulators and inverse modeling, as well as the development of new models and experimental methods for the study and quantification of CO2 trapping. A comparison of well-test designs in regard to their abilities to estimate the in-situ residual gas saturation (that determines the residual trapping of CO2) is presented, as well as a novel indicator-tracer approach to obtain residual gas saturation conditions in a formation. The results can aid in the planning of well-tests for estimation of trapping potential during site characterization. Pore-network modeling simulations were conducted to study the effects of co-contaminant sulphur dioxide and formation thermodynamic and salinity conditions on residual CO2 trapping. Furthermore, an analysis tool was developed and used to study the prerequisites for density-driven instability and convective mixing over broad geological storage conditions, including the relative influences of formation characteristics on factors controlling the convective process. The results show which conditions favour or disfavour residual and solubility trapping, knowledge useful for long-term predictions of the fate of injected CO2, and safety assessments during site selection. An optical experimental method, the refractive-light-transmission (RLT) technique, and an analogue system design were

Geological storage of carbon dioxide (CO2) in deep saline aquifers mitigates atmospheric release of greenhouse gases. To estimate storage capacity and evaluate storage safety, knowledge of the trapping mechanisms that retain CO2 within geological formations, and the factors affecting these is fundamental. The objective of this thesis is to study residual and solubility trapping mechanisms (the latter enhanced by density-driven convective mixing), specifically in regard to their dependency on aquifer characteristics, and to investigate and develop methods for quantification of CO2 trapping in the field. The work includes implementation of existing numerical simulators and inverse modeling, as well as the development of new models and experimental methods for the study and quantification of CO2 trapping. A comparison of well-test designs in regard to their abilities to estimate the in-situ residual gas saturation (that determines the residual trapping of CO2) is presented, as well as a novel indicator-tracer approach to obtain residual gas saturation conditions in a formation. The results can aid in the planning of well-tests for estimation of trapping potential during site characterization. Pore-network modeling simulations were conducted to study the effects of co-contaminant sulphur dioxide and formation thermodynamic and salinity conditions on residual CO2 trapping. Furthermore, an analysis tool was developed and used to study the prerequisites for density-driven instability and convective mixing over broad geological storage conditions, including the relative influences of formation characteristics on factors controlling the convective process. The results show which conditions favour or disfavour residual and solubility trapping, knowledge useful for long-term predictions of the fate of injected CO2, and safety assessments during site selection. An optical experimental method, the refractive-light-transmission (RLT) technique, and an analogue system design were

Geological storage of carbon dioxide (CO2) in deep saline aquifers mitigates atmospheric release of greenhouse gases. To estimate storage capacity and evaluate storage safety, knowledge of the trapping mechanisms that retain CO2 within geological formations, and the factors affecting these is fundamental. The objective of this thesis is to study residual and solubility trapping mechanisms (the latter enhanced by density-driven convective mixing), specifically in regard to their dependency on aquifer characteristics, and to investigate and develop methods for quantification of CO2 trapping in the field. The work includes implementation of existing numerical simulators and inverse modeling, as well as the development of new models and experimental methods for the study and quantification of CO2 trapping. A comparison of well-test designs in regard to their abilities to estimate the in-situ residual gas saturation (that determines the residual trapping of CO2) is presented, as well as a novel indicator-tracer approach to obtain residual gas saturation conditions in a formation. The results can aid in the planning of well-tests for estimation of trapping potential during site characterization. Pore-network modeling simulations were conducted to study the effects of co-contaminant sulphur dioxide and formation thermodynamic and salinity conditions on residual CO2 trapping. Furthermore, an analysis tool was developed and used to study the prerequisites for density-driven instability and convective mixing over broad geological storage conditions, including the relative influences of formation characteristics on factors controlling the convective process. The results show which conditions favour or disfavour residual and solubility trapping, knowledge useful for long-term predictions of the fate of injected CO2, and safety assessments during site selection. An optical experimental method, the refractive-light-transmission (RLT) technique, and an analogue system design were

Geological storage of carbon dioxide (CO2) in deep saline aquifers mitigates atmospheric release of greenhouse gases. To estimate storage capacity and evaluate storage safety, knowledge of the trapping mechanisms that retain CO2 within geological formations, and the factors affecting these is fundamental. The objective of this thesis is to study residual and solubility trapping mechanisms (the latter enhanced by density-driven convective mixing), specifically in regard to their dependency on aquifer characteristics, and to investigate and develop methods for quantification of CO2 trapping in the field. The work includes implementation of existing numerical simulators and inverse modeling, as well as the development of new models and experimental methods for the study and quantification of CO2 trapping. A comparison of well-test designs in regard to their abilities to estimate the in-situ residual gas saturation (that determines the residual trapping of CO2) is presented, as well as a novel indicator-tracer approach to obtain residual gas saturation conditions in a formation. The results can aid in the planning of well-tests for estimation of trapping potential during site characterization. Pore-network modeling simulations were conducted to study the effects of co-contaminant sulphur dioxide and formation thermodynamic and salinity conditions on residual CO2 trapping. Furthermore, an analysis tool was developed and used to study the prerequisites for density-driven instability and convective mixing over broad geological storage conditions, including the relative influences of formation characteristics on factors controlling the convective process. The results show which conditions favour or disfavour residual and solubility trapping, knowledge useful for long-term predictions of the fate of injected CO2, and safety assessments during site selection. An optical experimental method, the refractive-light-transmission (RLT) technique, and an analogue system design were

An experimental study on an n-octane pool fire bound on one side by an ice wall was carried out to investigate the effects on ice melting by convection within the liquid part of the fuel. Experiments were conducted in a square glass tray (9.6cm ×9.6cm ×5cm) with a 3cm thick ice wall (9.6cm ×6.5cm ×3cm) placed on one side of the tray. The melting front velocity, as an indicator of the melting rate of the ice, increased from 0.04cm/min to 1cm/min. The measurement of the burning rates and flame heights showed two distinctive behaviors; an induction period from the initial self-sustained flame to the peak mass loss rate followed by a steady phase from the peak of mass loss rate until the manual extinguishment. Similarly, the flow field measurements by a 2-dimensional PIV system indicated the existence of two different flow regimes. In the moments before ignition of the fuel, coupling of surface tension and buoyancy forces led to a combined one roll structure in the fuel. After ignition the flow field began transitioning toward an unstable flow regime (separated) with an increase in number of vortices around the ice wall. The separated regime started with presence of a multi-roll structure separating from a primary horizontal flow on the top driven by Marangoni convection. As the burning rate/flame height increased the velocity and evolving flow patterns enhanced the melting rate of the ice wall. Experimentally determined temperature contours, using an array of finely spaced thermocouples in the liquid fuel, were used to further investigate the two layer temperature structure; an upper layer (∼8mm thick) with steep temperature gradient in the vertical direction and a layer of low temperature in deeper regions. A hot zone with thickness of ∼3mm was present below the free surface corresponding to the multi-roll location. The multi-roll structure could be the main reason for the transport of the heat received from the flame toward the ice wall which causes the melting.

We report a self-assisted optothermal trapping and patterning of gold nanorods (GNRs) on glass surfaces with a femtosecond laser. We show that GNRs are not only the trapping targets, but also can enhance the optothermal trapping of other particles. This trapping phenomenon is the net result of thermophoresis and a convective flow caused by localized heating. The heating is due to the conversion of absorbed photons into heat at GNR's longitudinal surface plasmon resonance (LSPR) wavelength. First, we investigated the optothermal trapping of GNRs at their LSPR wavelength on the glass surface with as low as 0.5 mW laser power. The trapping range was observed to be larger than a typical field of view, e.g. 210 µm × 210 µm here. Second, by adjusting the distance between the laser focus and the glass surface, ring patterns of GNRs on the glass surface were obtained. These patterns could be controlled by the laser power and the numerical aperture of the microscope objective. Moreover, we examined the spectral emission of GNRs under different trapping conditions using the spectral phasor approach to reveal the temperature and association status of GNRs. Our study will help understanding manipulation of flows in solution and in biological systems that can be applied in future investigations of GNR-induced heating and flows.

We report a self-assisted optothermal trapping and patterning of gold nanorods (GNRs) on glass surfaces with a femtosecond laser. We show that GNRs are not only the trapping targets, but also can enhance the optothermal trapping of other particles. This trapping phenomenon is the net result of thermophoresis and a convective flow caused by localized heating. The heating is due to the conversion of absorbed photons into heat at GNR's longitudinal surface plasmon resonance (LSPR) wavelength. First, we investigated the optothermal trapping of GNRs at their LSPR wavelength on the glass surface with as low as 0.5 mW laser power. The trapping range was observed to be larger than a typical field of view, e.g. 210 µm × 210 µm here. Second, by adjusting the distance between the laser focus and the glass surface, ring patterns of GNRs on the glass surface were obtained. These patterns could be controlled by the laser power and the numerical aperture of the microscope objective. Moreover, we examined the spectral emission of GNRs under different trapping conditions using the spectral phasor approach to reveal the temperature and association status of GNRs. Our study will help understanding manipulation of flows in solution and in biological systems that can be applied in future investigations of GNR-induced heating and flows.

El estudio del comportamiento de un fluido al que se le aporta calor en el interior de cavidades o recintos total o parcialmente cerrados ha sido motivo de muchos y variados estudios, dado el amplio abanico de posibilidades que tiene este fenómeno en el mundo de la Ingeniería, como por ejemplo ventilación, climatización o evacuación de calor. Muchos de estos estudios servirán como apoyo en la elaboración de este trabajo, como posteriormente se irá indicando. En general, los dispositivos en los que tienen lugar procesos con trasmisión de calor por convección natural reciben la denominación de pasivos, por el hecho de que no intervienen sistemas electromecánicos para generación o transmisión de energía. La motivación por la cual se llevó a cabo este trabajo radica en lo llamativo que resulta la aparente sencillez de los dispositivos mediante los cuales se aprovechan las propiedades de los flujos convectivos naturales, dispositivos que se emplean desde para sistemas de climatización pasiva, sistemas cada vez más presentes en las denominadas casas inteligentes; hasta para su uso en las energías renovables, como las chimeneas solares para generación de energía. Por lo que se pretende llevar a cabo un estudio del comportamiento de un flujo de convección natural para llegar a comprender mejor las propiedades de dicho flujo.

Some applications of commercial code GASP on aerospace engineering are shown. One of these is concerned with numerical analysis around the fore body of HYFLEX (Hypersonic Flight Experiment). Computational results of real gas flow for HYFLEX on flight time 120.44 s are calculated and compared with the experiment. Park's seven species finite-rate chemical reaction model is used. For convective terms of Navier-Stokes equations, Roe Flux Difference Splitting (wall direction) and Van Leer Flux-Vector Splitting (other directions) are applied with the SuperBee limiter. For the turbulence model the Baldwin-Lomax algebraic model is used. The other case is a forward facing cavity with an incoming supersonic flow time dependent analysis. The pressure and density will vary sinusoidally at a frequency of 3,400 Hz. The amplitude of oscillation will equal 2 percent of the mean flow. For convective terms Van Leer Flux-Vector Splitting is applied, and a second order temporal accuracy is used., Special Publication of National Aerospace Laboratory, 航空宇宙技術研究所特別資料

The effects of convective flows in n-octane pool fires in an ice cavity were investigated and it was found that a new set of parameters to the classical problem of bounded pool fires arises under these unique conditions. To systematically understand these parameters, two sets of experiments were performed by burning n-octane in cylindrically shaped ice cavities of 5.7 cm diameter. The first set of experiments was intended to provide a clear understanding of the geometry change of the cavity and displacement of the fuel layer. The results of these experiments showed that the rate of melting of the ice walls were higher in areas where the fuel layer was in contact with ice than in places where the flame was present. Due to the melting of the ice walls, a ring-shaped void was formed around the perimeter of the cavity. In the second set of experiments, the change in the temperature of the fuel layer was measured by use of multiple thermocouples at different locations inside the ice cavity. The results of the temperature analysis showed that the lateral temperature gradient of the fuel layer was an increasing function of time, whereas the vertical temperature gradient was a decreasing function of time. Using these experimental results, two dimensionless numbers (Marangoni and Rayleigh) were calculated. The Marangoni number represents the surface tension driven flows in the fuel layer and the Rayleigh number represents the buoyancy driven flows in the fuel layer. The results of this study showed two major convective phases; in the first half of the burning time, the buoyancy driven flows (Rayleigh) were dominant, while Marangoni convection was dominant in the second half of the burning time. The role of these mechanisms in affecting the flow and melting the ice is discussed. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

The increase of the diffusion coefficient, due to its concentration dependency, can strongly increase the mass transfer rate through the membrane. Accordingly, the negative effect of the mass transfer resistance of the polarization layer can essentially be increased on the separation efficiency, especially in the case of low solute concentration in the feed phase. This effect can also exist at high solute concentration at extremely high pervaporation rate as it is illustrated by the case study. The simultaneous effect of the concentration polarization and membrane layers is discussed in this paper in case of exponentially or linearly concentration dependent diffusion coefficient. Mass transfer rate, enrichment and the polarization modulus are expressed in implicit, closed mathematical equations involving the transport parameters of the two layers, i.e.the kL, Pe, km, H values. How the increasing diffusion coefficient affects the concentration distribution in the polarization and the membrane layers and due to it, the mass transfer rate, enrichment or the polarization modulus, indicating the effect of the polarization layer, is discussed. It is shown how strongly the dimensionless plasticizing coefficient can decrease the polarization modulus and can affect the concentration distribution in the polarization and the membrane layers as well as the ratio of the diffusion dependent mass transfer rate to that without plasticizing effect, namely if . The case study illustrates the effect of the external mass transfer resistance on the mass transfer rate and on the concentration distribution in the case of high value of a plasticization coefficient.

Polymethacrylate monoliths, specifically poly(glycidyl methacrylate-co-ethylene dimethacrylate) or poly(GMA-co-EDMA) monoliths, are a new generation of chromatographic supports and are significantly different from conventional particle-based adsorbents, membranes, and other monolithic supports for biomolecule purification. Similar to other monoliths, polymethacrylate monoliths possess large pores which allow convective flow of mobile phase and result in high flow rates at reduced pressure drop, unlike particulate supports. The simplicity of the adsorbent synthesis, pH resistance, and the ease and flexibility of tailoring their pore size to that of the target biomolecule are the key properties which differentiate polymethacrylate monoliths from other monoliths. Polymethacrylate monoliths are endowed with reactive epoxy groups for easy functionalization (with anion-exchange, hydrophobic, and affinity ligands) and high ligand retention. In this review, the structure and performance of polymethacrylate monoliths for chromatographic purification of biomolecules are evaluated and compared to those of other supports. The development and use of polymethacrylate monoliths for research applications have grown rapidly in recent times and have enabled the achievement of high through-put biomolecule purification on semi-preparative and preparative scales.

Pressurized ventilation acts to increase the oxygen supply to roots and rhizomes in some species of emergent plants. In a greenhouse experiment, we investigated how pressurized ventilation affected growth, biomass allocation and mineral content of Phragmites australis in two water depths (15 cm or 75 cm) and two substrates (organic sediment or sand). Through perforating each stem above the water surface, pressurized ventilation was inhibited without affecting oxygen diffusion. In controls, 10-20% of the stems were perforated to make certain that lack of efflux sites would not limit pressurized ventilation. Plants with inhibited pressurized ventilation had lower oxygen concentrations in their stem bases than control plants. Growth was lower in plants with inhibited pressurized ventilation compared to controls except when plants grew in a combination of sand and shallow water. In plants grown in an organic sediment, but not in those grown in sand, inhibition of pressurized ventilation resulted in decreased biomass allocation to soil roots but increased allocation to aquatic roots. Stem perforation affected the tissue concentrations of nitrogen, phosphorus, magnesium, manganese and aluminium but not of calcium or iron. We suggest that the lower growth in plants with inhibited pressurized ventilation was caused by decreased mineral uptake, which may have resulted from the decreased proportional allocation to soil root weight, from decreased mineral availability or from impaired root function. In plants grown in sand in shallow water, diffusion seemed to cover the oxygen demand, as pressurized ventilation did not affect growth.

1 Pressurized ventilation, which increases gas exchange between aerial and submerged plant parts, has been found in various emergent macrophyte species. We investigated the potential for this mechanism to affect growth, morphology and biomass allocation in Phragmites australis in glasshouse experiments. 2 Inhibition of pressurized ventilation by perforation of stems above the water surface resulted in decreased oxygen concentrations in stem bases and rhizomes. Perforation caused little mechanical damage. 3 Allometric methods were used to evaluate treatment effects on biomass allocation and morphology. 4 Inhibition of pressurized ventilation resulted in decreased allocation to belowground weight and decreased rhizome penetration into the substrate in two of three experiments. Treatment also decreased growth rate, rhizome length and number of rhizomes when substrate had a high organic content. In the third experiment, growth clearly decreased in deep water, although inhibition of pressurized ventilation did not affect growth, biomass allocation or morphology at either of the water depths tested. 5 Decreased allocation to below-ground parts and decreased rhizome lengths may be adaptations to allow the oxygen concentration in roots and rhizomes to be maintained above a critical level when the oxygen supply is low. 6 Pressurized ventilation may improve the performance of P. australis but only under certain conditions (e.g. not when growth rate is low or the substrate has a high redox potential).

My long-term goal is to make observations in the laboratory and then conduct associated experiments based on the theory of nonlinear fluid dynamics in the ocean. Two processes were studied recently. The first is the behavior of convective flow driven by two distinct buoyancy sources in which more than one flow pattern is found for exactly the same forcing conditions. A primary objective was to determine the quantitative role of mixing upon circulation. The second is the strength and size of flows from sidewall forcing in rotating stratified fluid. The primary objective was to document the flow patterns near a line source of heat located at mid-depth on the periphery of a cylinder in a rotating stratified fluid. Both are poorly understood but known to be important in assorted oceanic phenomena. With the ultimate objective of conducting experiments for rotating flows, we have been able to develop a chamber whose floor was heated and which has an inflow of salty water near the top. This chamber was connected to a large tank of room temperature fresh water through a slot. The prototype experiments indicated that mixing within the chamber must be limited for the flows to differ from the simple box models mentioned above. Thus a theory for undermixed exchange flow was developed (theory supported by NSF) and successfully tested. The results were used to design an undermixed doubly driven chamber. Mixing was varied by changing the elevation of a tube which introduces the salty water. For boundary layer processes in rotating stratified fluid, boundary layers produced by heating from the side have been produced in a laboratory cylinder of thermally stratified water on a turntable. The results are compared with calculations by Joseph Pedlosky. A variety of other theoretical solutions have been developed which reveal these boundary layers and their strength in great detail., See also ADM002252.

A holographic interferometry technique has been used to record an illuminated plane of a Rayleigh-Bernard convection flow where small tracers are suspended. The analysis of several interferograms with different sensitivity vectors, obtained from the same hologram by varying the viewing direction, allows to obtain the three components of the velocity field. (Author)

peer-reviewed, The computational fluid dynamics (CFD) modeling is an applicable tool for the prediction of fluid flow characteristics (velocity, temperature, pressure, etc.). However, CFD requires a lot of time, computational efforts and as a result, much more expenses for complicated cases (e.g. turbulent flow, 3-dimensional calculations, etc.). The present work tries to conduct an investigation on the potential of the artificial intelligence algorithms in overcoming such barriers of CFD modeling. Turbulent forced convection of Cu/water nanofluid in a tube under constant heat flux is considered as a case study for the model development. The density and viscosity of the based fluid are enhanced by the suspension of the nanoparticles. This makes more pressure drop and as a result, imposes more pumping power. So, this paper is focused on a way to facilitate the prediction of the pressure of the nanofluid convective flow. The results of the CFD modeling are learned by the adaptive network-based fuzzy inference system (ANFIS), as the artificial intelligence method. The CFD modeling is done for several Cu nanoparticle volume fractions (i.e. 0.3, 0.5, 0.8, 1, and 2). Several types of variables as inputs (i.e. x, y, z, and nanoparticle volume fraction) and different kinds of membership functions (i.e. Generalized bell-shaped membership function (gbellmf), Gaussian membership function (gaussmf), Gaussian combination membership function (gauss2mf), Difference between two sigmoidal membership functions (dsigmf), Product of two sigmoidal membership functions (psigmf)) are examined until the intelligence requirements of the ANFIS are satisfied. Once the best intelligence of ANFIS has been achieved, there is no need for complicated CFD modeling. The ANFIS predictions show the highest compatibility with the CFD results. The maximum pressure drop was predicted around 1500 Pa. The results also revealed that for checking the intelligence condition the coefficient of determination (R2 ) is not sole

Natural convection liquid cooling of simulated electronic components in a vertical channel was investigated. The test surface consisted of three columns of fifteen flush mounted foil heaters. The channel was formed by placing a smooth movable shrouding wall parallel to the test surface. The experimental procedure called for temperature measurements and flow visualization at various power levels and channel spacings. Surface temperatures of each heat source were measured using a centrally located embedded thermocouple. Temperature measurement within the flow was conducted using a thermocouple probe. Flow visualization was conducted with the use of a laser generated plane of light. A visual temperature profile of the board was developed through the use of liquid crystals. From the data obtained, experimental correlations relating the local heat transfer properties with shroud wall spacing and strip heater power levels were developed., http://archive.org/details/naturalconvectio1094526097, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.

Natural convection from a single column of eight in-line, rectangular, flush heat sources was examined. A vertical channel was formed by placing a movable shroud parallel to the test surface. The experimental program consisted of temperature measurements and flow visualizations. For a range of component power levels and channel spacings, surface temperatures of each heat source were measured at five locations using embedded thermocouples. The resulting steady state data was compared with corresponding measurements for an identical geometric arrangement of protruding heat sources. The flow visualization was carried out using a laser generated plane of light., http://archive.org/details/naturalconvectio1094523323, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.