Mathematical Theory of Two-Phase Geochemical Flow with Chemical Species

2018 ◽  
pp. 255-267
Author(s):  
W. J. Lambert ◽  
A. C. Alvarez ◽  
D. Marchesin ◽  
J. Bruining
Keyword(s):  
Mathematical Theory ◽  
Chemical Species ◽  
Two Phase

scholarly journals Elasticity of Phases in Fe-Al-Ti Superalloys: Impact of Atomic Order and Anti-Phase Boundaries

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 299 ◽  
Author(s):  
Martin Friák ◽  
Vilma Buršíková ◽  
Naděžda Pizúrová ◽  
Jana Pavlů ◽  
Yvonna Jirásková ◽  
...  
Keyword(s):  
Solid Solution ◽  
Chemical Composition ◽  
Elastic Properties ◽  
Formation Energy ◽  
Chemical Species ◽  
Two Phase ◽  
Nano Structure ◽  
The Matrix ◽  
Free Material ◽  
Excess Fe

We combine theoretical and experimental tools to study elastic properties of Fe-Al-Ti superalloys. Focusing on samples with chemical composition Fe71Al22Ti7, we use transmission electron microscopy (TEM) to detect their two-phase superalloy nano-structure (consisting of cuboids embedded into a matrix). The chemical composition of both phases, Fe66.2Al23.3Ti10.5 for cuboids and Fe81Al19 (with about 1% or less of Ti) for the matrix, was determined from an Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The phase of cuboids is found to be a rather strongly off-stoichiometric (Fe-rich and Ti-poor) variant of Heusler Fe2TiAl intermetallic compound with the L21 structure. The phase of the matrix is a solid solution of Al atoms in a ferromagnetic body-centered cubic (bcc) Fe. Quantum-mechanical calculations were employed to obtain an insight into elastic properties of the two phases. Three distributions of chemical species were simulated for the phase of cuboids (A2, B2 and L21) in order to determine a sublattice preference of the excess Fe atoms. The lowest formation energy was obtained when the excess Fe atoms form a solid solution with the Ti atoms at the Ti-sublattice within the Heusler L21 phase (L21 variant). Similarly, three configurations of Al atoms in the phase of the matrix with different level of order (A2, B2 and D03) were simulated. The computed formation energy is the lowest when all the 1st and 2nd nearest-neighbor Al-Al pairs are eliminated (the D03 variant). Next, the elastic tensors of all phases were calculated. The maximum Young’s modulus is found to increase with increasing chemical order. Further we simulated an anti-phase boundary (APB) in the L21 phase of cuboids and observed an elastic softening (as another effect of the APB, we also predict a significant increase of the total magnetic moment by 140% when compared with the APB-free material). Finally, to validate these predicted trends, a nano-scale dynamical mechanical analysis (nanoDMA) was used to probe elasticity of phases. Consistent with the prediction, the cuboids were found stiffer.

Turbulent two-phase plumes with bubble-size reduction owing to dissolution or chemical reaction

2013 ◽  
Vol 716 ◽  
pp. 120-136 ◽  
Author(s):  
Mariana G. Domingos ◽  
Silvana S. S. Cardoso
Keyword(s):  
Carbon Dioxide ◽  
Chemical Reaction ◽  
Bubble Diameter ◽  
Chemical Species ◽  
Continuous Phase ◽  
Buoyancy Frequency ◽  
Two Phase ◽  
Norwegian Sea ◽  
Dimensionless Groups ◽  
Carbon Dioxide Release

AbstractTurbulent two-phase plumes consisting of a continuous phase of entrained fluid and a dispersed phase, in the form of buoyant droplets/bubbles, are investigated. Chemical reaction or dissolution causes both a decrease in the size of the droplets/bubbles and a change in the buoyancy of the plume. The behaviours of such a plume in environments with uniform and stratified density are considered. We show that the dynamics of the plume are determined by two dimensionless groups: $N/ T$ and $G/ T$. Here, $N$ is the buoyancy frequency of the environment, $G$ measures the ability of the reaction to change buoyancy and $T$ reflects the effect of reaction on the size of the droplets/bubbles. We identify four regimes of behaviour of a plume in a stratified environment depending on whether the dominant effect on buoyancy arises from reaction or stratification, and on the occurrence of either multiple or single zero-buoyancy levels. For a uniform environment, perturbation solutions for the fluxes of volume, momentum, buoyancy and chemical species as a function of ascent distance are obtained. We apply our findings to understand the dynamics of both of the cases of a release of methane and a release of carbon dioxide in the ocean. For a methane release in the Gulf of Mexico, the motion of the plume is shown to be controlled by external density stratification for a bubble diameter of methane above ${\sim }1$–2 mm. In the case of a carbon dioxide release in the Norwegian Sea, dissolution determines the motion of the plume when the bubble diameter is smaller than ${\sim }0. 5$–3.5 cm. In both scenarios, the plume releases seawater enriched with the chemical at multiple levels.

Numerical Investigation of Biodiesel Production in Capillary Microreactor

2011 ◽  
Author(s):  
Wei Han ◽  
Rachaneewan Charoenwat ◽  
Brian H. Dennis
Keyword(s):  
Mass Transfer ◽  
Volume Flow Rate ◽  
Flow Behavior ◽  
Chemical Species ◽  
Reaction Rates ◽  
Immiscible Fluids ◽  
Biodiesel Production ◽  
Reacting Flow ◽  
Two Phase ◽  
Capillary Microreactor

Synthesis of biodiesel through transesterification of vegetable oil with methanol has been experimentally studied in different types of microreactors though detailed numerical simulation has not yet been presented. The capillary microreactor has the potential to greatly intensify mass transfer between immiscible fluids that would result in higher chemical reaction rates. A segmented flow pattern of oil and methanol forms within the reactor. It has been shown experimentally that the two phase flow has dramatic benefits on the intensification of mass transfer and heat transfer. Such reactors have been proposed for the synthesis of biodiesel and detailed understanding of flow dynamics and chemical kinetics would be useful for process optimization. This paper presents a mathematical model and numerical solution for the synthesis of biodiesel in a capillary reactor. The model represents the unsteady incompressible viscous non-equilibrium chemically reacting flow. The equations are discretized with the finite element method (FEM) and solved to demonstrate the flow behavior and concentration distribution of each chemical species within two phases; different residence time will be obtained with different volume flow rate as well. Information about efficient computational treatment of the model will also be presented.

scholarly journals Numerical Modeling and Validation of a Novel 2D Compositional Flooding Simulator Using a Second-Order TVD Scheme

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2280 ◽  
Author(s):  
Pablo Druetta ◽  
Francesco Picchioni
Keyword(s):  
Multicomponent System ◽  
Chemical Species ◽  
Critical Time ◽  
Second Order ◽  
Tvd Scheme ◽  
Chemical Flooding ◽  
Time Step ◽  
Two Phase ◽  
Good Correspondence ◽  
Compositional Approach

The aim of this paper is to present the latter and develop a numerical simulator aimed at solving a 2D domain porous medium, using the compositional approach to simulate chemical flooding processes. The simulator consists in a two-phase, multicomponent system solved by the IMplicit in Pressure, Explicit in Concentration (IMPEC) approach, which can be operated under an iterative/non-iterative condition on each time-step. The discretization of the differential equations is done using a fully second order of accuracy, along with a Total Variation Diminishing (TVD) scheme with a flux limiter function. This allowed reducing the artificial diffusion and dispersion on the transport equation, improving the chemical species front tracking, decreasing the numerical influence on the recovery results. The new model was validated against both commercial and academic simulators and moreover, the robustness and stability were also tested, showing that the iterative IMPEC is fully stable, behaving as an implicit numerical scheme. The non-iterative IMPEC is conditionally stable, with a critical time-step above which numerical spurious oscillations begin to appear until the system numerically crashes. The results showed a good correspondence in different grid sizes, being largely affected by the time-step, with caused a decrease in the recovery efficiency in the iterative scheme, and the occurrence of numerical oscillations in the non-iterative one. Numerically speaking, the second-order scheme using a flux splitting TVD discretization proved to be a good approach for compositional reservoir simulation, decreasing the influence of numerical truncation errors on the results when compared to traditional, first-order linear schemes. Along with these studies, secondary recoveries in constant and random permeability fields are simulated before employing them in tertiary recovery processes.

THE RIEMANN PROBLEM FOR MULTIPHASE FLOWS IN POROUS MEDIA WITH MASS TRANSFER BETWEEN PHASES

2009 ◽  
Vol 06 (04) ◽  
pp. 725-751 ◽  
Author(s):  
WANDERSON LAMBERT ◽  
DAN MARCHESIN
Keyword(s):  
Porous Media ◽  
Riemann Problem ◽  
Complete Solution ◽  
Chemical Species ◽  
Fundamental Solutions ◽  
Flow In Porous Media ◽  
Thermodynamical Equilibrium ◽  
Two Phase ◽  
Single Chemical ◽  
Representative System

We are interested in solving systems of conservation laws modeling multiphase fluid flows under the approximation of local thermodynamical equilibrium except at very localized places. This equilibrium occurs for states on sheets of a stratified variety called the "thermodynamical equilibrium variety," obtained from thermodynamical laws. Strong deviation from equilibrium occurs in shocks connecting adjacent sheets of this variety. We assume that fluids may expand and we model the physical problem by a system of equations where a velocity variable appears only in the flux terms, giving rise to a wave with "infinite" characteristic speed. We develop a general theory for fundamental solutions for this class of equations. We study all bifurcation loci, such as coincidence and inflection loci and develop a systematic approach to solve problems described by similar equations. For concreteness, we exhibit the bifurcation theory for a representative system with three equations. We find the complete solution of the Riemann problem for two-phase thermal flow in porous media with two chemical species; to simplify the physics, the liquid phase consists of a single chemical species. We give an example of steam and nitrogen injection into a porous medium, with applications to geothermal energy recovery.

scholarly journals Effects of laden particles in two-phase flows on turbulence and scalar diffusion of chemical species

2003 ◽  
Vol 2003 (0) ◽  
pp. 231-232
Author(s):  
Takenobu MICHIOKA ◽  
Ryoichi KUROSE ◽  
Kouichi SADA ◽  
Hisao MAKINO
Keyword(s):  
Chemical Species ◽  
Two Phase Flows ◽  
Two Phase ◽  
Scalar Diffusion

Chemical Species Identification in an SEM by Changes in Emitted X-Ray Energies

1974 ◽  
Vol 32 ◽  
pp. 570-571
Author(s):  
R. H. Duff
Keyword(s):  
Species Identification ◽  
Valence Electron ◽  
Chemical Species ◽  
X Rays ◽  
Chemical Bonds ◽  
Small Shift ◽  
X Ray ◽  
Electron Transitions ◽  
Peak Energy ◽  
Chemical Combination

A material irradiated with electrons emits x-rays having energies characteristic of the elements present. Chemical combination between elements results in a small shift of the peak energies of these characteristic x-rays because chemical bonds between different elements have different energies. The energy differences of the characteristic x-rays resulting from valence electron transitions can be used to identify the chemical species present and to obtain information about the chemical bond itself. Although these peak-energy shifts have been well known for a number of years, their use for chemical-species identification in small volumes of material was not realized until the development of the electron microprobe.

Effect of Shock Loading on the Microstructure of Uniloy 326

1974 ◽  
Vol 32 ◽  
pp. 504-505
Author(s):  
K. P. Staudhammer ◽  
L. E. Murr
Keyword(s):  
Grain Size ◽  
Shock Loading ◽  
Current Investigation ◽  
Two Phase ◽  
05 C ◽  
Shock Deformation ◽  
Heat Treated

The effect of shock loading on a variety of steels has been reviewed recently by Leslie. It is generally observed that significant changes in microstructure and microhardness are produced by explosive shock deformation. While the effect of shock loading on austenitic, ferritic, martensitic, and pearlitic structures has been investigated, there have been no systematic studies of the shock-loading of microduplex structures.In the current investigation, the shock-loading response of millrolled and heat-treated Uniloy 326 (thickness 60 mil) having a residual grain size of 1 to 2μ before shock loading was studied. Uniloy 326 is a two phase (microduplex) alloy consisting of 30% austenite (γ) in a ferrite (α) matrix; with the composition.3% Ti, 1% Mn, .6% Si,.05% C, 6% Ni, 26% Cr, balance Fe.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

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