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Numerical simulation of phase transition problems with explicit interface tracking
Phase change is ubiquitous in nature and industrial processes. Started from the Stefan problem, it is a topic with a long history in applied mathematics and sciences and continues to generate outstanding mathematical problems. For instance, the explicit tracking of the Gibbs dividing surface between phases is still a grand challenge. Our work has been motivated by such challenge and here we report on progress made in solving the governing equations of continuum transport in the presence of a moving interface by the front tracking method. The most pressing issue is the accounting of topological changes suffered by the interface between phases wherein break up and/or merge takes place. The underlying physics of topological changes require the incorporation of space-time subscales not at reach at the moment. Therefore we use heuristic geometrical arguments to reconnect phases in space. This heuristic approach provides new insight in various applications and it is extensible to include subscale physics and chemistry in the future. We demonstrate the method on applications such as simulating freezing, melting, dissolution, and precipitation. The later examples also include the coupling of the phase transition solution with the Navier-Stokes equations for the effect of flow convection.
Determination of mineral dissolution regimes using flow-through time-resolved analysis (FT-TRA) and numerical simulation
Flow-through time resolved analysis (FT-TRA) involves subjecting small mineral samples (< 10 mg) inserted in a miniature flow-through cell (50 μL) to controlled flows of eluent analyzed on-line by ICP-MS. In this study, FT-TRA is used to empirically determine the dissolution regimes for the two well-studied minerals forsterite and calcite, representing minerals with relatively slow and fast dissolution kinetics. A proportional increase in steady-state effluent [Mg, Si] concentrations with increasing flow-through cell eluent residence times confirms a dominantly surface-controlled dissolution regime for a powdered forsterite sample at pH 2.3, implying that transport limitations are negligible. In contrast, the relationship between flow rates and dissolution rates for single grain calcite samples at pH 2.3-4 reveals that transport limitations affect the rate of calcite dissolution. In order to provide a quantitative and process-based assessment of the effect of diffusive transport limitations, simulations of the calcite experiments were performed with a high resolution, pore-scale model that considers the geometry of the calcite grain and the FT-TRA flow-through reactor. The pore-scale model reproduces the observed effluent [Ca] concentrations for all experimental conditions using a single set of surface kinetic parameters, by accounting for the formation of a diffusive boundary layer (DBL) that varies in thickness as a function of flow rates. These results demonstrate that combining FT-TRA with pore-scale modeling makes it possible to obtain unprecedented insights not achievable by either method separately, including quantification of DBL thicknesses and the determination of transport controls as a function of pH, flow velocity and residence times.
Numerical simulation for the design of induction heating based radio frequency reactor for ethylene production
Ethylene is a vital petrochemical compound produced in vast amounts yearly by manufacturers that have enough scale to overcome the inherent thermodynamic inefficiencies of the process. In order to address the inefficiencies that prevent smaller scale or intermittent production ethylene, investigation of new production methods are required. In this work, we investigate the use of a radio frequency (RF) based reactor system that generates heat internally as opposed to applying heat externally via steam or direct combustion of fossil fuels. In order to guide the design of an electromagnetic based reactor system, we have created a macroscale model capable of capturing heat generation at the susceptors from a produced electromagnetic field and subsequent chemical reactions. Several susceptor and induction coil designs were investigated to better understand the performance of the system.
Direct numerical simulations of NOx effect on multistage autoignition of DME/air mixture in the negative temperature coefficient regime for stratified HCCI engine conditions
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Direct numerical simulations of HCCI/SACI with ethanol
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Impact of multi-component diffusion in turbulent combustion using direct numerical simulations
This study presents the results of DNS of a partially premixed turbulent syngas/air flame at atmospheric pressure. The objective was to assess the importance and possible effects of molecular transport on flame behavior and structure. To this purpose DNS were performed at with two proprietary DNS codes and with three different molecular diffusion transport models: fully multi-component, mixture averaged, and imposing the Lewis number of all species to be unity.
Direct numerical simulation of a temporally evolving air/n-dodecane jet at low-temperature diesel-relevant conditions
Abstract not provided.
Edge flame speed analysis of a swirl-stabilized spray flame using sustainable aviation fuels: A direct numerical simulation study
Not Available
Numerical simulation of Water-alternating-gas Process for Optimizing EOR and Carbon Storage
Carbon dioxide (CO 2 ) generated by fossil fuel combustion can have serious consequences for humans and environments. Carbon capture, utilization and geological storage (CCUS) is a key approach to reduce the emissions of the anthropogenic CO 2 into the atmosphere. Of those, sequestering the CO 2 into depleted hydrocarbon reservoirs with associated enhanced oil recovery is the most achievable approach under current economic constraints since it increases recovery of existing oil reserves, and bridges the gap between nonprofit geological CO 2 sequestration and profit CO 2 -EOR. The Upper Devonian fluvial sandstone reservoir in Jacksonburg-Stringtown oil field in West Virginia, which has produced over 22 million barrels of oil since 1895, is an ideal candidate for CO 2 sequestration coupled with EOR. This research illustrates an example of CCUS, in which CO 2 is sequestered into underground meanwhile enhanced oil recovery from the depleted hydrocarbon reservoir by water alternating gas (WAG) strategy. Three CO 2 storage mechanisms including structural/stratigraphic trapping, dissolution trapping, and residual trapping are considered. A 3D geological model is constructed based on existing geological data from the Jacksonburg-Stringtown oil field. A 3D composition fluid model with 0.4 pore volume (PV) of water injection before WAG process is considered as a benchmark of this study. Several factors including WAG cycle period, injection time ratio, CO 2 injection rate are evaluated. After injection wells are completely shut-in, stored CO 2 is monitored for additional 200 years as a function of various storage mechanisms. The result shows that over 6 years of WAG injection, total 12 - 40 MMlb-mol CO 2 is sequestrated and oil recovery factor can achieve 28%. As a conclusion, this research constructs a basic workflow for CO 2 storage coupled with CO 2 -EOR which can be applied to other super-mature oil fields.